Hormonal and immunological mechanisms mediating sex differences in parasite infection

The effect of host age on feeding performance of fleas

We asked whether the age of a rodent host affects the feeding performance of fleas. We predicted that fleas would perform better on young and old than on adult rodents. To test this prediction, we determined bloodmeal size, rate of digestion and time of survival after a single bloodmeal inXenopsylla ramesisfeeding onMeriones crassusof different ages. Fleas took less blood from subadult and adult than from juvenile and old animals. Fleas digested blood of old hosts at the highest rate and blood of juvenile hosts most slowly. After a bloodmeal, fleas survived the longest if fed on a juvenile host. The effect of host gender on bloodmeal size and survival after a bloodmeal was manifested only in (a) subadult and adult hosts and (b) subadult hosts, respectively. Host gender affected the rate of digestion differently among digestion stages and host age cohorts. We explain the observed patterns in flea performance in terms of changes in the host's immune defences and nutritional quality of blood during the host's individual life. Our observations suggested that a host of a particular age could not be unequivocally predicted to be more or less beneficial for a parasite than a younger or an older host.

Seasonality of tuberculosis

OBJECTIVES

This study was designed to review previous studies and analyse the current knowledge and controversies related to seasonal variability of tuberculosis (TB) to examine whether TB has an annual seasonal pattern.

STUDY DESIGN AND METHODS

Systematic review of peer reviewed studies identified through literature searches using online databases belonging to PubMed and the Cochrane library with key words "Tuberculosis, Seasonal influence" and "Tuberculosis, Seasonal variation". The search was restricted to articles published in English. The references of the identified papers for further relevant publications were also reviewed.

RESULTS

Twelve studies conducted between the period 1971 and 2006 from 11 countries/regions around the world (South Western Cameroon, South Africa, India, Hong Kong, Japan, Kuwait, Spain, UK, Ireland, Russia, and Mongolia) were reviewed. A seasonal pattern of tuberculosis with a mostly predominant peak is seen during the spring and summer seasons in all of the countries (except South Western Cameroon and Russia).

CONCLUSIONS

The observation of seasonality leads to assume that the risk of transmission of M. tuberculosis does appear to be the greatest during winter months. Vitamin D level variability, indoor activities, seasonal change in immune function, and delays in the diagnosis and treatment of tuberculosis are potential stimuli of seasonal tuberculosis disease. Additionally, seasonal variation in food availability and food intake, age, and sex are important factors which can play a role in the tuberculosis notification variability. Prospective studies regarding this topic and other related subjects are highly recommended.

Immunological differences in women compared with men: overview and contributing factors

CITATION

Ghazeeri G, Abdullah L, Abbas O. Immunological differences in women compared with men: overview and contributing factors. Am J Reprod Immunol 2011; 66: 163-169 Gender differences in the innate and adaptive immune systems have long been observed in humans. These immunological differences in immune function manifest as diverse susceptibilities to different types of infections and varied risks of developing autoimmune disorders and maybe even, cancers. Several factors contribute to the development of this immunological dimorphism including sex hormones, genetic makeup, environmental causes, and more recently microchimerism. Although the aim behind this sexual immune dimorphism is still unclear, it is tempting to believe that the higher risk of developing autoimmune diseases in women somehow serves the higher evolutionary goal of reproduction and creating new life.

Factors affecting the pharmacokinetics of pegylated liposomal doxorubicin in patients

PURPOSE

There is significant inter-patient variability in the pharmacokinetics of pegylated liposomal doxorubicin (PLD). Identification of factors affecting the pharmacokinetics of PLD would enable personalization of therapy. We previously reported that age, gender, body composition, and monocytes affect the clearance of other liposomal agents. Therefore, we evaluated how these factors affect the pharmacokinetics of PLD.

METHODS

Pharmacokinetic studies of PLD were performed as part of phase I and II studies in 70 patients with solid tumors or Kaposi's sarcoma. The effects of monocyte count, age, gender, and body composition on PLD clearance were examined.

RESULTS

There was a 15.3-fold variability in PLD clearance. Body surface area-based dosing did not significantly reduce the variability in PLD clearance. The mean ± SD clearance for patients <60 years old and ≥60 years old were 54.6 ± 28.5 and 23.3 ± 10.8 mL/h/m(2), respectively (P < 0.0001), and for female and male patients were 23.7 ± 18.8 and 55.6 ± 26.8 mL/h/m(2), respectively (P < 0.0001). A reduction in pre-cycle monocyte count was associated with a greater reduction in PLD clearance.

