FIG. 4.

Improved survival rates for macaques vaccinated with MVA-SIV recombinants are associated with preservation of CD4⁺ central memory T cells. (A) Kaplan-Meier plot of cumulative survival indicates significant differences between the control group and groups immunized with MVA-SIV recombinants expressing SIV env. The comparison of survival in these groups of monkeys was done using a Gehan-Wilcoxon test. P values for groups of vaccinated macaques compared to the control group are indicated. (B) The absolute number of memory CD4⁺ T cells (left) or percentage of prechallenge memory CD4⁺ cells remaining (right) at 20 weeks postchallenge is shown for animals that survived less than 1 year, between 1 and 2 years, or more than 2 years. Significant preservation of memory CD4⁺ T cells was observed in animals that survived 1 to 2 years or longer. (C) Scatter plots of the correlation between the percentage of central memory CD4⁺ T cells left in peripheral blood at week 4 (left) or week 20 (right) post-SIVsm infection and survival (weeks) of control and vaccinated macaques. Monkeys immunized with MVA-SIV recombinants expressing SIV env (MVA-env or MVA-gag-pol-env) are shown by solid diamonds, and open diamonds indicate animals immunized with MVA-GP or control MVA. P values for the Spearman rank correlation test are indicated.