Long-term persistence of cytomegalovirus genome in cultured human cells of prostatic origin

Polyploid Giant Cancer Cells Generated from Human Cytomegalovirus-Infected Prostate Epithelial Cells

BACKGROUND

Prostate cancer is the most commonly diagnosed malignancy and the sixth leading cause of cancer death in men worldwide. Chromosomal instability (CIN) and polyploid giant cancer cells (PGCCs) have been considered predominant hallmarks of cancer. Recent clinical studies have proven the association of CIN, aneuploidy, and PGCCs with poor prognosis of prostate cancer (PCa). Evidence of HCMV transforming potential might indicate that HCMV may be involved in PCa.

METHODS

Herein, we underline the role of the high-risk HCMV-DB and -BL clinical strains in transforming prostate epithelial cells and assess the molecular and cellular oncogenic processes associated with PCa.

RESULTS

Oncogenesis parallels a sustained growth of "CMV-Transformed Prostate epithelial cells" or CTP cells that highly express Myc and EZH2, forming soft agar colonies and displaying stemness as well as mesenchymal features, hence promoting EMT as well as PGCCs and a spheroid appearance.

CONCLUSIONS

HCMV-induced Myc and EZH2 upregulation coupled with stemness and EMT traits in IE1-expressing CTP might highlight the potential role of HCMV in PCa development and encourage the use of anti-EZH2 and anti-HCMV in PCa treatment.

Does the prostate retain an endogenous antiviral defense system suggesting a past viral etiology for cancer?

Evidence of viral infection of the prostate is presented, and consists of viral isolation as well as antigen and genomic detection of integrated or episomal forms. Prior infection from "ancient" exogenous retroviruses is suggested by residual endogenous forms. The presence of an antiviral defense system based upon interferon induction has been suggested for the testes. I suggest that a similar system is also present in the prostate. Prostate cell lines (or tissue) can be tested directly for expression of interferon-γ (IFN-γ). However, enhanced expression should be induced by IFN inducers such as bispecific oligonucleotides having double stranded regions or poly I:C. RNA can be extracted and RT-PCR performed using commercially available primers for gamma interferon. Evidence for the presence of an interferon based anti-viral system would be indicated not only by interferon expression, but also its enhanced expression following exposure to the inducers. Gamma interferon is primarily associated with lymphocytic expression and immune regulation. Demonstration of its controlled expression in non-immune cells would support the hypotheses suggested here.

High prevalence of human cytomegalovirus in prostatic intraepithelial neoplasia and prostatic carcinoma

PURPOSE

Recent epidemiological data indicate that a history of increased exposure to sexually transmitted diseases is associated with an increased risk of prostate cancer. Human cytomegalovirus (HCMV) is a member of the herpesvirus family, is sexually transmitted in adults and can persistently infect prostatic epithelium in non-immunocompromised hosts. Based on increased awareness of the oncogenic potential of this virus, we decided to reexplore the issue of whether HCMV might be involved in prostate cancer pathogenesis.

MATERIALS AND METHODS

Paraffin embedded biopsy specimens from 22 randomly selected patients with prostatic intraepithelial neoplasia (PIN) lesions and prostatic carcinoma were analyzed by immunohistochemistry, in situ hybridization, polymerase chain reaction and DNA sequencing to detect HCMV nucleic acids and determine whether HCMV gene products were specifically associated with neoplastic cells.

RESULTS

We detected HCMV proteins and/or nucleic acids in all 22 of the 22 preneoplastic and neoplastic prostate lesions evaluated. HCMV proteins were specifically and often highly expressed in basal cell hyperplasia and PIN lesions, and to a lesser degree in carcinoma cells.

RESULTS

To our knowledge these data demonstrate for the first time the specific localization of HCMV nucleic acids and proteins in a high percent of PIN and prostate carcinoma lesions, and raise the possibility that HCMV might contribute to the natural history of prostatic cancer.

Viruses in the mammalian male genital tract and their effects on the reproductive system

This review describes the various viruses identified in the semen and reproductive tracts of mammals (including humans), their distribution in tissues and fluids, their possible cell targets, and the functional consequences of their infectivity on the reproductive and endocrine systems. The consequences of these viral infections on the reproductive tract and semen can be extremely serious in terms of organ integrity, development of pathological and cancerous processes, and transmission of diseases. Furthermore, of essential importance is the fact that viral infection of the testicular cells may result not only in changes in testicular function, a serious risk for the fertility and general health of the individual (such as a fall in testosteronemia leading to cachexia), but also in the possible transmission of virus-induced mutations to subsequent generations. In addition to providing an exhaustive account of the data available in these domains, this review focuses attention on the fact that the interface between endocrinology and virology has so far been poorly explored, particularly when major health, social and economical problems are posed. Our conclusions highlight the research strategies that need to be developed. Progress in all these domains is essential for the development of new treatment strategies to eradicate viruses and to correct the virus-induced dysfunction of the endocrine system.

