Consequences of herpes simplex virus type 2 and human cell interaction at supraoptimal temperatures.

The consequences of herpes simplex virus type 2 (HSV-2) and human embryonic fibroblast cell interaction at different temperatures (37, 40, and 42 degrees C) were investigated. Incubation at 37 or 40 degrees C was permissive for HSV-2 inhibition of host DNA synthesis, induction of virus-specific DNA replication, and infectious virus production. The amount of [methyl-3H]thymidine incorporated into viral DNA and the final yield of new infectious virus were significantly reduced at 40 degrees C compared to 37 degrees C. At 42 degrees C, detectable virus-specific DNA synthesis was totally blocked. Maximum stimulation of host cell DNA synthesis at 42 degrees C was measured after a multiplicity of infection of 0.5 to 1.0 PFU/cell. By autoradiography, data indicated that HSV-2 stimulates host cell chromosomal DNA synthesis. Stimulation of thymidine kinase activity with thermostability properties in common with a virus enzyme was detected during the first 24 h of infection at 42 degrees C, after 24 h the enhanced thymidine kinase activity had properties in common with host cell isozymes. The data obtained during this investigation indicated that stimulation of host cell DNA synthesis does not require viral DNA synthesis.     

Herpes Simplex Virus Type 2 Functions Expressed During Stimulation of Human Cell DNA Synthesis

Experiments were designed to identify herpes simplex virus type 2 (HSV-2)-specific functions expressed during stimulation of human embryo fibroblast DNA synthesis. Cultures were partially arrested in DNA synthesis by pretreatment with 5-fluorouracil and maintenance in low-serum (0.2%) medium during virus infection. Results showed that continuous [methyl-(3)H]thymidine uptake into cellular DNA was ninefold greater in HSV-2-infected than in mock-infected cultures measured after 24 h of incubation at 42 degrees C. Shifting mock-infected cultures from low- to high-serum (10%) medium also caused some stimulation, but [methyl-(3)H]thymidine uptake was only twofold greater than in cells maintained with low serum. Plating efficiencies of both HSV-2-infected and mock-infected cells at 42 degrees C were essentially the same and ranged from 37 to 76% between zero time and 72 h of incubation. De novo RNA and protein syntheses were continuously required for HSV-2 stimulation of cellular DNA synthesis. HSV-2 infection markedly enhanced transport, phosphorylation, and rate of incorporation of [methyl-(3)H]thymidine into cellular DNA, starting at 3 h and reaching a maximum by 12 h; after 12 h, these processes gradually declined to low levels. In mock-infected cells these processes remained at low levels throughout the observation period. Pretreatment of cells with interferon or addition of arabinofuranosylthymine at the time of virus infection inhibited stimulation caused by HSV-2. 5-Bromodeoxyuridine density-labeled experiments revealed that HSV-2 stimulates predominantly semiconservative DNA replication and some DNA repair. Stimulation of [methyl-(3)H]thymidine into cellular DNA correlated with detection of virus-specific thymidine kinase activity. In conclusion, HSV-2 stimulation of cellular DNA synthesis appeared to involve at least four virus-specific functions: induction of thymidine transport, HSV-2 thymidine kinase activity, semiconservative replication, and repair of cellular DNA.     

Visna virus synthesized in absence of host-cell division and DNA synthesis

Visna virus is similar to the avian and the murine oncornaviruses. Oncornavirus replication is dependent upon the provirus being integrated into the host cell's DNA but integration and subsequent oncornavirus synthesis is blocked when the host cells are prevented from synthesizing cellular DNA or dividing. The synthesis of visna virus is restricted in vivo and may be dependent upon the host cell's ability to synthesize cellular DNA or divide. Treatment of sheep choroid plexus (SCP) cells with ultraviolet light or with mitomycin C prior to infection irreversibly inhibited plexus (ScP) cells with ultraviolet light or with mitomycin C prior to infection irreversibly inhibited both cell division and cellular nucleic acid synthesis but did not inhibit visna virus synthesis. Similarly, the synthesis of visna virus in cultures of SCP cells which had been prevented from dividing by being deprived of serum and in cultures of SCP cells which were incapable of synthesizing host cell nucleic acids by being treated with miracil D or sodium hexachloroiridate was equivalent to the synthesis of visna virus in cultures of SCP cells which were allowed to both synthesize cellular nucleic acids and divide. The synthesis of visna virus in the presence of ethidium bromide further demonstrated that integration of the visna provirus into the host cell's DNA is not required for visna virus synthesis to occur.     

