ABORTIVE INFECTION OF CANINE CELLS BY HERPES SIMPLEX VIRUS. I. CHARACTERIZATION OF VIRAL PROGENY FROM CO-OPERATIVE INFECTION WITH MUTANTS DIFFERING IN CAPACITY TO MULTIPLY IN CANINE CELLS

Replication of canine herpesvirus: I. Synthesis of viral deoxyribonucleic Acid

This paper reports the results of two series of experiments. The first series indicated that deoxyribonucleic acid (DNA) extracted from partially purified canine herpesvirus virions is characterized by a high guanine plus cytosine molar base ratio (65 to 67 mole%), similar to the DNA of herpes simplex virus. In the second series of experiments it was estimated, on the basis of uptake of tritiated thymidine, that in dog kidney cells canine herpesvirus-DNA synthesis starts at 4 hr and continues until 16 hr after infection. Treatment of infected cells with puromycin during the first 4 hr of infection blocks the onset of viral DNA synthesis, whereas, after this time the uptake of thymidine is unaffected.

Similarities and Differences in the Development of Laboratory Strains and Freshly Isolated Strains of Herpes Simplex Virus in HEp-2 Cells: Electron Microscopy

HEp-2 cells infected with two laboratory strains (mP and MP) and two freshly isolated strains (F and G) of herpes simplex virus were fixed at intervals between 4 and 50 hr postinfection and sectioned, and were then examined with the electron microscope. These studies revealed the following. (i) All four strains caused identical segregation of nucleoli and aggregation of host chromosomes at the nuclear membrane. (ii) The development of MP virus could not be differentiated from that of its parent mP strain. (iii) There were quantitative differences between laboratory (mP) and freshly isolated (F) type 1 strains. Thus, cells infected with F contained numerous nuclear crystals of nucleocapsids and relatively few cytoplasmic structures containing enveloped nucleocapsids. Conversely, cells infected with mP or with MP virus contained numerous cytoplasmic structures with enveloped nucleocapsids and relatively few nuclear crystals of nucleocapsids. (iv) There were qualitative differences between type 2 strain (G) isolated from genital lesions and type 1 strains. Thus, cells infected with the G strain contain numerous filaments in nuclei and unenveloped and partially enveloped nucleocapsids in the cytoplasm. Of particular interest is the finding that cytoplasmic membranes in apposition to nucleocapsids were thickened and bent as if they were enveloping the particle. The significance of the qualitative differences in the development of the four strains is discussed.

The disaggregation of host polyribosomes in productive and abortive infection with herpes simplex virus

Herpes simplex virus strain MPdk- causes disaggregation of host polyribosomes in both permissive (HEp-2) and nonpermissive (DK) cells during the first 3 hours after infection. The following findings are discussed in this paper: (1) UV light-irradiated virus does not cause disaggregation of host polyribosome. (2) To obtain equivalent disaggregation of host polyribosomes, 1 hour after infection the nonpermissive DK cells must be infected with MPdk- virus at a multiplicity twenty- to thirty-fold higher than the permissive HEp-2 cells. (3) Actinomycin D (0-20 microg/ml of medium), 6-azauridine (0-10(-4) M), or p-fluorophenylalanine (0-10(-3) M) do not prevent the disaggregation of host polyribosomes in HEp-2 cells infected with 60 plaque-forming units (PFU)/cell of MPdk- virus. However, the drugs do prevent the disaggregation of host polyribosomes in DK cells infected with 1000 PFU/cell of MPdk- virus. (4) The differences between HEp-2 and DK cells with respect to multiplicity requirements to induce disaggregation and the ability of the drugs to prevent it are due to some property of the product specified by MPdk- in these cells. This conclusion is based on the finding that in DK cells productively infected with MPdk+sp, a multistep mutant of MPdk- virus, equivalent disaggregation of host polyribosomes is achieved with 40 PFU/cell and cannot be prevented by actinomycin D. The interpretation of these findings is based on data reported previously that the products specified by MPdk- virus in nonpermissive DK cells malfunction. We conclude that (1) in permissive cells the disaggregation of host polyribosomes is catalyzed by a highly efficient protein synthesized after infection; (2) in nonpermissive cells the protein malfunctions; to obtain comparable reduction in host functions the concentration of this protein must be higher in nonpermissive cells. This condition is satisfied by infecting nonpermissive cells at high multiplicity. (3) The reduction in synthesis or in function of this protein by the various drugs is sufficient to prevent the breakdown of host polyribosomes in nonpermissive cells but not in permissive cells.

