Rapid detection of cytomegalovirus in cell culture by indirect immunoperoxidase staining with monoclonal antibody to an early nuclear antigen

Novel microneutralization assay for HCMV using automated data collection and analysis

In addition to being sensitive and specific, an assay for the assessment of neutralizing antibody activity from clinical trial samples must be amenable to automation for use in high-volume screening. To that effect, we developed a 96-well microplate assay for the measurement of HCMV-neutralizing activity in human sera using the HCMV-permissive human cell line HEL-299 and the laboratory strain of HCMV AD169. The degree to which neutralizing antibodies diminish HCMV infection of cells in the assay is determined by quantifying the nuclei of infected cells based on expression of the 72 kDa IE1 viral protein. Nuclear IE1 is visualized using a highly sensitive immunoperoxidase staining and the stained nuclei are counted using an automated ELISPOT analyzer. The use of Half Area 96-well microplates, with wells in which the surface area of the well bottom is half the area of a standard 96-well microplate plate, improves signal detection compared with standard microplates and economizes on the usage of indicator cells, virus, and reagents. The staining process was also streamlined by using a microplate washer and data analysis was simplified and accelerated by employing a software program that automatically plots neutralization curves and determines NT₅₀ values using 4-PL curve fitting.

The optimized assay is not only fast and convenient, but also specific, sensitive, precise and reproducible and thus has the characteristics necessary for use in measuring HCMV-neutralizing activity in the sera of vaccine trial subjects such as the recipients of Vical's HCMV pDNA vaccine candidates.

Low-dose short-course intravenous ganciclovir as pre-emptive therapy for CMV viremia post allo-PBSC transplantation

In contrast to allogeneic bone marrow transplantation (allo-BMT), there is a paucity of data on cytomegalovirus (CMV) infection and preemptive therapy (PT) strategies following allogeneic peripheral blood stem cell (allo-PBSC) transplantation. We report here on the patterns of CMV infection in a cohort of 225 patients following sibling donor allo-PBSC transplantation. In an attempt to reduce neutropenia, we used intravenous low-dose short-course (LDSC) ganciclovir (GCV) 5 mg/kg once daily for 21 days as preemptive therapy. A total of 165 recipient-donor pairs were CMV seropositive. An initial episode of viremia (detected by shell vial/tube culture) occurred in 75/165 (45%) at a median of day +35 (17-445) post allo-PBSC. In all, 58 patients received PT with LDSC GCV. Among 58, 55 (94%) completed the 21-day course of PT. A second episode of viremia occurred in 19/58 (33%) at day+80 (50-174) and a third episode in 5/58 (9%) at day+134 (103-218). Among patients receiving LDSC GCV, 5/58(9%) developed disease (four pneumonia, one colitis) at day+211 (63-487). No patient on LDSC GCV exhibited a decline in their ANC below 500/microl and none required growth factors. LDSC GCV is extremely well tolerated and cost-effective as PT for CMV viremia following allo-PBSC transplantation.

A rapid immune plaque assay for the detection of Hendra and Nipah viruses and anti-virus antibodies

Rapid immune plaque assays have been developed to quantify biohazard level 4 agents Hendra and Nipah viruses and detect neutralising antibodies to both viruses. The methods rely on the fact that both viruses rapidly generate large syncytia in monolayers of Vero cells within 24 h and that monospecific antiserum to the Hendra virus phosphoprotein (P) detects that protein in both Hendra and Nipah virus-induced syncytia after methanol fixation of virus-infected cells. The P protein is a constituent of the ribonucleoprotein core of the viruses and a component of the viral RNA-dependent RNA polymerase and is made in significant amounts in infected cells. In the immune plaque assay, anti-P antibody is localised by an alkaline phosphatase-linked second antibody and the Western blot substrates 5-bromo-4-chloro-3-indolyl phosphate and p-nitro blue tetrazolium. A modification of the rapid immune plaque assay was also used to detect antibodies to Nipah virus in a panel of porcine field sera from Malaysia and the results showed good agreement between the immune plaque assay and a traditional serum neutralisation test. After methanol fixation, plates can be stored for up to 7 months and may be used in the immune plaque assay to complement the enzyme-linked immunosorbent assay screening of sera for antibodies to Nipah virus. At present, all enzyme-linked immunosorbent assay positive sera are subject to confirmatory serum neutralisation tests. Use of the immune plaque assay may reduce the number of sera requiring confirmatory neutralisation testing for Nipah virus antibodies under biohazard level 4 conditions by identifying those that generate false positive in the enzyme-linked immunosorbent assay.

