VAV1 and BAFF, via NFκB pathway, are genetic risk factors for myasthenia gravis

Objective To identify novel genetic loci that predispose to early‐onset myasthenia gravis (EOMG) applying a two‐stage association study, exploration, and replication strategy. Methods Thirty‐four loci and one confirmation loci, human leukocyte antigen (HLA)‐DRA, were selected as candidate genes by team members of groups involved in different research aspects of MG. In the exploration step, these candidate genes were genotyped in 384 EOMG and 384 matched controls and significant difference in allele frequency were found in eight genes. In the replication step, eight candidate genes and one confirmation loci were genotyped in 1177 EOMG patients and 814 controls, from nine European centres. Results Allele frequency differences were found in four novel loci: CD86, AKAP12, VAV1, B‐cell activating factor (BAFF), and tumor necrosis factor‐alpha (TNF‐α), and these differences were consistent in all nine cohorts. Haplotype trend test supported the differences in allele frequencies between cases and controls. In addition, allele frequency difference in female versus male patients at HLA‐DRA and TNF‐α loci were observed. Interpretation The genetic associations to EOMG outside the HLA complex are novel and of interest as VAV1 is a key signal transducer essential for T‐ and B‐cell activation, and BAFF is a cytokine that plays important roles in the proliferation and differentiation of B‐cells. Moreover, we noted striking epistasis between the predisposing VAV1 and BAFF haplotypes; they conferred a greater risk in combination than alone. These, and CD86, share the same signaling pathway, namely nuclear factor‐kappaB (NFκB), thus implicating dysregulation of proinflammatory signaling in predisposition to EOMG

Coreceptor affinity for MHC defines peptide specificity requirements for TCR interaction with coagonist peptide–MHC

Recent work has demonstrated that nonstimulatory endogenous peptides can enhance T cell recognition of antigen, but MHCI- and MHCII-restricted systems have generated very different results. MHCII-restricted TCRs need to interact with the nonstimulatory peptide–MHC (pMHC), showing peptide specificity for activation enhancers or coagonists. In contrast, the MHCI-restricted cells studied to date show no such peptide specificity for coagonists, suggesting that CD8 binding to noncognate MHCI is more important. Here we show how this dichotomy can be resolved by varying CD8 and TCR binding to agonist and coagonists coupled with computer simulations, and we identify two distinct mechanisms by which CD8 influences the peptide specificity of coagonism. Mechanism 1 identifies the requirement of CD8 binding to noncognate ligand and suggests a direct relationship between the magnitude of coagonism and CD8 affinity for coagonist pMHCI. Mechanism 2 describes how the affinity of CD8 for agonist pMHCI changes the requirement for specific coagonist peptides. MHCs that bind CD8 strongly were tolerant of all or most peptides as coagonists, but weaker CD8-binding MHCs required stronger TCR binding to coagonist, limiting the potential coagonist peptides. These findings in MHCI systems also explain peptide-specific coagonism in MHCII-restricted cells, as CD4–MHCII interaction is generally weaker than CD8–MHCI.National Institutes of Health (U.S.). Pioneer Awar

An Eye to a Kill: Using Predatory Bacteria to Control Gram-Negative Pathogens Associated with Ocular Infections

Ocular infections are a leading cause of vision loss. It has been previously suggested that predatory prokaryotes might be used as live antibiotics to control infections. In this study, Pseudomonas aeruginosa and Serratia marcescens ocular isolates were exposed to the predatory bacteria Micavibrio aeruginosavorus and Bdellovibrio bacteriovorus. All tested S. marcescens isolates were susceptible to predation by B. bacteriovorus strains 109J and HD100. Seven of the 10 P. aeruginosa isolates were susceptible to predation by B. bacteriovorus 109J with 80% being attacked by M. aeruginosavorus. All of the 19 tested isolates were found to be sensitive to at least one predator. To further investigate the effect of the predators on eukaryotic cells, human corneal-limbal epithelial (HCLE) cells were exposed to high concentrations of the predators. Cytotoxicity assays demonstrated that predatory bacteria do not damage ocular surface cells in vitro whereas the P. aeruginosa used as a positive control was highly toxic. Furthermore, no increase in the production of the proinflammatory cytokines IL-8 and TNF-alpha was measured in HCLE cells after exposure to the predators. Finally, injection of high concentration of predatory bacteria into the hemocoel of Galleria mellonella, an established model system used to study microbial pathogenesis, did not result in any measurable negative effect to the host. Our results suggest that predatory bacteria could be considered in the near future as a safe topical bio-control agent to treat ocular infections. © 2013 Shanks et al

Genome-Wide Association Study of Late-Onset Myasthenia Gravis: Confirmation of TNFRSF11A and Identification of ZBTB10 and Three Distinct HLA Associations

