Restriction of herpes simplex virus by macrophages. An analysis of the cell-virus interaction

c-Jun Signaling During Initial HSV-1 Infection Modulates Latency to Enhance Later Reactivation in addition to Directly Promoting the Progression to Full Reactivation

Herpes simplex virus-1 (HSV-1) establishes a latent infection in peripheral neurons and can periodically reactivate to permit transmission and clinical manifestations. Viral transactivators required for lytic infection are largely absent during latent infection and therefore HSV-1 relies on the co-option of neuronal host signaling pathways to initiate its gene expression. Activation of the neuronal c-Jun N-terminal kinase (JNK) cell stress pathway is central to initiating biphasic reactivation in response to multiple stimuli. However, how host factors work with JNK to stimulate the initial wave of gene expression (known as Phase I) or the progression to full, Phase II reactivation remains unclear. Here, we found that c-Jun, the primary target downstream of neuronal JNK cell stress signaling, functions during reactivation but not during the JNK-mediated initiation of Phase I gene expression. Instead, c-Jun was required for the transition from Phase I to full HSV-1 reactivation and was detected in viral replication compartments of reactivating neurons. Interestingly, we also identified a role for both c-Jun and enhanced neuronal stress during initial neuronal infection in promoting a more reactivation-competent form of HSV-1 latency. Therefore, c-Jun functions at multiple stages during HSV latent infection of neurons to promote reactivation. Importantly, by demonstrating that initial infection conditions can contribute to later reactivation abilities, this study highlights the potential for latently infected neurons to maintain a molecular scar of previous exposure to neuronal stressors.

Strength in diversity: Understanding the pathways to herpes simplex virus reactivation

Herpes simplex virus (HSV) establishes a latent infection in peripheral neurons and can periodically reactivate to cause disease. Reactivation can be triggered by a variety of stimuli that activate different cellular processes to result in increased HSV lytic gene expression and production of infectious virus. The use of model systems has contributed significantly to our understanding of how reactivation of the virus is triggered by different physiological stimuli that are correlated with recrudescence of human disease. Furthermore, these models have led to the identification of both common and distinct mechanisms of different HSV reactivation pathways. Here, we summarize how the use of these diverse model systems has led to a better understanding of the complexities of HSV reactivation, and we present potential models linking cellular signaling pathways to changes in viral gene expression.

Herpes Simplex Virus 1 Interaction with Myeloid Cells In Vivo

Herpes simplex virus 1 (HSV-1) enters mice via olfactory epithelial cells and then colonizes the trigeminal ganglia (TG). Most TG nerve endings are subepithelial, so this colonization implies subepithelial viral spread, where myeloid cells provide an important line of defense. The outcome of infection of myeloid cells by HSV-1 in vitro depends on their differentiation state; the outcome in vivo is unknown. Epithelial HSV-1 commonly infected myeloid cells, and Cre-Lox virus marking showed nose and lung infections passing through LysM-positive (LysM(+)) and CD11c(+) cells. In contrast, subcapsular sinus macrophages (SSMs) exposed to lymph-borne HSV-1 were permissive only when type I interferon (IFN-I) signaling was blocked; normally, their infection was suppressed. Thus, the outcome of myeloid cell infection helped to determine the HSV-1 distribution: subepithelial myeloid cells provided a route of spread from the olfactory epithelium to TG neurons, while SSMs blocked systemic spread.

IMPORTANCE

Herpes simplex virus 1 (HSV-1) infects most people and can cause severe disease. This reflects its persistence in nerve cells that connect to the mouth, nose, eye, and face. Established infection seems impossible to clear. Therefore, we must understand how it starts. This is difficult in humans, but mice show HSV-1 entry via the nose and then spread to its preferred nerve cells. We show that this spread proceeds in part via myeloid cells, which normally function in host defense. Myeloid infection was productive in some settings but was efficiently suppressed by interferon in others. Therefore, interferon acting on myeloid cells can stop HSV-1 spread, and enhancing this defense offers a way to improve infection control.

Oncolysis of prostate cancers induced by vesicular stomatitis virus in PTEN knockout mice

Vesicular stomatitis virus (VSV) is an oncolytic virus which selectively infects and kills cancer cells. The goal of the present study was to determine the safety and efficacy of VSV treatment of prostate tumors that arise in situ in immunocompetent, transgenic prostate-specific PTEN-null (PTEN(-/-)) mice. Interferon-sensitive VSV(AV3 strain), which expresses luciferase, was injected intraprostatically into tumor-bearing PTEN(-/-) and control mice and then monitored for tissue bioluminescence over 96 hours. Virus readily dispersed throughout the bodies of mice after only 3 hours; however, it persisted at high levels for >72 hours in PTEN(-/-) mice, but at relatively low levels and for only approximately 48 hours in controls. Plaque assays provided a similar pattern, with much higher concentrations of replicating virus in prostates of PTEN(-/-) mice than in controls. Transient, low levels of virus were detected in the spleens of both groups. Apoptotic analyses by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling staining revealed that VSV(AV3) is able to selectively infect and kill prostate cells in PTEN(-/-) mice, while sparing normal cells in control mice. The primary mechanism for cell kill is apparently apoptotic oncolysis as opposed to neutrophil invasion as has been reported using xenograft models. These results suggest that control of locally advanced human prostate cancer may be achievable through intraprostatic injection and amplification of a safe oncolytic virus, such as VSV(AV3).

Drugs and immunity: cannabinoids and their role in decreased resistance to infectious disease

Marijuana, Cannabis sativa, elicits a variety of effects in experimental animals and humans. Delta-9-tetrahydrocannabinol (THC) is the major psychoactive component in marijuana. This substance has been shown, also, to be immunosuppressive and to decrease host resistance to bacterial, protozoan, and viral infections. Macrophages, T lymphocytes, and natural killer cells appear to be major targets of the immunosuppressive effects of THC. Definitive data which directly link marijuana use to increased susceptibility to infection in humans currently is unavailable. However, cumulative reports indicating that THC alters resistance to infection in vitro and in a variety of experimental animals support the hypothesis that a similar effect occurs in humans.

