Molecular basis for variable expression of merozoite surface antigen gp45 among american isolates of Babesia bigemina

Immunization with the merozoite surface glycoprotein gp45 induces protection against challenge using the homologous Babesia bigemina strain. However, gp45 B-cell epitopes are highly polymorphic among B. bigemina strains isolated from different geographical locations within North and South America. T...

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Bibliographic Details
Published in:Infection and immunity 2001-06, Vol.69 (6), p.3782-3790
Main Authors: FISHER, Tina G, MCELWAIN, Terry F, PALMER, Guy H
Format: Article
Language:English
Subjects:
Americas
Amino Acid Sequence
Animals
Antigenic Variation
Antigens, Protozoan - genetics
Antigens, Protozoan - immunology
Antigens, Protozoan - metabolism
Antigens, Surface - genetics
Antigens, Surface - immunology
Antigens, Surface - metabolism
Babesia - genetics
Babesia - growth & development
Babesia - immunology
Babesia - isolation & purification
Babesia bigemina
Babesiosis - immunology
Babesiosis - parasitology
Bacteriology
Base Sequence
Biological and medical sciences
Cattle
Cloning, Molecular
Fundamental and applied biological sciences. Psychology
Fungal and Parasitic Infections
Genetics
glycoprotein gp45
Membrane Glycoproteins - chemistry
Membrane Glycoproteins - genetics
Membrane Glycoproteins - immunology
Microbiology
Molecular Sequence Data
Polymorphism, Genetic
Protozoa
Protozoan Proteins
Sequence Analysis, DNA
Vaccines, antisera, therapeutical immunoglobulins and monoclonal antibodies
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Summary:Immunization with the merozoite surface glycoprotein gp45 induces protection against challenge using the homologous Babesia bigemina strain. However, gp45 B-cell epitopes are highly polymorphic among B. bigemina strains isolated from different geographical locations within North and South America. The molecular basis for this polymorphism was investigated using the JG-29 biological clone of a Mexico strain of B. bigemina and comparison with the Puerto Rico, St. Croix, and Texcoco strains. The molecular size and antibody reactivity of gp45 expressed by the JG-29 clone were identical to those of the parental Mexico strain. gp45 cDNA and the genomic locus encompassing gp45 were cloned and sequenced from JG-29. The locus sequence and Southern blot data were consistent with a single gp45 copy in the JG-29 genome. The JG-29 cDNA expressed the full-length protein recognized by the gp45-specific monoclonal antibody 14/1.3.2. The genomes of the Puerto Rico and St. Croix strains of B. bigemina were shown to lack a closely related gp45-like gene by PCR using multiple primer sets and by Southern blots using both full-length and region-specific gp45 probes. This genomic difference was confirmed using unpassaged isolates from a 1999 disease outbreak in Puerto Rico. In contrast, the Texcoco strain retains a gp45 gene, encoding an open reading frame identical to that of JG-29. However, the Texcoco gp45 gene is not transcribed. These two mechanisms, lack of a closely related gp45-like gene and failure to transcribe gp45, result in generation of antigenic polymorphism among B. bigemina strains, and the latter mechanism is unique compared to prior mechanisms of antigenic polymorphism identified in babesial parasites.
ISSN:0019-9567
1098-5522
DOI:10.1128/IAI.69.6.3782-3790.2001