Human cytomegalovirus and human herpesvirus 6 genes that transform and transactivate

This review is an update on the transforming genes of human cytomegalovirus (HCMV) and human herpesvirus 6 (HHV-6). Both viruses have been implicated in the etiology of several human cancers. In particular, HCMV has been associated with cervical carcinoma and adenocarcinomas of the prostate and colon. In vitro transformation studies have established three HCMV morphologic transforming regions (mtr), i.e., mtrI, mtrII, and mtrIII. Of these, only mtrII (UL111A) is retained and expressed in both transformed and tumor-derived cells. The transforming and tumorigenic activities of the mtrII oncogene were localized to an open reading frame (ORF) encoding a 79-amino-acid (aa) protein. Furthermore, mtrII protein bound to the tumor suppressor protein p53 and inhibited its ability to transactivate a p53-responsive promoter. In additional studies, the HCMV immediate-early protein IE86 (IE2; UL122) was found to interact with cell cycle-regulatory proteins such as p53 and Rb. However, IE86 exhibited transforming activity in vitro only in cooperation with adenovirus E1A. HHV-6 is a T-cell-tropic virus associated with AIDS-related and other lymphoid malignancies. In vitro studies identified three transforming fragments, i.e., SalI-L, ZVB70, and ZVH14. Of these, only SalI-L (DR7) was retained in transformed and tumor-derived cells. The transforming and tumorigenic activities of SalI-L have been localized to a 357-aa ORF-1 protein. The ORF-1 protein was expressed in transformed cells and, like HCMV mtrII, bound to p53 and inhibited its ability to transactivate a p53-responsive promoter. HHV-6 has also been proposed to be a cofactor in AIDS because both HHV-6 and human immunodeficiency virus type 1 (HIV-1) have been demonstrated to coinfect human CD4(+) T cells, causing accelerated cytopathic effects. Interestingly, like the transforming proteins of DNA tumor viruses such as simian virus 40 and adenovirus, ORF-1 was also a transactivator and specifically up-regulated the HIV-1 long terminal repeat when cotransfected into CD4(+) T cells. Finally, based on the interactions of HCMV and HHV-6 transforming proteins with tumor suppressor proteins, a scheme is proposed for their role in oncogenesis.

Anti-epithelial (anti-A549) antibodies: their nature, specificity and relevance to transplantation

Several studies have addressed the possible importance of anti-epithelial cell antibodies in kidney transplantation using the A549 cell line as an in vitro model. In this paper we report our results using for the first time an enzyme-linked immunosorbent assay (ELISA) to detect the anti-A549 cell antibodies. Sera from 129 kidney transplant patients were tested for IgM anti-epithelial cell antibodies directed against the A549 cell line prior to transplantation; only three sera were positive (2.3%). 101 of these patients were then followed-up post-transplantation; sera were collected routinely at 2, 6 and 12 weeks and at the time of rejection episodes. All samples were also tested for cytomegalovirus (CMV) IgM antibodies. Sixteen patients developed anti-A549 IgM antibodies, and there was no correlation with acute graft rejection. Anti-epithelial antibodies showed no binding to sections of normal kidney or biopsies of rejected kidneys. Eleven patients were positive for anti-CMV IgM antibodies. In nine cases both IgM anti-A549 and IgM anti-CMV antibodies were found, which was a highly significant association (p < 0.001). Analysis of A549 cellular proteins by immunoblotting gave evidence for the presence of CMV polypeptides in the cell lysate. Electron-microscopic examination of A549 cell preparations revealed intracellular particles which were compatible in size with CMV. Polymerase chain reaction analysis confirmed the presence of a specific CMV DNA sequence in A549 cells of several batches from different sources. Our data strongly suggest that the A549 cell line used in several published reports is infected with CMV and that in the majority of cases the anti-A549 'anti-epithelial' antibodies found in renal transplant patients are anti-CMV antibodies.

A 79 amino acid oncogene is responsible for human cytomegalovirus mtrII induced malignant transformation

Human cytomegalovirus (HCMV) morphological transforming region (mtr)II is the only HCMV mtr that was retained and expressed in transformed mouse or rat cells. The minimal transforming region has previously been shown to be within a 980-bp BanII/XhoI subfragment which encodes three open reading frames (ORF) of 34, 79, and 83 amino acids. This report provides definitive evidence that the 79-aa ORF is responsible for mtrII mediated tumorigenic transformation. The 79-aa ORF, subcloned into a mammalian expression vector, pCHC79orf, induced morphologic transformation of NIH 3T3 cells. These transformed cells expressed 79-aa ORF specific transcripts and were tumorigenic when injected into nude mice. A construct containing a triple termination linker inserted after codon 24 failed to transform NIH 3T3 cells to tumorigenicity even though 79-aa ORF specific transcripts were expressed. Furthermore, when the triple termination linker was inserted after codon 49, tumorigenic transformation still occurred. These results demonstrate that the 79-aa ORF is the oncogene within HCMV mtrII and that the first 49-aa are sufficient.

Sodium butyrate-inducible replication of human cytomegalovirus in a human epithelial cell line

Replication of human cytomegalovirus (HCMV) in a human epithelial thyroid papillary carcinoma cell line (TPC-1) was restricted. However, pretreatment of these cells with 5 mM sodium butyrate (NaB) for 24 hr before infection enhanced both HCMV yield and infectious center titer to a similar level of that seen in human embryonic lung fibroblast cells. Immunofluorescence staining, gel electrophoresis, and Northern blot analysis revealed that TPC-1 cells are nonpermissive for expression of HCMV major immediate early (IE1) functions, but many of the cells become permissive after being treated with NaB. The presence of cycloheximide during NaB pretreatment of the cells efficiently diminished the stimulatory effect of NaB on expression of the IE1 gene. Therefore, it appeared that NaB induces the synthesis of a cellular protein(s) which apparently plays an important role in the conversion of nonpermissive cells to a permissive state for expression of this critical viral gene. Transient chloramphenicol acetyltransferase (CAT) assay experiments indicated that in TPC-1 cells the HCMV-CAT construct which contains the complete IE1 promoter regulatory region was expressed poorly, whereas a high level of CAT activity was detectable in the NaB-treated cells. Therefore, these results suggest that the enhancing effect of NaB on HCMV replication is expressed through some host cellular factor(s), and the HCMV IE1 promoter regulatory region is most likely to be the primary target of NaB action.

