Nuclear expression of the lower matrix protein of human cytomegalovirus in peripheral blood leukocytes of immunocompromised viraemic patients

The pentameric complex of human Cytomegalovirus: cell tropism, virus dissemination, immune response and vaccine development

Between the 1980s and 1990s, three assays were developed for diagnosis of human cytomegalovirus (HCMV) infections: leuko (L)-antigenemia, l-viremia and l-DNAemia, detecting viral protein pp65, infectious virus and viral DNA, respectively, in circulating leukocytes Repeated initial attempts to reproduce the three assays in vitro using laboratory-adapted strains and infected cell cultures were consistently unsuccessful. Results were totally reversed when wild-type HCMV strains were used to infect either fibroblasts or endothelial cells. Careful analysis and sequencing of plaque-purified viruses from recent clinical isolates drew attention to the ULb' region of the HCMV genome. Using bacterial artificial chromosome technology, it was shown by both gain-of-function and loss-of-function experiments that UL131-128 genes are indispensable for virus growth in endothelial cells and virus transfer to leukocytes. In addition, a number of clinical isolates passaged in human fibroblasts had lost both properties (leuko-tropism and endothelial cell-tropism) when displaying a mutation in the UL131-128 locus (referred to as UL128L). In the following years, it was shown that pUL128L was complexed with gH and gL to form the pentameric complex (PC), which is required to infect endothelial, epithelial and myeloid cells. The immune response to PC was studied extensively, particularly its humoral component, showing that the great majority of the neutralizing antibody response is directed to PC. Although anti-HCMV antibodies may act with other mechanisms than mere neutralizing activity, these findings definitely favour their protective activity, thus paving the way to the development of a potentially protective HCMV vaccine.

CMV infection, TLR-2 and -4 expression, and cytokine profiles in early-onset preeclampsia with HELLP syndrome

PROBLEM

Cytomegalovirus (CMV) infection was previously reported in pregnancy complications. However, its seroprevalence and associated Toll-like receptor (TLR) expression in early-onset preeclampsia (EOPE) with hemolysis, elevated liver enzyme and low platelets syndrome (HELLPs) are unexplored.

METHOD OF STUDY

A case–control study was performed to examine maternal CMV antibodies, neutrophil Toll-like receptor (TLR)-2 and -4 expression as well as the cytokine profile in EOPE with HELLPs (EOPE-HELLPs) (n = 10), late-onset preeclampsia (LOPE) (n = 20), normal pregnancy (n = 60), and non-pregnancy (n = 20) controls.

RESULTS

EOPE-HELLPs had significantly increased CMV IgG sero-positivity, upregulated TLR-2/-4 mRNA expression, increased serum IL-6 and TNF-α, and reduced IL-10 compared with matched normal and non-pregnancy controls. No significant difference was observed between LOPE and normal pregnancy controls.

CONCLUSION

We observed a significant association between CMV IgG sero-positivity and innate immune response in EOPE-HELLPs. Our data suggest that CMV infection may be a risk factor for this disorder.

Role of human cytomegalovirus tegument proteins in virion assembly

Like other herpesviruses, human cytomegalovirus (HCMV) contains a unique proteinaceous layer between the virion envelope and capsid, termed the tegument. Upon infection, the contents of the tegument layer are delivered to the host cell, along with the capsid and the viral genome, where they facilitate the initial stages of virus replication. The tegument proteins also play important roles in virion assembly and this dual nature makes them attractive potential targets for antiviral therapies. While our knowledge regarding tegument protein function during the initiation of infection has been the subject of intense study, their roles in assembly are much less well understood. In this review, we will focus on recent studies that highlight the functions of HCMV tegument proteins during assembly, and pose key questions for further investigation.

Endothelial cells and CMV dissemination

Evaluation of: Sacher T, Andrassy J, Kalnins A et al. Shedding light on the elusive role of endothelial cells in cytomegalovirus dissemination. PLoS Pathog. 7(11), E1002366 (2011). Using the murine CMV animal model and the well-established model of Cre-lox-P-mediated green-fluorescence tagging of endothelial cell (EC)-derived mouse CMV to quantify the role of infected ECs in transplantation-associated CMV dissemination (in mice expressing Cre recombinase under the control of either the Tie2 or the Tek promoter selectively expressed in vascular EC-Tie-Cre and Tek-Cre mice), it was shown that EC-derived virus contributed to 50% of the total viral load during primary infection, and there was no preference for dissemination of EC-derived viruses over viruses produced by other cell types. In addition, during secondary viremia, there was only a negligible contribution of EC-derived virus to dissemination to other organs. These results are novel in the methodology employed and are somewhat interesting. However, the data are limited to the mouse model with a short-term follow-up, and the immunodeficient host has not yet been studied. In humans, these conclusions must be taken with caution. First, in primary infection occurring through natural routes, epithelial cells are infected first, then ECs, unless primary infection occurs through blood transfusion, in which case endothelial vascular cells may become infected first. In both cases, the virus transport occurs through the intervention of leukocytes, namely monocytes and polymorphonuclear leukocytes. As monocytes differentiate to macrophages, they become highly susceptible to human CMV replication inside organ tissues, while polymorphonuclear leukocytes are active in virus capturing from infected endothelial vascular cells and transporting to distant sites.

Protein pUL128 of human cytomegalovirus is necessary for monocyte infection and blocking of migration

We have previously shown that only endotheliotropic strains of human cytomegalovirus (HCMV), such as TB40E, infect monocytes and impair their chemokine-driven migration. The proteins encoded by the UL128-131A region (UL128, UL130, and UL131A) of the HCMV genome, which assemble into a pentameric gH-gL-UL128-UL130-UL131A envelope complex, have been recognized as determinants for HCMV endothelial cell tropism. The genes for these proteins are typically inactivated by mutations in all fibroblast-adapted strains that have lost the diversified tropism of clinical isolates. By using mutant HCMV reconstituted from TB40E-derived bacterial artificial chromosomes (BAC) encoding a wild-type (wt) or mutated form of UL128, we show here that UL128-131A products are essential determinants of infection in monocytes and that pUL128, in particular, can block chemokine-driven motility. The virus BAC4, encoding wt UL128, established infection in monocytes, induced the intracellular retention of several chemokine receptors, and rendered monocytes unresponsive to different chemokines. In contrast, the virus BAC1, encoding a mutated UL128, failed to infect monocytes and to downregulate chemokine receptors. BAC1-exposed monocytes did not express immediate-early (IE) products, retained virions in cytoplasmic vesicles, and exhibited normal chemokine responsiveness. A potential role of second-site mutations in the observed phenotype was excluded by using the revertant viruses BAC1rep and BAC4mut. By incubating noninfected monocytes with soluble recombinant pUL128, we observed both the block of migration and the chemokine receptor internalization. We propose that among the gH-gL-UL128-UL130-UL131A complex subunits, the UL128 protein is the one that triggers monocyte paralysis.

Cytomegalovirus UL103 controls virion and dense body egress

Human cytomegalovirus UL103 encodes a tegument protein that is conserved across herpesvirus subgroups. Mutant viruses lacking this gene product exhibit dramatically reduced accumulation of cell-free virus progeny and poor cell-to-cell spread. Given that viral proteins and viral DNA accumulate with normal kinetics in cells infected with mutant virus, UL103 appears to function during the late phase of replication, playing a critical role in egress of capsidless dense bodies and virions. Few dense bodies were observed in the extracellular space in mutant virus-infected cells in the presence or absence of the DNA encapsidation inhibitor 2-bromo-5,6-dichloro-1-(β-d-ribofuranosyl)benzimidazole. Upon reversal of encapsidation inhibition, UL103 had a striking impact on accumulation of cell-free virus, but not on accumulation of cell-associated virus. Thus, UL103 plays a novel and important role during maturation, regulating virus particle and dense body egress from infected cells.

