Diseases produced by cytomegaloviruses

Routine Hematoxylin and Eosin Stain Is Specific for the Diagnosis of Cytomegalovirus Infection in Gastrointestinal Biopsy Specimens

BACKGROUND

Gastrointestinal cytomegalovirus (CMV) infection is a serious complication in immunocompromised patients; clinicians often expect expedited results for biopsy specimens. Our goal is to determine the accuracy of identification of CMV on hematoxylin and eosin (H&E) stain.

METHODS AND RESULTS

A total of 361 biopsy specimens from 273 patients with suspicion for CMV infection were retrieved. CMV was detected by immunohistochemistry (IHC) in 37 specimens acquired from 33 individual patients (average age = 54 years). Among the CMV-positive patients, 29 (88%) were reported to be immunosuppressed. Colon was the most common affected location. Of 37 CMV-positive specimens by IHC, 28 were positive by H&E (76%), 6 were negative (16%), and 3 were suspicious (8%). Of the 29 positive specimens on H&E, 28 were confirmed by IHC (97%) and 1 was indeterminate (3%). The sensitivity and specificity of H&E were 84% and 94%, respectively; the positive predictive value was 97%, and the negative predictive value was 93% ( P < .00001).

CONCLUSION

Our results show that a preliminary diagnosis of CMV infection, based on H&E stains, can be reported with high specificity and low risk for false-positive results. Suspicious cases should be deferred pending the result of IHC stains.

Cytomegalovirus Infection of Endocrine System in a Patient with Diffuse Large B-cell Lymphoma. Report of a Case

Cytomegalovirus (CMV) is an opportunistic pathogen causing different diseases in immunocompromised patients and leading to death in a high percentage of cases. CMV infection is also relatively frequent among patients with hematological malignancies, especially when treated with immunosuppressive agents. We describe the clinical history of a patient with stage IV diffuse large B-cell lymphoma (DLBCL) treated with eight courses of R-CHOP every two weeks, who presented clinical remission of the disease at the end of therapy. However, two months later he developed neurological symptoms due to cerebellar involvement and a subcutaneous dorsal lymphomatous infiltration. He had a partial response after chemotherapy and brain radiotherapy, but his clinical course was complicated by fever and hypotension. Although the fever resolved with broad-spectrum antibiotics, he presented progressive endocrine failure and died three weeks later. Autopsy confirmed disseminated multiorgan involvement by DLBCL associated with an unexpected CMV infection of the lungs and several endocrine organs including the pituitary gland, pancreatic islets and adrenals, a clinical association not previously reported in the English literature.

Looking for endoscopic features of cytomegalovirus colitis: a study of 187 patients with active ulcerative colitis, positive and negative for cytomegalovirus

BACKGROUND

Cytomegalovirus (CMV) is frequently detected in ulcerative colitis (UC) lesions of steroid-refractory patients. This has led to the suspicion that CMV might cause colitis and steroid refractoriness.

METHODS

During 2003 and 2011, 187 consecutive patients were divided into group I (n = 105), corticosteroid-free and thiopurine-free in the past 6 months, and group II (n = 82), all corticosteroid refractory. The combination of serum CMV immunoglobulin (Ig)M, CMV IgG, CMV antigenemia (Ag), and real-time polymerase chain reaction assays were performed to identify CMV(+) patients.

RESULTS

In group I, 79 patients were CMV IgG(+) and 26 patients were CMV IgG(-) and CMV IgM(-). In group II, 61 patients were CMV IgG(+), 1 CMV IgM(+), and 20 CMV IgG(-) and CMV IgM(-). All CMV IgG(+) patients were screened for CMV Ag. In group I, 6 of the 79 CMV IgG(+) patients were CMV Ag(+). In group II, 27 patients were CMV Ag(+). Colonoscopy was performed in all patients before screening for CMV. Similar colonoscopic features including punched out ulcers, geographic ulcers, and irregular ulcers were found in both CMV(+) and CMV(-) patients, without any striking difference between the 2 groups.

CONCLUSIONS

CMV reactivation might be encouraged by immunosuppressive drugs, like corticosteroids, immunomodulators, and therefore, patients with UC are at a high risk of CMV reactivation, potentially exacerbating UC. However, this study of 187 patients, CMV(+) and CMV(-), could not find colonoscopic features unique to CMV, except that CMV might be one factor for steroid refractoriness, and UC exacerbation.

The effect of murine cytomegalovirus IE-3 specific shRNA is dependent on intragenic target site due to multiple transcription initiation sites

BACKGROUND

Murine cytomegalovirus (MCMV) is closely related to human cytomegalovirus (HCMV) which is responsible for a variety of diseases, including retinitis, in immunocompromised individuals. Small inhibitory RNA molecules directed against essential viral regulatory genes may prove clinically useful.

METHODS

Small hairpin RNAs (shRNAs) directed against the essential MCMV immediate early-3 gene (IE-3) were designed and tested in vitro at m.o.i.'s of 2 and 0.2 to determine if virus replication could be inhibited.

RESULTS

At m.o.i. = 2, a MCMV IE-3 specific shRNA specific for sequences at the beginning of exon 5 inhibited virus replication with a maximum decrease in virus titer of approximately two logs at day 5 p.i. Surprisingly, however, at m.o.i. = 0.2, the same shRNA enhanced virus replication. In the latter case, the main IE-3 product observed in infected cells was not the expected 88 kd full length IE-3 protein observed at high m.o.i. but rather a truncated 45 kd form of this protein. Rapid analysis of 5' cDNA ends (5' RACE) indicated that substantial differences exist in the transcript profile produced by the IE-3 gene at low and high m.o.i. early after infection and that multiple transcripts are produced under both conditions. One such transcript, which originated in exon 5 of the IE-3 gene, was located outside the region targeted by our shRNA and was the major transcript produced at low m.o.i. Targeting of this exon 5 transcript with a second shRNA resulted in inhibition of virus replication at both low and high m.o.i.

CONCLUSIONS

These studies indicate that IE-3 has a complex transcriptional profile and that shRNA targeting of this and other viral regulatory genes which produce multiple transcripts may have unexpected effects on virus replication.

A case of cytomegalovirus colitis following immunosuppressive treatment for pyoderma gangrenosum

We report a case of pyoderma gangrenosum (PG) complicated by cytomegalovirus (CMV)-induced colitis. A 79-year-old woman with PG was treated with corticosteroid and cyclosporin. She had blood in her stool and advancing anemia during the treatment. A colonoscopic biopsy specimen from the colon revealed typical CMV-infected cells with CMV inclusions confirmed by immunohistochemistry. Furthermore, there were many CMV-antigen-positive leukocytes, suggesting an active CMV infection, which is serious in compromised hosts. Although ulcerative colitis and Crohn's disease are well known as complications of PG, CMV enterocolitis should be considered in the differential diagnosis of enterocolitis in immunocompromised patients.

