This proof-of-concept study tested if prior BCG revaccination can qualitatively and quantitively enhance antibody and T-cell responses induced by Oxford/AstraZeneca ChAdOx1nCoV-19 or COVISHIELD (TM... Show moreThis proof-of-concept study tested if prior BCG revaccination can qualitatively and quantitively enhance antibody and T-cell responses induced by Oxford/AstraZeneca ChAdOx1nCoV-19 or COVISHIELD (TM), an efficacious and the most widely distributed vaccine in India. We compared COVISHIELD (TM) induced longitudinal immune responses in 21 BCG re-vaccinees (BCG-RV) and 13 BCG-non-revaccinees (BCG-NRV), all of whom were BCG vaccinated at birth; latent tuberculosis negative and SARS-CoV-2 seronegative prior to COVISHIELD (TM) vaccination. Compared to BCG-NRV, BCG-RV displayed significantly higher and persistent spike-specific neutralizing (n) Ab titers and polyfunctional CD4+ and CD8+ T-cells for eight months post COVISHIELD (TM) booster, including distinct CD4+IFN-gamma+ and CD4+IFN-gamma- effector memory (EM) subsets co-expressing IL-2, TNF-alpha and activation induced markers (AIM) CD154/CD137 as well as CD8+IFN-gamma+ EM,TEMRA (T cell EM expressing RA) subset combinations co-expressing TNF-alpha and AIM CD137/CD69. Additionally, elevated nAb and T-cell responses to the Delta mutant in BCG-RV highlighted greater immune response breadth. Mechanistically, these BCG adjuvant effects were associated with elevated markers of trained immunity, including higher IL-1 beta and TNF-alpha expression in CD14+HLA-DR+monocytes and changes in chromatin accessibility highlighting BCG-induced epigenetic changes. This study provides first in-depth analysis of both antibody and memory T-cell responses induced by COVISHIELD (TM) in SARS-CoV-2 seronegative young adults in India with strong evidence of a BCG-induced booster effect and therefore a rational basis to validate BCG, a low-cost and globally available vaccine, as an adjuvant to enhance heterologous adaptive immune responses to current and emerging COVID-19 vaccines. Show less
BACKGROUND. Bacille Calmette-Guerin (BCG) vaccine is protective against Tuberculosis (TB) in children, but its efficacy wanes with age. Consequently, determining if BCG revaccination augments anti... Show moreBACKGROUND. Bacille Calmette-Guerin (BCG) vaccine is protective against Tuberculosis (TB) in children, but its efficacy wanes with age. Consequently, determining if BCG revaccination augments anti-TB immunity in young adults in TB endemic regions is vital.METHODS. Two hundred healthy adults, BCG vaccinated at birth, were tested for their IFN-gamma release assay (IGRA) status. Of these, 28 IGRA(+) and 30 IGRA(-) were BCG revaccinated, and 24 IGRA(+) and 23 IGRA(-) subjects served as unvaccinated controls. T and innate cell responses to mycobacterial antigens were analyzed by 14-color flow cytometry over 34 weeks.RESULTS. IFN-gamma and/or IL-2 Ag85A- and BCG-specific CD4(+) and CD8(+) T cell responses were boosted by revacciantion at 4 and 34 weeks, respectively, and were > 2-fold higher in IGRA(+) compared with IGRA- vaccinees. Polyfunctional Ag85A, BCG, and mycobacterium tuberculosis (Mtb) latency Ag-specific (LTAg-specific) CD4(+) T cells expressing up to 8 cytokines were also significantly enhanced in both IGRA+ and IGRA- vaccinees relative to unvaccinated controls, most markedly in IGRA(+) vaccinees. A focused analysis of Th17 responses revealed expansion of Ag85A-, BCG-, and LTAg-specific total IL-17A(+),IL-17F(+),IL-22(+), and IL-10(+) CD4(+) T cell effectors in both IGRA(+) and IGRA- subjects. Also, innate IFN-gamma(+) NK/gamma delta/NKT cell responses were higher in both IGRA(+) and IGRA- vaccinees compared with controls. This is the first evidence to our knowledge that BCG revaccination significantly boosts antimycobacterial Th1/Th17 responses in IGRA(+) and IGRA- subjects.CONCLUSION. These data show that BCG revaccination is immunogenic in IGRA- and IGRA(+) subjects, implying that Mtb preinfection in IGRA(+) subjects does not impact immunogenicity. This has implications for public health and vaccine development strategies. Show less
