Supramolecular assemblies underpin turnover of outer membrane proteins in bacteria.

Gram-negative bacteria inhabit a broad range of ecological niches. For Escherichia coli, this includes river water as well as humans and animals, where it can be both a commensal and a pathogen. Intricate regulatory mechanisms ensure that bacteria have the right complement of ß-barrel outer membrane proteins (OMPs) to enable adaptation to a particular habitat. Yet no mechanism is known for replacing OMPs in the outer membrane, an issue that is further confounded by the lack of an energy source and the high stability and abundance of OMPs. Here we uncover the process underpinning OMP turnover in E. coli and show it to be passive and binary in nature, in which old OMPs are displaced to the poles of growing cells as new OMPs take their place. Using fluorescent colicins as OMP-specific probes, in combination with ensemble and single-molecule fluorescence microscopy in vivo and in vitro, as well as molecular dynamics simulations, we established the mechanism for binary OMP partitioning. OMPs clustered to form ∼0.5-µm diameter islands, where their diffusion is restricted by promiscuous interactions with other OMPs. OMP islands were distributed throughout the cell and contained the Bam complex, which catalyses the insertion of OMPs in the outer membrane. However, OMP biogenesis occurred as a gradient that was highest at mid-cell but largely absent at cell poles. The cumulative effect is to push old OMP islands towards the poles of growing cells, leading to a binary distribution when cells divide. Hence, the outer membrane of a Gram-negative bacterium is a spatially and temporally organized structure, and this organization lies at the heart of how OMPs are turned over in the membrane.

The clinical academic workforce in Australia and New Zealand: report on the second binational summit to implement a sustainable training pathway.

There has been a decline in the proportion of clinical academics compared with full-time clinicians, since 2004. A Working Party was established to help develop and implement a model for the training of clinical academics. After a highly successful first summit in 2014 that summarised the challenges faced by clinical academics in Australia and New Zealand, a second summit was convened late in 2015 to report on progress and to identify key areas for further action. The second summit provided survey results that identified the varied training pathways currently offered to clinical academics and the institutions willing to be involved in developing improved pathways. A literature review also described the contributions that clinical academics make to the health sector and the challenges faced by this workforce sector. Current training pathways created for clinical academics by Australasian institutions were presented as examples of what can be done. The perspectives of government and research organisations presented at the summit helped define how key stakeholders can contribute. Following the summit, there was a strong commitment to continue to work towards developing a sustainable and defined training pathway for clinical academics. The need for a coordinated and integrated approach was highlighted. Some key objectives were agreed upon for the next phase, including identifying and engaging key advocates within government and leading institutions; publishing and profiling the contributions of successful clinical academics to healthcare outcomes; defining the stages of a clinical academic training pathway; and establishing a mentoring programme for training clinical academics.

A Multiantigenic DNA Vaccine That Induces Broad Hepatitis C Virus-Specific T-Cell Responses in Mice.

UNLABELLED: There are 3 to 4 million new hepatitis C virus (HCV) infections annually around the world, but no vaccine is available. Robust T-cell mediated responses are necessary for effective clearance of the virus, and DNA vaccines result in a cell-mediated bias. Adjuvants are often required for effective vaccination, but during natural lytic viral infections damage-associated molecular patterns (DAMPs) are released, which act as natural adjuvants. Hence, a vaccine that induces cell necrosis and releases DAMPs will result in cell-mediated immunity (CMI), similar to that resulting from natural lytic viral infection. We have generated a DNA vaccine with the ability to elicit strong CMI against the HCV nonstructural (NS) proteins (3, 4A, 4B, and 5B) by encoding a cytolytic protein, perforin (PRF), and the antigens on a single plasmid. We examined the efficacy of the vaccines in C57BL/6 mice, as determined by gamma interferon enzyme-linked immunosorbent spot assay, cell proliferation studies, and intracellular cytokine production. Initially, we showed that encoding the NS4A protein in a vaccine which encoded only NS3 reduced the immunogenicity of NS3, whereas including PRF increased NS3 immunogenicity. In contrast, the inclusion of NS4A increased the immunogenicity of the NS3, NS4B, andNS5B proteins, when encoded in a DNA vaccine that also encoded PRF. Finally, vaccines that also encoded PRF elicited similar levels of CMI against each protein after vaccination with DNA encoding NS3, NS4A, NS4B, and NS5B compared to mice vaccinated with DNA encoding only NS3 or NS4B/5B. Thus, we have developed a promising "multiantigen" vaccine that elicits robust CMI. IMPORTANCE: Since their development, vaccines have reduced the global burden of disease. One strategy for vaccine development is to use commercially viable DNA technology, which has the potential to generate robust immune responses. Hepatitis C virus causes chronic liver infection and is a leading cause of liver cancer. To date, no vaccine is currently available, and treatment is costly and often results in side effects, limiting the number of patients who are treated. Despite recent advances in treatment, prevention remains the key to efficient control and elimination of this virus. Here, we describe a novel DNA vaccine against hepatitis C virus that is capable of inducing robust cell-mediated immune responses in mice and is a promising vaccine candidate for humans.

