A Neutralizing Antibody Recognizing Primarily N-Linked Glycan Targets the Silent Face of the HIV Envelope.

Virtually the entire surface of the HIV-1-envelope trimer is recognized by neutralizing antibodies, except for a highly glycosylated region at the center of the "silent face" on the gp120 subunit. From an HIV-1-infected donor, #74, we identified antibody VRC-PG05, which neutralized 27% of HIV-1 strains. The crystal structure of the antigen-binding fragment of VRC-PG05 in complex with gp120 revealed an epitope comprised primarily of N-linked glycans from N262, N295, and N448 at the silent face center. Somatic hypermutation occurred preferentially at antibody residues that interacted with these glycans, suggesting somatic development of glycan recognition. Resistance to VRC-PG05 in donor #74 involved shifting of glycan-N448 to N446 or mutation of glycan-proximal residue E293. HIV-1 neutralization can thus be achieved at the silent face center by glycan-recognizing antibody; along with other known epitopes, the VRC-PG05 epitope completes coverage by neutralizing antibody of all major exposed regions of the prefusion closed trimer.

Essential role of Elmo1 in Dock2-dependent lymphocyte migration.

Elmo1 and Elmo2 are highly homologous cytoplasmic adaptor proteins that interact with Dock family guanine nucleotide exchange factors to promote activation of the small GTPase Rac. In T lymphocytes, Dock2 is essential for CCR7- and CXCR4-dependent Rac activation and chemotaxis, but the role of Elmo proteins in regulating Dock2 function in primary T cells is not known. In this article, we show that endogenous Elmo1, but not Elmo2, interacts constitutively with Dock2 in mouse and human primary T cells. CD4(+) T cells from Elmo1(-/-) mice were profoundly impaired in polarization, Rac activation, and chemotaxis in response to CCR7 and CXCR4 stimulation. Transfection of full-length Elmo1, but not Elmo2 or a Dock2-binding mutant of Elmo1, rescued defective migration of Elmo1(-/-) T cells. Interestingly, Dock2 protein levels were reduced by 4-fold in Elmo1(-/-) lymphocytes despite normal levels of Dock2 mRNA. Dock2 polyubiquitination was increased in Elmo1(-/-) T cells, and treatment with proteasome inhibitors partially restored Dock2 levels in Elmo1(-/-) T cells. Finally, we show that Dock2 is directly ubiquitinated in CD4(+) T cells and that Elmo1 expression in heterologous cells inhibits ubiquitination of Dock2. Taken together, these findings reveal a previously unknown, nonredundant role for Elmo1 in controlling Dock2 levels and Dock2-dependent T cell migration in primary lymphocytes. Inhibition of Dock2 has therapeutic potential as a means to control recruitment of pathogenic lymphocytes in diseased tissues. This work provides valuable insights into the molecular regulation of Dock2 by Elmo1 that can be used to design improved inhibitors that target the Elmo-Dock-Rac signaling complex.

Comprehensive proteomic analysis of influenza virus polymerase complex reveals a novel association with mitochondrial proteins and RNA polymerase accessory factors.

The trimeric RNA polymerase complex (3P, for PA-PB1-PB2) of influenza A virus (IAV) is an important viral determinant of pathogenicity and host range restriction. Specific interactions of the polymerase complex with host proteins may be determining factors in both of these characteristics and play important roles in the viral life cycle. To investigate this question, we performed a comprehensive proteomic analysis of human host proteins associated with the polymerase of the well-characterized H5N1 Vietnam/1203/04 isolate. We identified over 400 proteins by liquid chromatography-tandem mass spectrometry (LC-MS/MS), of which over 300 were found to bind to the PA subunit alone. The most intriguing and novel finding was the large number of mitochondrial proteins (∼20%) that associated with the PA subunit. These proteins mediate molecular transport across the mitochondrial membrane or regulate membrane potential and may in concert with the identified mitochondrion-associated apoptosis inducing factor (AIFM1) have roles in the induction of apoptosis upon association with PA. Additionally, we identified host factors that associated with the PA-PB1 (68 proteins) and/or the 3P complex (34 proteins) including proteins that have roles in innate antiviral signaling (e.g., ZAPS or HaxI) or are cellular RNA polymerase accessory factors (e.g., polymerase I transcript release factor [PTRF] or Supt5H). IAV strain-specific host factor binding to the polymerase was not observed in our analysis. Overall, this study has shed light into the complex contributions of the IAV polymerase to host cell pathogenicity and allows for direct investigations into the biological significance of these newly described interactions.

Preventing Hepatitis B Virus Infection Among U.S. Military Personnel: Potential Impact of a 2-Dose Versus 3-Dose Vaccine on Medical Readiness.

