HIVIS-DNA or HIVISopt-DNA priming followed by CMDR vaccinia-based boosts induce both humoral and cellular murine immune responses to HIV.

BACKGROUND: In order to develop a more effective prophylactic HIV-1 vaccine it is important optimize the components, improve Envelope glycoprotein immunogenicity as well as to explore prime-boost immunization schedules. It is also valuable to include several HIV-1 subtype antigens representing the world-wide epidemic. METHODS: HIVIS-DNA plasmids which include Env genes of subtypes A, B and C together with Gag subtypes A and B and RTmut/Rev of subtype B were modified as follows: the Envelope sequences were shortened, codon optimized, provided with an FT4 sequence and an immunodominant region mutated. The reverse transcriptase (RT) gene was shortened to contain the most immunogenic N-terminal fragment and fused with an inactivated viral protease vPR gene. HIVISopt-DNA thus contains fewer plasmids but additional PR epitopes compared to the native HIVIS-DNA. DNA components were delivered intradermally to young Balb/c mice once, using a needle-free Biojector® immediately followed by dermal electroporation. Vaccinia-based MVA-CMDR boosts including Env gene E and Gag-RT genes A were delivered intramuscularly by needle, once or twice. RESULTS: Both HIVIS-DNA and HIVISopt-DNA primed humoral and cell mediated responses well. When boosted with heterologous MVA-CMDR (subtypes A and E) virus inhibitory neutralizing antibodies were obtained to HIV-1 subtypes A, B, C and AE. Both plasmid compositions boosted with MVA-CMDR generated HIV-1 specific cellular responses directed against HIV-1 Env, Gag and Pol, as measured by IFNγ ELISpot. It was shown that DNA priming augmented the vector MVA immunological boosting effects, the HIVISopt-DNA with a trend to improved (Env) neutralization, the HIVIS-DNA with a trend to better (Gag) cell mediated immune reponses. CONCLUSIONS: HIVIS-DNA was modified to obtain HIVISopt-DNA that had fewer plasmids, and additional epitopes. Even with one DNA prime followed by two MVA-CMDR boosts, humoral and cell-mediated immune responses were readily induced by priming with either DNA construct composition. Priming by HIV-DNA augmented neutralizing antibody responses revealed by boosting with the vaccinia-based heterologous sequences. Cellular and antibody responses covered selected strains representing HIV-1 subtypes A, B, C and CRF01_AE. We assume this is related to the inclusion of heterologous full genes in the vaccine schedule.

Therapeutic efficacy of a DNA vaccine targeting the endothelial tip cell antigen delta-like ligand 4 in mammary carcinoma.

The Notch ligand delta-like ligand 4 (DLL4) is an essential component expressed by endothelial tip cells during angiogenic sprouting. We have described a conceptually novel therapeutic strategy for targeting tumor angiogenesis and endothelial tip cells based on DNA vaccination against DLL4. Immunization with DLL4-encoding plasmid DNA by in vivo electroporation severely retarded the growth of orthotopically implanted mammary carcinomas in mice by induction of a nonproductive angiogenic response. Mechanistically, vaccination brought about a break in tolerance against the self-antigen, DLL4, as evidenced by the production of inhibitory and inherently therapeutic antibodies against mouse DLL4. Importantly, no evidence for a delayed wound healing response, or for toxicity associated with pharmacological blockade of DLL4 signaling, was noted in mice immunized with the DLL4 vaccine. We have thus developed a well-tolerated DNA vaccination strategy targeting the endothelial tip cells and the antigen DLL4 with proven therapeutic efficacy in mouse models of mammary carcinoma; a disease that has been reported to dramatically induce the expression of DLL4. Conceivably, induction of immunity toward principal mediators of pathological angiogenesis could provide protection against recurrent malignant disease in the adjuvant setting.

Enhancement of epitope-specific cellular immune responses by immunization with HIV-1 peptides genetically conjugated to the B-subunit of recombinant cholera toxin.

As more HIV-1 infected patients receive anti-retroviral drug treatment, the occurrence of drug-resistant variants of the virus is increasing. We have previously shown that mutated HIV peptide sequences represent mutations induced by antiretroviral drugs are equally good and often better immunogens than wild type peptides. The non-toxic B subunit of cholera toxin (CTB) is an active substance in the oral cholera vaccine, and has been shown to bind ganglioside receptors and activate mucosal cells. By fusing mutant epitopes deriving from HIV-1 enzymes with the B subunit of cholera toxin, we aim is to induce cellular responses against virus harboring drug-induced mutations. We successfully created conjugates of HIV peptide sequences fused to rCTB. The immune response against the different peptides was strongly enhanced by the fusion to the toxin. Moreover, immunization with sequence containing drug-induced mutation triggered a cross-reactive immune response against the wild type epitope. Long-term follow-up of immunized animals revealed a persistence of cellular immune response for over 4 months, which could readily be boosted with an additional late immunization. By linking HIV-peptides to the B subunit of cholera toxin it is thus possible to stimulate a strong and long-lasting immune response, significantly better than that evoked by the peptide alone.

Pre-clinical evaluation of a CEA DNA prime/protein boost vaccination strategy against colorectal cancer.

In preparation for a clinical trial in patients diagnosed with colorectal cancer, a vaccination strategy targeting the carcinoembryonic antigen (CEA) was evaluated in mice using a GMP-produced plasmid DNA vaccine, CEA66, encoding a truncated form of the tumour-associated antigen, CEA. The GMP-produced CEA DNA vaccine was also evaluated for toxicity. Repeated intradermal administration of the GMP-produced vaccine using a novel needle-free jet injection device (Biojector) induced robust CD4 and CD8 T-cell responses in mice, and did not result in any vaccine-related toxicity. In a heterologous DNA prime/protein boost setting, cellular immune responses were of higher magnitude in animals primed with CEA66 DNA than in animals receiving repeated doses of recombinant CEA protein. These responses were further enhanced if recombinant murine granulocyte-macrophage colony-stimulating factor was given as an adjuvant prior to vaccination. In contrast to repeated administration of recombinant CEA protein as a single modality vaccine, the heterologous CEA66 DNA prime/rCEA boost vaccination strategy resulted in a qualitatively broader immune response, and supports clinical testing of this vaccination regimen in humans.

The rationale behind a vaccine based on multiple HIV antigens.

The viral diversity of HIV-1 is likely to require a vaccine strategy that induces broad cellular and humoral anti-HIV-1 immunity. Our strategy is based on multiple HIV-1 DNA immunogens together with adjuvant recombinant granulocyte-macrophage stimulating factor. This article describes pre-clinical and clinical work preceding the initiation of clinical HIV-1 phase I/II trials.