Changes in plasma amino acid concentrations in response to HIV-1 infection.

Plasma concentrations of 21 amino acids were determined for 20 control subjects and 20 subjects infected with human immunodeficiency virus type 1 (HIV). Compared with the control subjects, the HIV-infected group had lower cystine, tryptophan, and methionine (decreased 67%, 52%, and 32%, respectively, P < 0.001 for each) and increased taurine (230%, P < 0.001) and lysine concentrations (30%, P < 0.001). Other amino acid concentrations changed modestly. Amounts of cystine, tryptophan, methionine, taurine, and lysine did not differ significantly between subgroups of HIV-infected subjects with > 200 (n = 6) or < 200 (n = 14) CD4+ lymphocytes per microliter, suggesting that the concentrations decrease soon after infection and change little thereafter. Activation of metabolism of cystine to taurine may explain reciprocal changes in these amino acids and known depletion of cystine and glutathione. The selective changes in amino acid profiles observed during HIV infection differ from those recognized for malnutrition or other pathological processes.