INTRODUCTION: Hepatitis B, a major public health issue worldwide, has been associated with serious clinical outcomes. Military personnel are at particular risk for hepatitis B, such that hepatitis B vaccination is part of the accession process for new recruits. Although lost time costs and medical cost avoidance have been used by the U.S. Military to guide their decision-making protocols, this has not been applied to hepatitis B vaccination costs. Herein, a decision-analytic model is used to compare the effective vaccine protection rates and vaccine and operational costs of 2-dose versus 3-dose hepatitis B vaccine regimens in a population of recruits from the U.S. Marine Corps Recruit Depot, Parris Island. METHODS: A decision-analytic model was developed to assess the expected levels of adherence, seroprotection, and vaccination and operational costs of a cohort of recruits vaccinated with either a 2-dose (HepB-CpG) vaccine for those eligible (scenario 1) or a 3-dose (HepB-Alum) vaccine (scenario 2). De-identified data from 23,004 recruits at the Marine Corps Recruit Depot, Parris Island, in 2018 and 2019 were used to provide real-world data on age distribution and vaccination status. Other inputs included published data on adherence for hepatitis B vaccines and seroprotection rates for HepB-CpG and HepB-Alum in relation to the number of doses received. Costs included direct medical costs of the hepatitis B vaccination and operational costs such as missed training time. RESULTS: After receipt of two vaccine doses, 92% of recruits in scenario 1 (HepB-CpG group) were expected to be protected against hepatitis B within 1 month of receiving the second dose, compared with 24% of recruits in scenario 2 (HepB-Alum group), leaving 76% of Marine recruits unprotected if using HepB-Alum during the intervening 5-month period between doses 2 and 3. Over the study period, HepB-CpG was estimated to provide cost savings of $744,509 (17.3% cost reduction) compared with HepB-Alum, with the cost of missed training time being the most influential driver of the cost difference between the two vaccination schedules. CONCLUSIONS: Findings from this model suggest that vaccination with the 2-dose HepB-CpG vaccine may provide earlier and higher protection against hepatitis B compared with the 3-dose vaccine (HepB-Alum). A 2-dose vaccination strategy incorporated as part of individual medical readiness has the potential to not only increase protection but also confer economic savings among military recruits at risk for hepatitis B infection.

Adult immunization against hepatitis B: Does the number of jabs matter?

BACKGROUND: At least one-half of adults beginning an immunization series with a three-dose hepatitis B virus (HBV) vaccine (ENGERIX-B, RECOMBIVAX-B) have been reported not to receive the third dose. Use of a two-dose vaccine may improve adherence and lead to greater overall levels of seroprotection. OBJECTIVE: To examine expected levels of adherence and overall seroprotection at one year among adults in routine clinical settings beginning an immunization series with either ENGERIX-B or the two-dose HBV vaccine, HEPLISAV-B. METHODS: Decision-analytic model comparing expected levels of adherence and overall seroprotection at one year among a hypothetical cohort of one million previously unvaccinated adults aged ≥ 30 years receiving first doses of either ENGERIX-B or HEPLISAV-B in a routine clinical setting. We stratified the population by age (30-49 years vs ≥ 50 years) to allow for possible differences in adherence and seroprotection. We estimated our model using published adherence rates for HBV vaccines, and reported seroprotection rates by number of doses administered. We also compared total expected costs of HBV immunization with each vaccine. RESULTS: Use of a two-dose rather than three-dose HBV vaccine would increase the expected number of adults seroprotected at one year by 275,000 per one million persons beginning immunization series, largely reflecting a gain of 290,000 in the expected number of persons fully vaccinated. Results were similar for the two age groups. While the cost per dose of HEPLISAV-B exceeds that of ENGERIX-B, its estimated mean cost per person seroprotected at one year is $50-$70 (∼15%) lower. CONCLUSIONS: Use of a two-dose HBV vaccine would increase the number of adults fully seroprotected at one year compared with the number expected with a three-dose vaccine. Notwithstanding its higher unit cost, mean expected cost per person seroprotected is substantially lower for HEPLISAV-B than ENGERIX-B as a result of much higher levels of seroprotection.

Preventing hepatitis B virus infection among healthcare professionals: potential impact of a 2-dose versus 3-dose vaccine.

