Genetics of macrophage-controlled resistance to hepatitis induced by herpes simplex virus type 2 in mice.

The genetics of innate resistance of mice to hepatitis induced by herpes simplex virus type 2 (HSV-2) was analyzed by crossing resistant male GR to susceptible female BALB/c mice and backcrossing females of this F1 generation to susceptible male BALB/c mice. By scoring of macroscopic liver lesions and virus isolation studies from the liver 4 days after intraperitoneal inoculation of HSV-2, it appeared that the resistance was governed by one X-linked dominant gene or closely linked gene complex, as F1 female mice were resistant and F1 male mice were susceptible and the trait segregated in a ratio close to 1:1 in the backcross mating. A cellular expression in vitro of virus resistance was found in the macrophage population of the mice as measured by differences in the restriction of HSV-2 replication in macrophage cultures prepared from individual mice. In contrast to what was seen in macrophage cultures, virus replicated equally well in embryonic fibroblast cultures from susceptible and resistant strains of mice.     

Macrophages and age-dependent resistance to hepatitis induced by herpes simplex virus type 2 im mice.

An age-dependent increase in the resistance of BALB/c mice to induction of focal necrotic hepatitis by herpes simplex virus type 2 was demonstrated. In 3-week-old mice inoculated intraperitoneally with virus, numerous necrotic foci developed in the liver. As the mice matured, the number of lesions declined until the age of 8 weeks, when no further increase in resistance appeared. Corresponding to this, the virus titers of livers and spleens of 3-week-old mice were higher than in 8-week-old animals throughout the infection, and the infection was apparently terminated in these organs of the adult mice by day 5. In vitro infection of peritoneal macrophages from 3-week-old and 8-week-old mice showed that this age-related resistance was concomitant with an increased restriction of virus replication in peritoneal macrophages from adult mice. Since, furthermore, the resistance of adult mice could be abolished by intravenous inoculation of the macrophage-toxic agent silica before infection, and since adoptive transfer of 2 X 10(6) syngeneic macrophages from adult mice to young ones conferred to the latter a resistance comparable to that of the adult mice, it is concluded that macrophage maturation is responsible for the age-dependent resistance seen in this infection.     

Role of macrophages in hepatitis induced by Herpes simplex virus types 1 and 2 in mice.

A marked difference was found between herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) in the induction of hepatic necrotic lesions in mice inoculated intraperitoneally. Although HSV-2 produced many large, progressive liver lesions in 4-week-old BALB/c mice, HSV-1 only occasionally induced a few, self-limiting foci, which eventually healed. This was reflected in the isolation of HSV from the liver and spleen, two organs that are rich in macrophages. Although HSV-1 could be only temporarily isolated, HSV-2 was found in the two organs until the mice died. On the other hand, no such difference was found in the isolation of virus from the brain, which contains no macrophages, and the mice eventually died from encephalitis. This difference in hepatic involvement caused by the two virus types was found to parallel a marked difference in the restriction of HSV-1 and HSV-2 replication by macrophages as measured by an infectious center assay in vitro. HSV-2 produced 17 times as many infectious centers in infected peritoneal macrophage cultures as did HSV-1. Furthermore, the HSV-2 plaques in the cell overlay were large and increasing in size, whereas the HSV-1 plaques were small and showed regression on prolonged incubation. It was shown that this diversity was unique to the macrophage population and not caused by differences in the uptake of virus by macrophages. This model involving two closely related virus types shows the importance of tissue macrophages in the primary host defense against virus infections.     

Experimental Q fever infection in congenitally athymic nude mice.

Congenitally athymic nude (nu/nu) mice and their phenotypically normal (nu/+) euthymic littermates were exposed to Coxiella burnetii administered as small-particle aerosols. After challenge, both strains of mice became infected, as characterized by rickettsemia, viable rickettsiae in the spleen, and serological conversion. The major difference noted was that euthymic animals had cleared rickettsiae from peripheral circulation and the spleen within 14 days. In contrast, rickettsiae were detected and isolated from spleen and blood of athymic mice through 60 days.     