Expression of the Viral Thymidine Kinase Gene in Herpes Simplex Virus-Transformed L Cells

In these studies, the expression of thymidine kinase (TK) in normal and herpes simplex virus (HSV)-transformed L cells has been compared. In asynchronously dividing cultures of L cells, the TK activity rose and declined rapidly and coordinately with DNA synthesis. When net cell increase stopped, TK activity was at a minimum. In contrast, TK activity of HSV-transformed cells remained at a minimum during rapid DNA synthesis and gradually increased as the rate of DNA synthesis decreased. When net cell increase stopped, TK activity was at a maximum. In synchronous cultures of L cells, TK activity rose and fell coordinately with the rate of DNA synthesis. In synchronous cultures of HSV-transformed cells, no increase in TK activity was observed during the period of rapid DNA synthesis, i.e., the S phase. These findings indicated that the viral TK gene in HSV-transformed cells was not placed under the control of the cellular mechanisms which normally modulate the host cell TK gene. Lytic infection of HSV-transformed cells with a TK(-) mutant of HSV-1 induced a four-to fivefold increase in viral TK. The TK of HSV-1 was induced in the HSV-1-transformed cells and HSV-2 in the HSV-2-transformed cells by this TK(-) mutant. The same infection of normal L cells decreased the cellular TK activity by 80%. This stimulation, rather than inhibition, suggest that the viral gene in HSV-transformed cells retain some of its original viral characteristics.     

Inhibition of DNA synthesis in varicella-zoster virus-infected cells by BV-araU.

The inhibitory effect of BV-araU on DNA synthesis in human embryonic lung cells infected with varicella-zoster virus (VZV) or herpes simplex virus type 1 (HSV-1) was compared with that of acyclovir. Cellular uptake of [3H]thymidine and its incorporation into DNA was markedly stimulated by the infection with VZV or HSV-1, suggesting that the incorporation was mainly due to viral DNA synthesis. DNA synthesis in VZV-infected cells was dose-dependently suppressed by BV-araU and acyclovir, although cellular uptake of [3H]thymidine decreased in cells treated with a high concentration of drugs for an extended time. DNA synthesis in HSV-1-infected cells was also markedly inhibited by both drugs in a dose-dependent manner, without affecting cellular uptake of [3H]thymidine. The concentration of drugs inhibiting DNA synthesis was well correlated to their in vitro anti-VZV and anti-HSV-1 activities. The inhibitory concentration of BV-araU for DNA synthesis in VZV-infected cells was one-thousandth of that of acyclovir. Our results suggest that the antiviral action of BV-araU against VZV and HSV-1 is based on the inhibition of DNA synthesis in herpesvirus-infected cells.     

Herpes Simplex Virus Type 1 Infection of Isogenic Epstein-Barr Virus Genome-Negative and -Positive Burkitt''s Lymphoma-Derived Cell Lines

