Detection of specific antibodies in cord blood, infant and maternal saliva and breast milk to staphylococcal toxins implicated in sudden infant death syndrome (SIDS)

Antigen-specific downregulation of miR-150 in CD4 T cells promotes cell survival

MicroRNA-150 (miR-150) has been shown to play a general role in the immune system, but very little is known about its role on CD4+ T cell responses. During T cell responses against superantigen Staphylococcal Enterotoxin A, miR-150 expression was down-regulated in antigen-specific CD4+ T cells but up-regulated in CD8+ T cells. CD4+ and CD8+ T cell clonal expansion was greater in miR-150-KO mice than in WT mice, but miR-150 selectively repressed IL-2 production in CD4+ T cells. Transcriptome analysis of CD4+ T cells demonstrated that apoptosis and mTOR pathways were highly enriched in the absence of miR-150. Mechanistic studies confirmed that miR-150 promoted apoptosis specifically in antigen-specific CD4+ T cells, but not in bystander CD4+ nor in CD8+ T cells. Furthermore, inhibition of mTOR-linked mitochondrial superoxidedismutase-2 increased apoptosis in miR-150-/- antigen-specific CD4+ T. Thus, miR-150 impacts CD4+ T cell helper activity by attenuating IL-2 production along with clonal expansion, and suppresses superoxidedismutase to promote apoptosis.

Limited Neonatal Carbohydrate-Specific Antibody Repertoire Consecutive to Partial Prenatal Transfer of Maternal Antibodies

Despite the prominence of carbohydrate-specific antibodies in human sera, data on their emergence and antigen specificities are limited. Whereas maternal IgG are transferred prenatally to the fetal circulation, IgM present in cord blood originate from fetal B lymphocytes. Considering the limited exposure of the fetus to foreign antigens, we assessed the repertoire of carbohydrate-specific antibodies in human cord blood and matched maternal blood samples using glycan arrays. Carbohydrate-specific IgM was absent in cord blood, whereas low cord blood IgG reactivity to glycans was detectable. Comparing IgG reactivities of matched pairs, we observed a general lack of correlation in the antigen specificity of IgG from cord blood and maternal blood due to a selective exclusion of most carbohydrate-specific IgG from maternofetal transfer. Given the importance of intestinal bacteria in inducing carbohydrate-specific antibodies, we analyzed global antibody specificities toward commensal bacteria. Similar IgG reactivities to specific Bacteroides species were detected in matched cord and maternal blood samples, thus pointing to an efficient maternal transfer of anti-microbial IgG. Due to the observed selectivity in maternofetal IgG transfer, the lack of fetal antibodies to carbohydrate epitopes is only partially compensated by maternal IgG, thus resulting in a weak response to carbohydrate antigens in neonates.

Optimise the microbial flora with milk and yoghurt to prevent disease

Pathogenic bacteria, which are temporary or permanent members of our microbial flora, cause or contribute to a wide range of human disease at all ages. Conditions include Alzheimer's disease, atherosclerosis, diabetes mellitus, obesity, cancer, autoimmunity and psychosis, amongst others. The mechanism of damage is inflammation which can be chronic or acute. An optimal microbial flora includes a wide range of pathogenic bacteria in low dose. This allows specific immunity to be developed and maintained with minimal inflammatory damage. Human milk has evolved to deliver an optimal microbial flora to the infant. Cow's milk has the potential, following appropriate fortification, to maintain an optimal human microbial flora throughout life. Yoghurt is a fermented milk product in which bacteria normally present in milk convert sugars to lactic acid. The acid suppresses the growth of pathogens in the oral cavity, oropharynx and oesophagus. Thus yoghurt can restore an optimal flora in these regions in the short term. Since bacteria are transported between epithelial surfaces, yoghurt will also optimise the flora elsewhere. The judicious use of milk and yogurt could prevent a high proportion of human disease.

Prevalence of enterotoxin genes in Staphylococcus aureus colonising food handlers: does nasal carriage status matter?

