|Knowles, Donald - Don|
Submitted to: Gene
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/27/2005
Publication Date: 11/21/2005
Citation: Rodriguez, J., Palmer, G.H., Knowles Jr, D.P., Brayton, K.A. 2005. Distinctly different msp2 pseudogene repertoires in Anaplasma marginale strains that are capable of superinfection. Gene. 361:127-132. Interpretive Summary: Control of infectious diseases such as the bacterium Anaplasma marginale (an infection of cattle) requires an understanding of how such organisms remain viable in the cow for life and are transmissible. One of the components of A. marginale is the protein named MSP-2. This protein has the ability to change in the face of immunity and facilitate persistence of A. marginale. Differences in MSP-2 were correlated with the ability of A. marginale to superinfect. Superinfection is the ability of one strain of A. marginale to infect a cow which is already persistently infected with another strain of A. marginale.
Technical Abstract: Lifelong persistent infection of cattle is a hallmark of the tick transmitted pathogen Anaplasma marginale. Antigenic variation of Major Surface Protein 2 (MSP2) plays an important role in evasion of the host immune response to allow persistence. Antigenic variation of MSP2 is achieved by gene conversion of pseudogenes into the single operon linked expression site and the diversity of variants is defined by the pseudogene repertoire. Once an animal is persistently infected with one strain of A. marginale, infection with a second strain (superinfection) is rare. However, we recently detected animals superinfected with different strains of A. marginale and hypothesized that the msp2 pseudogene repertoire would be distinct in these superinfecting strains, consistent with encoding different sets of surface variants. Five strains of A. marginale were selected in order to identify and compare msp2 pseudogene content; these included strains with similar and different msp1alpha genotypes, and genotypes that were representative of the strains that were found in the superinfected animals. Southern blot analysis of strains associated with superinfection revealed distinctly different msp2 banding patterns, in contrast to a pattern suggesting identical pseudogene content among related strains not associated with superinfection. Indeed, targeted sequence analysis of msp2 pseudogenes showed identical pseudogene repertoires in genotypically closely related strains and varying amounts of dissimilarity in the pseudogene repertoire in strains with distinctly different msp1alpha genotypes, but totally different msp2 pseudogene repertoires between the strains that were found in superinfected animals. This finding supports the hypothesis that the occurrence of superinfection reflects the differences in the msp2 repertoire and corresponding diversity of variants.