MSP1a analysis expands Anaplasma marginale strain classification

A computational analysis of 157 Anaplasma marginale MSP1a sequences submitted to the National Center for Biotechnology Information between 2013 and 2023 identified 189 unique tandem-repeat types and expanded a molecular classification used to characterize diversity of the tick-borne pathogen. The work also revealed previously unreported tandem-repeat types, new positions of serine within repeats and substantial variation among predicted B-cell epitope variants.

MSP1a is the major surface protein 1a of A. marginale, a rickettsial pathogen associated with bovine anaplasmosis. Its variable N-terminal tandem repeats make the protein a widely used molecular marker for assessing strain diversity. Building on research published by Cabezas-Cruz in 2013, the study updated the nomenclature and classification of the sequences submitted during the 2013–2023 period.

Researchers characterized the amino-acid variation within the tandem repeats and used in-silico methods to predict their secondary structures and B-cell epitopes. These computational predictions identified differences among epitope variants across the analyzed MSP1a sequences. Because the evidence comes from sequence analysis and structural or epitope prediction, the results characterize molecular variation rather than directly demonstrating protection, vaccine performance or disease outcomes.

The researchers also compared the new sequence dataset with previously published datasets and classified the unique R1 tandem repeats into ecoregion clusters through principal component analysis of normalized difference vegetation index values. This geographic analysis provides an additional way to examine variation in the molecular marker, but the source does not report longitudinal sampling or establish that any regional pattern represents a change over time. Overall, the updated classification offers a more detailed framework for future strain typing, epidemiological investigation and vaccine research involving A. marginale.

Subject of Research: Computational classification and structural analysis of Anaplasma marginale MSP1a tandem-repeat variants

Article Title: Nomenclature, classification, and in-silico structural analysis of MSP1a variants of Anaplasma marginale

Article References: Siddiki, A. Z., Humaira, N., Hossain, N. S., Akbar, Y. B., Palit, P., Phwe, P. E., Eva, R. A., Alshaar, H., Tia, M. I., Marma, K., Akter, B., Sultana, S., & Alam, S. (2026). Nomenclature, classification, and in-silico structural analysis of MSP1a variants of Anaplasma marginale. PLOS One, 21(10), e0360505. https://doi.org/10.1371/journal.pone.0360505

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DOI: 10.1371/journal.pone.0360505

Keywords: Anaplasma marginale, MSP1a, bovine anaplasmosis, tandem repeats, strain diversity, B-cell epitopes, tick-borne pathogen, sequence analysis, epidemiology, vaccine research, Nomenclature, classification