CD4+ T cells are required during priming but not the effector phase of antibody-mediated IFN-gamma-dependent protective immunity against pulmonary Francisella novicida infection |
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Authors: | Powell Heather J Cong Yu Yu Jieh-Juen Guentzel M Neal Berton Michael T Klose Karl E Murthy Ashlesh K Arulanandam Bernard P |
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Institution: | Department of Biology, South Texas Center for Emerging Infectious Diseases, University of Texas at San Antonio, San Antonio, TX 78249, USA. |
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Abstract: | We have previously demonstrated the protective efficacy of intranasal vaccination with a defined Francisella tularensis subsp. novicida DeltaiglC mutant (KKF24) against pulmonary F. novicida U112 challenge. In this study, we further characterized the mechanisms of KKF24-induced immunity. Intranasally vaccinated KKF24 C57BL/6 major histocompatibility class (MHC) class II-/- mice produced minimal antigen-specific interferon (IFN)-gamma and serum antibodies and were highly susceptible (0% survival) to F. novicida challenge, compared to MHC class I-/- or wild-type mice (both 100% survival). Protective immunity could be transferred by immune serum into recipient wild type, but not IFN-gamma-/- mice. The protective effect of KKF24 vaccination against the respiratory F. novicida U112 challenge was not abrogated by anti-CD4 neutralizing antibody treatment and was not conferred by adoptive transfer of KKF24-specific CD4+ T cells. The protective effect of antibody was partially dependent upon Fc receptor-mediated clearance. Taken together, our data indicate that CD4+ T cells are required for priming, but not during the effector phase, of anti-KKF24 antibody-mediated IFN-gamma-dependent immunity against pulmonary F. novicida infection. |
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