Kinetics and genetics of herpes simplex virus-induced antibody formation in mice

Impact of Type I Interferon on the Safety and Immunogenicity of an Experimental Live-Attenuated Herpes Simplex Virus 1 Vaccine in Mice

Viral fitness dictates virulence and capacity to evade host immune defenses. Understanding the biological underpinnings of such features is essential for rational vaccine development. We have previously shown that the live-attenuated herpes simplex virus 1 (HSV-1) mutant lacking the nuclear localization signal (NLS) on the ICP0 gene (0ΔNLS) is sensitive to inhibition by interferon beta (IFN-β) in vitro and functions as a highly efficacious experimental vaccine. Here, we characterize the host immune response and in vivo pathogenesis of HSV-1 0ΔNLS relative to its fully virulent parental strain in C57BL/6 mice. Additionally, we explore the role of type 1 interferon (IFN-α/β) signaling on virulence and immunogenicity of HSV-1 0ΔNLS and uncover a probable sex bias in the induction of IFN-α/β in the cornea during HSV-1 infection. Our data show that HSV-1 0ΔNLS lacks neurovirulence even in highly immunocompromised mice lacking the IFN-α/β receptor. These studies support the translational viability of the HSV-1 0ΔNLS vaccine strain by demonstrating that, while it is comparable to a virulent parental strain in terms of immunogenicity, HSV-1 0ΔNLS does not induce significant tissue pathology.IMPORTANCE HSV-1 is a common human pathogen associated with a variety of clinical presentations ranging in severity from periodic "cold sores" to lethal encephalitis. Despite the consistent failures of HSV subunit vaccines in clinical trials spanning the past 28 years, opposition to live-attenuated HSV vaccines predicated on unfounded safety concerns currently limits their widespread acceptance. Here, we demonstrate that a live-attenuated HSV-1 vaccine has great translational potential.

Sex differences in the response to influenza virus infection: modulation by stress

Influenza virus infection is a significant public health problem; however factors affecting the incidence and severity of disease have not been fully elucidated. The present study sought to examine the role of sex and stress in mediating susceptibility to an influenza viral infection in mice. Male and female mice underwent repeated cycles of restraint (RST) stress, followed by an influenza A/PR8 virus infection. Following these manipulations, levels of circulating corticosterone, lung proinflammatory cytokine gene expression and sickness behavior were examined. The data indicate sex differences in several aspects of the response to the A/PR8 virus infection. The kinetics of lung interleukin-1β mRNA expression were faster in infected males compared to females, while circulating corticosterone levels were elevated in infected females, but not in males. Anorexia and reduced saccharin consumption began earlier and symptoms were more pronounced in infected males than in females. In addition, RST modulated the response to the A/PR8 virus infection. Proinflammatory cytokine gene expression in response to infection was enhanced and sickness behavior was modulated by RST in both males and females. These data suggest that males mount more vigorous immune and behavioral responses to influenza viral infection compared to females, and stress exacerbates the response in both males and females. In conclusion, complex interactions between biological and behavioral factors are involved in mediating individual differences in health and disease. Additional studies may help uncover some of the factors contributing to the individual differences in susceptibility to influenza infection.

Estrogens augment cell surface TLR4 expression on murine macrophages and regulate sepsis susceptibility in vivo

