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Sequence heterogeneity of the major antigenic protein 1 genes from Cowdria ruminantium isolates from different geographical areas.

ABSTRACT: The genes for the immunodominant major antigenic protein 1 (MAP1) of Cowdria ruminantium from four African and two Caribbean isolates were cloned, restriction mapped, and sequenced to identify conserved epitopes for development of serodiagnostic tools for heartwater. Restriction length polymorphisms were observed among the respective MAP1 genes analyzed and were confirmed by sequencing. The sequence data generated for these isolates were compared with data for the previously reported Senegal isolate MAP1 gene. These sequences were found to differ from each other by 0.6 to 14.0%. These differences translate into a 0.8 to 10.0% variation in the predicted protein sequence. In the entire coding sequence, several amino acid substitutions were identified in addition to deletions or insertions at three regions of the gene. These variable regions are referred to as variable regions I, II, and III. From the sequence data, an evolutionary distance tree was constructed; this tree suggested that at least two genetically distinct C. ruminantium strains exist in the Caribbean: the isolate from Antigua is similar to that from Senegal, while the isolate from Guadeloupe is closely related to that from Sudan.

SUBMITTER: Reddy GR

PROVIDER: S-EPMC170360 | biostudies-other | 1996 Jul

REPOSITORIES: biostudies-other

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Sequence heterogeneity of the major antigenic protein 1 genes from Cowdria ruminantium isolates from different geographical areas.

Reddy G R GR Sulsona C R CR Harrison R H RH Mahan S M SM Burridge M J MJ Barbet A F AF

Clinical and diagnostic laboratory immunology 19960701 4

The genes for the immunodominant major antigenic protein 1 (MAP1) of Cowdria ruminantium from four African and two Caribbean isolates were cloned, restriction mapped, and sequenced to identify conserved epitopes for development of serodiagnostic tools for heartwater. Restriction length polymorphisms were observed among the respective MAP1 genes analyzed and were confirmed by sequencing. The sequence data generated for these isolates were compared with data for the previously reported Senegal iso ...[more]

PMID: 8807206

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Project description:Proteins expressed from the map1 multigene family of Ehrlichia ruminantium are strongly recognized by immune T and B cells from infected animals or from animals that were infected and have recovered from heartwater disease (although still remaining infected carriers). Analogous multigene clusters also encode the immunodominant outer membrane proteins (OMPs) in other ehrlichial species. Recombinant protein analogs of the expressed genes and DNA vaccines based on the multigene clusters have been shown to induce protective immunity, although this was less effective in heterologous challenge situations, where the challenge strain major antigenic protein 1 (MAP1) sequence differed from the vaccine strain MAP1. Recent data for several ehrlichial species show differential expression of the OMPs in mammalian versus tick cell cultures and dominant expression of individual family members in each type of culture system. However, many genes in the clusters appear to be complete and functional and to generate mRNA transcripts. Recent data also suggest that there may be a low level of protein expression from many members of the multigene family, despite primary high-level expression from an individual member. A continuing puzzle, therefore, is the biological roles of the different members of these OMP multigene families. Complete genome sequences are now available for two geographically divergent strains of E. ruminantium (Caribbean and South Africa strains). Comparison of these sequences revealed amino acid sequence diversity in MAP1 (89% identity), which is known to confer protection in a mouse model and to be the multigene family member primarily expressed in mammalian cells. Surprisingly, however, the greatest sequence diversity (79% identity) was in the less-studied map1-2 gene. We investigated here whether this map1-2 diversity was a general feature of E. ruminantium in different cultured African strains and in organisms from infected sheep. Comparison of MAP1-2s revealed amino acid identities of 75 to 100% (mean of 86%), compared to 84 to 100% (mean of 89%) for MAP1s. Interestingly, MAP1-2s varied independently of MAP1s such that E. ruminantium strains with similar MAP1s had diverse MAP1-2s and vice versa. Different MAP1-2s were found in individual infected sheep. Different regions of a protein may be subjected to different evolutionary forces because of recombination and/or selection, which results in those regions not agreeing with a phylogeny deduced from the whole molecule. This appears to be true for both MAP1 and MAP1-2, where statistical likelihood methods detect heterogeneous evolutionary rates for segments of both molecules. Sera from infected cattle recognized a MAP1-2 variable-region peptide in enzyme-linked immunosorbent assay, but less strongly and consistently than a MAP1 peptide (MAP1B). Heterologous protective immunity may depend on recognition of a complex set of varying OMP epitopes.

Dataset Information

Sequence heterogeneity of the major antigenic protein 1 genes from Cowdria ruminantium isolates from different geographical areas.

Publications

Sequence heterogeneity of the major antigenic protein 1 genes from Cowdria ruminantium isolates from different geographical areas.

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