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Serial human immunodeficiency virus type-1 (HIV-1) isolates were obtained from five individuals with acquired immunodeficiency syndrome (AIDS) who changed therapy to 2',3'-dideoxyinosine (ddI) after at least 12 months of treatment with 3'-azido-3'-deoxythymidine (zidovudine, AZT). The in vitro sensitivity to ddI decreased during the 12 months following ddI initiation, whereas AZT sensitivity increased. Analysis of the reverse transcriptase coding region revealed a mutation associated with reduced sensitivity to ddI. When this mutation was present in the same genome as a mutation known to confer AZT resistance, the isolates showed increased sensitivity to AZT. Analysis of HIV-1 variants confirmed that the ddI resistance mutation alone conferred ddI and 2',3'-dideoxycytidine resistance, and suppressed the effect of the AZT resistance mutation. The use of combination therapy for HIV-1 disease may prevent drug-resistant isolates from emerging.

Our data disclose a previously undescribed pattern of cytokine alteration that is relevant to determine increased needs of EPO in hemodialysis patients. The present results have potential applicability in designing strategies to improve EPO resistance.

A molecular clone containing the wild-ype reverse transcriptase (RT) coding region of human immunodeficiency virus type 1 (iHV-1) was constructed, and sitedirected mutagenesis was used to introduce mutations-Leu74 --Val (L74V), T215Y, and the combination L74V/T215Y-into the RT coding region. The proteins were purified by immunoaffnity chromatography. Assays were performed with mutant and wild-ype RT to determine substrate and inhibitor specificity. AB three mutant enzymes catalyzed the incorporation of substrate 2'-deoxynucleoside 5'-triphosphates (dNTPs) as efficiently as wild-type IiV-1 RT. Small changes were observed in the Km values for dNTPs with all three mutant enzymes, while more significant changes were noted in sensitivity to nucleoside 5'-triphosphate analogues that inhibit the enzyme activity. Results suggest that altered substrate recognition by the HIV-1 RT is involved in the mechanism of resistance.

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To test whether (HCV) persistence is related to interferon (IFN) hyporesponsiveness, peripheral blood monuclear cells from 29 patients and 11 controls were studied for MxA protein expression. In vitro, only IFN-alpha (P<.001) and interleukin-2 (P<.05) induced MxA protein expression above unstimulated levels. Forty patients were treated with IFN-alpha2b. Patients showed higher basal levels of MxA protein (P<.02) and 2',5'-oligoadenylate synthase (2-5A) activity (P<.05) than controls. During therapy, MxA protein levels (P<.001) and 2-5A activity (P<.05) increased; after 1 month, MxA levels remained high, whereas 2-5A activity declined to initial levels. Increases in MxA were inversely correlated with decreases in serum alanine aminotransferase levels, and MxA induction was greater among virological responders. Thus, the IFN system seems to be activated in chronic HCV infection, but HCV appears to modulate these two components of the IFN system differentially. These results suggest that an inefficient response may contribute to virus persistence and affect the therapeutic outcome.

The degree of genetic variability in the hypervariable region 1 of hepatitis C virus (HCV) was analyzed by cloning and sequencing HCV genomes obtained in paired samples of serum, liver tissue, and peripheral blood mononuclear cells (PBMC) from four chronic hepatitis C patients. Genetic variability in serum was higher than in liver tissue or PBMC at the level of complexity (the number of different sequences obtained from each type of tissue) as well as at the level of genetic distance between all pairs of sequences within each tissue (compared by the Student t test; P < 0.001 for two patients and P < 0.01 for another). The spectrum of viral genomes differed among the three types of tissue, as shown by segregation of sequences according to their tissue of origin in phylogenetic analysis and by statistical analysis of mean genetic distances observed between sequences obtained from different tissues (P < 0.001), but sequences from liver tissue and PBMC were more closely related to each other than to those from serum.