Virus-cell interactions regulating induction of tumor necrosis factor alpha production in macrophages infected with herpes simplex virus

Macrophages respond to virus infections by rapidly secreting proinflammatory cytokines, which play an important role in the first line of defense. Tumor necrosis factor alpha (TNF-alpha) is one of the major macrophage-produced cytokines. In this study we have investigated the virus-cell interactions responsible for induction of TNF-alpha expression in herpes simplex virus (HSV)-infected macrophages. Both HSV type 1 (HSV-1) and HSV-2 induced TNF-alpha expression in macrophages activated with gamma interferon (IFN-gamma). This induction was to some extent sensitive to UV treatment of the virus. Virus particles unable to enter the cells displayed reduced capacity to stimulate TNF-alpha expression but retained a significant portion which was abolished by HSV-specific antibodies. Recombinant HSV-1 glycoprotein D was able to trigger TNF-alpha secretion in concert with IFN-gamma. Sugar moieties of HSV glycoproteins have been reported to be involved in induction of IFN-alpha but did not contribute to TNF-alpha expression in macrophages. Moreover, the entry-dependent portion of the TNF-alpha induction was investigated with HSV-1 mutants and found to be independent of the tegument proteins VP16 and UL13 and partly dependent on nuclear translocation of the viral DNA. Finally, we found that macrophages expressing an inactive mutant of the double-stranded RNA (dsRNA)-activated protein kinase (PKR) produced less TNF-alpha in response to infectious HSV infection than the empty-vector control cell line but displayed the same responsiveness to UV-inactivated virus. These results indicate that HSV induces TNF-alpha expression in macrophages through mechanisms involving (i) viral glycoproteins, (ii) early postentry events occurring prior to nuclear translocation of viral DNA, and (iii) viral dsRNA-PKR.

Expression of TNF-alpha by herpes simplex virus-infected macrophages is regulated by a dual mechanism: transcriptional regulation by NF-kappa B and activating transcription factor 2/Jun and translational regulation through the AU-rich region of the 3' untranslated region

Here we have investigated the regulation of TNF-alpha expression in macrophages during HSV-2 infection. Despite a low basal level of TNF-alpha mRNA present in resting macrophages, no TNF-alpha protein is detectable. HSV-2 infection marginally increases the level of TNF-alpha mRNA and protein in resting macrophages, whereas a strong increase is observed in IFN-gamma-activated cells infected with the virus. By reporter gene assay it was found that HSV infection augments TNF-alpha promoter activity. Moreover, treatment of the cells with actinomycin D, which totally blocked mRNA synthesis, only partially prevented accumulation of TNF-alpha protein, indicating that the infection lifts a block on translation of TNF-alpha mRNA. EMSA analysis showed that specific binding to the kappaB#3 site of the murine TNF-alpha promoter was induced within 1 h after infection and persisted beyond 5 h where TNF-alpha expression is down-modulated. Binding to the cAMP responsive element site was also induced but more transiently with kinetics closely following activation of the TNF-alpha promoter. Inhibitors against either NF-kappaB activation or the activating transcription factor 2 kinase p38 abrogated TNF-alpha expression, showing a requirement for both signals for activation of the promoter. This observation was corroborated by reporter gene assays. As to the translational regulation of TNF-alpha, the AU-rich sequence in the 3' untranslated region of the mRNA was found to be responsible for this control because deletion of this region renders mRNA constitutively translationable. These results show that TNF-alpha production is induced by HSV-2 in macrophages through both transcriptional and translational regulation.

CD4+ CD8+ (thymocyte-like) T lymphocytes present in blood and skin from patients with atopic dermatitis suggest immune dysregulation

BACKGROUND

Atopic dermatitis (AD) is a chronic inflammatory skin disease expressed early in life. Disease development is primarily determined by as yet unknown genetic factors, leading to the accumulation of activated T lymphocytes in the skin.

OBJECTIVES

To investigate the nature of these T cells.

METHODS

T-cell lines could be established from AD skin biopsies, but not from normal skin or AD peripheral blood, when placed in RPMI 1640 medium with 10% human AB serum, antibiotics, and the T-lymphocyte growth factors interleukins 2 and 4. The cell lines were subjected to phenotypic analysis using a fluorescence-activated cell sorter and compared with lymphocytes from AD and normal control peripheral blood.

RESULTS

T-cell lines from 22 of 24 consecutive skin biopsies taken from 24 adult patients with AD were established. All cells were T lymphocytes expressing several activation markers. A significant proportion of the lymphocytes had stable expression of a CD4+ CD8+ phenotype (26% +/- 6%; mean +/- SEM). Such double-positive T lymphocytes are normally only seen in the thymus and not in the peripheral immune system. CD4+ CD8+ cells in peripheral blood of the patients (12.5% +/- 3.3%) were also detected.

CONCLUSIONS

We suggest that a basic pathophysiological change in AD may be a faulty maturation of the T-lymphocyte system, leading to skin inflammation with CD4+ CD8+ T lymphocytes resembling immature T cells. This is likely to lead to skewing of many immune reactions in the patients.

Interferon (IFN)-gamma and Herpes simplex virus/tumor necrosis factor-alpha synergistically induce nitric oxide synthase 2 in macrophages through cooperative action of nuclear factor-kappa B and IFN regulatory factor-1

The radical nitric oxide (NO) constitutes an important part of the innate immune response to many viruses, and among these notably Herpes simplex virus (HSV). We have previously shown that HSV/tumor necrosis factor-alpha (TNF-alpha) and IFN-gamma synergistically induce NO production in macrophages, and here we have investigated the molecular mechanism underlying this phenomenon. The enhancement of NO production was regulated at the level of NO synthase 2 (NOS2, iNOS) transcription. The ISRE element of the NOS2 promoter, which binds IFN regulatory factor (IRF)-1, was essential both for full responsiveness to IFN-gamma and the synergistic response. The GAS motif, binding signal transducer and activator of transcription 1 (STAT1), did not contribute to the cross-talk with virus/TNF-induced signals, but was necessary for full responsiveness to IFN-gamma. The distal binding site for nuclear factor (NF)-kappa B was important for the cooperative response, while the proximal kappa B site was not involved in the cooperative promoter activation but played a role in full promoter inducibility. By ectopic expression of IRF-1 and NF-kappa B (p65), we found that these factors synergistically induce NO accumulation. Together, our results show that binding of IRF-1 and NF-kappa B to their respective sites in the distal domain of the NOS2 promoter, creates a potent trans-activating complex with the ability to induce NOS2 transcription synergistically in response to simultaneous HSV-2/TNF-alpha and IFN-gamma treatment.

