Vaccine Development for Potential Bioterrorism Agents

CpG used as an adjuvant for an adenovirus-based Venezuelan equine encephalitis virus vaccine increases the immune response to the vector, but not to the transgene product

An adenovirus-based (ad-based) vaccine delivering antigens from the Alphavirus Venezuelan equine encephalitis virus (VEEV) is a strategy that offers clinical potential. A vaccine against VEEV is desirable because of the re-emerging nature of this virus, and also the potential that it may be used as a biological weapon. This study was designed to investigate whether the co-administration of CpG oligodeoxynucleotides (ODNs) with an ad-based VEEV vaccine could enhance the protective efficacy of the vaccine. We report that the co-administration of CpG ODN was unable to increase VEEV-specific antibody responses in mice, and was unable to increase the protective efficacy of the vaccine against aerosol challenge with virulent VEEV. However, it was noted that antibody responses directed against the adenovirus vaccine vector were increased, which may be detrimental, particularly in the context of homologous boosting.

Potent antiviral synergy between monoclonal antibody and small-molecule CCR5 inhibitors of human immunodeficiency virus type 1

The chemokine receptor CCR5 provides a portal of entry for human immunodeficiency virus type 1 (HIV-1) into susceptible CD4(+) cells. Both monoclonal antibody (MAb) and small-molecule CCR5 inhibitors have entered human clinical testing, but little is known regarding their potential interactions. We evaluated the interactions between CCR5 MAbs, small-molecule CCR5 antagonists, and inhibitors of HIV-1 gp120, gp41, and reverse transcriptase in vitro. Inhibition data were analyzed for cooperative effects using the combination index (CI) method and stringent statistical criteria. Potent, statistically significant antiviral synergy was observed between the CCR5 MAb PRO 140 and the small-molecule CCR5 antagonists maraviroc (UK-427,857), vicriviroc (SCH-D), and TAK-779. High-level synergy was observed consistently across various assay systems, HIV-1 envelopes, CCR5 target cells, and inhibition levels. CI values ranged from 0.18 to 0.64 and translated into in vitro dose reductions of up to 14-fold. Competition binding studies revealed nonreciprocal patterns of CCR5 binding by MAb and small-molecule CCR5 inhibitors, suggesting that synergy occurs at the level of receptor binding. In addition, both PRO 140 and maraviroc synergized with the chemokine RANTES, a natural ligand for CCR5; however, additive effects were observed for both small-molecule CCR5 antagonists and PRO 140 in combination with other classes of HIV-1 inhibitors. The findings provide a rationale for clinical exploration of MAb and small-molecule CCR5 inhibitors in novel dual-CCR5 regimens for HIV-1 therapy.

Discordances between interpretation algorithms for genotypic resistance to protease and reverse transcriptase inhibitors of human immunodeficiency virus are subtype dependent

The major limitation of drug resistance genotyping for human immunodeficiency virus remains the interpretation of the results. We evaluated the concordance in predicting therapy response between four different interpretation algorithms (Rega 6.3, HIVDB-08/04, ANRS [07/04], and VGI 8.0). Sequences were gathered through a worldwide effort to establish a database of non-B subtype sequences, and demographic and clinical information about the patients was gathered. The most concordant results were found for nonnucleoside reverse transcriptase (RT) inhibitors (93%), followed by protease inhibitors (84%) and nucleoside RT inhibitor (NRTIs) (76%). For therapy-naive patients, for nelfinavir, especially for subtypes C and G, the discordances were driven mainly by the protease (PRO) mutational pattern 82I/V + 63P + 36I/V for subtype C and 82I + 63P + 36I + 20I for subtype G. Subtype F displayed more discordances for ritonavir in untreated patients due to the combined presence of PRO 20R and 10I/V. In therapy-experienced patients, subtype G displayed a lot of discordances for saquinavir and indinavir due to mutational patterns involving PRO 90 M and 82I. Subtype F had more discordance for nelfinavir attributable to the presence of PRO 88S and 82A + 54V. For the NRTIs lamivudine and emtricitabine, CRF01_AE had more discordances than subtype B due to the presence of RT mutational patterns 65R + 115 M and 118I + 215Y, respectively. Overall, the different algorithms agreed well on the level of resistance scored, but some of the discordances could be attributed to specific (subtype-dependent) combinations of mutations. It is not yet known whether therapy response is subtype dependent, but the advice given to clinicians based on a genotypic interpretation algorithm differs according to the subtype.

DNA vaccines for biodefence

The advantages associated with DNA vaccines include the speed with which they may be constructed and produced at large-scale, the ability to produce a broad spectrum of immune responses, and the ability for delivery using non-invasive means. In addition, DNA vaccines may be manipulated to express multiple antigens and may be tailored for the induction of appropriate immune responses. These advantages make DNA vaccination a promising approach for the development of vaccines for biodefence. In this review, the potential of DNA vaccines for biodefence is discussed.