Next, we tested whether CCL3L1 variation influences disease progression. We used both a quantitative measure of progression introduced previously6 (consisting of measured or estimated time to CD4+ cell count< 350 per mm3 or initiation of antiretroviral therapy; Supplementary Methods) and a simple case-to-control comparison of progressors versus nonprogressors (defined as progression to CD4+ cell count< 350 per mm3 or antiretroviral therapy within 10 years since seroconversion versus no progression within 10 years). Finally, we tested for an effect of CCL3L1low versus CCL3L1high group assignment on these measures as well as on progression to AIDS 1987, AIDS 1993 or AIDS-related death using a Cox proportional hazards model. Neither CCL3L1 copy number nor CCL3L1low versus CCL3L1high genotype group assignment was associated with disease progression under any of these models