DNA vaccines encoding membrane-bound or secreted forms of heat shock protein 70 exhibit improved potency.

Traditional vaccine strategies are inefficient against challenge with complex pathogens including HIV; therefore, novel vaccine technologies are required. DNA vaccines are attractive as they are relatively cheap and easy to manufacture, but a major limitation has been their lack of immunogenicity in humans, which may be overcome with the incorporation of an adjuvant. HSP70 is a recognised damage-associated molecular pattern, which is a potential adjuvant. We investigated the immunogenicity of a DNA vaccine encoding HIV gag and HSP70; the latter was genetically modified to produce cytoplasmic, secreted or membrane-bound HSP70, the expression of which was controlled by an independent promoter. The DNA was administered to C57BL/6 mice to evaluate gag-specific T-cell responses. Our results demonstrated the ability of membrane-bound and secreted HSP70 to significantly enhance gag-specific T-cell responses and increase the breadth of T-cell responses to include subdominant epitopes. Membrane-bound or secreted HSP70 also significantly improved the multifunctionality of HIV-specific T cells and T-cell proliferation, which is important for maintaining T-cell integrity. Most importantly, the inclusion of membrane-bound HSP70, secreted HSP70 or a combination significantly increased protection in mice challenged with EcoHIV, a chimeric virus that replicates in mouse leukocytes in vivo.

Induction of antigen-positive cell death by the expression of perforin, but not DTa, from a DNA vaccine enhances the immune response.

The failure of traditional protein-based vaccines to prevent infection by viruses such as HIV or hepatitis C highlights the need for novel vaccine strategies. DNA vaccines have shown promise in small animal models, and are effective at generating anti-viral T cell-mediated immune responses; however, they have proved to be poorly immunogenic in clinical trials. We propose that the induction of necrosis will enhance the immune response to vaccine antigens encoded by DNA vaccines, as necrotic cells are known to release a range of intracellular factors that lead to dendritic cell (DC) activation and enhanced cross-presentation of antigen. Here we provide evidence that induction of cell death in DNA vaccine-targeted cells provides an adjuvant effect following intradermal vaccination of mice; however, this enhancement of the immune response is dependent on both the mechanism and timing of cell death after antigen expression. We report that a DNA vaccine encoding the cytolytic protein, perforin, resulted in DC activation, enhanced broad and multifunctional CD8 T-cell responses to the HIV-1 antigen GAG and reduced viral load following challenge with a chimeric virus, EcoHIV, compared with the canonical GAG DNA vaccine. This effect was not observed for a DNA vaccine encoding an apoptosis-inducing toxin, DTa, or when the level of perforin expression was increased to induce cell death sooner after vaccination. Thus, inducing lytic cell death following a threshold level of expression of a viral antigen can improve the immunogenicity of DNA vaccines, whereas apoptotic cell death has an inhibitory effect on the immune response.

A qualitative study of the incentives and barriers that influence preferences for rural placements during surgical training in Australia.

BACKGROUND: Rural exposure of long durations during clinical training is positively associated with rural career uptake and is a central strategy to addressing the geographical maldistribution of Australia's surgical workforce. However, the incentives and barriers to trainees undergoing surgical training preferencing repeated rural placements in Australia are not well understood. This qualitative study explores the incentives and barriers that influence preference for rural placements during surgical training in Australia. METHODS: This qualitative study employed online semi-structured in-depth interviews. Participants were recruited using an online survey, and interviews were conducted between October 2020 and November 2020. Transcripts were transcribed and de-identified, and thematically analysed. RESULTS: Twenty-nine semi-structured interviews were conducted with trainees and 12 Fellows. Twenty-five participants identified as male, and four identified as female. Four main incentives identified were: (1) broad scope of learning opportunities, (2) quality of supervision, (3) positive work environment and (4) lifestyle. Seven barriers identified were: (1) inadequate preparation for placement, (2) limited case mix to support learning outcomes, (3) lack of formally structured learning opportunities, (4) workload and safe hours concerns, (5) lack of peer support, (6) childcare and educational needs and (7) partner career development. CONCLUSION: The strategy of encouraging trainees to undertake rural placements to address the maldistribution of the surgical workforce should include initiatives that support learning outcomes across their training levels. In addition, improving trainees' ability to prepare adequately for placements may also improve the number and duration of rural placements trainees undertake during their training.

