Molecular biology and immunology of cytomegalovirus

Early detection, reactivation of cytomegalovirus DNA & immediate early (IE)-mRNA expression in hematopoietic stem cell-transplant patients

BACKGROUND

Human cytomegalovirus (HCMV) reactivation is a major cause of morbidity and mortality among stem cell transplant recipients post-transplantation.

AIM

HCMV immediate-early messenger RNA (IE-mRNA) was evaluated as marker of post-transplant HCMV reactivation in bone marrow transplant recipients.

METHOD

ology: An in-house real-time reverse transcriptase PCR targeting IE-mRNA was developed to estimate HCMV mRNA levels post-transplantation. Blood samples collected in K2-EDTA tubes from patients (n = 162) admitted with Department of Clinical Hematology were transported in cold condition for routine HCMV DNA screening. For HCMV IE-mRNA quantification, peripheral blood mononuclear cells (PBMCs) were separated from whole blood and stored in RNA later at -70 °C until testing. Samples were collected weekly once for first 3 weeks post-transplantation and thereafter from week 4-12, samples were collected twice weekly. A total of 2467 samples were collected from 162 study participants.

RESULTS

Thirty five patients (21.6 %) had post-transplant HCMV reactivation. Twenty five patients with complete follow-up were selected for monitoring HCMV DNA. HCMV IE-mRNA PCR was performed for 15 patients and 7(46.6 %) patients had detectable mRNA levels. HCMV IE-mRNA was detected in all patients with increasing HCMV DNA levels except for one patient in whom IE-mRNA appeared 3 days before HCMV DNA was detected. One patient had detectable HCMV IE-mRNA during declining HCMV DNA level. However the patient showed an increased HCMV DNA one week later, indicating the importance of HCMV mRNA in predicting HCMV replication.

CONCLUSION

Quantification of HCMV IE-mRNA may be a valuable tool to predict progression of HCMV infection post-transplantation, with further prospective studies needed for validation.

Insight for Immunotherapy of HCMV Infection

Human cytomegalovirus (HCMV), a ubiquitous in humans, has a high prevalence rate. Young people are susceptible to HCMV infection in developing countries, while older individuals are more susceptible in developed countries. Most patients have no obvious symptoms from the primary infection. Studies have indicated that the virus has gradually adapted to the host immune system. Therefore, the control of HCMV infection requires strong immune modulation. With the recent advances in immunotherapy, its application to HCMV infections is receiving increasing attention. Here, we discuss the immune response to HCMV infection, the immune escape mechanism, and the different roles that HCMV plays in various types of immunotherapy, including vaccines, adoptive cell therapy, checkpoint blockade therapy, and targeted antibodies.

Cytomegalovirus Humoral Response Against Epithelial Cell Entry-Mediated Infection in the Primary Infection Setting After Hematopoietic Cell Transplantation

BACKGROUND

The influence of humoral immunity on the prevention of primary cytomegalovirus (CMV) infection after hematopoietic cell transplantation (HCT) is poorly understood.

METHODS

To determine whether neutralizing antibodies (nAbs) against CMV pentameric complex (PC)-mediated epithelial cell entry decrease CMV infection after HCT, samples were analyzed from a randomized controlled trial of CMV intravenous immunoglobulin (IVIG) prophylaxis. Weekly serum from 61 CMV donor-positive/recipient-negative (D+/R-) HCT patients (33 control, 28 CMV IVIG) was tested using a PC-entry nAb assay and quantitative CMV polymerase chain reaction (PCR).

RESULTS

There was a trend toward higher weekly PC-entry nAb titers (P = .07) and decreased CMV infection by PCR at viral load cutoffs of ≥1000 and ≥10 000 IU/mL in the CMV IVIG arm. High nAb titers were not significantly protective against CMV infection later after HCT in both study arms. Among CMV-infected patients, each log2 increase in nAb titer was associated with an average 0.2 log10 decrease in concurrent CMV viral load after infection (P = .001; adjusted for study arm).

CONCLUSIONS

This study provides initial support that CMV IVIG prophylaxis moderately enhances PC-entry nAB activity in D+/R- HCT recipients.

Molecular Biology and Epidemiology of Neurotropic Viruses

Neurotropic viruses are those viruses that can cause central nervous system (CNS) diseases with both neuroinvasive and neurovirulence properties. It comprises a wide range of viruses, including herpes simplex virus, poliovirus, enteroviruses, parechovirus, West Nile virus, Japanese encephalitis virus, measles, and mumps viruses among others. Some of these viruses are highly neuroinvasive and neurovirulent, while others are weakly neuroinvasive and neurovirulent. Moreover, some of them, like herpes simplex viruses, are highly neuroinvasive but weakly neurovirulent for the peripheral nervous system and highly neurovirulent but weakly neuroinvasive for the central nervous system. All these disparities are a result of differences in their genomic constitution, associated vectors, geographical region, and environmental factors. Therefore, a successful intervention will be almost impossible without a clear understanding of the molecular biology and epidemiology of these viruses. Thus, we conducted a review of the published studies on the molecular biology and epidemiology of the common neurotropic viruses to make the viral genetic makeup more understandable for targeted intervention and provide the morbidity and mortality data of the different neurotropic viruses for more serious action.

Antiviral Agents as Therapeutic Strategies Against Cytomegalovirus Infections

Cytomegalovirus (CMV) is a threat to human health in the world, particularly for immunologically weak patients. CMV may cause opportunistic infections, congenital infections and central nervous system infections. CMV infections are difficult to treat due to their specific life cycles, mutation, and latency characteristic. Despite recent advances, current drugs used for treating active CMV infections are limited in their efficacy, and the eradication of latent infections is impossible. Current antiviral agents which target the UL54 DNA polymerase are restricted because of nephrotoxicity and viral resistance. CMV also cannot be prevented or eliminated with a vaccine. Fortunately, letermovir which targets the human CMV (HCMV) terminase complex has been recently approved to treat CMV infections in humans. The growing point is developing antiviral agents against both lytically and latently infected cells. The nucleic acid-based therapeutic approaches including the external guide sequences (EGSs)-RNase, the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) system and transcription activator-like effector nucleases (TALENs) are being explored to remove acute and/or latent CMV infections. HCMV vaccine is being developed for prophylaxis. Additionally, adoptive T cell therapy (ACT) has been experimentally used to combate drug-resistant and recurrent CMV in patients after cell and/or organ transplantation. Developing antiviral agents is promising in this area to obtain fruitful outcomes and to have a great impact on humans for the therapy of CMV infections.

Effects of cytomegalovirus infection in human neural precursor cells depend on their differentiation state

Cytomegalovirus (CMV) is the most common cause of congenital infection in developed countries and a major cause of neurological disability in children. Although CMV can affect multiple organs, the most important sequelae of intrauterine infection are related to lesions of the central nervous system. However, little is known about the pathogenesis and the cellular events responsible for neuronal damage in infants with congenital infection. Some studies have demonstrated that neural precursor cells (NPCs) show the greatest susceptibility to CMV infection in the developing brain. We sought to establish an in vitro model of CMV infection of the developing brain in order to analyze the cellular events associated with invasion by this virus. To this end, we employed two cell lines as a permanent source of NPC, avoiding the continuous use of human fetal tissue, the human SK-N-MC neuroblastoma cell line, and an immortalized cell line of human fetal neural origin, hNS-1. We also investigated the effect of the differentiation stage in relation to the susceptibility of these cell lines by comparing the neuroblastoma cell line with the multipotent cell line hNS-1. We found that the effects of the virus were more severe in the neuroblastoma cell line. Additionally, we induced hNS-1 to differentiate and evaluated the effect of CMV in these differentiated cells. Like SK-N-MC cells, hNS-1-differentiated cells were also susceptible to infection. Viability of differentiated hNS-1 cells decreased after CMV infection in contrast to undifferentiated cells. In addition, differentiated hNS-1 cells showed an extensive cytopathic effect whereas the effect was scarce in undifferentiated cells. We describe some of the effects of CMV in neural stem cells, and our observations suggest that the degree of differentiation is important in the acquisition of susceptibility.

