Persistence and fitness of multidrug-resistant human immunodeficiency virus type 1 acquired in primary infection

Abstract

This study examines the persistence and fitness of multidrug-resistant (MDR) viruses acquired during primary human immunodeficiency virus infection (PHI). In four individuals, MDR infections persisted over the entire study period, ranging from 36 weeks to 5 years, in the absence of antiretroviral therapy. In stark contrast, identified source partners in two cases showed expected outgrowth of wild-type (WT) virus within 12 weeks of treatment interruption. In the first PHI case, triple-class MDR resulted in low plasma viremia (1.6 to 3 log copies/ml) over time compared with mean values obtained for an untreated PHI group harboring WT infections (4.1 to 4.3 log copies/ml). Increasing viremia in PHI patient 1 at week 52 was associated with the de novo emergence of a protease inhibitor-resistant variant through a recombination event involving the original MDR virus. MDR infections in two other untreated PHI patients yielded viremia levels typical of the untreated WT group. A fourth patient's MDR infection yielded low viremia (<50 to 500 copies/ml) for 5 years despite his having phenotypic resistance to all antiretroviral drugs in his treatment regimen. In two of these PHI cases, a rebound to higher levels of plasma viremia only occurred when the M184V mutation in reverse transcriptase could no longer be detected and, in a third case, nondetection of M184V was associated with an inability to isolate virus. To further evaluate the fitness of MDR variants acquired in PHI, MDR and corresponding WT viruses were isolated from index and source partners, respectively. Although MDR viral infectivity (50% tissue culture infective dose) was comparable to that observed for WT viruses, MDR infections in each case demonstrated 2-fold and 13- to 23-fold reductions in p24 antigen and reverse transcriptase enzymatic activity, respectively. In dual-infection competition assays, MDR viruses consistently demonstrated a marked replicative disadvantage compared with WT virus. These results indicate that MDR viruses that are generated following PHI can establish persistent infections as dominant quasispecies despite their impaired replicative competence.

FIG. 1.

Natural history of primary MDR infections. Plasma viremia and CD4 cell counts were monitored in untreated patients 1, 2, and 3 in comparison with average values from an untreated PHI cohort harboring WT infections (n = 20; mean values ± standard errors of the means [s.e.m.] are shown). Viremia in PHI patient 4 (see Table 1) over time is also depicted, since he harbored phenotypic resistance to his treatment ARVs, including ZDV, 3TC, IDV, NFV, and EFV. Viremia in untreated PHI patient 5, in relation to his M184V infection, is also presented for comparative purposes.

FIG. 2.

Effects of mixed MDR and WT populations on HIV-1 replicative capacity. PHA-stimulated CBMCs were coinfected with various ratios of homologous MDR and WT viral species from case 1. New rounds of infections were initiated by the weekly addition of fresh CBMCs. Proviral DNA was sequenced to determine the presence of MDR or WT virus (Table 4). Viral replicative capacity was ascertained by weekly determination of p24 antigen and RT activity in cell-free supernatants prior to addition of fresh CBMCs. (A) RT activity over time in different coinfections. In the infections with MDR/WT ratios of 94:6 and 98:2, NVP and 3TC drug pressure was reintroduced after WT virus was observed to predominate. (B) The levels of p24 antigen, expressed as percentages of those with the pure WT infection, are compared with those in pure MDR infections. In the case of infections in which MDR species represented less than 85% of the inocula, levels of p24 antigen paralleled those determined for the WT infection, as shown for the experiment with an MDR/WT ratio of 85:15.