A novel T‐cell receptor mimic defines dendritic cells that present an immunodominant West Nile virus epitope in mice

We used a newly generated T‐cell receptor mimic monoclonal antibody (TCRm MAb) that recognizes a known nonself immunodominant peptide epitope from West Nile virus (WNV) NS4B protein to investigate epitope presentation after virus infection in C57BL/6 mice. Previous studies suggested that peptides of different length, either SSVWNATTAI (10‐mer) or SSVWNATTA (9‐mer) in complex with class I MHC antigen H‐2D^b, were immunodominant after WNV infection. Our data establish that both peptides are presented on the cell surface after WNV infection and that CD8⁺ T cells can detect 10‐ and 9‐mer length variants similarly. This result varies from the idea that a given T‐cell receptor (TCR) prefers a single peptide length bound to its cognate class I MHC. In separate WNV infection studies with the TCRm MAb, we show that in vivo the 10‐mer was presented on the surface of uninfected and infected CD8α⁺CD11c⁺ dendritic cells, which suggests the use of direct and cross‐presentation pathways. In contrast, CD11b⁺CD11c^? cells bound the TCRm MAb only when they were infected. Our study demonstrates that TCR recognition of peptides is not limited to certain peptide lengths and that TCRm MAbs can be used to dissect the cell‐type specific mechanisms of antigen presentation in vivo.     

Identification of human neutralizing antibodies that bind to complex epitopes on dengue virions

Dengue is a mosquito-borne flavivirus that is spreading at an unprecedented rate and has developed into a major health and economic burden in over 50 countries. Even though infected individuals develop potent and long-lasting serotype-specific neutralizing antibodies (Abs), the epitopes engaged by human neutralizing Abs have not been identified. Here, we demonstrate that the dengue virus (DENV)-specific serum Ab response in humans consists of a large fraction of cross-reactive, poorly neutralizing Abs and a small fraction of serotype-specific, potently inhibitory Abs. Although many mouse-generated, strongly neutralizing monoclonal antibodies (mAbs) recognize epitopes that are present on recombinant DENV envelope (E) proteins, unexpectedly, the majority of neutralizing Abs in human immune sera bound to intact virions but not to the ectodomain of purified soluble E proteins. These conclusions with polyclonal Abs were confirmed with newly generated human mAbs derived from DENV-immune individuals. Two of three strongly neutralizing human mAbs bound to E protein epitopes that were preserved on the virion but not on recombinant E (rE) protein. We propose that humans produce Abs that neutralize DENV infection by binding a complex, quaternary structure epitope that is expressed only when E proteins are assembled on a virus particle. Mapping studies indicate that this epitope has a footprint that spans adjacent E protein dimers and includes residues at the hinge between domains I and II of E protein. These results have significant implications for the DENV Ab and vaccine field.     

Melatonin attenuates hypochlorous acid-mediated heme destruction, free iron release, and protein aggregation in hemoglobin

Abstract: In inflammatory diseases, where hypochlorous acid (HOCl) is elevated, iron homeostasis is disturbed, resulting in accumulation of free iron. Free iron is toxic by virtue of its ability to generate free radicals through the Fenton reaction. HOCl is generated by myeloperoxidase, (MPO) using chloride and hydrogen peroxide as substrates. Recent studies demonstrate that HOCl binds to the heme moiety of hemoglobin (Hb), which generates a transient ferric species whose formation and decay kinetics indicate it participates in protein aggregation, heme destruction, and free iron release. Here, we show that melatonin prevents HOCl‐mediated Hb heme destruction and protein aggregation, using a combination of UV‐vis spectrophotometry, ferrozine colorimetric assay, and in‐gel heme staining. We also show that melatonin treatment prevents HOCl‐mediated loss of red blood cell (RBC) viability, indicating biologic relevance of this finding. The mechanism by which melatonin prevents HOCl‐mediated Hb heme destruction is by direct scavenging of HOCl and/or through the destabilization of the higher Hb oxidative states intermediates, ferryl porphyrin radical cation Hb‐Fe(IV)=O^+π? and Hb‐Fe(IV)=O, which are formed through the reaction of HOCl with Hb. Our work establishes a direct mechanistic link between melatonin and its protective effect in chronic inflammatory diseases. Collectively, in addition to acting as an antioxidant and as a MPO inhibitor, melatonin can also exert its protective effect by inhibiting HOCl‐mediated heme destruction of hemoproteins and subsequent free iron release.     

