Submitted to: Infection and Immunity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/9/2001
Publication Date: N/A
Citation: Interpretive Summary: A South Idaho strain of Anaplasma marginale, an important disease agent in cattle in many parts of the world, including the U.S., and a South Idaho strain of the Rocky Mountain wood tick, Dermacentor andersoni, which transmits Anaplasma in nature, were used in this investigation. The study demonstrated that a major protein (MSP2) on the surface of the Anaplasma organism may be required for infection of the mammalian host. The study also revealed that the selection of variants (SGV1 and SGV2) of this protein occurs early in the development of Anaplasma in the tick.
Technical Abstract: Infectivity of Anaplasma spp. for mammalian hosts develops in infected ticks when they feed on these hosts. With the South Idaho strain of A. marginale, major surface protein 2 (MSP2) variants are restricted to SGV1 and SGV2, which are selected for in the tick and expressed within the salivary glands of a southern Idaho strain of the tick Dermacentor andersoni. Western blot, real-time PCR, and DNA sequencing analyses demonstrate that restriction and expression of MSP 2 occur within the first 48-h of the blood meal, when ticks acquire infection. A. marginale is in the tick salivary glands before transmission feeding begins, but MSP2 protein levels per A. marginale organism sharply increase in ticks during transmission feeding. MSP2 variant selection occurs early in the tick, and the variants are expressed in midgut and salivary glands. MSP2 may be required for infectivity, but its expression seems uncorrelated with development of infectivity.