Immune control of Babesia bovis infection Brown, Wendy C.; Norimine, Junzo; Knowles, Donald P. ...
Veterinary parasitology,
05/2006, Letnik:
138, Številka:
1
Journal Article
Recenzirano
Babesia bovis causes an acute and often fatal infection in adult cattle, which if resolved, leads to a state of persistent infection in otherwise clinically healthy cattle. Persistently infected ...cattle are generally resistant to reinfection with related parasite strains, and this resistance in the face of infection is termed concomitant immunity. Young animals are generally more resistant than adults to
B. bovis infection, which is dependent on the spleen. Despite the discovery of
B. bovis over a century ago, there are still no safe and effective vaccines that protect cattle against this most virulent of babesial pathogens. Immunodominant antigens identified by serological reactivity and dominant T-cell antigens have failed to protect cattle against challenge. This review describes the innate and acquired immune mechanisms that define resistance in young calves and correlate with the development of concomitant immunity in older cattle following recovery from clinical disease. The first sections will discuss the innate immune responses by peripheral blood- and spleen-derived macrophages in cattle induced by
B. bovis merozoites and their products that limit parasite replication, and comparison of natural killer cell responses in the spleens of young (resistant) and adult (susceptible) cattle. Later sections will describe a proteomic approach to discover novel antigens, especially those recognized by immune CD4
+ T lymphocytes. Because immunodominant antigens have failed to stimulate protective immunity, identification of subdominant antigens may prove to be important for effective vaccines. Identification of CD4
+ T-cell immunogenic proteins and their epitopes, together with the MHC class II restricting elements, now makes possible the development of MHC class II tetramers and application of this technology to both quantify antigen-specific lymphocytes during infection and discover novel antigenic epitopes. Finally, with the imminent completion of the
B. bovis genome-sequencing project, strategies using combined genomic and proteomic approaches to identify novel vaccine candidates will be reviewed. The availability of an annotated
B. bovis genome will, for the first time, enable identification of non-immunodominant proteins that may stimulate protective immunity.
Recombinant antigen-based enzyme-linked immunosorbent assay (ELISA) was developed for the serological diagnosis of
Babesia bigemina infection by using a full-length
B. bigemina rhoptry-associated ...protein 1 (rRAP-1) and the truncated C-terminal RAP-1 (rRAP-1/CT). While the rRAP-1 showed cross reactivity between
B. bigemina- and
Babesia bovis-infected bovine sera, the rRAP-1/CT was highly specific to
B. bigemina-infected bovine sera and proved useful in the detection of sequential sera collected from an experimentally infected cow during the acute and latent infection. The high yield of soluble rRAP-1/CT and its diagnostic specificity demonstrate its potential in the diagnosis of
B. bigemina infection. Its usefulness for epidemiological investigation is currently being evaluated.
The Babesia bovis genome encodes a rap-1 related gene denominated RAP-1 related antigen (RRA). In this study, we analysed the pattern of expression, immunogenicity and functional relevance of RRA.
...Phylogenetic analysis was performed using the program Phylip. Expression of rra was analysed by Northern blots, RT-PCR, immunoprecipitation, Western blots and immunofluorescence. RRA antigenicity was tested by T-cell proliferation and Western blot analysis, and functional relevance was determined in an in vitro neutralization assay.
RRA is more closely related to RAP-1b of Babesia bigemina than to B. bovis RAP-1, and it is highly conserved among distinct strains. Transcriptional analysis suggests lower numbers of rra transcripts compared to rap-1. Immunoprecipitation of metabolically labelled B. bovis proteins with antibodies against synthetic peptides representing predicted antigenic regions of RRA confirmed the expression of a ∼43 kDa RRA in cultured merozoites. Antibodies present in B. bovis hyperimmune sera, but not in field-infected cattle sera, reacted weakly with recombinant RRA, and no significant stimulation was obtained using recombinant RRA as antigen in T-cell proliferation assays, indicating that RRA is a subdominant antigen. Antibodies against RRA synthetic peptides reacted with merozoites using immunofluorescence, and were able to significantly inhibit erythrocyte invasion in in vitro neutralization tests, suggesting functional relevance for parasite survival.
B. bovis express a novel subdominant RAP-1-like molecule that may contribute to erythrocyte invasion and/or egression by the parasite.
