QseC Signaling in the Outbreak O104:H4 Escherichia coli Strain Combines Multiple Factors during Infection.

Enteroaggregative Escherichia coli (EAEC) from the O104:H4 specific serotype caused a large outbreak of bloody diarrhea with some complicated cases of hemolytic-uremic syndrome (HUS) in Europe in 2011. The outbreak strain consisted in an EAEC capable to produce the Shiga toxin (Stx) subtype 2a, a characteristic from enterohemorrhagic E. coli QseBC two-component system detects AI-3/Epi/NE and mediates the chemical signaling between pathogen and mammalian host. This system coordinates a cascade of virulence genes expression in important human enteropathogens. The blocking of QseC of EAEC C227-11 (Stx+) strain by N-phenyl-4-{[(phenylamino) thioxomethyl]amino}-benzenesulfonamide (also known as LED209) in vivo demonstrated a lower efficiency of colonization. The periplasmic protein VisP, which is related to survival mechanisms in a colitis model of infection, bacterial membrane maintenance, and stress resistance, here presented high levels of expression during the initial infection within the host. Under acid stress conditions, visP expression levels were differentiated in an Stx-dependent way. Together, these results emphasize the important role of VisP and the histidine kinase sensor QseC in the C227-11 (Stx+) outbreak strain for the establishment of the infectious niche process in the C57BL/6 mouse model and of LED209 as a promising antivirulence drug strategy against these enteric pathogens.IMPORTANCE EAEC is a remarkable etiologic agent of acute and persistent diarrhea worldwide. The isolates harbor specific subsets of virulence genes and their pathogenesis needs to be better understood. Chemical signaling via histidine kinase sensor QseC has been shown as a potential target to elucidate the orchestration of the regulatory cascade of virulence factors.

Novel Role of VisP and the Wzz System during O-Antigen Assembly in Salmonella enterica Serovar Typhimurium Pathogenesis.

Salmonella enterica serovars are associated with diarrhea and gastroenteritis and are a helpful model for understanding host-pathogen mechanisms. Salmonella enterica serovar Typhimurium regulates the distribution of O antigen (OAg) and presents a trimodal distribution based on Wzy polymerase and the WzzST (long-chain-length OAg [L-OAg]) and WzzfepE (very-long-chain-length OAg [VL-OAg]) copolymerases; however, several mechanisms regulating this process remain unclear. Here, we report that LPS modifications modulate the infectious process and that OAg chain length determination plays an essential role during infection. An increase in VL-OAg is dependent on Wzy polymerase, which is promoted by a growth condition resembling the environment of Salmonella-containing vacuoles (SCVs). The virulence- and stress-related periplasmic protein (VisP) participates in OAg synthesis, as a ΔvisP mutant presents a semirough OAg phenotype. The ΔvisP mutant has greatly decreased motility and J774 macrophage survival in a colitis model of infection. Interestingly, the phenotype is restored after mutation of the wzzST or wzzfepE gene in a ΔvisP background. Loss of both the visP and wzzST genes promotes an imbalance in flagellin secretion. L-OAg may function as a shield against host immune systems in the beginning of an infectious process, and VL-OAg protects bacteria during SCV maturation and facilitates intramacrophage replication. Taken together, these data highlight the roles of OAg length in generating phenotypes during S Typhimurium pathogenesis and show the periplasmic protein VisP as a novel protein in the OAg biosynthesis pathway.

"An Extra Variable to Consider"-Vaccine-Induced Seropositivity and Adolescent HIV Vaccine Clinical Trials.

Our study explores the understanding of vaccine-induced seropositivity (VISP) and its potential impact on US adolescents' and caregivers' willingness to participate in adolescent HIV vaccine clinical trials. Findings from in-depth interviews suggest that addressing concerns about VISP will be essential for future pediatric HIV vaccine trials in the United States.

Salmonella Typhimurium O-antigen and VisP play an important role in swarming and osmotic stress response during intracellular conditions.