Comparison of polymerase chain reaction of polymorphonuclear leukocytes and plasma identifies patients who control cytomegalovirus infection after hematopoietic cell transplantation

By use of an automated polymerase chain reaction test of plasma and a qualitative polymerase chain reaction assay on polymorphonuclear leukocytes, we identified a subgroup of hematopoietic cell transplant recipients who were able to control cytomegalovirus infection early after hematopoietic cell transplantation without antiviral therapy. Thirty-one percent of patients had cytomegalovirus DNA detected by qualitative polymerase chain reaction assay but had no cytomegalovirus DNA detected by the automated test; this group maintained a lower peak cytomegalovirus load, compared with the group of patients who had cytomegalovirus DNA detected by both tests (P = .03), suggesting a greater degree of functional immune reconstitution.

Tegument proteins of human cytomegalovirus

SUMMARY

Human cytomegalovirus (HCMV) is a common, medically relevant human herpesvirus. The tegument layer of herpesvirus virions lies between the genome-containing capsids and the viral envelope. Proteins within the tegument layer of herpesviruses are released into the cell upon entry when the viral envelope fuses with the cell membrane. These proteins are fully formed and active and control viral entry, gene expression, and immune evasion. Most tegument proteins accumulate to high levels during later stages of infection, when they direct the assembly and egress of progeny virions. Thus, viral tegument proteins play critical roles at the very earliest and very last steps of the HCMV lytic replication cycle. This review summarizes HCMV tegument composition and structure as well as the known and speculated functions of viral tegument proteins. Important directions for future investigation and the challenges that lie ahead are identified and discussed.

Clinical characteristics of cytomegalovirus infection in rheumatic diseases: multicentre survey in a large patient population

OBJECTIVE

To survey and elucidate the clinical characteristics of CMV infection in rheumatic disease patients.

METHODS

A detailed questionnaire survey on CMV infection was carried out against rheumatic disease patients hospitalized in member hospitals, and the obtained clinical and/or laboratory data were analysed.

RESULTS

Out of 7377 patients, 151 were diagnosed as having CMV infection. The underlying diseases ranged broadly, but SLE, microscopic polyangiitis, and dermatomyositis were the most common. Four were diagnosed histopathologically, and the others via positive CMV antigenaemia. In addition to oral corticosteroid for all but one patient, 81 were treated with pulsed methylprednisolone (MPSL), 64 with cyclophosphamide (CYC) and 36 with other immunosuppressants. Forty-four had a fatal outcome, for which presence of clinical symptoms, other infectious complications, lymphopenia, an older age (>59.3 yrs) and the use of pulsed MPSL were significant risk factors (P < 0.05) by univariate analysis. Multivariate analysis retained the first three (P < 0.05). The CMV antigenaemia count was significantly higher for the symptomatic than asymptomatic [10.1 (0.0-2998.0) vs 4.0 (1.3-1144.4)/10(5) PMNs, respectively, P < 0.05; threshold count: 5.6/10(5) PMNs]. No treatment benefit by anti-viral agent was observed as for survival.

CONCLUSION

CMV infection was mostly diagnosed by antigenaemia, and occurred among patients under strong immunosuppressive therapy using pulsed MPSL and/or immunosuppressants. Lymphopenia, presence of symptoms and other infections are significant risk factors for a poor outcome and pulsed MPSL and an older age may predict it. Patients were prone to be symptomatic with anti-genaemia count over 5.6/10(5) PMNs.

Comparison of a new Light Diagnostics and the CMV Brite to an in-house developed human cytomegalovirus antigenemia assay

BACKGROUND

Antigenemia, i.e. detection and quantification of human cytomegalovirus (HCMV) peripheral blood pp65-positive leukocytes, is still one of the two major assays available for diagnosis and monitoring of HCMV infections.

OBJECTIVES

To evaluate the performance of a new commercial assay under development (Light Diagnostics).

STUDY DESIGN

To compare the performance of the new assay with a commercial assay (CMV Brite) already available on 300 blood samples from immunocompromised patients using as a reference the original in-house developed assay.

RESULTS

Although 30 blood samples gave discrepant results among the 3 antigenemia assays, the Light Diagnostics detected an overall number of antigenemia-positive blood samples (sensitivity 84%) identical to that detected by CMV Brite (sensitivity 88%) and in-house assay (91/300, 30.3%). Problems of non-specific cytoplasmic staining were encountered with the CMV Brite assay in 219/300 (73%) blood samples.

CONCLUSIONS

The Light Diagnostics assay provides results comparable to those of the reference assay both in terms of specificity and sensitivity (number of pp65-positive leukocytes).

Monitoring human cytomegalovirus infection in transplant recipients

Human cytomegalovirus (HCMV) infection remains one of the most challenging infectious complications in both solid organ transplant (SOT) and hemopoietic stem cell transplant (HSCT) recipients. In the last two decades advances have been made in the diagnosis and monitoring of HCMV infection in SOT and HSCT recipients following introduction of quantitative assays such as rapid virus isolation in blood (viremia), quantitation of pp65 in peripheral blood leukocytes (antigenemia), and quantitation of viral genome in blood (DNAemia). The availability of these rapid diagnostic assays has allowed treatment administration during the presymptomatic phase of HCMV infection (preemptive treatment) and greatly reduced HCMV-related morbidity and mortality, particularly among HSCT recipients. Definition of clinically validated thresholds for initiating preemptive treatment in SOT and HSCT recipients is a major goal in the transplantation setting. With respect to universal prophylaxis of HCMV infection in transplant recipients, the preemptive treatment approach shows advantages in (i) treating a lower number of patients for shorter periods of time and (ii) avoiding the reported emergence of HCMV disease after interruption of anti-HCMV prophylaxis. To understand the mechanism behind long-term control of HCMV infection in transplant recipients, the HCMV-specific T-cell response must be evaluated.

Functions of human cytomegalovirus tegument proteins prior to immediate early gene expression

Proteins within the tegument layer of herpesviruses such as human cytomegalovirus (HCMV) are released into the cell upon entry when the viral envelope fuses with the cell membrane. These proteins are fully formed and active, and they mediate key events at the very start of the lytic infectious cycle, including the delivery of the viral genome to the nucleus and the initiation of viral gene expression. This review examines what is known about tegument protein function prior to the immediate early (IE) phase of the viral lytic replication cycle and identifies key questions that need to be answered to better understand how these proteins promote HCMV infection so that antiviral treatments that target these important viral regulators can be developed.

Evaluation of Cytomegalovirus DNAaemia versus pp65-Antigenaemia Cutoff for Guiding Preemptive therapy in Transplant Recipients: A Randomized Study

Methods

A bicentre, randomized, prospective open-label study aimed at defining a DNAaemia versus antigenaemia cutoff for guiding preemptive therapy of human cytomegalovirus (HCMV) infections in solid organ transplant recipients (SOTR) was completed. Overall, 99 patients were enrolled in the DNAaemia arm and 101 patients in the antigenaemia arm. Patients were randomized to be monitored for HCMV infection in the blood by either assay. Antiviral treatment was started in both seropositive and seronegative patients when levels greater than 300,000 DNA copies/ml blood or 100 pp65-positive leukocytes in the relevant arm were reached.

Results

HCMV infection was detected in 81/99 (81.8%) patients in the DNAaemia arm and in 87/101 (86.1%) patients in the antigenaemia arm ( P=ns). Antiviral treatment was given to 23/99 (23.0%) patients in the DNAaemia arm and 42/101 (41.0%) patients in the antigenaemia arm ( P=0.01). In the DNAaemia arm, antiviral therapy was significantly delayed and duration of the first course of treatment was significantly greater than in the antigenaemia arm. However, total duration of treatment was comparable in the two arms. No case of HCMV disease occurred in patients treated after reaching the relevant cutoff. However, four patients (three in the antigenaemia arm, and one in the DNAaemia arm) suffered from HCMV disease prior to reaching the relevant cutoff.

Conclusions

Compared with antigenaemia, a single DNAaemia cutoff: (i) significantly reduces the number of patients requiring treatment; (ii) may be safely adopted to guide preemptive therapy of both primary and reactivated HCMV infections in SOTR; and (iii) does not significantly modify the overall duration of treatment.

