Interferon production by mouse leukocytes in vitro and in vivo

CIRCULATING INTERFERON IN MICE AFTER INTRAVENOUS INJECTION OF VIRUS

Circulating interferon was detectable in mouse serum within 1 hour after the intravenous injection of various types of virus and it reached maximum levels in about 4 hours. Rapidly produced interferon may play a role in the pathogenesis of viral infection and in viral interference.

LEUKOCYTES AND INTERFERON IN THE HOST RESPONSE TO VIRAL INFECTIONS. I. MOUSE LEUKOCYTES AND LEUKOCYTE-PRODUCED INTERFERON IN VACCINIA VIRUS INFECTION IN VITRO

1. Investigation of the role of leukocytes in vaccinia virus infection is reported in an in vitro model, in the absence of an immune response. 2. Mouse leukocytes were shown to be capable of inhibiting the progression of vaccinia virus infection in primary mouse embryo fibroblast cultures. The degree of protection varied from slowing of spread of infection to complete control of the infection with eventual elimination of detectable virus and recovery of the culture. 3. Interferon production by leukocytes is thought to be an important factor in the observed protective effect.

Poxvirus pathogenesis

Poxviruses are a highly successful family of pathogens, with variola virus, the causative agent of smallpox, being the most notable member. Poxviruses are unique among animal viruses in several respects. First, owing to the cytoplasmic site of virus replication, the virus encodes many enzymes required either for macromolecular precursor pool regulation or for biosynthetic processes. Second, these viruses have a very complex morphogenesis, which involves the de novo synthesis of virus-specific membranes and inclusion bodies. Third, and perhaps most surprising of all, the genomes of these viruses encode many proteins which interact with host processes at both the cellular and systemic levels. For example, a viral homolog of epidermal growth factor is active in vaccinia virus infections of cultured cells, rabbits, and mice. At least five virus proteins with homology to the serine protease inhibitor family have been identified and one, a 38-kDa protein encoded by cowpox virus, is thought to block a host pathway for generating a chemotactic substance. Finally, a protein which has homology with complement components interferes with the activation of the classical complement pathway. Poxviruses infect their hosts by all possible routes: through the skin by mechanical means (e.g., molluscum contagiosum infections of humans), via the respiratory tract (e.g., variola virus infections of humans), or by the oral route (e.g., ectromelia virus infection of the mouse). Poxvirus infections, in general, are acute, with no strong evidence for latent, persistent, or chronic infections. They can be localized or systemic. Ectromelia virus infection of the laboratory mouse can be systemic but inapparent with no mortality and little morbidity, or highly lethal with death in 10 days. On the other hand, molluscum contagiosum virus replicates only in the stratum spinosum of the human epidermis, with little or no involvement of the dermis, and does not spread systemically from the site of infection. The host response to infection is progressive and multifactorial. Early in the infection process, interferons, the alternative pathway of complement activation, inflammatory cells, and natural killer cells may contribute to slowing the spread of the infection. The cell-mediated response involving learned cytotoxic T lymphocytes and delayed-type hypersensitivity components appears to be the most important in recovery from infection. A significant role for specific antiviral antibody and antibody-dependent cell-mediated cytotoxicity has yet to be demonstrated in recovery from a primary infection, but these responses are thought to be important in preventing reinfection.