Viral prophylaxis in organ transplant patients

Viral pathogens have emerged as the most important microbial agents having deleterious effects on solid organ transplant (SOT) recipients. Antiviral chemoprophylaxis involves the administration of medications to abort transmission of, avoid reactivation of, or prevent progression to disease from, active viral infection. Cytomegalovirus (CMV) is the major microbial pathogen having a negative effect on SOT recipients. CMV causes infectious disease syndromes, augments iatrogenic immunosuppression and is commonly associated with opportunistic superinfection. CMV has also been implicated in the pathogenesis of rejection. Chemoprophylactic regimens for CMV have included oral aciclovir (acyclovir) at medium and high doses, intravenous and oral ganciclovir, and the prodrugs valaciclovir (valacyclovir) and valganciclovir. CMV prophylactic strategies should be stratified, with the highest-risk patients receiving the most 'potent' prophylactic regimens. Herpes simplex virus (HSV) reactivation in SOT recipients is more frequent, may become more invasive, takes longer to heal, and has greater potential for dissemination to visceral organs than it does in the immunocompetent host. Prophylactic regimens for CMV are also effective chemoprophylaxis against HSV; in the absence of CMV prophylaxis, aciclovir, valaciclovir or famciclovir should be used as HSV prophylaxis in seropositive recipients. Primary varicella-zoster virus (VZV) after SOT is rare and most commonly seen in the paediatric transplant population because of VZV epidemiology. Zoster occurs in 5-15% of patients, usually after the sixth post-transplant month. Prophylactic regimens for zoster are neither practical nor cost effective after SOT because of the late onset of disease and low proportion of affected individuals. All SOT recipients should receive VZV immune globulin after contact with either varicella or zoster. Epstein-Barr virus has its most significant effect in SOT as the precipitating factor in the development of post-transplant lymphoproliferative disorders. Antiviral agents that could be effective are the same as those used for CMV, but indications for and effectiveness of prophylaxis are poorly established. Hepatitis B virus (HBV) and hepatitis C virus (HCV) are important pathogens in the SOT population as indications for transplantation. So-called 'prophylaxis' for recurrent HBV and HCV after liver transplantation is controversial, suppressive rather than preventive, and potentially lifelong. Influenza infection after SOT is acquired by person-to-person contact. During epidemic periods of influenza, transplant populations experience a relatively high frequency of infection, and influenza may affect immunosuppressed SOT recipients more adversely than immunocompetent individuals. Antiviral medications for prevention of influenza are administered as post-exposure prophylaxis to SOT recipients, in addition to yearly vaccine, in circumstances such as influenza epidemics and nosocomial outbreaks, and after exposure to a symptomatic individual during 'flu season'.

Down-regulation of surface major histocompatibility complex class I by guinea pig cytomegalovirus

Live attenuated strains of human cytomegalovirus are under development as vaccines to prevent birth defects resulting from congenital infections. These strains encode four proteins that inhibit surface expression of MHC class I, presumably to evade cytotoxic T-cell recognition and, perhaps, attenuate induction of immunity. To initiate studies of the role of class I down-regulation on congenital infection and vaccine efficacy, the ability of guinea pig cytomegalovirus to down-regulate class I was examined. Surface class I was specifically down-regulated on infected cells up to 8-fold. Sensitivity to UV irradiation and insensitivity to a viral DNA synthesis inhibitor revealed that immediate early or early viral gene(s) are responsible. Identification of these genes will permit future experiments to evaluate the role of class I down-regulation in congenital cytomegalovirus disease and its impact on vaccine efficacy. These findings should be pertinent to understanding human cytomegalovirus disease and may help guide the design of candidate vaccines.

Late and atypical cytomegalovirus disease in solid-organ transplant recipients

Posttransplantation cytomegalovirus (CMV) disease typically occurs 1-4 months after solid-organ transplantation. The case definition invariably includes unexplained fever for > or =3 days, often with leukopenia. Late and atypical presentation of CMV disease has been rarely reported. Five cases of late and atypical CMV disease in heart (n = 1), liver (n = 1), and kidney (n = 3) transplant recipients occurred within a 4-month period in early 1999. These patients presented at a median of 25 months after organ transplantation (range, 6 months to 22 years). Atypical findings included absence of fever in 3 patients, elevated white blood cell counts in 4 patients, and normal platelet counts in 4 patients. Four patients were at risk for primary CMV infection, and 3 received ganciclovir prophylaxis for 3 months. One patients was treated for rejection, and 2 patients had induction muromonab-CD3 (Orthclone; Orthobiotech). Two of the patients had pulmonary CMV disease, but neither of these patients had hypoxia. Two patients had enterocolitis, one of whom had chronic colitis for a year. These cases may represent a changing epidemiology and clinical presentation of CMV disease in solid-organ transplant recipients in an era of changing immunosuppression and improved CMV disease prevention in the early posttransplantation period.

Cytomegalovirus colitis complicating ulcerative colitis in the steroid-naive patient

We report a case of cytomegalovirus (CMV) presenting as acute refractory colitis in a patient with a pre-existing 14-month history of ulcerative colitis (UC) who had never previously been treated with corticosteroids or immunosuppressants. A review of existing literature and previous cases of patients with coincident CMV and UC are examined, stratifying these cases based upon absence or presence of corticosteroid use. To date, only five previous case reports of CMV colitis in patients naive to corticosteroids have been described, and only one previous case has had UC diagnosed over 4 wk before the development of CMV colitis. We further discuss the relationship between these two diseases as well as the diagnosis, treatment, patient characteristics, and outcome of CMV infection of the colon in patients with underlying UC. We discuss the need to consider the diagnosis of CMV colitis in patients with refractory UC who are not receiving corticosteroid treatment as well as those who are refractory and are being treated with immunosuppressants and/or corticosteroids.

