Attempts to induce resistance toSchistosoma mansoniandS. haematobium in Kenyan baboons (Papio anubis) using non-specific immunostimulants

Abstract

Non-specific immunostimulants were used in an attempt to protect baboons from infection by schistosomes. Subcutaneous vaccination with cord factor (4.50 mg) and muramyl dipeptide (4.56 mg) 6 days before percutaneous exposure to 3000 Schistosoma haematobium cercariae/baboon (c.p.b.) failed to protect naive baboons: baboons with a 7-month-old, 5000 c.p.b. S. haematobium primary infection had developed too strong a natural immunity to detect any protection attributable to vaccination. Subcutaneous vaccination with 0.4 ml of Bacillus Calmette-Guerin (BCG, 1-8 X 10(8) colony forming units/ml) 4 days before exposure to 1000 c.p.b. S. mansoni gave a significant (38%) reduction in worm load compared with controls. However, vaccination with 0.8 (intramuscular) and 0.2 (intradermal) ml of BCG 11 days before exposure to S. mansoni 800 c.p.b. did not protect naive baboons, nor did it significantly reduce challenge worm recovery from baboons with a 13-week-old, 500 c.p.b. S. mansoni primary infection. Obvious pathology was seen at the site of vaccination in the first but not the second BCG experiment. These results partly support the findings in mice that non-specific macrophage and monocyte activators give partial protection against schistosome infections but they also illustrate that rodents and primates do not necessarily react identically. Hence, findings from rodent models should be extrapolated to man with some caution.

Schistosoma haematobiumin the baboon (Papio anubis): assessment of protection levels against either a single mass challenge or repeated trickle challenges after vaccination with irradiated schistosomula

“…This difference may indicate a failure in the vaccination schedule or the inability of immunized baboons to resist a mass challenge. The mean recovery of cercariae as adult worms in the MCC group (30% ) was quite high (Sturrock et al, 1985) but this group was, of necessity, not entirely homogeneous with the remaining groups, its members having undergone only the minimal quarantine period; all were wild caught and most had heavy Oesophagostomum spp. infections.…”

Effects of immunopotentiating agents on the immune response of rainbow trout, Salmo gair dneri Richardson, to ERM vaccine

“…BCG is a potent, non-specific stimulant of T-, B-and reticuloendothelial cells in certain mammals including man (Sturrock et al, 1985). In fish, the mycobacterial component of adjuvants has been shown to both stimulate (Olivier et al, 1985) and suppress (Munn & Trust, 1983) the immune response, depending upon various factors including dosage and route of administration.…”

Experimental vaccines in animal models for schistosomiasis

“…Furthermore, baboons develop a human-like acute schistosomiasis syndrome after exposure to the cercariae of S. mansoni, manifested by fever, eosinophilia, leucocytosis, cachexia, anorexia, and diarrhea, and these symptoms are coincident with the start of egg deposition in the tissues by newly matured worms (Damian et al 1992;Farah et al 2001;Kariuki and Farah, 2005;Alan et al 2006). Furthermore, baboon as a "protection" model has been utilized successfully by several laboratories to test the efficacy of different schistosome vaccines (Sturrock et al 1985;Boulanger et al 1991b;Soisson et al 1993;Reid et al 1995;Yole et al 1996;Kanamura et al 2002;Kariuki et al 2004;Kariuki and Farah, 2005;Siddiqui et al 2005b;Kariuki et al 2006). For example, immunization of baboons with Sm28GST in the presence of alum resulted in protection from a reduction from 0% to 80% (mean=38%) in the number of parasites and a 33% decrease in female fecundity (Boulanger et al 1991b).…”