CONCLUSIONS

Age, gender, and monocyte counts appear to correlate with PLD clearance. Further investigation of the association between these factors, PLD pharmacokinetics, and clinical outcomes (efficacy and toxicity) is warranted. These effects on the pharmacokinetics of PLD may be an approach for personalizing PLD therapy and may affect other pegylated liposomes and nanoparticle agents.

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.

Hormone levels are associated with clinical markers and cytokine levels in human localized cutaneous leishmaniasis

Leishmaniasis is a serious health problem in several parts of the world, and localized cutaneous leishmaniasis (LCL) is the most frequent presentation of the tegumentary form of this disease cluster. Clinical presentations of leishmaniasis are influenced by both parasite and host factors, with emphasis on the host immune response. Alterations in plasma hormone levels have been described in many infections, and changes in hormone levels could be related to an imbalanced cytokine profile. In the present work, we evaluated a group of patients with LCL to determine changes in plasma hormone levels (cortisol, DHEA-S, estradiol, prolactin and testosterone) and their association with clinical markers of disease (lesion size, dose used to reach cure and time to cure) and with cytokines produced by PBMC stimulated by SLA (IFN-γ, IL-10 and TNF-α). Individuals with LCL exhibited lower plasma levels of DHEA-S, prolactin and testosterone compared with sex-matched controls, whereas levels of cortisol and estradiol were similar between patients and controls. Plasma levels of cortisol, estradiol or prolactin positively correlated with at least one clinical parameter. Cortisol and prolactin levels exhibited a negative correlation with levels of IFN-γ, whereas no correlation was observed with IL-10 or TNF-α levels. A decrease in DHEA-S levels was observed in male LCL patients when compared to male healthy controls. No other differences between the sexes were observed. Our results indicate a role for neuroendocrine regulation that restricts Th1 responses in human LCL. It is possible that, although impairing parasite killing, such neuroimmunomodulation may contribute to limiting tissue damage.

The role of Intelectin-2 in resistance toAscaris suumlung larval burdens in susceptible and resistant mouse strains

The underlying mechanism of predisposition toAscarisinfection is not yet understood but host genetics are thought to play a fundamental role. We investigated the association between the Intelectin-2 gene and resistance in F2mice derived from mouse strains known to be susceptible and resistant to infection.Ascarislarvae were isolated from murine lungs and the number of copies of the Intelectin-2 gene was determined in F2mice. Intelectin-2 gene copy number was not significantly linked to larval burden. In a pilot experiment, the response to infection in parental mice of both sexes was observed in order to address the suitablity of female F2mice. No overall significant sex effect was detected. However, a divergence in resistance/susceptibility status was observed between male and, female hybrid offspring. The responsiveness toAscarisin mice is likely to be controlled by multiple genes and, despite a unique absence from the susceptible C57BL/6j strain, the Intelectin-2 gene does not play a significant role in resistance. The observed intra-strain variation in larval burden requires further investigation but we hypothesize that it stems from social/dominance hierarchies created by the presence of female mice and possibly subsequent hormonal perturbations that modify the intensity of the immune response.

Diphtheria-tetanus-pertussis vaccine administered simultaneously with measles vaccine is associated with increased morbidity and poor growth in girls. A randomised trial from Guinea-Bissau

BACKGROUND

Combined vaccination with diphtheria-tetanus-pertussis (DTP) and measles vaccine (MV) has been associated with increased mortality in observational studies. Among children missing MV and a dose of DTP and oral polio vaccine (OPV), we conducted a randomised trial of providing MV+DTP+OPV simultaneously, as currently recommended, or MV+OPV only, and examined the effect on morbidity and growth. We hypothesised that the MV+OPV group would experience less morbidity and grow better. Due to previous observations of sex differences in the non-specific effects of vaccinations, we analysed all data stratified by sex.

METHODS

At the Bandim Health Project in Guinea-Bissau, 568 children who were due to receive MV and who were missing either DTP3 or DTP booster were enrolled in the study. A subgroup of 332 children was followed intensively to register adverse events and infections in the first month after vaccination. A subgroup of 276 children was followed every third month for a year to monitor growth. All children were followed for one year for infectious diseases, consultations, and hospitalisations.

