Latent cytomegalovirus infection in blood donors

Transfusion-transmitted CMV infection - current knowledge and future perspectives

Transmission of human cytomegalovirus (CMV) via transfusion (TT-CMV) may still occur and remains a challenge in the treatment of immunocompromised CMV-seronegative patients, e.g. after stem cell transplantation, and for low birthweight infants. Measures to reduce the risk of TT-CMV have been evaluated in clinical studies, including leucocyte depletion of cellular blood products and/or the selection of CMV-IgG-negative donations. Studies in large blood donor cohorts indicate that donations from newly CMV-IgG-positive donors should bear the highest risk for transmitting CMV infections because they contain the highest levels of CMV-DNA, and early CMV antibodies cannot neutralise CMV. Based on this knowledge, rational strategies to reduce the residual risk of TT-CMV using leucoreduced blood products could be designed. However, there is a lack of evidence that CMV is still transmitted by transfusion of leucoreduced units. In low birthweight infants, most (if not all) CMV infections are caused by breast milk feeding or congenital transmission rather than by transfusion of leucoreduced blood products. For other patients at risk, no definitive data exist about the relative importance of alternative transmission routes of CMV compared to blood transfusion. As a result, only the conduction of well-designed studies addressing strategies to prevent TT-CMV and the thorough examination of presumed cases of TT-CMV will achieve guidance for the best transfusion regimen in patients at risk.

Systematic Evaluation of Different Nucleic Acid Amplification Assays for Cytomegalovirus Detection: Feasibility of Blood Donor Screening

Acute primary cytomegalovirus (CMV) infections, which commonly occur asymptomatically among blood donors, represent a significant risk for serious morbidity in immunocompromised patients (a major group of transfusion recipients). We implemented a routine CMV pool screening procedure for plasma for the identification of CMV DNA-positive donors, and we evaluated the sensitivities and performance of different CMV DNA amplification systems. Minipools (MPs) of samples from 18,405 individual donors (54,451 donations) were screened for CMV DNA using the RealStar CMV PCR assay (Altona Diagnostic Technologies), with a minimum detection limit of 11.14 IU/ml. DNA was extracted with a high-volume protocol (4.8 ml, Chemagic Viral 5K kit; PerkinElmer) for blood donor pool screening (MP-nucleic acid testing [NAT]) and with the Nuclisens easyMAG system (0.5 ml; bioMérieux) for individual donation (ID)-NAT. In total, six CMV DNA-positive donors (0.03%) were identified by routine CMV screening, with DNA concentrations ranging from 4.35 × 10(2) to 4.30 × 10(3) IU/ml. Five donors already showed seroconversion and detectable IgA, IgM, and/or IgG antibody titers (IgA(+)/IgM(+)/IgG(-) or IgA(+)/IgM(+)/IgG(+)), and one donor showed no CMV-specific antibodies. Comparison of three commercial assays, i.e., the RealStar CMV PCR kit, the Sentosa SA CMV quantitative PCR kit (Vela Diagnostics), and the CMV R-gene PCR kit (bioMérieux), for MP-NAT and ID-NAT showed comparably good analytical sensitivities, ranging from 10.23 to 11.14 IU/ml (MP-NAT) or from 37.66 to 57.94 IU/ml (ID-NAT). The clinical relevance of transfusion-associated CMV infections requires further investigation, and the evaluated methods present powerful basic tools providing sensitive possibilities for viral testing. The application of CMV MP-NAT facilitated the identification of one donor with a window-phase donation during acute primary CMV infection.

Prevention of Transfusion-Transmitted Cytomegalovirus Infections: Which is the Optimal Strategy?

Traditionally, leukoreduction and selection of blood products from seronegative donors have been used as alternative strategies to reduce the risk of transfusion-transmitted cytomegalovirus infections (TT-CMV) in atrisk patients. After the introduction of universal leukoreduction for red blood cell and platelet concentrates in Germany, a controversy evolved as to whether the additional selection of blood products from seronegative donors would reduce or even increase the risk of TT-CMV. This review summarizes the current knowledge about CMV infections in blood donors and the implications of this information on the effect of potential transfusion strategies. Even though there are conflicting data about the incidence of TT-CMV remaining after the introduction of leukodepletion, it has been clearly shown that both prevalence and concentration of CMV DNA in peripheral blood are highest in newly seropositive donors. Therefore, avoidance of blood products from these donors is the most important goal of any transfusion strategy. This goal can be reached by: i) selection of blood products from seronegative donors, ii) provision of CMV DNA-negative blood products, or iii) provision of blood from long-term seropositive donors. In cases of suspected TT-CMV, all implicated donors should be investigated carefully to gather further knowledge on which donors confer the lowest risk for TT-CMV.

