Neonatal exposure to estradiol induces resistance to helminth infection and changes in the expression of sex steroid hormone receptors in the brain and spleen in adult mice of both sexes

Evaluating suitability of saliva to measure steroid concentrations in grey seal pups

Measurement of steroids in wild pinnipeds can facilitate assessment of breeding, nutritional and stress status, and is useful in understanding behavioral responses. Even in young animals, sex steroids may be important in behavioral interactions and immune modulation. Use of saliva can avoid the large fluctuations seen in some steroids in plasma, and can negate the need for venipuncture, making it a potentially useful matrix in the wildlife. However, its utility in estimating steroid levels in wild young pinnipeds has not been evaluated. Here, we investigated the suitability of saliva for steroid hormone analysis in wild grey seal pups during their suckling and post-weaning fast periods. We collected saliva (n = 38) and plasma (n = 71) samples during the breeding season on the Isle of May, Scotland, 2012. We investigated success of sample collection, ease of preparation, accuracy and precision of analysis, and, where possible, comparability of measurements (n = 27) from saliva and plasma. Plasma sampling was rapid, whereas sampling saliva took up to five times longer. Analytical performance criteria (parallelism, accuracy, and precision (intra and inter assay co-efficient of variation (% CV)) of commercial ELISA kits to measure estradiol, testosterone and cortisol in both matrices were assessed. Estradiol and cortisol assays performed well and can be used in plasma and saliva. However, we could not confidently validate testosterone for either matrix. Saliva estradiol correlated with levels in plasma. Saliva sample preparation was faster and simpler than plasma preparation because it did not require extraction. However, given the additional time taken to obtain saliva in the wild, the possibility of blood contamination from oral damage and the lower success rate in obtaining sufficient sample for analysis, we recommend that this matrix only be used as an alternative to plasma sampling measurement in pinnipeds when animals are anaesthetized, tolerate mouth swabbing, or have been trained to accept saliva sampling in captivity.

Bisphenol A induces protection through modulation of the immune response against the helminth parasite Taenia crassiceps

AIMS

Industrial growth has increased the exposure to endocrine disruptor compounds (EDCs) in all organisms. Bisphenol A (BPA), an EDC, has been demonstrated to be involved in the susceptibility to parasite infections. However, few studies have analysed this connection in more depth. The aim of this study was to determine whether early BPA exposure in female mice affects the systemic immune response and the susceptibility to Taenia crassiceps infection.

METHODS AND RESULTS

BALB/c mice were exposed to BPA at post-natal day 3. At 6 weeks of age, they were inoculated with T crassiceps larvae and, 2 weeks later, were euthanized. The number of parasites was quantified. By flow cytometry, in the spleen, the peripheral and mesenteric lymph nodes, the different innate and adaptive immune cell modulation was analysed, and RT-PCR cytokine expression was also evaluated. BPA induced a reduction of 40% in parasite load. BPA treatment modulated some lineages of the innate immune response and caused slight changes in cells belonging to the adaptive immune response. Additionally, BPA enhanced the type 2 cytokine profile.

CONCLUSION

Neonatal BPA treatment in female mice affects not only the percentage of different immune cells but also their ex vivo cytokine gene expression, decreasing T crassiceps cysticercosis susceptibility.

Perinatal exposure to bisphenol A increases in the adulthood of the offspring the susceptibility to the human parasite Toxocara canis