Cytomegalovirus in human breast milk: risk to the premature infant

Human cytomegalovirus (HCMV) can be transmitted through breast milk to neonates. Although healthy full-term infants rarely develop symptoms of CMV infection; premature or low-birth-weight infants can experience symptomatic infection that is occasionally severe. There is limited information on the long-term effects of postnatal CMV infection in premature infants, suggesting that these infants do not develop cognitive function delays or hearing loss, although those with intrapartum infection do. Readily available methods of treating breast milk to inactivate the CMV either diminish the immunologic and nutritive benefits of breast milk or incompletely inactivate the virus. This review considers the data on measuring CMV in breast milk, the recent clinical studies on CMV transmission via breast milk, reported methods of inactivation of CMV in breast milk, and immunologic factors that may play a role in transmission. CMV-IVIG treatment needs further evaluation but appears promising. Recommendations are made to help address the issue of CMV transmission to premature infants in clinical practice in the neonatal intensive care unit (NICU).

Cross-talk between dendritic cells and natural killer cells in viral infection

Dendritic cells (DC), first characterized in 1973 by Steinman and Cohn, have been defined as the professional antigen presenting cells (APC), capable of activating naïve T cells much more efficiently than either B cells or macrophages. DC also capture and process antigen more efficiently than other APC, and offer MHC-antigen complexes to T cells at higher densities, and in the context of larger amounts of co-stimulatory molecules (i.e. CD40, CD80 and CD86) at the T cell-DC synapse. Although historically, the principal function of DC is the priming of naïve T cells, more recently they have also been shown to affect the functions of natural killer (NK) cells. Interactions between DC and NK cells may be critical in situations where immune surveillance requires efficient early activation of NK cells, as is the case during infections. This review aims to summarise the interactions that occur between DC and NK cells during viral infection.

Neuropathogenesis in cytomegalovirus infection: indication of the mechanisms using mouse models

Cytomegalovirus (CMV) is the most frequent infectious cause of developmental brain disorders and also causes brain damage in immunocompromised individuals. Although the brain is one of the main targets of CMV infection, little is known about the neuropathogenesis of the brain disorders caused by CMV in humans because of the limitations in studying human subjects. Murine CMV (MCMV) is similar to human CMV (HCMV) in terms of genome structure, pattern of gene expressions, cell tropism and infectious dynamics. In mouse models, it has been shown that neural stem/progenitor cells are the most susceptible to CMV infection in developing brains. During brain development, lytic infection tends to occur in immature glial cells, presumably causing structural disorders of the brain. In the prolonged phase of infection, CMV preferentially infects neuronal cells. Infection of neurons may tend to become persistent by evasion of immune reactions, anti-apoptotic effects and neuron-specific activation of the e1-promoter, presumably causing functional neuronal disorders. It has also been shown that CMV infection in developing brains may become latent in neural immature cells. Brain disorders may occur long after infection by reactivation of the latent infection.

Perinatal cytomegalovirus hepatitis: to treat or not to treat with ganciclovir

OBJECTIVE

The use on ganciclovir for perinatal cytomegalovirus (CMV) infection is controversial. We aim to evaluate the use of ganciclovir treatment for neonatal CMV hepatitis.

METHODS

We present five infants with perinatally-acquired CMV hepatitis as a single organ manifestation of CMV infection. The three more severely affected children, i.e. those with cholestasis and elevation of serum hepatic enzymes to more than twice the normal values, were treated for 15 days with intravenous ganciclovir.

RESULTS

The three treated infants improved clinically and CMV DNA in the blood disappeared during treatment. After cessation of ganciclovir treatment all of the patients had a relapse of the infection. The two untreated patients recovered completely.

CONCLUSION

The long-term outcome of infants with CMV hepatitis is unpredictable. Some patients have persistent liver injury despite ganciclovir therapy. Ganciclovir therapy did not prevent chronic liver disease in any of the patients in our study. Owing to the possible serious side-effects the cost-benefit of ganciclovir treatment should be carefully evaluated.

Brain slice culture for analysis of developmental brain disorders with special reference to congenital cytomegalovirus infection

Cytomegalovirus (CMV) is the most significant infectious cause of congenital abnormalities of the central nervous system (CNS) with variation from the fatal cytomegalic inclusion disease to functional brain disorder. The phenotype and degree of the brain disorder depends on infection time during the developing stage, virulence, route of infection and the viral susceptibility of the cells. The pathogenesis of the CMV infection to the CNS seems to be strongly related to neural migration, neural death, cellular compositions and the immune system of the brain. To understand the complex mechanism of this disorder, we used organotypic brain slice cultures. In the brain slice culture system, migration of CMV-infected neuronal cells was observed, which reflects infectious dynamics in vivo. Neural progenitor cells or glial immature cells in the subventricular zone and marginal area are most susceptible to murine cytomegalovirus (MCMV) infection in this system. The susceptibility declined as the number of immature glial cells decreased with age. The immature glial cells proliferated in brain slice cultures during prolonged incubation, and the susceptibility to MCMV infection also increased in association with the proliferation of these cells. The brain slice from an immunocompromised mouse (Beige-SCID mouse) unexpectedly showed lower susceptibility than that of an immunocompetent mouse during any prolonged incubation. These results suggest that the number of immature glial cells might determine the susceptibility of CMV infection to the brain, independent of the immune system. We reviewed recent findings of CMV infection to the brain from the perspective of brain slice cultures and the possibility that this system could be a useful method to investigate mechanisms of congenital anomaly of the brain.

Stress management and psychoneuroimmunology in HIV infection

Does stress management affect psychological and immune functioning in persons with human immunodeficiency virus infections? Stress-management techniques, such as relaxation training and imagery, cognitive restructuring, coping-skills training, and interpersonal-skills training, may reduce anxiety, depression, and social isolation in HIV-infected persons by lowering physical tension and increasing a sense of control and self-efficacy. A psychoneuroimmunologic model is proposed wherein these psychological changes are hypothesized to be accompanied by an improved ability to regulate neuroendocrine functioning, which in turn may be associated with a partial normalization of immune system functions such as lymphocyte proliferation and cytotoxicity, providing more efficient surveillance of latent viruses that may contribute directly to increased HIV replication and generate opportunistic infections or cancer if left unchecked. Such a normalization of stress-associated immune system decrements are hypothesized to forestall or minimize increases in viral load and expression of clinical symptoms. This model is useful for testing the factors contributing to the health effects of stress-management interventions in HIV-infected persons. In this context, one general research strategy for testing the effects of stress-management interventions is to target them toward the more prevalent psychosocial challenges that HIV-infected people face at various points in the disease process; enroll an HIV-infected population (eg, HIV-positive homosexual and bisexual men) into a randomized trial; and monitor changes in cognitive, affective, behavioral, and social factors in parallel with hormonal, immunologic, viral, and clinical changes over the course of time. This article will review the major psychoneuroimmunologic findings that have emerged using this paradigm and suggest future research directions and clinical applications.

