Anaplasma marginale: Diversity, Virulence, and Vaccine Landscape through a Genomics Approach

Abstract

In order to understand the genetic diversity of A. marginale, several efforts have been made around the world. This rickettsia affects a significant number of ruminants, causing bovine anaplasmosis, so the interest in its virulence and how it is transmitted have drawn interest not only from a molecular point of view but also, recently, some genomics research have been performed to elucidate genes and proteins with potential as antigens. Unfortunately, so far, we still do not have a recombinant anaplasmosis vaccine. In this review, we present a landscape of the multiple approaches carried out from the genomic perspective to generate valuable information that could be used in a holistic way to finally develop an anaplasmosis vaccine. These approaches include the analysis of the genetic diversity of A. marginale and how this affects control measures for the disease. Anaplasmosis vaccine development is also reviewed from the conventional vaccinomics to genome-base vaccinology approach based on proteomics, metabolomics, and transcriptomics analyses reported. The use of these new omics approaches will undoubtedly reveal new targets of interest in the near future, comprising information of potential antigens and the immunogenic effect of A. marginale proteins.

Novel variants of the newly emerged Anaplasma capra from Korean water deer (Hydropotes inermis argyropus) in South Korea

“…Consistent with our results, sequence variation at the studied gene markers has been reported previously among isolates from ticks, sheep and goats [12,[15][16][17][18][20][21][22][23][24][25]. Similarly, genetic variation is common in other Anaplasma species [40][41][42][43][44][45]. Although genetic diversity is reportedly related to infectivity, virulence, pathogenicity, niche preference, immune evasion, and/or host adaptability [46][47][48][49], this has not been established in A. capra and further studies are needed to evaluate these relationships.…”

Insight into the genetic diversity of Anaplasma marginale in cattle from ten provinces of China

“…To date, a great number of geographical strains of A. marginale have been identified on a global scale, which vary in genotype, virulence, antigenic characteristics and infectivity for ticks [ 6 ]. Characterization of the genetic diversity of A. marginale strains has been performed based on the variability of tandem repeat amino acid sequences located in the N-terminal region of the major surface protein (Msp) 1a, and numerous geographical Msp1a tandem repeats and genotypes were identified [ 10 ]. In China, A. marginale has been recognized for over 30 years, and Rhipicephalus microplus is considered to be the most important tick vector with a nationwide distribution [ 11 , 12 ].…”

Genome-Based Vaccinology Applied to Bovine Anaplasmosis

“…The inclusion of Msp1a or its "conserved epitopes" should be carried with caution as the diversity of this marker is wider in regions where the tick vector is R. microplus than in its absence [10,45]. Vaccination based on Msp1a epitopes is further confounded by the fact that the Msp1a variable region may contain one or several repeats which may include the same or different repeats and that there are more than 300 repeats reported [45,46] and this number is bound to increase as the number of epidemiology studies is published. Furthermore, the number of Msp1a-distinct strains (up to nine) within the same herd or even within the same animal [10,47,48] complicates even more the design of an effective vaccine.…”