Immunogenicity and protective efficacy of recombinant Toxocara canis inorganic pyrophosphatase protein

Toxocara canis is a neglected zoonotic nematode that is widely prevalent worldwide. The parasite is of high veterinary and medical importance due to the disease it causes in dog pups and its ability to cause larval migration in humans, affecting internal organs. The most rational approach to contribute to the effective control of infection is considered to be the development of vaccines rather than the treatment of dogs with drugs. The current study identified a homolog (Tc-PYP) of inorganic pyrophosphatases (PPases) in T. canis lineages. Here, the efficacy of rTc-PYP, an adjuvanted form of the protein, was evaluated through immunization studies in a mouse model. It was observed that rTc-PYP immunization induced elevated levels of antigen-specific total IgG, IgG1, IgG2a, and IgG2b responses while not stimulating IgE antibody response. Regarding cytokine responses, rTc-PYP did not change the levels of the Th1 cytokines interferon-gamma and interleukin IL-2. However, it significantly increased the levels of the Th2 cytokines IL-10 and IL-4. Immunization with rTc-PYP resulted in a significant decrease in T. canis L3 larvae migrating to the lungs and liver, with an efficacy of 72.8%. In conclusion, this study demonstrated that immunization with rTc-PYP induced a Th2-mediated immune response and provided high protection against T. canis in mice. It suggests that rTc-PYP could be a promising vaccine candidate for controlling T. canis infection, particularly in the definitive host, dogs.