Post-transfusion cytomegaloviremia and persistence of cytomegalovirus in blood

Cytomegaloviremia was documented in seven patients. Three patients were renal transplant recipients and two were liver transplant recipients. One was a postcardiac surgery patient, and one had acute myelogenous leukemia. The transplant patients had received only banked blood or fresh frozen plasma and developed evidence of infection about 1 month after surgery. Illness varied from no apparent signs to fever alone, fever and a morbilliform rash, hepatitis and an infectious mononucleosis syndrome. The virus was isolated from the blood erythrocyte layer, the leukocyte layer, and the plasma and serum, in that order of frequency. In vitro studies demonstrated persistence of inoculated cytomegalovirus in the presence of erythrocytes (and tissue culture media) for up to 21 days. In whole blood under banking conditions, inoculated virus was recovered after 28 days and, in fresh frozen plasma, after 97 days.

Incidence of cytomegaloviremia in blood-bank donors and in infants with congenital cytomegalic inclusion disease

During a 15-month period, cytomegalovirus (CMV) isolations were attempted from leukocytes derived from 290 healthy blood-bank donors. The major proportion of the specimens were tested 2 to 5 hr after donation. However, CMV was not recovered from any of the specimens examined. At the time of donation, 75% of donors had CMV complement-fixing antibodies demonstrable in titers of 10 to >/=320. The age of the study group ranged from 17 to 57 years. During the same time period and with the use of identical isolation techniques, postnatal cytomegaloviremia was demonstrated in four infants with cytomegalic inclusion disease. Failure to detect cytomegaloviremia in 290 normal blood donors questions its occurrence outside pathological conditions. These results do not support the concept that CMV infection, concurrent with post-transfusion mononucleosis syndrome, is transmitted through the blood donor's leukocytes.

Stimulation of cellular DNA synthesis by human cytomegalovirus

Human cytomegalovirus (CMV) is able to induce cellular DNA synthesis in both permissive (human embryonic lung) and nonpermissive (Vero) cells. The induction of cell DNA synthesis was assayed by the incorporation of [methyl-(3)H]thymidine into macromolecules having the buoyant density characteristics of cell DNA. The DNA synthesis induced by CMV infection appears to represent normal semiconservative replication as opposed to repair synthesis. Both strains of CMV tested were capable of inducing cell DNA synthesis. Virus exposed to heat or UV light prior to infection lost the ability to induce DNA synthesis, indicating that a virus-coded function expressed after infection is responsible for stimulation of cell DNA synthesis.

The natural course of primary cytomegalovirus infection in blood donors

BACKGROUND AND OBJECTIVES

As cytomegalovirus (CMV) DNA is frequently detectable in the plasma of recently infected sero-positive blood donors, information concerning primary CMV infection is important for the identification of possibly infectious donors.

MATERIALS AND METHODS

Monitoring of 17 982 donors for CMV antibodies and DNA in plasma identified 14 subjects with ongoing primary CMV infection. Thirteen donors were interrogated for possible sources of infection and CMV-related symptoms, and monitored for CMV antigens, CMV DNA in plasma, leucocytes and urine, course of IgG and IgM antibodies as well as markers of systemic infection and parameters of organ function.

RESULTS

CMV antigens and DNA were detectable in peripheral blood for up to 54 and 269 days respectively. Clearance of CMV DNA from blood correlated with clearance of IgM antibodies, development of IgG antibodies against the membrane glycoprotein gB and development of high avidity IgG antibodies. Eighty-five percent of subjects with primary CMV infection, but even 69% of matched controls reported possibly CMV-related symptoms. Sixty-two and 23%, respectively, had contact with possible sources of infection. One donor developed a febrile illness accompanied by increased levels of CMV DNA in peripheral blood 2 to 3 weeks after seroconversion. In other donors, neither markers of systemic infection nor parameters of organ function correlated with the course of CMV DNA and antigens.

CONCLUSION

Potentially infectious donors can be identified by measuring CMV DNA, IgM antibodies or avidity of IgG antibodies. Alternatively, blood products donated during the first year after seroconversion should not be used for immunocompromised patients.

Primary cytomegalovirus infection following open heart surgery

Among 674 patients undergoing open heart surgery in 1981-82, 86 (13%) were cytomegalovirus (CMV) antibody-negative when tested by an enzyme-linked immunosorbent assay prior to operation. At follow-up, 54 (67%) of 80 patients restudied had seroconverted after the operation, and 35 of the 54 seroconvertants had been ill with fever and elevated liver enzymes. Among the latter 35 patients, 26 demonstrated a significant rise in CMV antibody titre, most often detected in the third week following the onset of illness. The older patients were more susceptible to illness and seroconversion, and there was a positive correlation between age and the number of blood units given. Thus, at least one third of the seronegative patients developed symptomatic CMV illness after open heart surgery. This is a much higher incidence than earlier reported.

