Caractérisation virologique des variants de VIH circulant au Cameroun : diversité génétique et résistance aux antirétroviraux

Abstract

Due to its broad diversity, human Immunodéficient Virus (HIV) remains a major public health problem in the world. The dynamism of this virus in Cameroon involves many challenges on diagnosis, follow-up and treatment in this country where the therapeutic options are limited. To target the ONUAIDS 90/90/90 objectives for 2020, it is important to observe and analyse the evolution of these different strains circulating in Cameroon. This is why we described the distribution of different strains of HIV circulating in Cameroon and the resistance profile of these strains to antiretroviral treatment (ART). Two groups of samples were used. The first consisted of plasma samples of patients who ich requested serological diagnosis of HIV between January 2010 and December 2016 or HIV genotyping resistance test between September 2013 and December 2016 on CPC. The second constituted all HIV positive blood collected in the framework of the Demographic Health Survey (DHS) of 2011 in Cameroon. The in-house serotyping test was performed to separate the different serotype of HIV (M, N, O, P, M+O and VIH-2). All the HIV non-M groups and doubles infections observed, were characterized by molecular test on the polymerase (pol) and envelope (env) genes to confirm the serological status. The discordance between pol and env genes, which favour the presence of recombinant forms were also analysed. The HIV genotypic resistance tests were done on pol region (Prot and RT) and only the specimen with positive amplification on these two regions were sequenced and analyzed for drug-resistant mutations using the French National Agency for research on HIV/AIDS and viral hepatitis algorithm. Out of the 83253 patients routinely received at the CPC for HIV diagnosis between 2010 and 2016, 24448 (29.4%) were found to be infected. The serotyping test revealed that 24079 (98.5%) were mono-reactive M, 119 (0.5%) mono-reactive O, 1 (0.004%) mono-reactive N, 9 (0.04%) mono-reactive VIH-2, 70 (0.3%) doubles-reactive M+O and 171 (0.7%) indeterminate serotypes. Over time, analyses showed significant decrease in the number of HIV positive samples from 53.2% in 2010 to 15.5% in 2016 (p=0.001). In the same order, we also observed a significant increase in the number of HIV-1/M+O double-activity (p-0.001) (from 0.08% in 2010 to 2.11% in 2016). One double HIV infection M+O was confirmed in one patient with the molecular test, and the presence of recombinant M/O was also observed. Of the 295 HIV-infected patients registered with the CPC for the ARV resistance test, 203 (68.8%) were of therapeutic failure. All these patients were infected with non B HIV subtype (CRF02_AG, 71%) and more than half of patients (70.2%) were on first-line ART with 3TC + TDF + EFV. On pol gene, the predominant mutations were M184V/I at 75.3% (222/295) and K103S/N/R at 47.8% (141/295) respectively in NRTI and NNRTI. No insertion on codon 69 was observed. Resistante to Lamivudine was commonly observed (75.3%) following by Nevirapine (76.6%). Concerning protease Inhibitors (PI) globally, lower resistance was observed (less than 10% of resistance by drugs). With time, significant increase in the number of patients on TDF was observed (51.2% in 2014, to 77% in 2016) (p=0.02). Similarly, an important increase in virus resistance to TDF on patients in first line only was also observed with rates of 3% and 25% in 2014 and 2016 respectively (p=0.02). Concerning 673 dried blood spot confirmed to be infected by HIV during DHS-2011, 646 were mono-reactive M, 4 mono-reactive O and 23 indeterminate serotypes. HIV-1/M was the predominant strains observed in all the regions of our country, and the four H subtype of HIV-1/O observed were identified in north, Adamawa and Centre of Cameroon. Among the 673 dried blood spot analyzed for HIV genotyping resistance test, 294 were sequenced, with 160 (54.4%) on both regions (Prot and RT), and 25 (8.5%) and 18 (6.1%) respectively on Protease and reverse transcriptase regions only. Globally lower resistance was perceived in this population. The common mutations detected in reverse-transcriptase region were M184V (5.6%) following by T215Y (5%). The current resistances present in this region were the resistance to Rilpivirine at 8.1%. As concerned protease region, the common mutations identified were M36I, H69K and L89M (97.5%, 96.3% and 95% respectively), and the predominant resistance was resistance to Saquinavir (8.1%).To conclude, our results confirm the circulation of different strains of HIV in Cameroon with the predominance of HIV-1/M, the presence of HIV-1/O, and a very low flow of HIV-1/N. However we note a significant decrease in the number of patients infected by HIV over time and a significant increase in probable double infections of HIV-1/M + O. We also observed the likelihood of emergence of resistance to the TDF. These data highlight the need to strengthen the monitoring of HIV strains in order to improve the diagnosis and follow-up of infected patients in Cameroon and predict possible treatment failure, mainly in resource-limited settings where the therapeutics options are limited.