HIV Epidemic in Asia: Implications for HIV Vaccine and Other Prevention Trials

Abstract

An overall decrease of HIV prevalence is now observed in several key Asian countries due to effective prevention programs. The decrease in HIV prevalence and incidence may further improve with the scale-up of combination prevention interventions. The implementation of future prevention trials then faces important challenges. The opportunity to identify heterosexual populations at high risk such as female sex workers may rapidly wane. With unabating HIV epidemics among men who have sex with men (MSM) and transgender (TG) populations, an effective vaccine would likely be the only option to turn the epidemic. It is more likely that efficacy trials will occur among MSM and TG because their higher HIV incidence permits smaller and less costly trials. The constantly evolving patterns of HIV-1 diversity in the region suggest close monitoring of the molecular HIV epidemic in potential target populations for HIV vaccine efficacy trials. CRF01_AE remains predominant in southeast Asian countries and MSM populations in China. This relatively steady pattern is conducive to regional efficacy trials, and as efficacy warrants, to regional licensure. While vaccines inducing nonneutralizing antibodies have promise against HIV acquisition, vaccines designed to induce broadly neutralizing antibodies and cell-mediated immune responses of greater breadth and depth in the mucosal compartments should be considered for testing in MSM and TG. The rationale and design of efficacy trials of combination prevention modalities such as HIV vaccine and preexposure prophylaxis (PrEP) remain hypothetical, require high adherence to PrEP, are more costly, and present new regulatory challenges. The prioritization of prevention interventions should be driven by the HIV epidemic and decided by the country-specific health and regulatory authorities. Modeling the impact and cost-benefit may help this decision process.

Molecular epidemiology of a primarily MSM acute HIV‐1 cohort in Bangkok, Thailand and connections within networks of transmission in Asia

“…A recombinant virus can continue to recombine with other viruses, as is evident in the unique recombinant structures found in the RV254 cohort. That Thailand remains an international hub for MSM, business and tourism facilitates the introduction of non‐endemic subtypes (including South African variants of subtype C and West African variants of CRF02_AG seen in RV254) into the local population either as pure subtype strains or as recombinants .…”

Modeling HIV vaccine trials of the future

“…These issues have implications for HIV vaccine science [63–65]. Trialists must incorporate PrEP into the design and analysis, taking into account participants using PrEP at enrollment and those that may initiate or discontinue PrEP during the trial [66**].…”

Immunogenicity and efficacy of DNA/MVA HIV vaccines in rhesus macaque models

“…A vaccine should prevent new infections and control the virus replication in infected individuals to limit disease progression. There are many challenges facing the development of an HIV vaccine including an incomplete knowledge of the immunological correlates of protection, the high diversity of HIV within an infected individual (2–6% [1,2]) as well as in the population (about 15–20% within a clade; 25–35% between clades [3–5]), the ability of HIV to rapidly mutate in an infected host, and a complex glycan structure that helps protect the virus against neutralization. It is clear that overcoming these challenges for an effective HIV vaccine will require the induction of both humoral and cellular immunity against conserved viral targets.…”