Cytomegalovirus colitis after administration of docetaxel-5-fluorouracil-cisplatin chemotherapy for locally advanced hypopharyngeal cancer

We present the case of a patient with a locally advanced hypopharyngeal carcinoma who developed a severe cytomegalovirus (CMV) colitis after his first chemotherapy course with 5-fluorouracil (5-FU), docetaxel and cisplatin. The most probable cause of his CMV colitis is the impaired immunity during a phase of neutropenia after the chemotherapy. Although there was amelioration of the colitis and clinical status after treatment with ganciclovir, the patient later deteriorated and died due to recurrent bacterial infections. This is the third reported case of CMV colitis treated with ganciclovir in a patient with a solid tumour. It is the first report of CMV colitis after docetaxel containing chemotherapy. Although CMV colitis is most frequently observed in immunosuppressed patients such as those with acquired immune deficiency syndrome (AIDS), transplants and corticosteroid treatment, it has also been reported in less immunosuppressed (elderly, malnourished,...) and even non-immunosuppressed patients. CMV infection should therefore be included in the differential diagnosis of GI disease in all patients, and when suspected, the clinician should pursue appropriate diagnostic and therapeutic interventions.

CREB and CREB-binding proteins play an important role in the IE2 86-kilodalton protein-mediated transactivation of the human cytomegalovirus 2.2-kilobase RNA promoter

The human cytomegalovirus (HCMV) immediate-early region 2 86-kDa protein (IE2 86) is the major transactivator of the promoter for the 2.2-kb class of early RNAs (open reading frame UL 112-113). Previously, we reported that a DNA segment on this promoter between nucleotides (nt) -113 and -59 was critical for activation by IE2 86 in vivo and could be bound by IE2 86 in vitro (R. Schwartz, M. H. Sommer, A. Scully, and D. H. Spector, J. Virol. 68:5613-5622, 1994). With a set of site-specific mutations within nt -84 to -61, we have localized the essential cis-acting sequences to nt -72 to -61, which contain an ATF/CREB-binding site. The IE2 86-binding site between nt -113 and -85 is not essential for activation of the promoter by IE2 86 in transient-expression assays, but its presence can enhance the level of activation mediated through the sequences located between nt -84 and -59. Electrophoretic mobility shift assays with a segment containing nt -84 to -59 and nuclear extracts from human cells permissive for the HCMV infection revealed a complex band pattern. However, by supershift analysis with specific antibodies, we were able to identify CREB as the major ATF/CREB family member in the protein-DNA complexes. Further evidence that CREB is a target for IE2 86-mediated induction, is provided by the finding that IE2 86 activates the somatostatin promoter to high levels. Although the binding of IE2 86 to nonphosphorylated full-length CREB or deltaCREB is minimal, IE2 86 does form complexes with p300 and the CREB-binding protein (CBP), which in turn bind to CREB and can serve as adaptor proteins for CREB function. In addition, the in vivo functional relevance of the interaction between IE2 86 and CBP is indicated by the ability of IE2 86 to enhance transcriptional activation mediated by a GAL4-CBP fusion protein brought to a promoter by GAL4-binding sites.

Immunosuppression induces transcription of murine cytomegalovirus glycoprotein H in the eye and at non-ocular sites

In these studies, DNA PCR was used to identify sites of murine cytomegalovirus (MCMV) latency after inoculation of virus into the supraciliary space of the eye. Reverse transcription (RT) PCR for an immediate early gene and a late gene was used to identify putative sites of virus reactivation after methylprednisolone (steroid)-induced immunosuppression. Ten weeks after inoculation of 5 x 10(2) PFU of MCMV, BALB/c mice were immunosuppressed by intramuscular injection of steroid. Control mice were infected but not immunosuppressed. Two weeks after initiation of immunosuppression, mice were sacrificed. DNA and RNA extracted from homogenized tissues were amplified for immediate early gene 1 (IE1) and late gene, glycoprotein H (gH), DNA and mRNA by PCR and RT-PCR, respectively. Replicating virus was detected in homogenized ocular and non-ocular tissues by plaque assay. In the latently infected PBS-treated control group, viral DNA was detected in the inoculated eye and in several non-ocular tissues; IE1 mRNA was found in most of the DNA-positive tissues, while gH mRNA was amplified only in a few of the MCMV DNA-positive tissues from a single mouse. After immunosuppression, viral DNA and IE1 mRNA were detected at a higher frequency in various tissues of steroid-treated mice. gH mRNA was detected in a significantly higher number of the inoculated eyes, salivary glands and other non-ocular tissues of steroid-treated mice. After immunosuppression, low titers of infectious virus were recovered from the salivary glands of steroid-treated mice, but infectious virus was not recovered from the inoculated eye of either steroid-treated of non-immunosuppressed mice. The DNA PCR results suggest that after inoculation of 5 x 10(2) PFU of MCMV into the supraciliary space of euthymic BALB/c mice, virus becomes latent in the inoculated eye, salivary gland and other extraocular tissues. The RT-PCR results suggest that latent MCMV can be reactivated in multiple tissues by immunosuppression.

Cytomegalovirus infection induces high levels of cyclins, phosphorylated Rb, and p53, leading to cell cycle arrest

Human cytomegalovirus (HCMV) infection stimulates cellular DNA synthesis and causes chromosomal damage. Because such events likely affect cellular proliferation, we investigated the impact of HCMV infection on key components of the cell cycle. Early after infection, HCMV induced elevated levels of cyclin E, cyclin E-associated kinase activity, and two tumor suppressor proteins, p53 and the retinoblastoma gene product (Rb). The steady-state concentration of Rb continued to rise throughout the infection, with most of the protein remaining in the highly phosphorylated form. At early times, HCMV infection also induced cyclin B accumulation, which was associated with a significant increase in mitosis-promoting factor activity as the infection progresses. In contrast, the levels of cyclin A and cyclin A-associated kinase activity increased only at late times in the infection, and the kinetics were delayed relative to those for cyclins E and B. Analysis of the cellular DNA content in the infected cells by flow cytometry showed a progressive shift of the cells from the G1 to the S and G2/M phases of the cell cycle, leading to an accumulation of aneuploid cells at late times. We propose that these HCMV-mediated perturbations result in cell cycle arrest in G2/M.

The human cytomegalovirus IE2 86-kilodalton protein interacts with an early gene promoter via site-specific DNA binding and protein-protein associations

The 86-kDa immediate-early 2 protein (IE2 86) of human cytomegalovirus is a powerful transactivator of homologous and heterologous promoters, including the human cytomegalovirus 1.2-kb RNA early promoter. Two potential mechanisms for gene activation by IE2 86 include interaction with cellular proteins and direct DNA binding. In this report, we show that the 1.2-kb RNA promoter contains a cis-acting AP-1 site, critical for its activation by IE2 86 in vivo, and that IE2 86, purified as a glutathione S-transferase-IE86 fusion protein, can interact with c-Jun and JunB. Additionally, by coimmunoprecipitation, we document that JunB and IE2 86 do associate in vivo. Further in vitro analysis reveals that Fos proteins are able to associate with glutathione S-transferase-IE86 only when present as a Jun-Fos heterodimer. With a set of IE2 86 mutants, we demonstrate that three independent regions of the IE2 86 interact in vitro with c-Jun, two of which are essential for activation of the 1.2-kb RNA promoter in vivo. We also show that IE2 86 can bind directly to this promoter through a sequence located just upstream of the AP-1 site between nucleotides -125 and -97. This discrete domain shares sequence homology with the cis-repression signal on the IE gene.

