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Dimorphic sequences of rap-1 genes encode B and CD4+ T helper lymphocyte epitopes in the Babesia bigemina rhoptry associated protein-1.
Title | Dimorphic sequences of rap-1 genes encode B and CD4+ T helper lymphocyte epitopes in the Babesia bigemina rhoptry associated protein-1. |
Publication Type | Journal Article |
Year of Publication | 1996 |
Authors | Hötzel, I, Brown, WC, McElwain, TF, Rodriguez, SD, Palmer, GH |
Journal | Mol Biochem Parasitol |
Volume | 81 |
Issue | 1 |
Pagination | 89-99 |
Date Published | 1996 Oct 18 |
ISSN | 0166-6851 |
Keywords | Animals, Antibodies, Monoclonal, Antigens, Protozoan, B-Lymphocytes, Babesia, Base Sequence, Cattle, CD4-Positive T-Lymphocytes, Disulfides, DNA Primers, Epitope Mapping, Epitopes, Genes, Protozoan, Molecular Sequence Data, Polymorphism, Genetic, Protozoan Proteins, Recombinant Proteins |
Abstract | The rhoptry-associated protein-1 (RAP-1) of Babesia bigemina induces protective immune responses in cattle and contains neutralization-sensitive B cell epitopes. RAP-1 variants containing blocks of sequence dimorphism in the amino and carboxy terminal ends are encoded by four nonallelic genes in B. bigemina. Epitopes recognized by RAP-1 specific monoclonal antibodies (MAbs) and bovine CD4+ T cell clones were mapped to determine whether these epitopes are localized in the amino and carboxy terminal dimorphic regions. Four B cell epitopes, including a neutralization-sensitive epitope, required both the amino terminal variant type 1 (NT-1) and non-dimorphic sequences for conformation. Intrachain disulfide bonds were required for at least one of these epitopes, since reduction and alkylation of cysteine residues abolished MAb binding. A fifth B cell epitope was mapped to the carboxy terminal variant type 1 (CT-1). As expected, the neutralizing MAb and two other MAbs requiring NT-1 for epitope binding recognized only the two RAP-1 variants with the NT-1 sequence, while the MAb binding an epitope in CT-1 did not bind RAP-1 variants with CT-2. In contrast, the fourth MAb requiring NT-1 for binding recognized all rap-1 gene products, indicating that dimorphic residues are not part of the epitope recognized by this MAb. Bovine CD4+ T cell clones characterized previously as responding in a strain dependent fashion recognized at least one epitope in CT-1, and did not cross-react with CT-2. A second group of bovine CD4+ T cell clones that responded to multiple parasite strains recognized an epitope in a non-dimorphic region of RAP-1. These data indicate that dimorphic regions of RAP-1 encode unique B and T helper lymphocyte epitopes and may be required for enhanced protective immune responses in cattle. |
Alternate Journal | Mol. Biochem. Parasitol. |
PubMed ID | 8892308 |
Grant List | AI30136 / AI / NIAID NIH HHS / United States |