The Epstein-Barr virus (EBV) genome-negative Burkitt's lymphoma-derived cell lines BJAB and Ramos and their in vitro EBV-converted sublines BJAB-B1, BJAB-A5, BJAB-B95-8, and AW-Ramos were infected with high multiplicities of herpes simplex virus type 1 (HSV-1; 10 to 70 PFU/cell). Cultures were monitored for cell growth and HSV-1 DNA synthesis. EBV-converted BJAB cultures were more permissive for HSV-1 infection than BJAB cultures. Significant cell killing and HSV-1 DNA synthesis were observed during the first 48 h of infection in the EBV-converted BJAB cultures but not in the BJAB cultures. The EBV-converted BJAB-B1 cell line contains an appreciable fraction of EBV-negative cells. Therefore, it was cloned. EBV-positive and -negative cells were identified by using EBV-determined nuclear antigen anti-complement immunofluorescence. Two types of subclones were identified: (i) those which contained both EBV-determined nuclear antigen-positive and -negative cells and (ii) those which contained only EBV-determined nuclear antigen-negative cells. When levels of HSV-1 DNA synthesis were measured in these subclones, it was found that the former were more permissive for HSV-1 infection than the latter. Thus, the presence of the EBV genome in BJAB cells correlates with increased permissiveness of these cells for HSV-1 during the first 48 h of infection. Nonetheless, persistent HSV-1 infections were established in both BJAB and EBV-converted BJAB-B1 cultures. No differences in extent of permissiveness for HSV-1 infection were found for Ramos and EBV-converted AW-Ramos cells.     

Deoxyribonucleic Acid Synthesis in Synchronized Mammalian KB Cells Infected with Herpes Simplex Virus

We examined the patterns of host cell and virus deoxyribonucleic acid (DNA) synthesis in synchronized cultures of KB cells infected at different stages of the cell cycle with herpes simplex virus (HSV). We found that the initiation of HSV DNA synthesis, we well as the production of new infectious virus, is independent of the S, G1, and G2 phases of the mitotic cycle of the host cell. This is in contrast to data previously found with equine abortion virus. Because HSV replicates independently of the cell cycle, we were able to establish conditions that would permit the study of rates of HSV DNA synthesized in logarithmically growing cells in the virtual absence of cellular DNA synthesis. This eliminates the need for separation of viral and cellular DNA by isopycnic centrifugation in CsCl. We found that HSV DNA synthesis was initiated between 2 to 3 hr after infection. The rate of DNA synthesis increased rapidly, reaching a maximum 4 hr after infection, and decreased to 50% of maximum by 8 hr. Evidence is also presented which suggests that HSV infection can inhibit both the ongoing synthesis of host DNA as well as the initiation of the S phase.     

Cytofluorometry of lymphocytes infected with Epstein-Barr virus: effect of phosphonoacetic acid on nucleic acid.

DNA synthesis in Epstein-Barr virus (EBV)-infected lymphocytes was inhibited by phosphonoacetic acid (PAA) as measured by [3H]thymidine incorporation. PAA, at a concentration of 200 microgram/ml, inhibited [3H]thymidine incorporation by human umbilical cord lymphocytes infected with EBV strain P94 but had little effect on DNA synthesis in mitogen-stimulated cells. Transformed cell lines did not develop from infected cord cell cultures treated with 100 microgram of PAA per ml. Cytofluorometric analysis showed marked increases in cellular nucleic acid content (RNA plus DNA) as early as 9 days after infection of cord cells in the absence of PAA and before significant enhancement of [3H]thymidine incorporation became apparent. Moreover, EBV led to increases in cellular nucleic acid even when 200 microgram of PAA per ml was added to cell cultures before infection. The apparent discrepancy between results obtained by [3H]thymidine incorporation and cytofluorometry is explained either by significant inhibition of cellular DNA polymerases by PAA or by a block at the G2 + M phase of the cell cycle. The data suggest that EBV initiates alterations in cellular nucleic acid synthesis or cell division without prior replication of viral DNA by virus-induced DNA polymerases.     