Acquisition of cytomegalovirus infection: an update

Human cytomegalovirus (CMV) is a ubiquitous deoxyribonucleic acid virus that commonly infects a majority of individuals at some time during their life. Although most of these CMV infections are asymptomatic, certain patient groups are at risk to develop serious illness. Understanding the epidemiology of this virus is a key element in the development of strategies for preventing CMV disease. However, a number of features of this virus complicate such understanding. Following infection, CMV can remain latent, with subsequent reactivation; the factors controlling latency and reactivation and those factors which determine whether a CMV infection will be symptomatic are unknown. CMV disease can be acquired by natural routes, including horizontal and vertical transmission. Due to the ubiquity of CMV, the delineation of CMV transmission by these natural routes is complicated by the myriad of possible sources. Moreover, concerns over the risk of CMV transmission to the seronegative pregnant female have been raised in relation to preventing CMV transmission. By using molecular biologic techniques, much knowledge has been gained regarding the transmission of CMV disease by natural routes; however, a number of questions remain unanswered. The transmission of CMV infection by natural routes is therefore reviewed and the issues are highlighted. Primary infection, reactivation, and reinfection are the types of active CMV infections that can occur in an immunocompromised patient. In addition to natural routes of infection, introduction of presumably latently infected organs and requirements for multiple blood transfusions increase potential exposure to CMV in the immunocompromised patient. Understanding the epidemiology of CMV infections in the immunocompromised patient is difficult and in some instances controversial due to the complexity and interdependency of a number of factors which lead to CMV infection. In an immunocompromised individual, a major risk factor in developing overt CMV-related disease is associated with the serological status of an organ donor, the recipient, and the blood product given to these patients. In addition, a large body of inferential data supports the transmission of CMV by blood products or organs from seropositive donors; however, the mechanisms by which transmission occurs remain unclear. The possible sources and mechanisms of transmission of CMV infections in the immunocompromised host are reviewed. Lastly, strategies for the ultimate prevention of CMV disease are discussed in light of the epidemiology of CMV infections. To date, these strategies have included use of CMV-seronegative blood products or organs, antiviral agents, and vaccines.(ABSTRACT TRUNCATED AT 400 WORDS)

The status of CMV as a human pathogen

Cytomegalovirus (CMV) is a common infectious agent which is well adapted to its host. Following primary infection, which is almost always asymptomatic in people with normal immunity, the virus establishes latency at sites which are unknown. The virus is probably maintained in this latent state by immune surveillance mechanisms since immunosuppression frequently leads to reactivation of virus.

Cytomegalovirus has been identified in most anatomical areas of the human body. The aim of this article is to define criteria for pathogenicity so that clinical and experimental data can be reviewed to determine if CMV is likely to cause disease at these various clinical sites. Thus, patients have been shown to die frequentlywithCMV but do they diefromit?

Establishment and biological characterization of an in vitro human cytomegalovirus latency model

In an attempt to develop an in vitro human cytomegalovirus (HCMV) latency model system, the growth characteristics of HCMV in a human thyroid papillary carcinoma cell line (TPC-1) were examined. When TPC-1 cultures preheated at 40.5 degrees for 48 hr were infected with HCMV and incubated at a supraoptimal temperature (40.5 degrees), the cultures could be maintained for at least 65 days without detection of infectious virus. In contrast, when the infected cultures were incubated at 37 degrees, HCMV persistently infected cultures were established. HCMV was reactivated from the latently infected cultures by decreasing the incubation temperature from 40.5 to 37 degrees, and the cultures subsequently entered into virus persistent infection. Although HCMV-specific polypeptides which comigrate with the immediate early virus polypeptides and nuclear antigens were continuously detectable in the majority (more than 95%) of the cells during the latent period, a detectable level of virus-specified DNA polymerase (one of the early virus proteins) was not induced, suggesting that the blockage of HCMV replication in the latently infected cultures occurs at the early stages of the HCMV replication cycle. Infectious center assay revealed that 0.002 to 0.2% of the cells contain an HCMV genome that can be activated during the latent period. The latently infected cells were susceptible to superinfection with homologous and heterologous strains of HCMV. In persistently infected cultures approximately 38% of the cells were lysed by reaction with HCMV immune serum and complement, whereas complement-mediated immune cytolysis could not be detected in the latently infected cultures. The data presented suggest that a temperature-sensitive cellular function(s) that controls the expression of the HCMV early functions plays an important role in maintenance of the HCMV genome in the latent state and reactivation of HCMV by decreasing the incubation temperature.

Microbial oncogenesis

For more than a century, medical investigators have sought to incriminate microorganisms in the cause of cancer. The first scientific evidence of such a relationship came in 1911, with the first successful induction of a tumor using a cell-free extract. Since that time, considerable data have accrued linking retroviruses, herpes viruses, the hepatitis B virus, papovaviruses, and adenoviruses to various malignant neoplasms. There is also increasing evidence that certain bacteria and parasites participate as cofactors in the development of some cancers. Although proof of cause-and-effect relationships has been difficult to obtain, there can be little doubt that microorganisms occasionally play pivotal roles in the origin of some cancers. Whether attempted intervention against these cancers is best directed against the oncogenic microorganisms themselves or against other environmental cofactors is not yet clear. Nevertheless, the successful application of tumor vaccines in the prevention of Marek's disease in chickens and in modifying the outcome of oncogenic herpesvirus infections in nonhuman primates offers hope of at least limited application of microbial vaccines in the prevention of human cancer.

