AUTHOR=Belkahia Hanène , Ben Abdallah Meriem , Andolsi Rihab , Selmi Rachid , Zamiti Sayed , Kratou Myriam , Mhadhbi Moez , Darghouth Mohamed Aziz , Messadi Lilia , Ben Said Mourad 

TITLE=Screening and Analysis of Anaplasma marginale Tunisian Isolates Reveal the Diversity of lipA Phylogeographic Marker and the Conservation of OmpA Protein Vaccine Candidate

JOURNAL=Frontiers in Veterinary Science

VOLUME=8

YEAR=2021

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2021.731200

DOI=10.3389/fvets.2021.731200

ISSN=2297-1769

ABSTRACT=<p>Bovine anaplasmosis caused by <italic>Anaplasma marginale</italic> is a disease responsible for serious animal health problems and great economic losses all over the world. Thereby, the identification of <italic>A. marginale</italic> isolates from various bioclimatic areas in each country, the phylogeographic analysis of these isolates based on the most informative markers, and the evaluation of the most promising candidate antigens are crucial steps in developing effective vaccines against a wide range of <italic>A. marginale</italic> strains. In order to contribute to this challenge, a total of 791 bovine samples from various bioclimatic areas of Tunisia were tested for the occurrence of <italic>A. marginale</italic> DNA through <italic>msp4</italic> gene fragment amplification. Phylogeographic analysis was performed by using <italic>lipA</italic> and <italic>sucB</italic> gene analyses, and the genetic relationship with previously characterized <italic>A. marginale</italic> isolates and strains was analyzed by applying similarity comparison and phylogenetic analysis. To evaluate the conservation of OmpA protein vaccine candidate, almost complete <italic>ompA</italic> nucleotide sequences were also obtained from Tunisian isolates, and various bioinformatics software were used in order to analyze the physicochemical properties and the secondary and tertiary structures of their deduced proteins and to predict their immunodominant epitopes of B and T cells. <italic>A. marginale</italic> DNA was detected in 19 bovine samples (2.4%). Risk factor analysis shows that cattle derived from subhumid bioclimatic area were more infected than those that originated from other areas. The analysis of <italic>lipA</italic> phylogeographic marker indicated a higher diversity of Tunisian <italic>A. marginale</italic> isolates compared with other available worldwide isolates and strains. Molecular, phylogenetic, and immuno-informatics analyses of the vaccine candidate OmpA protein demonstrated that this antigen and its predicted immunodominant epitopes of B and T cells appear to be highly conserved between Tunisian isolates and compared with isolates from other countries, suggesting that the minimal intraspecific modifications will not affect the potential cross-protective capacity of humoral and cell-mediated immune responses against multiple <italic>A. marginale</italic> worldwide strains.</p>