The history of cytomegalovirus and its diseases

Intranuclear inclusions typical of cytomegalovirus infections were first noticed in 1881 by German scientists who thought they represented protozoa. After viruses were grown in cell cultures, Weller, Smith and Rowe independently isolated and grew CMV from man and mice in 1956-1957. Antibodies in 30-100% of normal adults indicate not only a past infection, but the presence of a present latent infection. The presence of CMV DNA in tissues and most organs surveyed indicates the ubiquity of latent infection. CMV disease requires the virus and some deficiency of immunity such as occurs in the immature fetus, in AIDS, and in transplant patients on immunosuppressive drugs. Antiviral agents can inhibit CMV replication but they cannot prevent or cure latent infections. A pharmacological approach using the many leads in understanding latency is needed.

Transfusion-Transmitted Cytomegalovirus: Lessons From a Murine Model

Transfusion-transmitted cytomegalovirus (CMV) infection (TT-CMV) continues to complicate blood transfusion therapy, which can lead to severe morbidity or mortality in immunocompromised or immuno-immature recipients. The biological mechanisms that underlie TT-CMV (eg, viral latency in donor monocytes or stimulatory signals in the transfusion recipient leading to cytomegalovirus reactivation) are difficult to study in humans, but can be addressed in animal models. In this review, we discuss a mouse blood transfusion model, which can be used to investigate these issues as well as to validate methods to prevent TT-CMV in at-risk patients.

Latency, chromatin remodeling, and reactivation of human cytomegalovirus in the dendritic cells of healthy carriers

Human cytomegalovirus (HCMV) persists as a subclinical, lifelong infection in the normal human host, but reactivation from latency in immunocompromised subjects results in serious disease. Latency and reactivation are defining characteristics of the herpesviruses and are key to understanding their biology; however, the precise cellular sites in which HCMV is carried and the mechanisms regulating its latency and reactivation during natural infection remain poorly understood. Here we present evidence, based entirely on direct analysis of material isolated from healthy virus carriers, to show that myeloid dendritic cell (DC) progenitors are sites of HCMV latency and that their ex vivo differentiation to a mature DC phenotype is linked with reactivation of infectious virus resulting from differentiation-dependent chromatin remodeling of the viral major immediate-early promoter. Thus, myeloid DC progenitors are a site of HCMV latency during natural persistence, and there is a critical linkage between their differentiation to DC and transcriptional reactivation of latent virus, which is likely to play an important role in the pathogenesis of HCMV infection.

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.

CMV and blood transfusions

Among the human herpesviruses, cytomegalovirus (CMV) is the only one that has assumed significant importance in blood transfusion. Transfusion transmission of CMV (TT-CMV) to seronegative immunocompromised patients can lead to lethal CMV disease. Studies over the past 30 years have demonstrated that monocytes latently infected with CMV represent the primary vector for TT-CMV, and that TT-CMV can be largely abrogated by transfusing at-risk patients with either seronegative units or blood filtered to remove white blood cells. However, the small number of cases of breakthrough TT-CMV that follow transfusion of either seronegative or filtered blood still produce morbidity and mortality. These circumstances have motivated ongoing efforts to provide improved protection from TT-CMV, including the use of CMV DNA amplification for blood screening, and pathogen inactivation to sterilise all blood components prior to transfusion.

Transfusion associated graft-versus-host disease, cytomegalovirus infection and HLA alloimmunization in neonatal and pediatric patients

Modern transfusion support of pediatric patients requires attention to the necessity to provide specialized or modified blood components to these patients who are often immunocompromised and/or affected by very complex medical and surgical illnesses. In this review we will address three potential complications of transfusion that may require specialized components for their prevention in selected patients namely transfusion-associated graft-versus-host disease, transfusion-transmitted cytomegalovirus infection and HLA alloimmunization, with particular reference to the indications for prevention of these transfusion complications in neonatal and pediatric patients.

Quantitative analysis of latent human cytomegalovirus

Cytomegalovirus latency depends on an interaction with hematopoietic cells in bone marrow and peripheral blood. The distribution of viral DNA was investigated by PCR-driven in situ hybridization (PCR-ISH), and the number of viral genomes per cell was estimated by quantitative competitive PCR during both experimental and natural latent infection. During experimental latent infection of cultured granulocyte-macrophage progenitors, the viral genome was detected in >90% of cells at a copy number of 1 to 8 viral genomes per cell. During natural infection, viral genomes were detected in 0.004 to 0.01% of mononuclear cells from granulocyte colony-stimulating factor-mobilized peripheral blood or bone marrow from seropositive donors, at a copy number of 2 to 13 genomes per infected cell. When evaluated by reverse transcription-PCR-ISH, only a small proportion of experimentally infected cells (approximately 2%) had detectable latent transcripts. This investigation identifies the small percentage of bone marrow-derived mononuclear cells that become latently infected during natural infection and suggests that latency may proceed in some cells that fail to encode currently identified latent transcripts.