The impact of CMV on the respiratory burst of macrophages in response to Pneumocystis carinii

Infection of human monocyte-derived macrophages with CMV decreased the respiratory burst when cells were stimulated with opsonized zymosan or Pneumocystis carinii (P. carinii). Such an effect, though smaller, was also seen with heat-inactivated CMV, but only when triggered by zymosan. The effect was most pronounced in cells obtained from CMV antibody-negative donors. Dexamethasone further reduced the respiratory burst, both in uninfected and CMV-infected cells. Interferon-gamma increased the response in uninfected cells and, to a lesser extend, in cells treated with heat-inactivated CMV, whereas no effect was seen with infective CMV. No overt productive infection or cytopathology could be detected, however, the monocytes incubated with infective but also heat-inactivated CMV formed clusters, a phenomenon that was equally pronounced in cultures from CMV antibody positive and negative-donors. These results might help explain the worse prognosis of P. carinii pneumonia in patients coinfected with CMV and receiving dexamethasone.

Inhibition of NO production in macrophages by IL-13 is counteracted by Herpes simplex virus infection through tumor necrosis factor-alpha-induced activation of NK-kappa B

Interleukin (IL)-13 is known to antagonize many interferon (IFN)-gamma-activated functions in macrophages and among these, nitric oxide (NO) production. We have previously shown that this function of IL-13 is reduced in Herpes simplex virus type 2 (HSV-2)-infected macrophages. In the present study we show that IL-13 and IFN-gamma are indeed produced during infection of BALB/c mice with HSV-2. The lack of inhibitory function of IL-13 in infected macrophages, which was not overcome even at very high concentrations of IL-13, was not due to impaired IL-13 signalling, since virus infection did not affect IL-13-mediated activation of STAT6 (signal transducer and activator of transcription 6). Neutralizing tumour necrosis factor (TNF)-alpha antibodies, however, largely restored the effect of IL-13 on NO production in virus-infected macrophages. The same was observed after treatment of the cells with inhibitors of nuclear factor (NF)-kappa B activation, known to be involved in enhancement of IFN-gamma-induced NO production. Even though IL-13 reduced TNF-alpha secretion by 50%, this did not impair NF-kappa B activation in IFN-gamma-treated cells infected with HSV-2. The results indicate that TNF-alpha, secreted by virus-infected macrophages, activates NF-kappa B which impairs the IL-13-mediated inhibition of inducible NO synthase (iNOS) expression. This could imply that a sustained NO production would be focused to sites of active virus replication.

Herpes simplex virus type 2 infection of macrophages impairs IL-4-mediated inhibition of NO production through TNF-alpha-induced activation of NF-kappaB

Nitric oxide (NO) production in macrophages by the interferon (IFN)-gamma-inducible NO synthase has been shown to play a role in clearance of viral infections. We have previously shown that IFN-gamma-induced NO production is augmented by herpes simplex virus type 2 (HSV-2) infection through autocrine tumour necrosis factor (TNF)-alpha secretion and is inhibited by interleukin (IL)-4. Here we investigated the effect of HSV-2 infection on the inhibitory function of IL-4. Virus infection of mouse J774A.1 macrophages strongly reduced the ability of IL-4 to inhibit IFN-gamma-induced NO production, even at very high IL-4 concentrations. The effect of HSV-2 infection did not involve the IL-4 signal transduction pathway through STAT6. IL-4 reduced virus-induced TNF-alpha secretion and nuclear factor (NF)-kappaB activation significantly, but less in cells concomitantly treated with IFN-gamma. Furthermore, neutralisation of residual TNF-alpha activity or inhibition of NF-kappaB activation largely restored the inhibitory effect of IL-4. The data show that inhibition of IFN-gamma-induced NO production by IL-4 is impaired by HSV-2 infection due to autocrine TNF-alpha-mediated NF-kappaB activation. We suggest that the described phenomenon might be beneficial for the host by limiting high and sustained NO production to infectious foci.

Interleukin-4-mediated inhibition of nitric oxide production in interferon-gamma-treated and virus-infected macrophages

Upon interferon-gamma (IFN-gamma) stimulation, murine macrophages (Mphi) produce nitric oxide (NO) through expression of inducible nitric oxide synthase (iNOS). Interleukin (IL)-4 treatment, even delayed 12 h relative to IFN-gamma, antagonized this induction, whereas infection with herpes simplex virus type 2 (HSV-2) or treatment with tumour necrosis factor-alpha exerted a synergistic effect, which partly compensated for the antagonistic effect of IL-4. Neither IL-4 nor HSV-2 affected the IFN-gamma-activated Jak-STAT (Janus kinase-signal transducer and activator of transcription) pathway or altered the levels of IFN-gamma-induced interferon regulatory factor (IRF)-1 expression, which is STAT1-dependent and known to play a central role in IFN-gamma-mediated gene induction. The effect of IL-4 was completely dependent on de novo protein synthesis, indicating that a direct activation of latent inhibitors is not sufficient to explain the inhibitory effect of IL-4. Furthermore, IL-4 substantially augmented the IFN-gamma-induced expression of IRF-2, which is known to compete with IRF-1 for the DNA recognition site, ISRE (interferon-stimulated response element). Our findings could indicate that IL-4 suppresses IFN-gamma-stimulated iNOS transcription by elevating the level of IRF-2 which, through competition, prevents IRF-1 from binding to ISRE in the iNOS promoter. The virus-induced effects on iNOS and NO levels in IFN-gamma-stimulated Mphi do not seem to involve the Jak/STAT pathway or a differential expression of IRF-1 and IRF-2.

NF-kappaB activation is responsible for the synergistic effect of herpes simplex virus type 2 infection on interferon-gamma-induced nitric oxide production in macrophages

Nitric oxide (NO), produced in interferon (IFN)-gamma-activated murine macrophages by the enzyme inducible nitric oxide synthase (iNOS), has been found to have antiviral properties. We have previously shown that herpes simplex virus type 2 (HSV-2) infection of macrophages synergistically enhances IFN-gamma-induced NO production, and we now extend these findings by providing evidence that virus-induced tumour necrosis factor (TNF)-alpha mediates activation of the transcription factor nuclear factor (NF)-kappaB, which in turn is responsible for the synergistic effect. HSV-2 infection and IFN-gamma stimulation of macrophages synergistically induced TNF-alpha secretion and nuclear translocation of NF-kappaB, which bound to a sequence corresponding to a kappaB site in the iNOS promoter. The effect of HSV-2 on NF-kappaB and NO production was eliminated when cells were treated with antibodies to TNF-alpha, and direct inhibition of NF-kappaB activation with pyrrolidinedithiocarbamate (PDTC) also blocked the effect of HSV-2 infection on NO production. The effect of the NF-kappaB activation inhibitor was not mediated through inhibition of the production of interferon regulatory factor (IRF)-1 or of TNF-alpha itself, and a possible alternative mechanism of activation of NF-kappaB through virus-induced activation of the kinase PKR was also ruled out. Thus, our data indicate that NF-kappaB activation, through virus-induced autocrine TNF-alpha secretion, is responsible for the synergistic effect of HSV-2 infection on IFN-gamma-induced NO production, and that such activation might constitute a mechanism by which high-output NO production is targeted to infectious foci.