Gender-based differences exist in infectious disease susceptibility. In general, females generate more robust and potentially protective humoral and cell-mediated immune responses after antigenic challenge than their male counterparts. Furthermore, evidence is accumulating that sex may also influence the early perception of microbial challenges and the generation of inflammatory immune responses such as sepsis. These differences have previously been attributed to the actions of reproductive hormones. Whereas androgens have been shown to suppress acute host immune responses to bacterial endotoxin challenge, estrogens have been found to promote increased resistance to bacterial infections. However, the mechanisms by which estrogens exert immunoprotective effects have not been established. In this study, we investigated the in vivo effects of 17beta-estradiol on endotoxin susceptibility in mice. Importantly, we have examined the actions of this female reproductive hormone on the expression of pattern recognition receptors that recognize bacterial endotoxin by key innate immune sentinel cells. We show that removal of endogenous estrogens decreases both pro- and antiinflammatory cytokine production, with a concomitant reduction in circulating levels of lipopolysaccharide-binding protein and cell surface expression of Toll-like receptor 4 on murine macrophages. Exogenous in vivo replacement of 17beta-estradiol, but not progesterone, significantly elevates sera lipopolysaccharide-binding protein levels and cell surface expression of Toll-like receptor 4 and CD14 on macrophages. Furthermore, this effect corresponds with significantly higher inflammatory cytokine levels after in vivo lipopolysaccharide challenge and a marked increase in endotoxin-associated morbidity. Taken together, these data provide a potential mechanism underlying the immunoenhancing effects of estrogens.

Testosterone reduces macrophage expression in the mouse of toll-like receptor 4, a trigger for inflammation and innate immunity

Though gender-based differences in the development of protective or pathological adaptive host responses have been widely noted, it is becoming apparent that sex may also influence the early perception of microbial challenges and the generation of inflammatory immune responses. These differences may be due to the actions of reproductive hormones, and such a hypothesis is supported by the presence of receptors for these hormones in a variety of immune cell types. Androgens such as testosterone have been shown to decrease immune functions, including cytokine production. However, the mechanisms by which testosterone limits such responses remain undefined. In this study, we have investigated the acute effects of testosterone on the level of expression of a key trigger for inflammation and innate immunity, Toll-like receptor 4 (TLR4), on isolated mouse macrophages. We show that in vitro testosterone treatment of macrophages, generated in the absence of androgen, elicits a modest but significant decrease in TLR4 expression and sensitivity to a TLR4-specific ligand. In addition, we have studied the effect of in vivo removal of endogenous testosterone on TLR4 expression and endotoxin susceptibility. We report that orchidectomized mice were significantly more susceptible to endotoxic shock and show that macrophages isolated from these animals have significantly higher TLR4 cell surface expression than those derived from sham gonadectomized mice. Importantly, these effects were not apparent in orchidectomized animals that received exogenous testosterone treatment. As such, these data may represent an important mechanism underlying the immunosuppressive effects of testosterone.

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.

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.

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.

Effect of prior exposure to herpes simplex virus 1 on viral vector-mediated tumor therapy in immunocompetent mice

Replication-competent, attenuated mutants of herpes simplex virus type 1 (HSV-1) have been shown to be efficacious for tumor therapy. However, these studies did not address the consequences of prior exposure to HSV, as will be the case with many patients likely to receive this therapy. Two strains of mice, A/J and BALB/c, were infected with wild-type HSV-1 by intraperitoneal injection and the immune response was determined by plaque reduction assay for neutralizing antibody and ELISA for IgG and IgM. Syngeneic tumors, N18 neuroblastoma and CT26 colon carcinoma, were implanted subcutaneously in HSV-1 seropositive and naive A/J and BALB/c mice, respectively. Established tumors were subsequently treated intratumorally with a multi-mutated HSV-1, G207. G207 inhibited tumor growth to a similar extent whether the mice were seropositive or not. We next examined the effect of multiple intratumoral inoculations of a 10-fold lower dose of G207 on tumor growth. In the multiple treatment group (biweekly for 3 weeks), 75% of tumors were cured, whereas no cures were seen in the single treatment group. We conclude that HSV seropositivity should not deleteriously affect the efficacy of G207 tumor therapy, and multiple inoculations of virus should be considered for clinical evaluation.