Poxvirus pathogenesis

Poxviruses are a highly successful family of pathogens, with variola virus, the causative agent of smallpox, being the most notable member. Poxviruses are unique among animal viruses in several respects. First, owing to the cytoplasmic site of virus replication, the virus encodes many enzymes required either for macromolecular precursor pool regulation or for biosynthetic processes. Second, these viruses have a very complex morphogenesis, which involves the de novo synthesis of virus-specific membranes and inclusion bodies. Third, and perhaps most surprising of all, the genomes of these viruses encode many proteins which interact with host processes at both the cellular and systemic levels. For example, a viral homolog of epidermal growth factor is active in vaccinia virus infections of cultured cells, rabbits, and mice. At least five virus proteins with homology to the serine protease inhibitor family have been identified and one, a 38-kDa protein encoded by cowpox virus, is thought to block a host pathway for generating a chemotactic substance. Finally, a protein which has homology with complement components interferes with the activation of the classical complement pathway. Poxviruses infect their hosts by all possible routes: through the skin by mechanical means (e.g., molluscum contagiosum infections of humans), via the respiratory tract (e.g., variola virus infections of humans), or by the oral route (e.g., ectromelia virus infection of the mouse). Poxvirus infections, in general, are acute, with no strong evidence for latent, persistent, or chronic infections. They can be localized or systemic. Ectromelia virus infection of the laboratory mouse can be systemic but inapparent with no mortality and little morbidity, or highly lethal with death in 10 days. On the other hand, molluscum contagiosum virus replicates only in the stratum spinosum of the human epidermis, with little or no involvement of the dermis, and does not spread systemically from the site of infection. The host response to infection is progressive and multifactorial. Early in the infection process, interferons, the alternative pathway of complement activation, inflammatory cells, and natural killer cells may contribute to slowing the spread of the infection. The cell-mediated response involving learned cytotoxic T lymphocytes and delayed-type hypersensitivity components appears to be the most important in recovery from infection. A significant role for specific antiviral antibody and antibody-dependent cell-mediated cytotoxicity has yet to be demonstrated in recovery from a primary infection, but these responses are thought to be important in preventing reinfection.

Beta interferon production in primed and unprimed cells infected with human cytomegalovirus

Human cytomegalovirus induced beta interferon in cultures of human foreskin cells. The inhibitor was first released between 8 and 16 hours after infection, about 48 hours before progeny virus. In cultures infected with low concentrations of virus, interferon was produced as the infection spread, and then in amounts larger than expected. After infection with cytomegalovirus, cells which had been primed for 48 hours with purified beta interferon produced significantly more interferon than unprimed cells, and the interferon was produced earlier, between 2 and 8 hours after infection. CMV-induced interferon also was able to prime cells. The data suggest that the relatively large quantities of interferon detected in cultures infected with low concentrations of cytomegalovirus result from endogenous priming: those cells infected early first produce interferon which primes uninfected cells, then virus which induces the primed cells to produce interferon in relatively high concentrations.

Vaccinia virus proteins on the plasma membrane of infected cells. III. Infection of peritoneal macrophages

Primary macrophage cultures were prepared from the peritoneal exudate cell population harvested from mice challenged intraperitoneally with saline, thioglycollate, or vaccinia virus. Vaccinia virus was adsorbed and penetrated into primary macrophages and L-cells with similar kinetics. As evidenced by the expression of some "early" virus-specified proteins, partial uncoating and activation of the virion-associated DNA-dependent RNA polymerase occurred in the infected macrophages. Subsequently, the viral replication cycle in macrophages was aborted; with time after infection, viral DNA and virion proteins initially associated with infected cells could be detected in an acid-soluble form in the medium harvested from infected macrophage cultures. The results suggest that at the time that the final stages of virus uncoating should have occurred, intracellular subviral particles were, instead, degraded in the infected, primary macrophages. Viral DNA synthesis could not be measured in vaccinia virus-infected macrophages, no "late" virus functions were expressed, and progeny virions were not assembled. As measured by the binding of antiviral-antibody-125I-protein A complexes to the surface of vaccinia virus-infected cells, the expression of virus-specified antigens on the surfaces of infected macrophages was significantly reduced and never exceeded that measured at 2 hr after infection on the surfaces of infected L-cells. The expression of virus-specified polypeptides with mol mass of 48-50, 45-46, 36-37, and 25 kDa on the plasma membranes of vaccinia virus-infected, thioglycollate-elicited macrophages, rendered the infected macrophages susceptible to lysis by vaccinia virus-specific cytotoxic T-cells.

