Comparison of the magnitude of SIV-specific cellular immune responses in control and rituximab-treated rhesus macaques at early and late time points after SIV infection. (A) SIV-specific IFN-γ ELISPOT responses in control (CTRL) and rituximab-treated (RITUX) RMs at weeks 2 and 6, and 6 months after SIV infection shown. ELISPOT responses against SIV Gag and Pol proteins (Gag-specific and Pol-specific) as well as the sum of responses against individual SIV proteins representing the entire SIV proteome (total SIV-specific) shown. (B,C) Intracellular cytokine staining assay in control and rituximab-treated RMs at 6 weeks after SIV infection showing the frequency of (B) total SIV-specific CD8⁺ T lymphocytes and (C) total SIV-specific CD4⁺ T lymphocytes secreting IFN-γ, IL-2, TNF-α, and undergoing degranulation (surface CD107a⁺) after 16 hours of in vitro stimulation with SIV peptides in the presence of brefeldin A and monensin. Stimulation with SIVmac239 sequence-based peptide pool. Asterisks denote P values less than .05 (*) and less than .01 (**) for differences between and control and rituximab-treated RMs using the Mann-Whitney U test.