STUDIES & PUBLICATIONS

There have been over 80 publications on LAMP Technology including proof of concept evaluations of LAMP-based vaccines to treat specific cancers, infectious diseases, and autoimmune disorders. Presented here are the papers that ITI’s scientific team believes best represent the versatility and immunogenicity of the LAMP platform.

BACKGROUND: Previous studies demonstrated that allergen gene vaccination induced TH1-skewed responses and inhibited IgE production. This study evaluated and characterized the immune responses induced by three DNA constructs encoding different forms of Der p 2 for safe and efficacious vaccination against mite allergy. METHODS: Mice were immunized intramuscularly with DNA constructs encoding a major mite allergen, Der p 2, without a signal peptide (p2), with a signal peptide (p52), and with a signal peptide plus lysosomal-targeting sequence (p52-LA), respectively, followed by TH2-skewed protein challenge. Antibody and T-cell cytokine responses were assessed by ELISA. Primed dendritic cells (DCs) were adoptively transferred to naïve mice and humoral responses were examined after protein challenge. The circulating Der p 2 protein was detected by sandwich ELISA. RESULTS: Mice immunized with p52-LA showed strong and clear-cut TH1-type response, as evident by high IFN-gamma production and elevated levels of Der p 2-specific IgG2a production whereas construct p2 induced only moderate levels of TH1 response. In contrast, mice immunized with construct p52 showed a mixed TH1/TH2 phenotype and produced substantial circulating Der p 2 protein. Mice adoptively transferred with DCs primed by p52 construct, but not by the p2 or p52-LA constructs, were sensitized to produce high levels of Der p 2-specific IgE. CONCLUSIONS: Immunization with DNA construct encoding a signal peptide could potentially prime TH2-skewed responses and IgE production. The additional inclusion of lysosomal-targeting sequences to such construct could improve the safety and efficacy of DNA vaccination against allergy.

Ag processing is a critical step in defining the repertoire of epitope-specific immune responses. In the present study, HIV-1 p55Gag Ag was synthesized as a DNA plasmid with either lysosomal-associated membrane protein-1 (LAMP/gag) or human dendritic cell-LAMP (DC-LAMP/gag) and used to immunize mice. Analysis of the cellular trafficking of these two chimeras demonstrated that both molecules colocalized with MHC class II molecules but differed in their overall trafficking to endosomal/lysosomal compartments. Following DNA immunization, both chimeras elicited potent Gag-specific T and B cell immune responses in mice but differ markedly in their IL-4 and IgG1/IgG2a responses. The DC-LAMP chimera induced a stronger Th type 1 response. ELISPOT analysis of T cell responses to 122 individual peptides encompassing the entire p55gag sequence (15-aa peptides overlapping by 11 residues) showed that DNA immunization with native gag, LAMP/gag, or DC-LAMP/gag induced responses to identical immunodominant CD4+ and CD8+ peptides. However, LAMP/gag and DC-LAMP/gag plasmids also elicited significant responses to 23 additional cryptic epitopes that were not recognized after immunization with native gag DNA. The three plasmids induced T cell responses to a total of 39 distinct peptide sequences, 13 of which were induced by all three DNA constructs. Individually, DC-LAMP/gag elicited the most diverse response, with a specific T cell response against 35 peptides. In addition, immunization with LAMP/gag and DC-LAMP/gag chimeras also promoted Ab secretion to an increased number of epitopes. These data indicate that LAMP-1 and DC-LAMP Ag chimeras follow different trafficking pathways, induce distinct modulatory immune responses, and are able to present cryptic epitopes.

Infants born to HIV-infected mothers are at high risk of becoming infected during gestation or the breastfeeding period. A search is thus warranted for vaccine formulations that will prevent mother-to-child HIV transmission. The LAMP/gag DNA chimeric vaccine encodes the HIV-1 p55gag fused to the lysosome-associated membrane protein-1 (LAMP-1) and has been shown to enhance anti-Gag antibody (Ab) and cellular immune responses in adult and neonatal mice; such a vaccine represents a new concept in antigen presentation. In this study, we evaluated the effect of LAMP/gag DNA immunization on neonates either before conception or during pregnancy. LAMP/gag immunization of BALB/c mice before conception by the intradermal route led to the transfer of anti-Gag IgG1 Ab through the placenta and via breastfeeding. Furthermore, there were an increased percentage of CD4+CD25+Foxp3+T cells in the spleens of neonates. When offspring were immunized with LAMP/gag DNA, the anti-Gag Ab response and the Gag-specific IFN-?-secreting cells were decreased. Inhibition of anti-Gag Ab production and cellular responses were not observed six months after immunization, indicating that maternal immunization did not interfere with the long-lasting memory response in offspring. Injection of purified IgG in conjunction with LAMP/gag DNA immunization decreased humoral and cytotoxic T-cell responses. LAMP/gag DNA immunization by intradermal injection prior to conception promoted the transfer of Ab, leading to a diminished response to Gag without interfering with the development of anti-Gag T- and B-cell memory. Finally, we assessed responses after one intravenous injection of LAMP/gag DNA during the last five days of pregnancy. The intravenous injection led to in utero immunization. In conclusion, DNA vaccine enconding LAMP-1 with Gag and other HIV-1 antigens should be considered in the development of a protective vaccine for the maternal/fetal and newborn periods.