Growth of human cytomegalovirus in primary macrophages

Human cytomegalovirus (HCMV) is a major human pathogen that causes considerable disease among immunocompromised individuals. A primary infection results in life-long persistence of the virus in a latent form. HCMV is known to be transferred by blood products, bone marrow, and solid organs, but the cell type that carries the latent infection has been difficult to identify. We have recently demonstrated reactivation of latent HCMV in allogeneically stimulated monocyte-derived macrophages (Allo-MDM). Reactivation occurred only in macrophages produced by allogeneic but not mitogenic stimulation. The presence of dendritic cell markers on some Allo-MDM cells suggested that these macrophages were related to dendritic cells. However, dendritic cells obtained by stimulation of monocytes with interleukin-4 (IL-4) and granulocyte-macrophage colony stimulating factor (GM-CSF) were not permissive for HCMV infection. The cellular and cytokine components which are essential for HCMV replication and reactivation of virus were also examined in Allo-MDM. The importance of both CD4- or CD8-positive T cells in the generation of HCMV permissive Allo-MDM was demonstrated by negative selection or blocking experiments using antibodies directed against both HLA class I and HLA class II molecules. Examination of the cytokines essential for the generation of HCMV permissive Allo-MDM identified gamma-interferon (IFN-gamma, but not IL-1, IL-2, tumor necrosis factor alpha, or GM-CSF as critical components in the generation of these macrophages. However, addition of IFN-gamma to unstimulated macrophage cultures was insufficient to reactivate virus. These results indicate the importance of a specific moncyte stimulus in the generation of a unique HCMV permissive macrophage phenotype as well as why virus is commonly reactivated in transplant patients.

Steady-state plasma membrane expression of human cytomegalovirus gB is determined by the phosphorylation state of Ser900

Human cytomegalovirus (HCMV) infection of an astrocytoma cell line (U373) or human fibroblast (HF) cells results in a differential cell distribution of the major envelope glycoprotein gB (UL55). This 906-amino-acid type I glycoprotein contains an extracellular domain with a signal sequence, a transmembrane domain, and a 135-amino-acid cytoplasmic tail with a consensus casein kinase II (CKII) site located at Ser900. Since phosphorylation of proteins in the secretory pathway is an important determinant of intracellular trafficking, the state of gB phosphorylation in U373 and HF cells was examined. Analysis of cells expressing wild-type gB and gB with site-specific mutations indicated that the glycoprotein was equally phosphorylated at a single site, Ser900, in both U373 and HF cells. To assess the effect of charge on gB surface expression in U373 cells, Ser900 was replaced with an aspartate (Asp) or alanine (Ala) residue to mimic the phosphorylated and nonphosphorylated states, respectively. Expression of the Asp but not the Ala gB mutation resulted in an increase in the steady-state expression of gB at the plasma membrane (PM) in U373 cells. In addition, treatment of U373 cells with the phosphatase inhibitor tautomycin resulted in the accumulation of gB at the PM. Interestingly, the addition of a charge at Ser900 trapped gB in a low-level cycling pathway at the PM, preventing trafficking of the protein to the trans-Golgi network or other intracellular compartments. Therefore, these results suggest that a tautomycin-sensitive phosphatase regulates cell-specific PM retrieval of gB to intracellular compartments.

A novel mechanism for persistence of human cytomegalovirus in macrophages

Human cytomegalovirus (HCMV) infection of monocyte-derived macrophages (MDM) results in delayed and nonlytic productive viral growth. During late stages of replication, infectious virus remains cell associated in cytoplasmic vacuoles. In order to understand HCMV survival and persistence in MDM, we examined mechanisms involved in the formation and trafficking of HCMV-containing vacuoles in these cells. Utilizing double-label immunofluorescence with antibodies to viral and cellular proteins, HCMV-containing vacuoles were associated with the Golgi apparatus marker mannosidase II but not with markers to early endosomes (transferrin receptor and rab5) or late endosomes and early lysosomes (LAMP-1 and -2). In addition, as late-stage viral infection progressed in MDM, the cells displayed increasing abnormalities in the Golgi apparatus. Analysis of structural features of infected cells revealed the disruption of the microtubule network. These observations suggest a novel mechanism by which HCMV is vacuolized in MDM, avoiding degradation and release from the cell.

Growth kinetics of human cytomegalovirus are altered in monocyte-derived macrophages

Stimulation of monocytes/macrophages with activated nonadherent cells allows productive nonlytic growth of human cytomegalovirus (HCMV), but the viral replication cycle is delayed relative to replication of HCMV in human fibroblasts. Analysis of infected monocyte-derived macrophage (MDM) mRNA for major immediate-early (MIE 86, 72, and 55) and late (pp65 and gB) gene expression by reverse transcription PCR indicates that transcription peaks at 3 and 7 days postinfection (dpi), respectively. In contrast, in human fibroblast controls, mRNA for MIE and late gene expression peaked at 5 and 48 h postinfection, respectively. Consistent with reverse transcription PCR experiments, double-label antibody experiments first detected MIE antigen expression at 12 h postinfection, peaking at 3 dpi, and late (pp65 or gB) antigen expression at 5 dpi, peaking at 7 dpi. MIE antigen was not detected between 3 and 7 dpi but reappeared and was coexpressed with pp65 in enlarged MDM nuclei at 7 dpi. After 7 dpi, macrophages with numerous vacuoles containing large amounts of pp65 and gB were observed in culture. These vacuoles were frequently seen at cellular contact points, suggesting that cell-to-cell transfer of virus was the major mode of viral transmission. Consistent with this observation, infectious virus was recovered from MDM cellular lysates but not culture supernatant. The delayed growth and compartmentalization of HCMV in macrophages may allow the cell to accommodate the viral replication cycle without cell lysis. In addition, the macrophage may function as a vehicle for cell-to-cell transmission of HCMV.

