VIOLIN: Vaccine Investigation and Online Information Network

Sarcocystis neurona

Table of Contents

General Information
Vaccine Related Pathogen Genes
1. SAG1 (Protective antigen)
2. SAG1 (Protective antigen)
3. SAG5 (Protective antigen)
Vaccine Information
1. Epm vaccine
2. S. neurona SAG1 Protein Vaccine
References

I. General Information

1. NCBI Taxonomy ID:

42890

2. Disease:

Equine protozoal myeloencephalitis

3. Introduction

Sarcocystis neurona is the most common cause of equine protozoal myeloencephalitis (EPM) in horses in America. It is a single celled parasite belonging to the group called coccidia (Apicomplexa: Sarcocystidae) with opossums as the definitive hosts and a variety of mammals as aberrant or natural intermediate hosts . Only asexual stages have been identified in the aberrant intermediate hosts, and they are confined to the brain and spinal cord, and any part of the central nervous system (CNS) may be affected. In histologic sections of CNS, individual merozoites are about 3-5 um long and contain a single, centrally located vesicular nucleus. The sarcocysts are microscopic (~700 um long) with a 1-3 um thick sarcocyst wall. The bradyzoites are slender and tiny (~ 5 um long). Sarcocystis neurona sporocysts from opossum faeces are ~ 10 x 8 um in size (USDA Agricultural Research Service: Sarcocystis neurona).

4. Microbial Pathogenesis

The pathogenesis of EPM is not clear because the complete life cycle is unknown. Sarcocystis neurona can parasitize all regions of the CNS, from the anterior cerebrum to the end of the spinal cord. Sarcocystis neurona schizonts and merozoites are found in neurons, mononuclear cells, glial cells, and perhaps other neural cells (USDA Agricultural Research Service: Sarcocystis neurona).

5. Host Ranges and Animal Models

Opossums (Didelphis virginiana, D. albiventris) are its definitive (reservoir) hosts and excrete oocysts and sporocysts (environmentally resistant stage)in their feces. Raccoons, armadillos, sea otters, skunks, cats and possibly other mammals are intermediate hosts (USDA Agricultural Research Service: Sarcocystis neurona).

6. Host Protective Immunity

Cell mediated immunity is an important component of controlling this intracellular parasite (Marsh et al., 2004).

II. Vaccine Related Pathogen Genes

1. SAG1

Gene Name : SAG1
Sequence Strain (Species/Organism) : Sarcocystis neurona 3106
VO ID : VO_0011253
NCBI Protein GI : 295682690
Other Database IDs : CDD:252367
Taxonomy ID : 42890
Gene Strand (Orientation) : ?
Protein Name : surface antigen 1
Protein pI : 7.22
Protein Weight : 26504.924
Protein Length : 333
Protein Note : SRS domain; pfam04092

Protein Sequence : Show Sequence

>ADG26774.1 surface antigen 1 [Sarcocystis neurona]
MTRAVLLTFLTLCSARVSLVRAGAPPQATCANGETTVTKLGSSGALRIHCPNNFRLAPRAGNDAGQMQVY
ATAVAENPVNIRDVLPGASYLSVQNVPTLTVPQLPAKATSVFFHCQQQPDNQCFIQVEVAPAPRLGPNTC
AALQSTIAFEVQQANETAVFSCGEGLAVFPQGSKALDEACSKEQALPSGAALAPKDGGLHLGFPQLPQQA
MKICYICTNGGVQAEAAQRCEVRISVAANPDGSVPGANGAASXGAAARSAXALGLALVAGAFLHFC

Molecule Role : Protective antigen
Molecule Role Annotation : Horses were vaccinated with adjuvanted recombinant SnSAG1 (rSnSAG1)and 5 control (sham vaccinated) horses were vaccinated with adjuvant only. The effect of vaccination with rSnSAG1 on in vivo infection by S. neurona was evaluated by challenging all the horses with S. neurona merozoites. The study showed that vaccination with rSnSAG-1 produced antibodies in horses that neutralized merozoites when tested by in vitro culture and significantly reduced clinical signs demonstrated by in vivo challenge (Ellison and Witonsky, 2009).
Related Vaccine(s): S. neurona SAG1 Protein Vaccine

2. SAG1

Gene Name : SAG1
Sequence Strain (Species/Organism) : Sarcocystis neurona
NCBI Protein GI : AAO41732
Taxonomy ID : 42890
Protein Name : merozoite surface antigen SAG1
Protein pI : 7.56
Protein Weight : 26619.054
Protein Length : 346
Protein Note : corresponds to mRNA found in GenBank Accession Number AY245695

