Persistent infection with mouse hepatitis virus 3 in mouse lymphoid cell lines

The sensitivity of mice to mouse hepatitis virus 3 (MHV3) varies according to strain, age, and immune status of the animals. In semisusceptible strains, mice surviving the acute phase of infection develop a chronic disease characterized by the occurrence of paralysis, virus persistence, and immunodeficiency. Persistent MHV3 infections established in vitro in YAC and RDM -4 mouse lymphoid cell lines were characterized by virus production, presence of cytoplasmic viral antigens, and cell lysis. The occurrence of cell "crisis" in YAC cells was manifested by a sharp increase in cell lysis and in the number of fluorescent cells and, concomitantly, by a marked decrease in virus titers. A relationship was observed among the percentage of fluorescent cells, cell lysis, and virus yield and was modulated by renewal of culture media, change in temperature, or inhibition of cellular RNA synthesis. Cell cloning and antibody treatment experiments indicated that viral transmission was performed by viral infection of newly permissive cells produced by the division of uninfected cells in the culture and not by transmission of viral information by infected dividing cells. The biological and biochemical properties of MHV3 variants derived from persistently infected YAC lymphoid cells were characterized. Thermosensitivity and thermolability of cloned viruses originating from persistently infected YAC cells, as well as parent virus suspensions, were studied. A similar heterogeneity was observed when YAC-derived cloned substrains (YAC-MHV3) were compared with parent-derived cloned viruses, indicating that no selection of temperature-sensitive mutants was induced in persistently infected YAC cells. However, the capacity of MHV3 to induce a lethal acute disease when injected into susceptible mice was lost very rapidly. The absence of pathogenicity was related to the induction of a subclinical infection which elicited defense mechanisms. These data suggest, therefore, that MHV3 replication in lymphoid cell lines leads to induction or selection of variants which maintain pathogenicity in vitro but display reduced pathogenic effects in vivo.     

Persistent herpes simplex virus infections established in two Burkitt lymphoma derived cell lines.

Examination of P3HR-I cells (Epstein-Barr virus [EBV] producer) persistently infected with the MAL strain of herpes simplex virus type I (HSV-I) suggested that only a few cells were actively producing a virus indistinguishable from HSV-I (MAL) despite the presence of immunofluorescent HSV-I antigens associated with the majority of cells. EBV-specific immunofluorescence was not altered in HSV-I persistently infected P3HR-I cells. HSV-I persistently infected cells, labelled for 72 h with 14C-thymidine, incorporated approx. 8% of the label into cell associated HSV-I DNA as resolved by caesium chloride gradients. Values greater than 8% of the total were suggested by hybridization of gradient fractions with 3H-HSV-I DNA. To determine whether the establishment of HSV persistent infections in Burkitt lymphoma derived cells was a general phenomenon, six strains of HSV-I (MAL, KOS, Patton, Syn R, BF and SYN V) and two strains of type 2 (333 and MS) were used to infect the P3HR-I and Raji (EBV non-producer) cell lines derived from Burkitt lymphomas. In P3HR-I cells, persistent infections were established with all strains of HSV-I but not with HSV-2. In Raji cells, persistent infections were established with all strains of HSV-I, except Syn V, and with both strains of HSV-2. No external support was required to maintain these infections.     

A reproducible method for the optimum infection of human mononuclear cells and lymphoid cell lines by herpes simplex virus type I

Parameters for the infection of human mononuclear cells (MNC) with herpes simplex virus type 1 (HSV-1) were investigated and a procedure was established which resulted in a reproducible optimum number of cells expressing virus-specific cell surface antigens The number of cells infected was independent of the sex of the donor and independent of whether the donor was HSV- seropositive or -seronegative. On the average 18±6% of HSV-infected MNC from any given donor expressed HSV-specific cell surface antigens. When the standard procedure was applied to a variety of lymphoid cell lines, a high percentage of cells of both B and non-T/non-B lines expressed HSV-specific cell surface antigens, whereas T-cell lines appeared resistant to HSV infection.     