Transfusion-transmitted cytomegalovirus: the part-time pathogen

Viral infection is a well-known risk of blood product transfusion and much work has been devoted to the detection of such well-known pathogens as human immunodeficiency virus and hepatitis viruses in blood donors. Cytomegalovirus (CMV) is found in a much larger percentage of donor units than these other viruses but will cause disease in only a minority of recipients. Many pediatric patients (especially premature infants) are at risk for transfusion-transmitted CMV. This review describes work delineating the populations of patients most at risk for transfusion-transmitted CMV, describes methods for detecting CMV in blood donors, evaluates current methods for leuko-depletion of blood products, and provides recommendations for patients most likely to benefit from blood products with low risk of CMV transmission.

Human cytomegalovirus DNA is not detectable with nested double polymerase chain reaction in healthy blood donors

The PCR method was introduced to detect cytomegalovirus (CMV) DNA from 189 peripheral blood samples of volunteer donors. We adopted the nested double PCR method with primers specific for immediate early gene 1 followed by electrophoresis and ethidium bromide staining. This nested double PCR method was sensitive enough to detect approximately a single copy of CMV DNA. However, we failed to obtain positive amplification of CMV DNA from any of these donor samples. In contrast, CMV DNA could be detected in all 3 tested immunocompromised patients who had undergone bone marrow transplantation. These results support our previous report that the frequency of CMV DNA is of an order lower than 1 copy/10(5) leucocytes in the peripheral blood of healthy seropositive individuals.

Induction of endogenous human cytomegalovirus gene expression after differentiation of monocytes from healthy carriers

Monocytes are one site of carriage of the human cytomegalovirus (HCMV) genome in healthy human carriers. However, as there are conflicting data detailing the level of HCMV gene expression during persistence in these cells, we have analyzed monocytes for evidence of viral immediate-early, early, and late transcription by using reverse transcription followed by PCR. We were unable to find evidence of HCMV lytic gene transcription in freshly isolated peripheral blood monocytes from HCMV-seropositive subjects. However, as differentiation of monocytes to monocyte-derived macrophages results in increased permissiveness to infection with HCMV in vitro, we examined whether such differentiation could result in reactivation of endogenous viral gene expression. Here we show that in vitro differentiation of monocytes does result in expression of endogenous HCMV immediate-early genes. Although this differentiation led to reactivation of endogenous viral immediate-early expression, we were unable to detect any early or late viral transcription. Cocultivation experiments correlated with this level of gene induction, as no productive infection was detected. These data strongly suggest a mechanism of persistence of HCMV in the peripheral blood that is independent of HCMV lytic gene expression and that initial phases of lytic gene expression in monocytes can be induced by differentiation of these cells to monocyte-derived macrophages.

Cytomegalovirus studies on blood donors in north-east Scotland and a review of UK data

The epidemiology of cytomegalovirus (CMV) infection as assessed by CMV antibody testing varies significantly in different parts of the world and also in different regions of a country. A study was therefore carried out to assess the prevalence of CMV antibody in our blood donors, looking in particular at different subgroups of donors as divided by age, sex and social class, to see how we could maximise the yield of CMV-negative blood from our testing. It was shown that patterns of CMV infection in the North East of Scotland followed well-established norms. Data from other Regional Transfusion Centres within the UK were also collected for comparison.

Detection of human cytomegalovirus in peripheral mononuclear cells and urine samples using PCR

Samples of peripheral blood lymphocytes from 105 different blood donors were investigated for the presence of human cytomegalovirus (HCMV) DNA using the polymerase chain reaction (PCR) with primers specific for the Pst I w fragment (IE region). Viral DNA sequences were detected in 53 samples, a fifth of which had been previously serotyped as HCMV negative. In the latter cases, Western blot analysis re-determined two out of three individuals that were resampled as seropositive. PCR could therefore be used to extend existing methods employed for the identification of HCMV infected blood samples prior to transfusion to individuals in high risk groups. In addition, the value of PCR as a diagnostic test was evaluated in a small pilot study by comparing the results obtained with urine samples from babies suffering congenital infection and from other high risk patients, with data obtained by isolation of infectious virus or through the detection of immediate early antigens in infected cultures. Data from this study indicated that PCR is at least as sensitive as the other methods used in HCMV diagnosis.

