Detection of an Anaplasma marginale common surface protein present in all stages of infection

Abstract

The establishment and maintenance of anaplasmosis-free cattle herds is impaired due to the lack of a rapid, sensitive, and specific serologic test to detect persistently infected cattle which serve as carriers for the organism. To develop an improved diagnostic test for anaplasmosis we screened Anaplasma marginale initial body proteins to identify a protein common to antigenically different isolates that is recognized by the host immune system at all stages of infection. Seronegative cattle were infected with either the Florida, Virginia, or North Texas isolate of A. marginale and monitored for infection by daily examination of Wright-stained blood smears for parasitized erythrocytes. Sera from cattle at different stages of infection, from acute through persistent, were used to immunoprecipitate A. marginale proteins that were metabolically radiolabeled with [35S]methionine or surface radiolabeled with 1251. Multiple A. marginale proteins were recognized by using sera either undiluted or gt 1:10; however, only four or five proteins were sufficiently antigenic to elicit antibody reactive with a 1:1,000 serum dilution. A single protein with an apparent molecular mass of 86 kilodaltons was consistently recognized at all stages of infection regardless of the isolate used to infect the cattle. This protein was demonstrated to be on the surface of the A. marginale initial body and to be water soluble. We propose use of this 86-kilodalton protein to develop an improved serologic test for diagnosis of bovine anaplasmosis. Anaplasmosis is a hemoparasitic disease of cattle endemic in half of the livestock production regions worldwide (20).

Intermolecular relationships of major surface proteins of Anaplasma marginale

“…The Florida strain of A. marginale induces postinfection immunity against heterologous challenge (9,14,28,34) and has been used to identify surface proteins for vaccine development. Four major surface proteins (MSPs) from the Florida strain were recognized by neutralizing polyclonal antibody (23) and designated MSP-1 (105 kDa), MSP-2 (36 kDa), MSP-3 (86 kDa), and MSP-4 (31 kDa) (4,13,17,20,22,24). MSP-5 was originally identified in outer membrane preparations of the Norton Zimbabwe strain and subsequently shown to be conserved in other strains, including Florida (31).…”

Molecular size variations in an immunoprotective protein complex among isolates of Anaplasma marginale

“…Monoclonal antibodies against an erythrocyte-stage surface protein of the Florida isolate of A. marginale neutralize infectivity (20). This major surface protein, designated MSP-1, is recognized by postinfection antisera from cattle immune to A. marginale, regardless of the isolate used to infect the cattle (21). MSP-1 has the ability to induce protection in immunized cattle against both a homologous (20) and a heterologous (G. H. Palmer, T. C. McGuire, and A. F. Barbet, unpublished data) A. marginale challenge and has been proposed as the basis of a subunit vaccine.…”

Cloning and expression of the gene encoding the major surface protein 5 (MSP5) of Anaplasma phagocytophilum and potential application for serodiagnosis

“…This delayed immune response is consistent with what is seen in A marginale-infected cattle, where the immune response to MSP5 is most pronounced in later stages of infection (.90 days). 13,31 Overall the agreement between IFA/PCR-positive samples and the A phagocytophilum rMSP5 ELISA was .90%. This antigen appears to have potential use in the diagnosis of A phagocytophilum infection in both humans and dogs.…”

“…In previous studies, the immune response to MSP5 of A marginale appeared to roughly coincide with the appearance of acute rickettsemia, approximately 20 days postinoculation, 13 but it appears to become more pronounced during later stages of infection (.90 days postinoculation). 13,31 Antibodies to rMAP2 of E canis were identified in dogs as early as 16 days and as late as 24-months postinoculation. 19 Similarly, in this study, antibodies to rMSP5 of A phagocytophilum began to increase by day-22 postinoculation in a dog experimentally infected with the NY18 strain.…”