Abstract A gene coding for a protein with sequence similarity to the Toxoplasma gondii micronemal 1 (MIC1) protein that contains a copy of a domain described as a sialic acid-binding micronemal ...adhesive repeat (MAR) was identified in the Babesia bovis genome. The single copy gene, located in chromosome 3, contains an open reading frame encoding a putative 181 amino acid protein, which is highly conserved among distinct B. bovis strains. Antibodies against both recombinant protein and synthetic peptides mimicking putative antigenic regions in the B. bovis -MIC1 (Bbo-MIC1) protein bind to the parasite in immunofluorescence assays and significantly inhibit erythrocyte invasion in in vitro B. bovis cultures. Bbo-MIC1 is recognized by antibodies in serum from B. bovis infected cattle, demonstrating expression and immunogenicity during infection. Overall, the results suggest that Bbo-MIC1 protein is a viable candidate for development of subunit vaccines.
Polyphasic Taxonomy UILENBERG, GERRIT; GOFF, WILL L.
Annals of the New York Academy of Sciences,
October 2006, Letnik:
1081, Številka:
1
Journal Article
Recenzirano
: Several organisms from a number of prokaryotic and eukaryotic groups have presented problems for systematists for a long time. Both phenotypic and genotypic methods for sorting out these ...relationships have been employed. There are limitations with each method when taken alone. Since the purpose of systematics is to determine the correct genealogical relationships among biological organisms, it is necessary to use all available means to arrive at consensus associations, and polyphasic taxonomy, which takes into consideration both methods, is a rational approach. In this short article, we provide a number of examples where polyphasic taxonomy is serving as the means of arriving at the desired consensus.
Abstract A novel Babesia bovis gene family encoding proteins with similarities to the Plasmodium 6cys protein family was identified by TBLASTN searches of the B. bovis genome using the sequence of ...the P. falciparum PFS230 protein as query, and was termed Bbo-6cys gene family. The Bbo-cys6 gene family contains six genes termed Bbo-6cys-A , B , C , D , E and F encoding for proteins containing an arrangement of 6 cysteine residues. The Bbo-6cys genes A, B, C, D, and E are tandemly arranged as a cluster of Chromosome 2 in the B. bovis genome, whereas gene F is located in a distal region in the same chromosome. The Bbo-6cys-E gene, with higher homology to PFS230, was selected for further examination. Immunoblot analysis using recombinant Bbo-6cys-E protein and B. bovis- positive bovine serum demonstrated expression by the parasite and immunogenicity during B. bovis infection. Immunofluorescence analysis using anti-Bbo-6cys-E antibodies confirmed expression of Bbo-6cys-E in in vitro blood stages of B. bovis . In addition, polyclonal antisera against both recombinant Bbo-6cys-E and specific synthetic peptides containing predicted B-cell epitopes of Bbo-6cys-E, significantly inhibited erythrocyte invasion by B. bovis in in vitro neutralization assays, suggesting an important functional role for this protein. Identification of this new gene family in B. bovis and further investigation on its biological significance may aid our understanding of the bovine, tick and parasite relationships and the development of improved control methods against B. bovis infection in cattle.
A competitive enzyme-linked immunosorbent assay (cELISA) based on a broadly conserved, species-specific, B-cell epitope within the C terminus of Babesia bigemina rhoptry-associated protein 1a was ...validated for international use. Receiver operating characteristic analysis revealed 16% inhibition as the threshold for a negative result, with an associated specificity of 98.3% and sensitivity of 94.7%. Increasing the threshold to 21% increased the specificity to 100% but modestly decreased the sensitivity to 87.2%. By using 21% inhibition, the positive predictive values ranged from 90.7% (10% prevalence) to 100% (95% prevalence) and the negative predictive values ranged from 97.0% (10% prevalence) to 48.2% (95% prevalence). The assay was able to detect serum antibody as early as 7 days after intravenous inoculation. The cELISA was distributed to five different laboratories along with a reference set of 100 defined bovine serum samples, including known positive, known negative, and field samples. The pairwise concordance among the five laboratories ranged from 100% to 97%, and all kappa values were above 0.8, indicating a high degree of reliability. Overall, the cELISA appears to have the attributes necessary for international application.
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