ALVAC-HIV vaccine showed immunogenicity across several HIV clades in an early trial involving 100 healthy patients at low risk of HIV infection, according to a study by Glenda E. Gray, MBBCH, FCPaed, of the University of the Witwatersrand, Johannesburg, South Africa, and colleagues that was published online in the Sep. 18 issue of Science Translational Medicine.
Prof. Glenda E. Gray
ALVAC-HIV (vCP1521) is a live attenuated recombinant canarypox-derived virus that expresses gene products from the HIV-1 gp120 (92TH023/clade E), Gag (clade B), and Pro (clade B) that is cultured in chicken embryo fibroblast cells.
Four injections of ALVAC-HIV were given at months 0, 1, 3, and 6. At months 3 and 6, two booster injections were given of AIDSVAX/BE, a bivalent HIV glycoprotein 120 (gp120) that was previously studied in the RV144 trial. The HVTN 097 trial examined primary immunogenicity endpoints including the frequency and magnitude of IgG and IgG3 antibody binding, measured in serum specimens obtained at baseline, at a peak time point (2 weeks after second ALVAC/AIDSVAX vaccination), a durability time point (6 months after second ALVAC/AIDSVAX vaccination), and the response rates and magnitudes of CD4+ and CD8+ T-cell responses at the baseline, peak, and durability time points. One hundred healthy adults at low risk for HIV infection were randomized in 3:1:1 ratio to group T1 (HIV vaccines, tetanus vaccine, and hepatitis B vaccine), group T2 (HIV vaccine only), and the placebo group T3 (tetanus vaccine and hepatitis B vaccine). There were no meaningful differences in HIV immune responses between the HIV vaccine recipients with or without the tetanus and hepatitis B vaccines, so the researchers pooled the data from groups T1 and T2 in their analysis.
At the peak immunogenicity time point, the vaccine schedule predominantly induced CD4+ T cells directed to HIV-1 Env; this was measured by expression of interleukin-2 and/or interferon-gamma. The Env-specific CD4+ T-cell response rate was significantly higher in HVTN 097 vaccine recipients than it was in those in the RV144 trial (51.9% vs. 36.4%; P = .043). The HVTN 097 trial also showed significantly higher response rates for CD40L(59.3% for HVTN 097 vs. 33.7% for RV144; P less than .001) and for interferon-gamma (42.6% in HVTN 097 vs. 19.5% in RV144; P = .001).
However, durability at 6 months after the second vaccine injection remained an issue, with the frequency of circulating Env-specific CD4+ T-cell responses among vaccine recipients declining significantly; the response rate dropped from 70.8% to 36.1%.
“These data may indicate that cross-clade immune responses, especially to non-neutralizing epitopes correlated with decreased HIV-1 risk, can be achieved for a globally effective vaccine by using unique HIV Env strains,” Dr. Gray and associates concluded.
The authors declared that they had no competing interests.
SOURCE: Gray GE et al. Sci. Transl. Med. 2019 Sep 18. doi: 10.1126/scitranslmed.aax1880..