Effect of IL-4 and IL-13 on IFN-gamma-induced production of nitric oxide in mouse macrophages infected with herpes simplex virus type 2

Interleukin (IL)-4 and IL-13 share a wide range of activities. Prominent among these is the ability to antagonize many interferon (IFN)-gamma-induced activities. Here we demonstrate that IL-4 and IL-13 totally abrogate IFN-gamma-induced nitric oxide (NO) production and inducible nitric oxide synthase (iNOS) mRNA and protein synthesis in a murine macrophage cell line. IFN-gamma-treated cells infected with herpes simplex virus type 2 (HSV-2) or costimulated with tumor necrosis factor (TNF)-alpha showed an enhanced reactivity, which was only partially reduced by IL-4/13. The results indicate that IL-4 and IL-13 function by intervening with a step prior to iNOS transcription by antagonizing IFN-gamma-induced signal(s) without counteracting synergistic virus- or TNF-alpha-induced signals. The beneficial effect of a sustained NO production in foci of virus infection is suggested.

Acyclovir prophylaxis and fever during remission-induction therapy of patients with acute myeloid leukemia: a randomized, double-blind, placebo-controlled trial

PURPOSE

A randomized, double-blind, placebo-controlled trial was performed to estimate the preventive effect of the antiherpetic drug acyclovir on fever, incidence of bacteremia, use of antibiotics, and presentation of infections in patients with acute myeloid leukemia (AML).

PATIENTS AND METHODS

Ninety herpes simplex virus (HSV)-seropositive patients aged 18 to 84 years were included. Forty-five patients received acyclovir (800 mg by mouth daily) and 45 placebo. The patients were examined daily for 28 days from the initiation of remission-induction chemotherapy.

RESULTS

Fever developed in all patients in both groups. Acyclovir prophylaxis postponed the development of an oral temperature > or = 38.0 degrees C by 3 days (95% confidence interval [CI], 1 to 4 days; P = .03) and the initiation of antibacterial treatment by 3 days (95% CI, 1 to 5 days; P = .008). The duration of fever, use of antibacterial treatment, incidence of bacteremia, and need for systemic antifungal therapy were not affected by acyclovir prophylaxis. At fever development, acyclovir prophylaxis affected the incidence and localization pattern of oral ulcers. Thus, in the acyclovir group, the number of nonfungal oral infections was reduced (relative risk, 0.45 [95% CI, 0.24 to 0.85]) and mainly located on the soft palate (relative risk, 2.49 [95% CI, 1.19 to 5.22]).

CONCLUSION

Acyclovir prophylaxis has an impact on fever development, but not on the duration of fever or the need for antibiotics. It does not reduce the incidence of bacteremia, but the presentation of acute oral infections is changed.

Herpes simplex virus type 2 synergizes with interferon-gamma in the induction of nitric oxide production in mouse macrophages through autocrine secretion of tumour necrosis factor-alpha

We have analysed the ability of herpes simplex virus type 2 (HSV-2) to induce nitric oxide (NO) production in resting BALB/c mouse peritoneal macrophages. In most experiments, macrophages produced very small amounts of NO upon infection with HSV-2. Mock virus preparations did not induce NO production, and virus inactivation experiments showed that infectious virus was required. Since interferon-gamma (IFN-gamma) is the prototype cytokine that is able to induce significant NO production in macrophages, we found it of interest to examine the influence of HSV-2 infection on the IFN-gamma-induced NO production. The virus exerted a synergistic effect on the IFN-gamma-induced NO release, which was accompanied by induction of the iNOS-gene as revealed by RT-PCR. This effect was largely dependent on the presence of infectious virus particles, since only a minor effect was seen with mock virus and inactivated virus preparations. From experiments with neutralizing antibodies to tumour necrosis factor-alpha (TNF-alpha) and IFN-alpha/beta it was concluded that the synergistic effect is dependent on autocrine secretion of TNF-alpha, which acts as a second signal and synergizes with IFN-gamma in NO production.

Influence of mercuric chloride on resistance to generalized infection with herpes simplex virus type 2 in mice

The effect of mercuric chloride on resistance to generalized infection with herpes simplex virus type 2 (HSV-2) in mice was studied. The severity of the infection was evaluated by the amount of infectious virus in the liver. Mercury at a single dose of 20 micrograms aggravated the infection, and neither increasing the single dose to 80 micrograms nor giving repeated doses of 20 micrograms further intensified the infection. Examination of the course of infection after mercury exposure revealed an increased virus replication and dissemination during the first days of the infection, indicating that the early, nonspecific defence mechanisms were affected. Virus clearance and elimination, which is mediated by specific immunity, seemed not to be influenced. Examination of cells from the peritoneal cavity and of livers from virus-infected mice showed that mercury detectable by autometallography was exclusively found in mature peritoneal macrophages and in Kupffer cells of the liver. Inflammatory cells, recruited to the peritoneal cavity or infiltrating the infectious foci of the liver, did not show any mercury deposits. Attempts to demonstrate an effect in vivo of mercury on potential antiviral macrophage functions like interferon-alpha/beta (IFN-alpha/beta) and tumour necrosis factor-alpha (TNF-alpha) secretion and oxidative burst capacity were not successful, possibly because recruited, inflammatory cells, which have not been exposed to the high mercury concentrations at the site of injection, take over these functions of intoxicated macrophages.

Acyclovir given as prophylaxis against oral ulcers in acute myeloid leukaemia: randomised, double blind, placebo controlled trial

OBJECTIVES

To evaluate (a) the prophylactic effect of the antiherpetic drug acyclovir on oral ulcers in patients with acute myeloid leukaemia receiving remission induction chemotherapy and thus (b), indirectly, the role of herpes simplex virus in the aetiology of these ulcers.

DESIGN

Randomised, double blind, placebo controlled trial.

SUBJECTS

74 herpes simplex virus seropositive patients aged 18-84. Thirty seven patients received acyclovir (800 mg by mouth daily) and 37 placebo. The patients were examined daily for 28 days.

MAIN OUTCOME MEASURES

Occurrence of herpes labialis, intraoral ulcers, and acute necrotising ulcerative gingivitis.

RESULTS

The two populations were comparable in age, sex, type of antineoplastic treatment, and history of herpes labialis. Acute oral infections occurred in 25 of the acyclovir treated patients and 36 of the placebo treated patients (relative risk 0.69 (95% confidence interval 0.55 to 0.87)). This difference was due to a reduction in the incidence of herpes labialis (one case versus eight cases; relative risk 0.13 (0.02 to 0.95)), intraoral ulcers excluding the soft palate (one case versus 13 cases; relative risk 0.08 (0.01 to 0.56)), and acute necrotising ulcerative gingivitis (one case versus eight cases; relative risk 0.13 (0.02 to 0.95)). However, ulcers on the soft palate were diagnosed with similar frequency in the two groups. Isolation of herpes simplex virus type 1 in saliva was reduced from 15 cases in the placebo group to one case in the acyclovir group (relative risk 0.07 (0.01 to 0.48)).