The amount of immature glial cells in organotypic brain slices determines the susceptibility to murine cytomegalovirus infection

Cytomegalovirus (CMV) is the most common infectious cause of congenital anomalies of the brain and also causes brain damage in immunocompromised individuals. We investigated the effects of murine cytomegalovirus (MCMV) infection on the developing mouse brain in terms of susceptible cells and age-related resistance to MCMV in brain slice cultures. Brain slices from BALB/c mice at different developmental stages were infected with recombinant MCMV in which the lacZ gene was inserted into a late gene. The subventricular zone and cortical marginal region were the sites most susceptible to MCMV infection, and the susceptibility declined with the development of the brain. Immunohistochemical staining showed that the virus-susceptible cells were positive for GFAP, nestin, and Musashi-1, and that most of the infected cells were positive for the proliferative cell nuclear antigen and labeled with bromodeoxyuridine. These results suggest that the susceptible cells in the subventricular zone are immature glial cells, including neural progenitor cells. Immature glial cells proliferated when the brain slices were cultured for a prolonged time and furthermore, they showed themselves to be susceptible to virus infection even under serum-free conditions. These results suggest that the amount of immature glial cells, which include neural progenitor cells, in the developing brain or in the damaged brain with neural proliferation may be closely associated with the susceptibility of the brain to CMV infection in humans.

Targeting the function of mature dendritic cells by human cytomegalovirus: a multilayered viral defense strategy

Human cytomegalovirus (HCMV) can suppress and evade the immune system. We have identified as a mechanism the ability of HCMV to infect dendritic cells (DC), which initiate the antiviral immune response. HCMV-infected DC show enhanced expression of costimulatory molecules. In contrast, MHC molecules are partially downregulated, leading to a reduced antigen-presenting capacity. Moreover, the apoptosis-inducing ligands CD95L (FasL) and tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) are upregulated, thereby enabling HCMV-infected DC to delete activated T lymphocytes. This additional layer of viral defense is complemented by nondeletional mechanisms, which suppress surviving T cells. Thus, infection of DC allows the virus to blunt the antiviral T cell response by a multilayered defense strategy and could play a pivotal role in HCMV-triggered immunosuppression.

Activation of murine cytomegalovirus immediate-early promoter in cerebral ventricular zone and glial progenitor cells in transgenic mice

Cytomegalovirus (CMV) is the most common infectious cause of congenital anomalies of the CNS in humans. We recently reported that the murine cytomegalovirus (MCMV) immediate-early (IE) gene promoter directs astrocyte-specific expression in adult transgenic mice. In the present study, we analyzed the activation of the MCMV IE promoter in developing transgenic mouse brains and compared the activation with that of the Musashi 1 (Msi1) gene, which is expressed in neural progenitor cells, including neural stem cells. During the early phase of neurogenesis, the transgene was expressed predominantly in endothelial cells of the vessels, but not in neuroepithelial cells in which Msi1 was expressed. During later stages of gestation, expression of the transgene was largely restricted to the ventricular zone (VZ) in the CNS, similar to the expression of Msi1. In neurosphere cultures from transgenic embryos in the late phase of neurogenesis, the transgene was expressed in some cells of neurospheres expressing Msi1 and nestin. In neural precursor cells induced to differentiate from stem cells, expression of the transgene was detected in glial progenitor cells, expressing GFAP, nestin, and Msi1, but not in cells expressing MAP2 or MAG. In postnatal development, persistent expression of the transgene was observed in astrocyte lineage cells as was Msi1. These spatiotemporal changes of the MCMV IE promoter activity during development of transgenic mice correlated with susceptible sites in congenital HCMV infection. Moreover, this transgenic mouse model may provide useful model for analysis of the regulation of the switching of neuronal and astrocyte differentiation, and the maintenance of the astrocyte lineage.

Detection of cytomegalovirus (CMV) antigens in kidney biopsies and transplant nephrectomies as a marker for renal graft dysfunction

Chronic rejection accounts for the greatest loss of renal allografts. HLA mismatching has been minimised by organ allocation and new immunosuppressive drugs have been employed, but the average cadaveric graft survival still does not exceed 12 years. Though the aetiology is multifactorial, one contributory factor for this condition is cytomegalovirus (CMV). Detection of CMV in kidney biopsies and sera can diagnose and monitor this inflammatory event and define its role in chronic nephropathy. Twenty five biopsies taken at the time of transplantation, 10 biopsies for graft dysfunction and tissue blocks from 20 explanted kidney grafts were collected and investigated for CMV antigens by immunohistochemistry. Tissue samples were snap frozen and cryostat sections were incubated with monoclonal antibodies for CMV antigens followed by immunoperoxidase staining. In 12 out of 20 transplant nephrectomies CMV antigens were found. Only two of these patients had clinical CMV disease. Time 0 biopsies from CMV seronegative donors (n = 11) and CMV seropositive donors (n = 14) were negative for CMV antigens. The prevalence of CMV antigens in grafts lost due to chronic rejection was 60%. These antigens were not found within the time 0 biopsies, but were detected in 30% of biopsies taken at the time of clinical graft dysfunction. CMV appears to contribute to chronic rejection even without clinical disease.

Reactivation of human herpesviruses after allogeneic peripheral blood stem cell transplantation and bone marrow transplantation

Reactivation of latent herpesviruses results in outcomes ranging from asymptomatic shedding of viruses to severe diseases, depending on the immunological competence of the host. Severe and prolonged suppression of cellular and humoral immunity after hematopoietic stem cell transplantation is accompanied by a high incidence of symptomatic recurrent herpesvirus infections. Subclinical reactivation also occurs more frequently than previously expected in transplant recipients. An increasing viral load in the blood detected by an antigenemia assay or PCR and viral shedding in regional fluids have a predictive value for subsequent diseases. Monitoring of viral DNA in the peripheral blood after allogeneic bone marrow transplantation (allo-BMT) reveals unique temporal profiles of detection for each herpesvirus. Recent studies demonstrate that recovery of CD4+ T cells is enhanced within one month after allogeneic peripheral blood stem cell transplantation (allo-PBSCT) compared to allo-BMT. To clarify whether this immunological advantage could affect the reactivation of human herpesvirus (HHV), we monitored the emergence of viral DNA by a nested-double polymerase chain reaction in peripheral blood leukocytes. Detection rates of HHV-6 DNAs which peak at 3-4 weeks post-transplant, were significantly reduced after allo-PBSCT compared to allo-BMT, while those of other herpesviruses which tend to be reactivated later than this period (Epstein-Barr virus and cytomegalovirus) were similar between the two types of transplants. Detection of HHV-6 DNA within the first month after the transplant was associated with delayed platelet engraftment. These results underscore the important role of CD4+ T reconstitution in inhibiting virus reactivation post-transplant.