Previous studies of HIV-1 p55Gag immunization of mice have demonstrated the usefulness of targeting antigens to the cellular compartment containing the major histocompatibility complex type II (MHC II) complex molecules by use of a DNA antigen formulation encoding Gag as a chimera with the mouse lysosome-associated membrane protein (mLAMP/gag). In the present study, we have analyzed the magnitude and breadth of Gag-specific T-lymphocyte and antibody responses elicited in Rhesus macaques after immunization with DNA encoding a human LAMP/gag (hLAMP/gag) chimera. ELISPOT analyses indicated that the average Gag-specific IFN-gamma response elicited by the hLAMP/gag chimera was detectable after only two or three naked DNA immunizations in all five immunized macaques and reached an average of 1000 spot-forming cells (SFC)/10(6) PBMCs. High IFN-gamma ELISPOT responses were detected in CD8(+)-depleted cells, indicating that CD4(+) T-cells play a major role in these responses. The T-cell responses of four of the macaques were also tested by use of ELISPOT to 12 overlapping 15-amino acids (aa) peptide pools containing ten peptides each, encompassing the complete Gag protein sequence. The two Mamu 08 immunized macaques responded to eight and twelve of the pools, the Mamu B01 to six, and the other macaque to five pools indicating that the hLAMP/gag DNA antigen formulation elicits a broad T-cell response against Gag. Additionally, there was a strong HIV-1-specific IgG response. The IgG antibody titers increased after each DNA injection, indicating a strong amnestic B-cell response, and were highly elevated in all the macaques after three immunizations. Moreover, the serum of each macaque recognized 13 of the 49 peptides of a 20-aa peptide library covering the complete Gag amino acid sequence. In addition, HIV-1-specific IgA antibodies were present in the plasma and external secretions, including nasal washes. These data support the findings of increased immunogenicity of genetic vaccines encoded as LAMP chimeras, including the response to DNA vaccines by non-human primates.

Murine studies have shown that immunologic targeting of the tumor vasculature, a key element of the tumor stroma, can lead to protective immunity in the absence of significant pathology. In the current study, we expand the scope of stroma-targeted immunotherapy to antigens expressed in tumor-associated fibroblasts, the predominant component of the stroma in most types of cancer. Mice were immunized against fibroblast activation protein (FAP), a product up-regulated in tumor-associated fibroblasts, using dendritic cells transfected with FAP mRNA. Using melanoma, carcinoma, and lymphoma models, we show that tumor growth was inhibited in tumor-bearing mice vaccinated against FAP and that the magnitude of the antitumor response was comparable to that of vaccination against tumor cell-expressed antigens. Both s.c. implanted tumors and lung metastases were susceptible to anti-FAP immunotherapy. The antitumor response could be further enhanced by augmenting the CD4+ T-cell arm of the anti-FAP immune response, achieved by using a lysosomal targeting sequence to redirect the translated FAP product into the class II presentation pathway, or by covaccination against FAP and a tumor cell-expressed antigen, tyrosinase-related protein 2. No morbidity or mortality was associated with anti-FAP vaccination except for a small delay in wound healing. The study suggests that FAP, a product which is preferentially expressed in tumor-associated fibroblasts, could function as a tumor rejection antigen in a broad range of cancers.

An optimal anticancer vaccine probably requires the cooperation of both CD4(+) Th cells and CD8(+) CTLs. A promising tool in cancer immunotherapy is, therefore, the genetic modification of dendritic cells (DCs) by introducing the coding region of a tumor Ag, of which the antigenic peptides will be presented in both HLA class I and class II molecules. This can be achieved by linking the tumor Ag to the HLA class II-targeting sequence of an endosomal or lysosomal protein. In this study we compared the efficiency of the targeting signals of invariant chain, lysosome-associated membrane protein-1 (LAMP1) and DC-LAMP. Human DCs were electroporated before or after maturation with mRNA encoding unmodified enhanced green fluorescent protein (eGFP) or eGFP linked to various targeting signals. The lysosomal degradation inhibitor chloroquine was added, and eGFP expression was evaluated at different time points after electroporation. DCs were also electroporated with unmodified MAGE-A3 or MAGE-A3 linked to the targeting signals, and the presentation of MAGE-A3-derived epitopes in the context of HLA class I and class II molecules was investigated. Our data suggest that proteins linked to the different targeting signals are targeted to the lysosomes and are indeed presented in the context of HLA class I and class II molecules, but with different efficiencies. Proteins linked to the LAMP1 or DC-LAMP signal are more efficiently presented than proteins linked to the invariant chain-targeting signal. Furthermore, DCs electroporated after maturation are more efficient in Ag presentation than DCs electroporated before maturation.

A genetic vaccine for West Nile virus (WN) has been synthesized with the WN premembrane-envelope (WN preM-E) gene sequences encoded as a chimera with the transmembrane and carboxyl terminal domains of the lysosome-associated membrane protein (LAMP). The LAMP sequences are used to direct the antigen protein to the major histocompatibility class II (MHC II) vesicular compartment of transfected professional antigen-presenting cells (APCs). Vaccine constructs encoding the native WN preM-E and WN preM-E/LAMP chimera were synthesized in pVAX1 and pITR plasmid backbones. Extracts of human fibroblast 293 and monkey kidney COS-7 cells transfected with the WN preM-E/LAMP chimera constructs contained much greater amounts of E than did the cells transfected with constructs encoding the native WN preM-E. This difference in the concentration of native E and the E/LAMP chimera in transfected cells is attributed to the secretion of native E. The amount of preM protein in cell extracts, in contrast to the E protein, and the levels of DNA and RNA transcripts, did not differ between WN preM-E- and WN preM-E/LAMP-transfected cells. Additionally, confocal and immunoelectron microscopic analyses of transfected B cells showed localization of the WN preM-E/LAMP chimera in vesicular compartments containing endogenous LAMP, MHC II, and H2-M, whereas native viral preM-E lacking the LAMP sequences was distributed within the cellular vesicular network with little LAMP or MHC II association. Mice immunized with a DNA construct expressing the WN preM-E/LAMP antigen induced significant antibody and long-term neutralization titers in contrast to the minimal and short-lived neutralization titer of mice vaccinated with a plasmid expressing the untargeted antigen. These results underscore the utility of LAMP targeting of the WN envelope to the MHC II compartments in the design of a genetic WN vaccine.

