Liu ShuXian

Immunization of mice with recombinant Sjc26GST induces a pronounced anti-fecundity effect after experimental infection with Chinese Schistosoma japonicum

We report the cloning, by polymerase chain reaction (PCR), of a cDNA encoding a Schistosoma japonicum (Chinese) 26 kDa glutathione-S-transferase (GST) (Sjc26GST), expression of the cDNA, affinity purification of the recombinant GST and its vaccine efficacy in outbred NIH mice using Freunds as adjuvant. The most striking feature of the vaccination experiments was the pronounced reduction in the number of eggs in the livers and spleens of immunized mice. A relatively low but significant level of protection in terms of reduced worm viability against challenge infection was also observed. Further, the level of anti-Sjc26GST antibody in immunized mice was significantly higher than in control mice at week 6 post-challenge infection. These results closely mirror the protection conferred by immunization of animals with the 28 kDa GST of S. mansoni (Sm28) where a reduction in worm viability, worm fecundity and egg-hatching ability have been reported following challenge with S. mansoni. In terms of developing a vaccine against schistosomiasis japonica, immunization with Sjc26GST can provide two complementary goals in human or animal populations--some reduction in worm burden following exposure to infection or reinfection, and an anti-disease effect through reduction of pathology by a decrease in worm fecundity, with this direct effect also affecting the transmission of S. japonicum.

Anti-fecundity immunity to Schistosoma japonicum induced in Chinese water buffaloes (Bos buffelus) after vaccination with recombinant 26 kDa glutathione-S-transferase (reSjc26GST)

We have shown previously that immunisation of mice and pigs with recombinant 26 kDa GST (reSjc26GST) induces a pronounced anti-fecundity effect after experimental infection with Chinese Schistosoma japonicum. We report here that anti-fecundity immunity can also be induced against reSjc26GST in Chinese water buffaloes (Bos buffelus), important reservoir hosts for S. japonicum in China. Anti-Sjc26GST antibodies were produced in immunised buffaloes and, following challenge with S. japonicum cercariae, a 22.3% reduction in worm numbers was evident in vaccinated when compared with control animals. The anti-fecundity effect was characterised by a significant decrease in faecal egg output and eggs deposited in host tissues with those in the liver and intestine being reduced by about 50%. In addition to the anti-fecundity effect, reSjc26GST reduced by nearly 40% the egg-hatching capacity of S. japonicum eggs into viable miracidia. In terms of vaccination strategy, these effects would combine to diminish pathology in animals immunised with reSjc26GST and reduce transmission of schistosomiasis japonica.

Progress in the development of a vaccine against schistosomiasis in China

Schistosomiasis japonica a zoonotic disease caused by the Asian schistosome or blood fluke Schistosoma japonicum is still recognized as a major public health problem in China and is perhaps the nation’s most important parasitic disease. An estimated 1.5 million people are infected and over 40 million people are at risk for the disease in the Yangtze River valley provinces. Thousands of new cases of acute schistosomiasis have been reported in recent years from endemic areas. A variety of measures have been adopted in an integrated approach to control schistosomiasis japonica in China. These measures rely predominantly on mass chemotherapy with the drug praziquantel; however efforts to control schistosomiasis in China with extensive use of praziquantel administered to infected patients have been thwarted by three major problems. First and foremost high rates of reinfection with schistosomes occur within months following treatment particularly in hyperendemic areas. Second there are potential and proven concerns about emerging praziquantel drug resistance. Third the reservoir of domestic animal hosts including cattle buffaloes pigs and sheep represent a significant source for zoonotic transmission of S. japonicum to humans; these animal reservoirs are generally not targeted for mass chemotherapy. (excerpt)