Analysis of CD4 cell responses during 48 weeks of enfuvirtide therapy after virological failure (analysis of covariance) demonstrated significant associations between V38 mutations (n = 58 subjects) and continued CD4 cell increases and between Q40 mutations (n = 8) and loss of CD4 cell benefit (+34 versus -95 cells/mul, P < 0.001). Subjects with N43 (n = 20) or other mutations (n = 48) had intermediate CD4 cell responses. These data suggest that key enfuvirtide resistance mutations may be associated with reduced viral pathogenicity in vivo.