Development of a real-time PCR procedure including an internal control for the measurement of HCMV viral load

Human cytomegalovirus (HCMV) infections are frequent in immuno-compromised patients. The recent development of real-time PCR procedures that allow the rapid quantification of genome load will be helpful for accurate monitoring of these infections. Two extraction procedures were evaluated using 30 blood samples that were processed pure and diluted (1/10). Repeatability and reproducibility of the quantitative PCR procedure using an internal control for amplification were analysed, and its sensitivity compared to a qualitative PCR procedure using 50 HCMV culture positive blood samples. The real-time PCR and qualitative PCR procedures were positive in 46 and 48 of the samples tested, respectively. Discrepancies were observed for samples with a low viral load. The sensitivity of the real-time PCR procedure was evaluated at 500 HCMV DNA copies per ml of sera. The use of an internal control concomitantly processed during the HCMV quantification did not alter the sensitivity of the procedure, and was relevant for the detection of putative PCR inhibitors that may interfere with the amplification process. This procedure was used to measure genome load in two bone marrow transplant patients with HCMV disease, confirming that this new PCR procedure should be used widely for diagnosing and monitoring HCMV infections in transplant patients.

Real-time automated PCR for early diagnosis and monitoring of cytomegalovirus infection after bone marrow transplantation

The purpose of this study was to assess the usefulness of real-time automated PCR as a quantitative, highly reproducible, and sensitive method to detect cytomegalovirus (CMV) DNA in blood specimens. Intra- and interassay precision rates were 0.89% (small number of copies [L]), 1.43% (middle number of copies [M]), and 1.12% (high number of copies [H]), and 4.46% (L), 1.51% (M), and 2.28% (H), respectively. The linearity of this assay was obtained between 10 and 10(7) copies/well, with a minimum detection limit of 20 copies/well. Specimens from 55 of 70 healthy subjects were found to be positive for CMV antibody, but CMV DNA was not detected in any of them. In the qualitative assessment of each specimen, the results of the CMV antigenemia assay and those of the real-time PCR assay agreed in 80% (plasma specimens), 79% (all nucleated cells), and 86% (blood) of the cases examined. For eight patients diagnosed as having CMV infection or disease, no sample was positive in the antigenemia assay earlier than in the real-time PCR assay. Furthermore, the results of this assay could be obtained within 8 h. We concluded that the real-time PCR assay is useful for rapid diagnosis of CMV infection and monitoring of clinical courses.

Detection of cytomegalovirus in semen from a population of men seeking infertility evaluation

OBJECTIVE

To determine the incidence of cytomegalovirus in the ejaculates of infertile men who were seropositive for IgG antibodies to cytomegalovirus.

DESIGN

Prospective study.

PATIENT(S)

We tested cytomegalovirus infection in the semen of men participating in an IVF-ET program.

MAIN OUTCOME MEASURE(S)

IgG and IgM antibodies to cytomegalovirus were measured in sera. We used polymerase chain reaction (PCR) and cell culture to look for both cytomegalovirus DNA and infectious virus in the semen of 70 men with cytomegalovirus-specific antibodies detected in sera.

RESULT(S)

Of the infertile couples, 13.5% exhibited "mismatching" serology (i.e., detection of IgG antibodies to cytomegalovirus in male serum only and not in female serum) and constituted a potential risk for cytomegalovirus transmission. Cytomegalovrius was identified in the semen of two patients who were positive for IgG antibodies to cytomegalovirus. Cytomegalovirus DNA also was detected in one positive sample after centrifugation through a three-layer Percoll gradient.

CONCLUSION(S)

Human cytomegalovirus was present in the semen from a population of infertile men. Rapid detection can be achieved by molecular techniques such as PCR combined with a hybridization assay. Even though cytomegalovirus was infrequently detected in semen, these data must be considered in determining the risk of transmission and developmental anomalies in infected fetuses.

Evaluation and comparison of PCR and hybridization methods for rapid detection of cytomegalovirus in clinical samples

Rapid diagnosis of cytomegalovirus (CMV) infection may be obtained by molecular techniques, such as the polymerase chain reaction (PCR) and hybridization assays. The optimal technique to detect CMV in clinical samples was assessed. Two different PCR assays were used, targeting either the major immediate early 1 (MIE 1) or the HXLF 4 gene. The PCR products were detected by gel electrophoresis, dot blotting and an easy to use, rapid, solid phase hybridization assay, DNA enzyme immunoassay (DEIA). Standard tissue culture was also used. Cerebrospinal fluids (18), liver biopsies (9) from hepatic transplant recipients, amniotic fluids (7) from mothers with suspected peripartum infection, and samples (6) of miscellaneous origin (brain and fundus biopsy, pericardial and pleural fluid) were tested. Among the 40 samples, CMV was detected in 19 cases. Three were positive by both molecular techniques and tissue culture, 14 by molecular methods and 2 by culture. 16/19 or 9/19 CMV-positive samples were detected by PCR amplification of the HXLF 4 or MIE 1 gene, respectively and 14/16 HXLF 4-positive samples were detected using either dot-blot or DEIA, compared to 9/16 using gel electrophoresis. Thus, the most sensitive assays for the detection of CMV in clinical samples using the methods compared in the current study were PCR amplification of the HXLF 4 gene followed by dot-blot or DEIA hybridization.