Pathologic studies and comparison of the virulence of herpes simplex virus type 2 from Okinawa, Japan and Chiang Mai, Thailand

The virulence of four herpes simplex virus type 2 (HSV 2) strains (K1-K4) isolated in Okinawa, Japan was investigated, and compared with four strains (C1-C4) from Chiang Mai, Thailand and a standard laboratory strain SAV. Virulence was tested on BALB/c and C57/black mice. After viral inoculation intraperitoneally, the distribution with the passage of time of the virus in the brain and other organs was also studied using the polymerase chain reaction (PCR) method and immunohistochemistry. Generally, Okinawan HSV 2 (K1, K3 and K4) were less virulent than Chiang Mai strains (C1-C4). Among the Okinawan strains, K2 was the most virulent, but slightly less so than C3 and C4. All four Chiang Mai strains (C1-C4) and one Okinawan strain (K2) were more virulent than SAV strain. The virulence of K3 was very weak and no animals died from the intraperitoneal inoculation. In the brain, viral DNA from each strain was demonstrated at 1-9 days after inoculation by the PCR method. However, K3 strain was detected in the brain only between one day and 3 days after virus inoculation, and not after day 5. Immunohistochemically, the virus antigen was first demonstrated around the 3rd ventricle at one day after viral inoculation, then strongly at the ventral hypothalamus and the temporal lobe at 3 days after viral inoculation, and slightly in the frontal lobe, hippocampus, pons and cerebellum (on day 5 after inoculation). Furthermore, in Kupffer cells in the liver and macrophages in the spleen, numerous viral antigens were demonstrated from one to 9 days after viral inoculation.(ABSTRACT TRUNCATED AT 250 WORDS)

The pathogenicity of a US3 protein kinase-deficient mutant of herpes simplex virus type 2 in mice

We have investigated the pathogenicity of a US3 protein kinase-deficient mutant (L1 BR1) of herpes simplex virus type 2 (HSV-2) for 4-week-old ICR mice to define the role of the viral protein kinase in virus-host interaction. When mice were intraperitoneally infected with 10(5)PFU of L1 BR1, the virus disappeared from the peritoneal cavity by 2 days postinfection and failed to induce any significant histopathological changes in the liver and spleen although viral antigens were occasionally detected in the epithelial cells of small bile ducts and small vascular wall. The parental virus (HSV-2 186) and a revertant of the mutant (L1 B-11) both caused severe hepatitis, and viral antigens were clearly detected in the hepatocytes and Kupffer cells in the focal necrotic areas. Both of the virulent viruses, unlike L1 BR1, could produce infectious progeny and cytopathic effects in freshly harvested peritoneal macrophages. The growth of L1 BR1 in peritoneal macrophages was restricted at a stage of or prior to viral DNA synthesis but after the induction of viral DNA polymerase. In addition, the production and/or the spread of mutant in mouse embryo fibroblasts (MEF) was found to be much more effectively suppressed by cocultivation of peritoneal macrophages than that of 186. An almost complete inhibition of L1 BR1-plaque formation was observed at a macrophage-to-MEF ratio of 4:1. These results suggest that the attenuation of L1 BR1 following intraperitoneal infection is primarily due to its high sensitivity to intrinsic and extrinsic inhibition of peritoneal macrophages and that the US3 protein kinase may play a role in viral DNA replication in peritoneal macrophages.

delta-9-Tetrahydrocannabinol inhibits cell contact-dependent cytotoxicity of Bacillus Calmétte-Guérin-activated macrophages

The effect of delta-9-tetrahydrocannabinol (delta-9-THC), the major psychoactive component of marijuana, on the capacity of Bacillus Calmétte-Guérin (BCG)-activated macrophages to lyse L929 tumor cells, Naegleria fowleri amoebae, and herpes simplex virus-infected cells was examined. Delta-9-THC inhibited tumoricidal and amoebicidal activity in a dose-related manner. Antiviral activity was decreased when mice received 25 and 50 mg/kg delta-9-THC. The cannabinoid did not directly suppress the activation of macrophages as determined by levels of 5'-nucleotidase activity and did not inhibit splenic T-lymphocytes of BCG-recipient mice from producing interferon gamma. Nomarski optics microscopy, scanning electron microscopy, and radiolabeling binding studies demonstrated that macrophages from delta-9-THC-treated mice retained their capacity to attach to their targets. These results suggest that delta-9-THC suppresses cell contact-dependent amoebicidal, tumoricidal, and antiviral activities of activated macrophages at a stage following effector cell-target cell conjugation.

Latent infection of SCID mice with herpes simplex virus 1 and lethal cutaneous lesions in pregnancy

Some SCID mice survived primary infection with herpes simplex virus 1 without the development of peripheral lesions but established coculture-positive ganglionic latency when a low dose of a wild-type strain was inoculated intracutaneously. The latency was also evidenced by the development of the fatal zosteriform skin lesions and the isolation of the virus during pregnancy. We consider that the viral entry into neurons without successive replication, rather than the arrest of the lytic infection within the cells, is an important mechanism in the establishment of latency.

Temperature sensitivity of herpes simplex virus type 1 is a tissue-dependent phenomenon

The temperature sensitivity of herpes simplex virus type 1 (HSV-1) was assessed in primary cultures of mouse central nervous system (MNS) cells and mouse embryo cells (MEC). Infectious yields were determined and the ultrastructural morphogenesis of HSV-1 particles was compared following incubation at 37 or 40.5 degrees C. Yields of infectious virus were significantly reduced for both types of cell cultures following incubation at 40.5 degrees C. However, the effect of supraoptimal temperature (40.5 degrees C) on HSV-1 replication in MEC was significantly greater than the effect of supraoptimal temperature on virus replication in MNS cells. With respect to viral morphogenesis, no significant differences were found in either the quantity or the appearance (empty versus electron opaque core) of intranuclear particles present per infected nucleus, regardless of cell type or incubation temperature. However, complete virus particles (enveloped capsids with dense cores) were never observed in MEC at 40.5 degrees C, either intracytoplasmically or extracellularly. In contrast, complete virus particles were observed in MNS cell cultures at 40.5 degrees C, albeit in reduced numbers. At the permissive temperature (37 degrees C), complete intracytoplasmic and/or extracellular virus particles were associated with every infected cell in the MNS cell or MEC cultures. Thus an interactional effect on HSV-1 replication was found between cell culture type and incubation temperature.

Localization of herpes simplex virus type 1 in sebaceous glands of mice

The distribution of HSV-1 during the development of zosteriform skin lesions in SCID mice was analyzed by immunofluorescence and electron microscopy. The virus initially appeared within certain keratinocytes, sometimes surrounded by keratinocytes whose surfaces were also positive for the antigens, in the lower epidermal layers including the hair follicles, and then extended upward to the entire epidermis and downward to the sebaceous glands 1-2 days later, when no macroscopic skin lesion was seen. The affected epidermal cells subsequently degenerated and lost their viral antigens within a day, when the zosteriform lesion then became evident. This was followed by a degeneration of the dermis. The sebaceous glands eventually degenerated in 10 days, but some glands in the necrotic skin areas preferentially retained HSV-1. The horizontal spread of the virus in the epidermis beyond the first invaded dermatome occurred much later. In mice passively immunized with specific immune serum, viral antigens were observed even 20 days after the infection in sebaceous glands in necrotized areas. Therefore, HSV-1 appears to spread first via the extracellular fluid among the keratinocytes after being shed from nerve endings, and then produces a successive degeneration of the affected keratinocytes which may prevent any further extension of horizontal viral spread. The pilosebaceous apparatus is possibly acting as a site not only for the replication of HSV-1 with a delayed cytopathic effect, but also as an area that is temporarily sheltered from host defense mechanisms.