Analysis of the role of CD4+ T-cells during murine cytomegalovirus infection in different strains of mice

We examined the role of CD4+ T-cells in peritoneal exudate cells (PECs) during the course of acute murine cytomegalovirus (MCMV) infection in two strains of mice. Cell counts of PECs and cytofluorometric analysis showed that C57BL/6, a resistant strain, had more CD4+ T-cells than BALB/c, a susceptible strain, after intraperitoneal infection of 3 x 10(3) PFU of the Smith strain of MCMV, though both strains had an equivalent number of CD8+ T-cells. CD4+ T-cells of both strains expressed mRNA of IFN-gamma, IL-2, and IL-4 on days 5 and 7 after infection, with much higher expression of these cytokines in C57BL/6 than in BALB/c. At the same time point after infection, macrophages were shown to express mRNA of IL-1 alpha and TNF-alpha with higher expression of IL-1 alpha in C57BL/6 than in BALB/c. Production of nitric oxide, recently shown to be one of the antiviral effector mechanisms of macrophages, by macrophages of both strains was examined showing more production of nitric oxide on day 7 after infection in C57BL/6 than in BALB/c. From these findings, we suggest the possibility that CD4+ T-cells contribute to the protection against MCMV infection via the secretion of cytokines and the resultant activation of macrophages to produce nitric oxide.

Stability of cytomegalovirus antibodies in plasma during prolonged storage of blood components

Cytomegalovirus (CMV) antibody testing is currently limited by manufacturers' guidelines to specimens stored for 7 days or less. We examined the stability of CMV antibodies in plasma from platelets and whole-blood units during storage using a rapid, automated, recombinant protein-based immunoassay which qualitatively detects total antibody to human CMV. Testing of single-donor apheresis platelets was performed on baseline serum and platelet-free plasma and on platelet-free plasma 8 days later. Indeterminate, positive, and negative CMV antibody results were maintained over time for 97% (75 of 77) of the platelet specimens. For whole-blood units, initial testing of donor serum and plasma obtained from erythrocyte segments took place within 7 days of phlebotomy. Indeterminate, positive, and negative CMV antibody results were maintained on subsequent analyses performed on erythrocyte segments at 2, 4, 6, and 8 weeks for 100% of whole-blood specimens. An important potential benefit of CMV antibody testing of stored platelets and blood is the elimination of a costly, dedicated, CMV-negative inventory. The study suggests that CMV antibody testing can be conveniently and reliably performed on blood components over the entire storage period.

Use of recombinant virus to assess human cytomegalovirus early and late promoters in the context of the viral genome

We have developed a system to study human cytomegalovirus (HCMV) cis-acting promoter elements within the context of the viral genome. A recombinant HCMV (RV134) containing a marker gene (beta-glucuronidase) was used to insert HCMV promoter-chloramphenicol acetyltransferase gene constructs into the viral genome between open reading frames US9 and US10. Using this system, we have studied the promoters for the early DNA polymerase gene (UL54), the early-late lower matrix phosphoprotein gene (pp65, UL83), and the true late 28-kDa structural phosphoprotein gene (pp28, UL99). Transient-expression assays demonstrated that the pp65 and pp28 promoters are activated earlier and to higher levels than typically observed with the endogenous gene. In contrast, insertion of these promoters into the viral genome resulted in kinetics which mimicked that of the endogenous genes. In addition, we have also tested a variant of the pp28 promoter (d24/26CAT) which is deleted from -609 to -41. This promoter behaved similarly to the wild-type pp28 promoter, indicating that sequences from -40 to +106 are sufficient for conferring true late kinetics. Taken together, these data demonstrate that the viral genome affords a level of regulation on HCMV gene expression that has been previously unrealized. Therefore, these experiments provide a model system for the analysis of cis-acting promoter regulatory elements in the context of the viral genome.

The human cytomegalovirus origin of DNA replication (oriLyt) is the critical cis-acting sequence regulating replication-dependent late induction of the viral 1.2-kilobase RNA promoter

Plasmid constructs containing the 1.2-kb RNA promoter from the long terminal repeat region of human cytomegalovirus (HCMV) display the early-phase regulation of this promoter but lack the characteristic late induction (E. J. Wade, K. M. Klucher, and D. H. Spector, J. Virol. 66:2407-2417, 1992). To determine if the HCMV origin of replication (oriLyt) was necessary and sufficient for the late induction of the 1.2-kb RNA promoter, we cloned a 9.6-kbp segment of the origin of replication onto the p456 OCAT plasmid containing the 1.2-kb RNA promoter. This plasmid was designated ori456 OCAT. A control construct, which contains all of the same sequences as the ori456 OCAT construct except that a 2.4-kbp segment derived from HCMV EcoRI segment U is inverted in orientation to disrupt the origin function, was designated inv456 OCAT. After electroporation into human fibroblast cells and infection with HCMV 24 h later, ori456 OCAT replicated and showed the same early and late transcription pattern as the authentic viral 1.2-kb RNA. Under similar conditions, the inv456 OCAT neither replicated nor showed late induction. Experiments using plasmids synthesized in bacteria lacking methylation activity demonstrated that the late induction was not dependent on the change in methylation state of the plasmids. Ganciclovir, an inhibitor of the HCMV DNA polymerase, was used to demonstrate the replication dependence of the expression of the virally encoded 1.2-kb RNA, while the nearby early 2.7-kb RNA was unaffected. Ganciclovir also inhibited the late induction of the chloramphenicol acetyltransferase gene from ori456 OCAT, while expression from inv456 OCAT increased. Site-specific mutations in two previously identified important regulatory elements of the 1.2-kb RNA promoter, the AP1-binding site and the CATA site, indicated that these sites continue to contribute to promoter activity at late times but that the replication-dependent late induction acts independently of these sites. Possible mechanisms underlying the late induction are discussed.