Salmonella Typhimurium is a pathogen of clinical relevance and a model of study in host-pathogen interactions. The virulence and stress-related periplasmic protein VisP is important during S. Typhimurium pathogenesis. It supports bacteria invading host cells, surviving inside macrophages, swimming, and succeeding in murine colitis model, O-antigen assembly, and responding to cationic antimicrobial peptides. This study aimed to investigate the role of the O-antigen molecular ruler WzzST and the periplasmic protein VisP in swarming motility and osmotic stress response. Lambda red mutagenesis was performed to generate single and double mutants, followed by swarming motility, qRT-PCR, Western blot, and growth curves. Here we demonstrate that the deletion of visP affects swarming under osmotic stress and changes the expression levels of genes responsible for chemotaxis, flagella assembly, and general stress response. The deletion of the gene encoding for the O-antigen co-polymerase wzzST increases swarming motility but not under osmotic stress. A second mutation in O-antigen co-polymerase wzzST in a ΔvisP background affected gene expression levels. The ΔvisP growth was affected by sodium and magnesium levels on N-minimum media. These data indicate that WzzST has a role in swarming the motility of S. Typhimurium, as the VisP is involved in chemotaxis and osmotic stress, specifically in response to MgCl2 and NaCl.

Mandatory immunization and vaccine injury support programs: A survey of 28 GNN countries.

BACKGROUND: Despite the proposed ethical link between mandatory immunization and Vaccine Injury Support Programs (VISPs), relatively few jurisdictions, even those with mandatory immunization, have implemented such programs. Although it may be assumed that individuals injured by a vaccine in a non-VISP country receive less support than in countries possessing such programs, the extent of the discrepancy is not clear; nor is the nature of any discrepancy. METHODS: In our 2018 survey of 28 Global NITAG (National Immunization Technical Advisory Group) Network (GNN) countries, we asked respondents about mandatory immunization and the availability of VISPs. Responses were supplemented with desktop research and review of scholarly literature for further information regarding VISP availability and details. RESULTS: Although only two of 14 (14%) surveyed jurisdictions with mandatory immunization had formal VISPs, responses from additional countries suggested the presence of less formal avenues of compensation for serious Adverse Events Following Immunization (AEFIs); similarly, we found five of 15 (33%) of countries without mandatory immunization had implemented formal VISPs, but another three such countries suggested similar informal methods of compensation. CONCLUSIONS: From our data, it is evident that at least some countries with mandatory immunization may discharge their (perceived or actual) ethical obligation to provide financial assistance to vaccine-injured individuals through more informal avenues rather than structured VISPs, although the extent and impact of this practice is by its nature difficult to assess. Further, the nature of VISPs may vary significantly from jurisdiction to jurisdiction, and simple VISP/non-VISP classification of jurisdiction may fail to capture nuance in support for AEFI victims in many jurisdictions. Future assessments of VISPs should consider the possibility of these more informal avenues of support for vaccine injuries.

Epigenome-Wide Analyses Identify Two Novel Associations With Recurrent Stroke in the Vitamin Intervention for Stroke Prevention Clinical Trial.

DNA methylation, a well-characterized epigenetic modification that is influenced by both environment and genetic variation, has previously been implicated in a number of complex diseases, including cardiovascular disease and stroke. The goal of this study was to evaluate epigenome-wide associations with recurrent stroke and the folate one-carbon metabolism-related trait, plasma homocysteine (hcy). Differential methylation analyses were performed on 473,864 autosomal CpG loci, using Illumina HumanMethylation 450K array data in 180 ischemic stroke cases from the Vitamin Intervention for Stroke Prevention (VISP) clinical trial. Linear regression was used to assess associations between number of strokes prior to VISP enrollment and measures of hcy with degree of methylation (ß-values), while logistic regression was used to evaluate recurrent stroke status and incident recurrent stroke associations. All regression analyses were stratified by race. Two differentially methylated CpG sites exceeded epigenome-wide significance (p ≤ 1.055 × 10-7) for prior number of strokes (PNS) in European Americans. The top locus, cg22812874, was located in the ankyrin repeat and SOCS box containing 10 gene (ASB10; p = 3.4 × 10-9; ß = -0.0308; 95% CI = -0.040, -0.002). Methylation locus cg00340919, located in an intron of the tetratricopeptide repeat domain 37 gene, was also statistically significant (TTC37; p = 8.74 × 10-8; ß = -0.0517; 95% CI = -0.069, -0.034). An additional 138 CpG sites met our threshold for suggestive significance (p ≤ 5 × 10-5). We evaluated DNA methylation associated with recurrent stroke and hcy phenotypes across the epigenome. Hypermethylation at two CpG sites located in ASB10 and TTC37 was associated with fewer strokes prior to VISP enrollment. Our findings present a foundation for additional epigenome-wide studies, as well as mechanistic studies into epigenetic marks that influence recurrent stroke risk.