CONCLUSION

Intraoral ulcers excluding the soft palate are most often due to infection with herpes simplex virus, whereas ulcers on the soft palate have a non-herpetic aetiology. The findings suggest that acute necrotising ulcerative gingivitis may also be due to herpes simplex virus. Prophylaxis with acyclovir should be considered for patients with acute myeloid leukaemia during remission induction therapy.

Sterility of the uterine cavity

In a prospective open study the sterility of the uterine cavity was evaluated in 99 women admitted for hysterectomy. The indications for hysterectomy were in most cases persistent irregular vaginal bleeding and fibromyomas of the uterus. Samples for both aerobic and anaerobic bacteria, Chlamydia trachomatis, yeasts and viruses were taken preoperatively from the apex of the vagina and cervical os. Immediately after hysterectomy the uterus was opened under sterile conditions and samples obtained from the isthmus and fundus of the uterine cavity for microbiological examination. Wet smears were taken from the same sites. Nearly a quarter of all the patients harbored one or more microorganisms in the uterus, mostly Gardnerella vaginalis, Enterobacter and Streptococcus agalactiae. We found that in a significant number of cases, the uterine cavity is colonized with potentially pathogenic organisms which may play a causative role in endometritis. The results indicate that inflammation of the uterine cavity should be evaluated by hysteroscopic examination before hysterectomy is undertaken in patients with persistent irregular vaginal bleeding.

Effect of mercuric chloride on macrophage-mediated resistance mechanisms against infection with herpes simplex virus type 2

Macrophages play an important role in the early, nonspecific resistance to infection with herpes simplex virus. Mercuric chloride (HgCl2) accumulates in macrophages and has in certain concentrations a marked influence on the functional capacity of these cells. Therefore the influence of HgCl2 on resistance to generalized infection with herpes simplex virus type 2 (HSV-2) in mice and its effect on the HSV-2-induced activation of macrophages in vitro was examined. Mice injected intraperitoneally with HgCl2 24 h before infection with HSV-2 had more than 100 times higher virus titres in the liver 4 days after infection than mice not receiving any mercury. HgCl2 exerted a toxic effect on macrophages in vitro, which was especially pronounced during their adherence. Macrophages infected with HSV-2 were activated for an enhanced respiratory burst. This activation was abolished by treatment of the cells for 24 h with relatively low concentrations of HgCl2, resulting in macrophages with a potential to react with a respiratory burst comparable to that of uninfected cells. The HSV-2-induced activation of macrophages is mediated through the production and synergistic interaction of interferon-alpha/beta and tumour necrosis factor-alpha in an autocrine manner. The ability of these cytokines to activate macrophages and to interact synergistically was not affected by mercury. However the production by macrophages of both cytokines during the HSV-2 infection, but especially interferon-alpha/beta, which is essential for the activation, was reduced at low concentrations of HgCl2. Collectively these data indicate that mercury, by interfering with the early macrophage-production of cytokines, disables the early control of virus replication, leading to an enhanced infection.

Mannan-binding protein and bovine conglutinin mediate enhancement of herpes simplex virus type 2 infection in mice

A broad range of plant lectins have recently been shown to inhibit the infectivity of herpes simplex virus type 1 (HSV-1) in vitro. We decided to investigate the role of mammalian lectins in infection with herpes simplex virus. Two lectins, conglutinin and mannan-binding protein (also called mannose-binding protein, MBP), belonging to the collectin family of lectins, were examined. Four week-old BALB/c mice were injected subcutaneously with 100 micrograms bovine conglutinin or 50 micrograms human MBP 1 day before intravenous infection with 5 x 10(4) PFU of herpes simplex virus type 2 (HSV-2). A three-fold increase in virus titre of the liver was observed on day 3 of the infection in the mice pretreated with conglutinin or MBP, whereas no effect was seen on days 1 and 5. In a standard plaque assay using Vero cells we were not able to demonstrate reproducibly either infection inhibition or infection enhancement, when virus was pre-incubated with differing concentrations of the collectins. The concentrations used were similar to those used by us in vivo, and by others in in vitro experiments showing inhibition of the infectivity of HSV-1 with plant lectins. In an ELISA with HSV-2 antigens captured on anti-HSV-2 antibodies, calcium-dependent and carbohydrate inhibitable binding of the collectins was observed. Our results indicate that the effect of endogenous mammalian collectins in vivo may not be neutralization as suggested by the data using plant lectins. Instead, the previously described opsonizing activity of the mammalian collectins may provide the virions with an alternative port of entry into cells leading to infection enhancement.

Comparison of the interaction of methyl mercury and mercuric chloride with murine macrophages

The toxicity of organic methyl mercury was studied on murine macrophages in cell culture and compared to that of inorganic mercuric chloride. Long-term treatment of macrophage cultures with methyl mercury resulted in decreased cell viability in a concentration-dependent fashion. Experiments showed that 20 microM methyl mercury was highly toxic, causing cell death within a few days, while cultures exposed to lower levels were less severely affected. Comparison of the toxicity of organic and inorganic mercury by cell viability showed no difference between equimolar concentrations of methyl mercury and mercuric chloride. Furthermore, protein synthesis (interferon-alpha/beta) was reduced in a concentration dependent manner and had the same reduced magnitude in cells treated with either methyl mercury or mercuric chloride. However, impairment of random migration and phagocytosis of macrophages appeared at lower concentrations in cells exposed to methyl mercury than in cells exposed to mercuric chloride. Electron microscopy of cells exposed to methyl mercury revealed mercury deposits in lysosomes and dispersed in the cytoplasm and nuclei. The present study shows that methyl mercury and mercuric chloride impair cell viability and protein production in cell cultures at equimolar concentrations, while methyl mercury inhibits macrophage functions such as migration and phagocytosis at lower concentrations than mercuric chloride.

Bioactive and inactive forms of tumor necrosis factor-alpha in spinal fluid from patients with meningitis

Twenty-four patients, including 12 with meningitis, were admitted with meningeal symptoms and fever. Their serum and spinal fluid tumor necrosis factor-alpha (TNF alpha) levels were determined by ELISA. TNF alpha immunoreactivity was found in spinal fluid of 10 meningitis patients and one nonmeningitis patient, whereas 7 sera, 5 from meningitis patients, contained TNF alpha. Levels were significantly higher in spinal fluids than in serum samples, and the TNF alpha bioactivity of spinal fluids and sera was considerably below predictions based on ELISA measurements. Gel filtration chromatography demonstrated the presence of both polymeric (greater than 200 kDa) and oligomeric (10-40 kDa) TNF alpha in spinal fluid. Significant bioactivity was obtained only from samples containing oligomeric cytokine. In agreement with previous in vitro findings, these results strongly indicate that bioactive TNF alpha oligomers form inactive polymers and monomers, which could contribute to the observed in vivo discrepancies between immunoreactive and bioactive protein. Finally, the data support the concept of local central nervous system production of TNF alpha in meningitis.

Autometallography used as a histochemical indicator of lysosome function in cultured cells

The present paper suggests the autometallographic demonstration of intralysosomal silver as a sensitive tool for the detection of subtile toxic effects in cell cultures, the method is suggested to primarily detect lysosomal damage.

