Humoral correlates of immune protection in SIVΔnef vaccinated animals.

(A) TCLA SIVmac251 neutralizing antibody titers in serum on the day of challenge inversely correlated with peak post-challenge SIVmac251 viral loads. (B) TCLA neutralizing antibody titers in sterilely protected (though not partially protected) Grp 20/40 animals were significantly higher than those in unprotected Grp 5 animals. (C) Levels of anti-Env IgG binding antibodies in serum on the day of challenge and (D) anti-Env IgG specific activity in vaginal secretions collected 2 weeks before challenge, were inversely associated with peak post-challenge viremia. (E, F) The avidity of Env-specific serum IgG and IgA on the day of challenge was also significantly greater in sterilely protected animals. (G, H) Avidity of anti-Env serum antibodies in SIVΔnef vaccinated animals inversely correlated with peak post-challenge viremia. Two-tailed Spearman tests were used for all correlations and two-tailed Mann-Whitney tests were used for all comparisons between groups. Exclusion of the sterilely protected animals from the analysis presented in panel 5D also demonstrated a significant correlation between antibody titer and viral load (p = 0.049), while non-significant trends were noted for panels 5A, C, G and H when sterilely protected animals were excluded (p values = 0.076, 0.35, 0.36 and 0.074, respectively).