The exposure risk to the highly infectious hepatitis B virus (HBV) is an established and recognizable hazard to healthcare professionals (HCPs). In the United States, implementing preemptive vaccination programs and safety procedures resulted in drastic reductions in HBV infections among HCPs; however, many HCPs remain unprotected and risk of exposure persists, especially among those first entering a healthcare system and undergoing professional training. First-generation HBV vaccines require completion of a 3-dose schedule over a 6-month interval for maximum immunogenicity. By comparison, HepB-CpG (HEPLISAV-B®) is a 2-dose HBV vaccine licensed in the United States in 2017, inducing rapid seroprotection over a 1-month interval and may represent a more effective strategy for combating HBV infection in US healthcare systems. In this modeling study, the health and economic impact of implementing an HBV vaccination strategy with HepB-CpG versus the 3-dose HBV vaccine (Engerix-B®) was evaluated among HCPs newly entering a healthcare system. The model used effective seroprotection rate, a real-world metric accounting for HCP vaccine compliance and seroprotection rates for different dosing regimens and considered current pricing for postexposure prophylaxis treatment. Compared with the 3-dose vaccine, HepB-CpG was anticipated to provide faster, increased protection against HBV infection among newly entered HCPs. In protecting a greater percentage of HCPs, HepB-CpG was also projected to substantially reduce the risk of HBV exposure. Accordingly, an economic analysis showed HepB-CpG vaccination would reduce costs of postexposure prophylaxis treatment compared with the 3-dose vaccine. Overall, HepB-CpG represents an effective therapeutic strategy against HBV infection for US healthcare systems.

Diabetes and tuberculosis: the impact of the diabetes epidemic on tuberculosis incidence.

BACKGROUND: Tuberculosis (TB) remains a major cause of mortality in developing countries, and in these countries diabetes prevalence is increasing rapidly. Diabetes increases the risk of TB. Our aim was to assess the potential impact of diabetes as a risk factor for incident pulmonary tuberculosis, using India as an example. METHODS: We constructed an epidemiological model using data on tuberculosis incidence, diabetes prevalence, population structure, and relative risk of tuberculosis associated with diabetes. We evaluated the contribution made by diabetes to both tuberculosis incidence, and to the difference between tuberculosis incidence in urban and rural areas. RESULTS: In India in 2000 there were an estimated 20.7 million adults with diabetes, and 900,000 incident adult cases of pulmonary tuberculosis. Our calculations suggest that diabetes accounts for 14.8% (uncertainty range 7.1% to 23.8%) of pulmonary tuberculosis and 20.2% (8.3% to 41.9%) of smear-positive (i.e. infectious) tuberculosis. We estimate that the increased diabetes prevalence in urban areas is associated with a 15.2% greater smear-positive tuberculosis incidence in urban than rural areas - over a fifth of the estimated total difference. CONCLUSION: Diabetes makes a substantial contribution to the burden of incident tuberculosis in India, and the association is particularly strong for the infectious form of tuberculosis. The current diabetes epidemic may lead to a resurgence of tuberculosis in endemic regions, especially in urban areas. This potentially carries a risk of global spread with serious implications for tuberculosis control and the achievement of the United Nations Millennium Development Goals.

Diabetes and the risk of tuberculosis: a neglected threat to public health?

OBJECTIVES: Tuberculosis (TB) remains a major global public health problem. In the past, a relationship between TB and diabetes mellitus (DM) was recognized, and its importance was acknowledged through joint treatment clinics. However, this is rarely highlighted in current research or control priorities. This paper aims to evaluate the evidence for an association between these two diseases. METHODS: A Medline literature search was undertaken, supplemented by checking references and contacting experts. We critically appraised studies that quantified the association between TB and DM, and were published after 1995. We assessed study quality according to criteria such as sample size, method of selection of cases and controls, losses to follow-up, quality and method of control of confounding, and summarized the results narratively and in tabular form. RESULTS: All studies identified statistically significant and clinically important associations, with the increase in risk or odds of TB varying between 1.5- and 7.8-fold for those with DM. Risk was highest at younger ages. Most studies had not measured and controlled adequately for potential major confounders. DISCUSSION: There is strong evidence for an association between TB and DM, which has potential public health implications. Further well-designed studies are needed to assess the magnitude precisely.

Salmonella-induced SipB-independent cell death requires Toll-like receptor-4 signalling via the adapter proteins Tram and Trif.

Salmonella enterica serovar typhimurium (S. typhimurium) is an intracellular pathogen that causes macrophage cell death by at least two different mechanisms. Rapid cell death is dependent on the Salmonella pathogenicity island-1 protein SipB whereas delayed cell death is independent of SipB and occurs 18-24 hr post infection. Lipopolysaccharide (LPS) is essential for the delayed cell death. LPS is the main structural component of the outer membrane of Gram-negative bacteria and is recognized by Toll-like receptor 4, signalling via the adapter proteins Mal, MyD88, Tram and Trif. Here we show that S. typhimurium induces SipB-independent cell death through Toll-like receptor 4 signalling via the adapter proteins Tram and Trif. In contrast to wild type bone marrow derived macrophages (BMDM), Tram(-/-) and Trif(-/-) BMDM proliferate in response to Salmonella infection.