Site-specific binding of the human cytomegalovirus IE2 86-kilodalton protein to an early gene promoter

We have previously demonstrated that the human cytomegalovirus (HCMV) immediate-early region 2 86-kDa protein (the IE2 86 protein) is the major transactivator of the HCMV early promoter for the 2.2-kb class of RNAs (open reading frame UL 112-113). Here we show that specific stimulation of this promoter by IE2 86 in transient-expression assays requires sequences located between nucleotides (nt) -113 and -58 relative to the transcription start site; this is also the major regulatory region for this promoter during HCMV infection. To determine whether IE2 86 can bind to this promoter, a glutathione-S-transferase (GST)-IE2 86 fusion protein was incubated with the 32P-labeled promoter and specific binding was assessed by retention of the protein-DNA complex on glutathione-agarose beads. DNase I footprint analysis was also used to map the sequences involved in the binding. Our results indicate that three regions, located between nt -286 and -257, nt -248 and -218, and nt -148 and -120, bind strongly to the IE2 86 protein and share sequence similarity with the previously identified cis repression signal located near the cap site of the major HCMV IE gene. In addition, there is a weaker binding region between nt -113 and -85, which shares some sequence homology with the cis repression signal element and the strong binding regions of the 2.2-kb RNA promoter but lacks one of the two CG dinucleotides present in all of the high-affinity binding sites. With a set of IE2 86 protein deletion mutants, we also show that the DNA-binding domain spans a large region in the carboxy-terminal half of the protein.

The human cytomegalovirus 86-kilodalton immediate-early 2 protein: synthesis as a precursor polypeptide and interaction with a 75-kilodalton protein of probable viral origin

The immediate-early 2 (IE2) 86-kDa polypeptide, a major immediate-early gene product of human cytomegalovirus, regulates transcription both positively and negatively. We report two new properties of the IE2 86-kDa polypeptide in infected cells. Immunoprecipitation of infected cell proteins from human embryonic lung cells by antipeptide or monoclonal antibodies specific for IE2 epitopes revealed three closely migrating polypeptide species. The slowest, p86, behaved as expected for the mature 86-kDa IE2 polypeptide. The middle species, p80, was immunoprecipitated from denatured as well as native samples and labeled to steady state rapidly. Pulse-chase analysis demonstrated directly that p80 was a metabolic precursor to p86. The fastest-migrating species, p75, was not detected by probing blots of the immunoprecipitated proteins with IE2-specific antisera; p75 was not precipitated from denatured protein samples; and the products of partial proteolysis of p75 were distinct from those of p86. These properties established p75 as an unrelated coprecipitated polypeptide complexed with p86. The p75 proteins coprecipitated from cells infected with two different strains of human cytomegalovirus, AD169 and Towne, had different mobilities. p75 was detected as early as 6 h and as late as 72 h after infection, but it was not synthesized in cells released from a cycloheximide block. Thus, it is likely that p75 is an early viral protein.

In vivo and in vitro analysis of transcriptional activation mediated by the human cytomegalovirus major immediate-early proteins

To define mechanistically how the human cytomegalovirus (HCMV) major immediate-early (IE) proteins induce early-gene transcription, the IE1 72-kDa protein, the IE2 55-kDa protein, and the IE2 86-kDa protein were analyzed for their ability to activate transcription from an HCMV early promoter in vivo and in vitro. In transient-expression assays in U373MG astrocytoma/glioblastoma and HeLa cells, only the IE2 86-kDa protein was able to activate the HCMV early promoter to high levels. In HeLa cells, the IE1 72-kDa protein was able to activate the promoter to a low but detectable level, and the level of promoter activity observed in response to the IE2 86-kDa protein was increased synergistically following cotransfection of the constructs expressing both IE proteins. To examine the interaction of the HCMV IE proteins with the RNA polymerase II transcription machinery, we assayed the ability of Escherichia coli-synthesized proteins to activate the HCMV early promoter in nuclear extracts prepared from U373MG cells, HeLa cells, and Drosophila embryos. The results of the in vitro experiments correlated well with those obtained in vivo. The basal activity of the promoter was minimal in both the HeLa and U373MG extracts but was stimulated 6- to 10-fold by the IE2 86-kDa protein. With a histone H1-deficient extract from Drosophila embryos, the HCMV early promoter was quite active and was stimulated two- to fourfold by the IE2 86-kDa protein. Addition of histone H1 at 1 molecule per 40 to 50 bp of DNA template significantly repressed basal transcription from this promoter. However, the IE2 86-kDa protein, but none of the other IE proteins, was able to counteract the H1-mediated repression and stimulate transcription at least 10- to 20-fold. The promoter specificity of the activation was demonstrated by the inability of the IE2 86-kDa protein to activate the Drosophila Krüppel promoter in either the presence or absence of histone H1. These results suggest that one mechanism of transcription activation by the IE2 86-kDa protein involves antirepression.

In vivo and in vitro analysis of transcriptional activation mediated by the human cytomegalovirus major immediate-early proteins

To define mechanistically how the human cytomegalovirus (HCMV) major immediate-early (IE) proteins induce early-gene transcription, the IE1 72-kDa protein, the IE2 55-kDa protein, and the IE2 86-kDa protein were analyzed for their ability to activate transcription from an HCMV early promoter in vivo and in vitro. In transient-expression assays in U373MG astrocytoma/glioblastoma and HeLa cells, only the IE2 86-kDa protein was able to activate the HCMV early promoter to high levels. In HeLa cells, the IE1 72-kDa protein was able to activate the promoter to a low but detectable level, and the level of promoter activity observed in response to the IE2 86-kDa protein was increased synergistically following cotransfection of the constructs expressing both IE proteins. To examine the interaction of the HCMV IE proteins with the RNA polymerase II transcription machinery, we assayed the ability of Escherichia coli-synthesized proteins to activate the HCMV early promoter in nuclear extracts prepared from U373MG cells, HeLa cells, and Drosophila embryos. The results of the in vitro experiments correlated well with those obtained in vivo. The basal activity of the promoter was minimal in both the HeLa and U373MG extracts but was stimulated 6- to 10-fold by the IE2 86-kDa protein. With a histone H1-deficient extract from Drosophila embryos, the HCMV early promoter was quite active and was stimulated two- to fourfold by the IE2 86-kDa protein. Addition of histone H1 at 1 molecule per 40 to 50 bp of DNA template significantly repressed basal transcription from this promoter. However, the IE2 86-kDa protein, but none of the other IE proteins, was able to counteract the H1-mediated repression and stimulate transcription at least 10- to 20-fold. The promoter specificity of the activation was demonstrated by the inability of the IE2 86-kDa protein to activate the Drosophila Krüppel promoter in either the presence or absence of histone H1. These results suggest that one mechanism of transcription activation by the IE2 86-kDa protein involves antirepression.