Latent infection of human ovarian teratocarcinoma cells with human cytomegalovirus. Brief report

Persistent infection with human cytomegalovirus (HCMV) can be established in cultures of human ovarian teratocarcinoma (PA1) cells, and maintained for more than 200 days. Infected cultures maintained at 34 degrees C (PA1CMV34) and 37 degrees C (PA1CMV37) entered crisis and subsequently displayed massive cytopathic effects (CPE), whereas infected cultures maintained at 32 degrees C (PA1CMV32) and 39 degrees C (PA1CMV39) continued to release small amounts of infectious virus until 240 or 151 days post-infection (p.i.) respectively. PA1CMV32 cultures shifted to 37 degrees C at 258 days p.i. resumed synthesis of infectious virus which resulted in cell destruction, indicating that latent infection with HCMV was maintained in PA1 cells at 32 degrees C. In contrast, PA1CMV39 cells did not produce infectious virus even when cultured at 37 degrees C for more than 100 days after the temperature shift.

Replication of cytomegalovirus in human arterial smooth muscle cells

Cytomegalovirus (CMV) strain AD-169 replicated in smooth muscle cell (SMC) cultures derived from human umbilical arteries, producing enveloped infectious virions. However, unlike the effects of CMV on fully permissive human lung fibroblasts, the effects of strain AD-169 on SMC cultures were delayed and prolonged, resulting in extended survival of a fraction of the starting population. This period of survival did not exceed the life-span of the control SMC cultures. Infectious CMV continued to be isolated from the surviving SMC cultures after extinction of the original inoculum by dilution and after treatment of the cultures with CMV neutralizing antibody. The implications of these findings for the pathogenesis of atherosclerosis are discussed.

Early interactions between human cytomegalovirus and cells

Adsorption of cytomegalovirus (CMV) to human fibroblasts was not inhibited by preincubation with other herpes viruses (HSV-1, HSV-2, VZV). Transport of virus to the nucleus was studied using virus labelled with 3H-thymidine. Radioactivity was found in the nucleus 20 minutes after virus had been added to the cells. In order to assess the expression of the virus genome, synthesis of early (EA) and late (LA) antigens was studied. Assayed on permissive human lung fibroblasts, a plaque purified virus contained more EA inducing than both EA and LA inducing viral units. Since this was a consistent finding with virions of all densities, it seems to be an effect of viral dose rather than of virion density. Alternatively, LA-defectiveness is a virion property which does not vary with virion density.

Characterization of guinea pig cytomegalovirus DNA

The genome of guinea pig cytomegalovirus (GPCMV) was analyzed and compared with that of human cytomegalovirus (HCMV). GPCMV and HCMV DNAs were isolated from virions and further purified by CsCl centrifugation. Purified GPCMV DNA sedimented as a single peak in a neutral sucrose gradient and was infectious when transfected into guinea pig embryo fibroblast cells. The cytopathology was characteristic of that seen after infection with GPCMV. Virus DNA purified from virions isolated from infected GPEF or 104C1 cells had a CsCl buoyant density of 1.713 g/cm3, which corresponds to a guanine plus cytosine content of 54.1%. The CsCl buoyant density of GPCMV DNA was slightly less than that of HCMV DNA (1.716 g/cm3), but sufficiently different so that the two virus DNA peaks did not coincide. GPCMV DNA cosedimented with T4 DNA in a neutral sucrose gradient. Restriction endonuclease cleavage of GPCMV or HCMV DNAs with HindIII, XbaI, or EcoRI yielded fragments easily separable by agarose gel electrophoresis and ranging from 1.0 X 10(6) to 25.8 X 10(6) daltons. The number, size, and molarity of GPCMV DNA fragments generated by restriction enzymes were determined. Hybridization of restriction endonuclease-cleaved GPCMV DNA with radioactively labeled HCMV DNA and, conversely, hybridization of restriction endonuclease-cleaved HCMV DNA with radioactively labeled GPCMV DNA indicated sequence homology between the two virus DNAs.

Maintenance of human cytomegalovirus genome in human diploid fibroblast cells

Human embryo lung cells pretreated with a combination of human leukocyte interferon and acyclovir were infected with human cytomegalovirus (HCMV) and treated daily for 14 days with the same inhibitor combination. After removal of the inhibitors, the incubation temperature was maintained at either 37 or 40.5 degrees. Incubation of infected cells at 37 degrees after inhibitor removal resulted in progressive virus-specific cytopathology and eventually total destruction of the cell culture. However, HCMV-infected cells incubated at 40.5 degrees after inhibitor removal exhibited little or no virus-induced cytopathology and HCMV remained noninfectious for 8 days. After extended incubation at 40.5 degrees, infectious HCMV was readily detectable even though virus-specific cytopathology was not evident. Reducing the incubation temperature from 40.5 to 37 degrees resulted in stimulation of infectious virus replication and subsequent destruction of the infected cell culture monolayer within 10 days.

