Can an immune-regulatory vaccine prevent HIV infection?

Targeted Immuno-Antiretroviral to Promote Dual Protection against HIV: A Proof-of-Concept Study

The C-C motif chemokine receptor-5 (CCR5) expression on the T-cell surface is the prime barrier to HIV/AIDS eradication, as it promotes both active human immunodeficiency virus (HIV)-infection and latency; however, antiretrovirals (ARVs) suppress plasma viral loads to non-detectable levels. Keeping this in mind, we strategically designed a targeted ARVs-loaded nanoformulation that targets CCR5 expressing T-cells (e.g., CD4+ cells). Conceptually, CCR5-blocking and targeted ARV delivery would be a dual protection strategy to prevent HIV infection. For targeting CCR5+ T-cells, the nanoformulation was surface conjugated with anti-CCR5 monoclonal antibodies (CCR5 mAb) and loaded with dolutegravir+tenofovir alafenamide (D+T) ARVs to block HIV replication. The result demonstrated that the targeted-ARV nanoparticle's multimeric CCR5 binding property improved its antigen-binding affinity, prolonged receptor binding, and ARV intracellular retention. Further, nanoformulation demonstrated high binding affinity to CCR5 expressing CD4+ cells, monocytes, and other CCR5+ T-cells. Finally, the short-term pre-exposure prophylaxis study demonstrated that prolonged CCR5 blockage and ARV presence further induced a "protective immune phenotype" with a boosted T-helper (Th), temporary memory (TM), and effector (E) sub-population. The proof-of-concept study that the targeted-ARV nanoformulation dual-action mechanism could provide a multifactorial solution toward achieving HIV "functional cure."

Assessment of the population coverage of an HIV-1 vaccine targeting sequences surrounding the viral protease cleavage sites in Gag, Pol, or all 12 protease cleavage sites

Development of an effective HIV-1 vaccine has been a great challenge faced by the research community. Recently a novel strategy targeting the viral protease cleavage sites (PCSs) has been tested and shown promising results. This T cell-based vaccine strategy depends on individuals expressing certain HLA class I molecules and since each population has unique distributions of HLA class I alleles, population coverage analysis is required to assess feasibility. Utilizing the validated CD8 T cell epitope data from previous studies we conducted coverage analysis of an HIV-1 vaccine targeting the sequences surrounding all 12-PCSs, Gag-PCSs, and Pol-PCSs. The population coverage, average epitope hit, and minimum number of epitopes recognized by 90% of the population (PC90) was compiled for 66 countries and 16 geographical regions using the web tool provided by "Immune Epitope Database and Analysis Resource". Our analysis shows that the coverage for an HIV-1 vaccine targeting sequences surrounding all 12 PCSs, 5 PCSs in Gag or 6 PCSs in Pol can cover ~ 70% to ~ 100% of the populations analyzed. There was no statistical difference in population coverages for the majority of populations examined when comparing the CD8 T cell epitope sets (12-PCSs, Gag-PCSs, and Pol-PCSs). As expected, vaccines targeting more sequences will have more CD8 T cell epitopes, as the mean average epitope hit for the 12-PCSs, Gag-PCSs, and Pol-PCSs across all countries studied was 9.45, 4.76, and 4.74, respectively, and across all geographical regions was 9.76, 4.99, and 4.92, respectively. The average PC90 for the 12-PCSs, Gag-PCSs, and Pol-PCSs across all countries studied was 2.53, 1.31, and 1.41, respectively, and across all geographical regions was 2.24, 1.23, and 1.29, respectively. Thus, vaccines targeting sequences surrounding the HIV-1 PCSs can cover broad populations; however, whether targeting a subset of the PCSs is sufficient to prevent acquisition requires further preclinical investigation.

Vaccine targeting SIVmac251 protease cleavage sites protects macaques against vaginal infection

After over 3 decades of research, an effective anti-HIV vaccine remains elusive. The recently halted HVTN702 clinical trial not only further stresses the challenge to develop an effective HIV vaccine but also emphasizes that unconventional and novel vaccine strategies are urgently needed. Here, we report that a vaccine focusing the immune response on the sequences surrounding the 12 viral protease cleavage sites (PCSs) provided greater than 80% protection to Mauritian cynomolgus macaques against repeated intravaginal SIVmac251 challenges. The PCS-specific T cell responses correlated with vaccine efficacy. The PCS vaccine did not induce immune activation or inflammation known to be associated with increased susceptibility to HIV infection. Machine learning analyses revealed that the immune microenvironment generated by the PCS vaccine was predictive of vaccine efficacy. Our study demonstrates, for the first time to our knowledge, that a vaccine which targets only viral maturation, but lacks full-length Env and Gag immunogens, can prevent intravaginal infection in a stringent macaque/SIV challenge model. Targeting HIV maturation thus offers a potentially novel approach to developing an effective HIV vaccine.

Viral vaccines and their manufacturing cell substrates: New trends and designs in modern vaccinology

Vaccination is one of the most effective interventions in global health. The worldwide vaccination programs significantly reduced the number of deaths caused by infectious agents. A successful example was the eradication of smallpox in 1979 after two centuries of vaccination campaigns. Since the first variolation administrations until today, the knowledge on immunology has increased substantially. This knowledge combined with the introduction of cell culture and DNA recombinant technologies revolutionized vaccine design. This review will focus on vaccines against human viral pathogens, recent developments on vaccine design and cell substrates used for their manufacture. While the production of attenuated and inactivated vaccines requires the use of the respective permissible cell substrates, the production of recombinant antigens, virus‐like particles, vectored vaccines and chimeric vaccines requires the use – and often the development – of specific cell lines. Indeed, the development of novel modern viral vaccine designs combined with, the stringent safety requirements for manufacture, and the better understanding on animal cell metabolism and physiology are increasing the awareness on the importance of cell line development and engineering areas. A new era of modern vaccinology is arriving, offering an extensive toolbox to materialize novel and creative ideas in vaccine design and its manufacture.