Previous Article | Next Article ![]()
Clinical and Vaccine Immunology, May 2007, p. 605-616, Vol. 14, No. 5
1071-412X/07/$08.00+0 doi:10.1128/CVI.00398-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Bacteriology Division, U.S. Army Medical Research Institute of Infectious Diseases, 1425 Porter Street, Fort Detrick, Frederick, Maryland 21702
Received 27 October 2006/ Returned for modification 9 January 2007/ Accepted 7 March 2007
Pneumonic plague is a severe, rapidly progressing disease for which there is no effective vaccine. Since the efficacy of new vaccines cannot be tested in humans, it is essential to develop in vitro surrogate assays that are valid predictors of immunity. The F1 capsule antigen stimulates a protective immune response to most strains of Yersinia pestis. However, strains of Y. pestis that are F1 but still virulent have been isolated, and an in vitro assay, the results which can predict protection against both F1+ and F1 strains, is needed. The virulence antigen (V) is an essential virulence factor of Y. pestis and stimulates protective antibodies. We investigated potential correlates of plague immunity that are based on anti-V antibody-mediated neutralization of Yersinia-induced macrophage cytotoxicity. The neutralizing activity of sera from mice vaccinated with an F1-V fusion candidate vaccine was determined. The decrease in the level of the apoptosis-specific enzyme caspase-3 significantly predicted survival in one- and two-dose vaccination experiments. Sera from F1-V-vaccinated nonhuman primates were evaluated with macrophage assays based on caspase-3 and on other markers manifested at the different stages in cell death. Using murine- and human-derived macrophages in microscopic and fluorescence-activated-cell-sorting-based live/dead staining assays of terminal necrosis, we demonstrated a strong association between in vitro neutralization of macrophage cytotoxicity induced by serum-treated Yersinia and in vivo protection against lethal infection. These results provide a strong base for the development of reliable in vitro correlate bioassays that are predictive of protective immunity to plague.
Published ahead of print on 21 March 2007.
This article has been cited by other articles:
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»