Infection with Dual-Tropic Human Immunodeficiency Virus Type 1 Variants Associated with Rapid Total T Cell Decline and Disease Progression in Injection Drug Users

The characteristics of sequential human immunodeficiency virus type 1 (HIV-1) isolates from 12 seroconverters among injection drug users selected for either rapid or slow disease progression were evaluated. All 6 patients who developed AIDS within 5 years were initially infected with syncytium-inducing (SI) variants or showed a transition from non-SI-inducing (NSI) to SI variants. Detection of SI variants was associated with rapid decline of both CD8+ and CD4+ T cells. In contrast, the 6 slow progressors carried only NSI variants and maintained stable or increasing CD8+ T cell levels. The SI variants that were associated with initial infection were dual tropic, with efficient replication in primary macrophages and T cell lines. These results suggest that the ability to replicate in macrophages, rather than the SI or NSI phenotype per se, may be an important determinant of HIV-1 transmission and that dual-tropic viruses, when transmitted, may be associated with rapid progression to AIDS.