ABSTRACT

The PhD dissertation was carried out at the Department of Infectious Diseases at H:S Rigshopitalet, University Hospital of Copenhagen. It is based on three articles that describe the development of genotypic resistance in HIV-infected patients with virological failure on different HAART-combinations. Genotyping of the entire protease and most of the reverse transcriptase gene was performed with a commercial PCR-based whole-genome sequencing kit (TrueGene TM , Visible Genetics).

The first study investigated the genotypic resistance profile in 24 patients experiencing their first protease-inhibitor failure on nelfinavir-containing HAART. At failure we found a high frequency of primary protease mutations (58%), especially D30N (38%), which were significantly associated with presence of the secondary protease mutation N88D. The presence of primary protease mutations did not negatively affect outcome of second-line treatment.

The second study investigated the development of resistance in eight antiretroviral naive patients failing randomised treatment with at triple nucleoside analogue (NRTI) combination (n=60), consisting of abacavir, stavudine and didanosine. All five patients with wild-type virus at baseline developed the rare K65R mutation at failure and four of the five also acquired the S68G mutation. Therefore failure of a triple NRTI-combination is frequent with only the K65R mutation, which confers broad cross-resistance.

The third study retrospectively investigated the interplay between resistance and adherence at virological failure in patients randomised to three fundamentally different HAART-regimens, namely a triple NRTI-regimen (n = 60), a boosted protease inhibitor-based regimen (n = 115) or a three-class combination (n = 118). Adherence and genotypic resistance at time of failure were assessed from review of patient files and stored plasma samples. Treatment interruption or poor adherence accounted for the vast majority of failures (74%) and was associated with absence of resistance mutations. Failure with good adherence and resistance development was frequent in the triple NRTI combination suggesting week drug potency. Primary protease mutations were not detected in any patients failing a boosted saquinavir-based HAART indicating a high genetic barrier towards resistance, which might favour the use of these combinations as first-line options in patients with vulnerable adherence.