Interferon production by leukocytes infiltrating the lungs of mice during primary influenza virus infection

Lung fluids and leukocytes were obtained from unprimed C3H mice by transpleural lavage at intervals after infection with influenza A/Hong Kong/68 virus and were tested for interferon activity. Lavage fluid interferon titers correlated directly with lung virus titers and with initial increases in leukocyte yields from infected lungs. In contrast to cultured lymph node cells from infected animals or leukocytes from lungs of uninfected mice, washed leukocytes obtained from the lungs of mice infected 2 to 6 days earlier produced interferon spontaneously in culture. The physiochemical, biological, and antigenic properties of both the interferon in lavage fluids and that produced by lung lavage leukocytes were similar and characteristics of alpha interferon. Fractionation studies indicated that macrophages and T lymphocytes were primarily responsible for the interferon produced in culture. The early presence and significant numbers of interferon-producing leukocytes in infected lungs suggests that these cells have an early role in defense against influenza virus infection.

Immune interferon produced to high levels by antigenic stimulation of human lymphocytes with influenza virus

Influenza virus stimulation of human lymphocytes induced high levels of immune interferon in lymphocyte cultures. The lymphocytes of normal adults produced approximately 1,000 U/10(6) cells, which was in large part gamma interferon. The lymphocytes of individuals recently vaccinated yielded very high levels (10-50,000 U/10(6) cells) of interferon. The interferon was pH 2 labile, and was not neutralized by antisera to alpha or beta interferon. It did not bind to a monoclonal antibody to alpha interferon, and after partial purification it had characteristics identical to human gamma interferon induced by phytohemagglutinin. The highest yields were produced by treatment of stimulator cells with live virus. Stimulation by whole inactivated virus resulted in lower levels of interferon, and purified hemagglutinin did not induce interferon. The antigen responsible for stimulating the lymphocyte response and interferon induction is a cross-reactive determinant present on all human and non-human influenza viruses tested.

Phenotypic change of an SV40-transformed mouse macrophage line, BB-W-531-2 induced by different cultural methods

A simian virus 40 (SV40)-transformed macrophage clone which was established from BALB/cAnN mouse bone marrow cells was used to study the effect of different cultural conditions on the expression of macrophage properties. The macrophage clone, BB-W-531-2 line, expressed and maintained the macrophage properties, immune phagocytosis of Fc- and complement receptors, under the growth-inhibiting conditions of confluent density and of cultivation on bacteriologic dishes with reduced adhesiveness. However, the cells lost their ability to express the macrophage properties dependent upon cell density after repeated culture splits in the growing phase. These cells regained that ability when they were cocultured with cells having macrophage properties. These results suggest that there is a possible correlation between reduced multiplication and the expression of macrophage properties, and that macrophage properties which have been suppressed or blocked may be induced by diffusible factor(s) produced by macrophages.

Production of interferon by an SV40-transformed macrophage line, BB-W-531-2

A simian virus 40-transformed mouse macrophage line, BB-W-531-2, was examined for its ability to produce interferon. BB-W-531-2 cells showed a phenotypic change between the macrophage and the nonmacrophage states. A viral inhibitor (interferon) was produced by the cells during the phenotypic change from the nonmacrophage to the macrophage state. Cells having macrophage properties were well capable of producing interferon when they were stimulated with ultraviolet-inactivated vaccinia virus, lipopolysaccharide, a streptococcal preparation (OK-432) or polyinosinate . polycytidylate. In contrast, cells that had lost their macrophage properties did not produce interferon even when they were given the same treatments as the cells having macrophage properties. The results suggest that the ability of BB-W-531-2 cells to produce interferon is associated with the expression of several macrophage properties.