Innate and acquired immunity to herpes simplex virus type 1

Immunization with heat-inactivated herpes simplex virus type 1 (HSV-1) 2-5 days before ocular infection reduced the frequency of establishment of latent HSV-1 infection in the trigeminal ganglion (TG); this induction of resistance coincided with reduced expression of IFN-gamma mRNA in the TG. Immunization with unrelated antigens was not protective. In part, this resistance to nervous system invasion correlated with the appearance of serum antibody to HSV-1. Immunization reduced viral replication in the eye and trigeminal ganglion, and prevented HSV-1 spread to the cerebellum. IFN-gamma was detected in immunized mice 4 days postocular infection as determined by plaque reduction using neutralizing Ab to IFN-alpha/beta and IFN-gamma. Injection of antibody (Ab) to IFN-alpha/beta and IFN-gamma administered at the time of immunization did not affect survival. Anti-IFN-gamma-treated mice had significantly reduced levels of IFN in their serum. Treatment with anti-IFN-alpha/beta Ab resulted in an elevation in viral replication as determined by the expression of latency associated transcripts in the TG of mice. Likewise, there was a significant increase in the CD8, IL-12 (p40), and TNF-alpha mRNA levels in the TG of the anti-IFN-alpha/beta-treated mice TG explant cultures demonstrated that viral load was significantly increased in the TG of anti-IFN-alpha/beta-treated mice relative to TG of control mice 7 days after infection. The results suggest that exposure to viral antigens 2-5 days before infection is an important determinant of the extent of HSV-1 spread to the nervous system. Moreover, the data suggest that both an antibody response and IFN-alpha/beta play a role in limiting the progress of infection from the peripheral tissues to the central nervous system.

Contrasting effects of immunosuppression on herpes simplex virus type I (HSV I) induced central nervous system (CNS) demyelination in mice

We previously reported that lip inoculation of Herpes simplex virus type I (HSV I) in specific strains of mice would induce multifocal brain demyelination (MBD). The mechanisms mediating the development of MBD are unknown. In this study, five inbred strains of mice (C57BL/6J, Balb/cByJ, A/J, SJL/J, PL/J) immunosuppressed with either irradiation (IR), cyclophosphamide (CY), or cyclosporin A (CP) along with three immune deficient strains (C57BL/6J nu/nu, Balb/cByJ nu/nu, C57BL/6J bg/bg) were lip inoculated with HSV I to determine the effect of immunosuppression on viral spread throughout the brain and the development of demyelination during the acute stage of infection. Mortality increased in all groups when compared with controls but was greatest in A/J, SJL/J, and PL/J strains, where all mice died before day 6 PI. In contrast with immunocompetent C57BL/6J mice where virus is restricted to the brainstem, virus spread throughout the brain of immunosuppressed C57BL/6J, C57BL/6J nu/nu, and C57BL/6J bg/bg mice. Despite viral spread throughout the brain of immunosuppressed C57BL/6J, C57BL/6J nu/nu, Balb/cByJ and Balb/cByJ nu/nu mice, MBD did not develop. MBD did develop however, in both HSV I infected C57BL/6J bg/bg and CP treated Balb/cByJ mice. Immunosuppression of HSV I infected Balb/cByJ mice prevents the development of demyelination at the trigeminal root entry zone (TREZ) of the brainstem while in Balb/cByJ nu/nu mice, the extent of demyelination at TREZ was reduced and delayed when compared with immunocompetent controls. These results suggest that the immune system plays an important role in limiting viral spread in the brain as well as in the development of demyelination at TREZ and of MBD throughout the brain during the acute phase of infection. Virus alone does not induce MBD in this animal model of virus induced CNS demyelination but is a prerequisite for its development.

Pathogenesis of HSV-1/2 induced vaginitis/vulvitis of the mouse: dependence of lesions on genetic properties of the virus and analysis of pathohistology