Hirschsprung's disease: a viral etiology?

This study investigates the hypothesis that Hirschsprung's disease (HD), congenital rectal aganglionosis, may be etiologically linked to antenatal cytomegalovirus (CMV) infection. Bowel specimens from 72 HD patients, 144 control I infants (Hirschsprung-like symptoms, normal histology), and 36 control II infants (deaths from nongastrointestinal causes) were analyzed for CMV genomes by polymerase chain reaction. Positive results were obtained in 6 HD patients (8.8%) and none of the controls. Our findings suggest that antenatal CMV infection, a potentially preventable condition, may be one of the etiological factors in HD.

An AP-1 binding site is the predominant cis-acting regulatory element in the 1.2-kilobase early RNA promoter of human cytomegalovirus

To extend our analysis of the regulation of human cytomegalovirus (HCMV) early gene expression, we examined a transcription unit located in the terminal repeats of the long segment of the viral genome. This region encodes a major 1.2-kb RNA which is induced at early times in infection but undergoes its largest increase in abundance after the onset of viral DNA replication. To identify the important cis-acting regulatory elements for this gene, two constructs were prepared for use in transient expression assays. One contained 413 bp of the upstream sequence and 43 bp of the leader sequence fused to the gene for chloramphenicol acetyltransferase (CAT). The second construct included 1,722 bp upstream of the start site of the 1.2-kb RNA, the entire transcribed region with an additional 166-bp insert derived from the CAT gene as an assayable marker, and 2,393 bp downstream of the polyadenylation signal. Both constructs were individually transfected into human fibroblast cells, and the cells were infected with HCMV. RNA specified by the hybrid construct was initiated at the correct position and accumulated with the same kinetics as the authentic viral transcript at early times in the infection but did not undergo the increase in abundance at late at late times. By 5'-end-deletion analysis, we determined that the promoter for the 1.2-kb RNA contains a number of cis-acting elements, the most significant of which are the TATA-like sequence CATAAA at -30 and a sequence corresponding to the binding site for the transcription factor AP-1 at -75. Using extracts prepared from HeLa cells as well as from infected and uninfected fibroblasts in gel retardation assays, we obtained evidence for the specific interaction of a cellular factor(s) with the AP-1 binding site. The pattern of binding differed in the HeLa and fibroblast cells but did not change as a function of the HCMV infection. However, the functional importance of the AP-1 binding site and its key role in the regulation of the 1.2-kb RNA was supported by analysis of constructs containing specific point mutations at this site in gel retardation and transient expression assays. Site-specific mutations in the AP-1 consensus sequence, which resulted in the complete loss of binding to cellular factors, eliminated the basal activity and reduced the inducible promoter activity by eightfold.

Cytomegalovirus infection in Gambian mothers and their babies

A 15 month longitudinal study of cytomegalovirus (CMV) infection in 178 Gambian mothers and their babies was undertaken. Twenty five (14%) of the babies were congenitally infected despite the fact that 87% of their mothers were antibody positive to the virus. Two of the 25 congenitally infected infants had evidence of severe neurological damage; skin sepsis was also a prominent feature in congenitally infected infants. The other children soon became infected. At 6 months of age, 53% of the infants were shedding virus either in urine or saliva. By the age of 12 months 86% of the infants had serological evidence of CMV infection. Preliminary evidence suggests that sibling to sibling infection in crowded compounds might be a major route of transmission.

The human cytomegalovirus 2.7-kilobase RNA promoter contains a functional binding site for the adenovirus major late transcription factor

We have examined the factors which influence the expression of a major 2.7-kilobase (kb) early transcript encoded by the long repeat of the human cytomegalovirus (HCMV) strain AD169 genome. Previously, by deletion analysis, we determined that the promoter for this early RNA consisted of multiple cis-acting elements (Klucher et al., J. Virol. 63:5334-5343, 1989). Using extracts prepared from HeLa cells as well as from infected and uninfected foreskin fibroblasts, we also obtained evidence for the interaction of a cellular factor with one of these elements. In this study, we have further defined the specificity and functional importance of this binding. On the basis of DNase I footprinting and methylation interference assays, we localized the site of interaction to a region (nucleotides -113 to -106 relative to the mRNA start site) which contains homology to the binding site for the adenovirus major late transcription factor (MLTF), also referred to as the upstream stimulatory factor (USF). The contact points of binding between the cellular factor and the guanine residues within this segment were consistent with the pattern of binding for USF/MLTF. Additionally, by using oligonucleotides containing the binding sites for USF/MLTF from the adenovirus major late promoter and the HCMV 2.7-kb RNA promoter as competitors in gel retardation assays, we were able to show that USF/MLTF bound to the two promoters with similar affinity. Correlation of the binding activity with in vivo functional importance was provided by mutagenesis and transient-expression assays. A point mutation within the HCMV USF/MLTF site lowered the affinity of binding 5- to 10-fold and decreased the inducible activity of the HCMV 2.7-kb RNA promoter by approximately 50%. Furthermore, the addition of the HCMV USF/MLTF site to a minimal 2.7-kb RNA promoter containing only the TATA sequence resulted in an increase in HCMV inducible transcriptional activity of 6- to 20-fold. However, the HCMV USF/MLTF site could not functionally substitute for the TATA sequence. These studies further support the idea that for maximal response to the HCMV infection, the 2.7-kb RNA promoter requires multiple cis-acting sequences, two of which include the binding sites for USF/MLTF and TFIID.

Detection of an IE responsive element(s) in the BamHI J fragment of human cytomegalovirus AD169

The BamHI J fragment of human cytomegalovirus (HCMV) AD169 located at 0.815 to 0.855 map units in the unique short component of the genome was demonstrated to be responsive to the HCMV IE proteins by using a transient chloramphenicol acetyltransferase (cat) gene expression system. The BamHI J fragment was cloned into a cat gene expression plasmid and then cotransfected with a plasmid that expresses the immediate early (IE) genes of HCMV AD169 into the HCMV permissive cell line MRC-5. The results indicated that the BamHI J fragment enhanced cat gene expression 10-fold when the HCMV IE proteins were present. The BamHI J fragment was demonstrated to have properties of an inducible enhancer. In the presence of the HCMV IE proteins, it enhances cat gene expression when positioned in either orientation both upstream and downstream from the cat gene; it enhances transcription from the herpes simplex virus type 1 (HSV-1) thymidine kinase gene and the simian virus 40 (SV40) early gene promoters; and it requires a cis-positioned promoter for enhancer activity.

