The Role of Alveolar Epithelial Type II-Like Cells in Uptake of Structurally Different Antigens and in Polarisation of Local Immune Responses

Contribution of typhoid toxin in the pathogenesis of Salmonella Typhi

To persist and establish infection, Salmonella utilizes a battery of different virulence determinants at every stage of infection. Typhoid toxin, a newly identified toxin in Salmonella enterica serovar Typhi is recognized as one of the virulence factors that has been linked with Salmonella pathogenesis. In this study, we have further investigated the role of typhoid toxin in the symptomatology of typhoid fever through in-vivo and ex-vivo studies. In mice, administration of cloned and purified typhoid toxin induces similar symptoms observed during typhoid fever such as fever, weight loss with a decrease in peripheral leucocyte count along with an increase in levels of pro-inflammatory cytokines (Il-6, TNF-α). Results of DNA analysis, fluorescence microscopy and flow cytometry of typhoid toxin-treated macrophages (ex-vivo) altogether revealed the CdtB (subunit of typhoid toxin) mediated DNA damage that led to the apoptosis of cells. Furthermore, to validate CdtB's catalytic role, macrophages were treated with typhoid toxin preincubated with anti-CdtB antibodies (generated in mice). Re-assessment of macrophage DNA by gel electrophoresis and flow cytometry analysis indicated a significant decrease in DNA damage and cells undergoing apoptosis, respectively. Moreover, a significant reduction in in-vitro DNase activity of CdtB protein was also observed on preincubating holotoxin with anti-CdtB antibodies. In total, this study highlights the role of typhoid toxin in inducing typhoid fever-like symptomatology, which may be executed through the toxin's catalytic subunit CdtB.

Prophylactic potential of cytolethal distending toxin B (CdtB) subunit of typhoid toxin against Typhoid fever

Typhoid fever caused by Salmonella enterica serovar Typhi (S.Typhi) continues to be a major problem, especially in developing countries. Due to the rapid emergence of multi-drug-resistant (MDR) strains, which limits the efficacy of conventional antibiotics as well as problems associated with the existing vaccines, efforts are being made to develop effective prophylactic agents. CdtB subunit of typhoid toxin was selected for assessing its vaccine potential due to its high conservation throughout the Typhi strains. In-vitro assessment of DNase activity of cloned and purified CdtB protein showed a significant decrease in the band intensity of DNA. The measure of metabolic activity and morphological alterations assessed using different cell lines in the presence of CdtB protein showed no significant signs of toxicity. These observations were further strengthened by cell cycle analysis, assessed by flow cytometry. Keeping these observations in mind, the immunoprotective potential of CdtB was assessed using S.Typhi induced mouse peritonitis model. A significant titer of IgG antibodies (>128000) against CdtB protein was recorded in the immunized mice by enzyme-linked immunosorbent assay (ELISA), which was also validated by immunoblotting. Active immunization with the protein protected 75% mice against a lethal dose of S.Typhi Ty2. The data indicated a significant (up to 5 log) reduction in the bacterial load in the spleen and liver of immunized-infected mice compared to control (unimmunized-infected) mice which might have resulted in the modulation of histoarchitecture of spleen and liver and the levels of cytokines (IL-6, TNF-α and IL-10) production; thereby indicating the effectiveness of the subunit. The observations deduced from the study give the proof of concept of immunogenic potential of protein. However, further studies involving the immunoreactivity of CdtB with the statistically significant number of sera samples obtained from the human patients would be helpful in establishing the relevance of CdtB protein in humans and for making the strategies to develop it as an effective vaccine candidate.

In Utero Exposure to Aspirin and Risk of Asthma in Childhood

BACKGROUND

Aspirin is widely used in general population and low-dose aspirin is commonly prescribed to prevent recurrent pregnancy loss associated with antiphospholipid syndrome and preeclampsia, often used throughout pregnancy. But aspirin is associated with asthma pathogenesis. We aim to examine whether in utero exposure to aspirin at different fetal stages is associated with asthma in childhood.

METHODS

We used data from the Collaborative Perinatal Project. Maternal exposure to aspirin before and during pregnancy was recorded at each prenatal visit. Children were followed up to 7 years of age. A total of 19,928 singleton children without maternal history of asthma were included. We used multilevel multiple logistic regression models to control for potential confounders.

RESULTS

In utero exposure to aspirin was associated with an increased risk of childhood asthma (adjusted odds ratio [aORs] = 1.3, 95% confidence interval [CI] = 1.1, 1.6). aORs for exposure in first, second, and third trimesters were 1.1 (95% CI = 0.87, 1.3), 1.2 (95% CI = 1.0, 1.4), and 1.4 (95% CI = 1.1, 1.6), respectively. Furthermore, aORs of asthma were 1.3 (95% CI = 1.0, 1.7) and 1.3 (95% CI = 1.0, 1.7) for aspirin use for 2 to 7 days or more than 7 days in third trimester, respectively.

CONCLUSION

In utero exposure to therapeutic dose of aspirin even just briefly in late pregnancy is associated with childhood asthma by 7 years of age. More research is needed to carefully examine the association between low-dose aspirin with extended exposure period and long-term child outcomes.

Murine models for mucosal tolerance in allergy

Immunity is established by a fine balance to discriminate between self and non-self. In addition, mucosal surfaces have the unique ability to establish and maintain a state of tolerance also against non-self constituents such as those represented by the large numbers of commensals populating mucosal surfaces and food-derived or air-borne antigens. Recent years have seen a dramatic expansion in our understanding of the basic mechanisms and the involved cellular and molecular players orchestrating mucosal tolerance. As a direct outgrowth, promising prophylactic and therapeutic models for mucosal tolerance induction against usually innocuous antigens (derived from food and aeroallergen sources) have been developed. A major theme in the past years was the introduction of improved formulations and novel adjuvants into such allergy vaccines. This review article describes basic mechanisms of mucosal tolerance induction and contrasts the peculiarities but also the interdependence of the gut and respiratory tract associated lymphoid tissues in that context. Particular emphasis is put on delineating the current prophylactic and therapeutic strategies to study and improve mucosal tolerance induction in allergy.