This study investigated the association between the presence of staphylococcal enterotoxin (SE) genes and nasal carriage status, and determined temporal changes in the prevalence of these genes in Staphylococcus aureus strains isolated from healthy carriers between 2002 and 2011. Three large samples of food handlers recruited in 2002, 2003 and 2011 were nasally sampled on two occasions to determine S. aureus colonisation status. Those carrying the same spa type on both occasions were defined as persistent carriers. Genes for SEs SEA-SEU were amplified and associations between carriage status and presence of SE genes were investigated. Although 80 % of nasal isolates harboured at least one SE gene over the sampling period, persistent carriers were significantly more likely to harbour enterotoxigenic S. aureus than transiently colonised subjects [odds ratio (OR) 2.52-3.06]. Strains from persistent carriers more commonly harboured sea, seb and sem. The prevalence of classical SE genes and sej, sem, sen, seo, seq and ses was stable over time, but seh, sel, sep, ser, set and selu increased significantly. Increased toxigenicity of isolates from persistent carriers is consistent with the elevated antibody levels to classical SEs previously reported in persistent carriers, supporting the hypothesis that superantigen production in the nasal cavity may enhance colonisation.

Detection and potential utility of C-reactive protein in saliva of neonates

OBJECTIVE

We aimed to detect C-reactive protein (CRP) in neonatal saliva and evaluate its diagnostic utility.

STUDY DESIGN

Salivary and serum samples (n = 89) were collected from 40 neonates. Salivary CRP levels were determined using an enzyme-linked immunosorbent assay; serum CRP was measured per hospital protocol. Correlation coefficients with 95% confidence intervals and robust linear regression measured association while receiver-operator characteristic curves described the accuracy of salivary CRP in discriminating abnormal serum CRP thresholds of ≥10 and 5 mg/L. Corresponding sensitivities and specificities were calculated for these salivary cutpoints.

RESULTS

The area under the curve for salivary CRP in predicting serum CRP levels of ≥10 and 5 mg/L were 0.81 and 0.76, respectively. The corresponding sensitivity and specificity for raw salivary CRP to discriminate a serum CRP of ≥5 mg/L was 0.54 and 0.95, respectively. The corresponding sensitivity and specificity for raw salivary CRP to discriminate a serum CRP of ≥10 mg/L was 0.64 and 0.94, respectively. A statistically significant correlation was observed between serum and salivary CRP (r = 0.62, p < 0.001).

CONCLUSION

C-reactive protein is detectable in neonatal saliva and can predict abnormal serum CRP thresholds. Salivary CRP analysis represents a feasible screening tool for detecting abnormal serum CRP levels.

Season is associated with Pseudomonas aeruginosa acquisition in young children with cystic fibrosis

Pseudomonas aeruginosa, the principal respiratory pathogen in cystic fibrosis (CF) patients, is ubiquitous in the environment. Initial P. aeruginosa isolates in CF patients are generally environmental in nature. However, little information regarding seasonality of P. aeruginosa acquisition is available. We conducted a retrospective study to evaluate the seasonality of initial P. aeruginosa acquisition in young children with CF in the USA using the Cystic Fibrosis Foundation National Patient Registry from 2003 to 2009. Additionally, we assessed whether seasonal acquisition varied by climate zone. A total of 4123 children met inclusion criteria and 45% (n = 1866) acquired P. aeruginosa during a mean 2.0 years (SD 0.2 years) of follow up. Compared with winter, increased P. aeruginosa acquisition was observed in summer (incidence rate ratio (IRR): 1.22; 95% CI: 1.07-1.40) and autumn (IRR: 1.34; 95% CI: 1.18-1.52), with lower acquisition observed in spring (IRR: 0.81; 95% CI: 0.70-0.94). Seasonal variations in P. aeruginosa acquisition rates in the temperate and continental climate zones were similar to those in the overall cohort. In contrast, no significant seasonal effect was observed in the dry climate zone. In a corresponding analysis, no seasonal difference was observed in the rate of acquisition of Staphylococcus aureus, another common CF respiratory pathogen. These results provide preliminary support that climatic factors may be associated with initial P. aeruginosa acquisition in CF patients. Investigation and identification of specific risk factors, as well as awareness of seasonal variation, could potentially inform clinical recommendations including increased awareness of infection control and prevention strategies.

