Does the gender difference in interferon production seen in picornavirus-infected spleen cell cultures from ICR Swiss mice have any in vivo significance?

Disease parameters following ocular herpes simplex virus type 1 infection are similar in male and female BALB/C mice

Sex related differences in the incidence or severity of infection have been described for multiple viruses. With herpes simplex viruses, the best example is HSV-2 genital infection where women have a higher incidence of infection and can have more severe infections than men. HSV-1 causes several types of infections including skin and mucosal ulcers, keratitis, and encephalitis in humans that do not appear to have a strong biological sex component. Given that mouse strains differ in their MHC loci it is important to determine if sex differences occur in multiple strains of mice. Our goal was to answer two questions: Are virus related sex differences present in BALB/C mice and does virulence of the viral strain have an effect? We generated a panel of recombinant HSV-1 viruses with differing virulence phenotypes and characterized multiple clinical correlates of ocular infection in BALB/c mice. We found no sex-specific differences in blepharitis, corneal clouding, neurovirulence, and viral titers in eye washes. Sex differences in neovascularization, weight loss and eyewash titers were observed for some recombinants, but these were not consistent across the phenotypes tested for any recombinant virus. Considering these findings, we conclude that there are no significant sex specific ocular pathologies in the parameters measured, regardless of the virulence phenotype following ocular infection in BALB/c mice, suggesting that the use of both sexes is not necessary for the bulk of ocular infection studies.

Testosterone Promotes the Intestinal Replication and Dissemination of Coxsackievirus B3 in an Oral Inoculation Mouse Model

Enteroviruses initiate infection in the gastrointestinal tract, and sex is often a biological variable that impacts pathogenesis. Previous data suggest that sex hormones can influence the intestinal replication of Coxsackievirus B3 (CVB3), an enterovirus in the Picornaviridae family. However, the specific sex hormone(s) that regulates intestinal CVB3 replication is poorly understood. To determine if testosterone promotes intestinal CVB3 replication, we orally inoculated male and female Ifnar^-/- mice that were treated with either placebo or testosterone-filled capsules. Following oral inoculation, we found that the testosterone-treated male and female mice shed significantly more CVB3 in their feces than did the placebo-treated mice, indicating that testosterone enhances intestinal replication. Similarly, testosterone enhanced viral dissemination in both sexes, as we observed higher viral loads in peripheral tissues following infection. Further, the testosterone-treated male mice also had a higher mortality rate than did the testosterone-depleted male mice. Finally, we observed that testosterone significantly affected the immune response to CVB3. We found that testosterone broadly increased proinflammatory cytokines and chemokines while decreasing the number of splenic B cells and dendritic cells following CVB3 infection. Moreover, while testosterone did not affect the early CD4 T cell response to CVB3, testosterone reduced the activation of CD8 T cells. These data indicate that testosterone can promote intestinal CVB3 replication and dissemination while also impacting the subsequent viral immune response. IMPORTANCE Biological sex plays a significant role in the outcomes of various infections and diseases. The impact of sex hormones on the intestinal replication and dissemination of Coxsackievirus B3 remains poorly understood. Using an oral inoculation model, we found that testosterone enhances CVB3 shedding and dissemination in male and female mice. Further, testosterone can alter the immune response to CVB3. This work highlights the role of testosterone in CVB3 pathogenesis and suggests that sex hormones can impact the replication and dissemination of enteric viruses.

Hantavirus pulmonary syndrome in Argentina, 1995-2008

We report a large case series of hantavirus pulmonary syndrome (HPS) in Argentina that was confirmed by laboratory results from 1995 through 2008. The geographic and temporal distribution of cases by age, sex, fatality rate, and risk factors for HPS was analyzed. A total of 710 cases were unequally distributed among 4 of the 5 Argentine regions. Different case-fatality rates were observed for each affected region, with a maximum rate of 40.5%. The male-to-female ratio for HPS case-patients was 3.7:1.0; the case-fatality rate was significantly higher for women. Agriculture-associated activities were most commonly reported as potential risk factors, especially among men of working age. Although HPS cases occurred predominantly in isolation, we identified 15 clusters in which strong relationships were observed between members, which suggests ongoing but limited person-to-person transmission.

