Abstract
A gene family of surface antigens is expressed by merozoites of Sarcocystis neurona, the primary cause of equine protozoal myeloencephalitis (EPM). These surface proteins, designated SnSAGs, are immunodominant and therefore excellent candidates for development of EPM diagnostics or vaccines. Prior work had identified an EPM isolate lacking the major surface antigen SnSAG1, thus suggesting there may be some diversity in the SnSAGs expressed by different S. neurona isolates. Therefore, a bioinformatic, molecular and immunological study was conducted to assess conservation of the SnSAGs. Examination of an expressed sequence tag (EST) database revealed several notable SnSAG polymorphisms. In particular, the EST information implied that the EPM strain SN4 lacked the major surface antigen SnSAG1. The absence of this surface antigen from the SN4 strain was confirmed by both Western blot and Southern blot. To evaluate SnSAG polymorphisms in the S. neurona population, 14 strains were examined by Western blots using monospecific polyclonal antibodies against the four described SnSAGs. The results of these analyses demonstrated that SnSAG2, SnSAG3, and SnSAG4 are present in all 14 S. neurona strains tested, although some variance in SnSAG4 was observed. Importantly, SnSAG1 was not detected in seven of the strains, which included isolates from four cases of EPM and a case of fatal meningoencephalitis in a sea otter. Genetic analyses by PCR using gene-specific primers confirmed the absence of the SnSAG1 locus in six of these seven strains. Collectively, the data indicated that there is heterogeneity in the surface antigen composition of different S. neurona isolates, which is an important consideration for development of serological tests and prospective vaccines for EPM. Furthermore, the diversity reported herein likely extends to other phenotypes, such as strain virulence, and may have implications for the phylogeny of the various Sarcocystis spp. that undergo sexual stages of their life cycle in opossums.
Original language | English |
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Pages (from-to) | 623-631 |
Number of pages | 9 |
Journal | International Journal for Parasitology |
Volume | 38 |
Issue number | 6 |
DOIs | |
State | Published - May 2008 |
Bibliographical note
Funding Information:Funding for this research was provided by the Amerman Family Foundation, Fort Dodge Animal Health and gifts from various donors. Published as Kentucky Agricultural Experiment Station article number 07-14-064.
Funding
Funding for this research was provided by the Amerman Family Foundation, Fort Dodge Animal Health and gifts from various donors. Published as Kentucky Agricultural Experiment Station article number 07-14-064.
Funders | Funder number |
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Amerman Family Foundation |
Keywords
- Apicomplexa
- Diagnosis
- Equine protozoal myeloencephalitis
- Surface antigen polymorphism
- Vaccine
ASJC Scopus subject areas
- Parasitology
- Infectious Diseases