Isolated cytomegalovirus ileitis detected by colonoscopy

Cytomegalovirus infections in immunocompromised patients mimic graft-versus-host disease by causing abdominal pain, watery diarrhea, and protein-losing enteropathy. The cases of three bone marrow transplant patients with diarrheal illness and biopsy-proven graft-vs.-host disease are reported. Isolated cytomegalovirus enteritis was subsequently identified by endoscopic examination and biopsy of the terminal ileum. All three improved with the eventual institution of 9-(1,3-dihydroxy-2-propoxymethyl) guanine. Ileoscopy is important in addition to colonoscopy in bone marrow transplant patients with diarrhea if cytomegalovirus enteritis is to be identified and appropriately treated.

Rapid antiviral DNA-DNA hybridization assay for human cytomegalovirus

A rapid DNA-DNA hybridization technique that can be accomplished in 4 to 5 days was compared with plaque reduction assay to determine its reliability in performing antiviral assays for human cytomegalovirus (HCMV). The assay involves lysing infected cells, direct wicking of denatured DNA onto membranes and hybridization using a 125I-labeled HCMV DNA probe. Using ten ganciclovir sensitive clinical HCMV strains for comparison, the DNA hybridization technique correlated well with the plaque assay. Clinical HCMV strains previously identified as resistant to ganciclovir were also readily identified. The DNA-DNA hybridization assay is less tedious and more rapid than plaque reduction assays, and thus, provides an excellent alternative for evaluation of the antiviral activity of drugs against HCMV.

Severe haemolytic anaemia due to cold anti-'i' antibodies associated with cytomegalovirus infection

A 66 year old patient with multiple myeloma and monoclonal cryoglobulinaemia who developed a severe haemolytic anaemia following a cytomegalovirus infection is reported. The presence of a high titre of anti-'i' cold antibody of IgM subclass is demonstrated. Anti-'i' antibody disappeared when complement-fixation antibody titres against cytomegalovirus decreased. Various pathogenetic mechanisms involved in the development of haemolytic anaemia associated with cytomegalovirus infection are discussed. To our knowledge, this is the first case described in the English language publications associating severe haemolytic anaemia with an anti-'i' antibody after a cytomegalovirus infection in an immunocompromised patient.

Sequences in the human cytomegalovirus 2.7-kilobase RNA promoter which mediate its regulation as an early gene

We have studied the regulation of expression of a major human cytomegalovirus (HCMV) early transcription unit located within the long repeat of the strain AD169 genome. This region specified a 2.7-kilobase RNA which underwent its largest increase in abundance between 8 and 14 h postinfection. To study the regulation of this gene, its promoter was cloned 5' of the gene for chloramphenicol acetyltransferase (CAT) for use in transient expression assays. A construct containing 651 base pairs of upstream sequence and 54 base pairs of leader sequence was transfected into human fibroblast cells, followed by HCMV infection. Analysis of the steady-state levels of RNA expressed from this hybrid gene indicated that it accumulated with the same kinetics as the authentic viral transcript early in the infection. Cotransfection of human fibroblasts with the 2.7-kilobase RNA promoter-CAT construct and plasmids containing different HCMV immediate-early (IE) genes showed that the region of the HCMV genome encoding the transcription units corresponding to IE1 and 2 and the 5' end of IE3 is capable of stimulating promoter activity but not to the same extent as HCMV infection. To define important cis-acting regulatory elements in the promoter, a series of 5' deletion mutants was constructed. Transient expression analysis showed a stepwise reduction in inducible CAT activity, suggesting the presence of multiple regulatory sites. To further characterize the nature of these sites, we used gel mobility shift assays to study DNA-protein interactions occurring within this promoter sequence. With nuclear extracts prepared from HeLa cells as well as from infected and uninfected human foreskin fibroblasts, we found specific binding of a cellular factor to a region of the promoter important in HCMV inducible activity. This region contains a palindromic octamer with homology to the binding site of the cellular factor USF/MLTF.

Diseases potentially transmitted through corneal transplantation

Transmission of donor disease to the corneal graft recipient appears to be a rare event. Nevertheless, the subject merits careful attention because of the broad spectrum of diseases these cases represent, the potential for transmission of other disorders, and the difficulties in diagnosis they pose. Infections, neoplastic diseases, and corneal disorders may be acquired by corneal transplantation. Very serious are viral infections, but only rabies, Creutzfeldt-Jakob disease, and hepatitis B have had documented transmission. Bacterial and fungal infections are a clear hazard to the graft. On rare occasions, the recipient has died. Although the transmission of local corneal disorders and dystrophies has yet to be documented, the potential seems clear, particularly with tissue from young donors where evidence for dystrophies, such as keratoconus and Fuchs' dystrophy, has yet to appear. Fortunately, in the United States, screening techniques appear to be largely effective in detecting donors who harbor diseases that are potentially transmittable.

Posttranscriptional regulation of a class of human cytomegalovirus phosphoproteins encoded by an early transcription unit

We have further characterized and determined the origins of a family of nuclear phosphoproteins of 84, 50, 43, and 34 kilodaltons (kDa) encoded by a class of early transcripts arising from the adjacent EcoRI fragments R and d (map units 0.682 to 0.713) of the strain AD169 human cytomegalovirus genome. These RNAs have a complex spliced structure with common 5' and internal exons and alternative 3' exons with coterminal 3' ends. At early times, two fully processed species of 2.1 and 2.2 kilobases (kb) predominated. As the infection progressed to late times, there was a decrease in splicing of the RNA, generating larger transcripts 2.5 to 2.65 kb in size, which corresponded to the species which had spliced out only the first intron, as well as the completely unspliced transcript. We previously reported that the 34-kDa protein could be derived from a transcript which had failed to splice out the first intron (D. A. Wright, S. I. Staprans, and D. H. Spector, J. Virol. 62:331-340, 1988), but the origin of the other proteins was unclear. cDNA cloning has shown that the 2.1-, 2.2-, and 2.5-kb RNAs encode the 50-, 43-, and 84-kDa proteins, respectively. The shift in the splicing pattern of these RNAs with time revealed a posttranscriptional control mechanism which results in the differential accumulation of individual proteins within this family of nuclear phosphoproteins. Expression of the 84-, 43-, and 34-kDa proteins correlated well with the steady-state concentrations of their respective mRNAs. The 50-kDa protein, however, was not expressed in abundance until late times, despite the presence of the 2.1-kb mRNA in the cytoplasm at early times, suggesting a secondary level of posttranscriptional regulation for this protein. Full expression of the RNAs and proteins was dependent on continuing viral DNA synthesis. Accumulation of the 50-kDa protein was found to be particularly sensitive to the state of viral DNA replication and could not be detected after inhibition of replication. Further analysis of these proteins revealed that each one had a unique pattern of serine phosphorylation. Although there was one common site of phosphorylation, most likely located within the amino-terminal shared region, even this site showed quantitative differences in the level of phosphorylation for each of the proteins. Analysis of the Towne strain and two recent independent clinical isolates of human cytomegalovirus has shown that this family of proteins is highly conserved among human cytomegaloviruses.