Novel real-time monitoring system for human cytomegalovirus-infected cells in vitro that uses a green fluorescent protein-PML-expressing cell line

Promyelocytic leukemia (PML) bodies are discrete nuclear foci that are intimately associated with many DNA viruses. In human cytomegalovirus (HCMV) infection, the IE1 (for "immediate-early 1") protein has a marked effect on PML bodies via de-SUMOylation of PML protein. Here, we report a novel real-time monitoring system for HCMV-infected cells using a newly established cell line (SE/15) that stably expresses green fluorescent protein (GFP)-PML protein. In SE/15 cells, HCMV infection causes specific and efficient dispersion of GFP-PML bodies in an IE1-dependent manner, allowing the infected cells to be monitored by fluorescence microscopy without immunostaining. Since a specific change in the detergent solubility of GFP-PML occurs upon infection, the infected cells can be quantified by GFP fluorescence measurement after extraction. With this assay, the inhibitory effects of heparin and neutralizing antibodies were determined in small-scale cultures, indicating its usefulness for screening inhibitory reagents for laboratory virus strains. Furthermore, we established a sensitive imaging assay by counting the number of nuclei containing dispersed GFP-PML, which is applicable for titration of slow-growing clinical isolates. In all strains tested, the virus titers estimated by the GFP-PML imaging assay were well correlated with the plaque-forming cell numbers determined in human embryonic lung cells. Coculture of SE/15 cells and HCMV-infected fibroblasts permitted a rapid and reliable method for estimating the 50% inhibitory concentration values of drugs for clinical isolates in susceptibility testing. Taken together, these results demonstrate the development of a rapid, sensitive, quantitative, and specific detection system for HCMV-infected cells involving a simple procedure that can be used for titration of low-titer clinical isolates.

Human cytomegalovirus UL130 protein promotes endothelial cell infection through a producer cell modification of the virion

Human cytomegalovirus (HCMV) growth in endothelial cells (EC) requires the expression of the UL131A-128 locus proteins. In this study, the UL130 protein (pUL130), the product of the largest gene of the locus, is shown to be a luminal glycoprotein that is inefficiently secreted from infected cells but is incorporated into the virion envelope as a Golgi-matured form. To investigate the mechanism of the UL130-mediated promotion of viral growth in EC, we performed a complementation analysis of a UL130 mutant strain. To provide UL130 in trans to viral infections, we constructed human embryonic lung fibroblast (HELF) and human umbilical vein endothelial cell (HUVEC) derivative cell lines that express UL130 via a retroviral vector. When the UL130-negative virus was grown in UL130-complementing HELF, the infectivity of progeny virions for HUVEC was restored to the wild-type level. In contrast, the infectivity of the UL130-negative virus for UL130-complementing HUVEC was low and similar to that of the same virus infecting control noncomplementing HUVEC. The UL130-negative virus, regardless of whether or not it had been complemented in the prior cycle, could form plaques only on UL130-complementing HUVEC, not control HUVEC. Because (i) both wild-type and UL130-transcomplemented virions maintained their infectivity for HUVEC after purification, (ii) UL130 failed to complement in trans the UL130-negative virus when it was synthesized in a cell separate from the one that produced the virions, and (iii) pUL130 is a virion protein, models are favored in which pUL130 acquisition in the producer cell renders HCMV virions competent for a subsequent infection of EC.

Diagnosis of human cytomegalovirus infections in the immunocompromised host

BACKGROUND

In the last decade several major advances have been made in the rapid diagnosis of human cytomegalovirus (HCMV) infections and disease in immunocompromised patients both at the immunological and molecular level.

OBJECTIVES

The objective was to review in some detail the new diagnostic tools allowing determination and quantitation of HCMV infection in blood of transplanted and AIDS patients.

STUDY DESIGN

The determination and quantitation as well as the clinical significance of antigenemia, viremia, HCMV-infected circulating endothelial cells (CEC) and DNAemia will be discussed in view of the therapeutic management of HCMV disease. Levels of viremia represent the number of p72-positive cultured fibroblasts inoculated with 2 x 10(5)PBL, while levels of antigenemia represent number of pp65-positive PBL/2 x 10(5) PBL examined. The number of CEC is determined simultaneously and in parallel with antigenemia. DNAemia, both qualitative and quantitative, can be determined by polymerase chain reaction (PCR) per 1 x 10(5)PBL. The clinical utility of determining either immediate-early or late mRNA is still debated.

RESULTS

In solid organ transplant recipients mean levels of viremia of 100 and of antigenemia of 400 correlate with onset of clinical symptoms. The time between first HCMV positivity and the onset of symptoms (>/= 10 days), together with the observation that most patients with reactivated infection clear virus without treatment, allowed the establishment of an antigenemia cut-off of 100 for the initiation of treatment. On the other hand, seronegative recipients of solid organs from seropositive donors must be treated preemptively, i.e. at first appearance of HCMV positivity in blood. Due to the risk of early appearance of HCMV pneumonia, the same preemptive approach must be used in bone-marrow transplant recipients. In acquired immunodeficiency syndrome (AIDS) patients with HCMV infection/disease, general criteria for initiation of treatment are more difficult to establish and treatment must be maintained. CEC are detected only in untreated disseminated HCMV infections with organ involvement. Qualitative DNA determination is useful only in special cases, such as in aqueous or vitreous humor of AIDS patients with HCMV retinitis. Quantitative DNA levels obtained by PCR are much more helpful for diagnosing HCMV disease and establishing initiation of treatment.

CONCLUSIONS

New diagnostic procedures currently ensure fine monitoring of HCMV infections/diseases and evaluation of the effect of specific antiviral treatment in the immunocompromised host.

Viral diagnosis by antigen detection techniques

BACKGROUND

Diagnosis of viral infections can be obtained in the early stages of a disease by detection of viral antigens directly in the clinical specimen. This has become an important tool for rapid virus diagnosis.

METHODS

Antigens produced during virus infections can be detected either in cells collected from the site of infection by immunohistological investigation or in secretions and blood by solid phase immunoassays (IA). Viruses causing acute respiratory infections can be diagnosed in cells from the respiratory tract, viruses causing vesicular eruptions in epithelial cells from skin scrapings, rabies virus in nerve cells of the brain or epithelial cells from skin and cornea and cytomegalovirus (CMV) matrix antigen, pp65, can be detected in peripheral blood leukocytes (PBL) by immunofluorescence (IF) or immunoperoxidase techniques. The quality of specimens can be easily checked during the reading of results. Some IAs for antigen detection, such as detection of HBsAg and HIV p24 antigen in blood are standardized and sensitive. Others give less sensitive results because of the variation of quality of the clinical specimen. The latex agglutination tests are mainly used for rapid detection of virus or viral antigens in faeces: rota-and adenoviruses; the method may not be very sensitive but yields a result within a few minutes. Assays detecting viral nucleic acids are more sensitive than antigen detection tests because of a tremendous amplification of gene segments obtained by the polymerase chain reaction (PCR). So far such assays are time consuming and expensive and are mainly used in specific clinical situations.

RESULTS

After introduction of specific monoclonal antibodies (Mabs), the antigen detection techniques are increasingly used. the need for quality control, trained staff, and standardized reagents and methods for specimen collection and preparation is now being appreciated. IF for viral respiratory viruses is used for diagnosis and epidemiological studies all over the world. Likewise, IF is still the method most often used for rabies diagnosis. For CMV, the pp65 matrix antigen is shown to be a sensitive marker closely correlated with clinical symptoms. Its detection by the IF technique has proven to be superior to other techniques for prediction of CMV pneumonia in bone marrow transplant patients. IAs are currently used in fully automated systems for large scale diagnosis based on antigen detection in serum specimens. Increase of antibody specificity on the solid phase by use of Mabs directed against the most abundant viral antigen in the clinical specimen shortens the reaction time; this has been employed in most of the constantly appearing new rapid diagnosis kits based on the immunoassay principle.

CONCLUSION

Although, in virology, more sensitive results are obtained by the gene detection method, PCR, directly in clinical samples, viral antigen detection tests are, after the introduction of Mabs for diagnostic purposes, increasingly used because of their low demand on laboratory equipment, their rapid and early result and relatively low cost. Antigen detection is successfully used directly in clinical specimens for rapid diagnosis of many viral infections as well as for identification of tissue culture isolated viruses. With Mab-based IAs the reaction time is shortened and new rapid, almost 'instant test' kits are appearing on the market.

