The evolutionary dynamics of HIV-1 quasispecies and the development of immunodeficiency disease.

This paper presents a theory to explain the development of immunodeficiency disease after a long and variable incubation period of infection with HIV-1. Two assumptions are central to the theory: (1) mutation via reverse transcription during viral replication can generate viral strains resistant to neutralization by antibodies specific to earlier mutants in a particular host; (2) the virus can kill the CD4-positive lymphocytes that play a role in mounting an immunological attack directed at the virus. The theory is examined via the development of a mathematical model which reveals that an increasing number of antigenically distinct viral strains may overwhelm the immune system of the host. As the viral diversity increases beyond a certain level the immune system is unable to suppress the population growth of all the strains simultaneously. The intuitive explanation of this pattern of model behaviour lies in the assumption that each virus can kill CD4-positive lymphocytes that are specific to any of the viral strains, but each lymphocyte only directs immunological attack against a single viral strain.(ABSTRACT TRUNCATED AT 250 WORDS)