Herpes simplex virus and intraoral ulcers in immunocompromised patients with haematologic malignancies

Possible factors predisposing to the development of intraoral ulcers in immunocompromised patients with haematologic malignancies were investigated. Among 46 patients undergoing antineoplastic treatment, 18 developed an intraoral ulcer during the prospective study. Patients with or without ulcers were comparable with respect to underlying disease, presence of teeth, the qualitative composition of the aerobic and facultatively anaerobic oral microflora, herpes simplex virus (HSV) titer positivity, a past history of herpes labialis, leukocyte and thrombocyte counts, and duration of fever. Viral cultures from saliva revealed an association between the presence of HSV in saliva and the presence of intraoral ulcers. HSV was not isolated from the saliva of any patient without ulcers. Viral cultures from the ulcers revealed growth of HSV in 11 (61%) of the 18 patients with ulcers. HSV-positive ulcers were located more often on the alveolar process than elsewhere in the oral cavity. Ulcers on the lateral borders of the tongue and on the buccal mucosa were found only in dentate patients. Development of intraoral ulcers was not associated with an increase of the HSV titer in serum in any patient. It is concluded that some intraoral ulcers, especially when located on the alveolar process, are associated with and probably caused by HSV, while mechanical trauma during mastication seems likely to be involved in the pathogenesis of ulcers elsewhere in the oral cavity.

Bioactive human recombinant tumor necrosis factor-alpha: an unstable dimer?

As determined by native polyacrylamide gel electrophoresis (PAGE) and gel chromatography the molecular mass of native tumor necrosis factor (TNF)-alpha was approximately 35 kDa. When incubated at low concentrations (less than 1 nM) 125I-labeled TNF-alpha and unlabeled TNF-alpha rapidly multimerized or dissociated into monomers and bioactivity decreased. Sodium dodecyl sulfate (SDS)-PAGE analysis of cross-linked 125I-labeled TNF-alpha demonstrated bands of multi- and trimeric TNF-alpha in addition to dominating bands of dimers and monomers. Tri-, di- and monomeric TNF-alpha were recovered from SDS-PAGE gels and allowed to renature. Of the original receptor-binding activity, 10%-15% was obtained with cross-linked TNF-alpha dimers, whereas none was recovered from preparations of trimeric TNF-alpha. Multimeric and monomeric TNF-alpha exhibited little or no binding activity, and cell-bound, cross-linked TNF-alpha which was dissociated from cellular binding sites was mainly dimeric. 125I-labeled TNF-alpha bound to lymphokine-activated killer (LAK) cells and binding kinetics were much similar (Kd approximately 100 pM) to those reported in other normal cell types. The number of receptors per LAK cell was approximately 4 x 10(3). Cross-linking of TNF-alpha to binding sites in U-937 and LAK cells yielded a receptor-ligand complex of about 80/90 kDa. At 37 degrees C, 125I-labeled TNF-alpha was rapidly internalized and degraded in L-929, U-937 and LAK cells. Degradation of ligand and recycling of receptors were blocked in the presence of methylamine. Methylamine significantly inhibited TNF-alpha-mediated cytolysis of L-929 cells and caused a quantitatively corresponding reduction in cellular TNF-alpha uptake, indicating that L-929 lysis was mediated by receptors.

Differential sensitivity of macrophages from herpes simplex virus-resistant and -susceptible mice to respiratory burst priming by interferon-alpha/beta

Herpes simplex virus primes mouse macrophages for a genetically determined respiratory burst mediated in an autocrine manner by interferon (IFN)-alpha/beta. We have analysed the effect of IFN-alpha/beta on the respiratory burst capacity of mouse peritoneal macrophages by luminol-dependent chemiluminescence using phorbol myristate acetate as trigger. Crude macrophage-produced IFN-alpha/beta as well as purified IFN-alpha and -beta regularly augmented the respiratory burst capacity of peritoneal cells in a concentration-dependent manner. The augmented response was exclusively mediated by macrophages and was manifest after 4 h incubation with IFN-alpha/beta, peaked after 8 h and gradually declined to near background levels after 24 h. The effect of macrophage-produced IFN-alpha/beta was completely abolished by preincubation of IFN with antiserum to IFN-alpha/beta. The data obtained with this antiserum indicated that endogenous IFN, undetectable by a standard cytopathic effect-inhibition assay, was sometimes spontaneously produced by the peritoneal cells. Furthermore, the crude macrophage preparation seemed to contain a macrophage deactivating factor counteracting the effect of IFN-alpha/beta. Genetic analysis of the sensitivity of macrophages for the respiratory burst-priming effect of IFN-alpha/beta revealed that the trait is inherited as a co-dominant autosomal feature. Macrophages from herpes simplex virus-resistant C57BL/6 mice were more sensitive than macrophages from virus-susceptible BALB/c mice and cells from mice of the reciprocal crosses showed an equal sensitivity intermediate between those of the parental strains. A physiological role of differential IFN sensitivity in the context of resistance to virus infections is suggested.

Effects of selenium on toxicity and ultrastructural localization of mercury in cultured murine macrophages

The effects of selenium on cellular toxicity and histochemical distribution of mercury were examined in a cell culture system of mouse peritoneal macrophages. Selenium protected against the toxicity of mercury in cultures exposed to 4 microM of mercuric chloride. Selenomethionine caused a significant increase in cell survival throughout the experiments, while sodium selenite delayed the toxicity of mercury for a while, after which selenite itself had a toxic effect. The amount of mercury visualized by autometallography was increased in macrophage cultures pre-exposed to sodium selenite or selenomethionine. The additional mercury made visible by this histochemical demonstration was located in the cytoplasm as well as in the lysosomes.

Herpes simplex virus type 2 primes mouse macrophages for an early and genetically determined respiratory burst mediated by interferon-alpha/beta

The influence of infection by herpes simplex virus type 2 (HSV-2) on the respiratory burst capacity of mouse macrophages was studied by luminol-dependent chemiluminescence with phorbol myristate acetate (PMA) as trigger. Peritoneal cells from virus-infected mice were strongly primed for a respiratory burst during the acute phase of the infection. By 12 h after infection the response had increased 40-fold over control values. Most of the response was elicited by mononuclear phagocytes. When resting peritoneal macrophages were infected with HSV-2 in vitro a maximal priming effect was seen with 2 x 10(6) p.f.u./ml of virus after 8 h, but a significant response was obtained after 4 h of infection; after 12 h incubation with virus the response declined to reach background levels at 24 h. Peritoneal cells from C57BL/6 mice which are relatively resistant to HSV-2 showed a higher respiratory burst capacity after infection than cells from more susceptible BALB/c mice. Incubation of macrophages with crude niurine interferon (IFN)-alpha/beta produced by macrophages or purified murine IFN-alpha, in concentrations comparable to those obtained early (2 to 5 h) after infection of macrophage cultures with HSV-2 also augmented the respiratory burst. Addition of an IFN-alpha/beta-specific antiserum to HSV-2-infected cultures almost completely removed the response. We therefore conclude that HSV-2 induces an early and genetically determined activation of macrophages, mediated in an autocrine manner by IFN-alpha/beta secreted by the macrophages early during infection.