The effectiveness of the dendritic cell (DC) vaccination protocols that are currently in use could be improved by providing the DCs with a more potent maturation signal. We therefore investigated whether the T-cell stimulatory capacity of human monocyte-derived DCs could be increased by co-electroporation with different combinations of CD40L, CD70, and constitutively active toll-like receptor 4 (caTLR4) encoding mRNA. We show that immature DCs electroporated with CD40L and/or caTLR4 mRNA, but not those electroporated with CD70 mRNA, acquire a mature phenotype along with an enhanced secretion of several cytokines/chemokines. Moreover, these DCs are very potent in inducing naive CD4(+) T cells to differentiate into interferon-gamma (IFN-gamma)-secreting type 1 T helper (Th1) cells. Further, we assessed the capacity of the electroporated DCs to activate naive HLA-A2-restricted MelanA-specific CD8(+) T cells without the addition of any exogenous cytokines. When all three molecules were combined, a >500-fold increase in MelanA-specific CD8(+) T cells was observed when compared with immature DCs, and a >200-fold increase when compared with cytokine cocktail-matured DCs. In correlation, we found a marked increase in cytolytic and IFN-gamma/tumor necrosis factor-alpha (TNF-alpha) secreting CD8(+) T cells. Our data indicate that immature DCs genetically modified to express stimulating molecules can induce tumor antigen-specific T cells in vitro and could prove to be a significant improvement over DCs matured with the methods currently in use.

Telomerase reverse transcriptase (hTERT) represents an attractive target for cancer immunotherapy because hTERT is reactivated in most human tumors. A clinical trial was initiated in which hTERT mRNA-transfected dendritic cells (DC) were administered to 20 patients with metastatic prostate cancer. Nine of these subjects received DC transfected with mRNA encoding a chimeric lysosome-associated membrane protein-1 (LAMP) hTERT protein, allowing for concomitant induction of hTERT-specific CD8+ and CD4+ T cell responses. Treatment was well tolerated. Intense infiltrates of hTERT-specific T cells were noted at intradermal injection sites after repeated vaccination. In 19 of 20 subjects, expansion of hTERT-specific CD8+ T cells was measured in the peripheral blood of study subjects, with 0.9-1.8% of CD8+ T cells exhibiting Ag specificity. Patients immunized with the chimeric LAMP hTERT vaccine developed significantly higher frequencies of hTERT-specific CD4+ T cells than subjects receiving DC transfected with the unmodified hTERT template. Moreover, CTL-mediated killing of hTERT targets was enhanced in the LAMP hTERT group, suggesting that an improved CD4+ response could augment a CTL response. Vaccination was further associated with a reduction of prostate-specific Ag velocity and molecular clearance of circulating micrometastases. Our findings provide a rationale for further development of hTERT-transfected DC vaccines in the treatment of prostate and other cancers.

Presentation of antigenic peptides by MHC class II molecules to CD4+ T cells is critical to the generation of antitumor immunity. In an attempt to enhance MHC class II antigen processing, we linked the sorting signals of the lysosome-associated membrane protein (LAMP-1) to the cytoplasmic/nuclear human papilloma virus (HPV-16) E7 antigen, creating a chimera (Sig/E7/LAMP-1). Previously, we found that expression of this chimera in vitro and in vivo with a recombinant vaccinia vector targeted E7 to endosomal and lysosomal compartments and enhanced MHC class II presentation to CD4+ T cells compared to vaccinia expressing wild-type E7. In the current study, we tested these recombinant vaccinia for in vivo protection against an E7+ tumor, TC-1, which was derived from primary epithelial cells of C57BL/6 mice cotransformed with HPV-16 E6 and E7 and c-Ha-ras oncogenes. All mice vaccinated with 1 x 10(7) plaque-forming units of wild-type E7-vaccinia showed progressive tumor growth when challenged with a tumorigenic dose of TC-1 tumor cells; in contrast, 80% of mice vaccinated with the chimeric Sig/E7/LAMP1 vaccinia remained tumor free 3 months after tumor injection. Furthermore, treatment with the Sig/E7/LAMP-1 vaccinia vaccine cured mice with small established TC-1 tumors, whereas the wild-type E7-vaccinia showed no effect on this established tumor burden. These findings point out the therapeutic limitations of recombinant vaccinia expressing unmodified tumor antigens. Further, they demonstrate that modifications that reroute a cytosolic tumor antigen to the endosomal/lysosomal compartment can profoundly improve the in vivo therapeutic potency of recombinant vaccines.

A potentially powerful strategy for therapeutic HIV vaccination is the use of DC transfected with mRNA encoding autologous viral Ag, as epitopes presented by transfected DC would exactly reflect those expressed by infected cells in the individual. Using human and rhesus macaque monocyte-derived DC, we show that nucleofection is a superior method for mRNA transfection, resulting in high-level protein expression and DC maturation. DC transfected with SIV gag isolated from an infected monkey stimulated robust Ag-specific recall T cell responses of similar magnitude to those induced by peptide-pulsed PBMC that were predominantly CD8+ T cell mediated. Enhanced CD4+ T cell responses were stimulated when Gag was redirected into the lysosomal pathway via the targeting signal derived from lysosome-associated membrane protein-1 (LAMP-1). Rhesus DC transfected with lysosome-targeted gag encoding an escape mutation in an immunodominant CTL epitope stimulated CD4+ and CD8+ T cell responses of almost equivalent magnitude directed towards undefined epitopes outside of the mutated region. Finally, gag-transfected DC from SIV-infected monkeys stimulated significant Ag-specific recall T cell responses in an entirely autologous system. These findings demonstrate that mRNA-transfected DC expressing SIV Ag derived from infected monkeys stimulate broad and relevant T cell responses, supporting this approach for therapeutic HIV vaccine development.

Dendritic cells (DC) generated from the peripheral blood mononuclear cells of healthy individuals or from cancer patients transfected with carcinoembryonic antigen (CEA) mRNA stimulate a potent CD8+ cytotoxic T lymphocyte (CTL) response in vitro. DCs are effectively sensitized with RNA in the absence of reagents commonly used to facilitate mammalian cell transfection. RNA encoding a chimeric CEA/LAMP-1 lysosomal targeting signal enhances the induction of CEA-specific CD4+ T cells, providing a strategy to induce T-help that may be necessary to generate and/or maintain an optimal CD8+ CTL response in vivo. CEA RNA-transfected DCs also serve as effective targets in cytotoxicity assays, thus providing a general method for inducing, as well as measuring, CEA-specific CTL responses across a broad spectrum of HLA haplotypes.

