HIV-1 viraemia changes in patients with and without syncytium-inducing phenotype treated with nucleoside analogues: a case-control study

Abstract. The objective of the present study was to investigate the effect of the nucleoside analogue treatment on serum viraemia, CD4+ cell count and disease progression in patients with and without syncytium-inducing (SI) HIV-I variants. To achieve this in a case-control study, 11 nucleoside-naive patients harbouring SI variants who started treatment with zidovudine or zidovudine plus didanosine were matched with 11 control patients who never formed SI variants during a follow-up of 48 weeks. The matching criteria were age, CD4+ cell count and CDC clinical category at the start of the study and exposure to the same antiretroviral treatment. During the follow-up there were no significant differences in the changes of serum HIV-I RNA viral load and CD4+ cell counts between the two groups. In contrast, AIDS or new AIDS-defining events were observed in five SI cases but in none of the non-SI controls ( P = 0.002). The emergence of a zidovudine-resistant mutation at codon 215 was observed in all the patients harbouring SI strains and in six of the subjects with non-SI variants ( P = 0.03). The results of the present study show that in patients carrying SI virus, measurements of CD4+ count or RNA viral burden are neither related to the virulence of the virus strains nor able to predict the clinical course of the disease, at least under antiretroviral drug conditions. Thus, determination of SI phenotype should be considered in the evaluation and monitoring of HIV-I therapies.