Polymerase chain reaction for early detection of HSV-DNA in cerebrospinal fluid: an experimental mouse encephalitis study

A series of experiments was carried out using a mouse HSV-1 encephalitis model for detecting HSV-DNA in CSF by the polymerase chain reaction (PCR). The results were correlated with the time period after corneal inoculation, clinical signs and symptoms, and progression of infection in brain tissue (antigen detection and histopathology), and were compared with virus isolation by spin-amplified culture (SAC/IF). The PCR proved to be superior to SAC/IF, both with respect to early detection and the percentage of positive samples. The results of PCR did not correlate with signs of disease, nor with the interval post-inoculation. A correlation with the spread of HSV within the brain tissue was found. The possible pathways for virus spread from brain parenchyma to the CSF as well as a possible explanation for the low amounts of virus and viral-DNA within the CSF are discussed.

Interleukin-3 protects mice from acute herpes simplex virus infection

Evidence presented here from kinetic studies of interleukin-3 (IL-3) production by spleen cells from adult mice infected subcutaneously with HSV-1 and stimulated with virus antigen in vitro shows that high levels of IL-3 were produced at the onset of the animal's recovery from the disease state. Injections of anti-IL-3 antibody into HSV-1-infected mice resulted in exacerbation of the disease. Primary mouse embryonic head cells grown in the presence of murine IL-3, when infected with HSV-1, showed a 1000-fold decrease in virus titre compared with untreated control cells. This inhibiting effect was reversed by anti-IL-3 and anti-IFN-alpha, beta and gamma antibodies. These data suggest that IL-3 plays a host-protective role against HSV infection and it does so probably by inducing brain cells to produce interferons which then inhibit virus replication.

Use of live Saccharomyces cerevisiae cells as a biological response modifier in experimental infections

A short-term oral administration of live Saccharomyces cerevisiae cells, strain Sillix Hansen DSM 1883, resulted in enhanced resistance of mice toward infections with K. pneumoniae. S. pneumoniae and S. pyogenes A produced by intranasal inoculation. Yeast pre-treatment also increased the efficacy of antibiotic therapy in bacterial infections and of antiviral drugs in viral infections. Yeast treatment of animals stimulated phagocytosis, activated the complement system and induced interferon which are likely to represent the main mechanisms of action whereby pretreatment of mice with live S. cerevisiae cells increases resistance to infection. It is concluded that preventive administration of live Saccharomyces cerevisiae cells should be used for increasing resistance to bacterial infections, in particular of the respiratory tract, or to viral infections, as well as an adjunct to antibiotic and antiviral drug therapy.

Protection against lethal Venezuelan equine encephalitis (VEE) virus infection by cell-free supernatant obtained from immune spleen cells

Considerable effort has been directed at unraveling the mechanisms underlying protection and recovery in acute viral infections. Various factors, including antibody, interferon, lymphokines and certain lymphocyte and macrophage cell constituents, have been shown to play a role in host recovery. We have previously studied an adoptive transfer system in experimental VEE virus CNS infection in a mouse model, and shown that both T cells and B cells exert an influence in protecting the host from lethal CNS infection with this virus. Because of the complexity involved in the adoptive transfer of protection, we sought a simpler and more easily defined experimental approach to dissect the various factors responsible for protection in our model. We here report that immune cell-free supernatant, derived from mice immunized with vaccine against VEE virus, exerts as much protection as the whole cell transfer system against lethal VEE virus infection. Such cell-free supernatant allowed us to look more closely at individual host immune factors in their relationship to protection against infection. Studies herein reported demonstrate that the protection conferred by immune cell-free supernatants is not dependent on neutralizing antibody or interferon, but rather appears to be related to the presence of both interleukin-1 and -2 and the activation and potentiation of NK cell activity against VEE virus.

Molecular localization of abortive infection of resident peritoneal macrophages by herpes simplex virus type 1

Mononuclear phagocytes exhibit different patterns of intrinsic resistance to herpes simplex virus type 1 (HSV-1) that are related to the heterogeneity of macrophage populations and may reflect the particular differentiation or maturation state of the macrophages. In this study, we characterized the molecular basis for the block in HSV-1 replication in resident peritoneal macrophages from B6C3F1 mice. Infected resident peritoneal macrophages were analyzed for the presence of virus-specific mRNA by Northern (RNA) blotting and in situ hybridization and for proteins by immunofluorescence. The data were compared with those obtained in HSV-1-infected permissive Vero cells. The immediate-early genes ICP4, ICP0, ICP22, and ICP27 were transcribed in resident peritoneal macrophages, as was the early gene tk. Virus-specific mRNA for the major DNA-binding protein ICP8 was barely detectable, and that for another early gene, the viral DNA polymerase, was not detected. In addition, transcripts for the delayed-early gene glycoprotein D and the true late gene glycoprotein C (gC) were not detectable in resident peritoneal macrophages. In situ hybridization and immunofluorescence studies confirmed that transcripts and proteins for the immediate-early and some early HSV-1 genes were present. These data also established that 14% of the resident peritoneal macrophages were positive for RNA and polypeptide specific for the immediate-early gene ICP4 and that 7 to 11% were positive for RNA or polypeptides specific for the early genes tk and ICP8. The fact that only a few cells expressed viral products emphasizes the heterogeneity that exists even in this relatively homogeneous resident peritoneal macrophage population. Consistent with the Northern blot analysis, no RNA specific for the early DNA polymerase gene or the late gC gene was detected by in situ hybridization nor could the polypeptide for the gC gene be seen by immunofluorescence. Thus, while early transcriptional events were initiated in some resident peritoneal macrophages, there was a block in replication localized at the level of expression of the early to delayed-early viral genes.

Trichloroethylene cranial neuropathy: is it really a toxic neuropathy or does it activate latent herpes virus?

