Abstract
Anaplasma marginale (A. marginale) has a remarkable impact on livestock production, and an effective vaccine is not currently available due to the inexistence of a small animal model. Recently, BALB/c mice were successfully infected with A. marginale, resulting in an acute and persistent anaplasmosis infection. Here, we designed a hybrid protein containing repeats of polypeptide 1a from major surface protein-1 complex (MSP1a) repeats and common epitopes of outer membrane proteins (OMPs) OMP7, OMP8 and OMP9 expressed in Escherichia coli. Our proof-of-concept assessed vaccinal effectiveness against a challenge with live bacteria. The MSP1a/OMP7/8/9 immunized BALB/C mice exhibited a strong reduction in rickettsemia and had no signs of anaplasmosis or hepatic lesions. In contrast, the non-immunized mice exhibited signs of anaplasmosis and a body weight loss associated with increases in monocyte and neutrophil counts. Furthermore, the non-immunized mice displayed atrophies with chronic inflammatory infiltrates in the spleen and increased binucleation and hydropic degeneration in the hepatocytes. Our findings demonstrated that immunization with our hybrid protein induced a strong reduction in rickettsemia and conferred protection against anaplasmosis. Therefore, given the strong evidence of the protective effect against anaplasmosis, hybrid protein designs are potential candidates for the rational design of vaccinal subunits.
Highlights
Anaplasma marginale (A. marginale) causes a life-threatening disease with a remarkable impact on human and animal health
Expression, antigenicity and immunogenicity of the hybrid major surface protein 1a (MSP1a)/OMP7/8/9 The MSP1a/OMP7/8/9 synthetic DNA sequence was designed with repeats in MSP1a and two common sequences from OMP7, OMP8 and OMP9 using A. marginale GenBank: JN564640.1 St
The 3D prediction suggested that the MSP1 repeats and common OMP7–OMP9 surface antigens were exposed on the surface of the hybrid protein (Figure 1B)
Summary
Anaplasma marginale (A. marginale) causes a life-threatening disease with a remarkable impact on human and animal health. A microscopic analysis is the best method for the diagnosis of anaplasmosis but is not reliable for detecting pre-symptomatic or carrier animals. In these cases, Cangussu et al Vet Res (2018) 49:6 serological and molecular detection methods could be indicated [4]. The gold standard for the identification of A. marginale-free blood is the sub-inoculation of blood from the suspect animal into a splenectomized calf; this method is costly and raises animal welfare issues. Other methods, such as ELISA tests or PCR methods, have not been formally validated
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