RESULTS

As expected, adverse events were more common in the MV+DTP+OPV group; diarrhoea and use of medication were increased among girls but not among boys (both p=0.02, test of interaction between DTP and sex). Febrile disease with vesicular rash, as well as consultations and hospitalisations tended to be more common in the MV+DTP+OPV group than in the MV+OPV group; the hazard ratio (HR) for febrile disease with vesicular rash was 1.86 (1.00; 3.47). The strongest tendencies for more febrile diseases and hospitalisations in the MV+DTP+OPV group were found in girls. Overall, growth did not differ by randomisation group. However, results differed by sex. Girls in the MV+DTP+OPV group had a consistent pattern of worse z-scores for weight, height, and mid-upper-arm-circumference (MUAC) than girls in the MV+OPV group. The effect was opposite for boys, with boys in the MV+OPV group faring worse than those in the MV+DTP+OPV group, the interaction test for sex and DTP being significant for weight at 6 and 9 months, for MUAC at 12 months and for weight-for-height at 3 and 9 months after randomisation.

CONCLUSION

This is the first randomised trial of the non-specific effects of DTP and supports that these effects may be sex-differential and of clinical and anthropometric importance. Combined vaccination with DTP+MV+OPV may be detrimental for girls.

Sex differences in destructive periodontal disease: exploring the biologic basis

BACKGROUND

Epidemiologic studies provide broad-based evidence that men are at greater risk for developing destructive periodontal disease than women, even after adjusting for behavioral and environmental factors, such as oral hygiene practice and smoking. What requires clarification, however, is whether sex-specific differences in immune function provide a plausible biologic basis for a sexual dimorphism in susceptibility to destructive periodontal disease. This review examines evidence that might provide an underlying biologic basis for a sexual dimorphism in the prevalence and severity of destructive periodontal disease.

METHODS

A narrative review of the literature related to sexual dimorphism in pathogen-mediated inflammatory diseases and immune response was retrieved from searches of computerized databases (MEDLINE, PubMed, and SCOPUS).

RESULTS

Sex steroids exert profound effects on multiple immunologic parameters regulating both the amplification and resolution of inflammation. Strong evidence exists for sexual dimorphisms in immune function, involving both innate and acquired immunity. Injury and infection have been associated with higher levels of inflammatory cytokines, including interleukin-1β and tumor necrosis factor-α, in men than women, paralleling observed sex-specific differences in periodontitis.

CONCLUSION

Differential gene regulation, particularly in sex steroid-responsive genes, may contribute to a sexual dimorphism in susceptibility to destructive periodontal disease.

Immunohistochemical expression of oestrogen and progesterone receptors during experimental acute and chronic murine Schistosomiasis mansoni

INTRODUCTION: The responsibility of Schistosoma mansoni in female infertility is still controversial. This study was conducted to evaluate the effect of acute and chronic schistosomiasis mansoni infection on the endometrium using immunohistochemical analysis of uterine hormone receptor expression. METHODS: Twenty-four nonpregnant swiss albino mice were divided into three groups: control, noninfected; acute; and chronic Schistosoma mansoni infection. Histological sections of uterine specimens were examined by light microscope with an image analyzing system to detect structural histological, estrogen receptor (ER) and progesterone receptor (PR) expression in the endometrium. RESULTS: No secretory phase was detected in the endometrium in acute and chronic Schistosoma infection. Hormone receptor expression (ER and PR) showed statistically significant differences among the groups (p< 0.05), with significant low ER hormone expression in chronic infection, compared to control proliferative, control secretory and acute infection cases, and statistically significant high PR expression in both acute and chronic infection cases compared to the control secretory cases (p< 0.05). CONCLUSIONS: Schistosomiasis mansoni seems to have an important impact on the hormone expression of affected women. Further studies to explore the mechanism of such changes are recommended.

Ecological immunology of bird-ectoparasite systems

Ecological immunology is a rapidly expanding field of research that attempts to explain variation in immune function across individuals, populations and species. Birds and ectoparasitic arthropods have frequently been used in attempts to measure the cost of immune function in relation to adult condition, nestling growth and other life history challenges. Unfortunately, most studies in ecological immunology have relied on assays of general immunocompetence that are not connected to actual parasites. A summary of potential interactions between the avian immune system and ectoparasites is provided and methods that can be used to test ecological questions in the context of naturally occurring host-parasite interactions are proposed.

Haptoglobin and sickle cell polymorphisms and risk of active trachoma in Gambian children

Background

Susceptibility and resistance to trachoma, the leading infectious cause of blindness, have been associated with a range of host genetic factors. In vitro studies of the causative organism, Chlamydia trachomatis, demonstrate that iron availability regulates its growth, suggesting that host genes involved in regulating iron status and/or availability may modulate the risk of trachoma. The objective was to investigate whether haptoglobin (Hp) haplotypes constructed from the functional polymorphism (Hp1/Hp2) plus the functional promoter SNPs -61A-C (rs5471) and -101C-G (rs5470), or sickle cell trait (HbAS, rs334) were associated with risk of active trachoma when stratified by age and sex, in rural Gambian children.

