A substantial frequency of resistance to antiretroviral drugs was identified in a therapy-naïve U.S. cohort. In most cases, the genotypic and phenotypic assays yielded similar results, although the genotypic assay could detect some protease inhibitor resistance-associated mutations in the absence of phenotypic resistance. These data suggest the need for optimization of treatment guidelines based on current estimates of the prevalence of drug resistance in HIV-1 seroconverters.
The cellular immunologic and virologic status of a chimpanzee, naturally infected with a human immunodeficiency virus type 1 (HIV-1)-like lentivirus (SIVcpz-ant), was compared longitudinally with those of 3 HIV-1-infected and 5 uninfected chimpanzees for a period of 49 months. Evidence of immune deficiency was not observed in the HIV-1-infected chimpanzees, nor could virus be isolated from plasma. Virus could be isolated from plasma of the SIVcpz-ant-infected chimpanzee, but clinical signs of immune deficiency were never observed. Absolute CD4+ cell counts remained relatively stable, but NK cells fluctuated significantly over time and tended to correlate inversely with the virus titer in peripheral blood. Although only CD8+ T cells were directly demonstrated to exert a suppressive effect on viral replication in vitro, the observed fluctuation of NK cells suggests that these cells may also be involved in the interaction with lentivirus infection in this species.
In a longitudinal study we address the hypothesis that resis tance to disease progression in lentivirus-infected chimpanzees is related to potent non-cytotoxic suppression of virus replication. In a long-term follow-up, the viral suppressive capacity in two simian immunodeficiency virus (SIV)cpz-infected chimpanzees was correlated with two polymerase chain reaction (PCR)- and two culture-based virus load measurements. In both animals, quantitative virus isolation (QVI) tended to decline slowly, whereas in vitro virus suppression was sustained or increased over time. In general, plasma virus loads in SIVcpz-infected animals were maintained for extended periods of time. Based on current assays that measure virus suppressive capacity in peripheral blood, it was not possible to conclude that virus suppression played a major role in the maintenance of the disease-free state in lentivirus-infected chimpanzees.
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