Submitted to: Veterinary Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/21/2006
Publication Date: 1/15/2007
Citation: Carreno, A.D., Alleman, A.R., Barbet, A.F., Palmer, G.H., Noh, S.M., Johnson, C.M. 2007. In vivo Endothelial Cell Infection by Anaplasma marginale. Veterinary Pathology. 44(1):116-118
Interpretive Summary: Anaplasmosis is an arthropod-borne disease of cattle and other ruminants caused by the gram-negative bacterium, Anaplasma marginale. Within the mammalian host, the bacteria are know to reside in red blood cells. Consequently, the disease is characterized by severe anemia, fever, depression, and weakness. Anaplasmosis severely reduces the production of meat, milk, and fiber in tropical and subtropical areas of the world. Cattle that recover remain persistently infected and serve as a reservoir for transmission to uninfected cattle. It was recently shown that endothelial cells can be infected in vitro with A. marginale. This paper is the first to demonstrate that A. marginale also infects endothelial cells in the bovine host. This observation has several implications for the means by which A. marginale initiates and maintains persistent infection in the bovine host. For example, if endothelial cells are commonly infected during natural disease, these cells may be the initial site of replication in the mammalian host, or may be a reservoir for the organism during persistent infection. In addition, infected endothelial cells, due to the expression of MHC Class-I, may initiate a cell-mediated immune response, whereas infected red blood cells cannot because of the lack of MHC Class-I expression by these cells.
Technical Abstract: Anaplasma marginale has recently been shown to infect endothelial cells in vitro but it remains unknown as to whether endothelial infection also occurs in vivo. In this report, we demonstrate through dual fluorescence microscopy that A. marginale, detected by the monoclonal antibody, ANAF16C1, co-localizes with the endothelial cell marker, von Willebrand factor, in tissue sections from an experimentally inoculated calf. The results indicate that A. marginale infection includes endothelial cells and has implications for both pathogenesis and immune mechanisms.