• Guoquan Zhang, Kasi E Russell-Lodrigue, Masako Andoh, Yan Zhang, Laura R Hendrix, and James E Samuel.
• Department of Microbial and Molecular Pathogenesis, College of Medicine, Texas A&M Health Science Center, College Station, TX 77843-1114, USA. gqzhang@medicine.tamhsc.edu
• J. Immunol. 2007 Dec 15; 179 (12): 8372-80.

AbstractTo elucidate the mechanisms of vaccine-induced protective immunity against Coxiella burnetii infection, we compared the protective efficacy and immunogenicity between formalin-inactivated phase I vaccine (PI-V) and phase II vaccine (PII-V) in BALB/c mice. PI-V generated significant protection while PII-V did not confer measurable protection. Analysis of cytokine and subclass Ab responses indicated that both PI-V and PII-V were able to induce a Th1-dominant immune response but did not identify the component of host response that distinguished their ability to induce protective immunity. Interestingly, immunoblot analysis identified a difference between PI-V and PII-V vaccinates in antigenic recognition by specific Ab isotypes. The observation that PI-LPS elicited significant protection but PII-LPS did not confer measurable protection suggests PI-LPS may play a key role in PI-V-induced protection. Adoptive transfer of either immune sera or splenocytes mediated significant protection in naive BALB/c mice, supporting the notion that both humoral and cellular immunity are important for development of protective immunity. However, the evidence that immune sera and B cells were unable to control infection while T cells conferred significant protection in SCID mice supports the hypothesis that T cell-mediated immunity is critical for host defense against C. burnetii infection. This report presents novel evidence to highlight the importance of PI-LPS and Abs in protective immunity and has important implications for the design of new generation vaccines against Q fever.

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