Transfection with synthetic mRNA is a safe and efficient method of delivering antigens to dendritic cells for immunotherapy. Targeting antigens to the lysosome can sometimes enhance the CD4+ T-cell response. We transfected antigen-presenting cells (APCs) with mRNA encoding Gag-p24 and cytoplasmic, lysosomal, and secreted forms of Nef. Antigen-specific cytotoxic T cells were able to lyse the majority of transfected targets, indicating that transfection was efficient. Transfection of APCs with a Nef construct bearing lysosomal targeting signals produced rapid and prolonged antigen presentation to CD4+ and CD8+ T cells. Polyclonal CD4+ and CD8+ T-cell lines recognizing multiple distinct epitopes were expanded by coculture of transfected dendritic cells with peripheral blood mononuclear cells from viremic and aviremic HIV-infected subjects. Importantly, lysosome-targeted antigen drove a significantly greater expansion of Nef-specific CD4+ T cells than cytoplasmic antigen. The frequency of recognition of CD8 but not CD4 epitopes by mRNA-expanded T cells was inversely proportional to sequence entropy and was similar to ex vivo responses from a large chronic cohort. Thus human dendritic cells transfected with mRNA encoding lysosome-targeted HIV antigen can expand a broad, polyclonal repertoire of antiviral T cells, offering a promising approach to HIV immunotherapy.

DNA immunization is a new approach for cancer immune therapy. In this study, we constructed human papillomavirus (HPV) 16 E7 expression vector cassettes and then compared the abilities of these constructs to induce antitumour protection. Lysosome-targeted E7 antigens, and to a lesser degree signal sequence-conjugated and transmembrane region sequence-conjugated E7 antigens in a DNA form, displayed tumour protection significantly higher than wild-type E7 antigens. This enhanced tumour protection was mediated by CD8+ cytotoxic T lymphocytes (CTL), as determined by in vivo T-cell depletion and in vitro interferon-gamma (IFN-gamma) production. Subsequent co-injection with interleukin-12-expressing cDNA showed insignificantly enhanced antitumour protection. However, E7 codon optimization plus lysosomal targeting resulted in a dramatic enhancement in antitumour protection both prophylactically and therapeutically through augmentation of the E7-specific CTL population, compared to either one of them alone. However, wild-type or codonoptimized E7 antigens without intracellular targeting displayed no protection against tumour challenge. Thus, these data suggest that antigen codon optimization plus lysosomal targeting strategy could be important in crafting more efficacious E7 DNA vaccines for tumour protection.

Vaccines capable of inducing mucosal immunity in early postnatal life until adulthood, protecting early sexual initiation, should be considered as strategies to vaccination against HIV. The HIV-1 GAG protein as a chimera with the lysosome-associated membrane protein (LAMP/gag), encoded by a DNA vaccine, is targeted to the endosomal/lysosomal compartment that contains class II MHC molecules and has been shown to be immunogenic in adult mice. Assuming that one such strategy could help to overcome the immunological immaturity in the early postnatal period, we have evaluated the systemic and mucosal immunogenicity of LAMP/gag immunization in neonatal mice. Intranasal immunization with LAMP/gag vaccine induced higher levels of sIgA and IgG anti-GAG antibodies in intestinal washes than did the gag vaccine. The combination of ID injections and the IN protocol with the chimeric vaccine promoted the increase of Ab levels in sera. Both vaccines induced splenic IFN-?- secreting cells against GAG peptide pools, as well as in vivo cytotoxic T lymphocyte (CTL) function, and increased the percentage of CD8+ T cells to the immunodominant class I peptide in gut and spleen. However, only the chimeric vaccine was able to enhance Th1/Th2 cytokine secretion in response to class II GAG peptide and to enhance IL-4-secreting cells against GAG peptides and p24 protein stimuli. Long-lasting humoral and cellular responses were detected until adult age, following neonatal immunization with the chimeric vaccine. The LAMP/gag vaccination was able to induce potent GAG-specific T and B cell immune responses in early life which are essential to elicit sustained and long-lasting mucosal and systemic humoral response.

The worldwide incidence of rabies and the inability of currently used vaccination strategies to provide highly potent and cost-effective therapy indicate the need for an improved rabies vaccine. Thus, DNA vaccine based on lysosome-targeted glycoprotein of the rabies virus was evaluated in BALB/c mice. It imparted partial protection (60%) against challenge with 20 LD(50) of the challenge virus standard (CVS) strain of rabies virus. To improve the outcome of vaccination, to ultimately enhance the immune response, we investigated different routes for DNA vaccine delivery, varied doses of DNA, and the influence of adjuvant supplementation. The highest immune response pertaining to IgG antibody titer, with a predominantly IgG1/IgG2a subclass distribution, effective cellular immunity, and a high level of rabies virus neutralizing antibodies (RVNAs) was attained by the optimized DNA vaccine formulation comprising intramuscular administration of 100 microg of DNA vaccine supplemented with Emulsigen-D. In preexposure prophylaxis, a 3-dose regimen of this formulation generated a high RVNA titer (32 IU/ml) and conferred complete protection against challenge with 20 LD(50) of CVS. For postexposure efficacy analysis, rabies was experimentally induced with 50 LD(50) of CVS. Subsequent therapy with 5 doses of the formulation completely prevented rabies in BALB/c mice, which maintained protective RVNA titers of 4 IU/ml. The World Health Organization recommended rabies protective titer threshold is 0.5 IU/ml. Thus, this optimized DNA vaccine formulation provides an avenue for preventing and controlling rabies.

The presentation of antigenic peptides by major histocompatibility complex (MHC) class II molecules to CD4+ T cells is critical to the function of the immune system. In this study, we have utilized the sorting signal of the lysosomal-associated membrane protein LAMP-1 to target a model antigen, human papillomavirus 16 E7 (HPV-16 E7), into the endosomal and lysosomal compartments. The LAMP-1 sorting signal reroutes the antigen into the MHC class II processing pathway, resulting in enhanced presentation to CD4+ cells in vitro. In vivo immunization experiments in mice demonstrated that vaccinia containing the chimeric E7/LAMP-1 gene generated greater E7-specific lymphoproliferative activity, antibody titers, and cytotoxic T-lymphocyte activities than vaccinia containing the wild-type HPV-16 E7 gene. These results suggest that specific targeting of an antigen to the endosomal and lysosomal compartments enhances MHC class II presentation and vaccine potency.