A multivariate analysis of risk factors for cytomegalovirus infection in liver-transplant recipients

Thirty-three consecutive liver-transplant recipients were prospectively studied over a 37-mo period for evidence of cytomegalovirus infection. Sixteen (48%) episodes of cytomegalovirus infection were identified; 9 were primary infections and 7 were recurrent infections. Beginning with patient 8, gamma-globulin prophylaxis was routinely administered to most patients. Twelve potential risk factors for cytomegalovirus infection were evaluated and included pretransplant cytomegalovirus serological status of donor and recipient; recipient's age, sex, race, and liver disease; number and type of blood products transfused; type and intensity of immunosuppression; and occurrence of rejection. The Cox proportional hazards model identified positive donor cytomegalovirus serology as the single most important risk factor for subsequent development of cytomegalovirus infection, regardless of recipient cytomegalovirus serological status. In addition, use of gamma-globulin prophylaxis seemed to be protective against the occurrence of disseminated cytomegalovirus disease.

Acquisition of cytomegalovirus infection: an update

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

Physical mapping of a genome of equine herpesvirus 2 (equine cytomegalovirus)

The genome of a low equine cell passage equine herpesvirus 2 was partially cloned and physical maps for the restriction endonucleases BamHI, EcoRI, HindIII, and SalI determined. The genome length was estimated to be 192 kilobase pairs (kbp) and no evidence of isomerization was found. Two separate repeat structures were detected: 18 kbp direct terminal repeats; and an unrelated second pair of short internal, indirect repeats at 0.20 and 0.75 map units. Such a genomic structure does not appear to have been reported amongst the herpesviruses--all the genomes that do not isomerize either have repeat structures only at the termini, or if present internally, have only direct repeats.

The use of ELISA and nonradioactive DNA hybridization assays for the detection of human cytomegalovirus

A hybridization assay using a biotinylated DNA probe was compared to both ELISA and direct isolation methods for detecting human cytomegalovirus (HCMV). The biotin labeled HCMV AD 169 HindIII-O-DNA fragment was used in a dot-blot assay to screen for the presence of HCMV in 186 urine specimens obtained from kidney transplant patients. The biotinylated HCMV HindIII-O probe could detect 3 log10 TCID50 units of HCMV. Urine specimens were also examined for the presence of HCMV by either ELISA or direct isolation of virus in tissue culture. The HindIII-O fragment detected 12 of 20 culture positive samples (sensitivity, 60%). There were 5 samples which were probe positive and cell culture negative (specificity, 97%). The ELISA assay also detected 12 of 20 culture positive samples (sensitivity, 60%). Eight samples were ELISA positive, cell culture negative (specificity, 95%). Seven specimens were positive by all three criteria. Five specimens which were both ELISA positive and probe positive were cell culture negative. The ELISA positive, probe positive, culture negative specimens originated from patients who gave a culture positive specimen within 10 days of the original sample. The combination of probe and ELISA assays detected 16 of the 20 culture positive specimens (sensitivity, 80%). The combined use of biotinylated DNA probes and ELISA allows the detection of HCMV in urine specimens with good sensitivity and specificity.

Prevention of CMV infection by screening for CMV antibodies in renal allograft recipients and their blood and kidney donors

The influence of the cytomegalovirus (CMV) serostatus of blood and kidney donors on patient and graft survival was studied prospectively in 73 cadaveric renal graft recipients. Six out of 12 (50%) CMV seronegative recipients receiving a kidney from a CMV seropositive donor developed CMV disease, in contrast to none of 7 CMV seronegative donor/recipient combinations. Transmission of CMV with blood products to seronegative recipients was not observed in this study. A poor graft survival of 41% 3 years after transplantation was found in CMV seronegative recipients with CMV seropositive allograft donors, compared with an actuarial 3 year graft survival of 72% in the 7 CMV seronegative donor/recipient combinations. Six patients with graft failure had a CMV infection. This study, in accordance with other studies, suggests that selection of CMV seronegative renal allograft donors for CMV seronegative recipients will improve graft survival.

Rapid detection of infectious cytomegalovirus in blood with the aid of monoclonal antibodies

The recently developed early antigen immunofluorescence (IF) method for the detection of infectious cytomegalovirus (CMV) in clinical specimens has hardly been applied on blood samples. We compared the CMV early antigen detection technique with the conventional cell culture method in 415 different buffy coat samples from 85 different immunocompromised patients. Duplicate coverslips were stained with two different monoclonal antibodies 4-6 days after inoculation. The conventional cultures were examined for typical cytopathic effects (CPE) during 10 weeks. Forty samples from 19 patients were positive by the IF technique, most of them with both monoclonal antibodies. Only 22 of these samples were positive in the conventional cell culture assay, on average after 15.8 days. CMV viraemia was detected exclusively by the IF method in 18 samples, 7 of which were from five patients without any further evidence of an active CMV infection. CMV viraemia was detected exclusively by the CPE method in eight samples, on average after no less than 36.6 days. CMV viraemia was not found in blood samples from 10 patients with laboratory proven active CMV infections and 53 patients without any evidence of an active CMV infection. In our hands the early antigen method for the detection of infectious CMV in blood is nearly as specific (at least 98.1%) and clearly much faster and more sensitive than the conventional cell culture method. The early CMV antigen detection method is therefore a very useful tool for the rapid detection of infectious CMV in blood.

