Environmental toxins as modulators of antiviral immune responses

Environmental contaminant mixtures modulate in vitro influenza infection

Environmental chemicals, particularly organochlorinated contaminants (OCs), are associated with a ranged of adverse health effects, including impairment of the immune system and antiviral immunity. Influenza A virus (IAV) is an infectious disease of major global public health concern and exposure to OCs can increase the susceptibility, morbidity, and mortality to disease. It is however unclear how pollutants are interacting and affecting the outcome of viral infections at the cellular level. In this study, we investigated the effects of a mixture of environmentally relevant OCs on IAV infectivity upon in vitro exposure in Madin Darby Canine Kidney (MDCK) cells and human lung epithelial cells (A549). Exposure to OCs reduced IAV infectivity in MDCK and A549 cells during both short (18-24h) and long-term (72h) infections at 0.05 and 0.5ppm, and effects were more pronounced in cells co-treated with OCs and IAV than pre-treated with OCs prior to IAV (p<0.001). Pre-treatment of host cells with OCs did not affect IAV cell surface attachment or entry. Visualization of IAV by transmission electron microscopy revealed increased envelope deformations and fewer intact virions during OC exposure. Taken together, our results suggest that disruption of IAV infection upon in vitro exposure to OCs was not due to host-cell effects influencing viral attachment and entry, but perhaps mediated by direct effects on viral particles or cellular processes involved in host-virus interactions. In vitro infectivity studies such as ours can shed light on the complex processes underlying host-pathogen-pollutant interactions.

Prenatal exposure to bisphenol-A is associated with Toll-like receptor-induced cytokine suppression in neonates

BACKGROUND

Despite widespread human exposure to biphenol A (BPA), limited studies exist on the association of BPA with adverse health outcomes in young children. This study aims to investigate the effect of prenatal exposure to BPA on toll-like receptor-induced cytokine responses in neonates and its association with infectious diseases later in life.

METHODS

Cord bloods were collected from 275 full-term neonates. Production of TNF-α, IL-6, and IL-10 were evaluated after stimulating mononuclear cells with toll-like receptor ligands (TLR1-4 and 7-8). Serum BPA concentrations were analyzed by enzyme-linked immunosorbent assay. Bacteria from nasopharyngeal specimens were identified with multiplex PCR and culture method.

RESULT

Result showed significant association between cord BPA concentration and TLR3- and TLR4-stimulated TNF-α response (P = 0.001) and that of TLR78-stimulated IL-6 response (P = 0.03). Clinical analysis did not show prenatal BPA exposure to be correlated with infection or bacterial colonization during the first year of life.

CONCLUSION

This is the first cohort study that indicated prenatal BPA exposure to play a part in TLR-related innate immune response of neonatal infants. However, despite an altered immune homeostasis, result did not show such exposure to be associated with increased risk of infection during early infancy.

Perinatal exposure to a low dose of bisphenol A impaired systemic cellular immune response and predisposes young rats to intestinal parasitic infection

Perinatal exposure to the food contaminant bisphenol A (BPA) in rats induces long lasting adverse effects on intestinal immune homeostasis. This study was aimed at examining the immune response to dietary antigens and the clearance of parasites in young rats at the end of perinatal exposure to a low dose of BPA. Female rats were fed with BPA [5 µg/kg of body weight/day] or vehicle from gestational day 15 to pup weaning. Juvenile female offspring (day (D)25) were used to analyze immune cell populations, humoral and cellular responses after oral tolerance or immunization protocol to ovalbumin (OVA), and susceptibility to infection by the intestinal nematode Nippostrongylus brasiliensis (N. brasiliensis). Anti-OVA IgG titers following either oral tolerance or immunization were not affected after BPA perinatal exposure, while a sharp decrease in OVA-induced IFNγ secretion occurred in spleen and mesenteric lymph nodes (MLN) of OVA-immunized rats. These results are consistent with a decreased number of helper T cells, regulatory T cells and dendritic cells in spleen and MLN of BPA-exposed rats. The lack of cellular response to antigens questioned the ability of BPA-exposed rats to clear intestinal infections. A 1.5-fold increase in N. brasiliensis living larvae was observed in the intestine of BPA-exposed rats compared to controls due to an inappropriate Th1/Th2 cytokine production in infected jejunal tissues. These results show that perinatal BPA exposure impairs cellular response to food antigens, and increases susceptibility to intestinal parasitic infection in the juveniles. This emphasized the maturing immune system during perinatal period highly sensitive to low dose exposure to BPA, altering innate and adaptative immune response capacities in early life.

Developmental exposure to bisphenol A modulates innate but not adaptive immune responses to influenza A virus infection

Bisphenol A (BPA) is used in numerous products, such as plastic bottles and food containers, from which it frequently leaches out and is consumed by humans. There is a growing public concern that BPA exposure may pose a significant threat to human health. Moreover, due to the widespread and constant nature of BPA exposure, not only adults but fetuses and neonates are also exposed to BPA. There is mounting evidence that developmental exposures to chemicals from our environment, including BPA, contribute to diseases late in life; yet, studies of how early life exposures specifically alter the immune system are limited. Herein we report an examination of how maternal exposure to a low, environmentally relevant dose of BPA affects the immune response to infection with influenza A virus. We exposed female mice during pregnancy and through lactation to the oral reference dose for BPA listed by the US Environmental Protection Agency, and comprehensively examined immune parameters directly linked to disease outcomes in adult offspring following infection with influenza A virus. We found that developmental exposure to BPA did not compromise disease-specific adaptive immunity against virus infection, or reduce the host's ability to clear the virus from the infected lung. However, maternal exposure to BPA transiently reduced the extent of infection-associated pulmonary inflammation and anti-viral gene expression in lung tissue. From these observations, we conclude that maternal exposure to BPA slightly modulates innate immunity in adult offspring, but does not impair the anti-viral adaptive immune response, which is critical for virus clearance and survival following influenza virus infection.

Low-dose arsenic compromises the immune response to influenza A infection in vivo

BACKGROUND

Arsenic exposure is a significant worldwide environmental health concern. We recently reported that 5-week exposure to environmentally relevant levels (10 and 100 ppb) of As in drinking water significantly altered components of the innate immune response in mouse lung, which we hypothesize is an important contributor to the increased risk of lung disease in exposed human populations.

OBJECTIVES

We investigated the effects of As exposure on respiratory influenza A (H1N1) virus infection, a common and potentially fatal disease.

METHODS

In this study, we exposed C57BL/6J mice to 100 ppb As in drinking water for 5 weeks, followed by intranasal inoculation with a sub lethal dose of influenza A/PuertoRico/8/34 (H1N1) virus. Multiple end points were assessed postinfection.

RESULTS

Arsenic was associated with a number of significant changes in response to influenza, including an increase in morbidity and higher pulmonary influenza virus titers on day 7 post-infection. We also found many alterations in the immune response relative to As-unexposed controls, including a decrease in the number of dendritic cells in the mediastinal lymph nodes early in the course of infection.

CONCLUSIONS

Our data indicate that chronic As exposure significantly compromises the immune response to infection. Alterations in response to repeated lung infection may also contribute to other chronic illnesses, such as bronchiectasis, which is elevated by As exposure in epidemiology studies.