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Infection and Immunity, June 2007, p. 2965-2973, Vol. 75, No. 6
0019-9567/07/$08.00+0     doi:10.1128/IAI.01896-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Mice Lacking Components of Adaptive Immunity Show Increased Brucella abortus virB Mutant Colonization

Department of Medical Microbiology and Immunology, University of California, One Shields Avenue, Davis, California 95616,¹ Texas A&M University System Health Science Center, Department of Medical Microbiology and Immunology, College Station, Texas 77843-1114²

Received 30 November 2006/ Returned for modification 31 January 2007/ Accepted 23 March 2007

The Brucella abortus type IV secretion system (T4SS), encoded by the virB genes, is essential for survival in mononuclear phagocytes in vitro. In the mouse model, a B. abortus virB mutant was initially able to colonize the spleen at the level of the wild type for approximately 3 to 5 days, which coincided with the development of adaptive immunity. To investigate the relationship between survival in macrophages cultivated in vitro and persistence in tissues in vivo, we tested the ability of mutant mice lacking components of adaptive immunity to eliminate the virB mutant from the spleen during a mixed infection with the B. abortus wild type. Ifng^–/– or ß₂m^–/– mice were able to clear the virB mutant to the same degree as control mice. However, spleens of Rag1^–/– mice and Igh6^–/– mice were more highly colonized by the virB mutant than control mice after 14 to 21 days, suggesting that, in these mice, there is not an absolute requirement for the T4SS to mediate persistence of B. abortus in the spleen. Macrophages isolated from Igh6^–/– mice killed the virB mutant to the same extent as macrophages from control mice, showing that the reduced ability of these mice to clear the virB mutant from the spleen does not correlate with diminished macrophage function in vitro. These results show that in the murine model host, the T4SS is required for persistence beyond 3 to 5 days after infection and suggest that the T4SS may contribute to evasion of adaptive immune mechanisms by B. abortus.

Published ahead of print on 9 April 2007.

Editor: F. C. Fang

This article has been cited by other articles:

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