Post-transcriptional control of human cytomegalovirus gene expression

During the immediate-early, early, and late phases of human cytomegalovirus infection in human fibroblasts, transcripts accumulated, respectively, from approximately 20, 75, and 90% of the sequences on the genome. Not all of the sequences which accumulated during the immediate-early and early phases were represented on polysomes, however. Four transcripts synthesized in cycloheximide-treated cells were studied in detail. A 2.2-kb transcript (0.713-0.733 map units) represented 95% of the polysome-associated RNA in cycloheximide-treated cells and was the first to be detected on polysomes at 2 hr postinfection in untreated cells. A second, less abundant, transcript of 5.2 kb (0.670-0.733 map units) was also found on polysomes in cycloheximide-treated cells, and preliminary evidence suggested that this transcript may be spliced during processing. A 3.25-kb transcript (0.190-0.217 map units) was identified also as a minor polysome-associated species of RNA. One transcript of 4.8 kb (0.630-0.670) remained associated with the nucleus and was not processed into mRNA in cycloheximide-treated cells. Differential stability between the various transcripts was observed, the 2.2-kb transcript being the most stable. The results showed that in human cytomegalovirus-infected cells controls exist at the level of transcript accumulation, transport into the cytoplasm, preferential association with polysomes, and relative stability of RNAs.

Mitogenic activity in human embryonic fibroblasts early after infection by human cytomegalovirus

We have characterized the nonspecific lymphocyte stimulation by extracts of human cytomegalovirus-infected human embryonic fibroblasts. Cell extracts prepared at 5 h postinfection (early extract) and 72 h postinfection (late extract) were both highly mitogenic in lymphocyte preparations from adult blood, cord blood, and rabbit blood. Maximum stimulation of the lymphocytes was observed on day 3 after the addition of early or late extract under optimal conditions. Early extract stimulated both the E-rosetting and the EAC-rosetting subpopulations of human lymphocytes. The mitogenic activity appeared before 5 h postinfection and was fairly stable at 30 degrees C for 5 h.

Temporal patterns of human cytomegalovirus transcription: mapping the viral RNAs synthesized at immediate early, early, and late times after infection

The transcription of the human cytomegalovirus genome was investigated at immediate early, early, and late times after infection. Viral RNAs associated with either the whole cell, the nucleus, the cytoplasm, or the polyribosomes were analyzed. At immediate early times, i.e., in the absence of de novo viral protein synthesis, the viral RNA in high abundance originated from a region of the long unique section of the prototype arrangement of the viral genome (0.660 to 0.770 map units). The viral RNA in low abundance originated from the long repeat sequences (0.010 to 0.035 and 0.795 to 0.825 map units) and a region in the long unique section (0.201 to 0.260 map units). Viral RNAs associated with the polyribosomes as polyadenylated RNA were mapped to these restricted regions of the viral genome and characterized according to size class in kilobases. At 24 h after infection in the presence of an inhibitor of viral DNA replication, i.e., at early times, the stable viral RNAs in highest abundance mapped in the long repeat sequences. Viral RNAs at intermediate abundance under these conditions mapped in two regions of the long unique section of the viral genome (0.325 to 0.460 and 0.685 to 0.770 map units). Stable viral RNAs that were associated with the polyribosomes in high abundance as polyadenylated RNA orginated from the long repeat sequences, but not from the long unique section of the viral genome. An analysis of whole-cell RNA at late times (72 h) indicated that the abundant transcription was in the regions of the long unique sequences (0.325 to 0.460 and 0.660 to 0.685 map units), and transcription of intermediate abundance was from the long repeat sequences. However, stable viral mRNA's derived from the long repeat sequences were associated with the polyribosomes at late times after infection. In addition, mRNA's originating from the long and short unique sequences were found associated with the polyribosomes at higher relative concentration than at early times after infection. It is proposed that expression of the immediate early viral genes is required to transcribe the early viral genes in the long repeat and adjacent sequences. These sequences are also transcribed at late times after infection while viral DNA synthesis continues. The expression of viral genes in most of the long and short unique sequences appears to require viral DNA replication.

Characterization of human cells persistently infected with cytomegalovirus and exposed to a chemical carcinogen

A non-productive, persistent human cytomegalovirus (CMV) infection was developed in human embryo lung (LU) cells by initially using supraoptimal temperatures to restrict the replication of a recent CMB isolate (76-24). Although CMV replication was observed in some cells within a few weeks of shifting the cultures to 37 degrees C and subculturing, CMV cytopathic effects and infectious CMV were not detected with further subculturing during the next 5 weeks. CMV-specific nuclear antigens were, however, observed in most cells (designated LU-76-24) for 38 additional culture passages made during the following 12 months. Although the LU-76-24 cells were morphologically distinct from LU cell cultures carried in parallel as controls, the LU-76-24 were contact-inhibited in spite of a somewhat disoriented growth pattern. Treatment of LU-76-24 cells with 0.05 microgram/ml of the chemical carcinogen 4-nitroquinoline 1 oxide (NQO) induced a lytic CMV infection from which a clone of cells (designated LUC-NQO) was isolated. No effect was seen when LU cells were treated with the same dose of NQO. LUC-NQO cells were morphologically altered from LU-76-24 cells and had lost contact inhibition. Even though CMV-specific nuclear antigens were observed in LUC-NQO cells, infectious CMV was not detected in lysates of these cells, nor was CMV rescued by co-cultivation of these cells with susceptible cells or by induction with 5-iodo-2'-deoxyuridine. LUC-NQO, but not LU or LU-76-24 cells, plated with good efficiency in semi-solid medium. The results indicate that long-term, non-productive, persistent CMV infections can be established in vitro and suggest that such cells may be more susceptible than non-infected cells to the action of chemical carcinogens.