Simultaneous Ex Vivo Expansion of Cytomegalovirus and Epstein-Barr Virus–Specific Cytotoxic T Lymphocytes Using B-Lymphoblastoid Cell Lines Expressing Cytomegalovirus pp65

Cytomegalovirus (CMV) infection and Epstein-Barr virus (EBV)-induced lymphoproliferative disease are serious complications associated with allogeneic stem cell transplantation. Immunotherapy using ex vivo expanded, virus-specific cytotoxic T lymphocytes (CTL) has been explored and proven to be effective in therapeutic or prophylactic regimens for CMV and EBV infections. To generate CTL specific for both CMV and EBV, we engineered EBV-transformed B-lymphoblastoid cell lines (BLCL) to express CMV pp65 for use as antigen-presenting cells (APC). BLCL were transduced with a recombinant retrovirus encoding pp65, the immunodominant CMV polypeptide. Western blot analysis and immunocytochemistry confirmed the expression of pp65 in the transduced cells. Peripheral blood mononuclear cells (PBMC) from healthy CMV seropositive donors were stimulated with autologous pp65-expressing BLCL weekly for 3 weeks. Chromium release assays showed that the resulting CTL cultures possessed specific cytotoxicity against EBV and CMV. Recombinant vaccinia viruses encoding individual CMV peptides were used to demonstrate that this CMV-specific cytotoxicity was specific for pp65. Assays on CD4- and CD8-depleted CTL fractions indicated that CD8+ CTL mediated the pp65-specific cytotoxicity. These CMV/EBV-specific CTL recognized CMV- and EBV-infected targets sharing HLA class I antigens, but not HLA mismatched targets. Our results demonstrate that BLCL can be used as APC to stimulate expansion of EBV- and CMV-specific CTL simultaneously. These findings have potential implications for posttransplant CMV and EBV immunotherapy in recipients of allogeneic stem cell transplants.

Simultaneous Ex Vivo Expansion of Cytomegalovirus and Epstein-Barr Virus–Specific Cytotoxic T Lymphocytes Using B-Lymphoblastoid Cell Lines Expressing Cytomegalovirus pp65

Cytomegalovirus (CMV) infection and Epstein-Barr virus (EBV)-induced lymphoproliferative disease are serious complications associated with allogeneic stem cell transplantation. Immunotherapy using ex vivo expanded, virus-specific cytotoxic T lymphocytes (CTL) has been explored and proven to be effective in therapeutic or prophylactic regimens for CMV and EBV infections. To generate CTL specific for both CMV and EBV, we engineered EBV-transformed B-lymphoblastoid cell lines (BLCL) to express CMV pp65 for use as antigen-presenting cells (APC). BLCL were transduced with a recombinant retrovirus encoding pp65, the immunodominant CMV polypeptide. Western blot analysis and immunocytochemistry confirmed the expression of pp65 in the transduced cells. Peripheral blood mononuclear cells (PBMC) from healthy CMV seropositive donors were stimulated with autologous pp65-expressing BLCL weekly for 3 weeks. Chromium release assays showed that the resulting CTL cultures possessed specific cytotoxicity against EBV and CMV. Recombinant vaccinia viruses encoding individual CMV peptides were used to demonstrate that this CMV-specific cytotoxicity was specific for pp65. Assays on CD4- and CD8-depleted CTL fractions indicated that CD8+ CTL mediated the pp65-specific cytotoxicity. These CMV/EBV-specific CTL recognized CMV- and EBV-infected targets sharing HLA class I antigens, but not HLA mismatched targets. Our results demonstrate that BLCL can be used as APC to stimulate expansion of EBV- and CMV-specific CTL simultaneously. These findings have potential implications for posttransplant CMV and EBV immunotherapy in recipients of allogeneic stem cell transplants.

Cytomegalovirus colitis in individuals without apparent cause of immunodeficiency

Cytomegalovirus infection is usually reported in immunocompromised patients. In this study, apparently immunocompetent patients with cytomegaloviral colitis were reviewed. Records with a diagnosis of cytomegaloviral colitis from January 1989 to June 1996 were retrieved for analysis. Ten patients were included (median age 70 yr). The major presenting symptoms were diarrhea and hematochezia. Ulceration was the main macroscopic finding. Rectal bleeding was mostly self-limiting. Three patients developed local complications (rectovaginal fistula in two; rectal stricture in one). In the two patients with rectovaginal fistula, lymphocytes subsets and proliferative response were entirely normal. In the other patient, low B lymphocyte count and low response to mitogen were demonstrated. However, the immunoglobulins were not suppressed and rectal biopsies revealed noncaseating granulomas, suggesting activated cell-mediated immunity. In conclusion, a high index of suspicion is crucial for early diagnosis of cytomegaloviral colitis in patients with bloody diarrhea, even though obvious evidence of immunodeficiency is lacking.

The role of IL-12 in the control of MCMV is fundamentally different in mice with a retroviral immunodeficiency syndrome (MAIDS)

The present study investigates the susceptibility of C57BL mice exhibiting T cell immunodeficiency and lymphadenopathy induced by LP-BM5 murine leukaemia virus (MAIDS) to murine cytomegalovirus (MCMV). Treatment of normal (M-) mice with anti-IL-12 increased the contribution of IgG1 to the hypergammaglobulinaemia induced by MCMV, consistent with a shift towards a Th2 phenotype. This impaired control of early MCMV replication in the liver, with little effect in the spleen. Control of hepatic infection correlated with a vigorous splenic NK cytotoxic response in a subgroup of IL-12-depleted M- mice that remained healthy, while others became moribund. Mortality in IL-12-depleted MAIDS (M+) mice given MCMV was ultimately greater than in M- controls, but was delayed despite high levels of MCMV in the liver. IL-12 was required for optimal control of MCMV replication in M+ mice. This may involve cytotoxic activity because similar levels of infection were seen in bg/bg M+ mice, where the beige mutation impairs the formation of cytotoxic granules. Hence the ability of M+ mice to tolerate high titres of MCMV during acute infection may enable innate cytotoxic responses to clear MCMV. Interleukin-12 depletion of M- mice also increased salivary gland MCMV titres and depressed delayed-type hypersensitivity responses to MCMV antigen, normally mediated by CD4+ T cells. These changes were not observed in IL-12-depleted M+ mice.

Resistance to human cytomegalovirus infection may be influenced by genetic polymorphisms of the tumour necrosis factor-alpha and interleukin-1 receptor antagonist genes

To examine whether there are genetic differences between cytomegalovirus (CMV)-seronegative and CMV-seropositive adults, the polymorphisms of cytokine genes were analysed in a cohort of 400 adult blood donors. The genes and polymorphic sites studied were the tumour necrosis factor-alpha (TNF-alpha) gene (base exchange polymorphism at position -308; alleles TNF1 and TNF2) and the interleukin-1 receptor antagonist (IL-1RA) gene (variable numbers of 86-bp repeats in intron 2). In this material there were 85 (21%) seronegative persons. The frequencies of the TNF2 and the IL-IRA allele 2 (IL1RN*2) carriers were slightly increased in the seronegative compared with the seropositive samples (39% vs. 29%, and 55% vs. 47%, respectively). The presence of both of these alleles together was significantly (p < 0.05, chi2-test) more frequent in the seronegative population. These data suggest that the alleles of these cytokines, which are known to be associated with a strong inflammatory reaction, may have a protective role against CMV infection.

Murine cytomegalovirus immediate-early promoter directs astrocyte-specific expression in transgenic mice

Murine cytomegalovirus (MCMV), which causes acute, latent, and persistent infection of the natural host, is used as an animal model of human cytomegalovirus (HCMV) infection. Transcription of MCMV immediate-early (IE) genes is required for expression of the early and late genes and is dependent on host cell transcription factors. Cell-type-specific expression activity of the MCMV IE promoter was analyzed in transgenic mice generated with the major IE (MIE) enhancer/promoter involving nucleotides -1343 to -6 (1338 bp) connected to the reporter gene lacZ. Distinct expression was observed in the brain, kidneys, stomach, and skeletal muscles. Weak expression was observed in a portion of the parenchymal cells of the salivary glands and pancreas, and expression was hardly detected in the lungs, intestine, or immune and hematopoietic organs such as the thymus, spleen, lymph nodes, and bone marrow. The spectrum of organs positive for expression was narrower than that of the HCMV MIE promoter-lacZ transgenic mice reported previously and showed a greater degree of cell-type specificity. Interestingly, astrocyte-specific expression of the transgene was observed in the brain and primary glial cultures from the transgenic mice by combination of beta-galactosidase (beta-Gal) expression and immunostaining for cell markers. However, the transgene was not expressed in neurons, oligodendroglia, microglia, or endothelial cells. Furthermore, the beta-Gal expression in glial cultures was stimulated significantly by MCMV infection or by addition of calcium ionophore. These observations indicated that expression activity of the MCMV IE promoter is strictly cell-type specific, especially astrocyte-specific in the brain. This specific pattern of activity is similar to that of natural HCMV infection in humans.