Chronic chlamydial genital infection in congenitally athymic nude mice.

Congenitally athymic nude mice and their heterozygous counterparts were inoculated intravaginally with the chlamydial agent of mouse pneumonitis, a Chlamydia trachomatis biovar. Heterozygous mice resolved their infections in 20 days, whereas nude mice developed chronic infections which lasted at least 265 days and did not resolve within the time course of the experiments. Heterozygous mice produced high levels of antibody in both serum and secretions in contrast to nude mice, which produced very low levels of antibody in serum alone.     

Immune responses to Rickettsia akari infection in congenitally athymic nude mice.

Athymic BALB/c nude mice and euthymic BALB/c mice were infected with Rickettsia akari by the intraperitoneal route. The rickettsialpox infection was terminated in euthymic mice with only two intraperitoneal injections of the antibiotic oxytetracycline, whereas prolonged treatment was necessary to terminate the infection in athymic mice. Both athymic and euthymic mice produced specific antibody, but athymic mice were still susceptible to reinfection. Killed R. akari served as a protective immunogen in euthymic, but no in athymic, mice. When spleen cells from convalescent euthymic mice were transferred to syngeneic athymic mice, recipients showed protection against challenge. This suggests that a T-cell-dependent step is generally necessary to terminate the rickettsialpox infection.     

Tumor-dependent resistance of rat peritoneal macrophages to herpes simplex virus.

By their position at sites of initial infection and their wide distribution in major organs of the body, macrophages may be decisive in determining the susceptibility or resistance of the host to virus infection. Macrophage restriction of virus replication has been shown to be closely related to virus strains or virus types and to the age of the infected host. We report the effects of the development of a solid tumor in rats on intrinsic in vitro macrophage activity against herpes simplex virus type 1. The results obtained with the infectious center assays and the analysis of single-cycle growth curves of herpes simplex virus type 1 in macrophages obtained from normal and tumor-bearing rats showed a depression of antiviral activity of macrophages from tumor-bearing rats. The possibility of immunomodulation by bacterial adjuvants on tumor-bearing rats and the effects on the antiviral activity of peritoneal macrophages were furthermore demonstrated.     

Age-dependent resistance of human alveolar macrophages to herpes simplex virus.

Studies in mice demonstrate an age-dependent susceptibility to disseminated herpesvirus infection which is mediated. at least in part, by a defect in macrophage antiviral function. We examined the growth of herpes simplex virus within human alveolar macrophages obtained by bronchopulmonary lavage from neonates, adults with a variety of immunosuppressive disorders, and healthy adult volunteers. At 24 h postinfection, mean viral titers in neonatal macrophages increased 19-fold over adsorbed virus levels, a highly significant increase when compared to either immunosuppressed or normal adult macrophages (P less than 0.0005). These findings indicate that human macrophages, like those of mice, exhibit age-dependent permissiveness for the replication of herpes simplex virus. This permissiveness may at least partially account for the clinical observation that human newborns are highly susceptible to disseminated herpes simplex virus infections, whereas adults are not.     

Susceptibility of congenitally athymic (nude) mice to sporotrichosis

Congenitally athymic (nu/nu) mice were found to be more susceptible to intravenous challenge with Sporothrix schenckii than their phenotypically normal (nu/+) littermates as measured by lethality and the number of viable yeast cells in the liver 7 days postinfection. Thymus reconstitution of nu/nu mice (nu/thy) conferred a significant degree of resistance to sporotrichosis. Immunization greatly enhanced the resistance of nu/thy and nu/+ mice, but unexpectedly increased the susceptibility of nu/nu mice. The susceptibility of nonimmunized nu/nu mice and the finding that thymus transplants augmented resistance to sporotrichosis suggest that T lymphocytes are critical to host defense.     

Chronic infection with Trypanosoma musculi in congenitally athymic nude mice.

Trypanosoma musculi produces a chronic infection with a consistently elevated parasitemia in nude mice. Thymic reconstitution of nude mice restores immunity to the infection.     

Persistent Cryptosporidium infection in congenitally athymic (nude) mice.