Induction of interferon and erythropoietic differentiation in cells transformed by Friend virus

Two lines of Friend virus (FV)-transformed mouse spleen cells have been analyzed in respect to their interferon production capacity: neither F4 cells, which liberate infectious FV when kept under tissue culture conditions, nor the thymidine kinase-deficient B8 cells, which do not produce significant amounts of FV, release detectable amounts of autogenous interferon into cell supernatants. However, interferon is produced in these cells in amounts comparable to that in L-929 cells when interferon induction is initiated with UV-inactivated Newcastle disease virus. Conversely poly(I)-poly(C), a potent interferon inducer in L-929 cells, proved ineffective in this capacity in F4 or B8 cells. When erythropoietic differentiation is induced in these cells by dimethyl sulfoxide, no autogenous interferon production occurs, but with NDV-induction a four- to fivefode increase of interferon production is observed. A similar elevation of interferon production is achieved during 5-bromodeoxyuridine stimulation of differentiation in the thymidine kinase-deficient B8 cells. The refractiveness against poly(I)-poly(C) displayed in unstimulated cells is not overcome at any stage of differentiation, indicating major differences of Newcastle disease virus and poly(I)-poly(C) induction mechanisms.

Effect of Corynebacterium acnes on interferon production in mice

Exposure to Corynebacterium acnes, the most prominent member of our normal skin flora, produces stimulation of lymphoid tissue and certain reticuloendothelial system functions, as well as the immune response. Alteration of the host response is extended by these studies to include changes in the pattern of interferon production in response to a representative group of inducing agents. Serum interferon levels induced by the injection of endotoxin in mice are enhanced, whereas interferon production after injection of Newcastle disease virus, Chikungunya virus, and polyinosinic:polycytidylic acid is depressed in animals inoculated with viable or nonviable C. acnes organisms.

Selective increase in lymphocyte interferon response to vaccinia antigen after revaccination

Viral antigen prepared by heat inactivation of vaccinia virus stimulated production of interferon in association with transformation of sensitized human lymphocytes in vitro. Involvement of a macrophage-lymphocyte interaction in production of interferon stimulated by viral antigen was found in which macrophage greatly augmented the amount of interferon produced by lymphocytes. Reimmunization with live vaccinia virus resulted in a selective increase in the ability of lymphocytes to produce interferon in the presence of viral antigen 4-7 weeks later without a corresponding increase in the degree of already significant lymphocyte transformation. There was no correlation between the extent of lymphocyte transformation and the amount of interferon produced. The augmented interferon response after reimmunization described in this study may be a significant component of the protective effect of immunization with vaccinia against disease occurring after exposure to small-pox.

Transformation of mouse macrophages by simian virus 40

Studies were undertaken to prove that simian virus 40 (SV40) can transform the mouse macrophage, a cell type naturally restricted from deoxyribonucleic acid (DNA) replication. Balb/C macrophages infected with SV40 demonstrated T-antigen production and induced DNA synthesis simultaneously. In the absence of apparent division, these cells remained T antigen-positive for at least 45 days. SV40 could be rescued from nondividing, unaltered macrophages during the T antigen-producing period. Proliferating transformants appeared at an average of 66 days post-SV40 infection. Established cell lines were T antigen-positive and were negative for infectious virus, but yielded SV40 after fusion with African green monkey kidney cells. Their identity as transformed macrophages was substantiated by evaluation of cellular morphology, phagocytosis, acid phosphatase, beta(1c) synthesis, and aminoacridine incorporation.

Specific role of each human leukocyte type in viral infections. I. Monocyte as host cell for vesicular stomatitis virus replication in vitro

Each major leukocyte type of the peripheral blood of healthy donors was studied in vitro for its ability to support vesicular stomatitis virus (VSV) replication. Purified cultures of each white blood cell type were prepared by the selective adsorption and elution of cells from silicone-treated glass beads. It was found that monocytes and macrophages (derived from the rapid transformation of monocytes in vitro) were the principal host cells for VSV replication. Interferon added to mixed leukocyte cultures, prior to virus inoculation, reduced virus yields and prevented destruction of macrophages. Cultures of small lymphocytes, containing no detectable monocytes or macrophages, produced amounts of virus equivalent to 1% of that produced in leukocyte cultures which contained 7% monocytes. Small lymphocytes did not undergo demonstrable cytopathic alterations in virus-infected cultures. VSV neither replicated nor produced cytopathic effects in polymorphonuclear leukocytes.

