Vertical transmission of multidrug-resistant Q151M human immunodeficiency virus type 1 strains

The HIV-1 Reverse Transcriptase A62V Mutation Influences Replication Fidelity and Viral Fitness in the Context of Multi-Drug-Resistant Mutations

Emergence of human immunodeficiency virus type 1 (HIV-1) drug resistance arises from mutation fixation in the viral genome during antiretroviral therapy. Primary mutations directly confer antiviral drug resistance, while secondary mutations arise that do not confer drug resistance. The A62V amino acid substitution in HIV-1 reverse transcriptase (RT) was observed to be associated with multi-drug resistance, but is not known to be a resistance-conferring mutation. In particular, A62V was observed in various multi-dideoxynucleoside resistant (MDR) mutation complexes, including the Q151M complex (i.e., A62V, V75I, F77L, F116Y, and Q151M), and the T69SSS insertion complex, which has a serine–serine insertion between amino acid positions 69 and 70 (i.e., M41L, A62V, T69SSS, K70R, and T215Y). However, what selective advantage is conferred to the virus remains unresolved. In this study, we hypothesized that A62V could influence replication fidelity and viral fitness with viruses harboring the Q151M and T69SSS MDR mutation complexes. A single-cycle replication assay and a dual-competition fitness assay were used to assess viral mutant frequency and viral fitness, respectively. A62V was found to increase the observed lower mutant frequency identified with each of the viruses harboring the MDR mutation complexes in the single-cycle assay. Furthermore, A62V was observed to improve viral fitness of replication-competent MDR viruses. Taken together, these observations indicate an adaptive role of A62V in virus replication fidelity and viral fitness, which would likely enhance virus persistence during drug-selective pressure.

Structural Insights into HIV Reverse Transcriptase Mutations Q151M and Q151M Complex That Confer Multinucleoside Drug Resistance

HIV-1 reverse transcriptase (RT) is targeted by multiple drugs. RT mutations that confer resistance to nucleoside RT inhibitors (NRTIs) emerge during clinical use. Q151M and four associated mutations, A62V, V75I, F77L, and F116Y, were detected in patients failing therapies with dideoxynucleosides (didanosine [ddI], zalcitabine [ddC]) and/or zidovudine (AZT). The cluster of the five mutations is referred to as the Q151M complex (Q151Mc), and an RT or virus containing Q151Mc exhibits resistance to multiple NRTIs. To understand the structural basis for Q151M and Q151Mc resistance, we systematically determined the crystal structures of the wild-type RT/double-stranded DNA (dsDNA)/dATP (complex I), wild-type RT/dsDNA/ddATP (complex II), Q151M RT/dsDNA/dATP (complex III), Q151Mc RT/dsDNA/dATP (complex IV), and Q151Mc RT/dsDNA/ddATP (complex V) ternary complexes. The structures revealed that the deoxyribose rings of dATP and ddATP have 3'-endo and 3'-exo conformations, respectively. The single mutation Q151M introduces conformational perturbation at the deoxynucleoside triphosphate (dNTP)-binding pocket, and the mutated pocket may exist in multiple conformations. The compensatory set of mutations in Q151Mc, particularly F116Y, restricts the side chain flexibility of M151 and helps restore the DNA polymerization efficiency of the enzyme. The altered dNTP-binding pocket in Q151Mc RT has the Q151-R72 hydrogen bond removed and has a switched conformation for the key conserved residue R72 compared to that in wild-type RT. On the basis of a modeled structure of hepatitis B virus (HBV) polymerase, the residues R72, Y116, M151, and M184 in Q151Mc HIV-1 RT are conserved in wild-type HBV polymerase as residues R41, Y89, M171, and M204, respectively; functionally, both Q151Mc HIV-1 and wild-type HBV are resistant to dideoxynucleoside analogs.