Persistent herpes simplex virus infection and mechanisms of virus drug resistance

Herpes simplex virus (HSV) is susceptible to a variety of antiviral compounds, most of which are nucleoside analogues that interfere with DNA metabolism involving the virus enzymes DNA-polymerase and thymidine kinase. Single mutations in the virus genome give rise to resistant mutants following selection in vitro in the presence of a particular drug, and in this respect HSV is similar to several other viruses. Such mutants have been invaluable research tools. HSV is responsible for a variety of lesions which tend to be recurrent, owing to the special ability of the virus to remain latent in and reactivate from neural tissue. The consequences of this upon clinical resistance are discussed in the present review. In fact, clinical resistance in HSV infections has not yet become widespread but does appear to be especially important in immunocompromised patients, including those suffering from AIDS. HSV is proposed as an important model for the investigation of drug resistance in other, more complex organisms, and with respect to antiviral strategies against the human immunodeficiency virus.     

Persistent measles virus infection in vero and McCoy cell lines.

Persistent measles virus infection was established in two cell lines: Vero and McCoy. Vero cells were infected with a virus that had been propagated five times from an undiluted inoculum. Measles virus infection of McCoy cells caused no cytopathic lesions but led to the establishment of persistent infection. Haemadsorption (HA) and immunofluorescence (IF) results indicated that the majority of Vero and McCoy cells carried measles virus antigen localized in the cell membranes. Both cell lines released infectious virus into the medium. In Vero cells, the virus yield diminished with the number of cell passages. Our results suggest that the presence of defective interfering particles in Vero cells and an antiviral factor in the supernatant of McCoy cells contributed to the maintenance of persistent infection.     

Resistance of human blood monocytes to infection with herpes simplex virus

Human blood monocytes isolated by centrifugal elutriation were resistant to infection with herpes simplex virus type 1 (HSV). In vitro cultivation for several days resulted in a stepwise increase of virus yield. Similar amounts of virus absorbed to fresh and cultured monocytes. No viral DNA was associated with the nuclear fraction of freshly isolated monocytes early after infection indicating that early steps of virus infection were already inhibited in resistant cells. This argues against HSV induced interferon (IFN) being a major mediator of resistance. Culturing the cells for some hours was sufficient to overcome the early block. However, as revealed by virus yield assays, monocytes after 1 day of cultivation were not as susceptible as cells after 6 days of cultivation. Viral sequences could be demonstrated in the nuclei of freshly isolated monocytes after treatment with the fusion-promoting agent polyethylene glycol. Under these conditions no DNA replication occurred, indicating that overcoming the block of viral DNA entry into the nucleus was not sufficient to break resistance of the cells. Thus, the results show that several mechanisms are involved in the primary resistance of human blood monocytes to HSV.     

Comparative study of herpes simplex virus receptor expression on human lymphoid cells

Lymphocytes represent key cells of the immune system and play an important role against viral infections. However, the expression and quantification of virus receptors on lymphoid cells have, in most cases, not been studied. We report here a study of the expression of herpes simplex virus (HSV) receptors by different human lymphoid cell types. Using flow cytometry and fluorescein isothiocyanate-conjugated HSV1 (F-HSV1) we analyzed virus binding to fresh and mitogen-stimulated B and T lymphocytes and established monoclonal lymphoid cell lines (LCL). The study included analysis of (a) virus binding in relation to cell size; (b) specificity of the virus binding using virus-specific monoclonal and polyclonal antibodies as well as heparin, an inhibitor of HSV attachment to cells; and (c) HSV1 receptor density on various targets. The results show that HSV1 binds to all the cell types tested, including some cell lines which were found negative for virus replication. This binding was specifically inhibited with either purified human anti-HSV1 F(ab)'2 or heparin. Stimulation of peripheral blood leukocytes with phytohemagglutinin resulted in a remarkable increase of receptor density on T lymphocytes. B cells showed an increase in receptor density only following PBL stimulation with pokeweed mitogen. The density of HSV1 receptor on fresh T and B lymphocytes is significantly lower than that on mitogen-stimulated cells and LCL; this indicates that mitogenic activation or transformation of lymphocytes leads to an upregulation of the expression of cellular receptors for HSV1 and may in turn explain why HSV replicates only in stimulated and not in resting fresh lymphocytes.     