Impact of COVID-19, gender, race, specialty and seniority on mental health during surgical training: an international study.

BACKGROUND: Superior patient outcomes rely on surgical training being optimized. Accordingly, we conducted an international, prospective, cross-sectional study determining relative impacts of COVID-19, gender, race, specialty and seniority on mental health of surgical trainees. METHOD: Trainees across Australia, New Zealand and UK enrolled in surgical training accredited by the Royal Australasian College of Surgeons or Royal College of Surgeons were included. Outcomes included the short version of the Perceived Stress Scale, Oxford Happiness Questionnaire short scale, Patient Health Questionnaire-2 and the effect on individual stress levels of training experiences affected by COVID-19. Predictors included trainee characteristics and local COVID-19 prevalence. Multivariable linear regression analyses were conducted to assess association between outcomes and predictors. RESULTS: Two hundred and five surgical trainees were included. Increased stress was associated with number of COVID-19 patients treated (P = 0.0127), female gender (P = 0.0293), minority race (P = 0.0012), less seniority (P = 0.001), and greater COVID-19 prevalence (P = 0.0122). Lower happiness was associated with training country (P = 0.0026), minority race (P = 0.0258) and more seniority (P < 0.0001). Greater depression was associated with more seniority (P < 0.0001). Greater COVID-19 prevalence was associated with greater reported loss of training opportunities (P = 0.0038), poor working conditions (P = 0.0079), personal protective equipment availability (P = 0.0008), relocation to areas of little experience (P < 0.0001), difficulties with career progression (P = 0.0172), loss of supervision (P = 0.0211), difficulties with pay (P = 0.0034), and difficulties with leave (P = 0.0002). CONCLUSION: This is the first study to specifically describe the relative impacts of COVID-19 community prevalence, gender, race, surgical specialty and level of seniority on stress, happiness and depression of surgical trainees on an international scale.

A HIV-Tat/C4-binding protein chimera encoded by a DNA vaccine is highly immunogenic and contains acute EcoHIV infection in mice.

DNA vaccines are cost-effective to manufacture on a global scale and Tat-based DNA vaccines have yielded protective outcomes in preclinical and clinical models of human immunodeficiency virus (HIV), highlighting the potential of such vaccines. However, Tat-based DNA vaccines have been poorly immunogenic, and despite the administration of multiple doses and/or the addition of adjuvants, these vaccines are not in general use. In this study, we improved Tat immunogenicity by fusing it with the oligomerisation domain of a chimeric C4-binding protein (C4b-p), termed IMX313, resulting in Tat heptamerisation and linked Tat to the leader sequence of tissue plasminogen activator (TPA) to ensure that the bulk of heptamerised Tat is secreted. Mice vaccinated with secreted Tat fused to IMX313 (pVAX-sTat-IMX313) developed higher titres of Tat-specific serum IgG, mucosal sIgA and cell-mediated immune (CMI) responses, and showed superior control of EcoHIV infection, a surrogate murine HIV challenge model, compared with animals vaccinated with other test vaccines. Given the crucial contribution of Tat to HIV-1 pathogenesis and the precedent of Tat-based DNA vaccines in conferring some level of protection in animal models, we believe that the virologic control demonstrated with this novel multimerised Tat vaccine highlights the promise of this vaccine candidate for humans.

Encoded novel forms of HSP70 or a cytolytic protein increase DNA vaccine potency.

In humans, DNA vaccines have failed to demonstrate the equivalent levels of immunogenicity that were shown in smaller animals. Previous studies have encoded adjuvants, predominantly cytokines, within these vaccines in an attempt to increase antigen-specific immune responses. However, these strategies have lacked breadth of innate immune activation and have led to disappointing results in clinical trials. Damage associated molecular patterns (DAMPs) have been identified as pattern recognition receptor (PRR) agonists. DAMPs can bind to a wide range of PRRs on dendritic cells (DCs) and thus our studies have aimed to utilize this characteristic to act as an adjuvant in a DNA vaccine approach. Specifically, HSP70 has been identified as a DAMP, but has been limited by its lack of accessibility to PRRs in and on DCs. Here, we discuss the promising results achieved with the inclusion of membrane-bound or secreted HSP70 into a DNA vaccine encoding HIV gag as the model immunogen.