Protein Sequence : Show Sequence

>AAO41732.1 merozoite surface antigen SAG1 [Sarcocystis neurona]
MTRAVLLTFLTLCSARVSLVRAGAPPQATCANGETTVTKLGSSGALRIHCPNNFRLAPRAGNDAGQMQVY
ATAVAENPVNIRDVLPGASYLSVQNVPTLTVPQLPAKATSVFFHCQQQPDNQCFIQVEVAPAPRLGPNTC
AALQSTIAFEVQQANETAVFSCGEGLAVFPQGSKALDEACSKEQALPSGAALAPKDGGLHLGFPQLPQQA
MKICYICTNGGVQAEAAQRCEVRISVAANPDGSVPGANGAASXGAAARSAXALGLALVAGAFLHFC

Molecule Role : Protective antigen
Molecule Role Annotation : (Elsheikha and Mansfield, 2004)

3. SAG5

Gene Name : SAG5
Sequence Strain (Species/Organism) : Sarcocystis neurona
NCBI Protein GI : ABD47681
Other Database IDs : CDD:282012
Taxonomy ID : 42890
Protein Name : surface antigen 5
Protein pI : 5.78
Protein Weight : 26623.63
Protein Length : 336
Protein Note : SRS domain; pfam04092

Protein Sequence : Show Sequence

>ABD47681.1 surface antigen 5 [Sarcocystis neurona]
MTRAVLLTILTLCSARVSFVNAGGARQATCEEGQTTATKLENPGVLQLQCPARYQLNPAPAADANEGMQV
FTTAAVGNAVALQGVLPGATYVRAPNGAGATLTIPQLPPKAASVFIQCQQQGQQGQCFIEVQVAGSPRLG
PNTCAAVQSRIDFEIRAQNEAAVFSCGAGRAPFPQALDDACSKEQSLPSGVALAPKDAGSFQLGFPQLPQ
NPLKICYICTEGGQRVDAADQRCEVHIAVAGAEAGGPTGPTGGASVGPAARSASALVLAVVAAGFFHFW

Molecule Role : Protective antigen
Molecule Role Annotation : (Crowdus et al., 2008)

III. Vaccine Information

1. Epm vaccine

a. Tradename:

Epm vaccine

b. Manufacturer:

Fort Dodge

c. Vaccine Ontology ID:

VO_0000835

d. Type:

Inactivated or "killed" vaccine

e. Status:

Licensed

f. Host Species for Licensed Use:

Horse

g. Immunization Route

Intramuscular injection (i.m.)

h. Description

In vitro-cultured merozoites, chemically inactivated(Marsh et al., 2004)

2. S. neurona SAG1 Protein Vaccine

a. Vaccine Ontology ID:

VO_0004042

b. Type:

Subunit vaccine

c. Status:

Research

d. Gene Engineering of SAG1

Type: Recombinant protein preparation
Description:
Detailed Gene Information: Click here.

e. Adjuvant:

VO ID: VO_0001273

f. Immunization Route

Intramuscular injection (i.m.)

g. Horse Response

Vaccination Protocol: The horses were vaccinated on days 0 and 21 with 1 mL adjuvanted (Polygen; MVP Laboratories, Omaha, Nebraska, USA) rSnSAG1 (50 μg) or 1 mL adjuvant alone by IM injection in the left side of the neck (Ellison and Witonsky, 2009).
Challenge Protocol: Horses in all groups were challenged on study day 36 with S. neurona merozoites (Ellison and Witonsky, 2009).
Efficacy: Vaccination with rSnSAG-1 produced antibodies in horses that neutralized merozoites when tested by in vitro culture and significantly reduced clinical signs demonstrated by in vivo challenge (Ellison and Witonsky, 2009).

IV. References

1. Crowdus et al., 2008: Crowdus CA, Marsh AE, Saville WJ, Lindsay DS, Dubey JP, Granstrom DE, Howe DK. SnSAG5 is an alternative surface antigen of Sarcocystis neurona strains that is mutually exclusive to SnSAG1. Veterinary parasitology. 2008; 158(1-2); 36-43. [PubMed: 18829171].

2. Ellison and Witonsky, 2009: Ellison S, Witonsky S. Evidence that antibodies against recombinant SnSAG1 of Sarcocystis neurona merozoites are involved in infection and immunity in equine protozoal myeloencephalitis. Canadian journal of veterinary research = Revue canadienne de recherche veterinaire. 2009; 73(3); 176-183. [PubMed: 19794889].

3. Elsheikha and Mansfield, 2004: Elsheikha HM, Mansfield LS. Sarcocystis neurona major surface antigen gene 1 (SAG1) shows evidence of having evolved under positive selection pressure. Parasitology research. 2004; 94(6); 452-459. [PubMed: 15517384].

4. Marsh et al., 2004: Marsh AE, Lakritz J, Johnson PJ, Miller MA, Chiang YW, Chu HJ. Evaluation of immune responses in horses immunized using a killed Sarcocystis neurona vaccine. Veterinary therapeutics : research in applied veterinary medicine. 2004; 5(1); 34-42. [PubMed: 15150728].

5. USDA Agricultural Research Service: Sarcocystis neurona: EPM/Sarcocystis neuorna [http://www.ars.usda.gov/Main/docs.htm?docid=11028]