Methodology and Principal Findings

In two cross sectional surveys of children aged 6–78 months (n = 836), the prevalence of the clinical signs of active trachoma was 21.4%. Within boys, haplotype E (-101G, -61A, Hp1), containing the variant allele of the -101C-G promoter SNP, was associated with a two-fold increased risk of active trachoma (OR = 2.0 [1.17–3.44]). Within girls, an opposite association was non-significant (OR = 0.58 [0.32–1.04]; P = 0.07) and the interaction by sex was statistically significant (P = 0.001). There was no association between trachoma and HbAS.

Conclusions

These data indicate that genetic variation in Hp may affect susceptibility to active trachoma differentially by sex in The Gambia.

Sex steroids as inflammatory regulators

It is becoming increasingly clear that endogenous sex steroids are key players in a range of inflammatory contexts. Androgens and estrogens have been shown to have a profound influence on the function of inflammatory cells including macrophages and on the secretion and activation of a range of plasma-borne inflammatory mediators. The menopause and polymorphisms in estrogen receptor genes have separately been shown to affect the incidence of a range of inflammatory disorders. Sex steroids themselves have been shown to be protective in certain conditions; harmful in others. This review will summarize their documented effects on inflammatory processes, with particular focus on two areas that have received much recent attention: the antiatherosclerotic properties of estrogens in females and the wound healing effects of sex steroids.

Parasiticidal effect of 16alpha-bromoepiandrosterone (EpiBr) in amoebiasis and cysticercosis

The effect of the dehydroepiandrosterone analog 16alpha-bromoepiandrosterone (EpiBr) was tested on the tapeworm Taenia crassiceps and the protist Entamoeba histolytica, both in vivo and in vitro. Administration of EpiBr prior to infection with cysticerci in mice reduced the parasite load by 50% compared with controls. EpiBr treatment induced 20% reduction on the development of amoebic liver abscesses in hamsters. In vitro treatment of T. crassiceps and E. histolytica cultures with EpiBr, reduced reproduction, motility and viability in a dose- and time-dependent fashion. These results leave open the possibility of assessing the potential of this hormonal analog as a possible anti-parasite drug, including cysticercosis and amoebiasis.

Parasitic infections of three Mexican howler monkey groups (Alouatta palliata mexicana) living in forest fragments in Mexico

In order to better understand how patterns of parasitism in howler monkeys are affected by forest fragmentation, we carried out a 1 year survey of gastrointestinal parasites in fecal samples from three groups of Mexican howler monkeys inhabiting different forest fragments in the Los Tuxtlas Biosphere Reserve, Mexico. The study groups were chosen because the conditions in which they lived suggested a potentially negative gradient for parasite richness and a positive gradient for levels of parasitism. We report for the first time the presence of Entamoeba coli in Alouatta palliata mexicana and of hookworms (Family Ancylostomidae) in A. palliata. A reduction in home range size and an increase in disturbance was associated with a loss of parasite richness, which in general was high. Parasite prevalence and the proportion of contaminated samples in which each parasite taxon was present was also high in general and there were no differences between groups. A factor related to the generally high levels of parasitism in our study groups could be the high humidity in the study area, because this favors the survival of parasitic free forms and increases the chances of infection. This would also account for the tendency towards higher levels of parasitism observed in the rainy season. Finally we did not find a pattern relating sex and parasitism.

Understanding the vertebrate immune system: insights from the reptilian perspective

Reptiles are ectothermic amniotes, providing the key link between ectothermic anamniotic fishes and amphibians, and endothermic amniotic birds and mammals. A greater understanding of reptilian immunity will provide important insights into the evolutionary history of vertebrate immunity as well as the growing field of eco-immunology. Like mammals, reptile immunity is complex and involves innate, cell-mediated and humoral compartments but, overall, there is considerably less known about immune function in reptiles. We review the current literature on each branch of the reptilian immune system, placing this information in context to other vertebrates. Further, we identify key areas that are prime for research as well as areas that are lagging because of lack of reagents in non-model systems.

The role of sex hormones in the development of Th2 immunity in a gender-biased model of Trichuris muris infection

Trichuris muris infection is an ideal model for defining T-cell-driven immunity, and also provides essential insights that may impact on potential helminth therapies currently in development. Conflicting host variables determine the efficiency of such treatments and we have identified host-derived sex steroid hormones as key factors in the development of immunity. The female-associated hormone 17-β estradiol (E2) significantly enhanced the generation of a Th2 response in vitro; however, this stimulatory effect was found to be dispensable for the generation of immunity to Trichuris in the gender-biased IL-4KO mouse model. In contrast, the male-associated hormone dihydrotestosterone significantly inhibited the T-cell stimulatory capacity of DC and directly suppressed the immune response of male IL-4KO mice, with worm expulsion restored following castration. This finding was associated with dramatically reduced IL-18 mRNA expression suggesting androgens may act via this cytokine to suppress Th2 immunity to Trichuris. This study has critical implications for the development and efficacy of potential helminth therapeutics and identifies host gender – specifically sex hormones – as important factors in the development of Th2 immunity in susceptible and immunocompromised mice.