Effect of polycations on growth and dissemination of the encephalomyocarditis virus in mice

Pathogenicity of the encephalomyocarditis (EMC) virus for adult mice was increased when polycations of diverse type were mixed with virus and inoculated by the subcutaneous or intraperitoneal routes. Diethylaminoethyl (DEAE) dextran, hexadimethrine (polybrene), polymyxin B, polylysine, and calf thymus histone in various concentrations stimulated multiplication of virus in tissues at the injection site and enhanced entry of virus into the blood. The nonpathogenic r(+) variant of EMC which grows locally in tissues but fails to disseminate after subcutaneous and intraperitoneal inoculation was used in most experiments. This virus caused viremia and fatal central nervous system disease only when the polycations were included in the inoculum. DEAE dextran and polybrene stimulated the release of interferon in infected tissues but had no effect in the absence of virus multiplication. Histological studies of tissues from the injection site showed that polycations provoke a mononuclear cell reaction and alter the integrity of connective tissue. However, the mechanism by which the substances enhance virus growth and dissemination was not defined.

Vaccinia gangrenosa and 1-methylisatin 3-thiosemicarbazone (methisazone)

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Rabbit macrophage interferons. I. Conditions for biosynthesis by virus-infected and uninfected cells

Interferon is produced in cultures of rabbit leukocytes in response to infection with Newcastle disease virus or in the absence of known viral infection. The macrophage appears to be the responsible producing cell. Cultures prepared from sterile peritoneal exudates, which contained about 90% macrophages, are at least as efficient as cultures of rabbit kidney (RK) cells in their capacity to synthesize NDV-induced interferon. Interferon can be detected in the medium by 2 hr after viral infection and the titers usually reach a peak of 10,000 PDD(50)/ml by 4-6 hr. Exposure to actinomycin prior to or shortly after viral induction effectively blocks interferon synthesis by cells of both types. However, macrophages become refractory to actinomycin by 30-60 min compared with 607-120 min for RK cells, a finding which suggests earlier and more rapid transcription of interferon-specific messenger RNA in macrophages. Macrophages harvested from the peritioneal cavity of rabbits injected intravenously with NDV 48 hr previously also exhibit slightly reduced capacity to synthesize interferon, but this tolerant state is less marked than is tolerance to production of circulating interferon in intact rabbits. Interferon is also synthesized by rabbit macrophages not infected with virus but simply incubated at 37 degrees C in medium with or without added bacterial endotoxin. Uninfected polymorphonuclear leukocytes, rabbit kidney and spleen cells produced no detectable interferon under similar conditions of cultivation. No interferon was released by intact macrophages incubated at 4 degrees C or by ultrasonically disrupted macrophages incubated at 37 degrees C. Although interferon titers were found to be higher when uninfected cultures were exposed to 10-100 microg/ml of E. coli lipopolysaccharide, unavailability of suitable pyrogen-free maintenance media precluded answering the question whether macrophages can continually synthesize and release interferon spontaneously. Interferon yields from uninfected macrophages were only 1% or less of the yields from NDV-infected macrophages, but the rates of synthesis were similar under both conditions. Studies with actinomycin and puromycin revealed that sequential transcriptive and translational events are required for de novo interferon synthesis by uninfected cells in a manner similar to virus-induced interferon synthesis. The physical properties and molecular weights of these rabbit interferons are discussed in the following report (12).

Interferon in the cerebrospinal fluid of children with central nervous system disorders

Interferon was detected in the cerebrospinal fluid (CSF) of 26 of 51 children with aseptic meningitis, two of 44 with bacterial meningitis, and four of 118 with miscellaneous conditions including encephalitis, convulsive disorders and leukemia with neurological involvement. The geometric mean titre of interferon in mumps meningitis was seven to eight times higher than that in enteroviral meningitis; however, levels of interferon were not related to the concentration of leukocytes in CSF from these patients. Interferon titres were relatively greater at the height of the febrile response in children with mumps meningitis or enteroviral meningitis. There was no association between the presence of interferon in the CSF and the isolation of mumps virus or an enterovirus from the same specimen. Patients frequently developed homologous antibody one to three days after signs of aseptic meningitis, obscuring the relationship of interferon production to clinical improvement.

