Screening the Schistosoma mansoni transcriptome for genes differentially expressed in the schistosomulum stage in search for vaccine candidates.
Schistosomiasis affects more than 200 million people worldwide; another 600 million are at risk of infection. The schistosomulum stage is believed to be the target of protective immunity in the attenuated cercaria vaccine model. In an attempt to identify genes up-regulated in the schistosomulum stage in relation to cercaria, we explored the Schistosoma mansoni transcriptome by looking at the relative frequency of reads in EST libraries from both stages. The 400 genes potentially up-regulated in schistosomula were analyzed as to their Gene Ontology categorization, and we have focused on those encoding-predicted proteins with no similarity to proteins of other organisms, assuming they could be parasite-specific proteins important for survival in the host. Up-regulation in schistosomulum relative to cercaria was validated with real-time reverse transcription polymerase chain reaction (RT-PCR) for five out of nine selected genes (56%). We tested their protective potential in mice through immunization with DNA vaccines followed by a parasite challenge. Worm burden reductions of 16-17% were observed for one of them, indicating its protective potential. Our results demonstrate the value and caveats of using stage-associated frequency of ESTs as an indication of differential expression coupled to DNA vaccine screening in the identification of novel proteins to be further investigated as potential vaccine candidates.
Farias
Leonardo P
LP
Centro de Biotecnologia, Instituto Butantan, Av. Vital Brasil 1500, 05503-900 São Paulo, São Paulo, Brazil.
Tararam
Cibele A
CA
Miyasato
Patricia A
PA
Nishiyama
Milton Y
MY
Oliveira
Katia C
KC
Kawano
Toshie
T
Verjovski-Almeida
Sergio
S
Leite
Luciana Cezar de Cerqueira
LC
D000818:Animals; D000947:Antigens, Helminth / Q000096:biosynthesis; D018509:DNA, Helminth / Q000737:chemistry / Q000235:genetics; D020224:Expressed Sequence Tags; D020869:Gene Expression Profiling; D015801:Helminth Proteins / Q000096:biosynthesis; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012550:Schistosoma mansoni / Q000235:genetics* / Q000254:growth & development*; D012555:Schistosomiasis mansoni / Q000517:prevention & control; D017422:Sequence Analysis, DNA; D019444:Vaccines, DNA / Q000008:administration & dosage / Q000276:immunology
D000947:Antigens, Helminth; D018509:DNA, Helminth; D015801:Helminth Proteins; D019444:Vaccines, DNA