Microbiology & Immunology - Research Publications
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ItemCirculating TFH cells, serological memory, and tissue compartmentalization shape human influenza-specific B cell immunity(AMER ASSOC ADVANCEMENT SCIENCE, 2018-02-14)Immunization with the inactivated influenza vaccine (IIV) remains the most effective strategy to combat seasonal influenza infections. IIV activates B cells and T follicular helper (TFH) cells and thus engenders antibody-secreting cells and serum antibody titers. However, the cellular events preceding generation of protective immunity in humans are inadequately understood. We undertook an in-depth analysis of B cell and T cell immune responses to IIV in 35 healthy adults. Using recombinant hemagglutinin (rHA) probes to dissect the quantity, phenotype, and isotype of influenza-specific B cells against A/California09-H1N1, A/Switzerland-H3N2, and B/Phuket, we showed that vaccination induced a three-pronged B cell response comprising a transient CXCR5-CXCR3+ antibody-secreting B cell population, CD21hiCD27+ memory B cells, and CD21loCD27+ B cells. Activation of circulating TFH cells correlated with the development of both CD21lo and CD21hi memory B cells. However, preexisting antibodies could limit increases in serum antibody titers. IIV had no marked effect on CD8+, mucosal-associated invariant T, γδ T, and natural killer cell activation. In addition, vaccine-induced B cells were not maintained in peripheral blood at 1 year after vaccination. We provide a dissection of rHA-specific B cells across seven human tissue compartments, showing that influenza-specific memory (CD21hiCD27+) B cells primarily reside within secondary lymphoid tissues and the lungs. Our study suggests that a rational design of universal vaccines needs to consider circulating TFH cells, preexisting serological memory, and tissue compartmentalization for effective B cell immunity, as well as to improve targeting cellular T cell immunity.
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ItemPerturbed CD8+ T cell immunity across universal influenza epitopes in the elderly(OXFORD UNIV PRESS, 2018-02)Influenza epidemics lead to severe illness, life-threatening complications, and deaths, especially in the elderly. As CD8+ T cells are associated with rapid recovery from influenza, we investigated the effects of aging on antigen-specific CD8+ T cells across the universal influenza epitopes in humans. We show that aging is characterized by altered frequencies in T cell subsets, with naive T cells being partially replaced by activated effector/memory populations. Although we observed no striking differences in TCR signaling capacity, T cells in the elderly had increased expression of transcription factors Eomes and T-bet, and such changes were most apparent in CD8+ T cells. Strikingly, the numbers of antigen-specific CD8+ T cells across universal influenza epitopes were reduced in the elderly, although their effector/memory phenotypes remained stable. To understand whether diminished numbers of influenza-specific CD8+ T cells in the elderly resulted from alteration in TCR clonotypes, we dissected the TCRαβ repertoire specific for the prominent HLA-A*02:01-restricted-M158-66 (A2/M158 ) influenza epitope. We provide the first ex vivo data on paired antigen-specific TCRαβ clonotypes in the elderly, showing that influenza-specific A2/M158+ TCRαβ repertoires in the elderly adults varied from those in younger adults, with the main features being a reduction in the frequency of the public TRAV27-TRBV19 TCRαβ clonotype, increased proportion of private TCRαβ signatures, broader use of TRAV and TRBV gene segments, and large clonal expansion of private TCRαβ clonotypes with longer CDR3 loops. Our study supports the development of T cell-targeted influenza vaccines that would boost the T cell compartment during life and maintain the numbers and optimal TCRαβ signatures in the elderly.
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ItemClonally diverse CD38+HLA-DR+CD8+ T cells persist during fatal H7N9 disease(NATURE PORTFOLIO, 2018-02-26)Severe influenza A virus (IAV) infection is associated with immune dysfunction. Here, we show circulating CD8+ T-cell profiles from patients hospitalized with avian H7N9, seasonal IAV, and influenza vaccinees. Patient survival reflects an early, transient prevalence of highly activated CD38+HLA-DR+PD-1+ CD8+ T cells, whereas the prolonged persistence of this set is found in ultimately fatal cases. Single-cell T cell receptor (TCR)-αβ analyses of activated CD38+HLA-DR+CD8+ T cells show similar TCRαβ diversity but differential clonal expansion kinetics in surviving and fatal H7N9 patients. Delayed clonal expansion associated with an early dichotomy at a transcriptome level (as detected by single-cell RNAseq) is found in CD38+HLA-DR+CD8+ T cells from patients who succumbed to the disease, suggesting a divergent differentiation pathway of CD38+HLA-DR+CD8+ T cells from the outset during fatal disease. Our study proposes that effective expansion of cross-reactive influenza-specific TCRαβ clonotypes with appropriate transcriptome signatures is needed for early protection against severe influenza disease.