The blood parasite Haemoproteus reduces survival in a wild bird: a medication experiment

While avian chronic haemoparasite infections induce reproductive costs, infection has not previously been shown to affect survival. Here, we experimentally reduced, through medication, the intensity of infection by Haemoproteus parasites in wild-breeding female blue tits Cyanistes caeruleus. However, this treatment did not reduce the intensity of infection in males or the intensity of infection by Leucocytozoon. Medicated females, but not males, showed increased local survival until the next breeding season compared with control birds. To our knowledge, this is the first empirical evidence showing long-term direct survival costs of chronic Haemoproteus infections in wild birds.

The impact of concomitant infections by Trypanosoma cruzi and intestinal helminths on the health of wild golden and golden-headed lion tamarins

A 4-year longitudinal epidemiological study was carried out to evaluate the effect of infection by Trypanosoma cruzi and three intestinal helminth species on the health of golden and golden-headed lion tamarins. We evaluated health using analysis of blood counts, serum proteins, electrophoretograms, electrocardiograms and a health ranking based on physiological parameters. Among the helminths, Trichostrongylidae was demonstrated as the most pathogenic, followed by Prosthenorchis sp.; concomitant infection by Spiruridae may exacerbate the negative effects of the other two helminths. T. cruzi infection was not highly detrimental to the health of the study animals and was correlated with increased resilience to helminths. Tamarins younger than 1-year of age or older than 4-years had lower health condition. Golden-headed lion tamarins were in lower health condition because of higher parasitic prevalence. Our data suggest that when parasite community pathogenicity and prevalence are high, natural selection will allow survival only of lion tamarins in the best health condition.

Gonadectomy inhibits development of experimental amoebic liver abscess in hamsters through downregulation of the inflammatory immune response

Incidence of amoebic liver abscess (ALA) in human males is considerably higher than in females, suggesting a role for sex hormones in this parasite infection. We describe here the effect of hamster gonadectomization on the development of ALA. After monitoring the decrease of oestradiol in females and testosterone in males to undetectable levels by ELISA and Radio Immuno Assay (RIA) in serum, hamsters were intraportally infected with Entamoeba histolytica trophozoites and killed 7 days later. ALA was absent in 50% of male and 15% of female gonadectomized (Gdx) hamsters, in comparison with 100% infection in non-Gdx controls. This protection against ALA in Gdx hamsters was concomitant to a comparatively scarce inflammatory infiltrate and necrosis surrounding clusters of trophozoites in the liver tissue, as well as to a lack of response of spleen cells to Con A, evaluated in proliferation assays. As tissue damage in ALA has been associated with a local inflammatory Th1 response, we determined the profile of response in hamsters by immunohistochemistry on liver sections. In contrast to strong Th1 responses in non-Gdx animals, Gdx females and males exhibited Th2 and Th3 profiles of cytokines, respectively, suggesting that protection against ALA following gonadectomization, could be related to downregulation of liver Th1 response during amoebic infection.

Immunophenotypical characterization in Andalusian horse: variations with age and gender

Assessment of lymphocyte subsets is an effective method for characterizing disorders such as leukemia, lymphomas, autoimmune and infectious diseases. In order to clinically interpret these parameters, normal reference values should be set, estimating age- and gender-related variations. This research aimed to: (1) characterize lymphocyte subpopulations in Andalusian horse, and (2) evaluate age and gender-related variations of lymphocyte subsets. Jugular blood samples were obtained from 159 animals, 77 males and 82 females, belonging to four age groups-1: 1-2 years (N=39; 21 males and 18 females), 2: 2-3 years (N=38; 16 males and 22 females), 3: 3-4 years (N=41; 19 males and 22 females) and 4: 4-7 years (N=41; 21 males and 20 females). T lymphocytes subsets were quantified by flow cytometry with monoclonal antibodies specific for CD2, CD4 and CD8 cell markers. B and NK cell counts were estimated by using a mathematical formula. No variations were found in T, B lymphocytes and NK cells between males and females. Animals of group 1 and 2 had a higher number of CD2, T, CD4+, CD8+, B lymphocytes and NK cells than animals of groups 3 and 4. The percentage of CD2 in group 1 was significantly lower than in group 4. The percentage of T and CD4+ lymphocytes in the group 1 were significantly higher than groups 2 and 3, respectively. Whereas the percentage of B cells calculated by flow cytometry was significantly lower in group 2 compared to group 4, the percentage of B cells calculated by a mathematical formula was higher in group 1. NK cells percentage was significantly lower in group 3 and 4 than in younger animals. In conclusion, in Andalusian horse, gender does not influence absolute numbers and percentages of T, B and NK. There is an age-related decline in absolute number of CD2, T, CD4+ and CD8+ lymphocytes, B lymphocytes and NK cells, with increasing percentage of CD2, T, CD4+ and B lymphocytes, and a decrease in NK with no differences in CD4/CD8 ratio. The decline of lymphocyte population numbers with age is a natural process in many animal species, and could be the origin for immune dysfunction observed in geriatric individuals.

