The path to find an HIV vaccine

Gay and Bisexual Men's Perceptions about a Potential HIV Vaccine within a Post-COVID-19 Era: A Qualitative Study

To end the HIV epidemic, there is need for targeted strategies to reduce HIV incidence for those most vulnerable, including an HIV vaccine. This study seeks to understand the perceptions that non-PrEP using gay and bisexual men and other men who have sex with men (GBMSM) have about a potential HIV vaccine, while contextualizing their perspectives within the context of heightened vaccine hesitancy that has emerged since the COVID-19 pandemic. Between March and May of 2022, GBMSM (N = 20) participated in in-depth interviews, which assessed their perceptions about an HIV vaccine. Interviews were analysed using a codebook approach to thematic analysis. We oversampled for those unvaccinated against COVID-19 as a proxy for vaccine hesitation. Participants expressed a range of enthusiastic support, cautious optimism and skepticism when presented with the possibility of an HIV vaccine. Factors that drove willingness to receive an HIV vaccine included community-oriented altruism, individualized risk-benefit assessment, and/or the perception that a vaccine could provide a beneficial shift in sexual experiences. Participants also expressed hesitations about receiving an HIV vaccine, including concerns about potential side-effects and efficacy, as well as mistrust in the vaccine development process. Notably, participants often evaluated the vaccine in comparison to PrEP and condoms. Participants offered specific insights into information they would like to receive about an HIV and where/how they would like to receive it. Our findings can help inform future HIV vaccine implementation efforts by offering insights into the factors that motivate and deter GBMSM to receive an HIV vaccine.

HIV Latency and Nanomedicine Strategies for Anti-HIV Treatment and Eradication

Antiretrovirals (ARVs) reduce Human Immunodeficiency Virus (HIV) loads to undetectable levels in infected patients. However, HIV can persist throughout the body in cellular reservoirs partly due to the inability of some ARVs to cross anatomical barriers and the capacity of HIV-1 to establish latent infection in resting CD4⁺ T cells and monocytes/macrophages. A cure for HIV is not likely unless latency is addressed and delivery of ARVs to cellular reservoir sites is improved. Nanomedicine has been used in ARV formulations to improve delivery and efficacy. More specifically, researchers are exploring the benefit of using nanoparticles to improve ARVs and nanomedicine in HIV eradication strategies such as shock and kill, block and lock, and others. This review will focus on mechanisms of HIV-1 latency and nanomedicine-based approaches to treat HIV.

Impact of adjuvants on the biophysical and functional characteristics of HIV vaccine-elicited antibodies in humans

Adjuvants can alter the magnitude, characteristics, and persistence of the humoral response to protein vaccination. HIV vaccination might benefit from tailored adjuvant choice as raising a durable and protective response to vaccination has been exceptionally challenging. Analysis of trials of partially effective HIV vaccines have identified features of the immune response that correlate with decreased risk, including high titers of V1V2-binding IgG and IgG3 responses with low titers of V1V2-binding IgA responses and enhanced Fc effector functions, notably antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP). However, there has been limited opportunity to compare the effect of different adjuvants on these activities in humans. Here, samples from the AVEG015 study, a phase 1 trial in which participants (n = 112) were immunized with gp120SF-2 and one of six different adjuvants or combinations thereof were assessed for antibody titer, biophysical features, and diverse effector functions. Three adjuvants, MF59 + MTP-PE, SAF/2, and SAF/2 + MDP, increased the peak magnitude and durability of antigen-specific IgG3, IgA, FcγR-binding responses and ADCP activity, as compared to alum. While multiple adjuvants increased the titer of IgG, IgG3, and IgA responses, none consistently altered the balance of IgG to IgA or IgG3 to IgA. Linear regression analysis identified biophysical features including gp120-specific IgG and FcγR-binding responses that could predict functional activity, and network analysis identified coordinated aspects of the humoral response. These analyses reveal the ability of adjuvants to drive the character and function of the humoral response despite limitations of small sample size and immune variability in this human clinical trial.

Antibody-dependent cellular cytotoxicity (ADCC) responses along with ADCC susceptibility influence HIV-1 mother to child transmission

BACKGROUND

HIV-1 vaccine efforts are primarily directed towards eliciting neutralizing antibodies (nAbs). However, vaccine trials and mother to child natural history cohort investigations indicate that antibody-dependent cellular cytotoxicity (ADCC), not nAbs, correlate with prevention. The ADCC characteristics associated with lack of HIV-1 acquisition remain unclear.

METHODS

Here we examine ADCC and nAb properties in pre-transmission plasma from HIV-1 exposed infants and from the corresponding transmitting and non-transmitting mothers' breast milk and plasma. Breadth and potency (BP) is assessed against a panel of heterologous, non-maternal, variants. ADCC and neutralization sensitivity is estimated for the strains present in the infected mothers.

RESULTS

Infants that eventually acquire HIV-1 and those that remain uninfected have similar pre-transmission ADCC BP. The viruses circulating in the transmitting and the non-transmitting mothers also have similar ADCC susceptibility. Infants with a combination of higher pre-transmission ADCC BP and exposure to more ADCC susceptible strains are less likely to acquire HIV-1. In contrast, higher pre-existing infant neutralization BP and greater maternal virus neutralization sensitivity does not associate with transmission. Infants have higher ADCC BP closer to birth and in the presence of high plasma IgG relative to IgA levels. Mothers with potent humoral responses against their autologous viruses harbor more ADCC sensitive strains.

CONCLUSION

ADCC sensitivity of the exposure variants along with preexisting ADCC BP influence mother to child HIV-1 transmission during breastfeeding. Vaccination strategies that enhance ADCC responses are likely not sufficient to prevent HIV-1 transmission because strains present in chronically infected individuals can have low ADCC susceptibility.

TRIAL REGISTRATION

NCT00164736 for BAN study.