Infection of polarized MDCK cells with herpes simplex virus 1: two asymmetrically distributed cell receptors interact with different viral proteins

Herpes simplex virus 1 attaches to at least two cell surface receptors. In polarized epithelial (Madin-Darby canine kidney; MDCK) cells one receptor is located in the apical surface and attachment to the cells requires the presence of glycoprotein C in the virus. The second receptor is located in the basal surface and does not require the presence of glycoprotein C. Exposure of MDCK cells at either the apical or basal surface to wild-type virus yields plaques and viral products whereas infection by a glycoprotein C-negative mutant yields identical results only after exposure of MDCK cells to virus at the basal surface. Multiple receptors for viral entry into cells expand the host range of the virus. The observation that glycoprotein C-negative mutants are infectious in many nonpolarized cell lines suggests that cells in culture may express more than one receptor and explains why genes that specify the viral proteins that recognize redundant receptors, like glycoprotein C, are expendable.

Absence of host-cell influence on binding specificity of herpes simplex virus type 1 induced Fc receptor

Herpes simplex virus (HSV) infected cells express on their surface a receptor with affinity to the Fc portion of immunoglobulin G (IgG). The influence of the infected host cell on the specificity of the receptor was investigated with radiolabeled human IgG Fc fragment and four animal IgGs (rabbit, dog, cow, and rat) and eight human and animal (primate, rabbit, dog, cow, and rat) fibroblastoid and epithelioid cell lines. Human IgG Fc, rabbit IgG and cow IgG bound to all cell lines infected with HSV type 1 strain F (HSV-1 F), whereas dog IgG and rat IgG did not bind to any of these cells. The same binding pattern was seen when two additional HSV-1 strains infected rabbit epithelial (GMK AH1) cells. The results support the view that the specificity of the HSV Fc receptor is mainly under viral control and not primarily influenced by the species of the host cell.

Abortive infection of neural cells by herpes simplex virus type 2

The nature of the refractoriness of C6 rat glioma cells to herpes simplex virus type 2 (HSV-2) was examined. Infection of C6 cells with HSV-2 results in low virus yields, not exceeding the input virus. Although virus growth studies suggested a restricted cycle of virus replication, synthesis of HSV-2 DNA and HSV-2-specific antigens could not be detected. In addition, HSV-2 yields in C6 cells were unaffected by interferon, cycloheximide, tunicamycin, actinomycin D and cytosine arabinoside. However, trypsin, but not EDTA, treatment of infected C6 cells at 4 hours postinfection (p.i.) reduced maximal HSV-2 yields at 24 hours p.i. by 61 percent. These data: 1) indicate that HSV-2 fails to replicate in C6 cells and is prohibited from directing the synthesis of virus macromolecules; and 2) suggests that the increment of HSV-2 yields observed during the synthesis phase of the virus growth cycle represents re-envelopment and egress of a portion of the input virus.

Lymphocyte responses to herpes simplex virus isolates from patients with primary and recurrent herpes simplex genitalis

The ability of herpes simplex (HSV) isolates from patients with herpes simplex genitalis (HSG) to induce lymphocyte transformation in cells from unrelated, healthy, seropositive donors was examined in a standard lymphocyte transformation assay. All HSV isolates were obtained, before the initiation of therapy, from patients who were enrolled in a placebo-controlled trial of acyclovir in the treatment of HSG. Isolates from patients with primary infections were used, as well as those from patients with frequent (eight or more episodes per year) or infrequent (two or fewer per year) recurrent disease. Blastogenic responses to isolates from patients with infrequent HSG recurrences were significantly less than those to isolates from patients either primary infections or frequent recurrences. No differences between the latter two groups of isolates were seen. These observations demonstrate that differences among naturally occurring HSV isolates exist as determined by this in vitro assay of host-virus interactions. Differences among strains may be important in the pathogenesis of HSV infections, particularly with respect to latency.

Influence of genetic and physiological properties of the host cell on the cytopathic expression of herpes simplex virus

Two plaque morphology variants, a cell aggregating variant and a syncytial variant, were isolated from MDBK cells infected with the MP mutant of herpes simplex virus, type 1. The variants differed in the polypeptides produced in infected MDBK cells. The properties of the variants were stable on passage in cells and both variants produced only syncytia in KB and Hep-2 cells. The physiological state of MDBK cells influenced the cytopathological expression of the infecting virus, so that, under certain conditions, each variant could shift from one type of plaque morphology to the other. However, attempts to correlate this plaque morphology shift with a difference in the glycopolypeptides synthesized in the infected cells were unsuccessful.

Identification of receptors for animal viruses

Present knowledge of cell surface receptors for animal viruses is reviewed. The methods used for enumeration and identification of receptors are critically examined with respect to particular advantages and disadvantages. Specific controls and alternative interpretations are suggested in connection with the reactions of lectins which block viral attachment to cells. Currently available information for each group of animal viruses is summarized in order to define the extent to which the corresponding receptors have been identified. It is concluded that the full range of virus-receptor interactions has not yet been explored even for those viruses of which there is the most detailed knowledge. For some groups, moreover, the receptor is totally uncharacterized. Six areas in which future investigative effort might be productive are identified, including the isolation of membrane components and the immunochemical definition of viral receptors.