Congenital cytomegalovirus infection

OBJECTIVE

Congenital cytomegalovirus is the most common viral infection affecting approximately 1% of newborns. The virus can be transmitted to the fetus during both primary and recurrent infection. Although most of the infants are asymptomatic at birth, up to 15% develop late complications. The annual cost of treating cytomegalovirus infection complications in the USA is two billion US dollars. Many issues regarding cytomegalovirus infection such as routine screening, antenatal diagnosis and vaccination during pregnancy are unsettled and disputed. The aim of this article is to review the current literature on the subject and to draw some conclusions.

DESIGN

Review of the current literature.

CONCLUSIONS

At present, it appears that there is no indication for routine prenatal screening, while other issues, such as the most accurate method for antenatal diagnosis and the indications for pregnancy termination are, as yet, unsettled.

Viral infections in severely immunocompromised cancer patients

Immunocompromised cancer patients are susceptible to infection by many viral pathogens. The most serious morbidity results from active infection by members of the herpes virus family. Reactivation of latent virus occurs as a sequela of cytotoxic therapy and deficiency of cell-mediated immunity, especially cytotoxic responses, the major host protective defense. Herpes simplex virus and varicella zoster virus infections are problematic in patients with all types of cancer; cytomegalovirus infections cause life-threatening morbidity in bone marrow transplant patients. Several antiviral agents are highly active against these pathogens and different strategies of using them have resulted in reduced morbidity and mortality. Ultimately, the resolution of these infections is dependent on the control of the malignancy and the ability of the patient to mount an adequate immune response.

Critical care issues in the patient with hematologic malignancy

Patients with lymphomas, multiple myeloma, and leukemia are often at risk for life-threatening complications. Complications include viral infections (eg, herpes zoster, herpes simplex, cytomegalovirus) and hemolytic anemia, which are related to the hematologic origin of the malignancy. Life-threatening disorders related to amount of tumor burden are leukostasis and hyperviscosity. Complications related to therapy include pulmonary capillary leak syndrome and tumor lysis syndrome. Good assessment skills assist in early identification of individuals at risk and initiation of preventive measures.

CD13 (human aminopeptidase N) mediates human cytomegalovirus infection

Human cytomegalovirus (HCMV) infects cells by a series of processes including attachment, penetration via fusion of the envelope with the plasma membrane, and transport of the viral DNA to the nucleus. The details of the early events of HCMV infection are poorly understood. We have recently reported that CD13, human aminopeptidase N, a metalloprotease, is present on blood cells susceptible in vitro to HCMV infection (C. Söderberg, S. Larsson, S. Bergstedt-Lindqvist, and E. Möller, J. Virol. 67:3166-3175, 1993). Here we report that human CD13 is involved in HCMV infection. Antibodies directed against human CD13 not only inhibit infection but also block binding of HCMV virions to susceptible cells. Compounds known to inhibit aminopeptidase activity block HCMV infection. HCMV-resistant murine fibroblasts have heightened susceptibility to HCMV infection after transfection with complementary DNA encoding human CD13. A significant increase in binding of HCMV was observed in the CD13-expressing transfectants compared with neomycin-resistant control mouse cells. However, murine fibroblasts transfected with mutant CD13, lacking a portion of the aminopeptidase active site, remained susceptible to HCMV infection. Thus, human CD13 appears to mediate HCMV infection by a process that increases binding, but its enzymatic domain is not necessary for infection.

Physical and chemical methods for enhancing rapid detection of viruses and other agents

Viral replication events can be enhanced by physical, chemical, or heat treatment of cells. The centrifugation of cells can stimulate them to proliferate, reduce their generation times, and activate gene expression. Human endothelial cells can be activated to release cyclo-oxygenase metabolites after rocking for 5 min, and mechanical stress can stimulate endothelial cells to proliferate. Centrifugation of virus-infected cultures can increase cytopathic effects (CPE), enhance the number of infected cells, increase viral yields, and reduce viral detection times and may increase viral isolation rates. The rolling of virus-infected cells also has an effect similar to that of centrifugation. The continuous rolling of virus-infected cultures at < or = 2.0 rpm can enhance enterovirus, rhinovirus, reovirus, rotavirus, paramyxovirus, herpesvirus, and vaccinia virus CPE or yields or both. For some viruses, the continuous rolling of infected cell cultures at 96 rpm (1.9 x g) is superior to rolling at 2.0 rpm for viral replication or CPE production. In addition to centrifugation and rolling, the treatment of cells with chemicals or heat can also enhance viral yields or CPE. For example, the treatment of virus-infected cells with dimethyl sulfoxide can enhance viral transformation, increase plaque numbers and plaque size, increase the number of cells producing antigens, and increase viral yields. The infectivity of fowl plague virus is increased by 80-fold when 4% dimethyl sulfoxide is added to culture medium immediately after infection. The heat shocking of virus-infected cells also has been shown to have a stimulatory effect on the replication events of cytomegalovirus, Epstein-Barr virus, and human immunodeficiency virus. The effects of motion, chemicals, or heat treatments on viral replication are not well understood. These treatments apparently activate cells to make them more permissive to viral infection and viral replication. Perhaps heat shock proteins or stress proteins are a common factor for this enhancement phenomenon. The utility of these treatments alone or in combination with other methods for enhancing viral isolation and replication in a diagnostic setting needs further investigation.