Autocrine secretion of tumor necrosis factor under the influence of interferon-gamma amplifies HLA-DR gene induction in human monocytes

Recombinant interferon-gamma (IFN-gamma) induced HLA-DR gene expression in both U937 and THP-1 human monocytic cell lines, although the former was only very weakly inducible. Combination of recombinant tumor necrosis factor (TNF) and IFN-gamma resulted in a synergistic enhancement of DR mRNA and protein induction in both cell lines. TNF alone increased the constitutive expression of the DR gene in THP-1 cells. In the HLA class II-negative U937 cells, TNF used alone was not able to induce DR gene expression. Such a negative result was not due to a lack of TNF receptor expression in U937 cells, since TNF clearly induced HLA class I and TNF gene expression in this cell line. THP-1, but not U937, cells secreted TNF under the influence of IFN-gamma. Neutralization of TNF by a specific antibody decreased IFN-gamma-induced DR antigen expression in THP-1 cultures. These observations indicate that TNF is not able to directly induce DR gene expression, but rather amplifies ongoing expression of this gene, whether constitutive or induced by IFN-gamma. In the two cell lines tested, the level of DR inducibility under the influence of IFN-gamma used alone depended on a different inducibility of TNF secretion by IFN-gamma. Altogether, our observations indicate that TNF, whether exogenous or endogenously produced under the influence of IFN-gamma, amplifies DR gene expression in monocytes, a phenomenon that may provide to such antigen-presenting cells a selective sensitivity to the DR-inducing effects of IFN-gamma.

Toxicity and ultrastructural localization of mercuric chloride in cultured murine macrophages

The effects of mercuric chloride on cell survival, phagocytosis and cell migration were examined in cultured mouse peritoneal macrophages, and the accumulation of mercuric chloride in the cells was visualized by autometallography and evaluated by light and electron microscopy. Macrophages exposed to mercury concentrations from 1.25 microM to 10 microM mercuric chloride showed a concentration- and time-dependent increase in mercuric chloride accumulation, while cells exposed to 20 microM and 40 microM mercury showed an inverse relationship between mercury concentration and the accumulation of mercury. Mercury concentrations above these levels caused cell necrosis. Electron microscopy revealed that mercury was located primarily within lysosomes but also in the nucleus and cytoplasm. Mercury increased the death rate of macrophages in a concentration-dependent manner when cells were treated with mercury concentrations not causing cell necrosis. Further, we found that mercury clearly impaired macrophage random migration and possibly the capability for phagocytosis.

Autointerference in silver accumulation in macrophages without affecting phagocytic, migratory or interferon-producing capacity

Silver accumulation and processing in mouse peritoneal macrophages was studied in vitro by autometallographic visualization of intracellular silver. During the first 24 h of incubation in a medium containing from 5 microM to 20 microM of silver lactate, an inverse relationship between silver concentration in the former and visualizable silver in macrophages was recorded. Later, however, the cells treated with higher silver concentrations accumulated most silver. Cells exposed to silver concentrations above these levels exhibited acute coagulation necrosis and disintegrated within the first 15 min of silver treatment. Macrophages treated with silver lactate concentrations not causing acute cytotoxicity showed no impairment of their phagocytic, migratory or interferon-producing capacities. The significance of autointerference in silver accumulation and processing in macrophages is discussed, and a functional defect in the lysosome/phagosome system is suggested as a basis for the phenomenon.

Genetically determined difference in the antiviral action of alpha/beta interferon in cells from mice resistant or susceptible to herpes simplex virus type 2

Resistance of mice to infection with herpes simplex virus type 2 (HSV-2) is genetically determined. Embryonic cells from susceptible BALB/c and resistant C57BL/6 mice were equally sensitive to infection with HSV-2 as judged by plaque area, plaquing efficiency, endpoint titration and virus yield. Cells from C57BL/6 mice showed a higher sensitivity than cells from BALB/c mice to the protective action of two preparations of alpha/beta interferon against challenge with HSV-2. This was evident both from c.p.e. inhibition and yield reduction experiments. The difference in sensitivity was dependent on virus dose and was greatest (up to 50-fold) with low virus doses. An analysis of the genetics of the alpha/beta interferon sensitivity in cells from embryos of parental mice and embryos derived from reciprocal matings between HSV-2-resistant and -susceptible mice suggested that interferon sensitivity is inherited as a co-dominant autosomal trait. The induction of the interferon-induced enzyme 2'-5'-oligoadenylate synthetase was also different in cells from the two mouse strains, since significant levels were only detected in cells from C57BL/6 mice. It is suggested that differential interferon sensitivity of cells from HSV-2-resistant and -susceptible mice might be a factor of importance for the course of the infection.

X-linkage of the early in vitro alpha/beta interferon response of mouse peritoneal macrophages to herpes simplex virus type 2

The genetics of the early interferon response of mouse peritoneal cells to infection with herpes simplex virus type 2 (HSV-2) was studied in susceptible BALB/c and more resistant C57BL/6 mice and in reciprocal crosses between these mice. Wash-outs of the peritoneal cavity of normal C57BL/6 mice contained significantly more cells than wash-outs from BALB/c mice. Therefore, interferon induction with HSV-2 was studied under standardized conditions in vitro. Peritoneal cells reacted to HSV-2 infection by interferon production in a virus dose-dependent manner. Interferon was detected first after 2 h and peaked after 24 h. Cells from C57BL/6 mice of each sex produced significantly more early interferon than cells from BALB/c mice, and cells from female BALB/c mice produced more interferon than cells from males. This difference was not seen with C57BL/6 mice. Cultures of highly purified adherent cells yielded approximately 10 times as much interferon as cultures of non-adherent cells. Since treatment of cells with carbonyl iron and silica significantly reduced the amount of interferon produced, whereas 2000 rad of irradiation had no obvious effect, it is concluded that the main interferon-producing cell in the peritoneal cavity of mice in response to HSV-2 is of the monocyte/macrophage lineage. Interferon production in peritoneal cells was found to be quantitatively influenced by X-linked loci in that cells from male (BALB/c female X C57 male) F1 mice, which inherit the X chromosome from the low-responding BALB/c females, produced significantly lower amounts of interferon than cells from the other three F1 generation genotypes. All interferons were characterized as alpha/beta interferon. It is suggested that the early production of alpha/beta interferon in response to HSV-2 is influenced by X-linked loci, which might be involved in sex-linked differences in resistance to human herpesviruses.