The mechanism of the cranial neuropathy associated with heavy exposure to trichloroethylene (or dichloroethylene) is unknown. In severe cases there is destructive spread of the neuropathic process from the Vth cranial nerve nuclei up and down the brain stem in a manner that is difficult to explain on accepted neurotoxicological principles. However, there is a close association reported of this form of trigeminal neuropathy with reactivation of orofacial herpes simplex that suggests the possibility that the chemical, which readily gains entrance into the nervous system, may be responsible for reactivating the latent virus. This novel hypothesis is discussed in the light of current understanding of latency in herpes simplex infection in nervous tissue.

Host cell resistance to mouse hepatitis virus type 3 is expressed in vitro in macrophages and lymphocytes

Phenotypic expression of in vivo sensitivity to mouse hepatitis virus type 3 (MHV3) was studied in vitro in macrophages and lymphocytes. MHV3 infections were induced in peritoneal exudate (PE), nonadherent spleen (NAS) and thymus (THY) cells from resistant A/J, susceptible C57BL/6 or semisusceptible (C57BL/6xA/J)F1 mice. Differences in cytopathic effect, cell viability and virus titers were found only at 48 hrs postinfection (p.i.). "Carrier state" infections were performed at 48 hrs p.i. by transfer of supernatants of infected cells to newly collected cells originating from the same strain of mice. A passage-dependent restriction of viral replication was detected in vitro and was expressed in PE, NAS and THY cells as a recessive phenotype. No defective-interfering viral particles were involved in the restriction of viral replication. Results obtained with crossed infections and determination of the number of productively infected cells demonstrated that restriction of viral replication in macrophages and lymphoid cells from resistant A/J mice is controlled by a genetically-determined intrinsic cellular mechanism acting principally on the level of production of infectious viral particles by the infected cell.

HSV-1 DNA sequence determining intraperitoneal pathogenicity in mice is required for transcription of viral immediate-early genes in macrophages

The relationship between intraperitoneal (ip) pathogenicity in vivo of herpes simplex virus type 1 (HSV-1) and infection of macrophages (m phi) in vitro was studied. The apathogenic HSV-1 strain HFEM disappeared from the peritoneum of infected mice following ip inoculation, while the pathogenic F strain persisted in the peritoneum and penetrated the mouse nervous system, and eventually the mice died, showing severe neurological signs. When peritoneal m phi were infected in vitro, a direct correlation with pathogenicity in vivo was found with several HSV-1 strains and recombinants. HSV-1 strains (F, KOS, R-M1C1) which were pathogenic for mice by the ip route, induced cytopathic effect (CPE) in m phi in vitro. Strain F transcribed viral immediate-early genes and synthesized viral DNA in m phi that were treated with L-cell conditioned medium (as a source of colony-stimulating factor) prior to infection. Apathogenic HSV-1 strains (HFEM, R-15, R-19) did not cause CPE in m phi. The HFEM strain was already blocked in the transcription of viral alpha genes in the infected m phi, but replicated well in control BSC-1 cells. An intratypic recombinant (R-M1C1), produced by cotransfection of HFEM DNA with a cloned Mlul-Mlul DNA fragment (coordinates 0.7615-0.796) from HSV-1 strain F, that was shown [Becker et al. (1986). Virology 149, 255-259] to have regained partial ip virulence for mice, now transcribed alpha genes, synthesized viral DNA, and induced CPE in m phi. It appears that the viral DNA fragment responsible for ip virulence is involved in tissue-specific recognition of virus by infected m phi, a function necessary for transcription of viral alpha genes.

Antibody-mediated growth of influenza A NWS virus in macrophagelike cell line P388D1

We investigated the internalization and growth of influenza A NWS virus in macrophagelike P388D1 cells. Flow cytometric analysis using fluorescein isothiocyanate-labeled virus showed that the attachment of normal rabbit serum-exposed virus (NS-V) to neuraminidase (NA)-treated cells was noticeably limited compared with that to untreated cells. However, rabbit antiserum-exposed virus (AS-V) could attach equally well to both cells. Virus coated with Fab prepared from antiviral immunoglobulin G could not attach. These data suggest that the NWS virus can infect P388D1 cells in one of two ways, via viral or via Fc receptors, depending on the presence of antibodies. The NS-V could grow in the untreated cells, but not in the NA-treated cells. The highest growth of AS-V in the NA-treated cells was observed at an antibody concentration showing 50% plaque reduction titer. Growth was exponentially decreased toward the lower and higher dilutions of antibodies. By using three different immunoglobulin G subclasses of monoclonal antibodies against hemagglutinin, it was demonstrated that both Fc receptors I and II could take part in this phenomenon. The presence of 20 mM NH4Cl inhibited the growth of both AS-V and NS-V, suggesting that the intracellular pathways after internalization via Fc or viral receptors are similar. These data indicate that the concentration of antibodies has a critical role on the antibody-mediated growth of influenza virus in macrophages.

Possible neural basis for age-dependent resistance to neurologic disease from herpes simplex virus

Twenty-week-old mice are known to be resistant to HSV induced neurologic disease, while 5-week-old mice are susceptible. Although age-dependent resistance to disease has been attributed to immunologic maturation, most immunologic development is complete by about 3 weeks of age. We, therefore, postulated that differences in neural spread were involved and we compared the pathogenesis of viral spread in 5-week- and 20-week-old mice. Following footpad infection with 10(5.3) PFU HSV-1, virus was detected in homogenates of sciatic nerve and spinal cord 3-4 days sooner in 5-week-old versus 20-week-old mice. Virus titers in footpad homogenates were 10(5.2) to 10(6.0) in both groups, thus differences in virus replication or immunologic restriction at the initial site of infection could not account for the difference in neural spread. The rate of virus spread to the dorsal root ganglia (DRG) was assessed by ganglia explant/co-cultivation to detect virus presence at various times after footpad infection and by measuring sciatic nerve length. In 5- and 20-week-old mice the rate of virus spread to DRG was 28 mm/day and 4-12 mm/day respectively. We conclude that neural uptake and/or transport of virus may contribute to the difference in susceptibility to neurologic disease.

Role of interferon in persistent infection of macrophages with herpes simplex virus

Splenic macrophage cultures from C57BL/6 mice resistant to infection with herpes simplex virus (HSV) in vivo survived HSV infection in vitro. In contrast, macrophages from HSV-susceptible DBA/2 mice were completely lysed by the virus. During prolonged culturing, macrophages from C57BL/6 mice continued to produce infectious virus, indicating establishment of a persistent infection. At this time, interferon (IFN) was undetectable. However, as shown directly by the addition of an anti-IFN serum and indirectly by an increased activity of (2'-5')oligoadenylate synthetase, IFN was involved in the maintenance of the persistent infection. During the acute phase of virus infection, viral DNA replication was identical in macrophages from resistant or susceptible mice. Later, viral DNA content and the number of cells expressing HSV antigens decreased in macrophages from C57BL/6 mice. However, single cells remained to express viral proteins and to produce infectious particles. The results show that macrophages can be persistently infected with HSV due to their genetically controlled properties.