Diagnosis and management of human cytomegalovirus infection in the mother, fetus, and newborn infant

Human cytomegalovirus (HCMV) is the leading cause of congenital viral infection and mental retardation. HCMV infection, while causing asymptomatic infections in most immunocompetent subjects, can be transmitted during pregnancy from the mother with primary (and also recurrent) infection to the fetus. Hence, careful diagnosis of primary infection is required in the pregnant woman based on the most sensitive serologic assays (immunoglobulin M [IgM] and IgG avidity assays) and conventional virologic and molecular procedures for virus detection in blood. Maternal prognostic markers of fetal infection are still under investigation. If primary infection is diagnosed in a timely manner, prenatal diagnosis can be offered, including the search for virus and virus components in fetal blood and amniotic fluid, with fetal prognostic markers of HCMV disease still to be defined. However, the final step for definite diagnosis of congenital HCMV infection is detection of virus in the blood or urine in the first 1 to 2 weeks of life. To date, treatment of congenital infection with antiviral drugs is only palliative both prior to and after birth, whereas the only efficacious preventive measure seems to be the development of a safe and immunogenic vaccine, including recombinant, subunit, DNA, and peptide-based vaccines now under investigation. The following controversial issues are discussed in the light of the most recent advances in the field: the actual perception of the problem; universal serologic screening before pregnancy; the impact of correct counseling on decision making by the couple involved; the role of prenatal diagnosis in ascertaining transmission of virus to the fetus; the impact of preconceptional and periconceptional infections on the prevalence of congenital infection; and the prevalence of congenitally infected babies born to mothers who were immune prior to pregnancy compared to the number born to mothers undergoing primary infection during pregnancy.

Diagnosis and management of human cytomegalovirus infection in the mother, fetus, and newborn infant

Human cytomegalovirus (HCMV) is the leading cause of congenital viral infection and mental retardation. HCMV infection, while causing asymptomatic infections in most immunocompetent subjects, can be transmitted during pregnancy from the mother with primary (and also recurrent) infection to the fetus. Hence, careful diagnosis of primary infection is required in the pregnant woman based on the most sensitive serologic assays (immunoglobulin M [IgM] and IgG avidity assays) and conventional virologic and molecular procedures for virus detection in blood. Maternal prognostic markers of fetal infection are still under investigation. If primary infection is diagnosed in a timely manner, prenatal diagnosis can be offered, including the search for virus and virus components in fetal blood and amniotic fluid, with fetal prognostic markers of HCMV disease still to be defined. However, the final step for definite diagnosis of congenital HCMV infection is detection of virus in the blood or urine in the first 1 to 2 weeks of life. To date, treatment of congenital infection with antiviral drugs is only palliative both prior to and after birth, whereas the only efficacious preventive measure seems to be the development of a safe and immunogenic vaccine, including recombinant, subunit, DNA, and peptide-based vaccines now under investigation. The following controversial issues are discussed in the light of the most recent advances in the field: the actual perception of the problem; universal serologic screening before pregnancy; the impact of correct counseling on decision making by the couple involved; the role of prenatal diagnosis in ascertaining transmission of virus to the fetus; the impact of preconceptional and periconceptional infections on the prevalence of congenital infection; and the prevalence of congenitally infected babies born to mothers who were immune prior to pregnancy compared to the number born to mothers undergoing primary infection during pregnancy.

Cytomegalovirus infections

Over the past two decades, there has been an escalation in the number of patients undergoing immunosuppressive therapy following solid organ or bone marrow transplantation, as well as a dramatic increase in the incidence of AIDS. As a result, human cytomegalovirus (HCMV)--once considered a neonatal disease--has captured great interest and importance as a major pathogen in both immunocompromised and immunocompetent patients. Like other members of herpesviridae family, HCMV establishes latency in myeloid lineage cells with potential for reactivation. The natural history of HCMV infection can be divided into primary infection, latency, and reinfection. This review article briefly discusses the molecular pathogenesis of HCMV, then focuses on the clinical picture of this disease, with emphasis on the skin pathology. Diagnostic methods and treatments are also discussed.

Control of cytomegalovirus lytic gene expression by histone acetylation

Permissiveness for human cytomegalovirus (HCMV) infection is dependent on the state of cellular differentiation and has been linked to repression of the viral major immediate early promoter (MIEP). We have used conditionally permissive cells to analyze differential regulation of the MIEP and possible mechanisms involved in latency. Our data suggest that histone deacetylases (HDACs) are involved in repression of the MIEP in non-permissive cells as inhibition of HDACs induces viral permissiveness and increases MIEP activity. Non-permissive cells contain the class I HDAC, HDAC3; super-expression of HDAC3 in normally permissive cells reduces infection and MIEP activity. We further show that the MIEP associates with acetylated histones in permissive cells, and that in peripheral blood monocytes the MIEP associates with heterochromatin protein 1 (HP1), a chromosomal protein implicated in gene silencing. As monocytes are believed to be a site of viral latency in HCMV carriers and reactivated virus is only observed upon differentiation into macrophages, we propose that chromatin remodeling of the MIEP following cellular differentiation could potentially play a role in reactivation of latent HCMV.

Analytical performance and clinical utility of a nucleic acid sequence-based amplification assay for detection of cytomegalovirus infection

A nucleic acid sequence-based amplification (NASBA) assay for qualitative detection of human cytomegalovirus (CMV) pp67 mRNA was evaluated in a multicenter study. Negative results were obtained for all specimens from 50 CMV-seronegative and 50 CMV-seropositive low-risk whole-blood donors. No interference with CMV mRNA amplification was observed in the testing of 288 specimens containing various potential interfering substances, nonspecifically reacting substances (including mRNA from other herpesviruses), and three anticoagulants. A total of 95% (50 of 51) of CMV-positive (cell culture- and antigenemia immunofluorescence [AG-IFA]-positive) clinical specimens were positive by the NASBA assay. Results from different operators over multiple testing days were consistent for each of four panel members containing different concentrations of CMV mRNA, indicating the reproducibility of the assay. The estimated 95% reliable upper detection limit of the assay was 600 mRNA copies; the lower limit of detection was less than 25 mRNA copies. The clinical utility of the assay was evaluated with longitudinally collected specimens from solid-organ transplant patients (n = 21). A total of 98% (81 of 83) of the specimens from CMV-negative patients were negative by the NASBA assay, while 90% (10 of 11) of patient specimens that were positive by cell culture or AG-IFA were positive by the NASBA assay. Positive NASBA assay results were obtained earlier than AG-IFA or cell culture results for 55% of the patients and at the same time for the remainder of the patients (45%). The overall agreement between the NASBA assay and current reference tests was 86% when active CMV infection was present. These studies indicate that the CMV pp67 mRNA NASBA assay has reproducible and sensitive performance characteristics that should enable more rapid diagnosis of CMV infection.

Cytomegalovirus PP65 antigenemia monitoring as a guide for preemptive therapy: a cost effective strategy for prevention of cytomegalovirus disease in adult liver transplant recipients

BACKGROUND

The aim of the study was to assess the incidence of cytomegalovirus (CMV) infection and disease in adult liver transplant recipients, using routine preemptive therapy guided by the pp65 antigenemia test.

METHODS

Antigenemia was monitored weekly after liver transplantation (OLTX) for the first 3 months, and once a month for another 3 months. CMV seronegative recipients were treated preemptively for the first positive antigenemia. Seropositive recipients were treated only when their antigenemia count reached a threshold of > or =100 positive cells per 200,000 leukocytes.