Production of lymphokines and interferon by immune cells involved in recovery of mice from herpes simplex virus type 2 hepatitis

Adoptive transfer of spleen cells from mice 4 days after infection with herpes simplex virus type 2 (HSV-2) reduced the virus titer in the liver of recipient mice infected 24 h before transfer. Macrophage chemotactic factor (CF) and macrophage migration inhibition factor (MIF) were produced by day 3 of infection in spleen cell cultures stimulated with HSV-2, but not with control antigen, i.e. 1 day before the cells are active in adoptive transfer. Interferon was produced in cultures established throughout the infection but not in normal spleen cells. From days 1 to 5 of infection interferon was produced irrespective of in vitro restimulation, although the highest amounts were always produced after stimulation with the specific antigen. Spleen cells from mice infected for 6 days produced interferon only when stimulated with HSV-2. The cells from 6-day-immune mice active in adoptive transfer and CF and MIF production were found to be Thy 1+, Ig- and Lyt2-. Both Thy 1+ and plastic adherent cells were necessary for interferon production, whereas Ig+ and Lyt2+ cells did not produce interferon. The interferon was acid stable and neutralized by antiserum against alpha/beta-interferon and thus has the characteristics of alpha-interferon. The data indicate that a delayed type hypersensitivity reaction with lymphokine-induced macrophage recruitment into infectious foci may be a central feature of the recovery process in HSV-2-induced hepatitis. A possible role of interferon produced by the accumulated cells needs further investigation.

Experimental mastitis in mice induced by coagulase-negative staphylococci isolated from cases of mastitis in nursing women

Coagulase-negative staphylococci are frequently isolated from the milk of women with signs of puerperal mastitis. In order to evaluate the pathogenicity of these bacteria, strains of S. epidermidis and S. saprophyticus isolated from cases of mastitis in nursing women were inoculated into the mammary glands of lactating mice. Although clinical signs of mastitis were absent, by histological examination, mastitis was demonstrated in 78-93% of the glands. Abscesses were found in a few cases only. The inoculated bacteria were re-isolated in 41-61% of the cases, and when inoculated in numbers of 10(2) to 10(4) c.f.u. the bacteria multiplied above input levels in several cases. It is concluded that coagulase-negative staphylococci isolated from the milk of women with puerperal mastitis can produce mastitis in mice and should be considered as a possible etiologic agent of mastitis in nursing women.

Genetic aspects of macrophage involvement in natural resistance to virus infections

Macrophages are thought to constitute an important element in the body's natural defense against invasion and dissemination of viruses. Possible antiviral mechanisms of macrophages are defined and referred to as intrinsic, i.e. the ability of macrophages to serve as a nonpermissive barrier between the virus and susceptible cells and extrinsic, i.e. the ability of macrophages to affect the virus or virus replication in surrounding cells. Most studies on the role of macrophages in natural resistance to virus infections have been performed in animal models. An interesting aspect of many viral infections in animals is the finding of a genetically determined variation in natural resistance. Because of the availability of numerous inbred and congenic strains most studies on genetically determined resistance have been performed in mice. The classical examples are resistance to flaviviruses and susceptibility to mouse hepatitis virus, both of which are inherited as dominant, monogenic traits. With these viruses macrophage intrinsic restriction of virus replication has been found to express at the cellular level the genetics of resistance/susceptibility seen in the intact animal. Other examples, where macrophages have been implicated in genetically determined resistance include herpes simplex virus and influenza virus. The involvement of macrophages in natural resistance to these viruses is discussed in relation to other putative resistance determinants like interferon production and sensitivity and natural killer cell activity.

Host defences in mice against infections with herpes simplex virus

Herpes simplex virus infections in mice offer a useful model system for the study of viral pathogenesis. These infections usually result in complete recovery and involve a number of host defence mechanisms, including the action of macrophages, interferon production and specific immunological responses.

Ultrastructural localization of gold in macrophages and mast cells exposed to aurothioglucose

The ultrastructural localization of gold in resting, stimulated, and activated mouse peritoneal cells exposed in vivo and in vitro to aurothioglucose was examined by a photochemical technique. Activated macrophages from herpes simplex virus type 2 infected mice showed the heaviest accumulation of gold, located in phagolysosomes. Gold was also visualized in granules of mast cells and in nuclei of disintegrated cells. No gold was found in polymorphonuclear leucocytes and in lymphocytes. The mechanism by which gold is taken up into the cells is discussed.

Rapid and direct detection of herpes simplex virus and varicella-zoster virus antigens in clinical specimens by staphylococcal reagent and membrane filtration

Herpes simplex virus was detected rapidly and directly in 31 and varicella-zoster virus in two of 50 clinical specimens using specific antisera, stabilized staphylococci rich in protein A and membrane filtration. Microscopical examination of the cells retained on the filter membrane revealed attached staphylococci only on cells harbouring viral antigens but not on non-infected cells or cells from healthy donors. Infected cells treated with negative control sera and stabilized staphylococci and subsequently subjected to membrane filtration were also devoid of the marker. It was also possible to detect herpes simplex virus antigens in three specimens which were culture negative. Similar results were obtained with staphylococci specifically sensitized with anti-herpes simplex rabbit serum. No interfering, non-specific background of unattached staphylococci was observed on the filter membrane. The results were confirmed by the direct immunofluorescent test. The method is sensitive, specific, and provides results within 3 h. It could be employed for the rapid screening of populations at risk, e.g. pregnant women, medical personnel, and societies with a growing incidence of genital herpes. Since no special, expensive equipment is required, the method is also suitable for modestly equipped clinical laboratories.

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.

Rapid detection of herpes simplex virus and varicella-zoster virus in clinical specimens by the use of Staphylococcus aureus rich in protein A

Herpes simplex virus (HSV) type 1 and type 2 and varicella-zoster virus (VZV) were detected in cytospin preparations from clinical material by using specific antisera and Staphylococcus aureus, Cowan 1 strain, rich in protein A (SRA). Virus was isolated in tissue culture from 22 of the 30 specimens submitted for examination. Eighteen isolates showed cytopathic effect characteristic of HSV infection and 4 of VZV. In the cytospin preparations of the same samples HSV was detected in 15, two contained too few cells to allow a reliable diagnosis and one sample was negative when the SRA reagent was used. In the cytospin preparations of 2 of the 8 samples, which did not show cytopathic effect on isolation in tissue culture, HSV was detected by the SRA. This points to the possible presence of inactive virus in the specimens. All 4 cases of VZV infection were diagnosed correctly with the staphylococcal reagent. No reaction was observed between VZV antigens and rabbit anti-HSV sera. Cells in which viral infection was detected by specific antisera and SRA did not show staphylococcal adherence to their surface after interaction with normal rabbit or normal human serum. Similarly, cells from healthy donors, treated with positive and negative sera were found negative. The method is easy to perform and results can be obtained within three hours from the time specimens are received at the laboratory. Its use offers a rapid diagnosis in suspected cases of herpetic infections in which early therapy is recommended.