Genetic and biological analyses of a herpes simplex virus intertypic recombinant reduced specifically for neurovirulence

RS6 is a herpes simplex virus intertypic recombinant derived from type 1 strain 17 syn+ and type 2 strain HG52. With a 50% lethal dose of about 10(5) PFU after intracerebral inoculation of mice, RS6 was approximately 100,000 times less neurovirulent than either of its wild-type parental viruses were. When compared with strains 17 syn+ and HG52, RS6 replicated intermediately in primary mouse embryo fibroblasts in vitro at 38.5 degrees C (mouse temperature) and to wild-type peak titers in mouse feet in vivo. In contrast, following intracranial inoculation of mice, RS6 replicated significantly less well than did either of its parental viruses in brains. The genetic defect(s) responsible for the reduced neurovirulence of RS6 was stable after in vitro and in vivo serial passage, was not manifested as temperature-sensitive plaquing in vitro, and did not affect thymidine kinase expression. These data indicate that RS6 has a genetic defect(s) specifically affecting its ability to replicate in the mouse brain. Using marker rescue technologies, we increased the neurovirulence of RS6 and localized one genetic determinant(s) involved with the reduced neurovirulence of this agent to 0.72 to 0.87 map units (and, tentatively, to 0.79 to 0.83 map units) of the herpes simplex virus genome. When coupled with the work suggesting that thymidine kinase expression is essential for efficient replication in nerve tissues and earlier reports from this laboratory and others, the results presented in this study indicate that more than one herpes simplex virus gene is involved with neurovirulence.

Differential sensitivity of cultured retinal neurons and photoreceptors to herpes simplex infection

Infection of the retina with herpes simplex virus type 1 (HSV-1) causes devastating lesions usually leading to blindness. However, the interactions between individual retinal cell types and this virus have not been well characterized, probably because of limitations posed by the complexity of the intact retina. We have now approached this problem through the use of separate, purified populations of isolated chick embryo retinal neurons and photoreceptor cells, of glial cells, and of pigmented epithelial cells. This manuscript deals with the initial part of these studies, aimed at determining the susceptibility of different retinal types to HSV-1 infection. The different cultures were exposed to HSV-1 for 3-48 hr, and cell infection was evaluated by immunocytochemical detection of viral antigens or by autoradiographic study of viral DNA replication. Practically 100% of the retinal glial cells and pigmented epithelial cells appeared susceptible to HSV-1 infection. On the other hand, as many as 70% of the neurons present in glia-free, pigment epithelium-free cultures, also appeared infected after a 24-hr exposure to the virus. Neuronal susceptibility to HSV-1 was already present in early (2-day) cultures, was time- and concentration-dependent, and led to neuronal degeneration after 24-48 hr. Neuronal infection was also corroborated by the detection of viral particles by transmission electron microscopy. Photoreceptor cells were consistently and selectively resistant to HSV-1 infection at all the concentrations and time points investigated. Both immunocytochemical and autoradiographic studies showed similar results. Photoreceptor resistance to HSV-1 appears to be selective, since they could be readily infected with RNA viruses such as vesicular stomatitis virus and influenza virus. These cell culture preparations offer an attractive system for the investigation of cellular mechanisms involved in the differential susceptibility of retinal cells to viral infection. Moreover, they could also help in the screening of treatments potentially capable of preventing and (or) curing HSV-induced retinal infection.

Interactions between herpes simplex virus and murine bone marrow macrophages

Macrophages from murine bone marrow (strain C3Hf Bu/Kam) were cultured in vitro in L-cell conditioned medium. After 0, 2, 4, 6, 8 and 10 days, they were infected with a clinical strain of herpes simplex virus type 1 and the outcome followed morphologically, by phagocytic index, infectious virus yields, immunofluorescence, expression of Fc receptors and major histocompatibility complex (MHC) Class II antigens. At a multiplicity of infection of 1-5, little morphological difference was apparent between infected and uninfected cultures at early stages in vitro but marked changes occurred later with reduction in cell numbers in the infected cultures. Indirect immunofluorescence failed to detect cells expressing early viral antigens, and yields of infectious virus indicated that permissive infection was not taking place. While phagocytic index and Fc receptor expression did not change 24 hours post-infection, MHC Class II antigen expression was increased. Thus, although the bone marrow macrophages seem predominantly resistant to infection with HSV-1, they may be modified by the presence of the virus. Since macrophages may act as antigen presenting cells for the immune system, this type of mechanism may be important in the generation of local immune responses.

Suppression of MHV3 virus-activated macrophages by dieldrin

Dieldrin (36 mg/kg body weight) administered intraperitoneally prolonged recovery from infection with mouse hepatitis virus 3 (MHV3) in the genetically-resistant A/J strain, affected the humoral anti-MHV3 IgG immune response, and inhibited the intrinsic antiviral activity of peritoneal macrophages upon in vitro rechallenge with the virus. Infection of untreated A/J animals and vehicle controls with MHV3 resulted in marked and reproducible activation of peritoneal macrophages, observed in vitro as resistance to MHV3-cytopathic effects 48 hr after rechallenge with the virus, whereas exposure to dieldrin resulted in apparent loss of the intrinsic capacity of cells to restrict replication of MHV3 and to protect them from cytolysis. In addition, in vitro treatment of MHV3 virus-activated macrophages with dieldrin, mitomycin C and X-irradiation, inhibited the intrinsic capacity of cells to restrict MHV3 replication. This mechanism of cellular restriction of the virus by MHV3-activated macrophages from the resistant A/J strain appeared to be one of the sensitive targets for the suppressive action of dieldrin on host resistance, as no major changes in macrophage cellular parameters were observed in in vitro studies of cell viability, adherence to plastic, and superoxide anion generation; the increased cell yield in the peritoneal exudates during MHV3 virus infection was not affected by dieldrin exposure; and the attachment and uptake of [3H]MHV3 by virus-activated macrophages was shown to be unchanged by dieldrin exposure.

