Schistosoma mansoni tegument protein Sm29 is able to induce a Th1-type of immune response and protection against parasite infection.
BACKGROUND
Schistosomiasis continues to be a significant public health problem. This disease affects 200 million people worldwide and almost 800 million people are at risk of acquiring the infection. Although vaccine development against this disease has experienced more failures than successes, encouraging results have recently been obtained using membrane-spanning protein antigens from the tegument of Schistosoma mansoni. Our group recently identified Sm29, another antigen that is present at the adult worm tegument surface. In this study, we investigated murine cellular immune responses to recombinant (r) Sm29 and tested this protein as a vaccine candidate.


RESULTS
We first show that Sm29 is located on the surface of adult worms and lung-stage schistosomula through confocal microscopy. Next, immunization of mice with rSm29 engendered 51%, 60% and 50% reduction in adult worm burdens, in intestinal eggs and in liver granuloma counts, respectively (p<0.05). Protective immunity in mice was associated with high titers of specific anti-Sm29 IgG1 and IgG2a and elevated production of IFN-gamma, TNF-alpha and IL-12, a typical Th1 response. Gene expression analysis of worms recovered from rSm29 vaccinated mice relative to worms from control mice revealed a significant (q<0.01) down-regulation of 495 genes and up-regulation of only 22 genes. Among down-regulated genes, many of them encode surface antigens and proteins associated with immune signals, suggesting that under immune attack schistosomes reduce the expression of critical surface proteins.


CONCLUSIONS
This study demonstrates that Sm29 surface protein is a new vaccine candidate against schistosomiasis and suggests that Sm29 vaccination associated with other protective critical surface antigens is the next logical strategy for improving protection.
Cardoso
Fernanda C
FC
Departamento de Bioquímica e Imunologia do Instituto de Ciências Biológicas da Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
Macedo
Gilson C
GC
Gava
Elisandra
E
Kitten
Gregory T
GT
Mati
Vitor L
VL
de Melo
Alan L
AL
Caliari
Marcelo V
MV
Almeida
Giulliana T
GT
Venancio
Thiago M
TM
Verjovski-Almeida
Sergio
S
Oliveira
Sergio C
SC
D000818:Animals; D000909:Antibodies, Helminth / Q000097:blood / Q000276:immunology; D000947:Antigens, Helminth / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology*; D005260:Female; D015801:Helminth Proteins / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology*; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood / Q000276:immunology; D008168:Lung / Q000276:immunology / Q000469:parasitology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D012550:Schistosoma mansoni / Q000235:genetics / Q000254:growth & development / Q000276:immunology*; D012555:Schistosomiasis mansoni / Q000276:immunology* / Q000469:parasitology; D018417:Th1 Cells / Q000276:immunology*; D014612:Vaccines / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology
D000909:Antibodies, Helminth; D000947:Antigens, Helminth; D015801:Helminth Proteins; D007074:Immunoglobulin G; D014612:Vaccines