Day, T. A. | bioRxiv Science

bioRxiv2020

Ivermectin inhibits extracellular vesicle secretion from parasitic nematodes

Lymphatic filariasis (LF) is a disease caused by parasitic filarial nematodes that is endemic in 49 countries and affects or threatens over 890 million people. Strategies to control LF rely heavily on mass administration of anthelmintic drugs including ivermectin (IVM), a macrocyclic lactone drug considered an Essential Medicine by the WHO. However, despite its widespread use the therapeutic mode of action of IVM against filarial nematodes is not clear. We have previously reported that filarial nematodes secrete extracellular vesicles (EVs) and that their cargo has immunomodulatory properties. Here we investigate the effects of IVM and other anti-filarial drugs on parasitic nematode EV secretion, motility, and protein secretion. We show that inhibition of EV secretion was a specific property of IVM, which had consistent and significant inhibitory effects across nematode life stages and species (with the exception of male parasites). IVM inhibited EV secretion, but not parasite motility, at therapeutically relevant concentrations. Protein secretion was inhibited by IVM in the microfilariae stage, but not in any other stage tested. Our data provides evidence that inhibiting the secretion of immunomodulatory EVs by parasitic nematodes could explain, at least in part, IVM mode of action and provides a phenotype for novel drug discovery.

molecular biology↗

bioRxiv2020

Identification of Bovine Genotypes Conferring Diminished Susceptibility to Salmonellosis and Colonization by Salmonella and E. coli O157:H7

ABSTRACTSalmonella and E. coli O157:H7 are two of the most important problems for the beef industry. Cattle can develop salmonellosis and persistently harbor Salmonella, or they can asymptomatically shed Salmonella and/or E. coli O157:H7 resulting in contamination of the hide and carcass surfaces during processing. Additionally, Salmonella infiltrates lymph nodes that get incorporated into ground beef. In this study, we investigated the possibility of identifying cattle with reduced susceptibility to one or both of these infections. Empirical observations from previous studies suggested that a diminished susceptibility was possible in amelanotic cattle, i.e., cattle bearing the mcr1/mcr1 genotype and lacking overt black pigmentation. By searching for single nucleotide polymorphisms (SNP) present in the 34 genes encoding the Salmonella interactome, we identified a SNP that was consistently present in amelanotic cattle with diminished susceptibility to Salmonella. Specifically, we used an ex vivo assay to screen 500 cattle blood samples for the diminished ability of Salmonella to penetrate peripheral leukocytes. Diminished Salmonella penetration was observed in 150 of these blood samples and 147 of these samples harbored two alleles bearing a SNP that introduces a miRNA cleavage site (bta-let-7b) in the 3’UTR of the bsynJ1 gene, which we designate as the SYNJ1/SNYJ1 genotype. Further ex vivo studies revealed a decreased expression of SYNJ1 in leukocytes bearing the SYNJ1/SNYJ1 genotype. In vivo experimental challenge studies revealed a diminished susceptibility to salmonellosis in cattle with the SYNJ1/SNYJ1::mcr1/mcr1 genotype. Additional in vivo challenge studies revealed that SYNJ1/SNYJ1::mcr1/mcr1 cattle have a decreased susceptibility to lymph node infiltration by two Salmonella serotypes (S. Anatum and S. Montevideo) implicated in this lymph node problem, and a decreased susceptibility to E. coli O157:H7 colonization of the recto-anal junction. A field study revealed that the SYNJ1/SNYJ1::mcr1/mcr1 genotype was five times more prevalent, when compared to the SYNJ1/synj1::mcr1/mcr1 and synj1/ synj1::mcr1/mcr1 genotypes, in Salmonella-free lymph nodes. Small-scale genetic surveys revealed that the SYNJ1/SNYJ1 genotype was present in the following mcr1/mcr1 breeds: Akaushi, Barzona, Braunvieh, Hereford, Piedmontese, Red and White Holsteins, Red Angus, Red Poll, Shorthorn, Simmental (Red), and Tarentaise. Studies using the aforementioned ex vivo penetration assay, which putatively predicts the diminished susceptibility phenotype, revealed that the penetrance of the diminished susceptibility is >99% in SYNJ1/SNYJ1::mcr1/mcr1 cattle but only ∼1% in SYNJ1/SNYJ1 cattle with at least one MCR1 allele. Further studies with the ex vivo assay revealed that three additional SNPs are part of a genotype conferring diminished susceptibility to a broad array of Salmonella serotypes commonly associated with cattle. In summary, the studies presented herein reveal a bovine genotype associated with decreased susceptibility to Salmonella and E. coli O157:H7. PSR Genetics LLC holds a U.S. patent on testing for the SYNJ1/SNYJ1 genotype (patent number 9,049,848) while the three complementary SNPs are under further investigation.Competing Interest StatementThis study was funded by PSR Genetics LLC which included a rental agreement for laboratory space at Iowa State UniversityView Full Text

genetics↗