Low-density lipoprotein receptor-related protein 1 is a CROPs-associated receptor for Clostridioides infection toxin B.

As the leading cause of worldwide hospital-acquired infection, Clostridioides difficile (C. difficile) infection has caused heavy economic and hospitalized burden, while its pathogenesis is not fully understood. Toxin B (TcdB) is one of the major virulent factors of C. difficile. Recently, CSPG4 and FZD2 were reported to be the receptors that mediate TcdB cellular entry. However, genetic ablation of genes encoding these receptors failed to completely block TcdB entry, implicating the existence of alternative receptor(s) for this toxin. Here, by employing the CRISPR-Cas9 screen in CSPG4-deficient HeLa cells, we identified LDL receptor-related protein-1 (LRP1) as a novel receptor for TcdB. Knockout of LRP1 in both CSPG4-deficient HeLa cells and colonic epithelium Caco2 cells conferred cells with increased TcdB resistance, while LRP1 overexpression sensitized cells to TcdB at a low concentration. Co-immunoprecipitation assay showed that LRP1 interacts with full-length TcdB. Moreover, CROPs domain, which is dispensable for TcdB's interaction with CSPG4 and FZD2, is sufficient for binding to LRP1. As such, our study provided evidence for a novel mechanism of TcdB entry and suggested potential therapeutic targets for treating C. difficile infection.

Molecular and morphological characterization of third instar Palaearctic horse stomach bot fly larvae (Oestridae: Gasterophilinae, Gasterophilus).

Species of Gasterophilus are obligate parasites of equids and may induce severe, even lethal myiasis. However, identification of the third instar Gasterophilus larva at the species level is still problematic predominantly due to a shortage of diagnostic morphological features and incomplete molecular libraries. Testing the suitability of three different molecular markers showed that the traditional 650 bp barcode region near the 5' terminus of the cytochrome c oxidase subunit I (COI) served as a better tool for species-level identification than a 663 bp region near the 3' terminus of COI and a 554 bp region near the 5' terminus of the large subunit ribosomal RNA. We found that barcoding discriminates G. intestinalis, G. nasalis, G. nigricornis and G. pecorum but not G. haemorrhoidalis and G. inermis. A comparative morphological study using scanning electron microscopy was conducted to promote the identification of the third instar larvae. Photographs of fresh mature third instar larvae are provided for all species, and the remarkable green body colour of third instar G. nigricornis is fully documented for the first time. Two morphological keys are provided, one is suitable for quick identification, and the other based on ultrastructural details is provided for further comparative morphological investigation. A new term 'oral plate' instead of 'mandible' was proposed for a pair of sclerites of uncertain homology emerging from the secondary mouth opening. Our data shows that DNA barcodes cannot replace morphology for identification of third instars of Gasterophilus species, and a scaffold is provided for an integrated taxonomic reference system, which will contribute to monitoring gasterophilosis for equid welfare and protection, and also facilitate further studies in functional anatomy, phylogenetic analyses and host-parasite co-evolutionary investigations of Gasterophilus.

Review of the genus Agria (Diptera, Sarcophagidae) from China.

Agria mihalyii (Rohdendorf and Verves, 1978) is recorded from China for the first time, and both sexes are thoroughly documented using a combination of illustrations, photographs and scanning electron microscopy images. The generic affiliation is corroborated from an expanded definition of genus Agria Robineau-Desvoidy, 1830, and a key to males of the two known species from China is provided. The distribution of coeloconic sensilla on the male pre- and postgonite are shown to possess significant diagnostic and phylogenetic information in this genus.