Demonstration of suppressor cells in coxsackievirus group B, type 3 infected female Balb/c mice which prevent myocarditis

Coxsackievirus group B type 3 (CVB3) induces myocarditis in male Balb/c mice but produces little cardiac injury in females. Males develop cytolytic T lymphocytes (CTL) reactive to heart antigens which primarily cause the inflammation and cardiac injury observed in the disease. Infected female mice lack this CTL response because they rapidly produce suppressor cells inhibiting both cellular immunity and cardiac inflammation. Four lines of evidence demonstrate suppressor cells in females. First, females develop myocarditis when treated with low-dose cyclophosphamide under conditions known to preferentially eliminate suppressor cells but not other immune cells. Second, lymphocytes obtained from females at various times after infection prevent myocarditis when adoptively transferred into CVB3-infected males. Virus concentrations in the hearts of males receiving immune female cells and control males were equivalent. Thus protection did not result from accelerated virus elimination in recipient males. Third, CTL from CVB3 infected male mice could induce myocarditis in infected T-lymphocyte depleted but not in intact females suggesting the presence of an inhibitory T cell in the intact animals. Finally, male lymphocytes cultured on heart cell monolayers for 5 days generate significant cytolytic activity to myocyte targets. CTL generation could be inhibited by co-culture of the male cells with immune female lymphocytes. Nonimmune female cells were not inhibitory.

An acidic lymphokine distinct from interferon-gamma inhibits the replication of herpes simplex virus in human pulmonary macrophages

Supernatants from concanavalin A-stimulated human peripheral blood mononuclear cells were fractionated by gel filtration and isoelectric focusing. A fraction with an isoelectric point of 2.2-3.3 containing macrophage migration inhibition factor activity inhibited the replication of herpes simplex virus type 1 in human pulmonary macrophages and U937 cells. This fraction did not inhibit the replication of herpes simplex virus in human fibroblasts. Moreover, the ability of this lymphokine fraction to inhibit viral growth in macrophages was not neutralized by antibody against interferon-gamma. These findings identify a macrophage specific antiviral lymphokine which is distinct biochemically and immunologically from interferon-gamma.

Production of soluble suppressor factors by herpes simplex virus-stimulated splenocytes from herpes simplex virus-immune mice

Indirect evidence indicates that herpes simplex virus (HSV)-specific cytotoxic-T-lymphocyte induction is regulated by suppressor cells. To search for such suppressor effects, supernatant fluids from splenocyte cultures from normal and HSV-immune mice cultured either with or without viral stimulation were tested for their ability to inhibit HSV-specific cytotoxic-T-lymphocyte induction. Only the supernatant fluid from the HSV-stimulated, HSV-immune cultures contained a suppressor activity (HSV-SF). HSV-SF was produced by nylon-wool-purified Thy 1+ cells. HSV-SF was detectable after 3 days of culture and would only suppress cytotoxic-T-lymphocyte induction if HSV-SF was added within 24 h of initiation of the test cultures. HSV-SF was neither dialyzable nor heat stable. Molecular sieve chromatography of HSV-SF yielded multiple peaks of suppressor activity. Although most of these peaks exhibited nonspecific suppressor activity, the suppression mediated by the 90,000 to 150,000-molecular-weight fractions was antigen specific and genetically restricted. These results provide direct evidence for the regulation of HSV-cytotoxic-T-lymphocyte induction by a novel suppressor factor.

Direct inactivation of viruses by MCP-1 and MCP-2, natural peptide antibiotics from rabbit leukocytes

Six homologous peptides were purified to homogeneity from rabbit granulocytes or alveolar macrophages and tested for their ability to inactivate herpes simplex virus type 1 (HSV-1). Two of the peptides, MCP-1 and MCP-2, showed considerable in vitro neutralizing activity, whereas four structurally homologous peptides (NP-3a, NP-3b, NP-4, and NP-5) were relatively ineffective. Inactivation of HSV-1 by MCP-1 or MCP-2 depended on peptide concentration and on the time, temperature, and pH of the incubation. HSV-2, vesicular stomatitis virus, and influenza virus A/WSN were also susceptible to direct neutralization by MCP-1 or MCP-2, whereas cytomegalovirus, echovirus type 11, and reovirus type 3 were not. We speculate that MCP-1 and MCP-2, peptides that are abundant in rabbit granulocytes and lung macrophages, may contribute to antiviral defenses by mediating the direct inactivation of HSV-1 and selected other viruses.

Macrophage response to herpes simplex encephalitis in immune competent and T cell-deficient mice

Corneal inoculation of Nude (athymic) mice and Balb/c mice with herpes simplex virus Type I produces a brainstem encephalitis with demyelination of the trigeminal root entry zone. The extent of CNS demyelination is less in the immune-deficient athymic mice 7 days after infection compared to the immune-competent Balb/c mice. Both groups demonstrate a macrophage response and beginning myelin disruption approximately 3 days after corneal infection when herpes viral particles are first observed within central nervous system cells. Five to seven days after infection when differences in the extent of demyelination between the immune-competent and immune-deficient animals become evident, the Balb/c mice demonstrate T cells and increasing numbers of macrophages at the trigeminal root entry zones. These findings suggest an interaction between macrophages and T cells which leads to an extension of the demyelination in the immune competent Balb/c mice and that lack of T cells is important in limiting demyelination in Nude (athymic) mice.

Lysis of dengue virus-infected cells by natural cell-mediated cytotoxicity and antibody-dependent cell-mediated cytotoxicity

Peripheral blood mononuclear cells (PBMC) from humans without antibodies to dengue 2 virus lysed dengue 2 virus-infected Raji cells to a significantly greater degree than uninfected Raji cells. The addition of mouse anti-dengue antibody increased the lysis of dengue-infected Raji cells by PBMC. Dengue 2 immune human sera also increased lysis of dengue-infected Raji cells by PBMC. These results indicate that both PBMC-mediated cytotoxicity and antibody-dependent cell-mediated cytotoxicity (ADCC) can cause significant lysis of dengue-infected Raji cells. The lysis of infected Raji cells in the ADCC assay correlated with the dilution of dengue-specific antibody which was added, indicating the dengue virus specificity of the lysis of dengue virus-infected Raji cells. Alpha interferon (IFN alpha) was detected in the culture supernatant of PBMC and dengue-infected Raji cells. However, enhanced lysis of dengue-infected Raji cells by PBMC may not be due to the IFN produced, because neutralization of all IFN activity with anti-IFN alpha antibody did not decrease the lysis of dengue-infected cells, and effector cells pretreated with exogenous IFN alpha also lysed dengue-infected cells to a greater degree than uninfected cells. The effector cells responsible for lysis of dengue virus-infected Raji cells in the natural killer and ADCC assays were analyzed. Nonadherent PBMC caused more lysis than did adherent cells. Characterization of nonadherent cells with monoclonal antibodies showed that the predominant responsible effector cells were contained in OKM1+ and OKT3- fraction in the natural killer and ADCC assays.