To investigate the genetics of late-onset myasthenia gravis (LOMG), we conducted a genome-wide association study imputation of >6 million single nucleotide polymorphisms (SNPs) in 532 LOMG cases (anti-acetylcholine receptor [AChR] antibody positive; onset age ≥50 years) and 2,128 controls matched for sex and population substructure. The data confirm reported TNFRSF11A associations (rs4574025, P = 3.9 × 10−7, odds ratio [OR] 1.42) and identify a novel candidate gene, ZBTB10, achieving genome-wide significance (rs6998967, P = 8.9 × 10−10, OR 0.53). Several other SNPs showed suggestive significance including rs2476601 (P = 6.5 × 10−6, OR 1.62) encoding the PTPN22 R620W variant noted in early-onset myasthenia gravis (EOMG) and other autoimmune diseases. In contrast, EOMG-associated SNPs in TNIP1 showed no association in LOMG, nor did other loci suggested for EOMG. Many SNPs within the major histocompatibility complex (MHC) region showed strong associations in LOMG, but with smaller effect sizes than in EOMG (highest OR ∼2 versus ∼6 in EOMG). Moreover, the strongest associations were in opposite directions from EOMG, including an OR of 0.54 for DQA1*05:01 in LOMG (P = 5.9 × 10−12) versus 2.82 in EOMG (P = 3.86 × 10−45). Association and conditioning studies for the MHC region showed three distinct and largely independent association peaks for LOMG corresponding to (a) MHC class II (highest attenuation when conditioning on DQA1), (b) HLA-A and (c) MHC class III SNPs. Conditioning studies of human leukocyte antigen (HLA) amino acid residues also suggest potential functional correlates. Together, these findings emphasize the value of subgrouping myasthenia gravis patients for clinical and basic investigations and imply distinct predisposing mechanisms in LOMG

Effect of phospholipid deposits on adhesion of bacteria to contact lenses

PURPOSE.: Protein and lipid deposits on contact lenses may contribute to clinical complications. This study examined the effect of phospholipids on the adhesion of bacteria to contact lenses. METHODS.: Worn balafilcon A (n = 11) and senofilcon A (n = 11) were collected after daily wear and phospholipids were extracted in chloroform:methanol. The amount of phospholipid was measured by electrospray ionization mass spectrometry. Unworn lenses soaked in phospholipids were exposed to Pseudomonas aeruginosa and Staphylococcus aureus. After 18 h incubation, the numbers of P. aeruginosa or S. aureus that adhered to the lenses were measured. Phospholipid was tested for possible effects on bacterial growth. RESULTS.: A broad range of sphingomyelins (SM) and phosphatidylcholines (PC) were detected from both types of worn lenses. SM (16:0) (m/z 703) and PC (34:2) (m/z 758) were the major phospholipids detected in the lens extracts. Phospholipids did not alter the adhesion of any strain of P. aeruginosa or S. aureus (p > 0.05). Phospholipids (0.1 mg/mL) showed no effect on the growth of P. aeruginosa 6294 or S. aureus 031. CONCLUSIONS.: Phospholipids adsorb/absorb to contact lenses during wear, however, the major types of phospholipids adsorbed to lenses do not alter bacterial adhesion or growth.10 page(s

‘You can't stay away from your family’: a qualitative study of the ongoing ties and future plans of South African health workers in the United Kingdom

Background: Migration of African-trained health workers to countries with higher health care worker densities adds to the severe shortage of health personnel in many African countries. Policy initiatives to reduce migration levels are informed by many studies exploring the reasons for the original decision to migrate. In contrast, there is little evidence to inform policies designed to facilitate health workers returning home or providing other forms of support to the health system of their home country. Objective: This study explores the links that South African-trained health workers who now live and work in the United Kingdom maintain with their country of training and what their future migration plans may be. Design: Semi-structured interviews were conducted with South African trained health workers who are now living in the United Kingdom. Data extracts from the interviews relating to current links with South Africa and future migration plans were studied. Results: All 16 participants reported strong ongoing ties with South Africa, particularly through active communication with family and friends, both face-to-face and remotely. Being South African was a significant part of their personal identity, and many made frequent visits to South Africa. These visits sometimes incorporated professional activities such as medical work, teaching, and charitable or business ventures in South Africa. The presence and location of family and spouse were of principal importance in helping South African-trained health care workers decide whether to return permanently to work in South Africa. Professional aspirations and sense of duty were also important motivators to both returning and to being involved in initiatives remotely from the United Kingdom. Conclusions: The main barrier to returning home was usually the development of stronger family ties in the United Kingdom than in South Africa. The issues that prompted the original migration decision, such as security and education, also remained important reasons to remain in the United Kingdom as long as they were perceived as unresolved at home. However, the strong residual feeling of identity and regular ongoing communication meant that most participants expressed a sense of duty to their home country, even if they were unlikely to return to live there full-time. This is a resource for training and short-term support that could be utilised to the benefit of African health care systems