| Schistosomiasis is one of major public health problems in China, which severely jeopardize people's health and hamper the socio-economic development in epidemic areas. The repeated large-scale chemotherapy of praziquantel can not block re-infection of schistosome, and probably cause drug resistance. Therefore, the development of vaccine has been concerned as a long-term and effective measure for schistosomiasis control in recent decades. Following the completion of the genome working drafts of schistosoma japonicum, vaccine researches have entered a new era of post-genome with numerous data obtained from spectrums of various genes and proteins expression. These data contribute to the comprehensive understanding of schistosome's development and maturation, immune evasion, and invertebrate evolution, as well as identification of new potential vaccine candidates. Currently, a few hopeful vaccine candidates have been cloned and expressed including enzymes, myosin, membrane-related proteins, calcium-related proteins, mitochondrion-related proteins, signal peptide and sex-related proteins. Howerver, animal experiments indicated that the prevention effect of these candidates was not practical with 20%-40% of worm reduction rate and 30-70% of egg reduction rate, which can not meet the need of field work for schistsomiasis control due to the low protection rate. Hence, it is necessary to further identify new vaccine candidate antigens.Nicotinamide phosphoribosyl transferase (NAMPT), also called pre-B cell colony-enchancing factor (PBEF), is a rate-limiting enzyme for the synthesis of Nicotinamide adenine dinucleotide (NAD), which is a classic coenzyme of redox reaction in cells and has general biological functions. In addition, NAMPT can regulate the cells'growth, proliferation and differentiation, and improve the glucose absorbance of cells. Interleukin-16 (IL-16) is also called lymphocyte chemoattractant factor (LCF) due to the fact that it can induce human and rat CD4+T cells to migrate for immune response. IL-16 precursor is composed of 631 amino acids without biological activity, which is processed to secreted IL-16 monomer in cytoplasm. The tetramer structure formed by IL-16 monomer has biological functions of stimulating cell proliferation, growth and differentiation and inhibiting HIV reproduction. Nicotinamide phosphoribosyl transferase gene and interleukin-16 gene of Schistosoma japonium (SjNAMPT and SjIL-16) are two new ones identified in Schistosoma japonium. The study about SjNAMPT and SjIL-16 has not reported up to now at home and abroad. This study predicted the structure and functions of SjNAMPT and SjIL-16 proteins by using bioinformatics and cloned and expressed two genes by molecular biotechnology. We also analyzed the transcriptional levels of the two genes at different development stages of Schistosoma japonicum and their coded proteins' immunogenicity, and evaluated the diagnostic efficient and immuno-protective effect by ELISA and animal experiments, respectively.This study successfully cloned and expressed SjNAMPT and SjIL-16 genes and obtained the proteins in the form of insoluble inclusion bodies. The results of the transcript specificity indicated that both of SjNAMPT and SjIL-16 genes were specific expression genes of Schistosoma japonicum. SjNAMPT gene did not transcribe in the egg and the female, but the transcription levels in the miracidium, the sporocyst, the cercaria, the schistosomula, the paring adult and the male were relative high; The significant difference of transcription level in the male and female showed that the gene probably is a sex-related gene. SjIL-16 gene did not transcribe or had low level of transcription at early stages of schistosome, but had high level transcription in schistosomula, the paring adult and the male, which indicated the gene transcript probably was regulated by the development mechanism of Schistosoma japonicum and had relationship with the host-dependent development and maturation. Also, SjIL-16 is a sex-related gene due to the transcription difference in the male and the female. The results of Western blotting of SjNAMPT and SjIL-16 proteins indicated that the both had certain immunogenicity, and might be the vaccine candidates for schistsomiasis control. The ELISA results showed that the sensitivities and the specificities of SjNAMPT and SjIL-16 proteins were 56.0%,60.0% and 94.4%,95.4% respectively. According to the results of animal protective experiments, the worm reduction rates of SjNAMPT and SjIL-16 proteins were 19.5% and 20.7%, respectively, and the fecal egg reduction rates of the proteins were 24.0% and 18.0%, which show that SjNAMPT and SjIL-16 induced a certain immuno-protectivity. |
PDF Full Text Request