Influence of IFNgamma co-expression on the safety and antiviral efficacy of recombinant fowlpox virus HIV therapeutic vaccines following interruption of antiretroviral therapy.

Therapeutic immunization to stimulate host immune responses and control human immunodeficiency virus (HIV-1) replication is being investigated as a supplementary treatment for the management of HIV infection. On completion of an earlier study involving three vaccinations while taking combination antiretroviral therapy (CART), twenty-five subjects with plasma viral load (pVL) <50 copies/mL received a booster vaccination with either placebo (n = 7); fowl pox vaccine (rFPV) expressing HIV-1 Gag/Pol; [partial construct- PC (n = 8)] or rFPV coexpressing HIV-1 Gag/Pol and human interferon gamma[full construct - FC (n = 10)]. One week after the booster vaccination, participants stopped ART and were monitored for safety, pVL and immunological parameters for < or =20 weeks. The time weighted mean change (SD) from baseline plasma HIV RNA was 1.80 (0.72), 1.78 (0.91) and 0.96 (0.91) log(10) copies/mL for placebo, PC and FC recipients respectively (p = 0.06; mean differences between placebo and FC). Laboratory evaluations did not reveal differences in anti-HIV specific immune responses between study arms. No difference between treatment arms for host genetic factors known to affect pVL was demonstrated. In conclusion, vaccination with FC was associated with a trend toward lower rates of HIV replication following cessation of ART relative to placebo or PC. The promising antiretrovirological effect supports further study of FC in a larger trial with a broader population of patients with HIV disease.

Randomized, placebo-controlled, phase I/IIa evaluation of the safety and immunogenicity of fowlpox virus expressing HIV gag-pol and interferon-gamma in HIV-1 infected subjects.

We conducted a randomized, placebo-controlled double-blind trial to examine the safety and immunogenicity of a candidate HIV therapeutic vaccine based upon a recombinant fowl pox virus capable of coexpressing the human cytokine interferon-gamma and/or genes from HIV-1. Thirty-five eligible subjects were randomized (12 placebo, 11 fowlpox + HIV genes, 12 fowl pox + HIV genes + interferon gamma). All but one subject (placebo group) received three immunizations (by intramuscular injection on day 0, week 4 and week 12) and all completed 52 weeks of follow-up. All subjects continued to take combination antiretroviral therapy for the duration of study. There were no significant toxicity or safety concerns and the distribution of adverse events and their severity was consistent across each randomly assigned vaccine group. Comparison of placebo recipients with the combined recipients of the two vaccine constructs, in terms of anti-HIV gag ELISpot or lymphoproliferative responses, tended to favour the placebo group, but were not significantly different (difference in time-weighted mean change from baseline = 56 Spot forming units (sfu)/10(6) PBMC; p = 0.062 and 4.4 SI; p = 0.337). There were no significant changes in CTL responses by standard Cr(51) release assay. Anti-FPV antibodies were detected by week 14 in 0 placebo and 20 (87%) vaccine recipients. Although safe, neither vaccine construct appeared to possess detectable T-cell mediated anti-HIV immunogenic properties in HIV infected individuals, as measured by standard T cell assays.

The pharmacology of gene therapy.

The objective for human gene therapy is to express exogenous DNA at a site in vivo for long enough, and at sufficient levels to produce a therapeutic response. The obstacles to this objective are numerous and include the formulation or packaging of the DNA, in vivo delivery, penetration of biological barriers, DNA elimination within the cell and from the tissue compartments of the whole body, control of product expression and overt toxicity. The current challenge is to resolve each of these obstacles to produce a practical and efficient gene therapy. In doing so, it is vital to understand the disposition of DNA vectors in vivo, and to know how conventional medicines may be used to modulate this disposition and to enhance the therapeutic effect of these vectors. Many of the general concepts of human gene therapy have been reviewed extensively in the literature. This review discusses some of the pharmacological aspects of gene delivery and the fate of vectors in vivo, and then highlights how drugs are being used to modulate gene therapy.