Central Role of the Holliday Junction Helicase RuvAB in vlsE Recombination and Infectivity of Borrelia burgdorferi

Antigenic variation plays a vital role in the pathogenesis of many infectious bacteria and protozoa including Borrelia burgdorferi, the causative agent of Lyme disease. VlsE, a 35 kDa surface-exposed lipoprotein, undergoes antigenic variation during B. burgdorferi infection of mammalian hosts, and is believed to be a critical mechanism by which the spirochetes evade immune clearance. Random, segmental recombination between the expressed vlsE gene and adjacent vls silent cassettes generates a large number of different VlsE variants within the infected host. Although the occurrence and importance of vlsE sequence variation is well established, little is known about the biological mechanism of vlsE recombination. To identify factors important in antigenic variation and vlsE recombination, we screened transposon mutants of genes known to be involved in DNA recombination and repair for their effects on infectivity and vlsE recombination. Several mutants, including those in BB0023 (ruvA), BB0022 (ruvB), BB0797 (mutS), and BB0098 (mutS-II), showed reduced infectivity in immunocompetent C3H/HeN mice. Mutants in ruvA and ruvB exhibited greatly reduced rates of vlsE recombination in C3H/HeN mice, as determined by restriction fragment polymorphism (RFLP) screening and DNA sequence analysis. In severe combined immunodeficiency (C3H/scid) mice, the ruvA mutant retained full infectivity; however, all recovered clones retained the ‘parental’ vlsE sequence, consistent with low rates of vlsE recombination. These results suggest that the reduced infectivity of ruvA and ruvB mutants is the result of ineffective vlsE recombination and underscores the important role that vlsE recombination plays in immune evasion. Based on functional studies in other organisms, the RuvAB complex of B. burgdorferi may promote branch migration of Holliday junctions during vlsE recombination. Our findings are consistent with those in the accompanying article by Dresser et al., and together these studies provide the first examples of trans-acting factors involved in vlsE recombination

Elevations of inflammatory proteins in neonatal blood are associated with obesity and overweight among 2-year-old children born extremely premature

BACKGROUND: Childhood obesity is associated with elevated blood concentrations of inflammation markers. It is not known to what extent inflammation precedes the development of obesity. METHODS: In a cohort of 882 infants born before 28 weeks of gestation, we examined relationships between concentrations of 25 inflammation-related proteins in blood obtained during the first two postnatal weeks and body mass index at 2 years of age. RESULTS: Among children delivered for spontaneous indications (n=734), obesity was associated with elevated concentrations of four proteins (IL-1β, IL-6, TNF-R1, and MCP-1) on the first postnatal day; one protein (IL-6) on postnatal day 7; and two proteins (ICAM-3 and VEGF-R1) on postnatal day 14. Among children delivered for maternal or fetal indications (n=148), obesity was associated with elevated concentrations of seven proteins on the 14th postnatal day. In multivariable models in the spontaneous indications subsample, elevated IL-6 on day 1 predicted obesity (odds ratio: 2.9; 95% confidence limits: 1.2, 6.8), while elevated VCAM-1 on day 14 predicted overweight at 2 years of age (odds ratio: 2.3; 95% confidence limits: 1.2, 4.3). CONCLUSIONS: In this cohort, neonatal systemic inflammation preceded the onset of obesity, suggesting that inflammation might contribute to the development of obesity.Pediatric Research accepted article preview online, 15 December 2017. doi:10.1038/pr.2017.313

Both antenatal and postnatal inflammation contribute information about the risk of brain damage in extremely preterm newborns

Background: Preterm newborns exposed to intrauterine inflammation are at increased risk of neurodevelopmental disorders. We hypothesized that adverse outcomes are more strongly associated with a combination of antenatal and postnatal inflammation than with either of them alone. Methods: We defined antenatal inflammation as histologic inflammation in the placenta. We measured the concentrations of seven inflammation-related proteins in blood obtained on postnatal days 1, 7, and 14 from 763 infants born before 28 weeks of gestation. We defined postnatal inflammation as a protein concentration in the highest quartile on at least 2 days. We used logistic regression models to evaluate the contribution of antenatal and postnatal inflammation to the risk of neurodevelopmental disorders. Results: The risk of white matter damage was increased when placental inflammation was followed by sustained elevation of CRP or ICAM-1. We found the same for spastic cerebral palsy when placental inflammation was followed by elevation of TNF-α or IL-8. The presence of both placental inflammation and elevated levels of IL-6, TNF-α, or ICAM-1 was associated with an increased risk for microcephaly. Conclusion: Compared to a single hit, two inflammatory hits are associated with stronger risk for abnormal cranial ultrasound, spastic cerebral palsy, and microcephaly at 2 years

Early postnatal hypotension is not associated with indicators of white matter damage or cerebral palsy in extremely low gestational age newborns

OBJECTIVES: To evaluate, in extremely low gestational age newborns (ELGANs), relationships between indicators of early postnatal hypotension and cranial ultrasound indicators of cerebral white matter damage imaged in the nursery and cerebral palsy diagnoses at 24 month follow-up. METHODS: The 1041 infants in this prospective study were born at < 28 weeks gestation, were assessed for 3 indicators of hypotension in the first 24 postnatal hours, had at least one set of protocol cranial ultrasound scans, and were evaluated with a structured neurologic exam at 24 months corrected age. Indicators of hypotension included: 1) lowest mean arterial pressure (MAP) in the lowest quartile for gestational age; 2) treatment with a vasopressor; and 3) blood pressure lability, defined as the upper quartile of the difference between each infant’s lowest and highest MAP. Outcomes included indicators of cerebral white matter damage, i.e. moderate/severe ventriculomegaly or an echolucent lesion on cranial ultrasound, and cerebral palsy diagnoses at 24 months gestation. Logistic regression was used to evaluate relationships among hypotension indicators and outcomes, adjusting for potential confounders. RESULTS: Twenty-one percent of surviving infants had a lowest blood pressure in the lowest quartile for gestational age, 24% were treated with vasopressors, and 24% had labile blood pressure. Among infants with these hypotension indicators, 10% percent developed ventriculomegaly and 7% developed an echolucent lesion. At 24-months follow-up, 6% had developed quadriparesis, 4% diparesis, and 2% hemiparesis. After adjusting for confounders, we found no association between indicators of hypotension, and indicators of cerebral white matter damage or a cerebral palsy diagnosis. CONCLUSIONS: The absence of an association between indicators of hypotension and cerebral white matter damage and or cerebral palsy suggests that early hypotension may not be important in the pathogenesis of brain injury in ELGANs