Clinical significance of CMV-specific T helper responses in lung transplant recipients

BACKGROUND

Cytomegalovirus (CMV) disease continues to be a major problem for lung transplant patients who generate an inefficient immune response to control this viral infection. Both T helper and cytotoxic T cells are thought to play an important role in prevention and control of CMV disease. We investigated the clinical significance of CMV-specific memory responses in lung transplant recipients.

METHOD

Peripheral blood samples (140) were collected from 99 lung transplant recipients. Patients were grouped according to their pre-transplant CMV serological status as recipient/donor (R-/D+, 25 patients), 28 R+/D+ patients, 35 R+/D- patients and 11 R-/D- patients. Memory responses to CMV whole antigen, 5 CMV proteins, and tetanus toxoid (TT) were measured in a 6-day proliferative assay. Results were expressed as the stimulation index (SI = experimental cpm/background cpm), and were considered positive if the SI was >3 and the cpm values were over 1,000.

RESULTS

The frequency of positive CMV memory responses was similar in three groups: 64% for R-/D+, 63% for R+/D+ and 56% for R+/D- except for R-/D- (21%). The memory response to TT was similar for all four groups (70% of samples were positive). The level of responsiveness to individual CMV proteins was much higher in R+/D+ group (65%) than the other two groups (35% for R+/D-, and 31% for R-/D+). We determined the temporal relationship between the presence of CMV-specific memory responses and the diagnosis of CMV disease. In the R-/D+ group, 16 of 17 patients who had CMV disease eventually developed CMV-specific memory. In those patients (n = 3) who failed to develop CMV-specific T helper response for a prolonged time, all had recurrent CMV disease. In the R+/D+ group, 4 of 8 patients with CMV disease exhibited CMV-specific memory responses. Three of 4 patients in whom we observed a persistent absence of CMV-specific memory had multiple episodes of CMV pneumonitis. In the R+/D- group, only one of 4 patients with CMV disease had suppressed CMV-specific memory response after first episode of CMV pneumonitis and had recurrent disease.

CONCLUSION

In lung transplant recipients, the loss or persistent lack of CMV-specific memory following infection was associated with chronic CMV disease. These data suggest that monitoring T helper memory responses following primary CMV infection or after augmented immunosuppression for treatment of rejection may identify those patients at risk for morbidity associated with recurrent CMV disease.

Differential expression of the immediate-early and early antigens in neuronal and glial cells of developing mouse brains infected with murine cytomegalovirus

Brain disorders induced by congenital cytomegalovirus (CMV) infection may appear at a later time after birth as a consequence of persistent infection and/or the activation of a latent infection of the neural cells. We have analyzed the infection dynamics of the neural cells in the neonatal mouse brains infected with murine CMV (MCMV) in the late stage of gestation. First we prepared a rat monoclonal antibody to the major immediate-early (IE)-89K antigen and then used the antibody for comparison of the expression of early and late viral genes in the developing mouse brains. The cells expressing the IE-89K antigen were mostly localized in the ventricular and subventricular zones and were preferentially double stained with anti-glial fibrillary acidic protein and anti-nestin antibodies. In contrast, the cells expressing the early nuclear antigen, detected by the monoclonal antibody D5, were diffusely distributed in the cortex and the hippocampus and were mostly double labeled with anti-neuron-specific enolase antibody. In neonatal mouse brains infected congenitally with recombinant MCMV, which expressed lacZ as a late gene, the number of the early nuclear antigen-positive cells was much higher than that of the beta-galactosidase-expressing cells, the number of which was almost the same as that of the IE-89K antigen-positive cells. In addition, the distribution of viral DNA-rich cells detected by DNA-DNA hybridization was similar to that of the IE-89K antigen-positive cells. These results suggest that CMV may persistently infect neuronal cells, whereas lytic infection may preferentially occur in the glial cells in the developing brain.

Human cytomegalovirus IE2 86-kilodalton protein binds p53 but does not abrogate G1 checkpoint function

Physical interactions between human cytomegalovirus (HCMV) immediate-early (IE) proteins and key cell cycle regulatory proteins have been suggested as a mechanism whereby this herpesvirus modifies cellular control of proliferation. Observed similarities to interactions of other DNA virus proteins (human papillomavirus type 16 E6 and E7, simian virus 40 large T antigen, and adenovirus type 5 E1A and E1B) with cell cycle modulatory proteins such as p53 and Rb have suggested that HCMV IE proteins may likewise alter the G1-to-S phase transition. The IE2 region gene product IE86 has been shown to specifically bind p53, potentially modifying p53 G1 checkpoint function. To examine this possibility, p53-mediated G1 arrest in the presence of IE86 was assessed. Retroviral constructs were created to facilitate the stable expression of IE86 and IE72, another IE protein implicated in HCMV-mediated alteration of cell cycle progression. Western analysis and immunoprecipitation confirmed IE protein expression and binding of IE86 to p53, respectively. Chloramphenicol acetyltransferase assays examining the ability of IE86 to repress activity from the HCMV major IE promoter or activate the HCMV early promoter for the 2.2-kb class of RNAs demonstrated the functional integrity of the IE86 protein. Induction of DNA damage in normal, uninfected fibroblasts (FB) or FB expressing IE86 by actinomycin D (Act D) resulted in increased p53 levels, a predominance of the hypophosphorylated form of Rb, and increased expression of both p21(CIP1/WAF1) and mdm-2. Fluorescence-activated cell sorting revealed that both uninfected and IE86-expressing FB experienced dramatic G1 arrest following exposure to Act D. The clear demonstration of these p53-dependent responses in the presence of IE86 indicates that binding to this viral protein does not compromise the ability of p53 to elicit growth arrest following DNA damage.

The roles of tumour necrosis factor-alpha, interleukin-1 and interleukin-12 in murine cytomegalovirus infection

The roles of the inflammatory cytokines tumour necrosis factor-alpha (TNF-alpha), interleukin-1 (IL-1) and IL-12, in murine cytomegalovirus (MCMV) disease were investigated in susceptible BALB/c and resistant C57BL/6 mice. MCMV infection induced IL-1 and TNF-alpha production by peritoneal cells from BALB/c mice, as demonstrated previously in C57BL/6 mice. Overt ill-health and viral replication in the spleens of BALB/c mice were increased by in vivo treatment with soluble TNF-alpha receptors to inhibit the activity of this cytokine, whilst antibodies to IL-12 had a similar but more restricted effect C57BL/6 mice were not affected by either treatment, suggesting TNF-alpha and IL-12 are not critical for natural killer cell-mediated restriction of viral replication in the spleen. Soluble TNF-alpha receptors and antibodies to IL-12 also enhanced MCMV titres and numbers of viral antigen-positive cells in the livers of BALB/c mice and TNF-alpha receptors have similar effects in C57BL/6 livers. In contrast, IL-1 receptors improved the health of MCMV-infected BALB/c mice and reduced viral replication and hepatitis at some time-points. Mechanisms which may underlie these changes are discussed.

