Radiation-attenuated schistosome vaccination – a brief historical perspective

Abstract

The high level of protection which can be induced by vaccination of a range of hosts, from rodents to primates, with live radiation-attenuated schistosome larvae offers great promise for development of a human schistosome vaccine. Studies of the irradiated vaccine models benefitted from significant funding during the 1970-90s and much was learned concerning the inducers, targets and mechanisms of immunity. Less progress was made in definition of the protective antigens involved. The application of new techniques for identifying membrane and secreted antigens has recently provided new vaccine candidates and a new impetus for schistosome vaccine development. This article is intended as an overview of some of the main lessons learned from the studies of the irradiated vaccines as a backdrop to renewed interest in schistosome vaccine development.

Schistosomiasis vaccines

“…30,31 Vaccination with irradiated cercariae results in the development of various effector responses that can range from Th1-type cellmediated response to parasite-specific antibodies-all of these responses play some role in the immune killing of worms. 29,30,32 In humans, evidence from multiple studies documents an age-acquired resistance to re-infection in older children and adults. 5,[33][34][35] Individuals living in endemic communities display a characteristic left-skewed convex distribution by age of prevalence and intensity of infection for schistosomes.…”

Better Understanding of Anti-Schistosomal Strategies Through Microarray Analysis

“…Vaccination with live radiation attenuated (RA) cercariae can provide high levels of immunity in experimental animal models for all of the major schistosome species of clinical relevance [3]. However, the action of radiation attenuation on the parasite and the response the host has towards the attenuated parasite are not clear.…”

“…This avenue may provide future design strategies leading to the formulation of a targeted recombinant vaccine. One model providing high immunological protection is vaccination with radiation attenuated (RA) parasites [3]. Research characterising the action of RA induced protection have primarily focused on the developmental and migratory patterns of the parasite and the subsequent responses of the host.…”

Sm29, but Not Sm22.6 Retains its Ability to Induce a Protective Immune Response in Mice Previously Exposed to a Schistosoma mansoni Infection

“…The ability of the parasite to evade the host immune system and its complex life cycle make the development of a vaccine against schistososmiasis a difficult task to achieve. But the presence of individuals naturally resistant to Schistosoma mansoni infection in endemic areas [1], the evidence of acquired resistance by constant infection and treatments over the time [2], and the high levels of protection induced by vaccination with irradiated cercariae suggest that developing a vaccine against the parasite is a feasible goal [3]. …”