Kinetics of Nucleic Acid Synthesis in Human Embryonic Kidney Cultures Infected with Adenovirus 2 or 12: Inhibition of Cellular Deoxyribonucleic Acid Synthesis

Infection of human embryonic kidney (HEK) cell cultures with adenovirus types 2 or 12 resulted in an initial drop in the rate of incorporation of (3)H-thymidine into deoxyribonucleic acid (DNA) during the early latent period of virus growth, followed by a marked rise in label uptake. It was shown by cesium chloride isopycnic centrifugation that, after adenovirus 2 infection, there was a decrease in the rate of incorporation of thymidine into cellular DNA. Moreover, DNA-DNA hybridization experiments revealed that, by 28 to 32 hr after infection with either adenovirus 2 or 12, the amount of isolated pulse-labeled DNA capable of hybridizing with HEK cell DNA was reduced by approximately 60 to 70%. Autoradiographic measurements showed that the inhibition of cellular DNA synthesis was due to a decrease in the ability of an infected cell to synthesize DNA. The adenovirus-induced inhibition of host cell DNA synthesis was not due to degradation of cellular DNA. (3)H-thymidine incorporated into cellular DNA at the time of infection remained acid-precipitable, and labeled material was not incorporated into viral DNA. Furthermore, when zone sedimentation through neutral or alkaline sucrose density gradients was employed, no detectable change was observed in the sedimentation rate of this cellular DNA at various times after infection with adenovirus 2 or 12. In addition, there was no increase in deoxyribonuclease activity in cells infected with either virus. Cultures infected for 38 hr with adenovirus 2 or 12 incorporated three to four times as much (3)H-uridine into ribonucleic acid (RNA) as did non-infected cultures. Furthermore, the net RNA synthesized by infected cultures substantially exceeded that of control cultures. The activity of thymidine kinase was induced, but there was no stimulation of uridine kinase.     

Incorporation of Iododeoxyuridine into Cellular Deoxyribonucleic Acid Synthesized After Infection with Simian Virus 40

Primary monkey kidney cells (Cerocpithecus aethiops) in the stationary phase of growth were labeled with (14)C-thymidine for 24 hr prior to infection with simian virus 40 (strain 777). (3)H-deoxyadenosine and 5-iodo-2'-deoxyuridine (IUdR) were added to some of the cultures 24, 48, or 72 hr after infection; 24 hr later the deoxyribonucleic acid (DNA) was extracted from these cultures and centrifuged in a CsCl density gradient. The portion of DNA which had become heavier because of incorporation of IUdR could be seen as a second peak in the sedimentation profile. This peak contained (14)C as well as (3)H activity. The possibility that the (14)C-labeled cellular DNA might be degraded and used for the synthesis of viral DNA could be excluded. On the basis of these results, it must be assumed that the infection of monkey kidney cells with simian virus 40 induces the synthesis of cellular DNA.     

A human cytomegalovirus function inhibits replication of herpes simplex virus.

Human embryonic lung (HEL) cells infected with human cytomegalovirus (HCMV) restricted the replication of herpes simplex virus type 1 (HSV-1). A delay in HSV replication of 15 h as well as a consistent, almost 3 log inhibition of HSV replication in HCMV-infected cell cultures harvested 24 to 72 h after superinfection were observed compared with controls infected with HSV alone. Treatment of HCMV-infected HEL cells with cycloheximide (100 micrograms/ml) for 3 or 24 h, conditions known to result in accumulation of HCMV immediate-early and early mRNA, was demonstrated effective in blocking HCMV protein synthesis, as shown by immunoprecipitation with HCMV antibody-positive polyvalent serum. Cycloheximide treatment of HCMV-infected HEL cells and removal of the cycloheximide block before superinfection inhibited HSV-1 replication more efficiently than non-drug-treated superinfected controls. HCMV DNA-negative temperature-sensitive mutants restricted HSV as efficiently as wild-type HCMV suggesting that immediate-early and/or early events which occur before viral DNA synthesis are sufficient for inhibition of HSV. Inhibition of HSV-1 in HCMV-infected HEL cells was unaffected by elevated temperature (40.5 degrees C). However, prior UV irradiation of HCMV removed the block to HSV replication, demonstrating the requirement for an active HCMV genome. HSV-2 replication was similarly inhibited in HCMV-infected HEL cells. However, replication of adenovirus, another DNA virus, was not restricted in these cells under the same conditions. Superinfection of HCMV-infected HEL cells with HSV-1 labeled with [3H]thymidine provided evidence that the labeled virus could penetrate to the nucleus of cells after superinfection. Evidence for penetration of superinfecting HSV into HCMV-infected cells was also provided by blot hybridization of HSV DNA synthesized in cells infected with HSV alone versus superinfected cell cultures at 0 and 48 h after superinfection. In addition, superinfection with vesicular stomatitis virus ruled out a role for interferon in restriction of HSV replication in this system.     

