Cellular and humoral immune responses associated with protection in sheep vaccinated against Teladorsagia circumcincta

Abstract

Due to increased anthelmintic resistance, complementary methods to drugs are necessary to control gastrointestinal nematodes (GIN). Vaccines are an environmentally-friendly and promising option. In a previous study, a Teladorsagia circumcincta recombinant sub-unit vaccine was administered to two sheep breeds with different levels of resistance against GIN. In the susceptible Canaria Sheep (CS) breed, vaccinates harboured smaller worms with fewer eggs in utero than the control group. Here, we extend this work, by investigating the cellular and humoral immune responses of these two sheep breeds following vaccination and experimental infection with T. circumcincta. In the vaccinated CS group, negative associations between antigen-specific IgA, IgG2 and Globule Leukocytes (GLs) with several parasitological parameters were established as well as a higher CD4+/CD8+ ratio than in control CS animals, suggesting a key role in the protection induced by the vaccine. In the more resistant Canaria Hair Breed (CHB) sheep the vaccine did not significantly impact on the parasitological parameters studied and none of these humoral associations were observed in vaccinated CHB lambs, although CHB had higher proportions of CD4+ and CD8+ T cells within the abomasal lymph nodes, suggesting higher mucosal T cell activation. Each of the component proteins in the vaccine induced an increase in immunoglobulin levels in vaccinated groups of each breed. However, levels of immunoglobulins to only three of the antigens (Tci-MEP-1, Tci-SAA-1, Tci-ASP-1) were negatively correlated with parasitological parameters in the CS breed and they may be, at least partially, responsible for the protective effect of the vaccine in this breed. These data could be useful for improving the current vaccine prototype.

Variability in the Response against Teladorsagia circumcincta in Lambs of Two Canarian Sheep Breeds

“…In contrast to previous experimental GIN infection studies that included older (approximately 6 month-old) animals [16,23], we found no evidence that CHB lambs were more resistant to T. circumcincta than CS lambs at three months of age. However, great individual variability in resistance regarding parasitological parameters was observed within both breeds.…”

“…In conclusion, the lambs that controlled parasitological parameters more efficiently developed protective type-2 immune responses, similar to those developed by adult animals in other studies [23]. Future study designs will confirm the data presented; for example, by creating resistant and susceptible lineages and exploring the dynamics of the immune response with changes in gene expression throughout infection.…”

“…In this regard, a recent comparative study showed that suckling Santa Ines lambs were more resistant than Ile de France lambs due to a strong abomasal cellular immune response when infected with Haemonchus contortus, with significant intra-breed variability [18]. The CHB and the CS breeds have been used previously as models in several studies because of differences in their resistance to H. contortus and T. circumcincta in lambs older than six months of age [16,23]. Moreover, a recent study demonstrated that three -month-old CHB lambs responded to vaccination with recombinant T. circumcincta proteins, with reductions in parasitological variables and involvement of well-characterised anti-GIN immune mechanisms described in adult animals, whereas such differences were not observed in three-month-old CS lambs [29].…”

Perspective Chapter: Exosome-Mediated Pathogen Transmission

“…Proteomic characterization of these EVs and identified several proteins involved in various functions such as structure and metabolism of the parasite. Importantly, it was found that some of these proteins can be bound by two types of antibodies, IgA and IgG, in T. circumcinctainfected sheep suggesting that these proteins may have potential as vaccine targets for the development and production of a vaccine against T. circumcincta infection [27]. Proteomic analysis could identify proteins carried by extracellular vesicles (EVs) released by tapeworms.…”

Antibody response and abomasal histopathology of lambs with haemonchosis during supplementation with medicinal plants and organic selenium

“…Protective host immune responses against GINs are mediated by type 2 immune responses involving the infiltration of eosinophils, globule leukocytes, and plasma cells in the abomasal tissue and an increase in the production of cytokines and parasite-specific antibodies ( McRae et al., 2015 ). These host immune responses play important roles in regulating the damage caused by these parasites and are associated with lower egg production and excretion by adult worms, lower parasitic burden, and shorter female parasites ( Machín et al., 2021 ).…”