ISSN: 0973-7510

E-ISSN: 2581-690X

Review Article | Open Access
Noor Hanisa Harun1, Muhamad Yazli Yuhana2, Ang-Lim Chua3 and Seok Mui Wang3-5
1Institute for Medical Molecular Biotechnology, Faculty of Medicine, Universiti Teknologi MARA, Sungai Buloh Campus, Selangor, Malaysia.
2KPJ Healthcare University College – Ampang Puteri Specialist Hospital, Infectious Diseases Unit, Ampang, Selangor, Malaysia.
3Department of Medical Microbiology & Parasitology, Faculty of Medicine, Universiti Teknologi MARA, Sungai Buloh Campus, Selangor, Malaysia.
4Institute of Pathology, Laboratory and Forensic Medicine (I-PPerForM), Universiti Teknologi MARA, Sungai Buloh Campus, Selangor, Malaysia.
5Non-Destructive Biomedical and Pharmaceutical Research Center, Smart Manufacturing Research Institute, Universiti Teknologi MARA, Puncak Alam Campus, Selangor, Malaysia.
Article Number: 9127 | © The Author(s). 2024
J Pure Appl Microbiol. 2024;18(2):747-761.
Received: 13 November 2023 | Accepted: 20 May 2024 | Published online: 02 June 2024
Issue online: June 2024

Diseases caused by Rickettsiales are often overlooked, although they pose important public health concerns. The Rickettsiales family comprises a broad range of intracellular bacteria with distinct evolutionary adaptations, making the development of treatment measures to combat infections, such as vaccines or antibiotics, a challenge. Interestingly, the outer membrane protein A (OmpA) was found to exist in the cell surface of most human pathogenic bacteria in the order Rickettsiales. However, knowledge about OmpA in each species and strain is scattered and ambiguous. In this study, we systematically compiled the existing information on OmpA and its relationship with human pathogenic rickettsiae to serve as a reference for future research. A comprehensive literature search was conducted using specific keywords across five databases. According to the literature, OmpA of spotted fever group rickettsia plays a crucial role as an adhesin and invasin that directly interacts with the surface of mammalian host cells to mediate bacterial localization in host cells. The presence of a premature stop codon in the amino acid sequence resulted in the secretion of non-functional OmpA, which is one of the main reasons for rickettsial strains or species to become avirulent. Similarly, OmpA also functions as an important adhesin in the Anaplasma family when it interacts with the sLex and sLex-like glycan of myeloid and endothelial cells, respectively. However, the OmpA of Anaplasma must be co-functional with the other two adhesins to promote bacterial internalization. Interestingly, certain sites in the amino acid residues of Ehrlichia and Orientia OmpA are predicted to be homologous to the binding domain region of Anaplasma OmpA. It is therefore suggested that OmpA is an important adhesin for bacteria to bind to their specific mammalian host cells.


Rickettsia, Outer Membrane Protein, Rickettsial Disease, Pathogenesis

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© The Author(s) 2024. Open Access. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License which permits unrestricted use, sharing, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.