Schistosomiasis, also known as bilharzia, is a disease caused by parasitic worms. Infection occurs when your skin comes in contact with contaminated freshwater in which certain types of snails that carry schistosomes are living.
Freshwater becomes contaminated by Schistosoma eggs when infected people urinate or defecate in the water. The eggs hatch, and if certain types of freshwater snails are present in the water, the parasites develop and multiply inside the snails. The parasite leaves the snail and enters the water where it can survive for about 48 hours. Schistosoma parasites can penetrate the skin of persons who are wading, swimming, bathing, or washing in contaminated water. Within several weeks, parasite mature into adult worms, residing in the blood vessels of the body where the females produce eggs. Some of the eggs travel to the bladder or intestine and are passed into the urine or stool. Within days after becoming infected, you may develop a rash or itchy skin. Fever, chills, cough, and muscle aches can begin within 1-2 months of infection. Most people have no symptoms at this early phase of infection.
When adult worms are present, the eggs that are produced usually travel to the intestine, liver or bladder, causing inflammation or scarring. Children who are repeatedly infected can develop anemia, malnutrition, and learning difficulties. After years of infection, the parasite can also damage the liver, intestine, lungs, and bladder. Rarely, eggs are found in the brain or spinal cord and can cause seizures, paralysis, or spinal cord inflammation.
Symptoms of schistosomiasis are caused by the body's reaction to the eggs produced by worms, not by the worms themselves (CDC - Schistosomiasis).
II. Vaccine Related Pathogen Genes
1. calpain
Gene Name :
calpain
Sequence Strain (Species/Organism) :
Schistosoma mansoni strain Puerto Rico
Protein Note :
Cathepsin B group; composed of cathepsin B and similar proteins, including tubulointerstitial nephritis antigen (TIN-Ag). Cathepsin B is a lysosomal papain-like cysteine peptidase which is expressed in all tissues and functions primarily as an...; cd02620
Protein Note :
Copper/zinc superoxide dismutase (SOD). superoxide dismutases catalyse the conversion of superoxide radicals to molecular oxygen. Three evolutionarily distinct families of SODs are known, of which the copper/zinc-binding family is one. Defects in the...; cd00305
Efficacy:
CT-SOD showed the highest level of protection out of all vaccines tested (54%). Two immunizations resulted in significant reduction of worm burden compared to control groups (Shalaby et al., 2003).
2. S. mansoni DNA vaccine pcDNA/GPXbb encoding glutathione-S-peroxidase, GPX
Efficacy:
For the regimens involving GPXbb, immunization with DNA vaccination alone resulted in protection of 44%, but the prime-boost (boost of recombinant vaccinia virus/GPXbb) resulted in 85% worm burden reduction (Shalaby et al., 2003).
3. S. mansoni DNA vaccine Sm-p80-pcDNA3 encoding the large subunit of S. mansoni calpain
Efficacy:
Mice immunized with Sm-p80-pcDNA3 showed statistically significant 39% reduction in worm burden when compared with mice which received only pcDNA3. Similarly, mice immunized with Sm-p80-pcDNA3 and co-injected with pORF-mIL-2 exhibited 57% reduction (P≤0.0001) in the number of parasites when compared with the group of mice receiving only pcDNA3 and pORF-mIL-2. Also, when mice were primed with Sm-p80-pcDNA3 in the presence of pORF-mIL-12, they contained 45% less number of parasites (P≤0.0001) compared to the group of mice which were immunized with pcDNA3 alone (Siddiqui et al., 2003).
4. S. mansoni DNA vaccine Sm23-pcDNA encoding Sm23
Efficacy:
The Sm23-pcDNA vaccine provided statistically significant levels of protection against challenge infection (21-44%, P<0.001-0.02) (Da'dara et al., 2001).
2. Da'dara et al., 2001: Da'dara AA, Skelly PJ, Wang MM, Harn DA. Immunization with plasmid DNA encoding the integral membrane protein, Sm23, elicits a protective immune response against schistosome infection in mice. Vaccine. 2001; 20(3-4); 359-369. [PubMed: 11672898].
3. Mossallam et al., 2015: Mossallam SF, Amer EI, Ewaisha RE, Khalil AM, Aboushleib HM, Bahey-El-Din M. Fusion protein comprised of the two schistosomal antigens, Sm14 and Sm29, provides significant protection against Schistosoma mansoni in murine infection model. BMC infectious diseases. 2015; 15; 147. [PubMed: 25887456].
4. Shalaby et al., 2003: Shalaby KA, Yin L, Thakur A, Christen L, Niles EG, LoVerde PT. Protection against Schistosoma mansoni utilizing DNA vaccination with genes encoding Cu/Zn cytosolic superoxide dismutase, signal peptide-containing superoxide dismutase and glutathione peroxidase enzymes. Vaccine. 2003; 22(1); 130-136. [PubMed: 14604580].
5. Siddiqui et al., 2003: Siddiqui AA, Phillips T, Charest H, Podesta RB, Quinlin ML, Pinkston JR, Lloyd JD, Pompa J, Villalovos RM, Paz M. Enhancement of Sm-p80 (large subunit of calpain) induced protective immunity against Schistosoma mansoni through co-delivery of interleukin-2 and interleukin-12 in a DNA vaccine formulation. Vaccine. 2003; 21(21-22); 2882-2889. [PubMed: 12798631].
6. Tallima et al., 2017: Tallima H, Dvo?ák J, Kareem S, Abou El Dahab M, Abdel Aziz N, Dalton JP, El Ridi R. Protective immune responses against Schistosoma mansoni infection by immunization with functionally active gut-derived cysteine peptidases alone and in combination with glyceraldehyde 3-phosphate dehydrogenase. PLoS neglected tropical diseases. 2017; 11(3); e0005443. [PubMed: 28346516].