Sexual dimorphism in innate immune responses to infectious organisms

Gender has long been known to be a contributory factor in the incidence and progression of disorders associated with immune system dysregulation. More recently, evidence has accumulated that gender may also play an important role in infectious disease susceptibility. In general, females generate more robust and potentially protective humoral and cell-mediated immune responses following antigenic challenge than their male counterparts. In contrast, males have frequently been observed to mount more aggressive and damaging inflammatory immune responses to microbial stimuli. In this article we review the evidence for sexual dimorphism in innate immune responses to infectious organisms and describe our recent studies that may provide a mechanism underlying gender-based differences in conditions such as bacterial sepsis.

CD1d mediates T-cell-dependent resistance to secondary infection with encephalomyocarditis virus (EMCV) in vitro and immune response to EMCV infection in vivo

The innate and adaptive immune responses have evolved distinct strategies for controlling different viral pathogens. Encephalomyocarditis virus (EMCV) is a picornavirus that can cause paralysis, diabetes, and myocarditis within days of infection. The optimal innate immune response against EMCV in vivo requires CD1d. Interaction of antigen-presenting cell CD1d with distinct natural killer T-cell ("NKT") populations can induce rapid gamma interferon (IFN-gamma) production and NK-cell activation. The T-cell response of CD1d-deficient mice (lacking all NKT cells) against acute EMCV infection was further studied in vitro and in vivo. EMCV persisted at higher levels in CD1d-knockout (KO) splenocyte cultures infected in vitro. Furthermore, optimal resistance to repeat cycles of EMCV infection in vitro was also shown to depend on CD1d. However, this was not reflected in the relative levels of NK-cell activation but rather by the responses of both CD4(+) and CD8(+) T-cell populations. Repeated EMCV infection in vitro induced less IFN-gamma and alpha interferon (IFN-alpha) from CD1d-deficient splenocytes than with the wild type. Furthermore, the level of EMCV replication in wild-type splenocytes was markedly and specifically increased by addition of blocking anti-CD1d antibody. Depletion experiments demonstrated that dendritic cells contributed less than the combination of NK and NKT cells to anti-EMCV responses and that none of these cell types was the main source of IFN-alpha. Finally, EMCV infection in vivo produced higher levels of viremia in CD1d-KO mice than in wild-type animals, coupled with significantly less lymphocyte activation and IFN-alpha production. These results point to the existence of a previously unrecognized mechanism of rapid CD1d-dependent stimulation of the antiviral adaptive cellular immune response.

The herpes simplex virus type 1 locus that encodes the latency-associated transcript enhances the frequency of encephalitis in male BALB/c mice

Herpes simplex virus type 1 (HSV-1) is the leading cause of virus-induced encephalitis; however, the viral genes that regulate encephalitis have not been well characterized. In this study, we tested whether the LAT (latency-associated transcript) locus regulates the frequency of encephalitis in male or female mice. Male BALB/c mice are more susceptible to HSV-1-induced encephalitis than age-matched female BALB/c mice. Deletion of LAT coding sequences reduced the frequency of encephalitis. A recombinant virus containing the first 1.5 kb of the LAT coding sequence induces levels of encephalitis in male BALB/c mice similar to those induced by wild-type HSV-1.

Treatment-related death in childhood acute lymphoblastic leukaemia in the Nordic countries: 1992-2001

Despite continuously more successful treatment of childhood acute lymphoblastic leukaemia (ALL), 2-5% of children still die of other causes than relapse. The Nordic Society of Paediatric Haematology and Oncology-ALL92 protocol included 1652 patients < or =15 years of age with precursor B- and T-cell ALL diagnosed between 1992 and 2001. Induction deaths and deaths in first complete remission (CR1) were included in the study. A total of 56 deaths (3%) were identified: 19 died during induction (1%) and 37 in CR1 (2%). Infection was the major cause of death in 38 cases. Five patients died of early death before initiation of cytotoxic therapy. Five patients died because of toxicity of inner organs and one of accidental procedure failures. Seven patients died of complications following allogenic haematopoietic stem cell transplantation (HSCT) in CR1. Girls were at higher risk of treatment-related death (TRD) [relative risk (RR) = 2.2; 95% confidence interval (CI(95%)): 1.2-4.0, P < 0.01], mostly because of infections. Risk of TRD was also higher in children with Down syndrome (RR = 4.5; CI(95%): 2.0-10.2, P < 0.00). In conclusion, 3% of children with ALL died of TRD, with bacterial infections as the most common cause of death. Girls and Down syndrome patients had a higher risk of TRD. Infections still remain a major challenge in childhood ALL.