RESULTS

A total of 144 patients were included between June 1994 and April 1995, of which 137 (95%) were primary OLTX. The percentage of positive antigenemia and CMV disease was 55 and 8%, respectively. Seventy-eight (54%) patients were protocol-monitored for the entire follow-up (group 1) and received appropriate preemptive therapy, although 66 (46%) patients had protocol violation by having missed blood samples or blood drawn at unscheduled times (group 2). Using Cox's proportional hazards model, patients with a first antigenemia count of >11 leukocytes had a significantly higher rate of CMV disease compared to patients with an antigenemia count < or =11 leukocytes (RR = 7.3, 95% confidence interval = 2.2 to 24.5). In a multivariate Cox regression analysis, adjustments were made to control for: group 1 versus group 2, use of OKT3, and serology risk categories. This analysis showed that the relative rate of CMV disease was still significantly higher among patients with antigenemia count >11 leukocytes (adjusted RR = 4.9, 95% confidence interval = 1.3 to 18.1). The estimated cost of preemptive therapy was less than that of prophylaxis with i.v. (14-day course) or oral (90-day course) ganciclovir.

CONCLUSIONS

Preemptive therapy guided by pp65 antigenemia is a useful and cost effective strategy for prevention of CMV disease.

Prevention and treatment of cytomegalovirus infection in organ transplant recipients

Cytomegalovirus (CMV) is the most common viral pathogen in organ transplant recipients. The patients at highest risk of developing CMV disease are seronegative recipients of seropositive donors, and seropositive recipients who receive antilymphocyte agents such as OKT3 and antithymocyte globulin (ATG) for induction or for rejection. There have been many trials of CMV prevention, but they are difficult to compare with one another because of variability in definitions and end points. Two modalities that have been used to prevent CMV disease are prophylaxis and preemptive therapy. In prophylaxis all patients are given an antiviral agent in order to prevent CMV disease, while in preemptive therapy (also called targeted prophylaxis) only patients who are identified as 'high risk' are selected for treatment. Selected trials of prophylaxis and preemptive therapy in solid-organ recipients are reviewed. The factors to be considered in using one modality or the other are side effects from antivirals, cost of monitoring and antivirals, efficacy of the two modalities, and potential emergence of drug resistance. Sensitive tests that have been used for early diagnosis and monitoring of CMV are antigenemia and the polymerase chain reaction (PCR). Antigen pp65 is a lower matrix protein and can be detected in peripheral blood leukocytes. The sensitivity and specificity are high and vary from 89% to 100% and 92% to 96%, respectively. Currently, many authors believe that the antigenemia test is more useful than the PCR test. The antigenemia test is useful for viral monitoring as a guide for preemptive therapy after organ transplantation. Persistence of high counts of antigenemia may indicate inadequate antiviral therapy or emergence of resistance. Recurrence of positive antigenemia after treatment of CMV disease can be a sign of relapse. Transplant patients who develop resistance to antiviral drugs are usually seronegative recipients who receive an organ from a seropositive donor and have several courses of antivirals for CMV disease. Ganciclovir is the most frequent antiviral agent used in transplant recipients and is usually well tolerated. Resistance to ganciclovir may occur and is usually secondary to virus mutation in the UL97 gene. The availability of sensitive diagnostic tests such as pp65 antigenemia has made the early diagnosis of CMV possible in organ transplant recipients. CMV is being treated much earlier now, and progression to disseminated disease is uncommon. Prudent use of antiviral drugs will hopefully limit the problem of drug resistance.

Use of reverse transcription polymerase chain reaction with colorimetric plate hybridization to detect a cytomegalovirus late spliced mRNA in polymorphonuclear leukocytes from renal transplant patients

Human cytomegalovirus replication was evaluated in polymorphonuclear leukocytes from ten renal transplant recipients. Three new reverse transcription polymerase chain reactions with plate hybridization suitable for automation were developed for the detection of immediate-early spliced UL123 mRNA, early-late pp65 mRNA, and late spliced UL22 mRNA. The presence of UL22mRNA was found to be significantly associated with the occurrence of cytomegalovirus (CMV) disease.

Detection of cytomegalovirus proteins by flow cytometry in the blood of patients undergoing hematopoietic stem cell transplantation

Cytomegalovirus (CMV) infection and associated diseases continue to be a major complication encountered by patients undergoing high-dose chemoradiotherapy and hematopoietic stem cell transplantation (HSCT). A number of studies revealed that identification of CMV in the blood of HSCT patients was a predictor of future CMV disease. The purpose of this study was to determine if CMV proteins detected by flow cytometry could be a rapid and more quantitative way to monitor CMV infections and CMV antigenemia in HSCT patients. Preliminary studies showed that CMV immediate early (IE), early (E), and late (L) tegument proteins were specifically identified in CMV-infected cell lines and not in uninfected cells. We evaluated CMV antigen detection by flow cytometry in blood samples collected before and after transplantation in 56 serially collected blood samples from 17 HSCT patients and CMV protein expression was compared to CMV isolation. CMV IE and E proteins were not detected in any of the samples analyzed. However, CMV L protein detection by flow cytometry correlated with virus isolation in serially collected blood samples. Samples from 14 patients were evaluated by both techniques, at the same time intervals. There was a 100% correlation (8/8) between the lack of CMV antigen detection by flow cytometry and the failure to isolate infectious virus. Moreover, 5 of 6 patients who were positive for CMV L antigen by flow cytometry also were positive by virus isolation techniques. When flow cytometry and virus isolation did not detect CMV antigen on the same day, CMV positivity was first detected by flow cytometry. Then, 1-2 weeks later, positive virus isolation was documented. This study indicates that flow cytometric identification of CMV antigenemia correlates with isolation of CMV in HSCT patients and may be a predictive test for the rapid detection of CMV in the blood.

Polo-like kinase 1 as a target for human cytomegalovirus pp65 lower matrix protein

Human cytomegalovirus (HCMV) pp65 protein is the major constituent of viral dense bodies but is dispensable for viral growth in vitro. pp65 copurifies with a S/T kinase activity and has been implicated in phosphorylation of HCMV IE1 immediate-early protein and its escape from major histocompatibility complex 1 presentation. Furthermore, the presence of pp65 correlates with a virion-associated kinase activity. To clarify the role of pp65, yeast two-hybrid system (THS) screening was performed to identify pp65 cellular partners. A total of 18 out of 48 yeast clones harboring cDNAs for putative pp65 binding proteins encoded the Polo-like kinase 1 (Plk1) C-terminal domain. Plk1 behaved as a bona fide pp65 partner in THS control crosses, and the interaction was confirmed by in vitro binding experiments. Endogenous Plk1 was coimmunoprecipitated with pp65 from transiently transfected COS7 cells. In infected fibroblasts, Plk1 was coimmunoprecipitated with pp65 at late infection stages. Furthermore, Plk1 was detected within wild-type HCMV particles but not within the particles of a pp65-negative mutant (RVAd65). The hydrophilic region of pp65 was phosphorylated in vitro by Plk1. These results suggest that one function of pp65 may be to capture a cell kinase, perhaps in order to alter its activity, nucleotide preference, substrate specificity, or subcellular localization to the advantage of HCMV.

Quantitative cytomegalovirus DNA level in the blood and its relationship to cytomegalovirus retinitis in patients with acquired immune deficiency syndrome

OBJECTIVE

A pilot study was performed to determine whether relationships exist between changes in a quantitative solution hybridization assay for cytomegalovirus (CMV) DNA in the blood and development of CMV retinitis, development of nonocular CMV disease, or reactivation of pre-existing CMV retinitis lesions.

DESIGN

Observational case series.

PARTICIPANTS

Two groups of human immunodeficiency virus-infected patients: 10 CMV antibody-positive patients with CD4+ T-lymphocyte counts of less than 50 ml and no CMV disease at baseline and 11 patients with CMV retinitis but no extraocular CMV disease at baseline.

INTERVENTION

Quantitative changes in leukocyte-associated CMV DNA levels were observed over time. Anti-CMV therapies were based on clinical findings only.

MAIN OUTCOME MEASURES

Development of CMV end-organ disease or change in activity of pre-existing CMV retinitis lesions was measured.

RESULTS

Among patients with no CMV disease at baseline, four had CMV disease develop during follow-up (three cases of CMV retinitis, one case of presumed CMV esophagitis); all had CMV DNA levels greater than 5000 genomes/ml before the onset of CMV disease. The remaining six patients had levels less than 5000 genomes/ml throughout follow-up (P = 0.05). Among patients with CMV retinitis at baseline, all whose CMV DNA blood levels rose more than tenfold had extraocular CMV disease or reactivation of CMV retinitis develop. Raised CMV DNA blood levels were not seen in every patient with clinical reactivation of CMV retinitis.