Several genetic vaccines encoding antigen chimeras containing the lysosome-associated membrane protein (LAMP) translocon, transmembrane, and cytoplasmic domain sequences have elicited strong mouse antigen-specific immune responses. The increased immune response is attributed to trafficking of the antigen chimera to the major histocompatibility class II (MHC II) compartment where LAMP is colocalized with MHC II. In this report, we describe a new form of an HIV-1 p55gag DNA vaccine, with the gag sequence incorporated into the complete LAMP cDNA sequence. Gag encoded with the translocon, transmembrane and cytoplasmic lysosomal membrane targeting sequences of LAMP, without the luminal domain, was poorly expressed, did not traffic to lysosomes or MHC II compartments of transfected cells, and elicited a limited immune response from DNA immunized mice. In contrast, addition of the LAMP luminal domain sequence to the construct resulted in a high level of expression of the LAMP/Gag protein chimera in transfected cells that was further increased by including the inverted terminal repeat sequences of the adeno-associated virus to the plasmid vector. This LAMP/Gag chimera with the complete LAMP protein colocalized with endogenous MHC II of transfected cells and elicited strong cellular and humoral immune responses of immunized mice as compared with the response to DNA-encoding native Gag, with a 10-fold increase in CD4+ responses, a 4- to 5-fold increase in CD8+ T-cell responses, and antibody titers of >100,000. These results reveal novel roles of the LAMP luminal domain as a determinant of Gag protein expression, lysosomal trafficking, and possibly of the immune response to Gag.

Dendritic cells (DCs) transfected with mRNA encoding human telomerase reverse transcriptase (hTERT) have been shown to represent potent inducers of CTLs and antitumor immunity. However, it has become widely accepted that not only CTLs but also CD4(+) T helper cells are critical to the generation, as well as to the maintenance, of potent antitumor responses in vivo. In this study, we sought to determine whether human DCs transfected with mRNA encoding a chimeric hTERT/lysosome-associated membrane protein (LAMP-1) protein, carrying the endosomal/lysosomal sorting signal of the LAMP-1, are capable of stimulating concomitant hTERT-specific CD8(+) and CD4(+) T-cell responses in vitro. We show that processing of hTERT/LAMP-1 transcripts leads to enhanced stimulation of hTERT-specific CD4(+) T cells and does not negatively affect intracellular generation and subsequent presentation of MHC class I epitopes, hence, generating a CTL response. These findings provide a preclinical rationale of using DCs transfected with the chimeric hTERT/LAMP-1 RNA in vaccine trials to facilitate generation of antigen-specific CD4(+) T-cell responses that may be required to stimulate and maintain an optimal CD8(+) CTL response in vivo.

The lysosome-associated membrane proteins (LAMP), found in the outer membrane of lysosomes and also in a multilaminar compartment that contains major histocompatibility complex class II (MHC II) proteins, are directed to their localization by a cytoplasmic carboxyl-terminal sequence. Our studies of the immune response to LAMP-targeted proteins has led to the application of a HIV-1 gp160/LAMP chimeric gene as a novel means to enhance the MHC II presentation of gp160. Immunofluorescence microscopy confirmed that the gp160/LAMP protein had a cellular localization corresponding to that of lysosomes. Pulse-chase analysis confirmed that the rates of synthesis of gp160/LAMP and wild type gp160 were comparable and that both proteins were processed to gp120 at similar rates. However, the gp160/LAMP was degraded more rapidly than the wild type gp160. MHC II-mediated T cell proliferation assays performed with cloned human cell lines showed that gp160/LAMP stimulated greater responses than did the wild type gp160. Moreover, mice vaccinated with recombinant vaccinia expressing gp160/LAMP had greater gp160-specific lymphoproliferation responses and higher titers of anti-V3 loop antibodies than mice vaccinated with recombinant vaccinia expressing wild type gp160.

Antigen presentation by major histocompatibility complex type II (MHC II) molecules and activation of CD4+ helper T cells are critical for the generation of immunological memory. We previously described a DNA vaccine encoding human immunodeficiency virus-1 p55Gag as a chimera with the lysosome-associated membrane protein (LAMP/gag). The LAMP/gag chimera protein traffics to the MHC II compartment of transfected cells and elicits enhanced immune responses as compared to a DNA vaccine encoding native gag not targeted to the MHC II compartment. We have now investigated the long-term responses of immunized mice and show that the LAMP/gag DNA vaccine promotes long-lasting B cell- and CD4+ and CD8+ T-cell memory responses induced by DNA encoding non-targeted Gag decay rapidly and elicit very low or undetectable levels of gag DNA is sufficient to generate T-cell memory. Following this initial priming immunization with LAMP/gag DNA, booster immunizations with native gag DNA or the LAMP/gag chimera are equally efficient in eliciting B- and T-cell secondary responses, results in accordance with observations that secondary expansion of CD8+ cells in the boost phase does not require additional CD4+ help. These findings underscore the significance of targeting DNA-encoded vaccine antigens to the MHC II processing compartments for induction of long-term immunological memory.

