A genotypic analysis of patients receiving Zidovudine with either Lamivudine, Didanosine or Zalcitabine dual therapy using the LiPA point mutation assay to detect genotypic variation at codons 41, 69, 70, 74, 184 and 215.

BACKGROUND

The Murex-Innogenetics LiPA HIV-1 RT assay can be used to identify the presence of mutations of the reverse transcriptase gene at codons 41, 69, 70, 74, 184 and 215 of HIV-1, which have been shown to confer resistance to the nucleoside analogs Zidovudine (ZDV), Lamivudine (3TC), Didanosine (ddI) and Zalcitabine (ddC). The M184V mutation of the reverse transcriptase gene of HIV-1 has been associated with resistance to 3TC, ddC and ddI. This mutation has also been observed in patients receiving ZDV+ddC and ZDV+ddI. We used LiPA HIV-1 RT assay to identify the presence of either consensus methionine 184 or the mutant valine 184 with three groups of patients who were treated with ZDV/3TC, ZDV/ddI or ZDV/ddC combination therapy.

OBJECTIVES

The aim of our study was to determine the viral genotype of patients who were considered to be failing therapy, by two ways: using sequencing and LiPA assays. In particular we were interested in establishing a possible correlation between these methods.

STUDY DESIGN

The study group consisted of a consecutive series of 33 patients with a treatment failure, 18 of whom received ZDV+3TC therapy, seven received ZDV+ddI and eight received ZDV+ddC therapy. We also examined a small cohort of seven seroconverters.

RESULTS

The M184V mutation was observed in 47.0% of patients receiving ZDV+3TC combination therapy but was not observed in either patient group receiving either ddI or ddC as co-therapy with ZDV. There was no evidence of the L74V mutation in our study group in either the ZDV/ddI or ZDV/ddC combination therapy group. We found the frequency of the K70R mutation to be higher in patients treated with ZDV/ddI (P=0.033) or ZDV/ddC (P=0.3) when compared with patients treated with ZDV/3TC.

CONCLUSION

The LiPA assay allowed for the rapid detection of wild type and amino acid variations at key positions conferring resistance to the most used antiviral RT inhibitors. This represented a rapid, quite sensitive, and simple genotyping test. For these reasons the LiPA assay proved to be useful in studying genetic resistance in large screenings, when key RT mutations could be useful in guiding an effective HIV-1 suppressing regimen.