Pretransplant pulmonary function predicts cytomegalovirus-associated interstitial pneumonia following bone marrow transplantation

STUDY OBJECTIVE

To determine the value of pulmonary function tests (PFTs) in predicting the development of human cytomegalovirus (CMV)-associated interstitial pneumonia (IP) in allogeneic bone marrow transplant (BMT) recipients.

DESIGN

Nonrandomized, prospective, open-trial study.

SETTING

Tertiary referral medical center.

PATIENTS

66 evaluable CMV-seropositive patients with hematologic malignancies who were undergoing allogeneic BMT.

INTERVENTION

FEV1, FVC, FEV1/FVC, TLC, Dcoc/VA, PaO2, and P(A-a)O2 were measured on days -13, +33, and +44 following BMT. CMV-IP was diagnosed when typical roentgenographic findings developed with confirmatory positive bronchoalveolar lavage (BAL) using standard cytologic and/or rapid culture techniques.

MEASUREMENT AND MAIN RESULTS

Univariate logistic regression analysis to predict the development of CMV-IP revealed significant associations with the day -13 and +33 percent predicted FEV1, FVC, and TLC (p < 0.01) but no associations with other PFT parameters or with changes in these parameters. Stepwise logistic regression analysis demonstrated that only BAL positivity for CMV (odds ratio 14.8; p = 0.0002) and day -13 percent predicted FEV1 (odds ratio 0.92; p = 0.0004) were significant independent predictors of CMV-IP.

CONCLUSION

Pretransplant lung function is a previously unrecognized strong predictor and risk factor for the subsequent development of CMV-IP in BMT recipients.

Improved detection of cytomegalovirus viremia in AIDS patients using shell vial and indirect immunoperoxidase methodologies

One hundred twelve peripheral blood specimens were tested for the presence of cytomegalovirus (CMV) by the tube culture indirect immunoperoxidase (TC-IPA) procedure, the shell vial assay [shell vials were pre- and postinoculation treated with medium containing 2 of 10% fetal bovine serum (FBS) or 100 micrograms% cortisol] (SV-IFA), and conventional (MRC-5) tube cultures (TC-CPE). CMV was detected in 25 (22%) of the 112 specimens tested by at least one of these methods. The detection/isolation of CMV among the 25 positive specimens in shell vials maintained with 2% FBS, 100 micrograms% cortisol + 2% FBS, and 10% FBS was 36, 44, and 52%, respectively. Detection/isolation of the virus from blood by TC-IPA and TC-CPE was 52% and 76%, respectively. A significantly greater CMV detection rate occurred using TC-CPE compared to SV-IFA treated with medium supplemented with an FBS concentration of 2% (P = .0132), but not medium containing the higher serum supplement or the glucocorticoid (P greater than .05). Differences in the identification of a CMV viremia were observed by IPA, SV-IFA, and TC-CPE methodologies on a patient-to-patient basis, denoting the necessity of incorporating each methodology into the CMV screening panel. Demographic analysis of 82 AIDS patients showed a CMV viremia prevalence of 9% (2/28) in intravenous drug users, 57% (27/47) in homosexual patients, and 22% (2/9) in heterosexual and transfusion patients. Overnight (24 hr) storage of whole blood at 4 or 24 degrees C, respectively, reduced CMV recovery by 40% and 65%, when tested by TC-CPE.(ABSTRACT TRUNCATED AT 250 WORDS)

Rapid diagnosis of cytomegalovirus infections by direct immunoperoxidase staining with human monoclonal antibody against an immediate-early antigen

Direct immunoperoxidase technique using a horseradish peroxidase (HRP)-conjugated Fab' fragment of human monoclonal antibody (humab C7), designated HRP-C7, was evaluated as a rapid diagnosis of cytomegalovirus (CMV) infection. A total of 138 clinical specimens consisting of 124 urine samples and 14 oral swabs were examined for CMV by the direct HRP-C7 staining in comparison with conventional virus isolation. The number of CMV-positive samples by each method was 40 (29.0%) for the former and 37 (26.8%) for the latter, respectively. By HRP-C7 staining, CMV was identifiable within 24 hr after inoculation. By conventional isolation method, an average of 10.3 days had passed before cytopathic effect characteristic of CMV appeared in the cell culture. Some false-positive and false-negative cases were discussed in relation to toxicity of urine samples, storage of the samples, and amount of CMV in the sample. The sensitivity and specificity of HRP-C7 method against conventional isolation method were 89.2% and 93.1%, respectively. Thus, HRP-C7 staining is useful for a rapid diagnosis of CMV infections.

Deteccion de citomegalovirus mediante la tecnica de inmunoperoxidasa y aislamiento viral

En el presente estudio se comparó la técnica de inmunoperoxidasa para la detección de citomegalovirus (IPCMV) utilizando anticuerpos monoclonales que reconocen proteínas precoces virales con el método convencional de aislamiento viral en fibroblastos humanos. Un total de 150 muestras de orina fueron examinadas encontrando una sensibilidad de un 89.8% y una especificidad de 91.3% de la técnica de IPCMV comparada con el aislamiento viral. Una de las ventajas que presentó la IPCMV fue la rapidez con que fueron obtenidos los resultados (48 horas) mientras que el aislamiento viral fue como promedio 14 días.