CONCLUSION

Elevated or rising CMV DNA blood levels appear to be associated with the development of CMV disease in individuals with low CD4+ T-lymphocyte counts. In patients with CMV retinitis, rising levels appear to be associated with the development of extraocular CMV disease or reactivation of CMV retinitis. Conversely, reactivation of CMV retinitis also may occur in the absence of changes in CMV DNA blood levels. Further studies are warranted to determine whether changes in CMV blood levels can be used as a guide for preemptive therapy to prevent reactivation of CMV retinitis lesions or to help choose between local and systemic therapy for management of reactivations.

Use of the human cytomegalovirus (HCMV) antigenemia assay for diagnosis and monitoring of HCMV infections and detection of antiviral drug resistance in the immunocompromised

BACKGROUND

Quantification of viral load in blood has proven to be helpful in the follow-up of disseminated HCMV infections in immunocompromised patients.

OBJECTIVES

(i) To describe the antigenemia assay and its optimization and (ii) to analyze the use of the antigenemia assay for the diagnosis and monitoring of HCMV infections and for the detection of treatment failures.

STUDY DESIGN

This article is intended to give an overview of our experience in the use of the antigenemia assay.

RESULTS AND CONCLUSIONS

In solid organ transplant recipients and patients with AIDS, HCMV symptomatic infections mostly appear when antigenemia values are > 300 pp65-positive PBL/2 x 10(5) examined. To avoid the appearance of overt HCMV disease antiviral treatment could be administered when antigenemia levels are > 100 pp65-positive PBL/2 x 10(5) examined. Bone marrow transplant recipients show symptomatic HCMV infections when antigenemia values are > 100 pp65-positive PBL/2 x 10(5) examined. This group of patients should be treated when antigenemia levels are < 10 pp65-positive PBL/2 x 10(5) examined due to the higher mortality rate associated with HCMV complications. A decrease in antigenemia levels during therapy indicates a good response to antiviral drug, while stable or increasing values document a treatment failure and the emergence of drug-resistant HCMV strains.

Quantitation of cytomegalovirus: methodologic aspects and clinical applications

Cytomegalovirus (CMV) is an important pathogen in transplant recipients and human immunodeficiency virus (HIV)-infected individuals. Major progress has been made in developing quantitative detection methods for CMV in recent years. Due to their high sensitivity, these assays can detect CMV early, and quantitation may be useful in predicting the patient's risk for disease and in monitoring the effect of antiviral therapy. This review discusses methodological aspects of currently used quantitative assays for CMV (i.e., viral culture techniques, antigen detection assays, DNA detection assays including PCR, branched-DNA assay, and the DNA hybrid capture assay) and addresses the correlation of systemic and site-specific CMV load and CMV disease in different populations of immunosuppressed patients as well as the response to antiviral treatment. To date, direct antigen detection and molecular techniques have largely replaced traditional culture-based techniques for CMV quantitation. In general, a high systemic CMV load is correlated with CMV disease. This correlation is strong in the HIV-infected population and in solid-organ transplant recipients but less clear in allogeneic marrow transplant recipients. Measuring the viral load at specific anatomic sites may be an alternative way to assess disease activity in situations where the systemic viral load correlates poorly with disease activity. A reduction of the systemic CMV load also correlates with a response to antiviral treatment, but more research is needed to evaluate the role of viral load as a surrogate marker for drug resistance. Due to the widespread use of quantitative CMV detection techniques to direct and monitor antiviral treatment, there is a great need for an assessment of the reproducibility of test results and better standardization of the assays.

In vitro generation of human cytomegalovirus pp65 antigenemia, viremia, and leukoDNAemia

Immunocompromised patients with disseminated human cytomegalovirus (HCMV) infection have circulating PMN carrying HCMV pp65 (antigenemia), infectious virus (viremia), and viral DNA (leukoDNAemia). Because HCMV does not fully replicate in PMN, it is generally hypothesized that virions and viral materials are taken up by phagocytosis from fully permissive HCMV-infected endothelial cells. However, no experimental evidence has ever been provided for these PMN-endothelium interactions. PMN from 11 donors were cocultured with endothelial cells infected with an endothelium-adapted HCMV strain and with human fibroblasts infected with low-passaged clinical and laboratory-adapted HCMV strains. pp65-positive PMN were detected after coculture with both HCMV-infected endothelial and fibroblast cells, provided that wild and not laboratory-adapted strains were used. In addition, cocultured PMN carried infectious virus as demonstrated by virus isolation and presence of complete virus particles by electron microscopy. Moreover, high levels of viral DNA were consistently detected by quantitative PCR in cocultured PMN. Thus, we have generated in vitro the three most important viral parameters detected in patients with disseminated HCMV infection (antigenemia, viremia, and leukoDNAemia). The failure of laboratory-adapted HCMV strain to induce this phenomenon demonstrates that important modifications have occurred in attenuated viral strains affecting basic biological functions.

Defective growth correlates with reduced accumulation of a viral DNA replication protein after low-multiplicity infection by a human cytomegalovirus ie1 mutant

To investigate the importance of the IE1 p72 regulatory protein during human cytomegalovirus replication, a recombinant virus unable to synthesize IE1 p72 was constructed. The Towne strain mutant CR208 lacked exon 4 of the major immediate-early gene and was isolated and complemented in an IE1-expressing immortalized human fibroblast line (ihfie1.3). Replication of CR208 in primary human fibroblasts was completed after an input multiplicity of 10 PFU/cell but was severely-impaired at 0.1 PFU/cell. CR208 formed plaques with lower efficiency on primary fibroblasts than on ihfiel.3 cells, and the relationship between the CR208 inoculum size and the resulting number of undersized plaques was nonlinear, indicating that multiple particles of CR208 were required to initiate lytic replication in a single primary fibroblast. After infection of primary fibroblasts with CR208 at 5 PFU/cell, a normal pattern of viral antigens was detected, although IE1 p72 was absent. During lower-multiplicity infections, IE2 protein was consistently detected at similar levels in a similar proportion of CR208-infected cells relative to the case for a Towne infection, but many fewer CR208-infected cells contained the ppUL44 polymerase accessory protein when evaluated at 24 or 48 h after infection. Furthermore, fibroblasts infected with CR208 at a low multiplicity failed to form viral DNA replication compartments, despite having expressed IE2 p86. These low-multiplicity growth and expression defects were corrected in two rescued derivatives of CR208 able to synthesize IE1 p72. One rescued virus (CR249) carried a deletion removing the large intron between exons 1 and 2 of the ie1-ie2 locus, revealing that this intron was dispensable for growth in cell culture.

Semi-quantitative detection of cytomegalovirus DNA from native serum and plasma by nested PCR: influence of DNA extraction procedures

The diagnostic implications of different procedures of DNA extraction were examined for the detection of HCMV DNA from sera and plasma of immunosuppressed patients. The detection limit of HCMV plasmid DNA from cell free seronegative plasma and serum by limiting dilution nested PCR decreased in the following sequence: phenol/chloroform > NaI-single tube method > proteinase K digestion equal to amplification of native sera and plasma. Nested PCR from native sera and plasma performed well and surpassed the proteinase K method in sensitivity for detection of serum DNAemia. Semi-quantitative determination of HCMV DNA titer present in native sera of immunosuppressed patients did not seem to be correlated to HCMV disease. When compared to the persistence of leukoDNAemia, the viral DNA titer in native plasma could only be observed in the acute phase of HCMV infection, an important phenomenon for diagnostic purposes. Correlation of serum DNAemia to virus culture revealed low positive and high negative predictive values. Predictive values of nested PCR from native sera for HCMV infection were not lower than those following organic DNA extraction. Despite its low correlation to viremia and virus isolation from any site, nested PCR from organic DNA extracts of serum or plasma is the most sensitive diagnostic tool of an ongoing HCMV infection. Additionally, semi-quantitative end point dilution nested PCR from native serum or plasma promises to be a rapid and easy tool for the monitoring of antiviral therapy.

