The role of viral diversity in HIV pathogenesis.

From the time of seroconversion, patients who retain a high viral load are known to progress more rapidly to AIDS than individuals who have lower levels of HIV. Increased viral load is accompanied by decreasing CD4 cell numbers, and CD4 cell counts are therefore widely used as a diagnostic marker or predictor of progression in HIV patients. During the asymptomatic phase, however, CD4 counts often remain in the "normal" range, and this marker provides little information on potential disease progression. A shift in viral phenotype from non-syncytium-inducing (NSI) to syncytium-inducing (SI) heralds disease progression, and early in infection SI progression can be distinguished from nonprogression on the basis of CD4 changes. NSI progression, on the other hand, cannot be distinguished from nonprogression on the basis of CD4 counts but can be distinguished on the basis of RNA load. Molecular assessment of viral phenotype, such as quantitative measures of HIV RNA, as well as syncytium-inducing and nonsyncytium-inducing is therefore able to provide valuable information on the probable course of progression in individual patients, thus aiding in more effective disease management.