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Babesia bovis RON2 contains conserved B-cell epitopes that induce an invasion-blocking humoral immune response in immunized cattle.

ABSTRACT: BACKGROUND:Babesia bovis belongs to the phylum Apicomplexa and is the major causal agent of bovine babesiosis, the most important veterinary disease transmitted by arthropods. In apicomplexan parasites, the interaction between AMA1 and RON2 is necessary for the invasion process, and it is a target for vaccine development. In B. bovis, the existence of AMA1 has already been reported; however, the presence of a homolog of RON2 is unknown. The aim of this study was to characterize RON2 in B. bovis. RESULTS:The B. bovis ron2 gene has a similar synteny with the orthologous gene in the B. bigemina genome. The entire ron2 gene was sequenced from different B. bovis strains showing > 99% similarity at the amino acid and nucleotide level among all the sequences obtained, including the characteristic CLAG domain for cytoadherence in the amino acid sequence, as is described in other Apicomplexa. The in silico transcription analysis showed similar levels of transcription between attenuated and virulent B. bovis strains, and expression of RON2 was confirmed by western blot in the B. bovis T3Bo virulent strain. Four conserved peptides, containing predicted B-cell epitopes in hydrophilic regions of the protein, were designed and chemically synthesized. The humoral immune response generated by the synthetic peptides was characterized in bovines, showing that anti-RON2 antibodies against peptides recognized intraerythrocytic merozoites of B. bovis. Only peptides P2 and P3 generated partially neutralizing antibodies that had an inhibitory effect of 28.10% and 21.42%, respectively, on the invasion process of B. bovis in bovine erythrocytes. Consistently, this effect is additive since inhibition increased to 42.09% when the antibodies were evaluated together. Finally, P2 and P3 peptides were also recognized by 83.33% and 87.77%, respectively, of naturally infected cattle from endemic areas. CONCLUSIONS:The data support RON2 as a novel B. bovis vaccine candidate antigen that contains conserved B-cell epitopes that elicit partially neutralizing antibodies.

SUBMITTER: Hidalgo-Ruiz M

PROVIDER: S-EPMC6215676 | biostudies-literature | 2018 Nov

REPOSITORIES: biostudies-literature

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Babesia bovis RON2 contains conserved B-cell epitopes that induce an invasion-blocking humoral immune response in immunized cattle.

Hidalgo-Ruiz Mario M Suarez Carlos E CE Mercado-Uriostegui Miguel A MA Hernandez-Ortiz Ruben R Ramos Juan Alberto JA Galindo-Velasco Edelmira E León-Ávila Gloria G Hernández José Manuel JM Mosqueda Juan J

Parasites & vectors 20181103 1

<h4>Background</h4>Babesia bovis belongs to the phylum Apicomplexa and is the major causal agent of bovine babesiosis, the most important veterinary disease transmitted by arthropods. In apicomplexan parasites, the interaction between AMA1 and RON2 is necessary for the invasion process, and it is a target for vaccine development. In B. bovis, the existence of AMA1 has already been reported; however, the presence of a homolog of RON2 is unknown. The aim of this study was to characterize RON2 in B ...[more]

PMID: 30390674

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Project description:BackgroundBabesiosis is an important haemoparasitic disease, caused by the infection and subsequent intra-erythrocytic multiplication of protozoa of the genus Babesia that impacts the livestock industry and animal health. The distribution, epidemiology and genetic characterization of B. bigemina, B. bovis, and B. ovata in cattle in China as well as the prevalence of these protozoan agents were assessed.MethodsA total of 646 blood specimens from cattle, dairy cattle and yaks from 14 provinces were collected and tested for the presence of the three Babesia species via a specific nested PCR assay based on the rap-1 and ama-1 genes. The PCR results were confirmed by DNA sequencing. Gene sequences and the genetic characterization were determined for selected positive samples from each sampling area.ResultsOf a total of 646 samples, 134 (20.7 %), 60 (9.3 %) and 10 (1.5 %) were positive for B. bovis, B. bigemina and B. ovata infections, respectively. Mixed infections were found in 7 of 14 provinces; 43 (6.7 %) samples were infected with B. bovis and B. bigemina. Three samples (0.5 %) exhibited a co-infection with B. bovis and B. ovata, and 6 (0.9 %) were infected with all three parasites. The rap-1a gene of B. bovis indicated a high degree of sequence heterogeneity compared with other published rap-1a sequences worldwide and was 85-100 % identical to B. bovis rap-1a sequences in Chinese isolates. B. bigemina rap-1c and B. ovata ama-1 genes were nearly identical, with 97.8-99.3 % and 97.8-99.6 % sequence identity, respectively, in GenBank.ConclusionsPositive rates of B. bovis and B. bigemina infection are somewhat high in China. The B. bovis infection in yaks was first reported. The significant sequence heterogeneity in different variants of the rap-1a gene from Chinese B. bovis isolates might be a great threat to the cattle industry if RAP-1a protein is used as immunological antigen against Babesia infections in China. The data obtained in this study can be used to plan effective control strategies against babesiosis in China.

