Sub-Saharan Africa is disproportionally affected with HIV/AIDS, with close to 70% of the global epidemic and the highest burden of pediatric HIV infections; about 9 out of every 10 children living with HIV is found in the Sub-Saharan African region [1,2]. Due to combination antiretroviral therapy (ART) benefits, adolescents and young people represent a growing share of people living with HIV worldwide. In 2019, about 1.7 million adolescents between the ages of 10 and 19 years were living with HIV worldwide, representing about 5% of all people living with HIV; about 1.5 million or 88% of HIV-infected adolescents live in Sub-Saharan Africa. In 2019 alone, 460,000 young people between the ages of 10 and 24 years were newly infected with HIV, of whom 170,000 were adolescents. Of the estimated 690,000 people who died of AIDS-related illnesses in 2019, 110,000 (or approximately 16%) of them were children younger than 20 years, including 32,000 aged 10-19 years [2,3].

With the advent and scalability of ART, there is a global decrease in AIDS-related deaths. As of June 2021, 28.2 million [3] people were accessing ART, representing 73% of all people living with HIV. However, only 54% of the children living with HIV were receiving ART. Interestingly, about 94% of all the children receiving ART are from Sub-Saharan Africa [4]. In this context of continuous new HIV pediatric infections and increasing coverage in pediatric ART, the number of children living with HIV will increase, suggesting a higher likelihood of reaching adolescent age and even adulthood if treatment regimens remain fully effective in controlling HIV infections [3,4]. Adolescents living with HIV (ADLHIV) therefore constitute an HIV population with growing health concerns and with very limited findings for generalizable best practices specific to this target population, especially in Sub-Saharan Africa.

Cameroon still faces a generalized HIV epidemiology (2.7% prevalence) [5], with higher prevalence among pregnant women (5.7%) and HIV-exposed infants/children (5.8% positivity at first polymerase chain reaction [PCR] and 15% at the end of the prevention of mother-to-child HIV transmission cascade) [6]. As of December 2020, the national coverage of ART was 74% (or 367,871 HIV positive), which includes 12,017 children (35% coverage) younger than 15 years [6]. Regarding response to ART in Cameroon, an overall rate of 79.4% viral suppression was reported, with significant disparities across age ranges: 81.1% in adults, 75.6% in children, and only 53.3% in adolescents aged 10-19 years [7]. Similar to that reported by the Joint United Nations Programme on HIV/AIDS, ADLHIV represent the most vulnerable and underserved population in response to the epidemic [1,5]. For a safer growth toward adulthood, there is need to prioritize this population for the quest of innovative treatment strategies that ensure their well-being and their contribution to the development of Sub-Saharan Africa.

Despite the unquestioned benefits of ART, there are limitations with current treatment strategies. Of note, the lifelong nature of current ART goes with challenge-related adherence for most patients, ART-attributed toxicities and persisting immune dysfunction in patients lead to significant health impairments, and HIV drug resistance is increasing, mostly in Sub-Saharan African countries where most ART-experienced patients are living [8]. There is a threat of an emerging new HIV epidemic, driven by HIV drug resistance to existing antiretrovirals. These challenges are particularly true for pediatric populations due to limited ART options, poor drug formulations, and increasing events of nonadherence as they grow toward adolescence. These challenges call for approaches toward HIV (functional) cure or remission, especially for the most vulnerable populations (ie, ADLHIV) [7,9].

HIV-1 remission or eradication strategies aim to achieve durable control of the virus in the absence of ART. The development of an HIV-1 cure remains challenging due to latent reservoirs. The latter can be defined as the fraction of cells harboring transcriptionally silent proviral DNA that can produce infectious virions following activation [10]. Resting memory cluster of differentiation 4 (CD4) T cells are the primary host of the latent reservoir, but HIV-1 infection in these cells is inefficient due their low coreceptor expression and inherent restrictions to reverse transcription [11,12]. The provirus is maintained in a latent state in these cells via host factors due to integration into the expressed genes [13]. Viral rebound from the latent reservoir following ART cessation is rapid, leading to detectable viremia within weeks of therapy interruption [14]. Initiating ART early during infection is not sufficient to stop the formation of the latent reservoir, suggesting that the latent reservoir is established and disseminated early [15], even in vertically infected children who started ART soon after birth [16]. Despite years of suppressive ART, the latent reservoir is stable and is the source of rebound viremia following therapy interruption. Latently infected cells therefore represent a critical barrier to HIV-1 cure. The progress toward the development of a functional or sterilizing cure (virus remission/eradication) for HIV-1 has been significantly hindered by the presence of the latent reservoir. Therefore, understanding of where and how HIV persists in individuals on ART has transformed substantially with evidence that the virus persists in multiple cell types and tissue sites. Thus, in the frame of virological success during ART, accurate estimates of the viral reservoir would help in better mastering of viral persistence, which in turn might overcome existing barriers for achieving a complete cure [17].

Total HIV DNA is a reference biomarker that includes both integrated and unintegrated HIV DNA and reflects the global level of the viral reservoir. Buzon et al [18] reported a statistical correlation between the time from the start of the HIV infection to treatment initiation and the total HIV DNA level after 10 years of continuous treatment in a cohort of adults first treated with early infection [19]. In children, the HIV DNA level was markedly lower when viral control was achieved before the age of 1 year [18]. By comparison with other markers, total HIV DNA has the advantage of easy quantification by standardized, sensitive, real-time PCR, including digital droplet PCR [20].