Effect of a retroviral immunodeficiency syndrome on murine cytomegalovirus-induced hepatitis

We have studied the effects of LP-BM5 MuLV-induced murine acquired immunodeficiency syndrome (MAIDS) on concomitant murine cytomegalovirus (MCMV) infection in the livers of C57BL mice. A delayed inflammatory response in livers of mice with MAIDS (M+) on day 4 was associated with impaired clearance of MCMV-infected cells 6 days after infection. This correlated with increased levels of inflammation and serum alanine transaminase. The latter reflects enhanced hepatic necrosis, which was evident histologically. Delayed-type hypersensitivity responses to MCMV antigen were unimpaired in M+ mice and were mediated by CD8+ cells. Depletion of NK1.1+ cells from M+ mice increased MCMV replication and associated liver damage on day 6, whereas CD8+ depletion had little effect. In contrast, in the presence of CD8+ cells M- C57BL mice did not require NK1.1+ cells for control of hepatic MCMV infection, but dual NK1.1+ and CD8+ depletion dramatically potentiated hepatic MCMV replication. Our results suggest that M+ mice may acquire non-NK1.1+ and non-CD8+ cells that are able to partially control hepatic MCMV infection. These findings are discussed with reference to mortality in M+ mice after high-dose MCMV infection, as this is initially delayed but ultimately higher than in M- controls.

Detection of the Human Cytomegalovirus 2.0-kb Immediate Early Gene 1 Transcripts in Permissive and Nonpermissive Infections by RNA in situ Hybridization

The immediate early gene 1 (IE1) is the first gene to be expressed following the entry of the human cytomegalovirus (HCMV) into the cell and it does not require prior protein synthesis for its expression. Therefore, the IE1 gene is a potential candidate for the development of probes to detect HCMV in various states of infection. Using strand-specific (32)P- or digoxigenin-labeled riboprobes derived from an exon-specific subgenomic fragment of the HCMV Towne IE1 gene, we performed Northern blot analysis and RNA in situ hybridization on HCMV-infected human (permissive cells) and mouse (nonpermissive cells) fibroblasts and on 10 formalin-fixed paraffin-embedded sections of human tissue. By Northern blot analysis and by in situ hybridization, expression of the 2.0-kb IE1 gene was found in permissive as well as in nonpermissive infections. Specific nuclear and cytoplasmic hybridization was found at 5, 10, 24 and 72 h after infection in human fibroblasts. In comparison, hybridization was first detected at 10 h after infection in mouse fibroblasts. Hybridization with the IE1 probe was detected in cells with and without cytopathic changes in the formalin-fixed paraffin-embedded HCMV-infected human tissues. Hybridization patterns of the IE1 riboprobe were compared to those of the HCMV 2.7-kb major early beta-riboprobe which we have previously described [Am J Pathol 141:1247-1254;1992]. Although both riboprobes hybridize to their respective target sequences in the consecutive tissue sections, the patterns of hybridization are different. On occasion, sections of HCMV-infected human tissue showing no specific hybridization for the 2.7-kb riboprobe will show specific in situ hybridization when using the IE1 riboprobe. Our results suggest that RNA in situ hybridization with a probe directed at the IE1 transcripts is an effective method of detecting early and late stages of both permissive and nonpermissive HCMV infections. Copyright 1997 S. Karger AG, Basel

Cytotoxic T-lymphocyte responses to cytomegalovirus in normal and simian immunodeficiency virus-infected rhesus macaques

Disseminated cytomegalovirus (CMV) infection is a frequent occurrence in human immunodeficiency virus-infected humans and in simian immunodeficiency virus (SIV)-infected rhesus macaques. Rhesus macaques are a suitable animal model with which to study in vivo interactions between CMV and AIDS-associated retroviruses. Since cytotoxic T lymphocytes (CTL) play a major role in control of viral infections, we have characterized CMV-specific CTL responses in SIV-infected and uninfected rhesus macaques. Autologous fibroblasts infected with rhesus CMV were used to stimulate freshly isolated peripheral blood mononuclear cells from CMV-seropositive animals. Following in vitro stimulation, specific CTL activity against CMV-infected autologous fibroblasts was detected in CMV-seropositive but not in CMV-seronegative normal macaques. CMV-specific CTL activity comparable to that in normal animals was also detected in two CMV-seropositive macaques infected with a live attenuated SIV strain (SIVdelta3) and in two of three macaques infected with pathogenic SIV strains. The CMV-specific CTL response was class I major histocompatibility complex restricted and mediated by CD8+ cells. An early CMV protein(s) was the dominant target recognized by bulk CTL, although the pattern of CTL recognition of CMV proteins varied among animals. Analysis of CMV-specific CTL responses in macaques should serve as a valuable model for CMV immunopathogenesis and will facilitate prospective in vivo studies of immune interactions between CMV and SIV in AIDS.

Evaluation by polymerase chain reaction of cytomegalovirus reactivation in intensive care patients under mechanical ventilation

OBJECTIVE

The study was undertaken to determine if critically ill patients under mechanical ventilation could reactivate latent cytomegalovirus (CMV) in either lung or blood.

DESIGN

Prospective study in critically ill patients was performed in a multidisciplinary intensive care unit in a university hospital.

PATIENTS

23 non-immunocompromised, mechanically ventilated patients who were anti-CMV immunoglobulin G-positive. Ten immunocompromised patients with active CMV infection and 16 asymptomatic CMV seropositive non-immunocompromised patients constituted the positive and negative control groups.

MEASUREMENTS AND RESULTS

The presence of CMV in blood and bronchoalveolar lavage (BAL) was evaluated by both viral cultures and polymerase chain reaction (PCR). Thirty-seven blood and 22 BAL samples were investigated. Sequential samples were evaluated in 8 patients. For PCR, a 290 bp fragment in the first exon of the immediate early 1 gene was amplified. In order to exclude inhibitors of PCR amplification, a 268 bp fragment of the beta-globin gene was concurrently amplified in all samples. Viral cultures of blood and BAL were negative in all 23 non-immunocompromised, mechanically ventilated patients. Moreover, no CMV DNA could be amplified in blood BAL samples, whereas a beta-globin amplification was observed in all samples.

CONCLUSION

In a series of 23 critically ill patients under mechanical ventilation who were seropositive for CMV, no reactivation of CMV in blood or lung was demonstrated.

Association of anti-GM2 antibodies in Guillain-Barré syndrome with acute cytomegalovirus infection

We examined serum anti-cytomegalovirus (CMV) and anti-ganglioside antibodies by ELISA in 51 patients with Guillain-Barré syndrome (GBS), and titers were compared with those from 47 normal and 74 disease controls. Three GBS patients with IgM anti-CMV antibodies had high titers of IgM and IgG anti-GM2 antibodies. The other GBS patients without IgM anti-CMV antibodies, and the normal and disease controls except one of 6 non-GBS patients with acute CMV infections had no anti-GM2 antibodies. The titers of anti-GM2 antibodies decreased on absorption with CMV-infected cells. These findings suggest that anti-GM2 antibodies are associated with acute CMV infections in GBS patients.