The male excess in sudden infant deaths

The peak age at which sudden infant death syndrome (SIDS) occurs corresponds to the developmental period in which infants are dependent on their innate responses to infection. There is a growing body of evidence indicating that dysregulation of inflammatory responses might contribute to the physiological changes leading to these sudden deaths. This study examined the effects of three important risk factors for SIDS on inflammatory responses: cigarette smoke, virus infection and male sex. Cytokine responses of peripheral monocytic blood cells of healthy, non-smoking males and females to endotoxin were measured. Surrogates for virus infection or cigarette smoke were assessed using IFN-γ or water-soluble cigarette smoke extract (CSE). For most conditions, cells from males had lower pro-inflammatory cytokine responses than those of females. An opposite trend was observed for IL-10. Significantly lower levels of some cytokines were noted for cells from male donors exposed to CSE. In females, there were significant correlations between testosterone levels and levels of pro-inflammatory cytokines, but none for males. Testosterone levels in females correspond to those among male infants in the age range at greatest risk of SIDS. The effects of the testosterone surge in male infants need to be examined in relation to changes in cortisol levels that occur during the same period of infant development.

Simultaneous detection of seven staphylococcal enterotoxins: development of hydrogel biochips for analytical and practical application

A method of simultaneous analysis of staphylococcal enterotoxins using hydrogel-based microarrays (biochips) has been developed. The method allows simultaneous quantitative detection of seven enterotoxins: A, B, C1, D, E, G, and I in a single sample. The development of the method included expression and purification of recombinant toxins, production of panels of monoclonal antibodies (mAbs) against the toxins, and design and manufacturing of an experimental biochip for the screening of mAbs and selection of optimal pairs of primary and secondary antibodies for each toxin. The selected mAbs have high affinity toward their targets and no cross-reactivity with unrelated enterotoxins. Finally, a diagnostic biochip was designed for quantitative analysis of the toxins, and the analytical protocols were optimized. The sensitivity of the detection reached 0.1-0.5 ng/mL, depending on the type of enterotoxin. The evaluation of the resulting biochip using spiked food samples demonstrated that the sensitivity, specificity, and reproducibility of the proposed test system fully satisfy the requirements for traditional immunoanalytical systems. The diagnostic biochips manufactured on reflecting metal-coated surfaces shortened the time of analysis from 17 to 2 h without loss of sensitivity. The method was successfully tested on samples of food and biological media.

Toxic shock syndrome in a neonate

We report an unusual case of toxic shock syndrome in a 4-day-old baby, with mucosal isolates of Staphylococcus aureus (SEC, G, and I) and group G streptococcus. Treatment involved intravenous immunoglobulin and antibiotics. This case highlights the difficulties associated with the diagnosis and treatment of this condition in neonates.

Sudden infant death syndrome, infection and inflammatory responses

Sudden infant death syndrome (SIDS) is sudden unexpected death in infancy for which there is no explanation after review of the history, a death scene investigation and a thorough autopsy. The use of common diagnostic criteria is a prerequisite for discussing the importance of infection, inflammatory responses and trigger mechanism in SIDS. Several observations of immune stimulation in the periphery and of interleukin-6 elevation in the cerebrospinal fluid of SIDS victims explain how infections can play a role in precipitating these deaths. Finally, these findings and important risk factors for SIDS are integrated in the concept of a vicious circle for understanding the death mechanism. The vicious circle is a concept to elucidate the interactions between unfavourable factors, including deficient auto-resuscitation, and how this could result in death.

Development of mucosal immunity in the first year of life and relationship to sudden infant death syndrome

The common mucosal immune system (CMIS) is an interconnecting network of immune structures that provides effective immunity to mucosal surfaces. The structures of the mucosal immune system are fully developed in utero by 28 weeks gestation, but in the absence of intrauterine infection, activation does not occur until after birth. Mucosal immune responses occur rapidly in the first weeks of life in response to extensive antigenic exposure. Maturation of the mucosal immune system and establishment of protective immunity varies between individuals but is usually fully developed in the first year of life, irrespective of gestational age at birth. In addition to exposure to pathogenic and commensal bacteria, the major modifier of the developmental patterns in the neonatal period is infant feeding practices. A period of heightened immune responses occurs during the maturation process, particularly between 1 and 6 months, which coincides with the age range during which most cases of sudden infant death syndrome (SIDS) occur. A hyper-immune mucosal response has been a common finding in infants whose death is classified as SIDS, particularly if in association with a prior upper respiratory infection. Inappropriate mucosal immune responses to an otherwise innocuous common antigen and the resulting inflammatory processes have been proposed as factors contributing to SIDS.