Virus replication and high-titered interferon production in human leukocyte cultures inoculated with Newcastle disease virus

Wheelock, Frederick E. (Western Reserve University, Cleveland, Ohio). Virus replication and high-titered interferon production in human leukocyte cultures inoculated with Newcastle disease virus. J. Bacteriol. 92:1415-1421. 1966.-High titers of interferon (20,480 culture-protecting units per ml) are produced in freshly prepared human leukocyte cultures inoculated with a Newcastle disease virus (NDV)-cell multiplicity of 1:1. NDV replicates to low titers in these cultures. Incubation of leukocytes at 37 C for 24 hr prior to inoculation of NDV results in almost complete loss of detectable interferon production, but virus replicates to higher titers than in the freshly prepared cultures. In contrast, no diminution of interferon production in response to phytohemagglutinin (PHA) occurs on 24 hr of incubation of cultures prior to addition of PHA. Experiments with cultures of predominantly pure cell fractions of peripheral blood indicate that the lymphocyte fraction produces interferon in response to either NDV or PHA, and that polymorphonuclear leukocytes produce no interferon in response to these agents. These studies suggest a hitherto unsuspected ability of human lymphocytes to produce high titers of interferon in vivo.

Production of interferon by alveolar macrophages

Acton, Jean D. (Bowman Gray School of Medicine, Winston-Salem, N.C.), and Quentin N. Myrvik. Production of interferon by alveolar macrophages. J. Bacteriol. 91:2300-2304. 1966.-Rabbit alveolar macrophages inoculated with parainfluenza-3 virus in vitro produce a viral inhibitor which possesses the properties of interferon. The interferon is nondialyzable, is stable at pH 4, is not sedimented at 100,000 x g, exhibits species specificity, and can passively protect other alveolar macrophages from infection with virulent rabbitpox virus. The possible significance of alveolar macrophage-produced interferon is discussed.

Effect of interferon on early interferon production

Chick embryo cells given prior treatment with interferon make new interferon earlier and in larger quantities upon stimulation with Chikungunya virus than cells not so treated. By the criterion of loss of sensitivity to actinomycin, the time needed for formation of messenger RNA for interferon was decreased in the primed cells. Thus interferon affects virus action within 1 hour after infection.

Studies on the mechanism of action of Riley virus. 3. Replication of Riley's plasma enzyme-elevating virus in vitro

A study was made of the replication of Riley virus in various tissue cultures. It was observed that Riley virus replicated in primary mouse embryo cultures for 8 to 12 days. As they aged primary cultures became less susceptible to Riley virus infection, and subcultured cells were not susceptible. Suspensions of virus, in the absence of cells, were inactivated at 36.5 degrees C. Serial passage by transfer of supernatant fluids to fresh embryo cultures was not successful. Replication of the virus was more active in mouse embryo liver cultures than in the cultures of the embryo minus the livers. In cultures of mouse macrophages, the supernatants remained infective throughout the life of the cultures (21 days). The virus was passed 23 times through fresh macrophage cultures over a period of 80 days, during which the original inoculum (10(6.0)ID(50)/ml) was theoretically diluted to 10(-14). The possibility that the cells of the RES are involved in Riley virus replication is discussed.

INTERFERON-LIKE ACTIVITY OF EXTRACTS OF HUMAN SPLEEN

Extracts of human splenic tissue were found to resemble interferon in (a) their physicochemical properties, and (b) their mode of action when tested in vivo in the rabbit, using vaccinia as the challenge virus. The methods used to obtain (1) the crude extract and (2) a partially purified final fraction are described. The latter was found to be non-dialysable, stable over a pH range of 2-11, and relatively heat resistant. On analysis it appeared to be, or was associated with, a glycoprotein.