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For vaccines, CD4+ T cells can spell trouble
The ideal vaccine elicits immune memory—either antibodies or memory T cells—to protect the host from subsequent infections. T cell–mediated immunity requires both helper CD4+ T cells and cytotoxic CD8+ T cells to kill virus-infected cells. But what happens when a vaccine only elicits CD4+ memory T cells? Penaloza-MacMaster et al. probed this question by giving mice a vaccine that generated only memory CD4+ T cells against lymphocytic choriomeningitis virus (LCMV). Instead of protecting mice against chronic LCMV, vaccinated mice developed massive inflammation and died. Virus-specific CD8+ T cells or antibodies protected mice from the pathology. These results may have implications for vaccines against chronic viruses such as HIV.
Science 16 January 2015:
Vol. 347 no. 6219 pp. 278-282
DOI: 10.1126/science.aaa2148
CD4 T cells promote innate and adaptive immune responses, but how vaccine-elicited CD4 T cells contribute to immune protection remains unclear. We evaluated whether induction of virus-specific CD4 T cells by vaccination would protect mice against infection with chronic lymphocytic choriomeningitis virus (LCMV). Immunization with vaccines that selectively induced CD4 T cell responses resulted in catastrophic inflammation and mortality after challenge with a persistent strain of LCMV. Immunopathology required antigen-specific CD4 T cells and was associated with a cytokine storm, generalized inflammation, and multi-organ system failure. Virus-specific CD8 T cells or antibodies abrogated the pathology. These data demonstrate that vaccine-elicited CD4 T cells in the absence of effective antiviral immune responses can trigger lethal immunopathology.