Correlation of spontaneous suppressor cell activity with progression of human immunodeficiency virus infection

Correlation of clinical parameters and immunological function with human immunodeficiency virus plasma viremia in children

Studies of immune function in human immunodeficiency virus (HIV)-infected children are important, because functional abnormalities can precede CD4+ T-cell loss and are associated with the development of opportunistic and bacterial infections. We sought to correlate clinical parameters and immunological function with HIV RNA plasma levels in 20 children. HIV RNA levels were measured by a polymerase chain reaction assay. We analyzed T-cell responses to mitogens (phytohemagglutinin, concanavalin A, and pokeweed [PWM]) and antigens (tetanus toxoid and Candida albicans); T-cell suppressor activity; and humoral immunity to Haemophilus influenzae, hepatitis B, tetanus, and diphtheria vaccines. The median age of the children was 6 years. Eight children had HIV RNA levels less than 200 to 9621 copies per milliliter (group I). Four children had 37,970 to 82,630 copies per milliliter (group II). Eight children had 102,100 to 191,200 copies per milliliter (group III). There were no differences in the HIV-related complications between group I and II children. Group I/II children had significantly higher CD4+ T-cell counts (P = 0.02), less symptomatic HIV disease (P = 0.005), and more detectable protective vaccine immunity (P = 0.014) compared with group III children. Responses to mitogens were conserved in most children. Group I children tended to have higher responses to tetanus toxoid than group II children and significantly higher responses than group III children (P = 0.01). Group I had significantly higher responses to C. albicans than groups II (P = 0.016) and III (P = 0.001). Group I/II children tended to have lower suppressor activity compared with group III children (median, 0 vs 64%). We demonstrated that humoral and cellular immune dysfunction exists at all stages of disease in HIV-infected children but was most severe in children with greater than or equal to 100,000 HIV RNA copies per milliliter. Function was the most intact in children with less than 10,000 copies per milliliter.

Direct involvement of extracellular HIV-1 virions in the apoptosis of CD8+ lymphocytes: a two-step model

Lymphocytes of the CD8 phenotype play an important role in controlling viral burden in HIV-1 infection. Cytotoxic CD8+ T lymphocytes (CTL) can kill HIV-infected cells and in addition, are able to secrete a soluble factor that inhibits HIV replication. In most cases, HIV-infected individuals experience an unexplained CD8+ lymphopenia during the advanced stage of the disease that particularly affect HIV-1-specific CTL. It has been reported that CD8+ lymphocytes in HIV-infected individuals undergo programmed cell death or apoptosis. We now present a two-step model to explain CD8+ apoptosis, based on anchorage of HIV-1-associated MHC class 1 antigen into the envelope of extracellular viral particles.

A role for CD8+ T lymphocytes in the pathogenesis of AIDS

Experimental and clinical evidence is presented which supports the hypothesis that CD8+ T lymphocytes aimed at suppressing HIV replication in infected CD4+ T cells may have an important role in the pathogenesis of AIDS by directly causing a decrease in CD4+ T lymphocyte numbers. Possible models to test this hypothesis are discussed.