The immunostimulatory capacity of dendritic cells is improved by co-electroporation with mRNA encoding CD40 ligand, constitutively active toll-like receptor 4, and CD70 (TriMix-DC). This pilot clinical trial evaluated the feasibility, safety, and immunogenicity of a therapeutic vaccination containing autologous TriMix-DC co-electroporated with mRNA encoding a human leukocyte antigen class II-targeting signal linked to 1 of 4 melanoma-associated antigens (MAGE-A3, MAGE-C2, tyrosinase, and gp100) in patients with advanced melanoma. Thirty-five American Joint Committee on Cancer stage III/IV melanoma patients received autologous TriMix-DC (4 administrations 2 weeks apart). Immune monitoring was performed by evaluating skin biopsies of delayed type IV hypersensitivity (DTH) reactions for presence of vaccinal antigen-specific DTH-infiltrating lymphocytes (DIL). Thereafter, patients could receive interferon-alpha-2b (IFN-a-2b) 5 MU subcutaneously 3 times weekly and additional TriMix-DC every 8 weeks. TriMix-DC-related adverse events comprised grade 2 local injection site reactions (all patients), and grade 2 fever and lethargy (2 patients). Vaccinal antigen-specific DIL were found in 0/6 patients tested at vaccine initiation and in 12/21 (57.1%) assessed after the fourth vaccine. A positive postvaccination DTH test correlated with IL-12p70 secretion capacity of TriMix-DC. No objective responses to TriMix-DC alone were seen according to RECIST. Twenty-nine patients received IFN-a-2b after the fourth vaccine without unexpected adverse events. During TriMix-DC/IFN-a-2b combination therapy, 1 partial response and 5 stable disease (disease control of >6 months with regression of metastases) were observed in 17 patients with evaluable disease at baseline. In conclusion, this study demonstrated that therapeutic vaccination with autologous TriMix-DC is feasible, safe, and immunogenic and can be combined with sequential IFN-a-2b.

Transmissible spongiform encephalopathies (TSEs) can be ameliorated by prion protein (PrP)-specific antibodies, but active immunization is complicated by immune tolerance to the normal cellular host protein (PrP(C)). Here, we show that DNA immunization of wild-type mice can break immune tolerance against the prion protein, resulting in the induction of PrP-specific antibody and T-cell responses. PrP immunogenicity was increased by fusion to the lysosomal targeting signal from LIMPII (lysosomal integral membrane protein type II). Although mice immunized with a PrP-LIMPII DNA vaccine showed a dramatic delay in the onset of early disease signs after intracerebral challenge, immunization against PrP also had some deleterious effects. These results clearly confirm the feasibility of using active immunization to protect against TSEs and, in the absence of effective treatments, indicate a suitable alternative for combating the spread of these diseases.

Intradermal administration of DNA vaccines, using a gene gun, represents an effective means of delivering DNA directly into professional antigen-presenting cells (APCs) in the skin and thus allows the application of strategies to modify the properties of APCs to enhance DNA vaccine potency. In the current study, we hypothesized that the potency of human papillomavirus (HPV) type 16 E7 DNA vaccines employing intracellular targeting strategies combined with a strategy to prolong the life of dendritic cells (DCs) could be further enhanced by the addition of a DNA vaccine capable of generating high numbers of pan-HLA-DR reactive epitope (PADRE)-specific CD4(+) T cells. We observed that the addition of PADRE DNA to E7 DNA vaccines employing intracellular targeting strategies with a strategy to prolong the life of DCs led to significant enhancement of E7-specific CD8(+) effector and memory T cells as well as significantly improved therapeutic effects against established E7-expressing tumors in tumor-challenged mice. Our data suggest that the potency of a DNA vaccine combining an intracellular targeting strategy as well as a strategy to prolong the life of DCs can be further enhanced by addition of DNA that is capable of generating high numbers of PADRE-specific CD4(+) T cells.

LAMP Publications by Topic:   HPV | HIV | Cancer | Dengue / West Nile | General LAMP Papers