Nude (nu/nu) BALB/c mice and their white (nu/+) littermates were experimentally infected with Cryptosporidium sp. at 6 days of age. In white mice, the infection was transient, but in nude mice a persistent infection developed that was characterized by diarrhea and, occasionally, death. There were villus atrophy and crypt hyperplasia in the small intestine of infected nude and white mice necropsied at 11 days of age. Persistently infected nude mice had, in addition to the above small intestinal lesions, diffuse cystic mucosal hyperplasia and crypt abscesses in the large intestine at 56 days of age. These results suggest that T cells are required for recovery from the Cryptosporidium infection but are not required for epithelial cell loss in cryptosporidiosis. Both nude and white mice appeared to be relatively more resistant to Cryptosporidium infection at 42 days of age than at 6 days of age.     

The role of gamma interferon in immune resistance to vaginal infection by herpes simplex virus type 2 in mice.

We investigated the role of interferon gamma (IFN-gamma) in a mouse model of immunity to vaginal infection by herpes simplex virus type 2 (HSV-2). Within 8 h after immune mice were challenged intravaginally with HSV-2, IFN-gamma concentrations in vaginal secretions reached levels that can be antiviral in vitro. This rapid synthesis of IFN-gamma occurred in immune-challenged mice but not in nonimmune-challenged mice, indicating that it required memory T cells. Immunostaining and in situ hybridization revealed that the IFN-gamma was synthesized by cells whose morphological appearance suggested that they were lymphocytes and macrophage-like cells in the mucosa. The presence of IFN-gamma in vaginal secretions was correlated with upregulation of MHC class II antigens in the epithelium and with vigorous (30-fold) recruitment of T and B lymphocytes into the vagina. In vivo administration of anti-IFN-gamma to immune mice 17 h before virus challenge blocked the subsequent appearance of IFN-gamma in vaginal secretions, blocked upregulation of class II antigens, blocked adherence of T cells to endothelium and their recruitment into the vagina, and markedly reduced immunity against reinfection of the vaginal epithelium.     

Efficacy of herpes simplex virus type 1 immunization in protecting against acute and latent infection by herpes simplex virus type 2 in mice.

ICR mice were immunized with herpes simplex virus type 1 (HSV-1) and later challenged with HSV-2 by footpad inoculation. Both immunized animals and age-matched, nonimmunized controls were observed for ascending neurological disease and latent infection of spinal ganglia resulting from the HSV-2 challenge. Control animals had a 78% incidence of acute and latent infection compared with a 1.7% incidence in immunized mice. The data show immunity to HSV-1 is protective against both acute and latent infection by HSV-2.     

Replication of herpes simplex virus type 1 in macrophages from resistant and susceptible mice.

Studies were carried out to determine whether the in vitro capacity of adherent peritoneal cells to replicate herpes simplex virus type 1 (HSV-1) might correlate with the in vivo susceptibility of mice genetically resistant, moderately susceptible, or very susceptible to HSV-1 infection. Unstimulated and proteose peptone-stimulated monolayers restricted viral replication when infected immediately, but replicated HSV-1 when infected after 3 to 7 days of culture. Macrophages from resistant C57Bl/6 mice restricted HSV-1 replication significantly better than cells from susceptible mice. This function did not segregate with resistance, since macrophages from resistant F1 mice failed to restrict HSV-1 replication. Induction of peritoneal exudate cells with thioglycolate yielded cells capable of replicating HSV-1 when infected immediately after plating and after 4 days of culture.     

Role for cell-mediated immunity in the resistance of mice to subcutaneous herpes simplex virus infection.

