B cells expressing IL-10 mRNA modulate memory T cells after DNA-Hsp65 immunization

• Main Authors: I. C. Fontoura, A.P.F. Trombone, L. P. Almeida, J. C. C. Lorenzi, R. A. M. Rossetti, T. Malardo, E. Padilha, W. Schluchting, R. L. L. Silva, A. F. Gembre, J. E. C. Fiuza, C. L. Silva, A. Panunto-Castelo, A. A. M. Coelho-Castelo
• Format: Article
• Language: English
• Published: Associação Brasileira de Divulgação Científica 2015-12-01
• Series: Brazilian Journal of Medical and Biological Research
• Subjects: DNA-Hsp65 vaccine; Memory T cells; B cells
• Online Access: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-879X2015001201095&lng=en&tlng=en

In DNA vaccines, the gene of interest is cloned into a bacterial plasmid that is engineered to induce protein production for long periods in eukaryotic cells. Previous research has shown that the intramuscular immunization of BALB/c mice with a naked plasmid DNA fragment encoding the Mycobacterium leprae 65-kDa heat-shock protein (pcDNA3-Hsp65) induces protection against M. tuberculosis challenge. A key stage in the protective immune response after immunization is the generation of memory T cells. Previously, we have shown that B cells capture plasmid DNA-Hsp65 and thereby modulate the formation of CD8+ memory T cells after M. tuberculosis challenge in mice. Therefore, clarifying how B cells act as part of the protective immune response after DNA immunization is important for the development of more-effective vaccines. The aim of this study was to investigate the mechanisms by which B cells modulate memory T cells after DNA-Hsp65 immunization. C57BL/6 and BKO mice were injected three times, at 15-day intervals, with 100 µg naked pcDNA-Hsp65 per mouse. Thirty days after immunization, the percentages of effector memory T (TEM) cells (CD4+ and CD8+/CD44high/CD62Llow) and memory CD8+ T cells (CD8+/CD44high/CD62Llow/CD127+) were measured with flow cytometry. Interferon γ, interleukin 12 (IL-12), and IL-10 mRNAs were also quantified in whole spleen cells and purified B cells (CD43−) with real-time qPCR. Our data suggest that a B-cell subpopulation expressing IL-10 downregulated proinflammatory cytokine expression in the spleen, increasing the survival of CD4+ TEM cells and CD8+ TEM/CD127+ cells.