Ten years survey of primary HIV-1 resistance in Serbia: the occurrence of multiclass resistance

In Serbia, the first cases of HIV infection were reported in 1985, whereas antiretroviral (ARV) therapy has been in use since 1987. With this study we aimed to assess the occurrence and pattern of HIV resistance mutations among newly diagnosed patients in the period 2002-2011. The study prospectively included 181 adult patients. Genotypic HIV-1 drug resistance testing was performed and drug resistance was scored according to the 2009 WHO list for surveillance of drug resistance mutations (SDRMs). A bioinformatic approach was used to estimate the duration of infection by calculating the percentage of ambiguous basecalls per sequence, with a cutoff of 0.47% as the delimiter for recent infection. The overall prevalence of transmitted drug resistance (TDR) found in the study was 8.8% (16/181, 95% CI=5.5-13.8). Thirty-one percent of resistant samples contained multiple SDRMs. In particular, 5/16 patients with resistance carried viral strains with SDRMs to multiple ARV classes, hence one-third of resistant strains were multiclass resistant, including non-B strains. A total of 51.9% of samples (94/181) were classified as recent infection, with a significant increase in the second part of the study period. However, the prevalence of TDR in recent infection was 6.4% (6/94, 95% CI=2.9-13.2), not statistically different from that found in nonrecent infection. We showed a changing pattern of TDR mutations over the study period, with a substantial occurrence of multiclass resistance, across different HIV subtypes. Our results highlight the need for continued surveillance of primary resistance.

Multi-nucleoside reverse transcriptase inhibitor resistant HIV type-1 in a patient from Sierra Leone failing stavudine, lamivudine and nevirapine

We report a 33-year-old HIV type-1 (HIV-1)-infected male from Sierra Leone who harboured extensive drug resistance mutations to all nucleoside reverse transcriptase inhibitors (NRTIs) and non-NRTIs, including the multi-NRTI-resistance Q151M complex, K65R, M184I and Y181I, after using standard first-line generic fixed-dose stavudine, lamivudine and nevirapine (Triomune™) for 36 months. In the context of non-B subtypes in resource-limited countries, first-line stavudine-containing regimens have been associated with more extensive and complex mutation patterns, compared with subtype B viruses. Whether the extensive and complex NRTI resistance patterns found among African patients failing first-line antiretroviral therapy is explained by viral genetic diversity or by different patient monitoring strategies remains to be elucidated. Emerging multi-NRTI resistance in sub-Saharan Africa would not only compromise second-line treatment options and the success of antiretroviral rollout, but could also contribute to the spread of drug-resistant variants worldwide.

Postpartum antiretroviral drug resistance in HIV-1-infected women receiving pregnancy-limited antiretroviral therapy

BACKGROUND

Pregnancy-limited antiretroviral therapy (PLAT) drastically reduces HIV-1 transmission to the newborn, but may select for antiretroviral drug resistance mutations in mothers.

METHODS

We evaluated antiretroviral-naive, HIV-1-infected pregnant women who received PLAT between 1998 and 2005, and had 2-month or 6-month postpartum plasma samples available with HIV-1 RNA levels more than 500 copies/ml. Postpartum drug resistance mutation rates were assessed blindly using population sequencing and allele-specific PCR (ASPCR) of the M184V, K103N and D30N mutations. Factors associated with selection of drug resistance mutations were investigated.

RESULTS

One hundred and forty-six women were included. All women received zidovudine and lamivudine during pregnancy; 76% also received nelfinavir and 8.2% nevirapine. Resistance data were available from 114 women (78%). Postpartum rates of single-class, dual-class, and triple-class resistance were, respectively, 43, 6.1 and 0% (63.2, 10.5 and 1.7% by ASPCR). In women receiving dual or triple PLAT, respectively, postpartum M184V/I rates were 65% (95% by ASPCR) and 28.7% (51.6% by ASPCR), respectively (P < 0.01). Postpartum nonnucleoside reverse transcriptase inhibitor (NNRTI) resistance rates among women receiving nevirapine were 25% for K103N (37.5% by ASPCR) and 12.5% for Y188C. Protease inhibitor resistance rates in women receiving nelfinavir were 1.1% for D30N (1.1% by ASPCR) and 1.1% for L90M. Dual versus triple PLAT and prolonged zidovudine exposure were associated with selection of M184V. Nevirapine use and length of zidovudine and lamivudine exposure were associated with selection of K103N.

CONCLUSION

PLAT is associated with frequent selection of resistance to drugs with low-genetic barrier. Triple-drug PLAT decreases the odds for M184V selection. Routine postpartum genotypic resistance testing may be useful to guide future treatment decisions in mothers.