The role of cell-mediated immunity in the resistance of young adult mice to subcutaneous herpes simplex virus (HSV) type I infection was studied in mice receiving immunosuppressive doses of antilymphocyte sera (ALS) or antithymocyte sera (ATS). The effectiveness of these treatments to reduce cell-mediated responses was measured by their ability to prolong the life of allografts transplanted to ALS- or ATS-treated mice. It was found that subcutaneous infection of these mice with HSV resulted in spread of virus from the site of inoculation to the central nervous system. Neutralizing antibody could not be detected in the sera of ALS- or ATS-treated mice after HSV inoculation. Passive transfer of neutralizing antibody to ATS-treated mice did not restore resistance to subcutaneous HSV infection. However, adoptive transfer of HSV-sensitized spleen cells did provide significant protection against infection unless the spleen cells were treated with ATS prior to transfer. These experiments suggest that lymphocytes are involved in a cell-mediated response to subcutaneous HSV infection and demonstrate the importance of a noncompromised immune response in controlling spread of HSV from localized areas of infection.     

Intrinsic resistance to herpes simplex virus type 1 infection in liver Kupffer cells and peritoneal macrophages from normal and immunomodulator-treated mice.

In contrast with other macrophage (MO) populations, there is little information on the antiviral resistance in vitro of isolated liver MO (Kupffer cells, KC). We have demonstrated that the KC exhibits marked intrinsic resistance to infection in vitro with herpes simplex virus type 1 (HSV-1). Liver and peritoneal MO (PMO) were harvested from untreated mice (naive), from mice treated with drug vehicle, or from mice treated with either a synthetic nonspecific immunomodulator, maleic anhydride divinyl ether copolymer (MVE-2), or with MO colony-stimulating factor-1 (CSF-1). The studies revealed that resident KC, isolated by two different methods, are equally as nonpermissive for infection with HSV-1 as are resident PMO. When infected with HSV-1, resident KC showed no cytopathic effect, and no infectious virus was produced. Intravenous (i.v.) treatment of mice with MVE-2 (50 mg/kg 3 days before cell harvest) increased the number of KC recovered. However, neither i.v. treatment with MVE-2 nor CSF-1 (20,000 U daily for 4 days) had any pronounced effect on the permissiveness of KC or PMO to infection with HSV-1. These data support a role for KC in host antiviral resistance, and indicate that KC intrinsic antiviral resistance is maintained during immunotherapy with MVE-2 or CSF-1.     

Thromboplastic and fibrinolytic activities in various organs of congenitally athymic nude mice.

Thromboplastic and fibrinolytic activities in various organs of congenitally athymic nude mice were estimated. These activities varied from one organ to another and the organs were divided into six groups of possible combinations of these activities. The lung revealed high thromboplastic and high fibrinolytic activities, while the liver showed low thromboplastic and low fibrinolytic activities. The pattern of distribution of these activities in various organs of nude mice was almost similar to that of rats and mice with normal thymus. No plasmin activity was found in all organs.     

X-linked resistance of mice to high doses of herpes simplex virus type 2 correlates with early interferon production.

Mice inoculated intraperitoneally with herpes simplex virus type 2 develop focal necrotizing hepatitis and eventually die from ascending myelitis and encephalitis. The genetics of resistance to the infection were analyzed in crosses between resistant C57BL/10 mice and susceptible BALB/c mice. It was shown that the resistance of C57BL/10 mice to hepatitis induction was influenced by an X-linked dominant gene as previously shown for the GR mouse strain. The course of infection in the liver pointed to early, natural defense mechanisms as being responsible for the difference between the mouse strains, whereas the clearance of virus from the liver, probably mediated by specific immunity, was exerted at the same time and with equal efficiency for all groups of mice. In mortality experiments, resistance was shown to be an autointerference phenomenon in that a considerable number of C57BL/10 mice survived an intraperitoneal injection of 10(6) PFU, whereas all mice were killed by 10(5) PFU. This resistance of C57BL/10 mice to high doses of HSV-2 was retrieved in all groups of F1 mice in crosses between C57BL/10 and BALB/c mice except the (BALB/c female X C57 male) male group, in which the mice receive the X chromosome from the susceptible BALB/c female. Thus, the autointerference phenomenon also seems to be influenced by loci on the X chromosome. A similar pattern of inheritance was observed when early interferon induction (4 to 5 h after infection) in response to HSV-2 was measured. The possible relevance of this early interferon response in conjunction with other potential natural defense mechanisms is discussed.