Macrophage migration inhibition as a correlate of cell-mediated immunity to herpes simplex virus type 2 in mice

Mice inoculated intraperitoneally or intravenously with herpes simplex virus type 2 (HSV-2) develop a focal necrotizing hepatitis. The livers show expanding foci of necrosis and increasing virus content during the first days of the infection with maximal titers achieved on day 3. The clearance of virus from the organ is manifest from day 4 onward with the most dramatic fall in virus content occurring between days 4 and 5. The development of immunity during the course of infection was assessed by adoptive transfer experiments and by measuring macrophage migration inhibition factor (MIF) production of spleen cells in an indirect agarose microdroplet assay. Antiviral activity of adoptively transferred spleen cells was demonstrable from day 4 of the infection when 50 X 10(6) spleen cells were transferred into recipient mice infected 24 h previously. MIF production in spleen cell cultures stimulated with antigen was found to be specific in that activity was only detected in cultures derived from immune mice and stimulated with the virus antigen. The response was found to be antigen-dose and cell-number dependent. Significant MIF production was demonstrable in spleen cell cultures derived from mice 3 days after the infection, i.e. concomitant with the initiation of recovery and before antiviral activity can be detected in transfer experiments. It is suggested that a delayed type hypersensitivity reaction with lymphokine production leading to recruitment of macrophages and their retention and activation in the foci of infection may be a major factor in the recovery from the infection.

The use of Staphylococcus aureus rich in protein A in the detection of herpes simplex virus antigens

Herpes simplex virus (HSV) type 1 antigens were detected in infected human embryonic lung cells with the aid of specific antiserum and Staphylococcus aureus rich in protein A. When such staphylococci carrying specific anti-HSV IgG on their surface were interacted with various suspension of virus, a reduction in the initial virus titre of about 65% was obtained. However, no direct coagglutination was observed between cell-free supernatants of HSV or HSV-infected cells and sensitized staphylococci. When monolayers or suspended cells infected with the virus were treated with dilutions of specific anti-HSV antiserum followed by non-sensitized staphylococci (indirect method), an "aureola" of the bacteria was detected around the cells expressing the viral antigens. A similar picture was observed when infected cells were interacted directly with sensitized staphylococci. Viral antigens were detected already 12 hours post infection, well before the appearance of cytopathic effect. The sensitivity of the indirect method was found to be higher than that of the direct one and dependent on the multiplicity of infection and the serum dilution used. The method is proposed as a rapid means of identifying viral antigens in diagnostic and experimental virology.

Recovery of mice from herpes simplex virus type 2 hepatitis: adoptive transfer of recovery with immune spleen cells

Young BALB/c mice inoculated intraperitoneally with herpes simplex virus type 2 develop focal necrotizing hepatitis. After infection, the livers of these mice show increasing virus titers, which reach a maximum on day 3 after infection; this is followed by a dramatic decrease in the amount of virus recovered on days 4 and 5. This decrease in virus content is accompanied by a progressive infiltration of the lesions with mononuclear leukocytes and an apparent resolution of the lesions. Adoptive transfer of immune spleen cells from mice infected 6 days earlier accelerated this process. When 50 x 10(6) to 100 x 10(6) immune spleen cells were transferred 24 h after infection, the inflammatory response and the clearance of virus from the livers were advanced by almost 2 days. As few as 12 x 10(6) immune spleen cells accelerated the healing process, whereas fewer immune cells, disrupted immune cells, or normal spleen cells did not have an effect. The protection conferred by herpes simplex virus type 2-sensitized immune spleen cells was specific since mouse cytomegalovirus- or vaccinia virus-sensitized immune spleen cells had no effect on the course of infection with herpes simplex virus type 2, whereas some cross-reactivity was observed between herpes simplex virus types 1 and 2. This model seems to be suitable for examining the immunological mechanisms that are active during recovery from visceral herpes simplex virus infections.

Role of macrophages in natural resistance to virus infections

Images

Role of activated macrophages in resistance of congenitally athymic nude mice to hepatitis induced by herpes simplex virus type 2

Congenitally athymic nude (nu/nu) mice of a BALB/c genetic background were found considerably more resistant to the induction of focal necrotic hepatitis by herpes simplex virus type 2 (HSV-2) tha, were phenotypically normal littermates (nu/+) or BALB/c mice. The augmented resistance was age dependent, as it was only manifested in mice from 4 to 5 weeks of age. Studies of the course of infection showed that nude mice were able to restrain virus multiplication in the liver far better than normal mice in the early phase of infection. However, they seemed inferior to normal mice in eliminating the infectious process. In vitro investigation of peritoneal macrophages revealed that macrophages from 6-week-old nude mice exhibited accelerated spreading and were three times as restrictive in the replication of HSV-2 as macrophages from normal mice. However, no difference was found in the efficiency of adsorption/phagocytosis between macrophages from nude and normal mice. The increased resistance of nude mice could be abolished by blockade of the microphage function of the mice by silica. Nude mice reconstituted at birth with thymus cells were just as susceptible to infection as normal mice. These data suggest that the increased resistance of nude mice to HSV-2 hepatitis is due to the presence of nonspecifically activated macrophages before infection.

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.

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.

Effect of silica on the pathogenic distinction between herpes simplex virus type 1 and 2 hepatitis in mice

The role of macrophages in the difference in liver pathogenicity between herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) in mice was investigated by selectively blocking the macrophage function of the mice by silica. Intravenous administration of 3 mg of silica 2 h before virus inoculation partially abolished the difference between the two virus types, as judged by macroscopic and microscopic examination of the livers and by virus isolation studies. Intraperitoneal inoculation of 50 mg of silical before virus seemed more effective in suppressing the macrophage function, since this treatment almost completely eliminated the difference in hepatotropism between HSV-1 and HSV-2 as assessed by the number and size of the lesions appearing in the liver. The final outcome of the infection, death from encephalitis, was, however, not influenced by macrophage blockade.

Biological conditions influencing the focal necrotic hepatitis test for differentiation between herpes simplex virus types 1 and 2

Some biological conditions of the focal necrotic hepatitis test for the differentiation between herpes simplex virus (HSV) types 1 and 2 were investigated. Most of 13 different strains of mice tested were found usable in the test. An upper age limit (4 weeks) for the appearance of focal necrotic liver lesions was found in one strain of mice, while this was not seen in another strain. The minimum dose in 3- to 4-week-old mice was found to be as small as 10(2) to 10(3) p.f.u. in 0.1 ml of diluent. Suckling rats and hamsters, aged up to 7 and 14 days, respectively, were found to be convenient as alternative test animals. Finally, it was observed that focal necrotic hepatitis did not develop in the nude mouse with thymic aplasia on intraperitoneal inoculation of HSV type 2. The possible involvement of the thymus in the pathogenesis of the focal necrotic lesions is briefly discussed.

The influence of hyperthermia and poly I:C on Semliki Forest virus infection in mice

In mice infected intraperitoneally with 10(3) intracerebral suckling mice LD50 of Semliki Forest virus an additive reduction in mortality was found when the protective effect of hyperthermia and synthetic polyriboinosinic and polycytidylic aicds (Poly I:C) was combined. The effects of the two treatments seem to be independent of each other as Poly I:C was found to have no influence on the body temperature of mice, nor did hyperthermia increase the amount of interferon induced by Poly I:C.