The role of the protease cleavage sites in viral fitness and drug resistance in HIV-1 subtype C.
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Date
2010
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Abstract
There is an increasing number of patients failing second line highly active antiretroviral therapy
(AZT, DDI and LPV/r) in South Africa, where HIV-1 subtype C predominates. Mutations at gag
cleavage sites (CS) have been found to correlate with resistance mutations in protease (PR).
Therefore, it is important to collect data on subtype C protease and gag sequences from patients
as these mutations may affect the efficacy of protease inhibitor (PI) containing drug regimens.
In this study, 30 subtype-C infected second-line failures were genotyped using the ViroSeqTM
resistance genotyping kit and the gag region from these isolates were then characterised. These
sequences were then compared to 30 HIV-1 subtype C infected first-line failures (PI-naïve) and
subtype B, C and group M naïve sequences that were downloaded from the Los Alamos
Sequence Database. Amino acid diversity at the CS was measured using Mega version 4.0. To
investigate the effect of CS mutations on replication capacity, a mutation was introduced by
site-directed mutagenesis (Stratagene’s QuikChange Site-Directed Mutagenesis kit).
Of the 30 second-line failures that we genotyped, only 16 had resistance mutations in PR and 23
in gag. The most frequent major PI mutations were: I54V/L, M46I, V82A, and I84V and in gag
CS were V390L/I and A431V. Interestingly the A431V mutation significantly correlated with
protease mutations M46I/L, I54V and V82A. The virus carrying the A431V mutation in vitro
was found to have a lower replication capacity compared to the wild type.
These findings emphasize the need for further investigation of gag mutations and their
contribution to the evolution of HIV resistance to PIs.
Description
Thesis (M.Med.Sc.)-University of KwaZulu-Natal, Durban, 2010.
Keywords
Protease inhibitors., Highly active antiretroviral therapy., Drug resistance., HIV infections., Reverse transcriptase., Theses--Molecular virology.