A randomized, controlled trial of prophylactic ganciclovir for cytomegalovirus pulmonary infection in recipients of allogeneic bone marrow transplants; The City of Hope-Stanford-Syntex CMV Study Group

BACKGROUND

Cytomegalovirus (CMV)-associated interstitial pneumonia is a major cause of death after allogeneic bone marrow transplantation. We conducted a controlled trial of ganciclovir in recipients of bone marrow transplants who had asymptomatic pulmonary CMV infection. We also sought to identify risk factors for the development of CMV interstitial pneumonia.

METHODS

After bone marrow transplantation, 104 patients who had no evidence of respiratory disease underwent routine bronchoalveolar lavage on day 35. The 40 patients who had positive cultures for CMV were randomly assigned to either prophylactic ganciclovir or observation alone. Ganciclovir (5 mg per kilogram of body weight intravenously) was given twice daily for two weeks and then five times per week until day 120.

RESULTS

Of the 20 culture-positive patients who received prophylactic ganciclovir, 5 (25 percent) died or had CMV pneumonia before day 120, as compared with 14 of the 20 culture-positive control patients (70 percent) who were not treated prophylactically (relative risk, 0.36; P = 0.01). No patient who received the full course of ganciclovir prophylaxis went on to have CMV interstitial pneumonia. Four patients treated with ganciclovir had maximal serum creatinine levels greater than or equal to 221 mumol per liter (2.5 mg per deciliter), as compared with none of the controls (P = 0.029). Of the 55 CMV-negative patients who could be evaluated, 12 (22 percent) had CMV pneumonia--a significantly lower rate than in the untreated CMV-positive control patients (relative risk, 0.33; P = 0.003). The strongest predictors of CMV pneumonia were a lavage-fluid culture that was positive for CMV and a CMV-positive blood culture, both from specimens obtained on day 35.

CONCLUSION

In recipients of allogeneic bone marrow, asymptomatic CMV infection of the lung is a major risk factor for subsequent CMV interstitial pneumonia. Prophylactic ganciclovir is effective in preventing the development of CMV interstitial pneumonia in patients with asymptomatic infection.

Generation and application of a monoclonal antibody raised against a recombinant cytomegalovirus-specific polypeptide

Procedures for diagnostics of cytomegalovirus infections include histopathology, cell culture, serology, and direct detection of viral antigens or nucleic acids within infected cells or tissues. In order to develop a new diagnostic reagent for viral antigen detection, we generated a mouse monoclonal antibody. This antibody was raised against a recombinant antigen representing part of the large phosphorylated structural protein pp150 of human cytomegalovirus. The monoclonal antibody was shown to be useful for antigen detection by immunofluorescence and immunoenzymatic staining in infected cells from cell culture as well as from infected organs. The antibody proved to be reactive even in paraffin-embedded sections from tissue specimens.

Production of human monoclonal IgG antibodies reacting with cytomegalovirus (CMV)

A human monoclonal antibody (MoAb) reacting with cytomegalovirus (CMV) has been produced using somatic cell hybridization between Epstein-Barr virus (EBV) infected B lymphocytes and a human-mouse heteromyeloma cell line (SHM-D33). The hybrids were selected in HAT medium containing 5 x 10(-7) ouabain. The median level of Ig production was 5 (0.1-20) micrograms/10(6) cells/day. One selected hybridoma (IB-8E9H5) has been maintained in continuous culture for more than 30 months with a stable IgG2, lambda production. Molecular hybridization using EBV-specific probes demonstrate that our hybrids have lost the IR-1 EBV sequence during fusion. Unexpectedly, these blotting experiments revealed the presence of multiple EBNA-1 sequences dispersed among the genomic DNA of the SHM-D33 cell line. Screening for anti-CMV specificity was performed by ELISA and confirmed by immunofluorescence staining. Thus far, three CMV reference strains and 14 local strains are stained by the MoAb as early as 3 h after CMV infection of human fibroblasts, apparently through the recognition of a nuclear viral antigen of 67 kDa. In conclusion, this technique permits (a) the removal of the EBV genome contained in the lymphoblastoid parental cell line and (b) the production of human anti-CMV MoAb with potential applications in the prevention of life threatening CMV infections.