Temporal regulation of human cytomegalovirus transcription at immediate early and early times after infection

The immediate early transcripts of human cytomegalovirus originated from restricted regions of the viral genome. In contrast, transcription at early times was complementary to all regions of the viral genome that were fractionated by restriction endonuclease treatment followed by agarose gel electrophoresis. The viral genome was also extensively transcribed when 2 h of protein synthesis or longer was permitted after infection in permissive cells treated with an inhibitor of viral DNA replication or in nonpermissive cells of animal origin that permit little or no viral DNA replication. The size and in vitro translation products of the cytomegalovirus-specified mRNA's at immediate early and early times after infection were determined. Discrete size classes of virus-specified polyadenylated RNA accumulated on the polyribosomes of cells infected in the presence of an inhibitor of protein synthesis. When 2 or 24 h of protein synthesis occurred after infection, there were changes in the relative abundance of the virus-specified RNAs that accumulated on polyribosomes. Treatment of nonpermissive cells had little effect on the size classes of viral RNA found associated with the polyribosomes at early times after infection. These viral mRNA's were assumed to represent early viral gene expression. In vitro translation of the viral mRNA isolated from polyribosomes at immediate early and early times after infection identified many of the virus-specified gene products and demonstrated (i) a switch from immediate early to early viral gene expression and (ii) a prolonged phase of early viral gene expression. The data also indicated that the initiation of viral RNA synthesis does not depend on the formation of viral protein, but that de novo viral protein synthesis may influence the extent of transcription of the viral genome.

Enhanced capacity of DNA repair in human cytomegalovirus-infected cells

Plaque formation in Vero cells by UV-irradiated herpes simplex virus was enhanced by infection with human cytomegalovirus (HCMV), UV irradiation, or treatment with methylmethanesulfonate. Preinfection of Vero cells with HCMV enhanced reactivation of UV-irradiated herpes simplex virus more significantly than did treatment with UV or methylmethanesulfonate alone. A similar enhancement by HCMV was observed in human embryonic fibroblasts, but not in xeroderma pigmentosum (XP12BE) cells. It was also found that HCMV infection enhanced hydroxyurea-resistant DNA synthesis induced by UV light or methylmethanesulfonate. Alkaline sucrose gradient sedimentation analysis revealed an enhanced rate of synthesis of all size classes of DNA in UV-irradiated HCMV-infected Vero cells. However, HCMV infection did not induce repairable lesions in cellular DNA and did not significantly inhibit host cell DNA synthesis, unlike UV or methylmethanesulfonate. These results indicate that HCMV enhanced DNA repair capacity in the host cells without producing detectable lesions in cellular DNA and without inhibiting DNA synthesis. This repair appeared to be error proof for UV-damaged herpes simplex virus DNA when tested with herpes simplex virus thymidine kinase-negative mutants.

Patterns of transcription of human cytomegalovirus in permissively infected cells

The rate of accumulation of cytomegalovirus transcripts in permissively infected human embryonic lung (HEL) cells was analyzed at various times after infection by hybridization of infected cell RNA to undigested or restriction endonuclease-digested cytomegalovirus DNA fixed to nitrocellulose filters. Differences in patterns of transcript accumulation were determined by measuring the abundance levels of RNA which hybridized to different HindIII-, XbaI-, or EcoRI-generated fragments of cytomegalovirus DNA. The results showed that a small but significant amount of cytomegalovirus RNA was detectable within the first 3 h after infection and that the rate of accumulation of these transcripts was static during the first 24 h, but increased thereafter. In general, the viral transcripts accumulating in infected cells could be divided into three classes. Immediate-early RNA (synthesized in the absence of protein synthesis in infected cells) hybridizes predominantly to a very restricted part of the genome and can be identified during the first 2 to 4 h postinfection. Early RNA (synthesized up to about 24 h after infection) originates from most regions of the genome but is characterized by the presence of transcripts which hybridize in great abundance to certain fragments. Late RNA (synthesized after 24 h, i.e., after the onset of viral DNA synthesis) hybridizes in approximately equal abundance to most regions of the viral genome. These results showed that a block in the transition from immediate-early to early RNA did not account for the extended period of time that elapses between the time of infection and the initiation of viral DNA synthesis. Interestingly, despite rapid adsorption and penetration and a static level of accumulation of transcripts in the cultures during the first 24 h, the number of cells that synthesized detectable amounts of viral antigens increased steadily during this time.

Herpesviruses and prostate carcinogenesis

Prostatic cancer cell cultures possessed intracellular immunofluorescent antigens specific for human cytomegalovirus (CMV) but produced no infectious virus particles. Norman human prostatic tissue yielded a CMV isolate that transformed primary human embryo lung cells in vitro. These cell transformants were highly oncogenic when transplanted to athymic nude mice. Immunological studies revealed that sera from prostatic cancer patients reacted significantly more frequently with CMV-related antigens than sera from age-, race-, and socioeconomic status-matched benign prostate hyperplasia groups. Specific reactivity against CMV-transformed cells of lymphocytes from prostatic cancer patients was also detected. These complex findings indicate that CMV may be involved in the development of prostatic neoplasia.

Virology studies and cell lines for prostate cancer

Immunological and biochemical probes for viral genomes and products, growth in cell culture, co-culture methods to activate latent genomes, use of activating agents, and electron microscopy have been used in efforts to demonstrate RNA viruses in prostate cancer. Despite findings of C-type particles and p30 antigens, the role of RNA viruses appears to be secondary, with activation of the virogene being a relatively uncommon occurrence. No compelling evidence for Herpes II or cytomegalovirus as etiologic agents has emerged, despite their common presence in the urogenital tract. Though the search for integration of fragments of viral genome into host DNA is still in progress, it appears unlikely that these viruses would account for a significant number of prostate carcinomas. Progress has been achieved in developing simple, reliable, primary culture methods for human prostatic tissue, using explants or dispersed cells. Three cell lines, all from metastatic foci, have been established, are characterized, and are available for distribution. One neonatal cell strain retains many properties of normal prostate.

