Congenital infection of rabbits with Schistosoma japonicum and protective immunity of offspring / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Recently congenital infection with Schistosoma japonicum (S. japonicum) has been demonstrated in pigs, rabbits, mice and dogs. We explored the rabbit as an animal model for the congenital infection of schistosomiasis japonica and assessed the effect of a congenital S. japonicum infection on the resistance of rabbit kittens to a postnatal challenge infection.</p><p><b>METHODS</b>Sixteen pregnant New Zealand white rabbits were infected with a single dose of S. japonicum cercariae. The exposed animals were divided into three groups according to the gestation age at the time of infection. Diagnosis of prenatally acquired S. japonicum infection in the rabbit kittens was primarily based on serological tests in combination with parasitological and histopathological findings. Congenitally infected kittens were challenged percutaneously with 100 S. japonicum cercariae to assess the effect of a congenital S. japonicum infection on kitten resistance to a postnatal challenge infection.</p><p><b>RESULTS</b>The overall prevalence of congenital infection in offspring of infected mothers was 20% (12/60). The congenital infection rate in group L (late gestation) was much higher than in group E (early gestation) and group M (mid-gestation) (P <0.05). After a postnatal challenge infection, prenatally infected kittens had a 54.66% worm reduction rate, 41.45% egg reduction rate, and 51.76% granuloma size reduction rate compared to naïve kittens.</p><p><b>CONCLUSIONS</b>This study demonstrates the possibility of congenital infection of S. japonicum in rabbits and the resistance of congenitally infected kittens to a postnatal challenge infection. These results have important implications not only for epidemiological investigations, but also in designing government control programs for schistosomiasis.</p>

Immune responses against Schistosoma japonicum after vaccinating mice with a multivalent DNA vaccine encoding integrated membrane protein Sj23 and cytokine interleukin-12 / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>The vaccination of mice with DNA encoding single candidate antigens has failed to induce significant protection against Schistosoma japonicum (S. japonicum) challenge infections. In this study, we evaluated the feasibility of using a multivalent DNA vaccine which co-expressed S. japonicum integral membrane protein Sj23 and murine cytokine IL-12 to induce protective immune responses.</p><p><b>METHODS</b>The plasmid pVIVO2-IL12-Sj23, a eukaryotic expression vector expressing Sj23 and murine IL-12 simultaneously, was constructed, identified, and tested for expression in vitro. Its ability to protect against S. japonicum challenge infections was analyzed according to worm reduction rate and egg reduction rate after vaccination of BALB/c mice. The serum levels of specific IgG antibody were determined by enzyme-linked-immuno sorbent assay (ELISA) and Western blot analysis. Using cultured spleen cells, IFN-gamma and IL-4 post-stimulation were quantified by ELISA. The phenotypes of splenocyte populations were analyzed by flow cytometry (FCM).</p><p><b>RESULTS</b>The plasmid DNA pVIVO2-IL12-Sj23 was proven to express well in vitro by transient transfection of HEK-293 cells. Immunization resulted in a worm reduction rate of 45.53% and egg reduction rate of 58.35%. ELISA and Western blot analysis indicated that immunized mice generated specific IgG against Sj23. Spleen cells showed significant increases in IFN-gamma but decreases in IL-4. No significant differences in CD4+ and CD8+ subgroup ratios were observed after the challenges.</p><p><b>CONCLUSIONS</b>The multivalent DNA vaccine pVIVO2-IL12-Sj23 is sufficient to elicit moderate but highly significant levels of protective immunity against challenge infections. Cytokine IL-12, as a gene adjuvant, was able to enhance the Th1 responses and, hence, the protective immunity.</p>