No abstract

Group B Streptococcus (GBS) causes frequent urinary tract infection (UTI) in susceptible populations, including individuals with type 2 diabetes and pregnant women; however, specific host factors responsible for increased GBS susceptibility in these populations are not well characterized. Here, we investigate cathelicidin, a cationic antimicrobial peptide, known to be critical for defense during UTI with uropathogenic Escherichia coli (UPEC). We observed a loss of antimicrobial activity of human and mouse cathelicidins against GBS and UPEC in synthetic urine and no evidence for increased cathelicidin resistance in GBS urinary isolates. Furthermore, we found that GBS degrades cathelicidin in a protease-dependent manner. Surprisingly, in a UTI model, cathelicidin-deficient (Camp−/−) mice showed decreased GBS burdens and mast cell recruitment in the bladder compared to levels in wild-type (WT) mice. Pharmacologic inhibition of mast cells reduced GBS burdens and histamine release in WT but not Camp−/− mice. Streptozotocin-induced diabetic mice had increased bladder cathelicidin production and mast cell recruitment at 24 h postinfection with GBS compared to levels in nondiabetic controls. We propose that cathelicidin is an important immune regulator but ineffective antimicrobial peptide against GBS in urine. Combined, our findings may in part explain the increased frequency of GBS UTI in diabetic and pregnant individuals. IMPORTANCE Certain populations such as diabetic individuals are at increased risk for developing urinary tract infections (UTI), although the underlying reasons for this susceptibility are not fully known. Additionally, diabetics are more likely to become infected with certain types of bacteria, such as group B Streptococcus (GBS). In this study, we find that an antimicrobial peptide called cathelicidin, which is thought to protect the bladder from infection, is ineffective in controlling GBS and alters the type of immune cells that migrate to the bladder during infection. Using a mouse model of diabetes, we observe that diabetic mice are more susceptible to GBS infection even though they also have more infiltrating immune cells and increased production of cathelicidin. Taken together, our findings identify this antimicrobial peptide as a potential contributor to increased susceptibility of diabetic individuals to GBS UTI.

During pregnancy, GBS ascension into the uterus can cause fetal infection or preterm birth. In addition, GBS exposure during labor creates a risk of serious disease in the vulnerable newborn and mother postpartum.

White spot syndrome virus (WSSV) is one of the major viral pathogens affecting shrimp aquaculture. Four proteins, WSSV199, WSSV 222, WSSV 249 and WSSV 403, from WSSV are predicted to encode a RING-H2 domain, which in presence of ubiquitin conjugating enzyme (E2) in shrimp can function as viral E3 ligase and modulate the host ubiquitin proteasome pathway. Modulation of host ubiquitin proteasome pathway by viral proteins is implicated in viral pathogenesis. In the present study, a time course expression profile analysis of WSSV Open Reading Frame (ORF) 199 and Penaeus monodon ubiquitin conjugating enzyme (PmUbc) was carried out at 0, 3, 6, 12, 24, 48 and 72 h post WSSV challenge by semi-quantitative RT-PCR as well as Real Time PCR. EF1α was used as reference control to normalize the expression levels. A significant increase in PmUbc expression at 24 h post infection (h.p.i) was observed followed by a decline till 72 h.p.i. Expression of WSSV199 was observed at 24 h.p.i in WSSV infected P. monodon. Since the up-regulation of PmUbc was observed at 24 h.p.i where WSSV199 expression was detected, it can be speculated that these proteins might interact with host ubiquitination pathway for viral pathogenesis. However, further studies need to be carried out to unfold the molecular mechanism of interaction between host and virus to devise efficient control strategies for this chaos in the shrimp culture industry.

Toll-like receptors are sentinels of innate immune system, which recognise pathogen-associated molecular patterns, and subsequently activate production of antimicrobial peptides to contain the infection. In the present study, we cloned and characterised a Toll gene from Scylla serrata (SsToll) encoding 1005 amino acids with typical Toll-like receptor domain topology. Phylogenetic analysis revealed that it belongs to insect-type invertebrate Toll family showing 100 % identity with Scylla paramamosain (SpToll). The expression pattern of mRNA in different tissues indicated that SsToll is constitutively expressed in all the tissues examined, with varying expression levels. The expression was also detected in all the life-stages (egg, zoea stages 1-5, megalopa and crab instar) with the highest level observed in zoea 2. In-vitro studies using crab haemocyte culture demonstrated that SsToll transcripts are distinctly modulated in response to ligands such as peptidoglycan and lipopolysaccharide at all time-points. A significant change in SsToll expression was also noticed in haemocytes exposed to poly I:C (3-9 h). On the contrary, the transcription level of SsToll in response to white spot syndrome virus (WSSV) challenge was noticeably different. The change in expression in vitro was not significant at early time-points until 3 h; the transcripts showed a significant up-regulation commencing from 6 h, but not beyond 12 h. However, in vivo expression was unaffected at early time-points of WSSV challenge (until 12 h) and a gradual up-regulation was detected at 24 h. In-vivo challenge with Vibrio parahaemolyticus resulted in delayed up-regulation of the gene. The results obtained in the present study suggest that SsToll might be involved in the innate immunity of mud crab.

Group B Streptococcus (GBS) colonizes the vaginal mucosa of a significant percentage of healthy women and is a leading cause of neonatal bacterial infections. Currently, pregnant women are screened in the last month of pregnancy and GBS-positive women are given antibiotics during parturition to prevent bacterial transmission to the neonate. Recently, human milk oligosaccharides (HMOs) isolated from breastmilk were found to inhibit GBS growth and biofilm formation in vitro, and women that make certain HMOs are less likely to be vaginally colonized with GBS. Using in vitro human vaginal epithelial cells and a murine vaginal colonization model, we tested the impact of HMO treatment on GBS burdens and the composition of the endogenous microbiota by 16S rRNA amplicon sequencing. HMO treatment reduced GBS vaginal burdens in vivo with minimal alterations to the vaginal microbiota. HMOs displayed potent inhibitory activity against GBS in vitro, but HMO pretreatment did not alter adherence of GBS or the probiotic Lactobacillus rhamnosus to human vaginal epithelial cells. Additionally, disruption of a putative GBS glycosyltransferase (Δsan_0913) rendered the bacterium largely resistant to HMO inhibition in vitro and in vivo but did not compromise its adherence, colonization, or biofilm formation in the absence of HMOs. We conclude that HMOs are a promising therapeutic bioactive to limit GBS vaginal colonization with minimal impacts on the vaginal microenvironment.

Edwardsiella tarda is a versatile pathogen that could survive in different environmental conditions and infect economically important fish species. The whole cell antigenic proteins were extracted from E. tarda and assessed via Western blot using anti E. trada rohu and anti E. trada rabbit serum. Two strong reacted proteins with antibodies were recovered viz 61 kDa and 47 kDa from SDS PAGE gels to evaluate their vaccine potential in rohu fish. Fish were vaccinated 10 µg of antigenic proteins intraperitoneally as immunogens with Freund's incomplete adjuvant (FIA). The boosters were given on the 10 th day of immunization with PBS. The blood was drawn from vena caudalis at every 7 th day for hematological and immunological studies. Fish were challenged on 35 th day with 1× 10 6 cfu E. tarda field isolate ET-1.

No abstract