Persistence of the cytomegalovirus genome in human cells

A small percentage of human fibroblast cells survived high-multiplicity infection by cytomegalovirus and were isolated as persistently infected cultures. Approximately 30% of the cells were in the productive phase of infection, since virus-specific structural antigens and virions were associated with these cells. The remaining cells contained neither viral structural antigens nor particles. Nuclear DNA from these nonproductive cells contained approximately 120 genome equivalents of viral DNA per cell as determined by reassociation kinetics. In situ hybridization confirmed that nuclei from nonproductive cells contained a significant amount of viral DNA that was distributed in most of these cells. Early virus-induced proteins and antigens were also detected. Nonproductive cells continued to grow, and there was a slow, spontaneous transition of some of these cells to productive viral replication. The majority of the viral DNA in nonproductive cells persisted with restricted gene expression. When infectious virus production was eliminated by growing the persistently infected cultures in the presence of anticytomegalovirus serum, approximately 45 genome equivalents of the viral DNA persisted per cell. The reassociation reaction approached completion. After removal of the antiserum and subculturing, infectious virus production resumed. Therefore, it was assumed that all sequences of the viral genome remained associated with these cells. Restriction of cytomegalovirus gene expression in persistently infected cell cultures is discussed.

Tumorigenicity and karyotype of rat embryo cell lines transformed by BK virus

A rat embryo cell line transformed by BK virus was used to induce tumors in rats. Cell lines were established from these tumors. Other sublines were obtained by in vitro cloning of the parental line. Growth characteristics and karyotypes were compared to the tumorigenicity of these cell lines. The in vitro cloned sublines had a low tumorigenicity. Tumorigenicity of the tumor cell lines varied from high to undetectable. The tumor cell line with the highest tumorigenicity also had the highest saturation density in vitro, but otherwise there was little correlation between tumorigenicity and the in vitro characteristics of the cells. Karyotype analysis was done for two cell lines with high or low tumorigenicity which both had a near-diploid complement of chromosomes. The findings were in agreement with the expression-supression model of Rabinowitz and Sachs (1970). The suppression chromosomes seemed to be confined in group A, the expression chromosomes in group B.

Recognition of virally transformed cells by lymphocytes from patients with prostatic cancer

Data presented describe the first assay using human peripheral blood lymphocytes (PBL) against two unique virally transformed cell lines in vitro. Human cells transformed by a cytomegalovirus (CMV-Mj) isolated from normal human prostate tissue were used as target cells in microcytoxicity assays with lymphocytes from 100 patients. Three target cell types were used: control human embryonic lung cells (HEL), transformed HEL cells (CMV-Mj-HEL-2), and transformed HEL cells retrieved from tumors induced in athymic nude mice (CMV-Mj-HEL-2, T-1) by injection of CMV-Mj-HEL-2 cells. PBL preparations from 84% of all patients tested significantly killed CMV-Mj-HEL-2, T-1 cells. However, only PBL from patients with prostatic carcinoma were cytotoxic for CMV-Mj-HEL-2 cells significantly more often than for control HEL. The implications of this approach are discussed.

Immune response of prostatic cancer patients to cytomegalovirus-infected and -transformed human cells

The indirect immunofluorescent test was used to determine the prevalence of humoral immunity to cytomegalovirus (CMV)-induced antigens in prostatic cancer patients as compared to age-matched controls. Significantly more prostatic cancer patients demonstrated high CMV-antibody titers than did the benign prostatic hyperplasia and nonurogenital cancer groups; however, no significant difference in reactivity was found between paients with prostatic cancer and transitional cell carcinoma of the urinary bladder. When screened against CMV-transformed human cell lines, the reactivity of the sera followed the rate of expression of CMV-related antigens of cell lines used in these tests.

Identification of a herpesvirus isolated from cytomegalovirus-transformed human cells

Human cells transformed by cytomegalovirus and transplanted to athymic nude mice yielded a cytopathic virus, Hershey Medical Center virus, following prolonged in vitro passage of the tumor cells. The virus is a double-enveloped herpesvirus, is sensitive to ether, and is inhibited by iododeoxyuridine. No significant antigenic relationship to herpes simplex virus was detected using herpes simplex virus-immune sera in neutralization and immunofluorescence tests, but indirect immunofluorescence tests revealed cytomegalovirus-related antigenicity. Further immunological tests revealed that Hershey Medical Center virus is antigenically indistinguishable from infectious bovine rhinotracheitis virus. Thus, it appears that Hershey Medical Center virus is infectious bovine rhinotracheitis virus, which presumably appeared in the cell culture as a contaminant from fetal calf serum.