Human papilloma virus E6 or E7

  • Chen CH, Ji H, Suh KW, Choti MA, Pardoll DM, Wu TC. 1999. Gene gun-mediated DNA vaccination induces antitumor immunity against human papillomavirus type 16 E7-expressing murine tumor metastases in the liver and lungs. Gene Ther 6(12):1972-81.
  • Chen CH, Suh KW, Ji H, Choti MA, Pardoll DM, Wu TC. 2000a. Antigen-specific immunotherapy for human papillomavirus 16 E7-expressing tumors grown in the liver. J Hepatol 33(1):91-8.
  • Chen CH, Wang TL, Hung CF, Pardoll DM, Wu TC. 2000b. Boosting with recombinant vaccinia increases HPV-16 E7-specific T cell precursor frequencies of HPV-16 E7-expressing DNA vaccines. Vaccine 18(19):2015-22.
  • Chen CH, Wang TL, Ji H, Hung CF, Pardoll DM, Cheng WF, Ling M, Wu TC. 2001. Recombinant DNA vaccines protect against tumors that are resistant to recombinant vaccinia vaccines containing the same gene. Gene Ther 8(2):128-38.
  • Ji H, Chang EY, Lin KY, Kurman RJ, Pardoll DM, Wu TC. 1998. Antigen-specific immunotherapy for murine lung metastatic tumors expressing human papillomavirus type 16 E7 oncoprotein. Int J Cancer 78(1):41-5.
  • Ji H, Wang TL, Chen CH, Pai SI, Hung CF, Lin KY, Kurman RJ, Pardoll DM, Wu TC. 1999. Targeting human papillomavirus type 16 E7 to the endosomal/lysosomal compartment enhances the antitumor immunity of DNA vaccines against murine human papillomavirus type 16 E7-expressing tumors. Hum Gene Ther 10(17):2727-40.
  • Kim JW, Hung C-F, Juang J, He L, Kim TW, Armstrong DK, Pai SI, Chen P-J, Lin C-T, Boyd DA and others. 2004. Comparison of HPV DNA vaccines employing intracellular targeting strategies. Gene Ther 11(12):1011-8.
  • Kim MS, Sin JI. 2005. Both antigen optimization and lysosomal targeting are required for enhanced anti-tumour protective immunity in a human papillomavirus E7-expressing animal tumour model. Immunology 116(2):255-66.
  • Kim TW, Hung C-F, Boyd D, Juang J, He L, Kim JW, Hardwick JM, Wu T-C. 2003. Enhancing DNA vaccine potency by combining a strategy to prolong dendritic cell life with intracellular targeting strategies. J Immunol 171(6):2970-6.
  • Kim TW, Lee J-H, He L, Boyd DAK, Hung C-F, Wu T-C. 2005. DNA vaccines employing intracellular targeting strategies and a strategy to prolong dendritic cell life generate a higher number of CD8+ memory T cells and better long-term antitumor effects compared with a DNA prime-vaccinia boost regimen. Hum Gene Ther 16(1):26-34.
  • Mackova J, Stasikova J, Kutinova L, Masin J, Hainz P, Simsova M, Gabriel P, Sebo P, Nemeckova S. 2006. Prime/boost immunotherapy of HPV16-induced tumors with E7 protein delivered by Bordetella adenylate cyclase and modified vaccinia virus Ankara. Cancer Immunol Immunother 55(1):39-46.
  • Smahel M, Pokorn? D, Mackov? J, Vlas?k J. 2004. Enhancement of immunogenicity of HPV16 E7 oncogene by fusion with E. coli beta-glucuronidase. J Gene Med 6(10):1092-101.
  • Smahel M, S?ma P, Ludv?kov? V, Marinov I, Pokorn? D, Vonka V. 2003. Immunisation with modified HPV16 E7 genes against mouse oncogenic TC-1 cell sublines with downregulated expression of MHC class I molecules. Vaccine 21(11-12):1125-36.
  • Smahel M, S?ma P, Ludv?kov? V, Vonka V. 2001. Modified HPV16 E7 Genes as DNA Vaccine against E7-Containing Oncogenic Cells. Virology 281(2):231-8.
  • Wu TC, Guarnieri FG, Staveley-O’Carroll KF, Viscidi RP, Levitsky HI, Hedrick L, Cho KR, August JT, Pardoll DM. 1995. Engineering an intracellular pathway for major histocompatibility complex class II presentation of antigens. Proc Natl Acad Sci U S A 92(25):11671-5.
  • Peng S, Trimble C, Ji H, He L, Tsai Y, Macaes B, Hung C, Wu T. 2005. Characterization of HPV-16 E6 DNA vaccines employing intracellular targeting and intercellular spreading strategies. J Biomed Sci:1-12.
  • Pokorn? D, Mackov? J, Duskov? M, Rittich S, Ludv?kov? V, Smahel M. 2005. Combined immunization with fusion genes of mutated E7 gene of human papillomavirus type 16 did not enhance antitumor effect. J Gene Med 7(6):696-707.
  • Rittich S, Duskova M, Mackova J, Pokorna D, Jinoch P, Smahel M. 2005. Combined immunization with DNA and transduced tumor cells expressing mouse GM-CSF or IL-2. Oncol Rep 13(2):311-7.
  • Cheng WF, Hung CF, Hsu KF, Chai CY, He L, Ling M, Slater LA, Roden RB, Wu TC. 2001. Enhancement of sindbis virus self-replicating RNA vaccine potency by targeting antigen to endosomal/lysosomal compartments. Hum Gene Ther 12(3):235-52.
  • Lin, K-Y, Guarnieri, F. G., Staveley-O’Carroll, K. F., Levitsky, H. I., August, J. T., Pardoll, D. M., and Wu, T-C., Treatment of Established Tumors with a Novel Vaccine that Enhances Major Histocompatibility Class II Presentation of Tumor Antigen, Cancer Research 56: 21-26 (1996).

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Human immunodeficiency virus

  • Rowell JF, Ruff AL, Guarnieri FG, Staveley-O’Carroll K, Lin X, Tang J, August JT, Siliciano RF. 1995. Lysosome-associated membrane protein-1-mediated targeting of the HIV-1 envelope protein to an endosomal/lysosomal compartment enhances its presentation to MHC class II-restricted T cells. J Immunol 155(4):1818-28.
  • Ruff AL, Guarnieri FG, Staveley-O’Carroll K, Siliciano RF, August JT. 1997. The enhanced immune response to the HIV gp160/LAMP chimeric gene product targeted to the lysosome membrane protein trafficking pathway. J Biol Chem 272(13):8671-8.
  • Chikhlikar P, Barros de Arruda L, Agrawal S, Byrne B, Guggino W, August JT, Marques ETA. 2004. Inverted terminal repeat sequences of adeno-associated virus enhance the antibody and CD8(+) responses to a HIV-1 p55Gag/LAMP DNA vaccine chimera. Virology 323(2):220-32.
  • de Arruda LB, Chikhlikar PR, August JT, Marques ETA. 2004. DNA vaccine encoding human immunodeficiency virus-1 Gag, targeted to the major histocompatibility complex II compartment by lysosomal-associated membrane protein, elicits enhanced long-term memory response. Immunology 112(1):126-33.
  • Kavanagh DG, Kaufmann DE, Sunderji S, Frahm N, Le Gall S, Boczkowski D, Rosenberg ES, Stone DR, Johnston MN, Wagner BS and others. 2006. Expansion of HIV-specific CD4+ and CD8+ T cells by dendritic cells transfected with mRNA encoding cytoplasm- or lysosome-targeted Nef. Blood 107(5):1963-9.
  • Marques ETA, Chikhlikar P, de Arruda LB, Leao IC, Lu Y, Wong J, Chen J-S, Byrne B, August JT. 2003. HIV-1 p55Gag encoded in the lysosome-associated membrane protein-1 as a DNA plasmid vaccine chimera is highly expressed, traffics to the major histocompatibility class II compartment, and elicits enhanced immune responses. J Biol Chem 278(39):37926-36.
  • Qiu, J.T, Song R, Dettenhofer M, Tian C, August T, Felber BK, Pavlakis GN, Yu XF., Evaluation of novel human immunodeficiency virus type 1 Gag DNA vaccines for protein expression in mammalian cells and induction of immune responses. J Virol, 73, 9145-52(1999)