A novel challenge model to evaluate the efficacy of hepatitis C virus vaccines in mice.

An effective hepatitis C virus (HCV) vaccine should elicit robust humoral and cell mediated immunity (CMI). A small animal challenge model is required to assess the efficacy of vaccines which elicit CMI. In this study, HCV proteins were expressed in hepatocytes of immunocompetent mice after hydrodynamic injection of a plasmid encoding the HCV NS3/4A protein. This vector, constructed as the "challenge", was optimized for long term, specific gene expression in hepatocytes. To monitor HCV antigen expression in transfected hepatocytes, the plasmid also encoded secreted alkaline phosphatase (SEAP), which was detected in the mouse serum. The design of this novel challenge plasmid was based on studies using luciferase and SEAP as reporter molecules to examine the kinetics of the proteins expressed in hepatocytes and secreted into blood. We designed two constructs to control SEAP expression. In one construct, SEAP expression was controlled by the EMCV IRES, while in the other, a SEAP and luciferase polyprotein was cleaved by the FMDV2A proteinase. We found that SEAP expressed after FMDV2A self cleavage was more sensitive and showed a higher correlation with luciferase expressed in liver. The NS3/4A challenge model using the FMDV2A design provided a window period of 50 days to monitor changes in SEAP expression after hydrodynamic injection of DNA. In a challenge experiment, mice which received an adenovirus-based HCV vaccine showed accelerated clearance of SEAP and thus, of NS3/4A positive hepatocytes compared with a mock vaccinated group, that coincided with an increased number of CD8(+) lymphocytes in the liver.

Loss of long term protection with the inclusion of HIV pol to a DNA vaccine encoding gag.

Traditional vaccine strategies that induce antibody responses have failed to protect against HIV infection in clinical trials, and thus cell-mediated immunity is now an additional criterion. Recent clinical trials that aimed to induce strong T cell responses failed to do so. Therefore, to enhance induction of protective T cell responses, it is crucial that the optimum antigen combination is chosen. Limited research has been performed into the number of antigens selected for an HIV vaccine. This study aimed to compare DNA vaccines encoding either a single HIV antigen or a combination of two antigens, using intradermal vaccination of C57BL/6 mice. Immune assays were performed on splenocytes, and in vivo protection was examined by challenge with a chimeric virus, EcoHIV, able to infect mouse but not human leukocytes, at 10 days (short term) and 60 days (long term) post final vaccination. At 60 days there was significantly lower frequency of induced antigen-specific CD8(+) T cells in the spleens of pCMVgag-pol-vaccinated mice compared with mice which received pCMVgag only. Most importantly, short term viral control of EcoHIV was similar for pCMVgag and pCMVgag-pol-vaccinated mice at day 10, but only the pCMVgag-vaccinated significantly controlled EcoHIV at day 60 compared with pCMV-vaccinated mice, showing that control was reduced with the inclusion of the HIV pol gene.

Increase in DNA vaccine efficacy by virosome delivery and co-expression of a cytolytic protein.

The potential of DNA vaccines has not been realised due to suboptimal delivery, poor antigen expression and the lack of localised inflammation, essential for antigen presentation and an effective immune response to the immunogen. Initially, we examined the delivery of a DNA vaccine encoding a model antigen, luciferase (LUC), to the respiratory tract of mice by encapsulation in a virosome. Virosomes that incorporated influenza virus haemagglutinin effectively delivered DNA to cells in the mouse respiratory tract and resulted in antigen expression and systemic and mucosal immune responses to the immunogen after an intranasal (IN) prime/intradermal (ID) boost regimen, whereas a multidose ID regimen only generated systemic immunity. We also examined systemic immune responses to LUC after ID vaccination with a DNA vaccine, which also encoded one of the several cytolytic or toxic proteins. Although the herpes simplex virus thymidine kinase, in the presence of the prodrug, ganciclovir, resulted in cell death, this failed to increase the humoral or cell-mediated immune responses. In contrast, the co-expression of LUC with the rotavirus non-structural protein 4 (NSP4) protein or a mutant form of mouse perforin, proteins which are directly cytolytic, resulted in increased LUC-specific humoral and cell-mediated immunity. On the other hand, co-expression of LUC with diphtheria toxin subunit A or overexpression of perforin or NSP4 resulted in a lower level of immunity. In summary, the efficacy of DNA vaccines can be improved by targeted IN delivery of DNA or by the induction of cell death in vaccine-targeted cells after ID delivery.