Sequence of protein synthesis in cells infected by human cytomegalovirus: early and late virus-induced polypeptides

At least 10 distinct early virus-induced polypeptides were synthesized within 0 to 6 h after infection of permissive cells with cytomegalovirus. These virus-induced polypeptides were synthesized before and independently of viral DNA replication. A majority of these early virus-induced polypeptides were also synthesized in nonpermissive cells, which do not permit viral DNA replication. The virus-induced polypeptides synthesized before viral DNA replication were hypothesized to be nonstructural proteins coded for by the cytomegalovirus genome. Their synthesis was found to be a sequential process, since three proteins preceded the synthesis of the others. Synthesis of all early cytomegalovirus-induced proteins was a transient process; the proteins reached their highest molar ratios before the onset of viral DNA replication. Late viral proteins were synthesized at the time of the onset of viral DNA replication, which was approximately 15 h after infection. Their synthesis was continuous and increased in molar ratios with the accumulation of newly synthesized viral DNA in the cells. The presence of the amino acid analog canavanine or azetadine during the early stage of infection suppressed viral DNA replication. The amount of viral DNA synthesis was directly correlated to the relative amount of late viral protein synthesis. Because synthesis of late viral proteins depended upon viral DNA replication, the proteins were not detected in permissive cells treated with an inhibitor of viral DNA synthesis or in nonpermissive cells that are restrictive for cytomegalovirus DNA replication.

Infection of human amnion cells with cytomegalovirus

Human cytomegalovirus (CMV), known to replicate in vitro in human fibroblastic cells, was found to replicate in epithelial human amnion (HA) cells. Large syncytia formed in these cells after infection with CMV; inclusion bodies were observed in the nuclei, and CMV antigens were demonstrated in both the cytoplasm and the nucleus by indirect immunofluorescence techniques. The synthesis of virus DNA was also detected, and the production of infectious virus was followed. The titers were lower (from 10(4) to 6 X 10(5) using different isolates of CMV) than those obtained in human embryo fibroblast (HEF) cells, and the replication cycle was slower in HA than in HEF cells.

Lymphocyte reactivity against virally transformed cells in patients with urologic cancer

Lymphocytes from patients with urologic cancer were tested in microcytotoxicity assays against human cells transformed by cytomegalovirus. Human lymphocytes were significantly cytotoxic against the transformed cell line when compared to a normal human control cell line. Patients with prostatic carcinoma demonstrated greater target cell reduction than those with benign prostatic hyperplasia.

Evidence for the association of cytomegalovirus with carcinoma of the prostate

A human genital isolate of cytomegalovirus is shown to have transformed human embryonic lung cells in vitro. These cells produce tumors when injected into athymic nude mice. Two cell lines derived from tissue from human prostatic carcinoma have survived more than 20 passages in vitro and demonstrate cytomegalovirus-specific membrane antigen. Significant humoral antibody titers against cytomegalovirus have been demonstrated. Cell-mediated lymphocytotoxicity against these transformed cells has been demonstrated in patients with urinary tract tumors. This evidence indicates that an association between cytomegalovirus and human prostatic cancer may be more than coincidental.

Detection of latent cytomegalovirus in murine salivary and prostate explant cultures and cells

After infection of adult mice, cytomegalovirus was detectable in salivary gland suspensions by tissue culture inoculation for up to 3 months. After these cultures had become negative, virus apparently latent in these tissues could be detected in explants of salivary and prostate glands and in cell lines derived from these explants. In some cases cycles of virus-induced cell injury and regrowth were observed. Murine cytomegalovirus plaque efficiency and morphology were evaluated in prostate and salivary gland cell cultures derived from previously infected and uninfected mice. No evidence of interference was detected, although plaques size was altered (larger) in prostate cells from previously infected mice. These studies indicate the presence of a range of suppression, latency, or effects of murine cytomegalovirus detectable after the resolution of active infection and provide methods for additional study of the establishment and activation of virus latency.

Human cytomegalovirus: glycoproteins associated with virions and dense bodies

The glycoproteins associated with the membranes of cytomegalovirions and dense bodies were characterized by their relative mobility, percentage of glucosamine incorporation, and molecular weight. Eight glycopolypeptides were repeatedly detectable. Three glycopolypeptides of higher molecular weight with low levels of glucosamine incorporation were occasionally detectable. These latter glycopolypeptides may be precursors or aggregates of the glycopolypeptides with lower molecular weights. The glycoproteins associated with the membranes were on the surface, as determined by iodination with 125I of virions and dense bodies partially purified in gradients of D-sorbitol. Velocity centrifugation in linear gradients of D-sorbitol was used to obtain concentrated and partially purified preparations of infectious cytomegalovirus. Viral infectivity and the membranes of cytomegalovirions and dense bodies were stable in gradients of sorbitol, but cellular contaminants were not completely removed. Additional centrifugation in CsCl separated both cellular contaminants and viral nucleocapsids from virions and dense bodies. Many dense bodies, which are considered to be aberrant forms of cytomegalovirus, had the same size, sedimentation properties, and density as virions. Consequently, they were not separable from virions by various centrifugation techniques. Electron microscopy demonstrated that purified virions and dense bodies were qualitatively free of extraneous material and that each dense body was bounded by a membrane, as evidenced by its double-tract appearance. Antisera to a preparation of purified virions and dense bodies, or to their glycoproteins, contained antibodies that neutralized viral infectivity and reacted with antigens in cells infected with cytomegalovirus. However, these same antisera did not contain antibodies that reacted with uninfected cells. The glycoproteins associated with the membranes of cytomegalovirions and dense bodies are considered to be specified by the cytomegalovirus genome.

Oncogenic transformation of human embryo lung cells by human cytomegalovirus

Persistent infection of human embryo lung fibroblasts with a genital isolate of cytomegalovirus resulted in oncogenic transformation of these cells. Immunofluorescence techniques detected virus-specific antigens, while microcytotoxicity tests established that the transformed cells share a membrane antigen with hamster cells transformed by inactivated cytomegalovirus. The transformed human cells induced progressively growing tumors in weanling athymic nude mice.