Bisphenol A, a very widespread environmental pollutant and endocrine disruptor compound, can interact with several steroid receptors, particularly with estrogen ones. In different studies, it has observed that the endocrine disruption during critical periods of development can trigger alterations in the immune response during the adult life. Male Wistar rats were exposed indirectly to BPA at a dose of 250 μg/kg day during the perinatal period (from day 5 of pregnancy until day 21 postnatal), At the 60 days of age, the adulthood, animals were infected with larvated eggs of the Toxocara canis, and were sacrificed at 7 days post-infection. Parasitic loads in the lung and in the liver were analyzed by artificial digestion. Furthermore, immune cell subpopulations (macrophages, NK cells, Tγδ, total T cells, T helper, T cytotoxic, and B lymphocytes) present in spleen, peripheral and mesenteric lymph nodes were analyzed by flow cytometry. The expression of Th1 and Th2 cytokines at the splenic level was determined by real-time quantitative PCR. Finally, the titers of specific antibodies against to the parasite were analyzed by ELISA. The BPA treatment administrated in the perinatally stage favors a significant increase of the percentage of Toxocara canis larvae in the lungs and liver in the adulthood. Additionally, the exposure to this compound caused a dramatically decrease in the production of specific antibodies against to this parasite, downregulating together Th2 cytokines (IL-4, IL-5 and IL-13), meanwhile upregulated Th1 cytokines (IFN-γ and TNF-α). Perinatal exposure to BPA affects the performance of the immune response during adult life, modifying both cytokines and antibodies production by these cells, which favors the susceptibility to infections, specifically toxocariosis.

Parasite evolution in response to sex-based host heterogeneity in resistance and tolerance

Heterogenity between sexes in terms of both the level and the type of immune response to infection is documented in many species, but its role on parasite evolution is only beginning to be explored. We adopt an evolutionary epidemiology approach to study how the ability of a host to respond to infection through active immunity (resistance) or through minimizing deleterious effects of a given parasite load (tolerance) affects the evolution of parasite virulence. Consistently with earlier models, we find that increases in host resistance and tolerance both favour more virulent parasite strains. However, we show that qualitatively different results can be obtained if dimorphism between the sexes occurs through resistance or through tolerance depending on the contact pattern between the sexes. Finally, we find that variations in host sex ratio can amplify the consequences of heterogeneity for parasite evolution. These results are analysed in the light of several examples from the literature to illustrate the prevalence of sexually dimorphic immune responses and the potential for further study of the role of sexual dimorphism on parasite evolution. Such studies are likely to be highly relevant for improving treatment of chronic infections and control of infectious diseases, and understanding the role of sex in immune function.

Diethylstilbestrol exposure in neonatal mice induces changes in the adulthood in the immune response to taenia crassiceps without modifications of parasite loads

Industrial growth has increased the exposition to endocrine disruptor compounds (EDC's), which are exogenous agents with agonist or antagonist action of endogenous steroid hormones that may affect the course of parasite infections. We wanted to determine if the exposure to diethylstilbestrol (DES), an estrogen agonist, to both male and female mice affected the immune response and their susceptibility to T. crassiceps cysticercosis. In all infected groups, females showed higher parasite loads than males, and neonatal DES administration did not modify this pattern. In the spleen, noninfected mice showed sex-related differences in the percentage of the CD8+ subpopulation, but DES decreased the percentage of CD3+, CD19+, and CD8+ subpopulations in infected mice. In the mesenteric lymphatic node (MNL), DES showed a dimorphic effect in the percentage of CD19+ cells. Regarding estrogen receptor alpha (ER-α) expression, DES treatment induced a reduction in the expression of this receptor in both noninfected female and male mice in the spleen, which was decreased only in males in CD3+ and CD8+ lymphocytes in MNL cell subpopulations. Our study is the first one to demonstrate that DES neonatal treatment in male and female mice affects the immune cell percentage, without effect on the susceptibility to T. crassiceps cysticercosis.

Gender specific differences in the immune response to infection

There are many instances where males and females differ in the susceptibility to infections. The reason for these differences in susceptibility is multifactorial. The primary cause is thought to be due to differences induced by sex hormones and their effects on gene expression as well as the immune system, but may also be due to innate physiological differences between males and females. This review summarizes gender specific differences seen in infections caused by bacteria, fungi, parasites and viruses. Ultimately, gender specific differences appear to be dependent on the microbe causing the infection, as not every infection with a specific microbial type results in increased susceptibility of one gender over the other. This suggests that there is an interaction between gender specific immune differences and the specific immune response to individual microbes.