The importance of cytomegalovirus in heart-lung transplant recipients

The first 33 heart-lung transplant recipients in our series were studied for evidence of CMV infection. CMV infection was diagnosed by a change in the serologic status, viral culture, or histology of lung tissue. Of 18 patients who were preoperatively negative for CMV antibody, eight received organs from CMV antibody-positive donors. Five developed pneumonitis (fatal in three)l; one survived primary CMV of the GI tract. Those who recovered from CMV pneumonitis received IV ganciclovir with CMV hyperimmune globulin given prophylactically from the time of transplantation. Only three of ten antibody-negative patients receiving organs from antibody-negative donors developed primary CMV, characterized by only fever in two but associated with rejection, and repeated infection was fatal in a third. CMV reactivation/reinfection occurred in seven of 15 (47 percent) without clinical disease in all but one case. Following heart-lung transplantation, CMV is the cause of considerable mortality and morbidity. We recommend that CMV antibody-negative recipients should receive organs only from antibody-negative donors. If a donor/recipient mismatch occurs, hyperimmune globulin and ganciclovir may improve survival.

Pancreatitis in patients with AIDS presumptively due to CMV

We have studied two patients who developed pancreatitis and who died of complications of acquired immune deficiency syndrome (AIDS). From clinical analysis, presumptively, both patients developed CMV pancreatitis as a complication of AIDS.

Identification of sequence requirements and trans-acting functions necessary for regulated expression of a human cytomegalovirus early gene

We analyzed the regulation of expression of a human cytomegalovirus (HCMV) early transcription unit encoded by EcoRI fragments R and d (map units, 0.682 to 0.713), located within the long unique segment of the genome. This region specified a 2.2-kilobase class of spliced transcripts which encode several related proteins. To define important upstream regulatory elements of this gene, we generated hybrid plasmids in which 5'-promoter sequences were fused to the Escherichia coli chloramphenicol acetyltransferase (CAT) gene and tested these hybrid genes in transient expression assays in human fibroblast cells. The stimulation of CAT activity in HCMV-infected cells was found to reflect an induction of correctly initiated hybrid mRNA, which was dependent on the de novo synthesis of some virally induced factor(s). A time course experiment showed the correct early kinetics of CAT expression. Analysis of a series of 5'-promoter deletion plasmids, ending between -323 and -7 base pairs relative to the transcription start site, showed a stepwise reduction in inducible CAT activity, suggesting that this HCMV early promoter consists of multiple elements. One of these elements resembles the binding site of a previously identified cellular "transcription" factor. We also examined the role of specific virus-encoded factors in the transactivation of this promoter. Cotransfection of human fibroblasts with the 2.2-kilobase RNA promoter-CAT construct and plasmids containing different immediate-early genes showed that expression of CAT from this promoter was stimulated by the region of the HCMV genome encoding the immediate-early 1 and 2 gene products.

The risk of cytomegalovirus transmission by penetrating keratoplasty

To investigate the risk of cytomegalovirus transmission by corneal transplantation, we quantitated anticytomegalovirus IgG levels of donor, preoperative, and postoperative serum samples. Of 118 patients, 79 (67%) were seropositive preoperatively. Twenty-five patients who were seronegative preoperatively received a graft from a positive donor and two (8%) seroconverted. Eleven patients who were seronegative preoperatively received a graft from a negative donor and one (9%) seroconverted. None of the patients who seroconverted had a febrile illness and all three grafts were clear.

Pathogenesis of murine cytomegalovirus infection: identification of infected cells in the spleen during acute and latent infections

Spleen cells which replicate murine cytomegalovirus (MCMV) during acute infection in vivo were identified by electron microscopy and combined immunocytochemical staining and in situ cytohybridization. Most infected cells, as defined by in situ hybridization for viral RNA with MCMV-specific probes, were shown to be positive for factor VIII-related antigen and negative for Ia, Thy-1, and F4/80 antigens. Electron microscopic ultrastructural observations indicated that the infected cells in the spleen are predominantly sinusoidal-lining cells. We also studied reactivation of MCMV from latently infected mice by cocultivation of spleen cells with mouse embryo fibroblasts. Virus was only recovered from cells in preparations of stromal (or reticular) fragments, and not from spleen cell suspensions. Neither removal of immunoglobulin-bearing cells from the stromal fragments by panning nor depletion of Thy-1- and Ia-bearing stromal cells by treatment with monoclonal antibodies and complement reduced the frequency of reactivation of MCMV. These data suggest that T lymphocytes, mature B lymphocytes, and other Ia-bearing cells are not predominant reservoirs of latent MCMV.

Four phosphoproteins with common amino termini are encoded by human cytomegalovirus AD169

In this report, we identify the proteins encoded by the 2.2-kilobase class of early transcripts arising from a region of the strain AD169 human cytomegalovirus genome (map units 0.682 to 0.713) which contains cell-related sequences. These transcripts, encoded by adjacent EcoRI fragments R and d, have a complex spliced structure with 5' and 3' coterminal ends. Antiserum directed against a synthetic 11-amino-acid peptide corresponding to the predicted amino terminus of the proteins was generated and found to immunoprecipitate four infected-cell proteins of 84, 50, 43, and 34 kilodaltons. These proteins were phosphorylated and were associated predominantly with the nuclei of infected cells. The 43-kilodalton protein was the most abundant of the four proteins, and its level of expression remained relatively constant throughout the infection. Expression of the other proteins increased as the infection progressed. Pulse-chase analysis failed to show a precursor-product relationship between any of the proteins. A comparison of the [35S]methionine-labeled tryptic peptide maps of the four proteins from infected cells and an in vitro-generated polypeptide derived from the putative first exon showed that all four infected-cell proteins were of viral origin and contained a common amino-terminal region.