Comparative Immunovirological and Clinical Responses to Antiretroviral Therapy Between HIV-1 Group O and HIV-1 Group M Infected Patients

BACKGROUND

Little is known about impact of genetic divergence of human immunodeficiency virus type 1 group O (HIV-1/O) relative to HIV-1 group M (HIV-1/M) on therapeutic outcomes. We aimed to determine if responses to standardized combination antiretroviral therapy (cART) were similar between groups despite strain divergence.

METHODS

We performed an open nonrandomized study comparing the immunological, virological, and clinical responses to cART based on 2 nucleoside reverse transcriptase inhibitors plus 1 ritonavir-boosted protease inhibitor, in naive and paired HIV-1/O vs HIV-1/M infected (+) patients (ratio 1:2), matched on several criteria. The primary endpoint was the proportion of patients with undetectable plasma viral load (pVL, threshold 60 copies/mL) at week (W) 48. Secondary endpoints were the proportion of patients with undetectable pVL at W24 and W96 and CD4 evolution between baseline and W24, W48, and W96.

RESULTS

Forty-seven HIV-1/O+ and 94 HIV-1/M+ patients were included. Mean pVL at baseline was significantly lower by 1 log for HIV-1/O+ vs HIV-1/M+ patients. At W48, no significant difference was observed between populations with undetectable pVL and differences at W24 and W96 were not significant. A difference in CD4 gain was observed in favor of HIV-1/M at W48 and W96, but this was not significant when adjusted on both matched criteria and pVL at baseline.

CONCLUSIONS

Our data demonstrate similar immunovirological and clinical response between HIV-1/O+ and HIV-1/M+ patients. They also reveal significantly lower baseline replication for HIV-1/O variants, suggesting specific virological properties and physiopathology that now need to be addressed.

CLINICAL TRIALS REGISTRATION

NCT00658346.

Severe underquantification of HIV-1 group O isolates by major commercial PCR-based assays

HIV-1 diversity poses major challenges to viral load assays because genetic polymorphisms can impede nucleic acid detection. In addition to the on-going viral diversification within the HIV-1 group M pandemic, HIV-1 genetic diversity is further increased by non-group M infections, such as HIV-1 groups O (HIV-1-O), N and P. We here conducted a systematic evaluation of commercially available PCR assays to detect HIV-1-O isolates. We collected 25 primary HIV-1-O isolates covering all genetic clusters within HIV-1-O. Subsequently, this panel of isolates was tested on eight commercially available quantitative and five qualitative HIV-1 PCR-based assays in serial dilutions. Sequence analyses were performed for severe cases of underquantification or lack of detection. We observed differences between the assays in quantification that depended on the HIV-1-O isolate's subgroup. All three tested HIV-1-O subgroup IV isolates were underquantified by the Roche CAP/CTM >800-fold compared to the Abbott RealTime assay. In contrast, the latter assay underquantified several subgroup I isolates >200-fold. Notably, the Xpert HIV-1 Viral Load test from Cepheid failed to detect two of the HIV-1-O isolates, whereas the Roche Cobas 8800 assay readily detected all isolates. Comparative sequence analyses identified polymorphisms in the HIV-1-O long-terminal repeat and integrase genes that likely underlie inadequate nucleic acid amplification. Potential viral load underquantification should be considered in therapeutic monitoring of HIV-1-O-infected patients. Pre-clinical assessments of HIV-1 diagnostic assays could be harmonized by establishing improved and internationally standardized panels of HIV-1 isolates that cover the dynamic diversity of circulating HIV-1 strains.

Efficient Vpu-Mediated Tetherin Antagonism by an HIV-1 Group O Strain

Simian immunodeficiency viruses (SIVs) use their Nef proteins to counteract the restriction factor tetherin. However, a deletion in human tetherin prevents antagonism by the Nef proteins of SIVcpz and SIVgor, which represent the ape precursors of human immunodeficiency virus type 1 (HIV-1). To promote virus release from infected cells, pandemic HIV-1 group M strains evolved Vpu as a tetherin antagonist, while the Nef protein of less widespread HIV-1 group O strains acquired the ability to target a region adjacent to this deletion. In this study, we identified an unusual HIV-1 group O strain (RBF206) that evolved Vpu as an effective antagonist of human tetherin. While both RBF206 Vpu and Nef exert anti-tetherin activity in transient-transfection assays, mainly Vpu promotes RBF206 release in infected CD4+ T cells. Although mutations distinct from the adaptive changes observed in group M Vpus (M-Vpus) were critical for the acquisition of its anti-tetherin activity, RBF206 O-Vpu potently suppresses NF-κB activation and reduces CD4 cell surface expression. Interestingly, RBF206 Vpu counteracts tetherin in a largely species-independent manner, degrading both the long and short isoforms of human tetherin. Downmodulation of CD4, but not counteraction of tetherin, by RBF206 Vpu was dependent on the cellular ubiquitin ligase machinery. Our data present the first example of an HIV-1 group O Vpu that efficiently antagonizes human tetherin and suggest that counteraction by O-Nefs may be suboptimal.IMPORTANCE Previous studies showed that HIV-1 groups M and O evolved two alternative strategies to counteract the human ortholog of the restriction factor tetherin. While HIV-1 group M switched from Nef to Vpu due to a deletion in the cytoplasmic domain of human tetherin, HIV-1 group O, which lacks Vpu-mediated anti-tetherin activity, acquired a Nef protein that is able to target a region adjacent to the deletion. Here we report an unusual exception, identifying a strain of HIV-1 group O (RBF206) whose Vpu protein evolved an effective antagonism of human tetherin. Interestingly, the adaptive changes in RBF206 Vpu are distinct from those found in M-Vpus and mediate efficient counteraction of both the long and short isoforms of this restriction factor. Our results further illustrate the enormous flexibility of HIV-1 in counteracting human defense mechanisms.

HIV-1 group O infection in Cameroon from 2006 to 2013: Prevalence, genetic diversity, evolution and public health challenges

The human immunodeficiency virus, HIV, is characterized by a tremendously high genetic diversity, leading to the currently known circulating HIV types, groups, subtypes, and recombinant forms. HIV-1 group O is one of the most diverse forms of HIV-1 and has been so far related to Cameroon or individuals originating from Cameroon. In this study, we investigated in Cameroon, the evolution of this viral group from 2006 to 2013, in terms of prevalence, genetic diversity and public health implications. Our results confirmed the predominance of HIV-1 group M (98.5%), a very low prevalence (<0.02%) for HIV-1 group N and P, and HIV-2 in this country. HIV-1 group O was found at around 0.6% (95% confidence interval: 0.4-0.8%), indicating that the frequency of this virus in Cameroon has remained stable over the last decades. However, we found an extensive high genetic diversity within this HIV-1 group, that resulted from previous steady increase on the effective number of HIV-1 group O infections through time, and the current distribution of the circulating viral strains still does not allow classification as subtypes. The frequency of dual infections with HIV-1 group M and group O was 0.8% (95% confidence interval: 0.6-1.0%), but we found no recombinant forms in co-infected patients. Natural resistance to integrase inhibitors was not identified, although we found several mutations considered as natural polymorphisms. Our study shows that infections with HIV-1 group O can be adequately managed in countries where the virus circulates, but this complex virus still represents a challenge for diagnostics and monitoring strategies.