SnSAG5 is an alternative surface antigen of Sarcocystis neurona strains that is mutually exclusive to SnSAG1

A novel Sarcocystis neurona genotype XIII is associated with severe encephalitis in an unexpectedly broad range of marine mammals from the northeastern Pacific Ocean

“…Three sets of nested surface antigen primers (for use in external and internal PCRs), SnSAG1-5-6, SnSAG3 and SnSAG4 were used, which allowed for S. neurona genotyping based on allele presence at SnSAGs 1, 5 and 6, and polymorphisms at specific nucleotide positions in SnSAG3 and SnSAG4 (Crowdus et al, 2008; Howe et al, 2008; Rejmanek et al, 2010; Wendte et al, 2010b). The SnSAG1-5-6 genes are differentially encoded among S. neurona strains, whereas SnSAG3 and SnSAG4 are polymorphic.…”

“…Sarcocystis neurona is known to possess six major surface antigen genes, SnSAGs 1–6 (Ellison et al, 2002; Hyun et al, 2003; Howe et al, 2005; Crowdus et al, 2008; Wendte et al, 2010b). Analysis for the presence or absence and allelic variation within these genes allows for classification of S. neurona isolates into genotypes or antigen genetic (Ag) types.…”

An update on Sarcocystis neurona infections in animals and equine protozoal myeloencephalitis (EPM)

“…Subsequent immunologic analysis of a collection of 14 S. neurona strains using antiserum against SnSAG1 demonstrated that this surface antigen is not expressed by multiple strains, and the lack of expression was shown to be due to the absence of the SnSAG1 gene (Howe et al, 2008). Those parasite strains that lack SnSAG1 were found to express one of two alternative major surface antigens that were call SnSAG5 and SnSAG6 (Crowdus et al, 2008; Wendte et al, 2010b). While it is conceivable that additional alternative major SnSAG paralogues exist, analysis of much more extensive collections of parasite strains suggest that SnSAG1, SnSAG5, or SnSAG6 will be predominant in the S. neurona strains circulating in nature (Rejmanek et al, 2010 , ; Wendte et al, 2010a).…”

“…Thus far, these ELISAs are all based on the family of related S. neurona merozoite surface antigens (SnSAGs) (Ellison et al, 2002; Howe et al, 2005), which are good serologic targets since they are abundant and immunogenic. Importantly, antigenic diversity has been found among different strains of S. neurona (Crowdus et al, 2008; Howe et al, 2008; Hyun et al, 2003; Marsh et al, 2001b; Wendte et al, 2010b), so all of the SnSAGs are not equally valid for use in serologic assays.…”

“…More critically, the SnSAG1 protein has been shown to be absent from multiple S. neurona isolates (Howe et al, 2008; Hyun et al, 2003; Marsh et al, 2001b), which explains the relatively low accuracy observed with this antigen in independent studies (Hoane et al, 2005; Johnson et al, 2010). An assay that combines SnSAG1 with the two alternative major SnSAGs, SnSAG5 (Crowdus et al, 2008) and SnSAG6 (Wendte et al, 2010b), is presently offered as a stall-side test (Prota, LLC), but no published reports have validated this assay so remains unclear whether the test accurately detects antibodies to S. neurona .…”