Susceptibility of human lymphocyte populations to infection by herpes simplex virus.

The antibody response to diphtheria toxoid by cultured tonsil cells was suppressed by herpes simplex virus during its inductive stage. Since only T lymphocytes readily supported virus replication, this immunosuppression may be attributed to a selective effect of the virus on this population of cells.     

Mouse hybrid cell lines produce antibodies to herpes simplex virus type 1.

A solid-phase radioimmunoassay procedure has been devised for the assay of antibodies produced in the mouse to herpes simplex virus type 1 (HSV-1). It is based on the adsorption of virus to flexible micro-well plates and uses radio-iodine-labelled rabbit antibody against mouse immunoglobulin to assess antibody binding. Using this assay for screening, cell hybrids have been obtained which yield monoclonal antibody to HSV-1. The hybrids are between spleen cells from hyperimmune mice and an immunoglobulin-non-secreting, azaquanine resistant myeloma cell line (NS-1). From 480 hybrid cell lines initially examined, five stable cell lines were obtained which released HSV-1-specific antibody in vitro and in vivo. Mice carrying transplants of these cell lines yield binding titres in serum of up to 1/25000. Both IgG and IgM antibodies were obtained in this way.     

Neonatal herpes simplex virus infection presenting with fever alone.

OBJECTIVE: Unlike bacterial infections, herpes simplex virus (HSV) infections are rarely considered as the diagnosis in neonates less than 1 month of age who present with fever alone. We wanted to determine the proportion of neonates with HSV who presented with fever alone and to compare that with the proportion of neonates with bacterial infection who presented with fever alone over the same period of time at our institution. STUDY DESIGN/METHODS: We retrospectively reviewed all neonatal medical records from March 1995 to February 1997 with a discharge diagnosis of HSV infection and all laboratory reports of a positive assay for HSV. We reviewed the medical records of neonates with a discharge diagnosis of bacterial infection over the same period of time. We excluded neonates who were afebrile, whose fever source was evident on physical examination, or who were immunocompromised. RESULTS: Eighteen neonates were diagnosed with an HSV infection over the 2-year period. One presented with fever alone. Twenty-seven of 113 neonates who presented with fever alone had a bacterial infection; 2 of these babies had meningitis. CONCLUSION: The proportion of neonates with HSV infection who presented with fever alone was comparable to that of neonates with bacterial meningitis who presented with fever alone at our institution. Testing and empirically treating for HSV infection might be warranted in febrile neonates with negative bacterial cultures.     

Persistent reactivable latent herpes simplex virus infection in trigeminal ganglia of mice treated with antiviral drugs

Summary Latent reactivable infection was established with HSV in mouse trigeminal ganglion. A number of antiviral drugs (IUDR, acycloguanosine, Ara-A, PAA and PFA), effective against acute CNS infection with HSV, failed to influence the latent infection once established. Neither lipophilic properties of PFA-derivatives nor the combination of Ara-A and acyloguanosine improved the drug-effects on HSV latency.With 1 Figure     

Diagnosis of herpes simplex virus infection by immunofluorescence.

The utility of the indirect immunofluorescent antibody (IFA) technique for diagnosis of herpes simplex virus (HSV) infection was examined by testing specimens for this agent from 31 patients with encephalitis or meningitis, 17 with conjunctivitis, 19 with genital disease, and 1 with genital disease and meningitis. Brain biopsy tissue from four patients with encephalitis was positive by IFA and virus culture for HSV. Leukocytes in cerebrospinal fluid from these four patients and one with HSV meningitis were also positive by IFA, but virus isolation attempts on the fluid were all negative. Conjunctival scrapings from two patients with conjunctivitis were positive for HSV by both IFA and virus culture. Eleven of 12 culture-positive lesions of herpes progenitalis were positive by IFA, and 1 dark field-positive syphilitic chancre was also positive for HSV by both IFA and culture. Evidence for specificity of the results was provided by internal controls in each test and negative results from patients with other diagnoses. Thus, the IFA technique constituted a rapid, sensitive, and specific diagnostic method for the diagnosis of HSV infections.