Sex-dependent susceptibility to Listeria monocytogenes infection is mediated by differential interleukin-10 production

It is well documented that sex-dependent factors affect susceptibility to infection, with most mouse models demonstrating higher resistance in females. We made the unexpected observation that infection with the intracellular bacterium Listeria monocytogenes showed an opposite pattern in several commonly used inbred mouse strains: female C57BL/6J, BALB/c, C3H/HeN, and CBA/J mice were significantly more susceptible to Listeria infection. The pronounced sensitivity of females to Listeria, which was revealed by significantly higher lethality rates, correlated also with increased bacterial numbers in organ tissues (spleen and liver) and several immunological changes in peripheral blood samples. Surprisingly, increased severity of infection in females was associated with elevated interleukin-10 (IL-10) levels in plasma. Experiments using Il10 knockout mice, for which no differences between the susceptibilities of males and females to Listeria infection could be detected, confirmed the important role of this immunosuppressive cytokine for the outcome of disease. Our findings are likely to have clinical relevance, since similar sex differences with regard to infection with Listeria monocytogenes and other intracellular pathogens have been reported for humans.

Herpes simplex virus type 1 infection via the bloodstream with apolipoprotein E dependence in the gonads is influenced by gender

Herpes simplex virus type 1 (HSV-1) causes disease in humans and animals. Infection usually occurs via the neural route and possibly occurs via the hematogenous route. The latter, however, is the main route by which immunosuppressed individuals and neonates are infected. Gender-dependent differences in the incidence and severity of some viral infections have been reported. To detect differences between the sexes with respect to HSV-1 colonization and disease, the characteristics of both acute and latent infections in hematogenously infected male and female mice were compared. In acute infection, the female mice had a poorer outcome: HSV-1 colonization was more effective, especially in the gonads and brain. In the encephalon, the midbrain had the highest viral load. In latent infection, brain viral loads were not significantly different with respect to sex. Significant differences were seen, however, in the blood and trigeminal ganglia: HSV-1 seroprevalence was observed in females, with no virus detected in males. In brain dissections, only the cerebral cortex of the females had viral loads statistically higher than those observed in the males. The spread of the virus to several organs of interest during acute infection was examined immunohistochemically. Female mice showed greater viral immunostaining, especially in the adrenal cortex, gonads, and midbrain. In male mice, HSV-1 was detected predominantly in the adrenal cortex. It was also found that apolipoprotein E promotes virus colonization of the ovaries, the APOE gene dose being directly related to viral invasiveness.

Innate immune response to encephalomyocarditis virus infection mediated by CD1d

CD1d-reactive natural killer T (NKT) cells can rapidly produce T helper type 1 (Th1) and/or Th2 cytokines, can activate antigen-presenting cell (APC) interleukin-12 (IL-12) production, and are implicated in the regulation of adaptive immune responses. The role of the CD1d system was assessed during infection with encephalomyocarditis virus (EMCV-D), a picornavirus that causes acute diabetes, paralysis and myocarditis. EMCV-D resistance depends on IL-12-mediated interferon-gamma (IFN-gamma) production. CD1d-deficient mice, which also lack CD1d-reactive NKT cells, were substantially more sensitive to infection with EMCV-D. Infected CD1d knockout mice had decreased IL-12 levels in vitro and in vivo, and indeed were protected by treatment with exogenous IL-12. IFN-gamma production in CD1d knockout mice was decreased compared with that in wild-type (WT) mice in response to EMCV-D in vitro, although differences were not detected in vivo. Treatment with anti-asialo-GM1 antibody, to deplete NK cells, caused a marked increase in susceptibility of WT mice to EMCV-D infection, whereas CD1d knockout mice were little affected, suggesting that NK-cell-mediated protection is CD1d-dependent. Therefore, these data indicate that CD1d is essential for optimal responses to acute picornaviral infection. We propose that CD1d-reactive T cells respond to early immune signals and function in the innate immune response to a physiological viral infection by rapidly augmenting APC IL-12 production and activating NK cells.