Genetic relatedness of type 1 and type 2 herpes simplex viruses

The extent of homology between herpes simplex virus(1) and(2) (HSV-1 and HSV-2) deoxyribonucleic acid (DNA) was measured in two ways: (i) by determination of the relative rate of hybridization of labeled HSV-1 and HSV-2 DNA to excess unlabeled HSV-1 or HSV-2 DNA immobilized on filters and (ii) by determination of the rate of hybridization of labeled HSV-1 and HSV-2 DNA to excess unlabeled HSV-1 or HSV-2 DNA in solution. Approximately 40% of HSV-1 and HSV-2 DNA is homologous at hybridization temperatures 25 C below the melting temperature (T(m)) of HSV DNA (liquid-filter annealing). Lowering the temperature to 34 C below the T(m) increased the extent of homology to 46% (liquid annealing). The extent of base-pairing in HSV-1-HSV-2 heteroduplex DNA was determined by thermal chromatography on hydroxyapatite. Heteroduplexes of HSV-1 and HSV-2 DNA eluted in a single peak whose midpoint (Te(50)) was 10 C below that of the homoduplex. Conspicuously absent were heteroduplexes that eluted at more than 15 C below the Te(50) of the homoduplex. The data indicate the existence of a variable region of DNA (54%) with very little, if any, homology and an invariable region (46%) with relatively good (85%) matching of base pairs.

Marek's disease herpes virus: a cytomegalovirus

The DNA of herpes viruses associated with Marek's disease of fowl contains 56-57 moles of guanine and cytosine per 100. The composition of its DNA and lack of infectiousness of cell-free preparations suggest that the herpes virus associated with Marek's disease belongs to the herpes virus group B which contains predominantly cytomegaloviruses.

RNA synthesis in cells infected with herpes simplex virus. II. Evidence that a class of viral mRNA is derived from a high molecular weight precursor synthesized in the nucleus

Viral RNA extracted from the cytoplasmic polyribosomes of human epidermoid carcinoma no. 2 cells infected with herpes simplex virus (mRNA) had a sedimentation coefficient between 10S and 20S while that from nuclei of infected cells varied in size from 10S to >80S. Estimates of the maximum molecular weight of viral RNA from its sedimentation coefficients suggest that at least 10 per cent of the viral genome is transcribed as a single molecule. The ratio of RNA of different sizes found in the nuclei of cells pulse labeled for 12 minutes was approximately the same as those found in cells labeled for longer intervals implying that either some classes of viral mRNA were made as small molecules or that the large viral RNA molecules were cleaved soon after synthesis. Cytoplasmic mRNA competed to a level of at least 80 per cent in viral DNA-RNA hybridization tests with >50S RNA extracted from nuclei of infected cells. This is consistent with the hypothesis that viral mRNA is produced by cleavage of a large precursor RNA molecule.

Ribonucleic acid synthesis in cells infected with herpes simplex virus. I. Patterns of ribonucleic acid synthesis in productively infected cells

HEp-2 cells were pulse-labeled at different times after infection with herpes simplex virus, and nuclear ribonucleic acid (RNA) and cytoplasmic RNA were examined. The data showed the following: (i) Analysis by acrylamide gel electrophoresis of cytoplasmic RNA of cells infected at high multiplicities [80 to 200 plaque-forming units (PFU)/cell] revealed that ribosomal RNA (rRNA) synthesis falls to less than 10% of control (uninfected cell) values by 5 hr after infection. The synthesis of 4S RNA also declined but not as rapidly, and at its lowest level it was still 20% of control values. At lower multiplicities (20 PFU), the rate of inhibition was slower than at high multiplicities. However, at all multiplicities the rates of inhibition of 18S and 28S rRNA remained identical and higher than that of 4S RNA. (ii) Analysis of nuclear RNA of cells infected at high multiplicities by sucrose density gradient centrifugation showed that the synthesis and methylation of 45S rRNA precursor continued at a reduced but significant rate (ca. 30% of control values) at times after infection when no radioactive uridine was incorporated or could be chased into 28S and 18S rRNA. This indicates that the inhibition of rRNA synthesis after herpesvirus infection is a result of two processes: a decrease in the rate of synthesis of 45S RNA and a decrease in the rate of processing of that 45S RNA that is synthesized. (iii) Hybridization of nuclear and cytoplasmic RNA of infected cells with herpesvirus DNA revealed that a significant proportion of the total viral RNA in the nucleus has a sedimentation coefficient of 50S or greater. The sedimentation coefficient of virus-specific RNA associated with cytoplasmic polyribosomes is smaller with a maximum at 16S to 20S, but there is some rapidly sedimenting RNA (> 28S) here too. (iv) Finally, there was leakage of low-molecular weight (4S) RNA from infected cells, the leakage being approximately three-fold that of uninfected cells by approximately 5 hr after infection.