Genetic susceptibility to neonatal infection

Effect of TLR-4 gene polymorphisms on sepsis susceptibility in neonates: a systematic review and meta-analysis

Aim: To clarify the role of polymorphisms rs4986790 and rs4986791 in TLR-4 with susceptibility to neonatal sepsis. Methods: To evaluate the possible correlation of polymorphisms rs4986790 and rs4986791 with sepsis risk, odds ratios (ORs) were calculated. The heterogeneity was evaluated by χ²-based Q-test. Results: For rs4986790, ORs were 1.36 (95% CI: 1.05-1.79, p = 0.017) and 1.84 (95% CI: 0.04-7.9, p = 0.410) under AG+GG versus AA and G vs. A models, respectively. For rs4986791, ORs were 2.22 (95% CI: 1.25-3.94, p = 0.006) and 2.20 (95% CI: 1.26-3.85, p = 0.005) under CT+TT versus CC and of T versus C models, respectively. Conclusion: The rs4986790 and rs4986791 polymorphisms in TLR-4 could influence the sepsis susceptibility in neonates.

MBL2 genotypes and their associations with MBL levels and NICU morbidity in a cohort of Greek neonates

The objective of this study was to assess the frequency of MBL2 genotypes and their associations with MBL levels and various morbidities of a neonatal intensive care unit (NICU). One hundred and thirty-four (134) NICU (83 term and 51 preterm) and 150 healthy neonates were enrolled in the study. MBL2 genotype and MBL serum levels at birth were determined prospectively by PCR-RFLP-sequencing and enzyme-linked immunosorbent assay, respectively. NICU neonates displayed significantly lower MBL serum levels compared to healthy ones. MBL deficiency, defined as the low MBL2 expression group (XA/O and O/O), was significantly associated with an increased risk of respiratory morbidity, especially transient tachypnea of the newborn and respiratory distress syndrome (RDS). Moreover, an increase of 100 ng/mL of serum MBL levels decreases by 5% the risk of total respiratory morbidity and by 7% the risk of RDS, after correction for prematurity and sex and regardless of the presence of infections. Our study further supports the notion that neonates with MBL deficiency and low MBL serum levels at birth may be at higher risk of developing severe respiratory complications.

Impact of prematurity on language skills at school age

PURPOSE

The existing literature on language outcomes in children born prematurely focuses almost exclusively on standardized test scores rather than discourse-level abilities. The authors of this study looked longitudinally at school-age language outcomes and potential moderating variables for a group of twins born prematurely versus a control group of twins born at full term, analyzing both standardized test results and language sample data from the population-based Western Reserve Reading Project (WRRP; Petrill, Deater-Deckard, Thompson, DeThorne, & Schatschneider, 2006).

METHOD

Fifty-seven children born prematurely, at ≤32 weeks or <1,500 g, were compared with 57 children born at full term and were matched for age, gender, race, and parental education. Data included discourse-level language samples and standardized test results, collected at average ages 7, 8, and 10 years. The language samples were analyzed to yield a number of semantic and syntactic measures that were consolidated via factor analysis.

RESULTS

Regression models showed significant differences between the 2 groups for standardized test results, although the mean score for both groups fell in the normal range. For the discourse-level language measures, however, differences never reached statistical significance. Parental education was significantly associated with improved standardized test scores.

CONCLUSIONS

These findings suggest that in the absence of frank neurological impairment, sophisticated semantic and syntactic skills may be relatively intact in the discourse-level language of children born prematurely. Implications for assessment, particularly the potential role of attention and executive function in standardized testing tasks, are reviewed.

Genetic and epigenetic susceptibility to early life infection

PURPOSE OF REVIEW

This review aims to interpret the current literature on the role of genetic and epigenetic factors in susceptibility to neonatal infection, a leading cause of early life mortality and morbidity.

RECENT FINDINGS

Epidemiological data indicate that the differential susceptibility to infection is partly heritable. To date there have been relatively few studies on genetic determinants of susceptibility to neonatal infection and many of these have methodological shortcomings. Most studies predominantly focus on the innate immune system. There is growing interest in the potential role of epigenetic mechanisms in disease susceptibility and data are emerging on the role of epigenetics in the maturation of the immune system in early life.