A scoring system for herpes simplex virus (HSV) induced vaginitis/vulvitis in Balb/c mice was delineated from vaginal infections. Four degrees of vaginitis/vulvitis could be distinguished after infection with suitable strains of HSV despite nearly identical replication rates. The time course of replication, inflammation and pathohistology was compared further. Grade 0 was defined by lack of symptoms despite presence of strong replication, which was detectable at days 3-6. Focal necrotic lesions of the epithelial layer were present containing HSV-specific antigens. DNA could be detected by hybridization only in the outer zone of these areas. At day 6 these zones began to be re-epithelialized. In the vaginal lumen abundant detached epithelial cells and granulocytes were already present by day 2. Grade 1 was macroscopically characterized by a slight inflammation commencing on days 5-6. Replication and antigens in the epithelium were found on days 2-6. HSV-antigens were only detected above the basal membrane, and some infiltration with granulocytes and lymphocytes was observed below the basal membrane at day 4. Grade 2 showed strong redness and inflammation as well as hyperemia. Cellular infiltrates were present in the large antigen containing epithelial lesions and below the basal membrane. From day 4 on, neurons were HSV-antigen and DNA positive and macrophages in the stroma contained antigen. The vulva was also shown to be involved. Grade 3 exhibited prolonged severe hyperemia, and destruction of the epithelium and the stroma with necrosis and infiltration, especially of the vulva. This grading system was shown to depend on certain unknown genetic properties of HSV-strains. Neither thymidine-kinase activity, replication in macrophages, fusion activity of strains nor presence or absence of the Hpa I P-fragment were shown to be of importance for severity of vaginitis/vulvitis. Vaginitis/vulvitis was shown to be an all or none response to HSV independent of the rate of replication. The set of virus genes responsible for neuroinvasiveness after vaginal or i.p. inoculation was found to be different. The time course of replication (mainly days 3-6) and inflammation (days 5-10) indicates that inflammation seems to be a secondary immunological phenomenon induced later by the replication phase of HSV. Our system could be useful for separately testing drugs with antiviral and anti-inflammatory properties.

Vaginal infection of mice with HSV type 2 variant ER-: a new animal model for human primary genital HSV type 2 infections

Studying the pathogenesis of vaginal infections in mice with two variants of Herpes simplex virus type 2 (HSV-2) strain ER we observed that both variants ER+ and ER- caused severe vaginitis but only ER+ invaded the CNS leading to lethal neurological disease. In contrast, mice infected with ER- cleared the virus from the vagina and recovered from infection. ER+ and ER- expressed equal levels of thymidine kinase (TK) indicating a TK-independent difference in neurovirulence. Using the non-neurovirulent variant ER-, we were able to investigate humoral immune responses later after infection. Vaginal infection with ER- suppressed serum antibody formation after a secondary systemic HSV-1 infection. Fresh isolates of HSV-1 and HSV-2 caused uniformly a lethal neurological disease after vaginal inoculation of mice. However, some animals survived an intraperitoneal infection with these isolates. Infection with HSV-1 isolates stimulated a strong antibody production, whereas infection with HSV-2 isolates suppressed antibody formation, thus supporting earlier results from our group obtained with laboratory strains. Since suppression of antibody formation could be demonstrated with clinical HSV-2 isolates and likewise after vaginal infection with HSV-2 variant ER- we consider this phenomenon to be of relevance in human genital HSV-2 infections. Vaginal infection of mice with variant ER- represents a new model for primary genital HSV-2 infections; this model could be useful for histopathological, virological, immunological and drug testing studies.

Colonization of adrenal glands and ovaries of mice by variants of HSV 1 and 2. II. Histopathological, immunohistochemical and in situ hybridization studies

The herpes simplex virus (HSV)-infected mouse model was used to correlate histopathological lesions in adrenal glands and ovaries with the localisation of viral nucleic acids and viral antigens, employing in situ hybridization and immunohistochemistry. In the adrenals, the lesions were mainly restricted to the zona fasciculata and the zona reticularis, sometimes extending to the medulla. In the ovaries, lesions were detected in follicles and in the stroma. During the course of infection, HSV nucleic acids could be detected earlier than HSV proteins. Next to the center of necrotic foci mainly HSV proteins were detected, whereas peripheral cells were found to contain viral nucleic acids. In situ hybridization revealed no proof of HSV latency in either organ. Among HSV-1 and HSV-2 strains of different neurovirulence, only HSV-2 variant ER- failed to replicate in adrenal glands and ovaries, whereas the neuroinvasive variant ER+ showed the same patterns as the HSV-1 strains used.