Project description:BackgroundBabesia parasites, mainly Babesia bovis and B. bigemina, are tick-borne hemoparasites inducing bovine babesiosis in cattle globally. The clinical signs of the disease include, among others, anemia, fever and hemoglobinuria. Babesiosis is known to occur in tropical and subtropical regions of the world. In this study, we aim to provide information about the occurrence and phylogenetic relationship of B. bigemina and B. bovis species in cattle from different locations in nine provinces of South Africa. A total of 430 blood samples were randomly collected from apparently healthy cattle. These samples were genetically tested for Babesia parasitic infections using nested PCR assays with species-specific primers.ResultsNested PCR assays with Group I primer sets revealed that the overall prevalence of B. bigemina and B. bovis in all bovine samples tested was 64.7% (95% CI = 60.0-69.0) and 35.1% (95% CI = 30.6-39.8), respectively. Only 117/430 (27.2%) animals had a mixed infection. The highest prevalence of 87.5% (95% CI = 77.2-93.5) for B. bigemina was recorded in the Free State province collection sites (Ficksburg, Philippolis and Botshabelo), while North West collection sites had the highest number of animals infected with B. bovis (65.5%; 95% CI = 52.7-76.4). Phylograms were inferred based on B. bigemina-specific gp45 and B. bovis-specific rap-1 nucleotide sequences obtained with Group II nested PCR primers. Phylogenetic analysis of gp45 sequences revealed significant differences in the genotypes of B. bigemina isolates investigated, including those of strains published in GenBank. On the other hand, a phylogeny based on B. bovis rap-1 sequences indicated a similar trend of clustering among the sequences of B. bovis isolates investigated in this study.ConclusionThis study demonstrates the occurrence of Babesia parasites in cattle from different provinces of South Africa. It was also noted that the situation of Babesia parasitic infection in cattle from certain areas within the surveyed provinces had either reached endemic stability or was progressing towards stability.

Project description:BackgroundAmong protozoan parasites in the genus Babesia, Babesia bigemina is endemic and widespread in the East African region while the status of the more pathogenic Babesia bovis remains unclear despite the presence of the tick vector, Rhipicephalus microplus, which transmits both species. Recent studies have confirmed the occurrence of R. microplus in coastal Kenya, and although B. bovis DNA has previously been detected in cattle blood in Kenya, no surveillance has been done to establish its prevalence. This study therefore investigated the occurrence of B. bovis in cattle in Kwale County, Kenya, where R. microplus is present in large numbers.MethodsA species-specific multiplex TaqMan real-time PCR assay targeting two Babesia bovis genes, 18S ribosomal RNA and mitochondrially-encoded cytochrome b and B. bigemina cytochrome b gene was used to screen 506 cattle blood DNA samples collected from Kwale County for presence of Babesia parasite DNA. A sub-set of 29 B. bovis real-time PCR-positive samples were further amplified using a B. bovis-specific spherical body protein-4 (SBP-4) nested PCR and the resulting products sequenced to confirm the presence of B. bovis.ResultsA total of 131 animals (25.8%) were found to have bovine babesiosis based on real-time PCR. Twenty-four SBP4 nucleotide sequences obtained matched to B. bovis with a similarity of 97-100%. Of 131 infected animals, 87 (17.2%) were positive for B. bovis while 70 (13.8%) had B. bigemina and 26 (5.1%) were observed to be co-infected with both Babesia species. A total of 61 animals (12.1%) were found to be infected with B. bovis parasites only, while 44 animals (8.7%) had B. bigemina only. Babesia bovis and B. bigemina infections were detected in the three Kwale sub-counties.ConclusionThese findings reveal high prevalence of pathogenic B. bovis in a Kenyan area cutting across a busy transboundary livestock trade route with neighbouring Tanzania. The Babesia multiplex real-time PCR assay used in this study is specific and can detect and differentiate the two Babesia species and should be used for routine B. bovis surveillance to monitor the spread and establishment of the pathogen in other African countries where B. bigemina is endemic. Moreover, these findings highlight the threat of fatal babesiosis caused by B. bovis, whose endemic status is yet to be established. GRAPHICAL ABTRACT.

Dataset Information

Babesia bovis RON2 contains conserved B-cell epitopes that induce an invasion-blocking humoral immune response in immunized cattle.

Publications

Babesia bovis RON2 contains conserved B-cell epitopes that induce an invasion-blocking humoral immune response in immunized cattle.

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