Successful vaccines for naturally occurring protozoal diseases of animals should guide human vaccine research. A review of protozoal vaccines and their designs

Abstract

SUMMARYEffective vaccines are available for many protozoal diseases of animals, including vaccines for zoonotic pathogens and for several species of vector-transmitted apicomplexan haemoparasites. In comparison with human diseases, vaccine development for animals has practical advantages such as the ability to perform experiments in the natural host, the option to manufacture some vaccines in vivo, and lower safety requirements. Although it is proper for human vaccines to be held to higher standards, the enduring lack of vaccines for human protozoal diseases is difficult to reconcile with the comparatively immense amount of research funding. Common tactical problems of human protozoal vaccine research include reliance upon adapted rather than natural animal disease models, and an overwhelming emphasis on novel approaches that are usually attempted in replacement of rather than for improvement upon the types of designs used in effective veterinary vaccines. Currently, all effective protozoal vaccines for animals are predicated upon the ability to grow protozoal organisms. Because human protozoal vaccines need to be as effective as animal vaccines, researchers should benefit from a comparison of existing veterinary products and leading experimental vaccine designs. With this in mind, protozoal vaccines are here reviewed.

Antimicrobial Resistance: Its Surveillance, Impact, and Alternative Management Strategies in Dairy Animals

“…HIDATIL EG95, a subunit vaccine, is available for protecting sheep and goats against Echinococcus granulosus ( 85 ). Leish-Tec is one of the commercially available recombinant vaccines against protozoans ( 90 ). Among vectored vaccines, cattle vaccinated with a BCG strain overexpressing the Ag85B antigen (protein found on the bacterial surface) displayed enhanced protective immune responses against Mycobacterium bovis ( 91 ).…”

Paths to a malaria vaccine illuminated by parasite genomics

“…Although there is a precedent for use of live-parasite vaccines to prevent protozoan infections of domestic animals [28] , subunit vaccines containing specific antigens are generally considered more feasible for broad delivery to human populations [4,5] . These may be constructed as recombinant proteins (that are either soluble, or form virus-like particles, or chemically conjugated nanoparticles), long synthetic peptides, recombinant plasmid DNA, or recombinant viral vectors, each potentially offering a product profile that could be incorporated into an Expanded Program for Immunization (EPI) schedule [29] .…”

Limited genetic and antigenic diversity within parasite isolates used in a live vaccine against Theileria parva

“…Live vaccines are available for a number of economically important diseases of farm animals caused by protozoal parasites including Babesia bovis , Theileria parva and Theileria annulata in cattle, Toxoplasma gondii in sheep and Eimeria spp. in poultry (reviewed by McAllister, 2014 ). Extensive efforts to develop alternative, more easily manufactured, vaccines based on use of defined antigens, have met with limited success.…”