Single nucleotide polymorphisms from candidate genes associated with nematode resistance and resilience in Corriedale and Pampinta sheep in Argentina.

Selective breeding of genetically resistant animals is considered a promising strategy to face the problem of nematode resistance to anthelmintics and mitigate concerns about the presence of chemical residues in animal food products and the environment. Gastrointestinal nematode resistance is a complex, multifactorial trait related to host immunity. However, the mechanisms underlying host resistance and response to infection remain to be fully elucidated. In this context, the objective of this study was to provide insight into the chromosomal regions determining nematode resistance and resilience in Corriedale and resistance in Pampinta sheep breeds. A total of 170 single nucleotide polymorphisms (SNP) from 76 candidate genes for immune response were studied in 624 Corriedale and 304 Pampinta animals. Lambs underwent artificial or natural challenges with infective larvae mainly from Haemonchus contortus. Fecal egg counts, estimated breeding values for fecal egg counts, and rate of packed cell volume change and FAMACHA© score change over the challenge were used, when available, as indicators of host parasite resistance or resilience. Phenotype-genotype association studies were conducted and significance values obtained were adjusted for multiple testing errors. Eight SNPs, located on OARs 3, 6, 12, and 20, reached significance in Corriedale sheep under artificial challenge. Those SNP represent allelic variants from the MHC-Ovine Lymphocyte Antigen-DRA, two C-type lectin domain families, the Interleukin 2 receptor ß, the Toll-like receptor 10, the Mannan binding lectin serine peptidase 2, and the NLR family, CARD domain containing 4 genes. On Pampinta lambs under natural challenge, we found three significant SNPs, located in the TIMP metallopeptidase inhibitor 3, the FBJ murine osteosarcoma viral oncogene homolog, and the Interleukin 20 receptor alpha genes, on OARs 3, 7, and 8, respectively. The results obtained herein confirm genomic regions previously reported as associated with nematode resistance in other sheep breeds, reinforcing their role in host response to parasites. These findings contribute to gain knowledge on parasite resistance and resilience in Corriedale sheep and report for the first time SNPs associated with resistance to gastrointestinal parasite infections in Pampinta breed.

Prevalence and Genotyping of Echinococcus Species from Livestock in Kajiado County, Kenya.

Cystic Echinococcosis (CE) is a widespread neglected zoonotic disease and is caused by the larval stage of the dog tapeworm Echinococcus granulosus sensu lato. CE is more frequent in livestock-rearing areas and where people live a nomadic or seminomadic lifestyle such as in Kajiado County, Kenya. There is limited data on CE disease situation in the county of Maasailand; the present study, therefore, reports on the prevalence of CE in cattle, sheep, and goats and their relative importance in CE transmission in Kajiado County. In total, 1,486 livestock (388 cattle, 625 sheep, and 473 goats) slaughtered in two abattoirs were examined for the presence of hydatid cysts in various organs. Cyst isolates were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) of the NADH dehydrogenase subunit 1 gene (nad1). The overall prevalence of CE was 14.8% (220/1486), while prevalence per livestock species was 15.2% (72/473) in goats, 14.9% (93/625) in sheep, and 14.2% (55/388) in cattle. Out of the 421 cysts isolated, 389 cysts were successfully characterized to be either E. granulosus sensu stricto (s. s.), 356/389 (91.5%), E. canadensis (G6/7), 26/389 (6.7%), or E. ortleppi, 7/389 (1.8%). This record confirms predominance of E. granulosus s. s. in Maasailand and other parts of Kenya, while the importance of E. ortleppi and E. canadensis (G6/7) to the general CE burden in Maasailand might be higher than previously thought. More so, a higher infection pressure for humans by E. granulosus s. s. based on its abundance could be speculated. The study sheds significant light on CE situation in livestock in the nomadic/seminomadic society of the Maasai in Kajiado County and provides good bases to investigate human CE in the area.

Application of small RNA technology for improved control of parasitic helminths.