Comparison of culture and the antigenemia assay for detection of cytomegalovirus in blood specimens submitted to a reference laboratory

We compared the antigenemia assay (AA) with tandem shell vial cultures (SVCs) and tube cultures (TCs) for detection of cytomegalovirus (CMV) in 343 blood specimens. For 249 specimens, the AA was performed in duplicate with two different commercially available monoclonal antibody reagents (Biotest Diagnostic Corporation and Argene Biosoft). Specimens considered true positives were positive in either culture system or both AAs. Only specimens which were negative in both cultures and positive in a single AA were tested retrospectively with a CMV PCR assay. CMV recovery rates were also calculated to determine if increased specimen age resulted in decreased positivity. CMV recovery rates for the AA and the combination of both cultures were 20.0 and 5.0% at 3 to 18 h, 20.2 and 14.0% at 18 to 35 h, 12.5 and 7.8% at 36 to 52 h, and 18.8 and 6.3% at 64 to 75 h, respectively. The sensitivities and specificities of the Biotest AA, the Argene AA, SVC, and TC were 84.4 and 100.0, 100.0 and 99.6, 44.4 and 100.0, and 46.0 and 100.0%, respectively. The AA was significantly more sensitive than either culture method alone and was also more sensitive than the two culture methods used in tandem (the tandem culture sensitivity was 63.5%); the Argene AA identified more positives than the Biotest AA.

Infection of blood and bone marrow cells with the human cytomegalovirus in vivo

The human cytomegalovirus (HCMV) is a major pathogen in immunocompromised patients. Both, primary infection and reactivation of latent virus can cause disease. Peripheral blood leukocytes (PBL) most likely play an important role in viral persistence and dissemination of infection. However, an open question has been whether HCMV actively replicates in PBL in vivo and whether the progenitor cells in the bone marrow are also infected. Previous studies on this issue are controversial. Here we summarize data on the tropism of HCMV for mature leukocyte populations as well as bone marrow progenitor cells during HCMV viremia. All cell populations were highly purified by a fluorescence activated cell sorter (FACS) and analyzed by PCR for the presence of viral genomic DNA. Moreover, mature leukocyte populations were investigated for mRNA expression of regulatory and viral structural proteins. We could show, that HCMV DNA was detected most frequently in granulocytes and monocytes as well as in CD34+ progenitor cells of immunosuppressed patients. Viral mRNA expression was found in granulocytes, monocytes, and lymphocyte fractions. In contrast, no HCMV DNA was found in healthy, seropositive individuals.

The effect of human cytomegalovirus on selected functions of peripheral blood monocytes

The effect of in vitro infection of human cytomegalovirus (HCMV) on various monocyte functions relevant to antimicrobial defence mechanisms has been investigated: the phagocytic activity of monocytes, the release of lysozyme and intracellular concentration of acid phosphatase, and the release of the cytokines interleukin-1 (IL-1), IL-6, and tumour necrosis factor-alpha (TNF-alpha). HCMV significantly inhibited the release of lysozyme and intracellular concentration of acid phosphatase. Regarding the phagocytic activity and the release of cytokines, there was considerable variation in the HCMV effect among the different blood donors tested. There was no clear tendency in the observed results; both stimulation and inhibition were seen. The HCMV-specific pp65 was detected in the nucleus of about 1% of the monocytes 3 h after infection and HCMV-specific IE antigens were found in about 0.1% of the monocytes 2 days postinfection. No E- or L-gene expression was observed and no infectious virus was produced in the monocytes. Our results indicate that HCMV infection may influence monocyte functions in spite of no productive infection of these cells.

Significance of cytomegalovirus (CMV)-pp65 antigenemia in the diagnosis of CMV disease in human immunodeficiency virus-infected patients

To establish the diagnostic value of the cytomegalovirus (CMV)-pp65 antigenemia in CMV disease occurring in human immunodeficiency (HIV)-infected patients, CMV-pp65 antigen in polymorphonuclear leukocytes (PMNLs) was assayed in 373 samples from 138 randomly included patients followed up for symptomatic HIV-1 infection and the correlation between CMV-pp65 antigenemia and diagnosis of CMV disease was investigated. Thirty-seven CMV disease episodes were observed in 30 patients and 89.2% of these episodes were associated with a positive CMV-pp65 antigenemia. In contrast, 94% of the patients negative for CMV-pp65 antigenemia remained free of CMV disease. Patients with CMV disease had significantly higher levels of CMV-pp65 antigenemia than CMV disease-free patients (695 positive cells/2 x 10(5) PMNLs vs. 28 positive cells/2 x 10(5) PMNLs). The positive and negative predictive values of the test were 45% and 94%, respectively, but were 93% and 80%, respectively, when a CMV-pp65 antigenemia level of > 100 positive cells/2 x 10(5) PMNLs was taken into consideration. These results indicate that the CMV-pp65 antigenemia assay is useful for the diagnosis and monitoring of CMV disease in HIV-infected patients.

Stably expressed antisense RNA to cytomegalovirus UL83 inhibits viral replication

The human cytomegalovirus (HCMV) open reading frame UL83 encodes a phosphoprotein of 64 to 68kDa (pp65) which is a major constituent of this virion and dense bodies. To determine the importance of the HCMV gene in the virus cycle, we studied HCMV replication in astrocytoma cells stably transfected with a retroviral vector carrying an antisense UL83 cDNA. Reverse transcription-PCR detected antisense RNA in the cytoplasm. The steady-state level of a 4-kb RNA containing coding sequences for pp65 was significantly reduced after infection of antisense cells. Concomitant with this, levels of expression of pp65 and pp71 (UL82) were severely reduced. Extracellular HCMV production was almost completely blocked, irrespective of the multiplicity of infection or the time after infection studied. The block occurred at an early phase, since immediate-early protein synthesis occurred normally, while several late proteins (e.g., pp150 [ppUL32] and assembly protein [UL80]) were absent or strongly inhibited. Normal replication of herpes simplex virus and of a pp65 deletion mutant of HCMV (RVAd65), lacking target sequences of antisense RNA, demonstrated the specificity of the block for wild-type HCMV in the antisense-stabilized cells and indicated that the block was not due to indirect interference with cellular genes. Our results appear to contradict those of Schmolke et al (S. Schmolke, H.F. Kern, P. Drescher, G. Jahn, and B. Plachter, J. Virol. 69:5959-5968, 1995), which show that UL83 is a nonessential gene for HCMV replication in vitro. This contradiction is discussed in light of the fact that the 4-kb mRNA, which codes for pp65 and was targeted in UL83-antisense cell lines, may be a bicistronic mRNA which also codes for pp71 (UL82). Thus, interference of expression from the genes encoding pp65 and pp71 by blocking of this putative bicistronic message leads to severe impairment of viral replication.

Serum polymerase chain reaction for cytomegalovirus DNA for monitoring ganciclovir treatment in AIDS patients

The virological response to antiviral treatment of cytomegalovirus (CMV) infection in patients with AIDS can be monitored by the identification and quantification of CMV pp65 antigen in blood polymorphonuclear leukocyte cells (PMNL). To assess the value of nested polymerase chain reaction (PCR) in serum for therapy follow-up, we compared PCR and pp65 antigenemia results in 21 acquired immune deficiency syndrome (AIDS) patients with CMV infection, before and after 3 weeks of intravenous ganciclovir at standard doses. pp65 antigenemia was positive in 18/21 (86%) patients at the start of the therapy and in 2/15 (13%) at the end of therapy. CMV DNA was found in serum from 18/21 (86%) patients at the beginning of therapy and in 3/21 (14%) patients after 3 weeks of therapy. A clinical improvement was seen in 16/21 (76%) patients: 11/16 (69%) were negative by both PCR and antigenemia at the end of ganciclovir treatment. The sensitivity and specificity of serum PCR versus the antigenemia assay were 85% and 81%, respectively. Nested PCR on serum can be useful for treatment follow-up of CMV infection in patients with AIDS. It can be used where antigenemia cannot be performed and in retrospective studies.

