The Role of HIV Type 1 Phenotype and Genotype in Long-Term Responders to Zidovudine Therapy

Abstract

We performed a cross-sectional and partly retrospective virological evaluation of 31 long-term responders (LTRs) to zidovudine (ZDV) (persistent increase in the CD4⁺ cell counts without progression of HIV infection throughout a period of ZDV therapy >3 years) and 17 well-matched controls who developed a marked immunological deterioration over a 24-month period of ZDV therapy.

The biological phenotype of HIV-1 was assessed by testing the capacity of the isolates to replicate in the MT-2, HUT-78, C-8166, and U-937 T cell lines, and mutations at codons 215 and 41 of RT were checked in proviral DNA from uncultured PBMCs.

Slow/low non-syncytium-inducing (S/L-NSI) and rapid/high syncytium-inducing (R/H-SI) variants were detected in 25 (81%) and 2 (6%) LTRs, respectively. HIV-1 could not be isolated in the remaining four LTRs (13%). Conversely, 12 of 17 (71%) controls yielded R/H-SI variants. Conversion from the S/L-NSI to R/H-SI phenotype occurred in 5 controls but in none of the 18 LTRs tested. Mutant sequences in proviral DNA from control PBMCs were consistently detected (94%), while a wild-type sequence of the residues investigated was found in the majority of LTRs (77%).

In our series, patients who received immunological and clinical benefits even after prolonged ZDV treatment had S/L-NSI viruses and a low risk to develop ZDV resistance. Conversely, subjects who demonstrated an immunological and clinical deterioration yielded R/H-SI variants or shifted from S/L-NSI to R/H-SI phenotypes and were at higher risk to develop mutations indicating ZDV resistance.