SUMMARY

Infection is a leading cause of morbidity and mortality, especially in preterm infants, but it remains unclear why neonates are so susceptible or what mediates differential risk. Genetic and epigenetic epidemiologic studies may assist in the identification of critical protective and pathogenic pathways. Despite the current relative lack of robust data, such studies may facilitate the development of interventions that ultimately decrease the significant morbidity and mortality of this highly vulnerable population.

The impact of maternal anti-retroviral therapy on cytokine profile in the uninfected neonates

The number of HIV-infected young women has been increasing since the beginning of the AIDS epidemic. The objective of the present study was to investigate the impact of anti-retroviral treatment (ART) of HIV-1-infected pregnant women (PW) on cytokine profile of uninfected neonates. Our results demonstrated that higher levels of IL-1β and TNF-α associated with lower IL-10 production were detected in the plasma obtained from neonates born from ART-treated PW. Furthermore, the production of TNF- α and IFN-γ was also significantly higher in polyclonally-activated T cells from those neonates. This elevated pro-inflammatory pattern detected by these activated-T cells was not associated to HIV-1 antigens sensitization. Finally, ART-exposed neonates showed to be born with lower weight, and it was inversely correlated with maternal peripheral TNF-a level. In summary, the data presented here suggest a significant disturbance in cytokine network of HIV-1-uninfected neonates exposed to potent anti-retroviral schemes during pregnancy.

Genomic Approaches to the Host Response to Pathogens

The need to better understand host–pathogen interactions has risen with the expansion in genomics and related technologies. This chapter focuses on two aspects of the host response to pathogens where major advances are being made using genomic approaches. The availability of complete genomic sequences of an expanding number of pathogens, the human and mouse genome sequences, and the advent of genome-wide genotyping and gene expression profiling has opened up new avenues of investigation in the field. The genotype of the pathogen plays a major role in the response of the host to infection with more virulent pathogenic strains possessing the capability to interfere with the host immune response. In addition, different individuals in a population can have very different responses to a genetically identical pathogen. Part of the differential response is governed by the underlying genetic differences between individuals. The advent of genome-wide genotyping using single nucleotide polymorphisms or microsatellite markers is leading to major advances in molecular epidemiology. The future impact of genomic approaches on the development of diagnostics and therapeutics is discussed for infectious diseases. This includes defining the basis of genetic susceptibility to infection and system-wide molecular response to a pathogen.

[Clinical outcome and bacterial characteristics of 99 Escherichia coli meningitis in young infants]

OBJECTIVE

To conduct a descriptive analysis of clinical, biological and prognostic aspects of Escherichia coli meningitis in young infants.

METHODS

Clinical and biological data on young infants diagnosed with neonatal E. coli meningitis (NECM) between 1988 and 2004 were collected retrospectively and analyzed with respect to the isolates'phenotypic and genotypic characteristics. The molecular analyses focused on the phylogenetic group, the sequence-O-type, and genetic virulence traits. The virulence of lethal strains was tested in a newborn rat meningitis model.

RESULTS

The median age of the 99 children analyzed was 10 days (0 to 90 days), and 83 of the patients were newborns. Thirty-three children were premature. Hyper- or hypothermia was the most frequent clinical sign at admission. Intercurrent urinary tract infection was present in 28% of cases, all over 6 days of age. 81% of blood cultures were positive. The CSF cytology was abnormal in 97% of cases. Twelve hours after admission, 34% of infants were transferred to intensive care. One-third of transfontanellar ultrasound scans done on admission were abnormal. CSH sterilization was slow in 15 % of cases, despite appropriate antibiotic therapy. The use of ciprofloxacin was associated with more rapid CSF sterilization (94 % vs 77 %, p=0.03). Six children relapsed. The average follow-up was eight months, and 21 % of children had sequelae. The case lethality rate was 14%. Fatal outcome was associated with signs of septic shock (57% vs 3%, p<10(-4)) and neurological failure (76% vs 19%, p<10(-4)) within the first 24 hours, and with abnormalities on the first ultrasound scan (63% vs 27%, p=0.03). The risk of death was higher among children infected by strains belonging to unusual sequence-O-types (50% vs 18%, p=0.01), which harbored fewer virulence factors (4.8 vs 5.9, p<10(-4)). Only aerobactin was less frequent in lethal strains (71 % vs 94%, p=0.02). Strains belonging to unusual sequence-O-types and that were lethal in the animal model induced a significantly lower level of bacteremia than strains belonging to frequent sequence-O-types (p<0.001).

