Doctor of Philosophy, Jawharlal Nehru Centre for Advanced Sci Research (2016)
Master of Technology, Vellore Institute Technology (2010)
Bachelor of Technology, Anna University (2007)
Emerging concepts in the science of vaccine adjuvants.
Nature reviews. Drug discovery
Adjuvants are vaccine components that enhance the magnitude, breadth and durability of the immune response. Following its introduction in the 1920s, alum remained the only adjuvant licensed for human use for the next 70 years. Since the 1990s, a further five adjuvants have been included in licensed vaccines, but the molecular mechanisms by which these adjuvants work remain only partially understood. However, a revolution in our understanding of the activation of the innate immune system through pattern recognition receptors (PRRs) is improving the mechanistic understanding of adjuvants, and recent conceptual advances highlight the notion that tissue damage, different forms of cell death, and metabolic and nutrient sensors can all modulate the innate immune system to activate adaptive immunity. Furthermore, recent advances in the use of systems biology to probe the molecular networks driving immune response to vaccines ('systems vaccinology') are revealing mechanistic insights and providing a new paradigm for the vaccine discovery and development process. Here, we review the 'known knowns' and 'known unknowns' of adjuvants, discuss these emerging concepts and highlight how our expanding knowledge about innate immunity and systems vaccinology are revitalizing the science and development of novel adjuvants for use in vaccines against COVID-19 and future pandemics.
View details for DOI 10.1038/s41573-021-00163-y
View details for PubMedID 33824489
Systems biological assessment of immunity to mild versus severe COVID-19 infection in humans.
Science (New York, N.Y.)
COVID-19 represents a global crisis, yet major knowledge gaps remain about human immunity to SARS-CoV-2. We analyzed immune responses in 76 COVID-19 patients and 69 healthy individuals from Hong Kong and Atlanta. In PBMCs of COVID-19 patients, there was reduced expression of HLA-DR and pro-inflammatory cytokines by myeloid cells, and impaired mTOR-signaling and IFN-alpha production by plasmacytoid DCs. In contrast, there were enhanced plasma levels of inflammatory mediators, including EN-RAGE, TNFSF14, and oncostatin-M, which correlated with disease severity and increased bacterial products in human plasma. Single-cell transcriptomics revealed no type-I IFN, reduced HLA-DR in myeloid cells of severe patients, and transient expression of IFN-stimulated genes. This was consistent with bulk PBMC transcriptomics, and transient, low plasma IFN-alpha levels during infection. These results reveal mechanisms and potential therapeutic targets for COVID-19.
View details for DOI 10.1126/science.abc6261
View details for PubMedID 32788292
T cell-inducing vaccine durably prevents mucosal SHIV infection even with lower neutralizing antibody titers.
Recent efforts toward an HIV vaccine focus on inducing broadly neutralizing antibodies, but eliciting both neutralizing antibodies (nAbs) and cellular responses may be superior. Here, we immunized macaques with an HIV envelope trimer, either alone to induce nAbs, or together with a heterologous viral vector regimen to elicit nAbs and cellular immunity, including CD8+ tissue-resident memory T cells. After ten vaginal challenges with autologous virus, protection was observed in both vaccine groups at 53.3% and 66.7%, respectively. A nAb titer >300 was generally associated with protection but in the heterologous viral vector + nAb group, titers <300 were sufficient. In this group, protection was durable as the animals resisted six more challenges 5 months later. Antigen stimulation of T cells in ex vivo vaginal tissue cultures triggered antiviral responses in myeloid and CD4+ T cells. We propose that cellular immune responses reduce the threshold of nAbs required to confer superior and durable protection.
View details for DOI 10.1038/s41591-020-0858-8
View details for PubMedID 32393800
Toll-Like Receptor 9 Activation Rescues Impaired Antibody Response in Needle-free Intradermal DNA Vaccination
The delivery of plasmid DNA to the skin can target distinct subsets of dermal dendritic cells to confer a superior immune response. The needle-free immunization technology offers a reliable, safe and efficient means to administer intradermal (ID) injections. We report here that the ID injection of DNA vectors using an NF device (NF-ID) elicits a superior cell-mediated immune response, at much lesser DNA dosage, comparable in magnitude to the traditional intramuscular immunization. However, the humoral response is significantly impaired, possibly at the stage of B cell isotype switching. We found that the NF-ID administration deposits the DNA primarily on the epidermis resulting in a rapid loss of the DNA as well as the synthesized antigen due to the faster regeneration rate of the skin layers. Therefore, despite the immune-rich nature of the skin, the NF-ID immunization of DNA vectors may be limited by the impaired humoral response. Additional booster injections are required to augment the antibody response. As an alternative and a viable solution, we rescued the IgG response by coadministration of a Toll-like receptor 9 agonist, among other adjuvants examined. Our work has important implication for the optimization of the emerging needle-free technology for ID immunization.
View details for DOI 10.1038/srep33564
View details for Web of Science ID 000383946000001
View details for PubMedID 27658623
View details for PubMedCentralID PMC5034244