Disruption of Th2 immunity results in a gender-specific expansion of IL-13 producing accessory NK cells during helminth infection

Host gender has previously been identified as a determining factor in the resolution of Trichuris muris infection in mice lacking IL-4 (IL-4KO BALB/c). Worm expulsion in these mice is delayed, but occurs in females. In this study we were able to demonstrate delayed expulsion occurs at day 26 post infection and is associated with the production of the key Th2-associated cytokine IL-13 by both CD4(+) T cells and an auxiliary DX5(+) NK cell source, as well as a concurrent reduction in proinflammatory cytokines. NK cell number was comparably increased in both sexes, but NK cells from male mice were found to express higher levels of the chemokine receptor CXCR3. Depletion of CD4(+) T cells completely prevented parasite expulsion, whereas loss of NK cells resulted in a mild, but significant delay. Furthermore, IL-18 is a cytokine with the capacity to enhance both Th1 and Th2 responses found to be dispensable for worm expulsion in female mice but was a key factor for the suppression of the Th2 response in male IL-4KO mice. In contrast neutralization of IFN-gamma resulted in a complete restoration of typical wild-type BALB/c expulsion kinetics. This study sheds further light on the role of accessory NK cells in supplementing the IL-13-driven immune response when normal Th2 immunity is disrupted, and further identifies host gender as a key factor in determining the generation of "NK cell help".

Rapid fluctuation in infection levels of Neoheterobothrium hirame (Monogenea) in Japanese flounder Paralichthys olivaceus in the Joban area, Japan

Neoheterobothrium hirame a haematophagous monogenean parasite on Japanese flounder Paralichthys olivaceus occurred at high prevalences (> 70%) from 1999 to 2002 but thereafter declined and remained low (< 20%) from 2003 to 2005 in the Joban area, Japan. In 2006, N. hirame became abundant again reaching a prevalence of 63%. Generalized linear models explained these rapid fluctuations in infection in relation to inshore water temperature, which affected the reproductive success of the parasite, and also the encounter rate between host and parasite through changes in their respective population densities. Severely anaemic fish were few, 2.4% even in 1999-2002 and 2006, suggesting that the effect of N. hirame infection on the P. olivaceus population was small in this area.

Invasive amebiasis: a microcirculatory disorder?

The two current models of invasive amebiasis both hold that direct contact of toxic molecules and amebas with tissue produces the necrotic areas characteristic of this disorder. Whereas one model characterizes these toxic molecules as amebic products (e.g., lectins, amebapores, cysteine proteinases and other proteolytic enzymes), the other describes them as products of the inflammatory response (e.g., cytokines, nitric oxide, reactive oxygen intermediates and cytotoxic granules). Both these models can account for necrotic areas with many amebas present and with acute inflammation, but not those with few or no amebas present or with scarce inflammation. A new model poses that an inadequate immune response leads to a continuous and prolonged activation of endothelial cells (ECs) by amebas, amebic molecules and cytokines, which triggers the mechanisms leading to necrosis. Other toxic molecules later contribute to EC activation: nitric oxide, reactive oxygen intermediates, the activated complement and proteases. Hyperactivated endothelial cells continuously express adhesion molecules (e.g., ICAM-1 and E-selectin), pro-coagulant molecules (e.g., tissue factor, von Willebrand factor, and the plasminogen activator inhibitor), resulting in ever greater inflammation and thrombosis, which eventually reduces or blocks blood flow in some vessels and starves certain tissue areas of an adequate oxygen and nutrient supply. When necrotic areas first develop, they are surrounded by inflammatory cells due to the acute inflammation at this stage. However, these cells are starved of oxygen and essential nutrients by the same microcirculatory dysfunction. The increasing concentration of nitric oxide during amebiasis eventually has an anti-inflammatory and vasodilating effect, creating a new mechanism for the microcirculatory dysfunction. This local microcirculatory dysfunction can explain necrotic areas in the presence of many, few, or no amebas, with abundant or scarce inflammation.