Generalized immune activation is typically related to HIV-1 infection. A variety of immune cells show an increase in the expression of activation and production of proinflammatory cytokines [21,22]. Immune activation is associated with HIV-1 disease progression; suppression of viral replication with effective ART reduces immune activation, but even effective ART regimens are unable to bring it to levels seen in healthy individuals [21]. HIV-infected children, even if successfully treated with ART regimens, face a lifetime of elevated immune activation; evaluating the potential impact of this chronic immune activation and inflammation on their immune system and on disease outcome is very important [23]. Recent studies showed that immune activation and exhaustion markers are strongly associated with the reservoir size in ART-treated adults; thus, it might be anticipated that minimizing the viral reservoir with early ART might equally minimize the level of immune activation [23,24].

There is limited evidence in characterizing HIV reservoirs in the western and central African region—a geographical setting having the highest variability in circulating HIV-1 and HIV-2 strains [25,26]. For example, Cameroon, a zoonotic epicenter of HIV-1, is host to an extensively diverse landscape of HIV driven by the CRF02_AG recombinant, including most group M (sub-) subtypes, a vast array of unique recombinant forms, circulating recombinant forms, group N, group O, group P, and HIV-2 viruses [27-29]. Thus, generating baseline data on the genotypic and quantitative profile of the viral reservoir across several HIV clades in settings like Cameroon would inform the design of optimal strategies for HIV cure. Considering the aforementioned vulnerability of adolescents with vertical infection and the limited knowledge on viral reservoirs and immune activation/inflammatory reaction in this population, evidence generated from this target will be highly complementary to current global efforts. Such evidence, generated in a context of high burden of coinfections [30,31], might depict differential mechanisms of HIV persistence far from those reported in other parts of the world. 

Within the frame of the European and Developing Countries Clinical Trial Partnership-Resistance Evolution among Adolescents in Yaoundé and its surroundings (EDCTP-READY) study (Multimedia Appendix 1), we have set up a cohort of 292 vertically infected adolescents (10-19 years) receiving ART in Cameroon. In this cohort, we reported a rate of 40% undetectable viral load (<40 copies/mL) after a median of 8 years of ART, about 20% immunological failure (CD4<250 cells/mm³) rate, and less than 10% clinical failure (ie, World Health Organization stages III/IV) [32]. This population offers a unique opportunity for understanding the size and nature of the reservoir; the variability of immune response/cytokine profiling; and the effect of the viral subtype, treatment history of ART (regimen and duration), gender disparities, and adherence level on the control of the viral reservoir. To date, most HIV cure research has been restricted to high-income countries with relatively low HIV burden and has most often engaged men who have sex with men. HIV strains are genetically and biologically diverse, and host mechanisms of antiviral immunity required for durable control may differ by age, sex, geography, and ethnicity. Basic discovery research and clinical trials in resource-limited settings must be strengthened to contribute to the global cure strategy [33]. Our study aims to characterize the HIV reservoirs and their variability according to the virological and immunological profiles of vertically infected adolescents receiving ART in Cameroon and therefore improve the understanding of the viral reservoirs and provide accurate and reliable data for HIV cure research in settings harboring broad genetic diversity. In this study, we shall (1) determine HIV-1 genetic variability and drug resistance in cellular reservoirs, (2) determine the immune profile of ADLHIV, (3) quantify their HIV viral reservoir, and (4) evaluate the effect of ART and immune response on the viral reservoir profile.

We plan to conduct a cross-sectional, observational, and comparative study among vertically infected ADLHIV receiving ART in Cameroon. Participants will be selected and enrolled from an existing cohort of close to 300 vertically infected adolescents recruited for the EDCTP-READY study [7]. They will provide written assent and legal guardians will provide written proxy consent. HIV positive adolescents with incomplete ART history and hepatitis B virus/hepatitis C virus and malaria coinfections will not be considered for this study.

The minimum sample size was estimated at 90 participants, assuming an HIV prevalence of 2% in adolescents in Cameroon, a 95% confidence, and 80% statistical power. The sample size was further stratified into 3 arms of 30 participants each: arm A, HIV viral load<40 copies/mL; arm B, HIV viral load=40-999 copies/mL; and arm C, HIV viral load≥1000 copies/mL. A group of 30 HIV-negative adolescents will serve as control for immunological profiling.

This study will be conducted per the declaration of Helsinki on ethical principles for medical research involving human subjects. A written proxy-informed assent from legal guardians and a written assent from the participating HIV positive adolescent will be obtained without any coercion. Privacy and confidentiality will be ensured through the use of unique identifiers and a password-protected database accessible only by authorized staff. Participants will be free to deliberately leave the study at any time, without any effect on their routine monitoring at the study clinic. Phlebotomy will be noninvasive (venipuncture) and will be performed by a trained nurse. Ethical clearance has been obtained from the Cameroon National Ethics committee for research on human health (No2021/12/1426/CE/CNERSH/SP).

The risks to the participants are minimal since the only procedure the volunteer is subjected to, is venipuncture by a phlebotomist or physician. The venipuncture may be slightly painful, but it is practically without any risk of complication. The potential risks to subjects, none of which are likely to occur, may include momentary pain and bruising at the site or possible (but extremely unlikely) infection. If such complications arise, participants will be provided with emergency medical care.

Our study team will include a quality assurance officer who will be responsible for all the standard operating procedures for the study protocol and who will manage proficiency testing and data validation during the entire study. Quality assurance will be assessed by external proficiency testing for plasmatic viral load, CD4/CD8 count, and genotyping.