Ixodes scapularis nymph saliva protein blocks host inflammation and complement-mediated killing of Lyme disease agent, Borrelia burgdorferi

Tick serine protease inhibitors (serpins) play crucial roles in tick feeding and pathogen transmission. We demonstrate that Ixodes scapularis (Ixs) nymph tick saliva serpin (S) 41 (IxsS41), secreted by Borrelia burgdorferi (Bb)-infected ticks at high abundance, is involved in regulating tick evasion of host innate immunity and promoting host colonization by Bb. Recombinant (r) proteins were expressed in Pichia pastoris, and substrate hydrolysis assays were used to determine. Ex vivo (complement and hemostasis function related) and in vivo (paw edema and effect on Bb colonization of C3H/HeN mice organs) assays were conducted to validate function. We demonstrate that rIxsS41 inhibits chymase and cathepsin G, pro-inflammatory proteases that are released by mast cells and neutrophils, the first immune cells at the tick feeding site. Importantly, stoichiometry of inhibition analysis revealed that 2.2 and 2.8 molecules of rIxsS41 are needed to 100% inhibit 1 molecule of chymase and cathepsin G, respectively, suggesting that findings here are likely events at the tick feeding site. Furthermore, chymase-mediated paw edema, induced by the mast cell degranulator, compound 48/80 (C48/80), was blocked by rIxsS41. Likewise, rIxsS41 reduced membrane attack complex (MAC) deposition via the alternative and lectin complement activation pathways and dose-dependently protected Bb from complement killing. Additionally, co-inoculating C3H/HeN mice with Bb together with rIxsS41 or with a mixture (rIxsS41 and C48/80). Findings in this study suggest that IxsS41 markedly contributes to tick feeding and host colonization by Bb. Therefore, we conclude that IxsS41 is a potential candidate for an anti-tick vaccine to prevent transmission of the Lyme disease agent.

miR-509-5p anti-infection response for mycoplasma pneumonia in sheep by targeting NF-κB pathway

MicroRNAs play a key role in Mannan-binding lectin-mediated resistance to Mycoplasma ovipneumoniae pneumonia, by regulating the translation of mRNAs of target genes, thereby regulating the immune response. Additionally, TRAF6 is a key molecule in Toll-like receptor signal transduction, which mediates inflammation and apoptosis signaling pathways and is widely involved in inflammation and immune response. While the molecular regulation mechanism has not been reported. In this study, we screened differentially expressed miRNAs and genes of Anti-infection for M. pneumonia on Sheep, through relevant bioinformatics analysis. Further, the effect of differential expression of NF-κB signaling pathway related genes on the molecular mechanism of M. pneumonia was detected. We used miRNA-mRNA integrated analysed, the target gene TRAF6 of miR-509-5p was selected. TRAF6 dual luciferase reporter vector was co-transfected into HEK 293T cells and primary sheep respiratory mucosal epithelial cells to detect changes in luciferase activity. qRT-PCR was used to analyze the effect of miR-509-5p on the expression and regulation of TRAF6 and other genes related to the NF-κB signaling pathway. The result confirmed that TRAF6 was a target gene of miR-509-5p. Compared with miR-509-5p-NC group, the luciferase activity of miR-509-5p group was significantly down-regulated (P < 0.01). Further, in sheep respiratory mucosal epithelial cells, miR-509-5p mimic could significantly down-regulate the fold change value of TRAF6 (P < 0.01). On the contrary, miR-509-5p-inhibitor up-regulated the fold change value of TRAF6 (P < 0.05). Interestingly, the expression levels of other genes were different. Among them, miR-509-5p mimic significantly up-regulated TLR4 and IRAK4 (P < 0.05), significantly down-regulated TAK1 (P < 0.05) and NF-κB (P < 0.01). miR-509-5p-inhibitor significantly up-regulated NF-κB (P < 0.05) and TAK1 (P < 0.01). miR-509-5p targets TRAF6 to affect the expression of downstream genes, which negatively regulates the NF-κB pathway, thereby affecting the inflammatory response.

The role of Mannose Binding Lectin in the immune response against Borrelia burgdorferi sensu lato

The causative agents of Lyme borreliosis, spirochetes belonging to the Borrelia burgdorferi sensu lato group, have developed several ways to protect themselves against killing by the host complement system. In addition, it has been shown that serum sensitive isolates are (partially) protected by the Ixodes Tick Salivary Lectin Pathway Inhibitor (TSLPI) protein; a salivary gland protein that inhibits the function of Mannose Binding Lectin (MBL). MBL is a C-type lectin that recognizes oligosaccharides on pathogens and activates the complement system via the lectin pathway. MBL deficiency has been linked to a more severe course of several infectious diseases and humans with detectable antibodies against B. burgdorferi are significantly more often MBL deficient compared to humans without antibodies against B. burgdorferi. Here we set out to investigate the role of MBL in the immune response against B. burgdorferi in more detail. We demonstrate that B. burgdorferi N40 needle-infected C57BL/6 MBL deficient mice harbored significantly higher B. burgdorferi numbers in skin tissue during the early course of infection. In line with these findings they also developed higher anti-B. burgdorferi IgG serum antibodies compared to WT controls. In contrast, B. burgdorferi loads in distant tissue such as heart, joints or bladder at later time points were similar for both mouse strains. These in vivo findings were corroborated using a B. burgdorferi N40-infected I. scapularis infestation model. We showed that MBL is capable of binding B. burgdorferi through its carbohydrate recognition domains, but in vitro complement killing assays, peritoneal macrophage and whole blood stimulations, phagocytosis assays and an in vivo migration experiment did not reveal the mechanism by which MBL facilitates early clearance of B. burgdorferi. To conclude, we show a protective role of MBL in the early stages of B. burgdorferi infection, yet the underlying mechanism warrants further investigation.

Mannose-binding lectin gene polymorphism in relation to periodontal infection

BACKGROUND AND OBJECTIVE

Mannose-binding lectin (MBL) plays an important role in innate immunity. MBL deficiency is usually caused by mutations in exon 1 of the MBL structural gene (MBL2). Our aim was to investigate MBL2 polymorphisms and their relation to salivary levels of periodontal inflammatory/tissue destruction markers and two major periodontitis-associated bacteria.

MATERIAL AND METHODS

Salivary samples from 222 subjects were available for genotyping by pyrosequencing. The subjects between 40 and 60 years of age and having a minimum of 20 teeth were divided into three periodontal groups: 80 had generalized periodontitis, 65 had localized periodontitis and 77 were periodontitis-free. A comparison between their MBL2 genotypes and salivary detection rates and levels of Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis as well as interleukin -1β, matrix metalloproteinase -8, and tissue inhibitor of matrix metalloproteinase (TIMP)-1 was performed.

RESULTS

The frequencies of the MBL2 wild-type (A/A), heterozygote variants (A/O) and homozygote variants (O/O) were 69.4%, 26.6% and 4%, respectively. In A. actinomycetemcomitans-positive subjects having homozygote or heterozygote MBL2 variants, the salivary concentrations of IL-1β (p = 0.010) were elevated and those of TIMP-1 (p = 0.001) were decreased. In addition their matrix metalloproteinase -8/TIMP-1 ratio was higher (p < 0.001) and they had more pocket teeth (p = 0.012) than subjects negative for A. actinomycetemcomitans.

CONCLUSION

Our findings indicate that the carriage of A. actinomycetemcomitans may facilitate extended periodontal inflammation and destruction in subjects with a variant form of human MBL2.