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

Exploring the transcriptomic changes underlying recombinant vaccine efficacy against Teladorsagia circumcincta in 3-month-old lambs

Teladorsagia circumcincta is an abomasal parasitic nematode that can cause serious issues in small ruminant production, which are aggravated by drug resistance. Vaccines have been suggested as a feasible, long-lasting alternative for control since adaptation to the host's immune mechanisms by helminths develops at a much slower pace than anthelmintic resistance. Recently, a T. circumcincta recombinant subunit vaccine yielded over a 60% reduction in egg excretion and worm burden and induced strong humoral and cellular anti-helminth responses in vaccinated 3-month-old Canaria Hair Breed (CHB) lambs, but Canaria Sheep (CS) of a similar age were not protected by the vaccine. Here, we compared the transcriptomic profiles in the abomasal lymph nodes of such 3-month-old CHB and CS vaccinates 40 days after infection with T. circumcincta to understand differences in responsiveness at the molecular level. In the CS, differentially expressed genes (DEG) identified were related to general immunity processes such as antigen presentation or antimicrobial proteins and down-regulation of inflammation and immune response through regulatory T cell-associated genes. However, upregulated genes in CHB vaccinates were associated with type-2 oriented immune responses, i.e., immunoglobulin production, activation of eosinophils, as well as tissue structure and wound repair-related genes and protein metabolism pathways such as DNA and RNA processing. These results highlight potentially more optimal timing and orientation of immune responses in CHB sheep compared to CS associated with vaccine-induced protection. The data obtained in this study thus deepens our understanding of variations in responsiveness to vaccination in young lamb and provides insights for vaccine refinement strategies.

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

We evaluated the effects of dietary supplementation with medicinal plants (Herbmix) or organic selenium (Selplex) on the immune responses and histopathology of lambs infected with Haemonchus contortus. Twenty-seven lambs were infected and reinfected with approximately 11,000 third-stage larvae of H. contortus during the experiment (on days 0, 49 and 77). Lambs were divided into two supplemented experimental groups (Herbmix and Selplex) and unsupplemented group (Control). The abomasal worm counts at necropsy on day 119 were lower for Herbmix (4230) and Selplex group (3220) than to the Control (6613) which resulted in 51.3% and 36.0% of reduction, respectively. The mean length of adult female worms was in the order Control > Herbmix > Selplex (2.1, 2.08, and 2.01 cm, respectively). The specific IgG response against adults was significantly affected by time (P < 0.001). Serum-specific and total mucus levels of IgA in the Herbmix group were highest on day 15. Mean levels of serum IgM against adults were influenced by treatment (P = 0.048) and time (P < 0.001). The Herbmix group had strong local inflammation in the abomasal tissue, with the formation of lymphoid aggregates and the infiltration of immune cells, but the tissues of the Selplex group had higher numbers of eosinophils, globule leukocytes, and plasma cells. The lymph nodes of each animal had reactive follicular hyperplasia due to the infection. Dietary nutritional supplementation with a mixture of medicinal plants or organic selenium could improve local immune responses and thus enhance the resistance of animals to this parasitic infection.

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

The increasing resistance to anthelmintics has necessitated the exploration of alternative control strategies of gastrointestinal nematode (GIN) infections. A sustainable option is genetic selection based on differences in susceptibility to GIN infection between and within breeds of sheep. Here, three-month-old Canaria Hair breed (GIN-resistant) and Canaria Sheep breed (GIN-susceptible) showed no significant between-breed differences after trickle infection with Teladorsagia circumcincta, whereas considerable individual variability was found in both breeds. Next, data from lambs of both breeds were used to explore the relationships between parasitological variables and T. circumcincta-specific IgA levels, local immune cell populations, and abomasal lymph node gene expression to understand the possible mechanisms underlying resistance. Mucosal IgA levels as well as numbers of globular leukocytes and MHC-II⁺ cells were associated with protection. Analysis of lymph node gene expression revealed the associations between lower parasite numbers and cumulative fecal egg counts and several immune pathways, such as leukocyte cell adhesion, activation and differentiation of T cells, in particular CD4⁺ and IL-4 production. The data obtained here may inform on the relationship between phenotypic resistance variability and protective responses at the humoral, cellular, and transcriptomic levels, thus contributing to identifying immune responses in young lambs that could be used as markers for selection.

In vitro characterization of Haemonchus contortus trehalose-6-phosphate phosphatase and its immunomodulatory effects on peripheral blood mononuclear cells (PBMCs)

Background

Trehalose-6-phosphate phosphatase (TPP6) is a key enzyme in the trehalose biosynthesis pathway. The accumulation of TPP6 inside the body is harmful to the pathogen, but almost nothing is currently known about the function of TPP6 from Haemonchus contortus (CRE-GOB-1).

Methods

The H. contortus CRE-GOB-1 (HcGOB) gene was cloned and recombinant protein of GOB (rHcGOB) was expressed; transcription of the HcGOB gene at different developmental stages of H. contortus was then studied. The spatial expression pattern of the HcGOB gene in adult female and male worms was determined by both quantitative real-time PCR (qPCR) and immunofluorescence. The binding of the rHcGOB protein to goat PBMCs was assessed by immunofluorescence assay. The immunomodulatory impacts of rHcGOB on cell proliferation, nitric oxide generation and cytokine secretion were assessed by co-culture of rHcGOB protein with goat PBMCs.

Results

The HcGOB protein was transcribed in eggs, infective third-stage larvae (iL3s) and adults of H. contortus, with the highest transcript levels found in the egg stage. The transcript levels were significantly elevated in iL3s after manual desheathing. HcGOB was widely distributed in adult worms where it was mainly localized in the gut and gonads. rHcGOB was observed to bind to PBMCs and also to be recognized by sera collected from a goat infected with H. contortus. rHcGOB significantly activated the interleukin-10/transforming growth factor β/signal transducer and activator of transcription 3 (IL-10/TGF-β/STAT3) pathway in PBMCs while suppressing the transcription and expression of IL-4 and IL-17.

Conclusions

These results suggest that the HcGOB gene plays an important role in the development, parasitism and reproduction of H. contortus. The rHcGOB protein affected the immunomodulatory function of PBMCs in the in vitro study, suggesting that this protein would be a promising vaccine target.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-05115-4.