Cell types involved in replication and distribution of human cytomegalovirus

As the number of patients suffering from severe HCMV infections has steadily increased, there is a growing need to understand the molecular mechanisms by which the virus causes disease. The factors that control infection at one time and the events leading to virus multiplication at another time are only beginning to be understood. The interaction of HCMV with different host cells is one key for elucidating these processes. Through modern techniques, much has been learned about the biology of HCMV infections in culture systems. In addition to endothelial cells, epithelial cells, and smooth muscle cells, fibroblasts are one cell population preferentially infected in solid tissues in vivo. From these sites of multiplication, the virus may be carried by peripheral monocytes and circulating endothelial cells to reach distant sites of the body. This would explain the multiorgan involvement in acute HCMV infection and the modes of viral transmission. From what has been learned mainly from human fibroblast culture systems, future studies will focus on how HCMV regulates the expression of its putative 200 genes in different host cells at different stages of cell differentiation and activation to result in viral latency and pathogenesis.

Quantitation of human cytomegalovirus DNA in bone marrow transplant recipients

HCMV DNA was retrospectively quantitated in the early post-transplant period in 36 paediatric bone marrow transplant (BMT) recipients prospectively monitored for human cytomegalovirus (HCMV) infection on the basis of antigenaemia and viraemia assays. Viral DNA was quantitated in peripheral blood leucocytes (PBL) by PCR using an internal control of amplification and a series of external standards. Densitometric analysis of hybridization results obtained on PCR products enabled construction of a standard curve from which DNA amounts of clinical samples, expressed in terms of genome equivalents (GE), were interpolated. Of the 36 BMT recipients, three had clinically symptomatic HCMV infection with mean peak levels of viral DNA > 5000 GE (antigenaemia and viraemia mean peak levels were 873 and 35, respectively), whereas 19 with HCMV reactivation were asymptomatic (five of them had abortive HCMV infection) showing mean peak DNA levels of 131 GE (and of 6.8 and 1.3 for antigenaemia and viraemia, respectively) (P < or = 0.01). Single or multiple courses of pre-emptive therapy with ganciclovir or foscarnet were given to 14/19 asymptomatic children in whom antigenaemia levels were > 2 or lower yet persisting. Overall, in the 14 asymptomatic treated patients the mean antigenaemia level was 9.3 (range 1-22), and the mean DNA level was 184.6 (range 20-710) GE. Antiviral drugs were also administered to the three symptomatic patients who, due to late diagnosis of HCMV infection, escaped preemptive therapy. Antiviral treatment caused marked decrease or disappearance of viral DNA, antigenaemia and viraemia in both symptomatic and asymptomatic patients. In conclusion, our study suggests that: (i) starting therapy in the presence of a mean antigenaemia level of 9.3 (range 1-22) corresponding to a mean DNA level of 184.6 (range 20-710) GE avoided occurrence of any major HCMV-related clinical complication; (ii) clinical symptoms were associated with antigenaemia levels > 100 and DNA levels > 1000 GE; (iii) the effect of antiviral treatment could be more carefully monitored by quantitation of viral DNA.

Detection improvement of cytomegalovirus antigen in human peripheral blood using monoclonal antibodies and automated reading of cell preparations

One of the major drawbacks in cytomegalovirus (CMV)-antigenaemia detection for diagnosis of active CMV infection is the low number of CMV-antigen positive cells present in peripheral blood. It is therefore necessary to screen large numbers of peripheral blood granulocytes to find only a few antigen-positive cells. We have optimized this detection by testing several monoclonal antibodies (mAb) to CMV-antigens (mAbs C10/C11, C12, BM222, E13 and SL20). In total 550 blood samples from 40 patients were investigated. More blood samples were found positive with mAb C12 than with the other mAbs. Also the average number of positive cells per slide was highest for mAb C12. Furthermore, duplicate slides were examined automatically using an image analysis system (LEYTAS) and compared to visual detection (cytospin slides). The detection sensitivity of both screening methods was compared for mAb C12. In total 360 slides were analysed, from positive as well as negative blood samples. The sensitivity of the automated screening was 93% and for the visual evaluation of the cytospin slides 73%. In conclusion, mAb C12 was the most suitable of the mAbs tested for detection of antigenaemia, and automatic detection of CMV antigenaemia with image analysis of slides is a sensitive method due to the large numbers of cells that can be screened.

Role of antigenemia assay in the early diagnosis and prediction of human cytomegalovirus organ involvement in AIDS patients

The role of an antigenemia assay in the diagnosis and prediction of human cytomegalovirus (HCMV) disease in AIDS patients was evaluated. The clinical history of 62 patients with advanced HIV infection from whom a total of 248 blood samples were drawn and tested by the HCMV antigenemia assay was examined retrospectively. Between December 1992 and January 1994, 28 episodes of HCMV disease with organ involvement were recorded; the antigenemia assay was positive in 23 of them (82.1%). In particular, this test was positive in 11 of 12 (91.6%) first episodes and in 3 of 3 (100%) recurrent episodes occurring in patients not receiving maintenance therapy. The same test was positive in 9 of 13 (69.2%) recurrent episodes occurring in patients receiving maintenance therapy. The first occurrence of HCMV disease was always preceded by a positive antigenemia assay 2 and 4 months before diagnosis (in all 7 patients of the 7 for whom a blood sample was available before HCMV disease). A positive antigenemia test result was not always followed by organ involvement, but a high positive cell count (> 100/200,000 polymorphonuclear leukocytes) strongly correlated with the appearance of HCMV disease in the following 1 to 3 months (100% of cases). The antigenemia assay is a useful and reliable indirect method for the diagnosis and prediction of HCMV end-organ disease in severely and persistently immunocompromised AIDS patients.

Human antibody reactivity against the lower matrix protein (pp65) produced by cytomegalovirus

The lower matrix protein (pp65) is a major product of many laboratory strains of cytomegalovirus (CMV). It is thus an integral part of many CMV serological assays based on native antigen. Recombinant fragments of pp65 have previously been investigated for their usefulness in more-defined assays. The latter antigens have, however, failed to develop a positive response with serum samples derived from a substantial number of infected individuals. Here we show that the human humoral immune response to CMV pp65 is highly diverse and recognizes at least seven distinct but in some cases partly overlapping epitopes. Most of these epitopes could not be mimicked by any of the investigated recombinant or synthetic antigens. Furthermore, when we investigated the ability of human CMV-seropositive serum samples to block the reactivity of pp65-specific antibodies recognizing five different epitopes within pp65, it was evident that several sera did not contain significant levels of antibodies against any of these or overlapping structures. It was thus concluded that the antibody response against CMV pp65 is weak in some CMV-infected individuals, making this antigen unsuitable for use alone in serological screening systems for CMV infection.

Laboratory diagnosis of HCMV-related disease in renal transplant patients - pp65 antigen detection versus nested PCR

BACKGROUND

Sixty-five renal transplant (Tx) recipients were monitored for signs and symptoms of human cytomegalovirus (HCMV) infection.

OBJECTIVES

Different diagnostic markers were evaluated for early and correct diagnosis of HCMV disease.

STUDY DESIGN

Blood and urine samples were obtained in weekly intervals and the following markers were determined: (1) IgG and IgM antibodies in serum using immunofluorescence and ELISA tests; (2) viral shedding in urine by rapid centrifugation culture (RCC); (3) viral antigen (pp65) in peripheral blood leukocytes (PBL) by immunofluorescence and (4) viral DNA in PBL by nested PCR (NPCR).

RESULTS

Twenty-two patients remained free of HCMV infection, 18 patients developed clinical symptoms of HCMV disease, and 25 patients remained asymptomatic in spite of laboratory signs of HCMV infection. For the early detection of HCMV disease, the highest sensitivity was achieved using NPCR (100%) and pp65 antigen detection (94%). RCC and IgM serology were less sensitive (62% and 40% respectively). The differences of sensitivity were significant. Clinical specificity was 47% for NPCR, 79% for pp65 antigen detection, 66% for RCC, and 68% for IgM serology.

CONCLUSION

In contrast to NPCR, pp65 antigen detection was closely correlated with the appearance of clinical disease and proved to be a useful marker in the monitoring of antiviral therapy.