下调细胞P21WAF1/CIP1基因表达可抑制单纯疱疹病毒Ⅱ型复制

为了揭示细胞P21蛋白在单纯疱疹病毒Ⅱ型（herpes simplex virus type 2, HSV-2）复制中的作用,通过用HSV-2感染和感染前用特异性小干扰RNA (small interfering RNA,siRNA) 抑制P21基因表达,应用Western 印迹方法检测宿主细胞和病毒蛋白水平,用终点滴定法测定病毒半数组织培养感染量（50% tissue culture infectious dose, TCID50）,以及观察感染细胞的细胞病变效应（cytopathic effect, CPE）等3个方面,揭示细胞P21蛋白水平的变化对病毒复制的影响.结果表明,HSV-2在细胞内复制时可引起P21蛋白水平增高;而用特异性siRNA下调细胞P21基因表达时,可显著地抑制HSV-2 gB蛋白水平,减少培养细胞上清液中病毒TCID50.提示P21蛋白对HSV-2的复制具有重要的作用.     

Nonproductive Infection and Induction of Cellular Deoxyribonucleic Acid Synthesis by Bovine Adenovirus Type 3 in a Contact-Inhibited Mouse Cell Line

Bovine adenovirus type 3 (BAV-3), which has been reported to produce tumors in newborn hamsters, induced cellular deoxyribonucleic acid (DNA) synthesis in a contact-inhibited mouse kidney cell line (C3H2K). In this system, the virus did not multiply, whereas virus-specific tumor antigen (T antigen) was detected in nearly all cells. Replication of viral DNA could not be detected by DNA-DNA hybridization on membrane filters. The cellular DNA synthesis induced by BAV-3 did occur in the absence of added serum. Extent of induction of cellular DNA synthesis was closely correlated with the multiplicity of infection. Cells activated to synthesize DNA in the serum-free medium by the virus infection progressed to cell division without noticeable cell killing.     

Simian virus 40 gene A regulation of cellular DNA synthesis. II. In nonpermissive cells.

The stimulation of host macromolecular synthesis and induction into the cell cycle of serum-deprived G0-G1-arrested mouse embryo fibroblasts were examined after infection of resting cells with wild-type simian virus 40 or with viral mutants affecting T antigen (tsA58) or small t antigen (dl884). At various times after virus infection, cell cultures were analyzed for DNA synthesis by autoradiography and flow microfluorimetry. Whereas mock-infected cultured remained quiescent and displayed either a 2N DNA content (80%) or a 4N DNA content (15%), mouse cells infected with wild-type simian virus 40, tsA58 at 33 degrees C, or dl884 were induced into active cell cycling at approximately 18 h postinfection. Although dl884-infected mouse cells were induced to cycle initially at the same rate as wild type-infected cells, they became arrested earlier after infection and also failed to reach the saturation densities of wild-type simian virus 40-infected cells. Infection with dl884 also failed to induce loss of cytoplasmic actin cables in the majority of the infected cell population. Mouse cells infected with tsA58 and maintained at 39.5 degrees C showed a transient burst of DNA synthesis as reflected by changes in cell DNA content and an increase in the number of labeled nuclei during the first 24 h postinfection; however, after the abortive stimulation of DNA synthesis at 39.5 degrees C shift experiments demonstrated that host DNA replication was regulated by a functional A gene product. It is concluded that both products of the early region of simian virus 40 DNA play a complementary role in recruiting and maintaining simian virus 40-infected cells in the cell cycle.     