Experimental infection of inbred mice with herpes simplex virus. VI. Effect of interferon on in vitro virus replication in macrophages

Peritoneal exudate cells (PEC) of DBA/2 mice, after 7 days of in vitro preculture and consisting of virtually 100 per cent macrophages, were able to support the replication of Herpes Simplex Virus type 1 strain WAL (HSV). Using a standard medium based on Dulbecco's Modified Eagle Medium (D-MEM), no virus replication was observed in freshly isolated PEC. However a medium based on RPMI 1640 consistently yielded higher virus titres in precultured PEC than the D-MEM medium, and also allowed virus replication in freshly isolated PEC. Macrophages derived from the spleens or the bone marrow, and precultured in the same way as PEC represented a highly pure population and were permissive for infection with HSV. Titres of about 10(6) PFU HSV were observed in PEC 48 hours after infection with 10(3) or 10(6) PFU. However, whereas a complete destruction of the cell monolayer was observed 24 hours after infection with 10(6) PFU, complete cytopathogenicity in PEC infected with 10(3) PFU required at least twice this time. In the latter situation, plaque formation was observed 24 hours after infection. PEC of different strains of mice were compared. Of these, PEC of all mice that are susceptible to HSV infection in vivo replicated HSV to the same degree as PEC of DBA/2 mice, whereas PEC of resistant C57BL/6 and C3H/HeJ mice produced 1000 fold lower titres of viral progeny. Whereas the number of infectious centres were equal in PEC of DBA/2 and C57BL/6 mice, the plaques observed after infection of confluent PEC with a low MOI were considerable smaller in cells from C57BL/6 mice. Furthermore, significantly higher titres of interferon were measured in the supernatants of HSV-infected C57BL/6 macrophages than in those of DBA/2 macrophages, and the former were made fully susceptible by the in vitro addition of an anti-interferon serum.

Electron microscopic observations on primary hepatocyte cultures infected with herpes simplex virus types I and II

The replication cycle of the Herpes simplex virus (HSV) strains I and II has so far been described mainly in established proliferative cell cultures. Most of the biochemical data and ultrastructural cell changes regarding the virus-cell interaction have been obtained from 'permissive' cells which allow almost unrestricted viral multiplication. It seems obvious, however, that the in vivo viral infections are not represented adequately by these experiments. In order to achieve a more realistic view of the ultrastructural events during HSV infection of adult tissue, cell cultures were prepared from adult mouse and rat livers and infected with several HSV strains. Established 'permissive' cell lines (BHK and RK cells), served as controls. Although the main principles of viral attachment, replication and release of viral particles, were similar in hepatocytes and proliferating cells, marked differences were observed regarding the better preservation of the nuclear structures, the lower replication rate of viruses, the hypertrophy of the endoplasmic reticulum, and the changes in the Golgi apparatus. Summarizing, it can be stated that hepatocytes infected by HSV in cell culture display the well known general features of adult cells infected by viruses in vivo.

Effects of microwave exposure on the hamster immune system. III. Macrophage resistance to vesicular stomatitis virus infection

Exposure of hamsters to microwave (MW) energy (2.45 GHz, 25 mW/cm2, 1 h) resulted in activation of peritoneal macrophages (PM) to a viricidal state restricting the replication of vesicular stomatitis virus (VSV). The PM from MW-exposed hamsters were viricidal as early as 1 day after exposure and remained active for 5 days. Immunization of hamsters with vaccinia virus induced viricidal PM by 3 to 4 days and they remained active for 7 days. To test the hypothesis that thermogenic MW exposure results in the release of endotoxin across the intestinal epithelium which subsequently activates PM, hamsters were injected with lipopolysaccharide (LPS) and their viricidal activity was studied. Lipopolysaccharide in vitro (0.2 microgram) and in vivo (0.5 microgram) activated macrophages to a viricidal state. When administered in vivo, LPS (0.5 microgram) activated macrophages as early as 1 day and the activity remained for 3 days. While MW exposure of PM in vitro failed to induce viricidal activity, exposure of PM to LPS in vitro induced strong viricidal activity. This suggests that the in vivo response of PM to MW is an indirect one, which is consistent with the hypothesis that MW-induced PM viricidal activity may be mediated via LPS. In preliminary experiments, MW exposure resulted in extended survival time for hamsters challenged with a lethal dose of vesicular stomatitis virus, supporting the concept that MW-activated PM may be a useful therapeutic modality.

Injection of mice with antibody to interferon renders peritoneal macrophages permissive for vesicular stomatitis virus and encephalomyocarditis virus

Vesicular stomatitis virus (VSV) and encephalomyocarditis virus (EMCV) multiply in only a small percentage of peritoneal macrophages freshly explanted from 4- to 6-week-old male or female DBA/2, BALB/c, C3H, C57BL/6, or Swiss mice. However, when these mice were injected intraperitoneally with potent sheep (or goat) anti-mouse interferon alpha/beta globulin 4 days prior to harvesting peritoneal macrophages, the viruses multiplied to high titers and most of the cells were infected, as determined by total virus yield (VSV and EMCV), percentage of VSV antigen-positive cells (immunofluorescence), and determination of VSV infectious centers. This effect was not observed when mice were inoculated with other sheep hyperimmune or normal serum globulins. Anti-interferon globulin appeared to act in vivo because incubation of this globulin with peritoneal macrophages during the period of cell attachment or during the 18 hr after virus absorption did not render these cells permissive for VSV. Injection of mice with anti-interferon globulin did not affect the binding and uptake of labeled VSV by peritoneal macrophages. Although the underlying mechanism of this phenomenon is unknown, the results suggest that there may be low levels of endogenous interferon that contribute to host defense by maintaining some cells in an antiviral state.

Contribution of macrophage arginase in the intrinsic restriction of herpes simplex virus replication in permissive macrophage cultures induced by gamma-interferon containing products of activated spleen cells

Cultured peritoneal macrophages (PM) from adult mice of strain DBA/2 (but not C57BL/6) supported productive replication of HSV, as monitored by infectious virus yield and electron microscopy. In contrast, PM of DBA/2 origin, when pretreated with supernatants of Con A-stimulated spleen cells containing immune interferon (IFN-gamma) activity, manifested remarkable intrinsic restriction to HSV replication. The acquisition of this intrinsic restriction to virus replication correlated with the generation of appreciably elevated levels of arginase in supernate of treated PM. Addition of incremental doses of exogenous arginine in the culture medium led to the abrogation of induced restriction to HSV replication in DBA/2 PM, indicating the critical role of arginase in the phenomenon. Furthermore, anti-HSV activity of arginase levels released into the culture medium of IFN containing supernate-treated PM became apparent when assayed on PM, which were precultured in arginine-deficient medium for 24 hours before virus infection and exposure to arginase containing preparation. Taken together, these observations indicate that macrophage arginase can mediate intrinsic restriction to HSV replication in PM.

