BCG revaccination boosts adaptive polyfunctional Th1/Th17 and innate effectors in IGRA+ and IGRA– Indian adults
Srabanti Rakshit, Asma Ahmed, Vasista Adiga, Bharath K. Sundararaj, Pravat Nalini Sahoo, John Kenneth, George D’Souza, Wesley Bonam, Christina Johnson, Kees L.M.C. Franken, Tom H.M. Ottenhoff, Greg Finak, Raphael Gottardo, Kenneth D. Stuart, Stephen C. De Rosa, M. Juliana McElrath, Annapurna Vyakarnam
Srabanti Rakshit, Asma Ahmed, Vasista Adiga, Bharath K. Sundararaj, Pravat Nalini Sahoo, John Kenneth, George D’Souza, Wesley Bonam, Christina Johnson, Kees L.M.C. Franken, Tom H.M. Ottenhoff, Greg Finak, Raphael Gottardo, Kenneth D. Stuart, Stephen C. De Rosa, M. Juliana McElrath, Annapurna Vyakarnam
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Clinical Research and Public Health Immunology Infectious disease

BCG revaccination boosts adaptive polyfunctional Th1/Th17 and innate effectors in IGRA+ and IGRA– Indian adults

Abstract

BACKGROUND Bacille Calmette-Guérin (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-γ 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-γ 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-γ+ NK/γδ/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.FUNDING This work was funded principally by DBT-NIH (BT/MB/Indo-US/HIPC/2013).

Authors

Srabanti Rakshit, Asma Ahmed, Vasista Adiga, Bharath K. Sundararaj, Pravat Nalini Sahoo, John Kenneth, George D’Souza, Wesley Bonam, Christina Johnson, Kees L.M.C. Franken, Tom H.M. Ottenhoff, Greg Finak, Raphael Gottardo, Kenneth D. Stuart, Stephen C. De Rosa, M. Juliana McElrath, Annapurna Vyakarnam

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Figure 4

Longitudinal analysis reveals that BCG revaccination significantly enhances Ag85A- and BCG-specific IFN-γ and/or IL-2 CD8+ T cell in whole blood.

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Longitudinal analysis reveals that BCG revaccination significantly enhan...
Left panel shows ICS data for Ag85A, and right panel shows data for BCG following in vitro stimulation of whole blood from BCG-revaccinated and control subjects. Representative flow cytometry plots show IFN-γ and/or IL-2 cytokine–positive CD8+ T cells after in vitro stimulation with either Ag85A (A) or BCG (E) at T0 and T2 (A) or T0 and T5 (E) Total frequencies of Ag85A- (B) and BCG-specific (F) IFN-γ and/or IL-2 cytokine–positive CD8+ T cells in all participants are shown after background subtraction. Line graphs show changes in frequencies of specific CD8+ T cells over time in BCG-revaccinated (Group 1 [IGRA+, red, n = 19] and Group 2 [IGRA–, blue, n = 18]) subjects and unvaccinated controls (Group 3 [IGRA+, black, n = 18] and Group 4 [IGRA–, brown, n = 18]). P values for longitudinal samples were calculated by comparing each time point with baseline using the Freidman test and corrected for multiple comparisons using Dunn’s test. Further, significant differences were determined using the Wilcoxon paired, 2-tailed t test before and after vaccination. Bonferroni adjusted P value threshold of 0.02 was considered statistically significant. Median frequencies of Ag85A (C) and BCG (G) specific IFN-γ and/or IL-2 cytokine–positive CD8+ T cells over time were compared between unvaccinated and revaccinated IGRA+ and IGRA– subjects (Group 1 versus Group 3 and Group 2 versus Group 4). Mann-Whitney U test was used to determine significant differences between groups. P < 0.05 was considered significant. Analysis of CD45RA and CD27 expression was used to determine percentage distribution of naive (CD45RA+CD27+), central memory (CM, CD45RA–CD27+), effector memory (EM, CD45RA–CD27–), and terminally differentiated T effector memory cells (TD, CD45RA+CD27–) Ag85A- (D) and BCG-specific (H) IFN-γ and/or IL-2 CD8+ T cells in BCG-revaccinated (Group 1 [IGRA+] and Group 2 [IGRA–]) subjects. Wilcoxon paired, 2-tailed t test was used to determine significant differences before and after vaccination. P < 0.05 was considered significant.