Over the last decade microRNAs (miRNAs) and small interfering RNAs (siRNAs) have emerged as important regulators of post-transcriptional gene expression. miRNAs are short, non-coding RNAs that regulate a variety of processes including cancer, organ development and immune function. This class of small RNAs bind with partial complementarity to their target mRNA sequences, most often in the 3'UTR, to negatively regulate gene expression. In parasitic helminths, miRNAs are being increasingly studied for their potential roles in development and host-parasite interactions. The availability of genome data, combined with small RNA sequencing, has paved the way to profile miRNAs expressed at particular developmental stages for many parasitic helminths. While some miRNAs are conserved across species, others appear to be unique to specific parasites, suggesting important roles in adaptation and survival in the host environment. Some miRNAs are released from parasites, in exosomes or in protein complexes, and the potential effects of these on host immune function are being increasingly studied. In addition, release of miRNAs from schistosome and filarial parasites into host plasma can be exploited for the development of specific and sensitive diagnostic biomarkers of infection. Interfering with miRNA function, as well as silencing key components of the pathways they regulate, will progress our understanding of parasite development and provide a novel approach to therapeutic control. RNA interference (RNAi) by siRNAs has proven to be inconsistent in parasitic nematodes. However, the recent successes reported for schistosome and liver fluke RNAi, encourage further efforts to enhance delivery of RNA and improve in vitro culture systems and assays to monitor phenotypic effects in nematodes. These improvements are important for the establishment of reliable functional genomic platforms for novel drug and vaccine development. In this review we focus on the important roles of miRNAs and siRNAs in post-transcriptional gene regulation in veterinary parasitic helminths and the potential value of these in parasite diagnosis and control.

Antibody-mediated trapping of helminth larvae requires CD11b and Fcγ receptor I.

Infections with intestinal helminths severely impact on human and veterinary health, particularly through the damage that these large parasites inflict when migrating through host tissues. Host immunity often targets the motility of tissue-migrating helminth larvae, which ideally should be mimicked by anti-helminth vaccines. However, the mechanisms of larval trapping are still poorly defined. We have recently reported an important role for Abs in the rapid trapping of tissue-migrating larvae of the murine parasite Heligmosomoides polygyrus bakeri. Trapping was mediated by macrophages (MΦ) and involved complement, activating FcRs, and Arginase-1 (Arg1) activity. However, the receptors and Ab isotypes responsible for MΦ adherence and Arg1 induction remained unclear. Using an in vitro coculture assay of H. polygyrus bakeri larvae and bone marrow-derived MΦ, we now identify CD11b as the major complement receptor mediating MΦ adherence to the larval surface. However, larval immobilization was largely independent of CD11b and instead required the activating IgG receptor FcγRI (CD64) both in vitro and during challenge H. polygyrus bakeri infection in vivo. FcγRI signaling also contributed to the upregulation of MΦ Arg1 expression in vitro and in vivo. Finally, IgG2a/c was the major IgG subtype from early immune serum bound by FcγRI on the MΦ surface, and purified IgG2c could trigger larval immobilization and Arg1 expression in MΦ in vitro. Our findings reveal a novel role for IgG2a/c-FcγRI-driven MΦ activation in the efficient trapping of tissue-migrating helminth larvae and thus provide important mechanistic insights vital for anti-helminth vaccine development.

Pronounced phenotype in activated regulatory T cells during a chronic helminth infection.

Although several markers have been associated with the characterization of regulatory T cells (Tregs) and their function, no studies have investigated the dynamics of their phenotype during infection. Since the necessity of Tregs to control immunopathology has been demonstrated, we used the chronic helminth infection model Schistosoma mansoni to address the impact on the Treg gene repertoire. Before gene expression profiling, we first studied the localization and Ag-specific suppressive nature of classically defined Tregs during infection. The presence of Foxp3+ cells was predominantly found in the periphery of granulomas and isolated CD4+CD25(hi)Foxp3+ Tregs from infected mice and blocked IFN-gamma and IL-10 cytokine secretion from infected CD4+CD25- effector T cells. Furthermore, the gene expression patterns of Tregs and effector T cells showed that 474 genes were significantly regulated during schistosomiasis. After k-means clustering, we identified genes exclusively regulated in all four populations, including Foxp3, CD103, GITR, OX40, and CTLA-4--classic Treg markers. During infection, however, several nonclassical genes were upregulated solely within the Treg population, such as Slpi, Gzmb, Mt1, Fabp5, Nfil3, Socs2, Gpr177, and Klrg1. Using RT-PCR, we confirmed aspects of the microarray data and also showed that the expression profile of Tregs from S. mansoni-infected mice is simultaneously unique and comparable with Tregs derived from other infections.

The alterations in genetic apparatus of somatic and generative cells of the host caused by helminths metabolites.

Alterations in the genetic apparatus of mice bone marrow cells and testicles caused by Hymenolepis nana, Ascaris suum and Toxocara canis metabolites have been investigated by means of micronuclear test application. The activity of spermatogenesis has been investigated at experimental hymenolepidosis, migrating ascariasis and toxocarosis with the use of 3H-timidine. Helminths metabolites have been established to exert a mutagenic effect on somatic cells of bone marrow, spermatogonies and also on the generative cells (spermatides) of helminths in invaded mice. The concurrent increase in micronucleus number in erythrocytes, spermatogonies and in spermatides (to a lesser degree) of invaded mice has been revealed. The decrease in spermatogenesis activity has been established in experimental hymenolepidosis, migrating ascariasis and toxocarosis in invaded mice.