[Relationship between patient profile and feverishness developed during interferon-ribavirin combination therapy of chronic hepatitis C patients]

To investigate the relation between tendency of feverishness and patient profile in pegylated interferon (peginterferon) and ribavirin combination therapy, we performed a retrospective survey of the medical charts of patients with chronic hepatitis C that have been on interferon therapy for the past two years. The sample was 36 patients (18 males, 18 females, aged 30 to 67 years, average of 57.5 years) who were hospitalized for the introduction of peginterferon-alpha 2b and ribavirin combination therapy and did not use NSAIDs before the administration of interferon. We examined body temperature and laboratory values (AST, ALT, WBC, Hb, PLT, BUN, Cr, HCV RNA level, and HCV genotype) for one week from the initiation of peginterferon administration to one week after the administration. Tendency of feverishness was classified into two groups according to the time to reach maximum body temperature. The early fever-developing group reached maximum body temperature within 12 hours of the administration, and the slow fever-developing group reached maximum body temperature after 12 hours post administration. The early fever-developing group had a significantly higher maximum body temperature (early group, 38.5 degrees C+/-0.55; slow group, 37.8 degrees C+/-0.55), more persistent fever (early group, 71.0 h+/-31.3; slow group, 36.5 h+/-41.8), and a higher percentage of females (early group, 80.0%; slow group, 28.6%). Moreover, females and elderly patients developed significantly higher fever (temperature difference 0.78 degrees C) early (8.5 h) after peginterferon administration. These results indicate the need for careful observation of females and elderly patients in the early stage of an initial treatment of chronic hepatitis C with peginterferon.

Immune activation suppresses plasma testosterone level: a meta-analysis

Females often select mates on the basis of sexual signals, which can be reliable indicators of male quality when the costliness of these signals prevents cheating. The immunocompetence handicap hypothesis (ICHH) provides a mechanistic explanation of these costs, by proposing a trade-off between immune function and sexual displays. This trade-off arises because testosterone enhances sexual signals, but suppresses immune function. Many studies have investigated the ICHH by administrating testosterone, and a recent meta-analysis found little evidence that testosterone suppressed immune function. However, another component of the ICHH, which has received less empirical interest, suggests that there may also be an interaction in the other direction, with immune activation suppressing testosterone levels. We present a meta-analysis to test for this effect. Overall, there was a strong suppressive effect of experimental immune activation on testosterone levels (r=-0.52), regardless of whether live pathogens or non-pathogenic antigens were used to challenge the immune system. The latter is important because it shows that immune activation per se suppresses testosterone levels. Thus, a trade-off between immunocompetence and sexual displays may primarily be generated by the effect of immune activation on testosterone, rather than the opposite effect that has received most attention.

Estrogen and progesterone affect responses to malaria infection in female C57BL/6 mice

BACKGROUND

Previous data from our laboratory suggest that gonadally intact C57BL/6 male mice are more likely than their female counterparts to die from Plasmodium chabaudi infection, to recover more slowly from weight loss and hematocrit loss, and to have reduced interferon-gamma (IFN-gamma) and interleukin-10 (IL-10) responses. Removal of the ovaries, and hence, the primary production of sex steroids in females, reverses these differences.

OBJECTIVE

We hypothesized that sex differences in response to P chabaudi may be mediated by differential synthesis of IFN-gamma and IL-10 that is influenced by estrogen, progesterone, or both.

METHODS

C57BL/6 female mice (n = 200; n = 10/time point/treatment/experiment) were ovariectomized and implanted with a 21-day controlled-release pellet containing either 0.1 mg of 17beta-estradiol (E(2)), 10 mg of progesterone (P(4)), 0.1 mg of E(2) plus 10 mg of P(4), or cholesterol (placebo). Females were inoculated with 10(6)P chabaudi-infected erythrocytes. Body mass, body temperature, hematocrit, parasitemia, cytokine production, and antibody responses were monitored 0, 3, 5, 7, 10, 14, and 21 days postinoculation.

RESULTS

Administration of E(2), either alone or in combination with P(4), mitigated infection-induced weight loss, hematocrit loss, and hypothermia, compared with females receiving placebo pellets (P < 0.05 in each case). Hormone treatment did not affect levels of parasitemia. Females administered E(2) alone or in combination with P(4) produced 4 to 7 times higher IFN-gamma and IL-10 during peak parasitemia than did females implanted with pellets containing either P(4) alone or placebo (P < 0.05 in each case). Exposure to E(2), either alone or in combination with P(4), increased anti-P chabaudi immunoglobulin G (IgG1) responses and the ratio of IgG1 to IgG2c (P < 0.05 in each case).