Identification of Friend murine retrovirus-infected immune cells and studies of the effects of sex and steroid hormones in the early phase of infection

Male mice are more susceptible than female mice to the murine retrovirus FIS-2. We previously reported that sex-related factors influence early virus replication via mechanisms involving a glucocorticoid response element (GRE) in the long terminal repeat (LTR) enhancer region. In the present study, we investigated further the influence of sex and steroid hormones on early murine retrovirus dissemination and immune functions. In male mice we found a correlation between an early expansion of the CD8+ cell subset and rapid infection of lymphocytes, including CD8+ cells. Virus load in blood declined faster in females than in males, and the postpeak declines coincided with more rapidly generation of antibodies against virus-positive cells. Moreover, female-derived T-cells responded better to in vitro mitogen stimuli than male-derived T-cells. Physiological concentrations of progesterone and dexamethasone induced a dose-dependent inhibition of T-cell proliferation. Administration of progestin in vivo did not modify early FIS-2 production in female mice. Male castrated mice, who were notably less involved in aggressive behaviour and fighting compared to male control mice, had a significant delay of virus dissemination. We suggest that testosterone-dependent aggression, with successive enhanced stress hormone levels, may influence both FIS-2 replication and immune responses during infection.

Gender influences herpes simplex virus type 1 infection in normal and gamma interferon-mutant mice

Gender influences the incidence and severity of some bacterial and viral infections and autoimmune diseases in animal models and humans. To determine a gender-based difference, comparisons were made between male and female mice inoculated with herpes simplex virus type 1 (HSV-1) by the corneal route. Mortality was higher in the male mice of the three strains tested: 129/Sv//Ev wild type, gamma interferon (IFN-gamma) knockout (GKO), and IFN-gamma receptor knockout (RGKO). Similarly, in vivo HSV-1 reactivation occurred more commonly in male mice, but the male-female difference in reactivation was restricted to the two knockout strains and was not seen in the 129/Sv//Ev control. Comparison among male mice of the three strains showed a higher mortality of the RGKO mice and a higher reactivation rate of the GKO and RGKO mice than of the 129/Sv//Ev males. In contrast, female RGKO and GKO mice did not differ from female 129/Sv//Ev controls in either mortality or reactivation. HSV-1 periocular and eyelid disease was also more severe in male and dihydrotestosterone (DHT)-treated female mice than in control female mice. These results show a consistent gender difference in HSV-1 infection, with a worse outcome in male mice. In addition, the results comparing GKO and RGKO mice to controls show differences only in male mice, suggesting that some effects of IFN-gamma, a key immunoregulatory molecule, are gender specific.

Cytokines produced early in picornavirus infection reflect resistance or susceptibility to disease

Gender bias favoring female resistance to picornavirus disease is not seen in ICR Swiss mice following infection with the MM strain of encephalomyocarditis virus (EMCV) (causing encephalitis and death) as it is with D variant of EMCV (causing diabetes in males). To define this difference, an in vitro virus-infected splenocyte culture system was used to explore virus effects on lymphoid cells. Infected and sham-infected splenocyte cultures, prepared from both genders of mice and infected with either virus variant, were examined for immunoregulatory cytokines in the first 24 h of infection using ELISA or bioassays. Disease resistance was associated with increased levels of interferon-y (IFN-gamma) and undetectable levels of interleukin-10 (IL-10) by 12 h postinfection in splenocytes from ICR Swiss females infected with EMCV-D. Disease susceptibility was associated with high levels of IL-10 at 12 h after infection of spleen cells from ICR Swiss males infected with EMCV-D or from both genders infected with EMCV-MM. This information was used to protect susceptible mice against picornavirus disease (either diabetes or death) by giving them an inducer of IFN-alpha/beta, to induce natural killer (NK)-like cells to produce high levels of IFN-gamma and rat monoclonal anti-IL-10 to neutralize the effects of mouse IL-10.