The intracellular localization of human cytomegalovirus DNA in peripheral blood leukocytes during active infections by high-resolution fluorescence in situ hybridization

Although viremia is an integral part of the pathogenesis of human cytomegalovirus (HCMV) disease, the interaction between HCMV and circulating leukocytes of actively infected patients remains an area of uncertainty. It is still a matter of dispute, whether leukocytes support viral replication with subsequent production of infectious virus. In a new approach we developed and applied a sensitive fluorescence in situ hybridization assay for the precise intracellular localization of HCMV genomes in leukocytes. It was shown that in vivo HCMV genomes were exclusively localized in the cytoplasm of leukocytes, indicating that the majority of these cells are virus carriers or abortively infected. Though this method easily detects single copy genes in metaphase chromosomes, the number of HCMV DNA positive leukocytes was significantly lower than the number of HCMV pp65 antigen positive cells. In relation to the pp65 antigen positive cells, only 1-4% of these cells were DNA positive. In addition, the much lower frequency of HCMV immediate early antigen positive leukocytes in comparison to the pp65 antigen positive cells and the impossibility of detecting other viral antigens support the hypothesis that the origin of pp65 found in leukocytes results mainly from protein uptake.

Calnexin acts as a molecular chaperone during the folding of glycoprotein B of human cytomegalovirus

Human cytomegalovirus glycoprotein B (gB) is synthesized as a 105-kDa nonglycosylated polypeptide and cotranslationally modified by addition of N-linked oligosaccharides to a 160-kDa precursor in the endoplasmic reticulum (ER). It is then transported to the Golgi complex, where it is endoproteolytically cleaved to form the disulfide-linked mature gp55-116 complex. Pulse-chase experiments demonstrate that the 160-kDa gB precursor was transiently associated with calnexin, a membrane-bound chaperone, in the ER. The association was maximal immediately after synthesis, and they dissociated with a half-time of 15 min. Complete inhibition of binding by tunicamycin or castanospermine indicates the importance of N-linked oligosaccharides for it. Nonreducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis demonstrated that during an initial stage in the biogenesis, the 160-kDa gB precursor was first synthesized as a fully reduced form and rapidly converted to an oxidized form, with a half-time of 18 min. Both forms of the gB precursor could bind to calnexin. The kinetics of the conversion from the fully reduced to the oxidized form coincided with that of dissociation of the 160-kDa gB precursor from calnexin, suggesting that the two steps are closely related.

CMV-DNA detection in parenchymatous organs in cases of SIDS

A nested PCR approach has been developed especially for the detection of small amounts of cytomegalovirus (CMV) DNA in autopsy samples. Lung tissue and submandibular glands in 118 cases of infant death (92 SIDS cases, 13 natural deaths due to other defined causes and 13 unnatural deaths) were investigated by this technique and compared to the results obtained by other CMV detection methods (histology, immunohistochemistry, in situ hybridization and PCR). CMV-DNA could be detected in the lung tissue in 7 cases of SIDS using nested PCR. Compared to conventional PCR (3 positive cases in lung tissue) the nested approach always gave glear results and showed less additional bands. In all cases where CMV could be detected in the lungs, positive results were also obtained in the submandibular glands. The nested PCR method proved to be a more sensitive technique than the other detection methods including PCR and hot start, and even minimal amounts of target DNA could be detected in the presence of human and bacterial background DNA.

Cytomegalovirus replication is not a cause of instability in unstable angina

BACKGROUND

Unstable angina is most frequently caused by coronary thrombosis, with or without plaque fissure, but the mechanisms underlying these events are still speculative. Since cytomegalovirus (CMV) antigens and DNA encoding CMV major immediate-early (MIE) gene have been detected in atherosclerotic arterial walls, the active replication of CMV may be responsible for plaque instability. Therefore the expression of CMV MIE gene mRNA, an early marker of viral replication, was assessed in coronary atherectomy specimens from patients with stable or unstable angina.

METHODS AND RESULTS

Twenty patients with unstable angina (12 men and 8 women; mean age, 62 years; range, 44 to 89 years) and 20 patients with stable angina (16 men and 4 women; mean age, 62 years; range, 43 to 81 years) who underwent successful directional coronary atherectomy were enrolled in the study. The efficiency of mRNA extraction, transcription, and amplification from each coronary atherectomy specimen was assessed by performance of reverse transcription and thermal cycling amplification of a 548-bp human beta-actin cDNA segment. After Southern blotting and hybridization with a specific probe, all specimens but one showed a positive hybridization signal. The negative sample was excluded from the study. Reverse transcription and thermal cycling amplification of a 145-bp CMV cDNA segment of the MIE gene were then carried out. After Southern blotting and hybridization with a specific probe, none of the specimens showed a positive hybridization signal. Plasmid pACYC 184 containing the Xba I-inserted MIE gene cDNA was used as a positive control: as few as 10 molecules of the plasmid per reaction were detectable after amplification.

CONCLUSIONS

Our results do not support the hypothesis that, in patients with unstable angina, replication of CMV in coronary atherosclerotic plaques is a major cause of plaque instability. These findings suggest that the research for the causes of unstable angina should be directed toward processes other than CMV replication.

The presence of cytomegalovirus antigens in karyotyped abortions

PROBLEM

About one out of six pregnancies ends in spontaneous abortion before the 17th week. In more than half of these a chromosome abnormality is present, which explains the abortion. The role of cytomegalovirus (CMV) infections in early pregnancy failure is unclear. If there is a role for CMV, a preponderance of infections would be expected in a chromosomally normal group.

METHOD

The significance of CMV in abortions has been studied by screening 80 spontaneous and nine induced abortions with known karyotype for the presence of phosphoprotein pp65, an early CMV antigen. Also, endometrial biopsies (n = 55) and menstruum (n = 10) were screened. In 11 patients more than one specimen was available for study.

RESULTS

The protein was present in the glandular epithelium of the decidua of spontaneous as well as induced abortions in 31 of 89 (35%) cases, irrespective of chromosomal constitution. Trophoblastic cells were pp65 positive in 6/89 cases. A total of 17 embryos could be studied, seven of which were positive. Positive staining of embryonic organs correlated strongly with the presence of the antigen in the decidua. The endometrial biopsies and menstrual discharges from women of comparable ages showed the same percentages of positive tests for pp65: 35 and 20%. Histologically positive and negative specimens could not be differentiated other than by the specific staining. In 10 of 11 patients with more than one specimen available, the results were consistent. One patient had two positive and one negative specimen.

CONCLUSION

The findings indicate that in early pregnancy cytomegalovirus is transmitted from the decidual glands to the foetus. However, we have not found indications that the presence of cytomegalovirus infection as shown by the presence of antigen is pathogenic for early pregnancy.

Humoral immune responses and cytomegalovirus excretion in children with asymptomatic infection

Forty-two seropositive children aged 3 to 5 years attending a kindergarten were followed up for 1 year in order to examine the relationship between humoral immunity and cytomegalovirus (CMV) excretion status. Anti-CMV antibodies were measured at the beginning and end of the study by enzyme-linked immunosorbent assay, neutralizing antibody test, and immunoblot techniques. Among these children, 32 persistently shed virus in urine, 2 intermittently shed CMV, and 4 experienced reactivation during the study. Virus was never isolated from 4 seropositive children. The level of anti-CMV IgG antibody in seropositive children who remained nonshedders was significantly higher than in children who shed virus during follow-up. On immunoblots, all seropositive nonshedders reacted to a CMV-specific 65 kD antigen, whereas most shedders (80%) did not. These findings suggest that humoral immunity plays a role in controlling persistent CMV infection in children with asymptomatic infection. However, the humoral immunity measured by the neutralizing test and the presence of antibodies against CMV-specific envelope antigens (116 kD/55 kD) apparently play a limited role in modifying persistent excretion and regulating reactivation of latent CMV. Immune evasion by CMV to block these antigens may explain these results.