HIV vaccine-induced sero-reactivity: a challenge for trial participants, researchers, and physicians.

Antibody-inducing vaccines are a major focus in the preventive HIV vaccine field. Because the most common tests for HIV infection rely on detecting antibodies to HIV, they may also detect antibodies induced by a candidate HIV vaccine. The detection of vaccine-induced antibodies to HIV by serological tests is most commonly referred to as vaccine-induced sero-reactivity (VISR). VISR can be misinterpreted as a sign of HIV infection in a healthy study participant. In a participant who has developed vaccine-induced antibodies, accurate diagnosis of HIV infection (or lack thereof) may require specialized tests and algorithms (differential testing) that are usually not available in community settings. Organizations sponsoring clinical testing of preventive HIV vaccine candidates have an ethical obligation not only to inform healthy volunteers about the potential problems associated with participating in a clinical trial but also to help manage any resulting issues. This article explores the scope of VISR-related issues that become increasingly prevalent as the search for an effective HIV vaccine continues and will be paramount once a preventive vaccine is deployed. We also describe ways in which organizations conducting HIV vaccine trials have addressed these issues and outline areas where more work is needed.

Genetic Associations with Plasma B12, B6, and Folate Levels in an Ischemic Stroke Population from the Vitamin Intervention for Stroke Prevention (VISP) Trial.

BACKGROUND: B vitamins play an important role in homocysteine metabolism, with vitamin deficiencies resulting in increased levels of homocysteine and increased risk for stroke. We performed a genome-wide association study (GWAS) in 2,100 stroke patients from the Vitamin Intervention for Stroke Prevention (VISP) trial, a clinical trial designed to determine whether the daily intake of high-dose folic acid, vitamins B6, and B12 reduce recurrent cerebral infarction. METHODS: Extensive quality control (QC) measures resulted in a total of 737,081 SNPs for analysis. Genome-wide association analyses for baseline quantitative measures of folate, Vitamins B12, and B6 were completed using linear regression approaches, implemented in PLINK. RESULTS: Six associations met or exceeded genome-wide significance (P ≤ 5 × 10(-08)). For baseline Vitamin B12, the strongest association was observed with a non-synonymous SNP (nsSNP) located in the CUBN gene (P = 1.76 × 10(-13)). Two additional CUBN intronic SNPs demonstrated strong associations with B12 (P = 2.92 × 10(-10) and 4.11 × 10(-10)), while a second nsSNP, located in the TCN1 gene, also reached genome-wide significance (P = 5.14 × 10(-11)). For baseline measures of Vitamin B6, we identified genome-wide significant associations for SNPs at the ALPL locus (rs1697421; P = 7.06 × 10(-10) and rs1780316; P = 2.25 × 10(-08)). In addition to the six genome-wide significant associations, nine SNPs (two for Vitamin B6, six for Vitamin B12, and one for folate measures) provided suggestive evidence for association (P ≤ 10(-07)). CONCLUSION: Our GWAS study has identified six genome-wide significant associations, nine suggestive associations, and successfully replicated 5 of 16 SNPs previously reported to be associated with measures of B vitamins. The six genome-wide significant associations are located in gene regions that have shown previous associations with measures of B vitamins; however, four of the nine suggestive associations represent novel finding and warrant further investigation in additional populations.