Evidence suggests that the New World was colonized only 11,000-40,000 years ago by Palaeo-Indians. The descendants of these Palaeo-Indians therefore provide a unique opportunity to study the effects of selection on major histocompatibility complex class I genes over a short period. Here we analyse the class I alleles of the Waorani of South America and the Zuni of North America. Four of the Waorani HLA-B alleles were new functional variants which could be accounted for by intralocus recombination. In contrast, all of the Zuni HLA-A and -B molecules were present in caucasians and orientals. This suggests that the new Waorani HLA-B variants arose in South America. The description of four new HLA-B alleles in the Waorani and another five new HLA-B alleles from two other tribes of South American Amerindians indicates that the HLA-B locus can evolve rapidly in isolated populations. These studies underline the importance of gathering genetic data on endangered native human populations.

Proinflammatory cytokines may be important in the pathogenesis of human immunodeficiency virus type 1 (HIV-1) disease. Tenidap decreases interleukin (IL)-6, IL-1, and tumor necrosis factor (TNF) production by peripheral blood mononuclear cells and decreases IL-6 plasma levels in rheumatoid arthritis patients. In this randomized double-blind study, 43 HIV-1-infected patients received tenidap (120 mg) or placebo daily for 6 weeks and then crossed over to the alternative therapy for an additional 6 weeks. Mean entry CD4 cell count was 140/microL. Analyses were performed on cytokines, acute-phase proteins, virus load, and CD4 cell counts. With the exception of small differences in plasma TNF levels, tenidap had no significant effect on these indices. Significant correlations of plasma IL-6 and TNF levels with HIV-1 RNA were noted. Six patients discontinued tenidap due to rash. The effects of tenidap in HIV-1 infection contrast to results in arthritis patients, in whom tenidap decreased plasma levels of IL-6 and acute-phase proteins.

The genetic basis for didanosine (ddl) resistance in human immunodeficiency virus (HIV-1) has previously been shown to be commonly associated with a Leu to Val change at codon 74 in the HIV-1 RT gene. In this study sequential viral isolates were analyzed from five patients with prior zidovudine (AZT) use who received 6 to 16 months of ddl therapy. Following ddl therapy, viral isolates exhibited an increased AZT susceptibility and decreased ddl susceptibility. Sequence and nested PCR analysis of the HIV-1 RT gene revealed that two viral isolates contained the Leu to Val change at codon 74, and three other isolates with reduced susceptibility to ddl each contained changes at codons 65, 70, and 72. Site-directed mutagenesis was employed to insert specific mutations in RT gene of proviral clone pNL4-3. Analysis of virion-associated reverse transcriptase activity indicated that the Lys70Arg mutation resulted in an enzyme with 2- to 4-fold decreased susceptibility to ddATP. Statistical analysis of the inhibitory concentration for RT activity between pNL4-3 and mutant Lys70Arg viruses obtained in three independent RT inhibition assays was significant (P = 0.05) by student t test paired analysis. Drug susceptibility assays on the virus with Lys70Arg mutation showed a marginal decrease in susceptibility to ddl (1.5- to 2-fold) and about 4- to 6-fold decrease in susceptibility to AZT. Mutations Lys65Glu and Arg72Ser resulted in an impaired RT with greatly diminished functional RT activity. The AZT-associated Lys70Arg mutation results in an RT enzyme with decreased susceptibility to ddATP.

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