An assessment of brief group interventions to increase condom use by heterosexual crack smokers living with HIV infection

The purpose of this study was to assess the efficacy of brief group interventions, the positive choices intervention (PCI) and a standard intervention (SI), to increase condom use and intention to use condoms and to change condom use attitudes and beliefs. The design of the study was a randomized comparative trial. Participants were 347 heterosexual African American crack cocaine users living with HIV infection. Data were collected at intake and at three and nine months after intake. Behavioral and sociocognitive data were collected. Although both brief interventions achieved positive results, there were significant differences in outcomes between the interventions groups. The mean number of sex partners was significantly lower in the PCI group at three months. The proportion of those assigned to the PCI reporting sex with a paid partner significantly decreased, while the proportion disclosing their serostatus to their partners increased. There were no significant differences on these measures in the SI group. Significant time effects were found on measures of condom use, condom use attitudes, and self-efficacy beliefs. These measures significantly increased from intake to one month for both groups. One significant time-by-group effect was found. The measure of situational self-efficacy significantly increased in the PCI group, but not the SI group. Results also showed significant time-by-time effects. Mean condom use, intention to use condoms, attitudes, and condom use self-efficacy beliefs showed significant difference between three and nine months. However, there was no clear pattern of change. Findings suggest that brief group interventions designed to reduce HIV can help heterosexual drug users living with HIV infection increase condom use and intention to use condoms and change condom use attitudes and beliefs. A significant time-by-group effect was observed only for situational self-efficacy, suggesting limited additional efficacy of the PCI intervention. Given similar positive findings between groups, more research is needed to determine which components of brief interventions produce changes in motivations and risk behaviors.     

Lung-enriched Organisms and Aberrant Bacterial and Fungal Respiratory Microbiota after Lung Transplant

Rationale: Long-term survival after lung transplantation is limited by infectious complications and by bronchiolitis obliterans syndrome (BOS), a form of chronic rejection linked in part to microbial triggers. Objectives: To define microbial populations in the respiratory tract of transplant patients comprehensively using unbiased high-density sequencing. Methods: Lung was sampled by bronchoalveolar lavage (BAL) and upper respiratory tract by oropharyngeal wash (OW). Bacterial 16S rDNA and fungal internal transcribed spacer sequencing was used to profile organisms present. Outlier analysis plots defining taxa enriched in lung relative to OW were used to identify bacteria enriched in lung against a background of oropharyngeal carryover. Measurements and Main Results: Lung transplant recipients had higher bacterial burden in BAL than control subjects, frequent appearance of dominant organisms, greater distance between communities in BAL and OW indicating more distinct populations, and decreased respiratory tract microbial richness and diversity. Fungal populations were typically dominated by Candida in both sites or by Aspergillus in BAL but not OW. 16S outlier analysis identified lung-enriched taxa indicating bacteria replicating in the lower respiratory tract. In some cases this confirmed respiratory cultures but in others revealed enrichment by anaerobic organisms or mixed outgrowth of upper respiratory flora and provided quantitative data on relative abundances of bacteria found by culture. Conclusions: Respiratory tract microbial communities in lung transplant recipients differ in structure and composition from healthy subjects. Outlier analysis can identify specific bacteria replicating in lung. These findings provide novel approaches to address the relationship between microbial communities and transplant outcome and aid in assessing lung infections.     

Variation in PTX3 Is Associated with Primary Graft Dysfunction after Lung Transplantation

Rationale: Elevated long pentraxin-3 (PTX3) levels are associated with the development of primary graft dysfunction (PGD) after lung transplantation. Abnormalities in innate immunity, mediated by PTX3 release, may play a role in PGD pathogenesis. Objectives: Our goal was to test whether variants in the gene encoding PTX3 are risk factors for PGD. Methods: We performed a candidate gene association study in recipients from the multicenter, prospective Lung Transplant Outcomes Group cohort enrolled between July 2002 and July 2009. The primary outcome was International Society for Heart and Lung Transplantation grade 3 PGD within 72 hours of transplantation. Targeted genotyping of 10 haplotype-tagging PTX3 single-nucleotide polymorphisms (SNPs) was performed in lung transplant recipients. The association between PGD and each SNP was evaluated by logistic regression, adjusting for pretransplantation lung disease, cardiopulmonary bypass use, and population stratification. The association between SNPs and plasma PTX3 levels was tested across genotypes in a subset of recipients with idiopathic pulmonary fibrosis. Measurements and Main Results: Six hundred fifty-four lung transplant recipients were included. The incidence of PGD was 29%. Two linked 5' region variants, rs2120243 and rs2305619, were associated with PGD (odds ratio, 1.5; 95% confidence interval, 1.1 to 1.9; P = 0.006 and odds ratio, 1.4; 95% confidence interval, 1.1 to 1.9; P = 0.007, respectively). The minor allele of rs2305619 was significantly associated with higher plasma PTX3 levels measured pretransplantation (P = 0.014) and at 24 hours (P = 0.047) after transplantation in patients with idiopathic pulmonary fibrosis. Conclusions: Genetic variants of PTX3 are associated with PGD after lung transplantation, and are associated with increased PTX3 plasma levels.