Novel Replication Profiles of Brucella in Human Trophoblasts Give Insights Into the Pathogenesis of Infectious Abortion

Many infectious agents cause abortion in humans and in animals. In this issue of the Journal of Infectious Diseases ,a n article by Salcedo et al [1] describes the behavior of Brucella strains in human trophoblasts and presents data that change the current paradigm regarding Brucella virulence. Brucellosis is a serious disease caused by bacteria of the genus Brucella. The disease affects all species of farm animals, although it is most important when it affects ruminants. Brucellosis has a worldwide impact in terms of its epidemiology, human health risks, and effects on trade. In most natural animal hosts the predominant symptom is abortion, with consequent loss of offspring and milk yield. In males, orchitis and epididymitis occur with a resulting loss in fertility. Three species, B. melitensis, B. abortus, and B. suis, can be readily transmitted to man, either following professional contact with infected animals or following the ingestion of contaminated dairy products. Despite much effort worldwide, no vaccine is available for human prophylaxis, but infections can be treated with a combination of antibiotics. Brucella is a facultative intracellular pathogen that can survive and replicate in many types of host cells, with macrophages as prime targets. This ability of Brucella to replicate intracellularly is central to its pathogenicity. When Brucella infects pregnant animals, it colonizes the trophoblasts in the placenta where it grows to very high density. In the mid-1980s, seminal studies from the Cheville lab showed that during placentitis of goats, Brucella were first seen in phagosomes in erythrophagocytic trophoblasts and in a compartment resembling rough endoplasmic reticulum in chorioallantoic trophoblasts [2, 3]. Although brucellosis is recognized as a cause of infectious abortion in animals, evidence that it causes abortion in humans is less clear. In the late 1990s, studies expanded on the observations in goat placentas, unraveling the cell biology of Brucella infections using HeLa cells [4, 5]. Unlike certainintracellularpathogensthatescape