Early detection of cytomegalovirus in cell culture by a new monoclonal antibody, CCH2

A CMV monoclonal antibody, CCH2, produced in this laboratory was evaluated for rapid detection of CMV. Two staining procedures, immunofluorescence and an immunoenzymatic technique using biotin-streptavidin peroxidase, were compared. The CCH2 monoclonal antibody was used to demonstrate early CMV antigen in cell culture 24 h after inoculation of 598 urine samples from kidney transplanted patients by indirect immunofluorescence in comparison with virus isolation. One hundred and sixty of the specimens were stained additionally by an immunoenzymatic technique and the results were compared. CMV was isolated from 170 out of 598 specimens within 6 weeks. Early CMV antigen was demonstrated in 114 of these specimens by immunofluorescence giving a sensitivity of 67% and a specificity of 95%. In the comparison with the immunoenzymatic staining procedure the results for all three tests agreed for 81% (130/160) of the specimens. After resolving discordant results into true positives and true negatives, the sensitivity was 87, 85 and 70%, respectively for virus isolation, immunoenzymatic staining and immunofluorescence and the specificity 100, 96 and 99%. The CCH2 monoclonal antibody proved to be useful for rapid detection of CMV in urine specimens and using immunoenzymatic staining with biotin-streptavidin a sensitivity comparable to that of virus isolation was found.

An improved immunocytochemical method for the detection of human cytomegalovirus antigens in peripheral blood leucocytes

A recently described immunoperoxidase method for the detection of nuclear human cytomegalovirus (HCMV) immediate early antigen (IEA) directly on peripheral blood leucocytes suffers from the drawback that the antigen is vulnerable to endogenous peroxidase inactivation procedures. To solve this problem a procedure is developed in which endogenous peroxidase is inactivated after binding and immobilization of the primary antibody with 4% formaldehyde. In combination with this procedure, three types of inactivation were investigated: glucose/glucose oxidase, hydrochloric acid and methanol/H2O2. Of these three, the first gives optimal results, especially in combination with methanol/acetic acid (20/1 v/v) as the primary fixative. This procedure results in preparations which allow for a more objective evaluation and enable automated examination using bright field microscopy. As a second improvement we developed a simple adherence method in order to diminish the risk of infection for the laboratory staff during processing of unknown blood samples. The protocol described shows great clinical potential for the diagnosis of HCMV infections.

Comparison of in situ hybridization and monoclonal antibodies for early detection of cytomegalovirus in cell culture

The abilities of each of four diagnostic tests--direct fluorescent monoclonal antibody (direct FA) staining, indirect fluorescent monoclonal antibody (indirect FA) staining, in situ hybridization with biotinylated DNA probes, and in situ hybridization with DNA probes directly linked to enzymatically active horseradish peroxidase-to detect cytomegalovirus soon after culture were compared. Only the indirect FA test and the in situ hybridization method with directly linked HRP-DNA probes provided consistent and reliable cytomegalovirus detection as early as 15 h postinfection.

Applications of immunogold-silver enhancement: testing of monoclonal antibodies and detection of human cytomegalovirus in histologic specimens

Human cytomegalovirus (HCMV) is an important pathogen in neonates, transplant patients, and individuals with acquired immunodeficiency syndrome (AIDS). Reliable techniques for the detection of this virus in clinical specimens would aid in improving methods for diagnosis and increasing our understanding of viral pathogenesis. We evaluated the utility of immunogold-silver enhancement to determine the specificity of murine monoclonal antibodies directed against HCMV proteins and applied these antibodies to the detection of HCMV in histologic material. Nine antibodies were tested in a tissue-culture system to determine the location of staining. All were found to be active in frozen tissue, but only two of these antibodies were reactive in formalin-fixed tissue. We also evaluated a novel tissue fixative technique (AMeX; Fixation and dehydration with acetone) that has been used to maintain antigenicity of T-lymphocyte cell markers. All antibodies remained reactive against their respective HCMV proteins in tissue fixed by this technique. However, dehydration of tissue may limit the usefulness of AMeX fixation. Immunogold-silver enhancement is a useful and reliable histochemical technique for detection of HCMV antigens in pathologic specimens.

Cytomegalovirus detection by biotinylated DNA probes

Clinical specimens from 317 patients suspected of cytomegalovirus infection were examined by immunofluorescence (IF) using monoclonal antibodies and by a biotinylated DNA probe kit after cell culture isolation. Of the 317 samples, 68 were positive by culture isolation. Of these 67 were IF positive when the cytopathic effect (CPE) was 1+ or less, whereas 56 gave positive results with DNA probes when the CPE was 2+. A further 83 specimens were examined directly by immunoperoxidase histopathology (IHP), IF and the DNA probe kit: 26 of these were positive by IHP examination, 25 by IF and only 6 by DNA probes. The sensitivity of the DNA probe kit was not satisfactory when the clinical tissue specimens were directly examined. However, the sensitivity improved considerably to 82% if the specimens were propagated first in cell culture. The IF method detected the virus before and after cell culture isolation equally well (96%-98.5%). Compared to the IF method, the DNA probe kit is costly and requires more labor and time.

Detection of cytomegalovirus in bronchial lavage and urine using a monoclonal antibody to an HCMV early nuclear protein

Laboratory diagnosis of 24 cases of human cytomegalovirus (HCMV) infection in patients with the acquired immunodeficiency syndrome, renal transplant recipients and premature infants was achieved. These results were obtained by a rapid, sensitive and versatile HCMV-antigen detection method, which combined cell culture and immunoperoxidase staining with a monoclonal antibody to an HCMV "early" nuclear protein. The results were compared with HCMV isolation by the conventional cell culture method. While some of these immunocompromised patients lacked a significant antibody response, infective HCMV could be detected in the patients' urine and bronchial lavage fluid. The diagnostic procedure took no longer than 24 h. The usefulness of this antigen test for an effective diagnosis in immunocompromised individuals was demonstrated. We recommend routine analysis of various specimens, since recent developments in chemotherapy of HCMV infection and the risks of long-term damage demand immediate management of the patients concerned.

