Genetic Diversity of Microneme Protein 2 and Surface Antigen 1 of Eimeria tenella

Abstract

Avian coccidiosis is a disease caused by members of the genus Eimeria. Huge economic losses incurred by the global poultry industry due to coccidiosis have increased the need for cost-effective and easily available recombinant vaccines. Microneme protein 2 (MIC2) and surface antigen 1 (SAG1) of E. tenella have been recognised as potential vaccine candidates. However, the genetic diversity of the antigens in field isolates, which affects vaccine efficacy, has yet to be largely investigated. Here, we analysed genetic diversity and natural selection of etmic2 and etsag1 in Korean E. tenella isolates. Both genes exhibited low levels of genetic diversity in Korean isolates. However, the two genes showed different patterns of nucleotide diversity and amino acid polymorphism involving the E. tenella isolates obtained from different countries including China and India. These results underscore the need to investigate the genetic diversity of the vaccine candidate antigens and warrant monitoring of genetic heterogeneity and evolutionary aspects of the genes in larger numbers of E. tenella field isolates from different geographical areas to design effective coccidial vaccines.

Identification and Protective Efficacy of Eimeria tenella Rhoptry Kinase Family Protein 17

“…However, further studies based on larger numbers of E. tenella field isolates from different geographical areas are needed to determine genetic heterogeneity. Meanwhile, it is necessary to evaluate the protective efficacy of EtROP17 showing amino acid changes, as genetic polymorphisms of vaccine candidates may affect protective efficacy [ 30 ].…”

What Do We Know about Surface Proteins of Chicken Parasites Eimeria?

“…Low antigenic diversity has been reported for genes encoding for E. tenella surface antigens such as IMP-1, AMA1, SAG1, and MIC2 [ 108 , 131 , 132 ], a desirable feature for their inclusion in vaccines formulations since a high variability could impair its effectivity in different regions. Low variability for a protein is usually related to an essential function.…”

“…Recently, the genetic diversity of this antigen—along with EtMIC2—was analysed among 231 E. tenella- positive isolates from China and India, and compared with Korean isolates. The study demonstrated that this antigen is highly conserved since little variability was found among isolates [ 108 ]. Etsag1 in these isolates was classified into four different haplotypes and showed limited amino acid polymorphism.…”

Construction of recombinant SAG22 Bacillus subtilis and its effect on immune protection of coccidia

“…The expression of SAG is differentially regulated between oocyst/zygotes and second-generation cleavage stages, with only one being specifically expressed in the zygotes, a few in both stages, and most in the second generation cleavage ( Tabares et al, 2004 ), with the SAG B gene being specifically expressed in the second-generation cleavage peak expression in the second generation of cleistogamy. In recent years, many researchers have investigated the immunogenicity of SAG proteins, such as SAG1 ( Vo et al, 2021 ), SAG2, SAG4 ( Zhao et al, 2020b ), SAG6, SAG15 ( Geng et al, 2022 ), SAG16, SAG22, SAG23 ( Song et al, 2021 ; Zhao et al, 2021 ), among which SAG1, SAG4, SAG15, and SAG22 have candidate antigenic genes to be anticoccidial vaccines. In general, protective antigens will prefer proteins expressed in the intracellular phase or in the metabolically active phase of the worm, whereas SAG22 belongs to the SAG B gene, which is capable of efficient expression in the second generation of cleavers.…”