Transfusion-associated viral infections

Viral infections are a frequent occurrence following transfusion of blood products. While generally benign, these infections are capable of causing significant morbidity and mortality. Therefore, it is prudent to follow several general approaches diligently to reduce the risks of these infections in patients undergoing transfusions of blood products. These suggested measures include the following: 1. Prescribe and administer blood and blood products only when absolutely needed. 2. Use volunteer blood donors only. 3. Avoid use of pooled blood products when possible. 4. Use only blood and blood products that have been appropriately tested for HBsAg and HIV. 5. Use ALT determinations to screen blood products and eliminate those with high level. 6. Avoid the use of clotting-factor concentrates but, if necessary, use only those which have been heat-treated. 7. Limit use of leukocyte transfusion. 8. Use only CMV seronegative blood and blood products or frozen deglycerolized red cells in patients at high risk for posttransfusion CMV infection.

A test for human cytomegalovirus-specific immunoglobulins using a modification of a commercial test kit

A technique (Ig-EIA) for the detection of CMV-specific IgG, IgM and IgA in human blood is described. Ig-EIA utilizes alkaline phosphatase-labeled goat anti-human IgG, IgM and IgA as a detection probe and CMV antigen-coated solid phase from commercial kits. Ig-EIA is compared to indirect fluorescent assay (IFA) and indirect hemagglutination (IHA) for sensitivity and specificity. On sequential samples of blood from a set of patients, Ig-EIA clearly demonstrated seroconversion in CMV-specific IgG and IgM. A test of 332 blood donors by Ig-EIA showed 177 (53%) had CMV-specific IgG and 17 (5%) had CMV IgM. Only two of the 17 donors with CMV IgM were nonreactive for CMV-IgG. The potential of CMV-IgM as an indicator of CMV infectivity is discussed.

Molecular biology and immunology of cytomegalovirus

The application of modern biochemical techniques has led to a rapid improvement in our knowledge of the molecular biology of CMV. Several coding regions of the DNA genome have been identified with certainty and major virus-coded proteins have been given provisional names. The cascade expression of the CMV genome has been shown to be controlled by mechanisms similar to those found in other herpes viruses, together with novel post-transcriptional controls which remain to be defined. The control of CMV replication by the host involves both non-specific and specific defence mechanisms. The induction of natural killer cells and interferon early after CMV infection appears to be the most important aspects of the non-specific host defence against the virus. The cell-mediated immune response, in particular the generation of Tc cells against CMV early antigens, is probably the most important facet of the specific immune defence against CMV. When intact these defence mechanisms appear to be efficient in restricting viral replication; however, when such immunity is compromised, the balance rapidly swings in favour of the virus. As our understanding of the interaction between the host and the virus increases, it may be possible to redress the balance in such cases in favour of the host.

Rapid detection of cytomegalovirus in clinical specimens by using biotinylated DNA probes and analysis of cross-reactivity with herpes simplex virus

A method for rapid identification of human cytomegalovirus (HCMV) was developed with biotinylated DNA probes. BamHI restriction fragments from HCMV strain AD169 were selected and tested for their ability to detect virus in patient urine samples. All probes detected 30 pg of HCMV AD169 DNA. The BamHI B fragment detected 15 of 29 cell-culture-positive samples (sensitivity, 52%). There were four samples which were probe positive and cell culture negative (specificity, 87%). The D and H fragments used as combined probes detected 17 of 21 cell-culture-positive samples (sensitivity, 81%). There were five probe-positive and cell-culture-negative samples (specificity, 68.8%). The H fragment, when used alone, detected 11 of 14 culture-positive samples, and 5 samples were culture negative and probe positive. Sensitivity (78.6%) and specificity (76.2%) for the H fragment were similar to those for the combined probes, but the color intensity of the positive reactions detected by the H fragment alone was lower. There was unexpected cross-reactivity with herpes simplex type 1 and 2 controls when the combined D and H probes were used. Specific hybridization was demonstrated between subfragments of the HCMV BamHI D fragment and the herpes simplex virus type 1 EcoRI M fragment.