Detection of cytomegalovirus in shell vial cultures by using a DNA probe and early nuclear antigen monoclonal antibody

An in situ biotinylated DNA probe assay was evaluated as an adjunct to anti-cytomegalovirus early nuclear antigen indirect immunofluorescence and cytopathic effect on cytomegalovirus-infected monolayers in shell vial cultures. Viral infection was detected by early nuclear antigen indirect immunofluorescence at 24 h and by DNA probe assay and shell vial cytopathic effect at 5 days.

Immunological detection of cytomegalovirus early antigen on monolayers inoculated with urine specimens by centrifugation and cultured for 6 days as alternative to conventional virus isolation

Detection methods for human cytomegalovirus were evaluated with 431 urine samples from 30 bone marrow and 88 kidney transplant recipients. Low-speed centrifugal inoculation was followed by early antigen (EA) detection by means of indirect immunofluorescence with a monoclonal antibody after 1 (EA-1) and 6 (EA-6) days of cultivation. The results were compared with those of conventional virus isolation (CVI). Of 68 positive samples, 49 (72%) were detected with EA-1, 58 (85%) were detected with EA-6, and 43 (63%) were detected with CVI. The combination of EA-1 and EA-6 showed positive results with 66 samples (97%), which is significantly better than with CVI (P less than 0.001). With the exception of one patient, all CVI-negative but EA-positive samples had either significant rises in immunoglobulin G (IgG) or IgA antibody titer or IgM antibodies present in the sera. These data indicate that the method with EA detection can replace CVI, provided that each sample is inoculated in duplicate. Sample 1 is examined after 1 day, and if it is negative, sample 2 is incubated for a further 5 days, followed by detection of cytomegalovirus.

Correlation of cytomegalovirus (CMV) detection in urine by tissue culture virus isolation, early antigen immunofluorescence test and nucleic acid hybridization

The sensitivity and specificity of the early antigen immunofluorescence test and of the hybridization assay were compared with those of the development of a cytopathic effect on HF MA 23 cell monolayers in tissue culture. Of 818 clinical specimens tested, 125 specimens produced CMV cytopathic effect in tissue culture within four weeks after inoculation. Of the 125 specimens, 71 were positive for CMV after 36 h by early antigen immunofluorescence test (sensitivity 56.8%). Of the remaining 693 culture-negative specimens, seven were positive by early antigen immunofluorescence test (specificity, 99%). A hybridization assay using a commercial kit with the biotinylated Bam H I AB DNA fragment of HCMV Towne strain and horseradish peroxidase streptavidin conjugate, detected 60 pg of HCMV DNA. In this assay 104 urine specimens were tested. Compared with tissue culture, this hybridization assay had a sensitivity of 69.5%, a specificity of 60.3% and a correlation of 63.4%, at which 25 of 33 tissue culture positive samples had positive hybridization results, and 27 of 68 tissue culture negative samples also gave positive hybridization results. An additional hybridization assay, using the biotinylated Hind III L fragment of HCMV AD 169 and 125J streptavidin conjugate, detected 30 pg HCMV DNA. In 179 urine specimens simultaneously tested by tissue culture, 28 of 33 positive tissue culture specimens were positive in the hybridization assay. 37 of 146 negative tissue culture specimens gave positive hybridization signals (sensitivity 84.8%, specificity 74.7%, correlation 76.5%).

Rapid quantitation of cytomegalovirus and assay of neutralizing antibody by using monoclonal antibody to the major immediate-early viral protein

An overnight assay, based on staining cytomegalovirus-infected cells with monoclonal antibody to the 72,000-molecular-weight major immediate-early viral protein, was compared with a conventional 14-day plaque assay for quantitation of cell-free stocks of cytomegalovirus laboratory strain AD-169 and 20 other clinical strains. Viral titers were quantitatively similar when determined by either method, but centrifugation of monolayers during inoculation enhanced viral infectivity an average of 4.1-fold. When used for scoring neutralizing antibody assays, monoclonal antibody staining yielded titers within one dilution of 14-day plaque-reduction assays in 54 of 56 titrations. Of 21 cytomegalovirus strains, 2 were not recognized by the monoclonal antibody used. Assay with monoclonal antibody offers a rapid and accurate alternative to plaque assays for quantitation or neutralization of cytomegalovirus.