CONCLUSION

E. coli meningitis remains highly lethal in infants. Clinical and molecular analyses showed a link between lethality and infrequent sequence-O-types. The avirulence of these strains in animal models suggests that fatal outcome could be due to host susceptibility more than to strain virulence.

Association between mortality of Escherichia coli meningitis in young infants and non-virulent clonal groups of strains

To identify factors associated with Escherichia coli meningitis (ECM) mortality in infants aged <3 months, the clinical, biological and bacterial characteristics of isolates from 99 cases of ECM were compared, including the phylogenetic group, multilocus sequence type, O serogroup and sequence O type (a combination of sequence type complex (STc) and O serogroup) and virulence genotype. All 99 isolates were susceptible to the initial antimicrobial treatment. The mortality rate (14%) was not influenced by term or post-natal age. Hypotension or seizures were the sole clinical predictive factors for fatal outcome (p <0.01), and abnormal initial trans-fontanellar ultrasound was associated with death (p 0.03). Seventy-seven isolates belonged to the common sequence O types (STc29(O1), STc29(O18), STc29(O45), STc301(O7), STc304(O16), STc697(O83), STc700(O1)) causing neonatal meningitis. None of the phylogenetic groups and none of the virulence determinants were distributed differently between survivors and non-survivors, except that the aerobactin gene (iucC) was less frequent in lethal isolates (94% vs. 71%, p 0.02). Isolates belonging to rare sequence O types were more likely to be lethal (OR 4.3, p 0.01), although they induced a lower level of bacteraemia than common sequence O types such as STc29(O18) and STc29(O45) in a neonatal rat model. These results suggest that unidentified human genetic risk-factors may be more important than strain virulence in predicting ECM mortality.

Altered immunological reactivity in HIV-1-exposed uninfected neonates

This work aimed to evaluate immune events in HIV-1-exposed uninfected neonates born from mothers who control (G1) or not (G2) the plasma viral load, using unexposed neonates as controls. Cord blood from each neonate was collected, plasma and mononuclear cells were separated and the lymphoproliferation and cytokine pattern were evaluated. The results demonstrated that the in vitro lymphoproliferation induced by polyclonal activators was higher in the G2 neonates. Nevertheless, no cell culture responded to poll synthetic HIV-1 envelope peptides. The cytokine dosage in the plasma and supernatants of polyclonally-activated cultures demonstrated that, while IL-4 and IL-10 were the dominant cytokines produced in G1 and control groups, IFN-gamma and TNF-alpha were significantly higher in G2 neonates. Systemic levels of IL-10 observed among the G1 neonates were higher in those born from anti-retroviral treated mothers. In summary, our results indicate an altered immune responsiveness in neonates exposed in utero to HIV and support the role of maternal anti-retroviral treatment to attenuate it.

Innate immunity of the newborn: basic mechanisms and clinical correlates

The fetus and newborn face a complex set of immunological demands, including protection against infection, avoidance of harmful inflammatory immune responses that can lead to pre-term delivery, and balancing the transition from a sterile intra-uterine environment to a world that is rich in foreign antigens. These demands shape a distinct neonatal innate immune system that is biased against the production of pro-inflammatory cytokines. This bias renders newborns at risk of infection and impairs responses to many vaccines. This Review describes innate immunity in newborns and discusses how this knowledge might be used to prevent and treat infection in this vulnerable population.