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Cancer antigens

  • Wang S, Bartido S, Yang G, Qin J, Moroi Y, Panageas KS, Lewis JJ, Houghton AN. 1999. A role for a melanosome transport signal in accessing the MHC class II presentation pathway and in eliciting CD4+ T cell responses. J Immunol 163(11):5820-6.
  • Bonehill A, Heirman C, Tuyaerts S, Michiels A, Breckpot K, Brasseur F, Zhang Y, Van Der Bruggen P, Thielemans K. 2004. Messenger RNA-electroporated dendritic cells presenting MAGE-A3 simultaneously in HLA class I and class II molecules. J Immunol 172(11):6649-57.
  • Brinster C, Muguet S, Lone YC, Boucreux D, Renard N, Fournillier A, Lemonnier F, Inchausp? G. 2001. Different hepatitis C virus nonstructural protein 3 (Ns3)-DNA-expressing vaccines induce in HLA-A2.1 transgenic mice stable cytotoxic T lymphocytes that target one major epitope. Hepatology 34(6):1206-17.
  • Lee J, Fassnacht M, Nair S, Boczkowski D, Gilboa E. 2005. Tumor immunotherapy targeting fibroblast activation protein, a product expressed in tumor-associated fibroblasts. Cancer Res 65(23):11156-63.
  • Lepage S, Lapointe R. 2006. Melanosomal targeting sequences from gp100 are essential for MHC class II-restricted endogenous epitope presentation and mobilization to endosomal compartments. Cancer Res 66(4):2423-32.
  • Nair SK, Boczkowski D, Morse M, Cumming RI, Lyerly HK, Gilboa E. 1998. Induction of primary carcinoembryonic antigen (CEA)-specific cytotoxic T lymphocytes in vitro using human dendritic cells transfected with RNA. Nat Biotechnol 16(4):364-9.
  • Su Z, Dannull J, Yang BK, Dahm P, Coleman D, Yancey D, Sichi S, Niedzwiecki D, Boczkowski D, Gilboa E and others. 2005. Telomerase mRNA-transfected dendritic cells stimulate antigen-specific CD8+ and CD4+ T cell responses in patients with metastatic prostate cancer. J Immunol 174(6):3798-807.
  • Su Z, Vieweg J, Weizer AZ, Dahm P, Yancey D, Turaga V, Higgins J, Boczkowski D, Gilboa E, Dannull J. 2002. Enhanced induction of telomerase-specific CD4(+) T cells using dendritic cells transfected with RNA encoding a chimeric gene product. Cancer Res 62(17):5041-8.

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West Nile virus

  • Anwar A, Chandrasekaran A, Ng ML, Marques E, August JT. 2005. West Nile premembrane-envelope genetic vaccine encoded as a chimera containing the transmembrane and cytoplasmic domains of a lysosome-associated membrane protein: increased cellular concentration of the transgene product, targeting to the MHC II compartment and enhanced neutralizing antibody response. Virology 332(1):66-77.

Dengue Virus

  • Lu Y, Raviprakash K, Leao IC, Chikhlikar PR, Ewing D, Anwar A, Chougnet C, Murphy G, Hayes CG, August TJ and others. 2003. Dengue 2 PreM-E/LAMP chimera targeted to the MHC class II compartment elicits long-lasting neutralizing antibodies. Vaccine 21(17-18):2178-89.
  • Raviprakash K, Kim JW, Ewing D, August TJ, Hayes CG, Porter KR. Antigen targeting to lysosomal vesicles increases antibody response to a dengue DNA vaccine in rhesus macaques.; 2004; Philadelphia, Pennsylvania.
  • Raviprakash K, Marques E, Ewing D, Lu Y, Phillips I, Porter KR, Kochel TJ, August TJ, Hayes CG, Murphy GS. 2001. Synergistic neutralizing antibody response to a dengue virus type 2 DNA vaccine by incorporation of lysosome-associated membrane protein sequences and use of plasmid expressing GM-CSF. Virology 290(1):74-82.

Hepatitis C virus

  • Brinster C, Muguet S, Lone YC, Boucreux D, Renard N, Fournillier A, Lemonnier F, Inchausp? G. 2001. Different hepatitis C virus nonstructural protein 3 (Ns3)-DNA-expressing vaccines induce in HLA-A2.1 transgenic mice stable cytotoxic T lymphocytes that target one major epitope. Hepatology 34(6):1206-17.

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SARS coronavirus

  • Gupta V, Tabiin TM, Sun K, Chandrasekaran A, Anwar A, Yang K, Chikhlikar P, Salmon J, Brusic V, Marques ET and others. 2005. SARS coronavirus nucleocapsid immunodominant T-cell epitope cluster is common to both exogenous recombinant and endogenous DNA-encoded immunogens. Virology.

Bacterial antigens

  • Uchiyama H, Nagata T, Yamada T, Uchijima M, Aoshi T, Suda T, Chida K, Nakamura H, Koide Y. 2002. Endosomal/lysosomal targeting of a single helper T-cell epitope of an intracellular bacterium by DNA immunisation induces a specific T-cell subset and partial protective immunity in vivo. FEMS Microbiol Lett 216(1):91-7.

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LAMP

  • Fernandes DM, Vidard L, Rock KL. 2000. Characterization of MHC class II-presented peptides generated from an antigen targeted to different endocytic compartments. Eur J Immunol 30(8):2333-43.
  • Pichurin PN, Chazenbalk GD, Aliesky H, Pichurina O, Rapoport B, McLachlan SM. 2004. “Hijacking” the thyrotropin receptor: A chimeric receptor-lysosome associated membrane protein enhances deoxyribonucleic acid vaccination and induces Graves’ hyperthyroidism. Endocrinology 145(12):5504-14.
  • Rodriguez F, Harkins S, Redwine JM, de Pereda JM, Whitton JL. 2001. CD4(+) T cells induced by a DNA vaccine: immunological consequences of epitope-specific lysosomal targeting. J Virol 75(21):10421-30.
  • Guarnieri, F.G., Arterburn, L.M.; Penno, M.B.; Cha, Y.; and August, J.T. The Motif Tyr-X-X-hydrophobicResidue Mediates Lysosomal Membrane Targeting of Lysosome-associated Membrane Protein 1. J. Biol. Chem., 268, 1941-1946 (1993).
  • Arterburn, L.M., Earles, B.J., and August, J.T. The disulfide structure of lysosomal membrane glycoprotein mLAMP-1. J. Biol. Chem., 265, 7419-7423 (1990).
  • Cha, Y., Holland, S.M., and August J.T. The cDNA sequence of mouse LAMP-2: evidence for two classes of lysosomal membrane glycoproteins. J. Biol. Chem., 265, 5008-5013 (1990).

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