CONCLUSION

This animal study suggests that physiological levels of estrogen, rather than progesterone, enhance immunity and, possibly, protect females from disease symptoms during malaria infection.

Heritability of human hookworm infection in Papua New Guinea

Hookworms infect approximately 740 million humans worldwide and are an important cause of morbidity. The present study examines the role of additive genetic effects in determining the intensity of hookworm infection in humans, and whether these effects vary according to the sex of the host. Parasitological and epidemiological data for a population of 704 subjects in Papua New Guinea were used in variance components analysis. The ‘narrow-sense’ heritability of hookworm infection was estimated as 0·15±0·04 (P<0·001), and remained significant when controlling for shared environmental (household) effects. Allowing the variance components to vary between the sexes of the human host consistently revealed larger additive genetic effects in females than in males, reflected by heritabilities of 0·18 in females and 0·08 in males in a conservative model. Household effects were also higher in females than males, although the overall household effect was not significant. The results indicate that additive genetic effects are an important determinant of the intensity of human hookworm infection in this population. However, despite similar mean and variance of intensity in each sex, the factors responsible for generating variation in intensity differ markedly between males and females.

Schistosoma mansoni: Microarray analysis of gene expression induced by host sex

Schistosoma mansoni is a digenetic trematode and a human parasite responsible for high social and economic impact. Although some authors have studied the effect of host hormones on parasites, not much is known about the effects of host sex on gene expression in Schistosomes. In order to study gene transcripts associated with the host sex, we compared the gene expression profiles of both male and female unisexual adult S. mansoni parasites raised on either male or female hosts, using DNA microarrays. Our results show that host sex caused differential expression of at least 11 genes in female parasites and of 134 in male parasites. Of the differentially expressed genes in female worms, 10 were preferentially expressed in female worms from male mice, while of the 134 differentially expressed genes in male parasites, 79 (59%) were preferentially expressed in worms from female mice. Further investigation of the role of each of those genes will help understand better their importance in the pathogenesis of Schistosomiasis.

Incubation Environment Affects Immune System Development in a Turtle with Environmental Sex Determination

The developmental environment can have lasting effects on posthatching phenotype in oviparous animals. Innate immune response is one important component of fitness in vertebrates because it provides a generalized defense against infection. In addition, because male vertebrates are at a higher risk of infection than females, males may benefit more from increased innate immunity than females. We determined the effects of incubation temperature on the innate immune response of hatchling map turtles (Graptemys) by incubating eggs at a range of male and female producing-temperatures and assessing plasma complement activity in the resulting hatchlings. We found a significant effect of incubation environment on circulating complement in hatchling Graptemys ouachitensis, with male-producing temperatures yielding the highest innate immune response. Most important, these results demonstrate that immune response is affected by developmental environment in a species with environmental sex determination, potentially resulting in sex differences in the ability to fend off pathogens.

Steroidogenic capacity of Trypanosoma cruzi trypomastigotes

American Trypanosomiasis is caused by the hemoflagellate Trypanosoma cruzi (T. cruzi) and affects millions of persons causing variable degrees of digestive and heart disturbances. As far as we concerned, T. cruzi capacity to synthesize steroid hormones has not been investigated. Therefore, the aim of this work was to investigate the capacity of T. cruzi trypomastigotes to transform tritiated steroid precursors into androgens and estrogens. The T. cruzi Tulahuén strain was obtained from mice blood. The trypomastigotes were cultured for 6 and 24h in Dulbbeco's modified Eagle's medium plus FCS and antibiotics. Tritiated dehydroepiandrosterone or androstendione were added to the culture media and parasites were incubated for 6 or 24h. The cultures were centrifuged and ether extracted. The steroids were analyzed by thin layer chromatography (TLC) in two solvent systems. After incubation with 3H-androstenedione, T. cruzi trypomastigotes synthesized 3H-testosterone (T), 3H-17beta-estradiol (E2) and 3H-estrone (E1). Metabolism of 3H-DHEA by the parasites yielded 3H-androstendione and 3H-androstendiol at 6h of incubation. The recrystallization procedure further demonstrated the 3H-androstendiol and 3H-17beta-estradiol syntheses. Results indicate for the first time that T. cruzi trypomastigotes produce androgens and estrogens when incubated in the presence of steroid precursors and suggest the presence of active parasite steroidogenic enzymes.