Research article

Interferon-γ promotes abortion due to Brucella infection in pregnant mice

Suk Kim¹ , Dong Soo Lee² , Kenta Watanabe¹ , Hidefumi Furuoka³ , Hiroshi Suzuki^2,4 and Masahisa Watarai¹

¹  Department of Applied Veterinary Science, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan

²  Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan

³  Department of Pathological Science, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan

⁴  Department of Development and Medical Technology, Graduate School of Medicine, The University of Tokyo, Hongo, Tokyo 113-0033, Japan

author email corresponding author email

BMC Microbiology 2005, 5:22doi:10.1186/1471-2180-5-22

Published:	4 May 2005

Abstract

Background

The mechanisms of abortion induced by bacterial infection are largely unknown. In the present study, we investigated abortion induced by Brucella abortus, a causative agent of brucellosis and facultative intracellular pathogen, in a mouse model.

Results

High rates of abortion were observed for bacterial infection on day 4.5 of gestation, but not for other days. Regardless of whether fetuses were aborted or stayed alive, the transmission of bacteria into the fetus and bacterial replication in the placenta were observed. There was a higher degree of bacterial colonization in the placenta than in other organs and many bacteria were detected in trophoblast giant cells in the placenta. Intracellular growth-defective virB4 mutant and attenuated vaccine strain S19 did not induce abortion. In the case of abortion, around day 7.5 of gestation (period of placental development), transient induction of IFN-γ production was observed for infection by the wild type strain, but not by the virB4 mutant and S19. Neutralization of IFN-γ, whose production was induced by infection with B. abortus, served to prevent abortion.

Conclusion

These results indicate that abortion induced by B. abortus infection is a result of transient IFN-γ production during the period of placental development.