Biological characterization of a herpes simplex virus intertypic recombinant which is completely and specifically non-neurovirulent

In this study, a pre-existing "library" of Herpes Simplex Virus (HSV) intertypic recombinants was found to be not useful for mapping HSV genes controlling viral neurovirulence in mice. Most of these agents were significantly less virulent than either parental type following intracranial inoculation, and in the general case this lessened virulence could be attributed to inefficient replication in any cell type at 38.5 degrees (the normal temperature of the mouse). One agent tested (recombinant RE6) was completely non-neurovirulent following intracranial inoculation of as much as 3.2 X 10(7) PFU. Since about 10 PFU of either 17 Syn+ or HG52 (the "parental" strains of this recombinant) were lethal for mice, RE6 is at least 10 million-fold less neurovirulent than the wild-type strains from which it was produced. The function of the defective gene(s) in RE6 is not yet known, but it is not required for the expression of viral thymidine kinase, efficient replication in cultured cells at 38.5 degrees, or replication in non-neural mouse tissue in vivo. Therefore, the defect in RE6 is in an HSV gene function(s) which is absolutely required for neurovirulence but not for general viral replication. Several possibilities for the molecular nature of the defect in RE6 are discussed.

Incomplete growth of varicella-zoster virus in human monocytes

Infection of human peripheral blood monocytes by varicella-zoster virus (VZV) was investigated. When freshly isolated monocytes of young adult volunteers were infected with cell-free VZV and examined by indirect immunofluorescence, specific antigens appeared at 8 hr and the number of antigen-positive cells reached the maximum between 24 and 48 hr postinfection. The proportion of antigen-positive cells to total cells was similar to that of the permissive control (HeLa cells), while very few infectious centers (IC) of monocytes were formed in comparison with the infected control cells. Monocytes isolated from infants and old persons formed a larger number of IC than those of young adults. Electron microscopic study of VZV-infected monocytes from three young adult volunteers demonstrated that the proportion of VZV particle-positive cells to total cells was similar to that of antigen-positive cells, and most of the particles seen in the nuclei were low in density and lacked a central core. These results suggest that the growth of VZV in human adult monocytes is incomplete. This restriction of VZV growth by monocytes may play an important role in defense against VZV infection.

Replication at body temperature selects a neurovirulent herpes simplex virus type 2

A prototype strain of herpes simplex virus type 2 (HG-52) replicated at 31 degrees C was avirulent when inoculated intracranially into mice. This property was not altered after serial passage of the agent at 31 degrees C, but the virus became virulent after passage at 37.5 degrees C. The selection was not merely for an agent which replicated more efficiently at the higher temperature, but for viruses with enhanced capacity to replicate in the brains of mice. Virulent descendants of plaque-purified avirulent stocks were obtained in each instance attempted.

Genetic variability of herpes simplex virus: development of a pathogenic variant during passaging of a nonpathogenic herpes simplex virus type 1 virus strain in mouse brain

Herpes simplex virus type 1 ANG (HSV-1 ANG) is originally nonpathogenic for inbred mice upon intraperitoneal intravenous, or intravaginal inoculation. In contrast, mice died of encephalitis within 4 to 5 days after intracerebral inoculation with this strain. HSV-1 ANG was serially passaged in mouse brains. In two independent series, peripherally pathogenic virus variants had developed and accumulated in the virus progeny after 12 to 15 intracerebral passages. In mixed infections both nonpathogenic and pathogenic viruses replicated at the primary site of infection and spread to various organs. However, only the pathogenic phenotype could be recovered from the spinal cord and the brain. Comparison of the restriction enzyme cleavage patterns of pathogenic ANG and nonpathogenic ANG virus DNAs revealed distinct alterations in the S-segment (US) sequences bounded by coordinates 0.953 and 0.958 in the prototype orientation and by coordinates 0.862 to 0.867 in the IS orientation of the viral genome. However, it is not known whether these alterations are physiologically relevant to the observed changes in pathogenicity. When coinjected intraperitoneally at 50 to 100-fold excess, the nonpathogenic HSV-1 ANG protected mice against its own pathogenic variant as well as against other pathogenic HSV-1 strains. Pathogenic HSV-1 ANG proved to be genetically and phenotypically stable for at least 25 serial passages in tissue culture at either high or low multiplicity of infection.

Early interactions of herpes simplex virus with mouse peritoneal macrophages

Adsorption of herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) to resident peritoneal macrophages (PM) of 4-week-old Swiss albino (SA) and GR/AFib mice was studied. A significantly (P less than 0.05) higher HSV-2 adsorption rate was found with PM of SA mice than with PM of GR/AFib mice. Of added HSV-2 65% bound to the cells of SA mice over a 120-min period versus 15% to PM of GR/AFib mice. Only 15 to 20% of added HSV-1 bound to PM regardless of the mouse strain. These patterns of adsorption were found with all four HSV-1 and four HSV-2 strains tested. Pretreatment of PM with an HSV-2 mutant blocked the adsorption of added HSV-2. Thus, the receptors for HSV attachment seemed to be virus type selective. To avoid masking of adsorption by phagocytotic activity, the adsorption studies had to be performed at 4 degrees C. Transport of attached HSV-1 and HSV-2 to the nuclei of SA PM was studied with purified virus labeled with 32Pi and [3H]thymidine. In double-isotope experiments, only transport of HSV-2 was detected. The possible importance of differences in density or avidity of virus-binding receptors on the plasma membrane of PM is discussed in relation to macrophage-dependent focal liver necrosis, which was only demonstrable after intraperitoneal inoculation of HSV-2, not HSV-1, only in SA, not GR/AFib, mice.

Inhibition of herpes simplex virus multiplication by activated macrophages: a role for arginase?

Proteose-peptone-activated mouse macrophages can prevent productive infection by herpes simplex virus in neighboring cells in vitro whether or not those cells belong to the same animal species. The effect does not require contact between the macrophages and the infected cells, may be prevented by adding extra arginine to the medium, and may be reversed when extra arginine is added 24 h after the macrophages. Arginase activity was found both intracellularly and released from the macrophages. The extracellular enzyme is quite stable; 64% activity was found after 48 h of incubation at 37 degrees C in tissue culture medium. No evidence was found that the inefficiency of virus replication in macrophages was due to self-starvation by arginase. As might be predicted macrophages can, by the same mechanism, limit productive infection by vaccinia virus.