Herpes simplex virus 1 infection alters the mRNA translation processing in L-02 cells

HSV-1 infection-mediated regulation of mRNA translation in host cells is a systematic and complicated process. Investigation of the details of this mechanism will facilitate understanding of biological variations in the viral replication process and host cells. In this study, a comparative proteomics technology platform was applied by two-dimension electrophoresis of HSV-1 infected normal human L-02 cell and control cell lysates. The observed protein spots were analyzed qualitatively and quantitatively by the PDQuest software package. A number of the different observed protein spots closely associated with cellular protein synthesis were identified by matrix-assisted laser-desorption ionization-time of flight-mass spectrometry (MALDI-TOF-MS). The expression levels of the RPLP1 protein, which is required for mRNA translation, and KHSRP protein, which is involved in rapid decay of mRNA, were up-regulated, whereas the expression level of RNP H2, which is involved in positive regulation on the mRNA splicing process, was down-regulated. All of these results suggest that HSV-1 infection can influence cellular protein synthesis via modulation of cellular regulatory proteins involved in RNA splicing, translation and decay, resulting in optimisation of viral protein synthesis when cellular protein synthesis is shut off. Although there is need for further investigations regarding the detailed mechanisms of cellular protein control, our studies provide new insight into the targeting of varied virus signaling pathways involved in host cellular protein synthesis.     

Herpes Simplex Virus 1 Infection Alters the mRNA Translation Processing in L-02 Cells

HSV-1 infection-mediated regulation of mRNA translation in host cells is a systematic and complicated process. Investigation of the details of this mechanism will facilitate understanding of biological variations in the viral replication process and host cells. In this study, a comparative proteomics technology platform was applied by two-dimension electrophoresis of HSV-1 infected normal human L-02 cell and control cell lysates. The observed protein spots were analyzed qualitatively and quantitatively by the PDQuest software package. A number of the different observed protein spots closely associated with cellular protein synthesis were identified by matrix-assisted laser-desorption ionization-time of flight-mass spectrometry （MALDI-TOF-MS）. The expression levels of the RPLP1 protein, which is required for mRNA translation, and KHSRP protein, which is involved in rapid decay of mRNA, were up-regulated, whereas the expression level of RNP H2, which is involved in positive regulation on the mRNA splicing process, was down-regulated. All of these results suggest that HSV-1 infection can influence cellular protein synthesis via modulation of cellular regulatory proteins involved in RNA splicing, translation and decay, resulting in optimisation of viral protein synthesis when cellular protein synthesis is shut off Although there is need for further investigations regarding the detailed mechanisms of cellular protein control, our studies provide new insight into the targeting of varied virus signaling pathways involved in host cellular protein synthesis.     

Assay for Epstein-Barr virus based on stimulation of DNA synthesis in mixed leukocytes from human umbilical cord blood.

Relationships between the rate of DNA synthesis in cultured human umbilical cord leukocytes and the multiplicity of added Epstein-Barr virus (EBV) were studied. At low multiplicities of approximately 0.1 transforming units/cell (approximately 10 physical particles/cell), inoculated cultures demonstrated increased rates of DNA synthesis, by comparison to uninoculated cultures, 3 days after inoculation. Stimulation of DNA synthesis was evident of progressively longer intervals after inoculations of 10-fold dilutions of virus. The rate of DNA synthesis, determined by short [-3H]thymidine pulses, reflected as small as twofold changes in multiplicity and thus can serve as a quantitative assay for the virus. Changes in the rate of DNA synthesis were evident before increases in cell number or alteration in morphology. Stimulation of DNA synthesis in umbilical cord leukocytes was inhibited by treatment of EBV with antibody and also in graded fashion, by progressive doses of UV irradiation to the virus. Induction of DNA synthesis by EBV was serum dependent. Estimates of the number of cells transformed were obtained by extrapolation from a standard curve relating known numbers of transformed cells to [-3H]thymidine incorporation and also by cloning cells after exposure to virus. At the low multiplicities of infection used in these experiments approximately 0.04 to 0.002 of the total cellular population was transformed. The high efficiency of cell transformation by EBV by comparison to other DNA tumor viruses is emphasized.