To our knowledge, this study is the first large multicountry study conducted in four countries in the West (n = 3) and Central (n = 1) African regions of the prevalence of the HLA-B*57:01 allele among individuals with HIV. According to the latest epidemiological data, West and Central Africa is home to 4.9 million people living with HIV. HIV prevalence among adults is 1.4%, which is relatively low compared to East and Southern Africa. In this region, the number of people accessing treatment rose significantly from 860,000 in 2010 to 2.9 million in 2019. HLA-B*57:01 is a generic marker of clinical importance used in several countries, specifically in developed countries, to decrease abacavir-related hypersensitivity reactions. Guidelines in North America and Europe recommend routine screening for HLA-B*57:01 prior to initiation of abacavir therapy [27]. Ideally, since HLA-B*57:01 varies among different populations, it is ascertaining HLA-B*57:01 prevalence before decoding or not performing systematic screening before initiating abacavir-based ART regimens. In our study, we screened HIV-positive patients on ART or not for HLA-B*57:01 carriage.
We estimated an overall HLA-B * 57:01 prevalence rate of 0.07%, ranging from 0% in Togo to 0.2% in Burkina-Faso. A similar survey was conducted in Nigeria, located in the West African region between April 2016 and April 2017 in five HIV treatment facilities. In this study, 1,504 adults were enrolled. Of these, 132 (9.1%) were HLA-B*57 positive using a nonspecific low-resolution HLA-B*5701 primer mix. On further analysis, none of the 132 samples (0%) had the HLA-B*57:01 allele [21]. Another survey was conducted in a different population and reported a high prevalence of HLA-B*57:01. This is the case in Colombia, with a prevalence rate of 2.7% in Colombian HIV-infected individuals. The prevalence was 4% for whites, 2.6% for other races, and 1.9% for Afro-Colombians [28]. Other studies have confirmed a low prevalence of HLA-B * 57:01 in the African population. In the United States, there is a lower frequency of the HLA-B*57:01 allele in African Americans, with a reported frequency between 2.3% and 4% [19, 29, 30]. Among White subjects, prevalence was 7.93%. Among black subjects, only two (both Ugandan) were HLA-B*57:01 positive, giving a rate of 0.26% [31].
Our study had a few limitations. We did not conduct an analysis based on race in our survey. Other races are indeed rare in individuals with HIV in West and central Africa, and this variable is not collected routinely in databases. Further studies should explore including race (i.e., mestizo), as in our sample, one person in Gabon with the mestizo race was screened positive. Some studies have reported that the heterogeneity of HLA B*57:01 prevalence is mostly dependent upon race and ethnicity heritage [15, 32]. Another limitation is that we did not perform logistic regression with the low prevalence observed to identify factors associated with the presence of HLA-B*57:01. Finally, HLA-B*57:01-negative patients starting abacavir-containing regimens (3%) were not followed up; therefore, the incidence of HSR was not assessed.
Since abacavir is included in the first-line regimen, the question of hypersensitivity to abacavir should be important to document. However, to our knowledge, there are no guidelines for screening patients before ART initiation in Africa. Before abacavir should be wisely used in Africa, it is necessary to explore the prevalence of HLA-B*57:01. The application of routine HLA-B*57:01 testing to other racial populations deserves further investigation. In these four countries, antiretroviral therapy is available and free of charge for patients. Currently, the first-line regimen includes 2 NRTIs and dolutegravir in accordance with the WHO guidelines or 2 NRTIs and efavirenz. An optimized NRTI backbone should be used, such as zidovudine (AZT), tenofovir or abacavir (ABC), and vice versa.
In addition, HLA-B*57:01 screening was not performed routinely because of the lack of equipment and reference laboratories specializing in immunologic tests in the four countries. This is the main reason all-immunological analyses were performed in Belgium, which is specialized in this analysis to avoid heterogenicity between the tests.
Recently, the value of HLA-B*57:01 screening prior to prescribing abacavir is a concern in areas where its prevalence is low [33, 34]. In the context of low-income countries where pharmacogenetic screening is not available and based on this result with a low prevalence of HLA-B*57:01, we could not recommend the testing of HLA-B*57:01. Despite the low prevalence of HLA-B*57:01, clinical follow-up of patients starting an abacavir-based regimen is mandatory. It is therefore important to educate the patient about the possible symptoms of a hypersensitivity reaction, especially at the beginning of treatment, so that the patient can easily identify them and return for further consultation. Any suspicion of hypersensitivity to abacavir should lead to discontinuation of treatment and the initiation of rigorous clinical follow-up [35, 36]. Screening for HLA-B*57:01 prior to initiation of any therapy with abacavir has been shown to be beneficial [37, 38].