Cytomegalovirus immune globulin and seronegative blood products to prevent primary cytomegalovirus infection after marrow transplantation

In an attempt to prevent primary cytomegalovirus infection after marrow transplantation, we randomly assigned 97 patients who were seronegative for antibody to cytomegalovirus before transplantation to receive one of the following: (1) both intravenous cytomegalovirus immune globulin and seronegative blood products (23 patients); (2) seronegative blood products alone (28 patients); (3) globulin alone (22 patients); or (4) neither treatment (24 patients). Patients not assigned to receive seronegative blood products received unscreened blood products from random donors. The incidence of cytomegalovirus infection according to study group among patients in the study for at least 62 days was 5 percent, 13 percent, 24 percent, and 40 percent, respectively. Among 57 patients with seronegative marrow donors, those who received seronegative blood products had significantly less infection (1 of 32) than those who received standard blood products (8 of 25, P less than 0.007). In contrast, the use of seronegative blood products did not appear to prevent cytomegalovirus infection among patients with seropositive marrow donors. The possibility that cytomegalovirus immune globulin as used in this study can prevent cytomegalovirus infection or ameliorate cytomegalovirus disease was not confirmed, and it cannot be recommended for routine use without additional study.

Neonatal cytomegalovirus infections due to blood

Infants with very low birthweights (less than 1250g) are immunocompromised and have immature hematopoietic systems. They require frequent blood transfusions and have an increased susceptibility to infection. These very low birthweight infants who lack passively acquired antibody against CMV, acquire transfusion-associated CMV infections with a frequency of approximately 30%. These infections are associated with significant morbidity and mortality. The source of these postnatally acquired CMV infections are seropositive blood donors. These infections can be prevented by appropriate donor selection and/or blood processing. Recent but limited data suggests that all infants (regardless of birthweight or the presence of antibody against CMV) should receive CMV seronegative blood products if they are likely to receive multiple transfusions from multiple donors.

Detection of human cytomegalovirus in peripheral blood lymphocytes in a natural infection

In situ hybridization was used to detect human cytomegalovirus (HCMV) in the peripheral blood mononuclear cells of some naturally infected (seropositive) individuals. A subpopulation of cells hybridized specifically to a portion of the HCMV genome that is heavily transcribed during the immediate-early period of infection. The hybridization signal was markedly reduced by base hydrolysis and ribonuclease, and therefore the probe appears to be detecting viral RNA. A fluorescence-activated cell sorter was used to select lymphocytes bearing the OKT4 and OKT8 markers. Hybridization with the HCMV probe revealed a higher proportion of positive cells in the OKT4 than in the OKT8 subset. This observation specifically identifies lymphocytes as a cell population involved in natural HCMV infection and suggests that lymphocytes may be a reservoir for maintaining infection and may also serve as a vehicle for its spread by blood transfusion.

Quantitative and qualitative detection of cytomegalovirus-specific antibodies using two types of enzyme-linked immunosorbent assay

An indirect ELISA and an inhibition ELISA were developed for the detection of cytomegalovirus (CMV)-specific immunoglobulin G (IgG) and CMV-specific total immunoglobulin, respectively. Both assays were more specific than the complement fixation (CF) test, and titres of positive sera were 660 times higher by IgG ELISA and 6 times higher by inhibition ELISA than titres by the CF test. Titres by IgG ELISA were reliably determined using the absorbance obtained at a single serum dilution of 1/1,000 in conjunction with a standard graph. Both ELISAs compared favourably with each other in sensitivity and specificity in determining CMV immune status. The inhibition ELISA, in particular, provides a simple and reliable method of screening sera, which requires no control antigen or predilution of sera. It should prove useful for large-scale screening procedures, such as blood donor testing.

Incidences of antibodies to hepatitis B, herpes simplex and cytomegalovirus in prostitutes

The 170 prostitutes registered by the local public health authority (165 female, 5 male; ages 17-61) were serologically investigated by ELISA and CFT for the presence of hepatitis B virus (HBV) markers (n = 170), anti-CMV (n = 118) and anti-HSV 2 antibodies (n = 117). 4.7% (1.2%) were found to be HBs- (HBe-)antigen carriers; 1.2% revealed an acute hepatitis B (seroconversion of anti-HBc or IgM-anti-HBc highly positive); 17.1% presented a past and resolved hepatitis B (anti-HBs positive). These rates exceeded those of 125 female age-matched control persons considerably, out of whom only 2.4% (0.8%) presented HBs-(HBe-) antigen and 3.2% anti-HBs antibodies. 90% of the prostitutes investigated proved to be anti-CMV IgG (1.7% IgM) antibody positive and were compared to healthy blood donors (47% IgG, 0% IgM-anti-CMV antibody carriers) and other CMV risk groups: pregnant women 56 (13), patients in hemodialysis 61 (0), hemophiliac patients 69 (0), patients after kidney transplantation 90 (16) and after open-heart surgery 87 (4) % anti-CMV IgG (IgM) antibody carriers. An AIDS patient suffered from simultaneous HBV and CMV infections. The risk of HSV 2 infection is among prostitutes (38.5% seropositives) five times as high as among female age-matched control persons (7.2% seropositives, n = 125). These results confirm that prostitutes must be regarded as a risk for the spread of hepatitis BV and CMV- and HSV 2-caused diseases in the population.