Induction of Protective Immunity againstSchistosoma mansonivia DNA Priming and Boosting with the Large Subunit of Calpain (Sm-p80): Adjuvant Effects of Granulocyte-Macrophage Colony-Stimulating Factor and Interleukin-4

Abstract

Considerable morbidity and mortality result from schistosomiasis, an affliction affecting an estimated 200 million people. Although schistosomicidal drugs and other control measures (including public hygiene and snail control) exist, the advent of an efficacious vaccine remains the most potentially powerful means for controlling this disease. We have targeted a vaccine candidate (large subunit of calpain, Sm-p80) because of its consistent immunogenicity, protective potential, and integral role in surface membrane biogenesis of schistosomes. Since surface membrane renewal appears to be one of the major phenomena employed by schistosomes to evade the host's immune system; an immune response directed against Sm-p80 should render the parasite susceptible to immune clearance from the host by both providing a focus of attack and by potentially impairing the membrane repair process. In the present study, we have employed DNA immunization protocols using Sm-p80 with plasmids encoding granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4). Sm-p80 by itself provided 39% protection (P ‫؍‬ <0.0001) against challenge infection in C57BL/6 mice. This protection was increased to 44% (P ‫؍‬ <0.0001) when the plasmid encoding GM-CSF was coadministered with Sm-p80 DNA. Coinjection of plasmid DNA encoding IL-4 with Sm-p80 DNA yielded a protection level of 42% (P ‫؍‬ <0.0001). Statistically, the protection conferred by including GM-CSF, but not IL-4, was significantly greater than that when only Sm-p80 was used. Sm-p80 DNA by itself elicited strong responses that include IgG2A and IgG2B antibody isotypes. The introduction of GM-CSF DNA with Sm-p80 DNA led to distinct increases in total IgG and IgG1 titers, whereas the coadministration of IL-4 DNA with Sm-p80 DNA resulted in a slight elevation of IgG1 and IgG3 titers and in some reduction of IgG2A and IgG2B titers. Our data again indicate that Sm-p80 can be an excellent candidate for a schistosomiasis vaccine.

Characterization of protective immunity induced againstSchistosoma mansonivia DNA priming with the large subunit of calpain (Sm-p80) in the presence of genetic adjuvants

“…Co-injection of plasmid DNA encoding IL-4 with Sm-p80 DNA yielded a protection level of 42 % (Siddiqui et al, 2003b). The protection was found to be 44 % when plasmid encoding GM-CSF was co-administered with Sm-p80 DNA (Siddiqui et al, 2003a). Coinjection of plasmid DNA encoding IL-12 with Sm-p80 DNA yielded a protection level of 45 % (Siddiqui et al, 2003b).…”

“…Furthermore, co-inoculation of Sm-p80 with GM-CSF resulted in augmentation of total IgG and IgG 1 antibody titers, indicating that Th-2 arm of the immune system was also induced. Interestingly, however, IgG 2A titers remained high but IgG 2B titers were reduced (Siddiqui et al, 2003a). Elevation of IgG 2A titers suggested that either GM-CSF was unable to counter the already biased Th-1 type response induced by intramuscular injections of plasmid DNA containing Th-1 promoting Sm-p80-pcDNA3 415 ± 27.9 171 ± 23.2 Sm-p80-pcDNA3 + pORF-mGM-CSF 488 ± 37.9 134 ± 12.1 Sm-p80-pcDNA3 + pORF-mIL-4 400 ± 38.1 245 ± 13.6 Sm-p80-pcDNA3 + pORF-mIL-12 1,071 ± 54.3 43 ± 2.3 Sm-p80-pcDNA3 + pORF-mIL-2 1,415 ± 122.9 46 ± 1.5 et al, 2003b).…”

“…The viability of cells was determined via Trypan Blue, > 80 % of cells were found to be viable. In a 96-well flat-bottom plate, the splenocytes (5 × 10 5 cells/100 µl/well) were stimulated with baculovirus generated Sm-p80 recombinant protein (1.2 µg/ 100 µl/well) (Siddiqui et al, 2003a). ConA was used at a concentration of 0.1 µg/well.…”

DNA Immunization with Na + -K + ATPase ( Sseat-6 ) Induces Protective Immunity to Larval Strongyloides stercoralis in Mice

“…All groups, including the control groups, received plasmid containing the murine GM-CSF sequence. GM-CSF was coadministered with experimental plasmids, because it has been shown to increase the IgG response after DNA immunization (44,49). Mice were immunized intradermally in the ear with 20 g of the antigen DNA/l and 10 g of GM-CSF/l in a total volume of 20 l (10 l/ear) every 2 weeks for a total of six immunizations.…”

Schistosomiasis vaccines

“…At present, to our knowledge, Sm-p80 is the sole schistosome vaccine candidate that has been tested for its prophylactic, antifecundity and therapeutic efficacy in different vaccine formulations and approaches (e.g., naked DNA alone; recombinant protein with adjuvants; and prime with DNA, followed by boosting with protein plus adjuvants) in two experimental animal models (mouse and baboon) of infection and disease. 16,[50][51][52][53][54][55][56][57][58][59][60][61][62] Furthermore, the validity of Sm-p80 as a viable vaccine candidate has been reinforced by the work of five "research groups" who have independently demonstrated reproducible and consistent protective efficacy in mice following challenge infection using calpain or its peptides as an antigen (Nagoya City University Medical School, Nagoya, Japan; 63 [50][51][52][53][54][55][56][57][58][59][60][61][62] ). Sm-p80-based vaccine formulations have three protective effects: worm reduction, antifecundity effect and protection against acute schistosomiasis.…”