HSV hepatitis in the mouse: a light and electron microscopic study with immunohistology and in situ hybridization

In order to characterize better the morphology and immune response in acute necrotizing HSV infection, murine HSV hepatitis was examined. BALB/c mice were inoculated intraperitoneally with 10(6) plaque-forming units (PFU) of HSV-1 (Lenette) and HSV-2 (D316). In both groups half the animals were pretreated with silica particles to block macrophage function. Up to 6 days after infection four mice from each group were sacrificed at daily intervals and the livers were examined by light and electron microscopy, immunohistology, in situ hybridization, combined immunohistology/in situ hybridization and titration of viral PFU. HSV-2 infected mice developed severe necrotizing hepatitis with persistence of HSV in the liver tissue until the end of the study. HSV-1 infected mice rapidly eliminated the virus and revealed only small necrotic foci. Early phase alterations and necrotic phase lesions were distinguished and characterized and morphologic evidence of a direct cytopathic effect of HSV was detected. A specific immune reaction in late stages appeared to be mediated by T4-positive T-lymphocytes. In situ hybridization and immunohistochemistry showed a close correlation with virus titration and were valuable in characterizing early phases and in the assessment of prognosis and differential diagnosis.

The quest for a herpes simplex virus vaccine: background and recent developments

Herpes simplex virus infections in humans range from localized skin infections of the oral, ocular and genital regions, to severe and often fatal disseminated infections of immunocompromised hosts. Following primary infection, the virus often becomes established in a latent form in the neurons of sensory ganglia and can reactivate to excrete virus asymptomatically or produce recrudescent lesions. This review describes some of the mechanisms involved in the immune response against HSV infections and examines the different strategies adopted to develop a vaccine against this seemingly intractable disease.

Herpes simplex virus-enhanced production of autoantibodies against myelin basic protein in mice

In 5 per cent of untreated and apparently healthy Swiss albino mice antibodies were demonstrable against myelin basic protein (MBP) prepared from human brain tissue. Associated with infection with herpes simplex virus (HSV) type 1, enhancement of the antibody formation against MBP was encountered. Thus of infected but symptom-free animals 15-25 per cent revealed anti-MBP antibodies. The latter type of antibodies appeared later than antibodies against HSV and were found predominantly in animals inoculated via the intraperitoneal route. No signs of demyelination in spinal cords or spinal nerve roots were observed in MBP antibody-positive HSV-immunized animals. Results reported may indicate triggering of an autoantibody formation against MBP and are discussed in relation to demyelinating disease.

Replication of HSV-1 in murine peritoneal macrophages: comparison of various virus strains with different properties

The in vitro replication of eleven different strains of herpes simplex virus type 1 was studied in resident or thioglycollate-stimulated mouse macrophages. The strains of herpes simplex virus differed in the type of cytopathic effect, induction capacity for herpes simplex virus coded thymidine kinase and pathogenicity in the mouse. Herpes simplex virus replicated better in thioglycollate-stimulated macrophages than in resident macrophages. In vitro ageing of macrophages increased their replicative potency. Herpes simplex virus replicated better in macrophages from homozygous bg/bg C57/BL6J mice than in macrophages from their heterozygous littermates. Separation of macrophages on discontinuous Percoll-gradients revealed 4 fractions with identical potency for replication. The ability of herpesvirus to replicate in macrophages varied from strain to strain of virus i.e. Wal greater than Len, clone 4 of Len, greater than L3-2s, JES, Ang-, Ang + path, clone 2 of Len and greater than MDK clones. The ability to cause cytopathology also varied. Only strains Ang- and Ang + path showed limited or late cytopathology in macrophages. The cell-fusing property of herpes simplex virus appeared to be more closely correlated with lower replication rates than production cell rounding. Thymidine kinase- viruses replicated less well than thymidine kinase+ or thymidine kinase(+) strains. Strains of herpes simplex virus with high or low pathogenicity for mice replicated in macrophages to the same degree. The phagocytic activity of macrophages for IgM-coated sheep red blood cells was inhibited earlier by strains of herpes simplex virus of type 2 than by strains of herpes simplex virus of type 1.