Detection of cytomegalovirus in clinical specimens by virus isolation and by a monoclonal antibody against the early nuclear antigen

A commercially available monoclonal antibody against the 72000 Dalton early nuclear protein (EA) of cytomegalovirus (CMV) strain AD169 was used in an indirect immunofluorescence staining procedure (IF) for rapid detection of CMV-infected cells in tissue cultures inoculated with clinical specimens (200 urines, 22 throat washings, 5 stools, 4 bronchoalveolar lavage fluids). The results obtained by this method were compared with those obtained by virus isolation with and without centrifugal enhancement of viral infectivity. In 66 (28.6%) of the 231 samples, CMV was detected by at least one of the methods used. Of 59 specimens producing CMV-specific cytopathic effect (CPE) in tissue culture, 46 (78%) were also positive in the EA test 16 hours after inoculation. Seven CPE-negative samples were, however, positive in the EA test. Five (38%) of the false negative EA test results were due to CMV strains that did not react with the monoclonal antibody used.

Comparison of two rapid culture methods for detection of cytomegalovirus in clinical specimens

The conventional virus isolation technique was compared with a 24-h shell vial centrifugation culture technique and with a 48-h tube culture method for the detection of cytomegalovirus (CMV) in MRC-5 cells. Of 200 clinical specimens tested, 41 were positive for CMV by at least one procedure. Indirect immunoperoxidase staining was positive for 32 (78.0%) of 41 specimens in the tube culture method and for 30 (73.2%) of 41 specimens in the shell vial centrifugation method. CMV was detected in 23 (56.1%) of 41 specimens by the development of cytopathic effect within 14 days.

Cytomegalovirus: epidemiology and infection control

Cytomegalovirus (CMV) causes asymptomatic infection in most individuals but can produce devastating illness in immunocompromised hosts and in a small proportion of congenitally infected babies. New techniques in molecular biology have provided insights into the epidemiology and transmission of CMV. Children in day care, their parents, and sexually active individuals, especially homosexual men, are now known to be at particular risk for acquiring CMV. Recent studies show that the risk of CMV acquisition by health care workers is similar to the risk to the general public. Health care workers should be aware of the wide range of clinical manifestations, methods of laboratory diagnosis, and current limitations of treatment of CMV. Careful handwashing and avoidance of excretions and secretions are recommended to decrease the transmission of CMV in the hospital.

Use of monoclonal antibodies for the diagnosis of cytomegalovirus infection by the detection of early antigen fluorescent foci (DEAFF) in cell culture

A pool of seven monoclonal antibodies, each reactive with cytomegalovirus (CMV) early antigens, was used in an indirect immunofluorescence method for the rapid detection of CMV-infected fibroblasts following inoculation with clinical specimens. A total of 1,639 specimens were examined, and the results were compared with those of conventional isolation procedures. The detection of CMV by early antigen fluorescent foci (DEAFF) was found to be comparable, both in terms of specificity and sensitivity, to that of conventional cell culture. Its great advantage, however, is the rapidity with which results are achieved. Thus, results were available from the DEAFF test within 24 hours of receipt of the specimens as compared to a mean of 16 days for cell culture. This single rapid assay for the detection of CMV in clinical samples may be performed by any laboratory familiar with cell culture techniques and in our hands is the preferred diagnostic method for CMV.

Sensitivity and specificity of enzyme immunofiltration and DNA hybridization for the detection of HCMV-infected cells

The sensitivity and specificity of enzyme immunofiltration and DNA hybridization were compared in human cytomegalovirus (HCMV) (AD 169)-infected MRC-5 cells. The enzyme immunofiltration was carried out on glass fiber filters in microplates, using an HCMV (AD 169) monoclonal antibody and a peroxidase conjugate. The DNA hybridization was carried out with a microfiltration apparatus, using a 32P-labelled HCMV (AD 169) Eco R1 D fragment probe. The sensitivities of enzyme immunofiltration and DNA hybridization were 1.82 X 10(3) and 1.13 X 10(3) infected cells, respectively. Both methods were highly specific, but enzyme immunofiltration was faster and simpler.

Early detection of cytomegalovirus in the allograft liver biopsy: a comparison of methods

Cytomegalovirus (CMV) hepatitis can be distinguished from allograft rejection only by biopsy. It is important to document CMV hepatitis early, before inclusions become visible, since antirejection therapy can aggravate the hepatitis. CMV was isolated from 50 patients, 9 of whom had a biopsy-proven CMV hepatitis that was preceded by an apparently uninfected biopsy within 3-33 days (mean = 18 days). A monoclonal antibody to an intermediate early CMV antigen (Chemicon) was compared with a commercially available CMV DNA-hybridization kit (ENZO) for their ability to demonstrate virus in the earlier, apparently uninfected biopsies. All of the biopsies with CMV hepatitis and 3 of the 9 preceding biopsies revealed CMV nuclear antigen in both transformed and nontransformed cells in paraffin-embedded tissues. DNA hybridization revealed viral DNA in the hepatitis biopsies but not in the preceding ones. Thus, in this study CMV was detectable by means of antibody before there was overt histologic evidence of CMV effect. The monoclonal antibody stain was more sensitive, less expensive, and easier to perform and interpret in this study than the DNA hybridization. Demonstration of early CMV antigen is more rapid and sensitive than culture of the liver specimen (which grew CMV in only 3 of 5 attempts) and should be considered in all allograft liver biopsies in which rejection is suspected.