Structural characteristics of four human hybridoma antibodies specific for the pp65 protein of the human cytomegalovirus and their relationship to human rheumatoid factors

Four human hybridoma antibodies directed against the human cytomegalovirus (CMV) were characterized with respect to their immunoglobulin gene usage and expression of rheumatoid factor (RF) associated idiotypes and variable region epitopes. The aims of these experiments were: (1) to characterize the immunoglobulin gene usage of four antibodies directed against a single protein of a human pathogen; and (2) to examine how this humoral response may be linked to the production of RFs, autoantibodies found in the majority of patients with rheumatoid arthritis (RA). All four anti-CMV antibodies were of the gamma heavy chain isotype and were specific for the immunodominant 65 kDa viral matrix phosphoprotein (pp65). The four anti-pp65 antibodies expressed different light (L) and heavy (H) chain variable region gene combinations. These were: VkIII/VH3, V lambda 1/VH3, V lambda 1/VH4 and V lambda 3/VH3, respectively for the HCV-2, HCV-3, HCV-63 and HCV-65 hybridoma cell lines. Although none had RF activity, each of these antibodies expressed a unique set of RF-associated determinants, implying different three-dimensional configurations of the variable regions of these antibodies. The HCV-2 antibody, however, had the most extensive similarities to human RFs since it not only expressed the greatest number of RF-associated determinants but also had a protein sequence that was very homologous to RFs of the "Po" idiotypic family. Furthermore, predicted germline gene usage by anti-CMV antibodies and RFs suggest that some are encoded by identical or similar genes and that the different specificities are achieved by somatic mutations in the L and H chain complementarity determining regions (CDRs) and genetic diversity in the H chain CDR3.

Double fluorescence analysis of human cytomegalovirus (HCMV) infected human fibroblast cultures by flow cytometry: increase of class I MHC expression on uninfected cells and decrease on infected cells

Cultured human foreskin fibroblasts (HFF) were infected with different multiplicities of infection (moi 0.001-0.1) of human cytomegalovirus (HCMV) strain AD 169 or a clinical isolate. Percentage of infected cells was determined by analysis of immediate early (IEA), early (EA), and late (LA) virus antigen expression with flow cytometry or by immunoperoxidase staining. Changes in the expression of class I MHC surface molecules were demonstrated by comparing the mean fluorescence intensities of infected HFF cultures with those of mock infected cell cultures by flow cytometry. At day three post infection single fluorescence analysis showed that infected HFF cultures split into low and high density class I MHC bearing cells. The addition of anti-interferon beta reduced the expression of class I MHC, distinctly. The assumption that infected cells down-regulate and uninfected cells up-regulate their expression of class I MHC molecules was demonstrated by double fluorescence analysis both with flow cytometry and fluorescence microscopy. Analysis of class I MHC-antigen expression versus immediate (IEA, mab E13), early (EA, mab 9221), or late (LA, mab BM219) virus antigen expression yielded three cell populations of HCMV infected HFF cultures three days post infection: 1. uninfected cells with an increase of class I MHC, 2. high density class I MHC, IEA and/or EA expressing cells, and 3. low class I MHC, IEA, EA and LA expressing cells.

A comparative study of congenital and postnatally acquired human cytomegalovirus infection in infants: lack of expression of viral immediate early protein in congenital cases

Postmortem tissues from infants with congenital and postnatally acquired human cytomegalovirus (HCMV) infection were examined by routine histology, immunohistochemistry (IHC) and in situ hybridization (ISH) to determine the dynamics of viral replication in vivo. Histologically, infants in both groups showed characteristic inclusion-bearing cells most commonly in lung, kidney, liver and pancreas. IHC for late proteins using a rabbit polyclonal antibody and ISH for viral genomes detected most of the infected cells as nuclear and/or cytoplasmic signals. However, immunostaining with a monoclonal antibody against viral immediate early (IE) proteins was variable depending on the stage of viral replication within an individual infected cell. In tissues of infants with postnatal HCMV infection, many cells harboured IE antigens, while in tissues from congenital cases most of the affected cells lacked IE antigens and only a few showed cytoplasmic staining. The difference was not caused by the antigenic diversity among viral strains as confirmed by in vitro study. Our findings suggested that congenital infections exhibited uniformly late stage proteins with inactive viral replication at death, while acquired ones remained active. The different viral activity may reflect the immune status of congenital and acquired HCMV infections.

The immediate early genes of human cytomegalovirus upregulate tumor necrosis factor-alpha gene expression

Cytomegalovirus (CMV) is an important cause of disease in the immunocompromised patient and CMV infection is associated with predominantly mononuclear inflammatory response. Since products of the CMV immediate early (IE) gene region are potent trans-activators, we used the monocyte cell line THP-1 and a transient transfection assay to determine if these viral proteins upregulate expression of the TNF gene. The IE genes of CMV upregulated TNF gene activity as judged by increases in promoter activity, steady state mRNA, and protein production. The presence or absence of the 3' untranslated region of the TNF gene did not affect gene expression induced by the IE gene products. These studies suggest that activation of TNF gene expression by the CMV IE gene products may, in part, account for the inflammatory response associated with CMV infections.

Further studies of 31 temperature-sensitive mutants of mouse cytomegalovirus: thermal stability, replication and analysis of temperature-sensitive functions by temperature shift

A study of 31 temperature-sensitive mutants of mouse cytomegalovirus has indicated that two mutants (tsm1, tsm31) may be defective in immediate-early/early functions, two (tsm2, tsm3) may be defective in early functions and six (tsm9, tsm18, tsm22, tsm23, tsm28, tsm30) may be defective in early/late functions while the remainder are late function-defective mutants as determined by temperature-shift experiments. Three mutants (tsm1, tsm2, tsm3) were more thermostable than wild-type virus while three (tsm16, tsm26, tsm28) were more thermolabile; the remainder were similar in their thermostability to wild-type virus.

Isolation and preliminary characterisation of twenty-five temperature-sensitive mutants of mouse cytomegalovirus

To study the pathogenicity of mouse cytomegalovirus (MCMV) and to identify virulence determinants, we have isolated and phenotypically characterised 25 temperature-sensitive (ts) mutants. Six of these (tsm9, tsm13, tsm20, tsm22, tsm28 and tsm30) failed to replicate in mice and were avirulent. Five mutants (tsm14, tsm18, tsm19, tsm25 and tsm27) were of similar virulence to the parental wild-type (wt) virus, five (tsm7, tsm15, tsm24, tsm26 and tsm31) were 12-100 fold less virulent, five (tsm8, tsm12, tsm16, tsm23 and tsm29) were 150-1500 fold less virulent and four (tsm10, tsm11, tsm17 and tsm21) were between 2,000 and 85,000 fold less virulent than wt. One mutant (tsm28) did not plaque or replicate at 39 degrees C while 5 other mutants (tsm7, tsm9, tsm23, tsm24 and tsm27) also failed to plaque at 39 degrees C but only failed to replicate or replicated poorly at 40 degrees C. A further two mutants (tsm10 and tsm13) were able to plaque and replicate at 39 degrees C but not 40 degrees C. Six other mutants (tsm14, tsm15, tsm16, tsm21, tsm22 and tsm30) failed to form plaques at 40 degrees C and were severely restricted in their replication at 40 degrees C. The remaining 11 mutants exhibited varying degrees of restriction in ability to plaque and/or replicate at non-permissive temperatures. These 25 mutants, together with 6 isolated previously, comprise at least 24 complementation groups.