Genetic Control of Survival and Weight Loss during Pneumonic Burkholderia pseudomallei (Bp) Infection

Burkholderia pseudomallei (Bp) is a saprophytic, gram-negative aerobe and the causative agent of the disease melioidosis. Melioidosis is an infectious disease that occurs in humans and animals and is prevalent in Southeast Asia, northern Australia and other tropical areas. Transmission occurs through direct contact with the organism via ingestion, inhalation, or through open wounds and skin abrasions. Clinical presentation is extremely variable and can range from acute septicemia with bacterial dissemination to distant sites, to an isolated pulmonary infection. Treatment of melioidosis can be problematic because it is often difficult to diagnose and Bp is resistant to a diverse group of antibiotics. Even with treatment, the mortality rate of melioidosis is 20 to 50%. While this pathogen is not widespread in the United States, it is a significant U.S. health issue because of its high potential for use as a biological weapon. The US Centers for Disease Control and Prevention (CDC) and The Department of Health and Human Services (DHHS) has recognized Bp as a Tier 1 Select Agent, meaning there is no effective vaccine against this high morbidity/mortality disease. Furthermore, according the CDC, other factors including aerosol infectivity, the severity of infection, and the global distribution of this pathogen makes it a potential bioterrorism agent that poses a threat to national security, if intentionally released into populated areas. There has been little investigation into the role of host genetic background as it relates to susceptibility and/or resistance to Bp infection. It has been known for some time that inbred and recombinant inbred mice exhibit differences in susceptibility to many intracellular pathogens and are thought to provide excellent models for acute and chronic human melioidosis. Therefore, this project set out to identify host genetic elements that contribute to differential immune responsiveness and/or susceptibility to a Bp infection using a murine pneumonic challenge model. There is a high potential for discovery of host genes/genetic networks that confer resistance or sensitivity to this dangerous and emerging pathogen using inbred and BXD mouse strains as an in vivo modeling system of melioidosis. We have utilized recombinant inbred BXD mice and a powerful array of complementary computer-based modeling algorithms and databases collectively known as GeneNetwork. We infected parental mice and 32 BXD strains with 50-100 CFU of Bp (strain 1026b) and monitored survival and weight retention each day over an eleven-day time course. Initial studies revealed that Bp infection elicits phenotypically distinct innate immune responses in terms of survival and weight loss following pneumonic infection in parental and BXD mice. Using the computational tools in GeneNetwork, we performed genome-wide linkage analysis of our survival and weight loss phenotypic data to identify that survival is a complex trait involving loci on chromosomes 5 and 7 and weight retention involves loci on chromosome 12. We then analyzed and ranked several potential candidate genes within the significant and/or suggestive interval on these chromosomes that appear to correlate with differential susceptibility to Bp infection. Several genes have intriguing connections with innate immunity, regulation of Nf-kβ, apoptosis, cell cycle regulation, nervous system development, calcium homeostasis, lipid transport, host cell growth and development, and autophagy. To date, there have been few published studies that have identified specific host genetic elements that correlate with resistance and/or susceptibility to the acute form of melioidosis. Therefore, the identification of key host genetic factors that control resistance or susceptibility to Bp is of much importance. Results generated from this work will increase our understanding of the interactions between Bp and its genetically diverse hosts, which will enhance the understanding of Bp pathogenesis and increase the biological knowledge to help guide the progression and development of preventative and therapeutic measures to a Bp infection as well as other high morbidity/mortality respiratory pathogens

A galU mutant of francisella tularensis is attenuated for virulence in a murine pulmonary model of tularemia

<p>Abstract</p> <p>Background</p> <p>A number of studies have revealed that <it>Francisella tularensis </it>(FT) suppresses innate immune responses such as chemokine/cytokine production and neutrophil recruitment in the lungs following pulmonary infection via an unidentified mechanism. The ability of FT to evade early innate immune responses could be a very important virulence mechanism for this highly infectious bacterial pathogen.</p> <p>Results</p> <p>Here we describe the characterization of a <it>galU </it>mutant strain of FT live vaccine strain (LVS). We show that the <it>galU </it>mutant was highly attenuated in a murine model of tularemia and elicited more robust innate immune responses than the wild-type (WT) strain. These studies document that the kinetics of chemokine expression and neutrophil recruitment into the lungs of mice challenged with the <it>galU </it>mutant strain are significantly more rapid than observed with WT FT, despite the fact that there were no observed differences in TLR2 or TLR4 signaling or replication/dissemination kinetics during the early stages of infection. We also show that the <it>galU </it>mutant had a hypercytotoxic phenotype and more rapidly induced the production of IL-1β following infection either <it>in vitro </it>or <it>in vivo</it>, indicating that attenuation of the <it>galU </it>mutant strain may be due (in part) to more rapid activation of the inflammasome and/or earlier death of FT infected cells. Furthermore, we show that infection of mice with the <it>galU </it>mutant strain elicits protective immunity to subsequent challenge with WT FT.</p> <p>Conclusions</p> <p>Disruption of the <it>galU </it>gene of FTLVS has little (if any) effect on <it>in vivo </it>infectivity, replication, or dissemination characteristics, but is highly attenuating for virulence. The attenuated phenotype of this mutant strain of FT appears to be related to its increased ability to induce innate inflammatory responsiveness, resulting in more rapid recruitment of neutrophils to the lungs following pneumonic infection, and/or to its ability to kill infected cells in an accelerated fashion. These results have identified two potentially important virulence mechanisms used by FT. These findings could also have implications for design of a live attenuated vaccine strain of FT because sublethal infection of mice with the <it>galU </it>mutant strain of FTLVS promoted development of protective immunity to WT FTLVS.</p

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030

Handbook of Cardiovascular Behavioral Medicine

Handbook of Cardiovascular Behavioral Medicin