CD4 and infection: Within the S-specific T cell response, CD8/CD4 ratios were similar between BTI and non-BTI within the first two weeks of infection (0.2 - 0.4), while median CD8/CD4 ratios were 2- to 5-fold higher in BTI versus non-BTI versus during weeks 3 (p=0.06), 4 (p=0.06), and 5 (p=0.18).