Conversion rate towards a syncytium-inducing (SI) phenotype during different stages of human immunodeficiency virus type 1 infection and prognostic value of SI phenotype for survival after AIDS diagnosis

The presence of syncytium-inducing (SI) human immunodeficiency virus type 1 (HIV-1) variants is predictive for accelerated progression to AIDS. This study showed that a 4-year survival with AIDS also occurred significantly more often for patients who lacked SI variants. However, multivariate Cox analysis excluded the predictive value of SI viruses for rapid death as being independent from low CD4⁺ T cell counts. Incidence of appearance of SI variants was increased in persons with CD4⁺ T cell counts <500/μL but remained constant in the strata of CD4⁺ T cell counts <500/μL, excluding the possibility that loss of immune control is the only prerequisite for the development of SI HIV-1 variants.