Rapid detection and quantitation of human cytomegalovirus in urine through DNA hybridization

Detection of human cytomegalovirus by slot-blot hybridisation assay employing oligo-primed 32P-labelled probe

A 32P-labelled Hind III-0 DNA fragment (nine Kilobases; Kb) from human cytomegalovirus AD-169 (HCMV) was used in slot-blot hybridisation assay for the detection of HCMV in clinical samples. The results obtained with DNA hybridisation assay (DNA HA) were compared with virus isolation using conventional tube cell culture (CTC) and centrifugation vial culture (CVC), immunofluorescence (IF), and complement fixation test (CFT). Of 15 CTC-positive samples, 13 were positive with DNA HA (sensitivity 86.7%). Also, 14 additional samples were DNA HA-positive but CTC-negative. CVC and/or IF confirmed the diagnosis in nine of 14; the remaining five samples were from three patients who showed fourfold rising antibody titre by CFT. Although DNA HA using 32P-labelled probes is relatively cumbersome and expensive, it is a valuable test for quantitation of viral shedding in patients with HCMV infections who may benefit from antiviral therapy.

Detection of enteroviruses using subgenomic probes of Coxsackie virus B4 by hybridization

The objective of this research was to develop group- and type-specific probes for the detection of enteroviruses. Coxsackie virus B4 RNA was cloned, and a series of subgenomic clones were generated. Six of these clones, containing sequences from the 3' end or the 5' end of the genome, were tested for their ability to detect these viruses in a small number of infected cells employing nucleic acid hybridization technique and total cytoplasmic RNA from a panel of 11 serotypes of enteroviruses. The RNA from cells infected with Coxsackie B viruses gave characteristic and positive hybridization signals. Coxsackie B-specific probes and a control Echo 9 probe detected Coxsackie A9 and Echo 3 weakly. As little as 0.5 microgram of the RNA--which contained 10-20 ng of poly(A)-containing, virus-specific, hybridizable RNA--was sufficient to successfully conduct the assay, suggesting high sensitivity of these probes. Probes that are 3' end-specific appear to be group specific, while those that are 5' end-specific appear to be type specific among the serotypes tested.

DNA hybridization assay for congenital cytomegalovirus infection

An in vitro DNA hybridization assay was used to test 281 newborns for congenital infection with cytomegalovirus. The assay utilized an abbreviated method for DNA preparation and a dot blot assay that provided good sensitivity (100%) and specificity (98.9%) when compared with standard tissue culture, yet substantially reduced the total time of analysis. This assay would be a useful adjunct to tissue culture to diagnose newborns with congenital infection with cytomegalovirus.

Chronic cytomegalovirus infection

Cytomegalovirus infects about 60% of persons in developed countries and may cause significant disease in immunosuppressed patients. Serology has no role in the diagnosis of CMV disease in such patients yet detection of the virus in diseased parts of the body can be used to monitor the course of disease and antiviral measures. Detection of viral proteins (alpha or beta proteins) by monoclonal antibodies in cell cultures infected by urine, saliva or blood samples from patients allows a positive diagnosis within 24 h (DEAFF test). Monoclonal antibodies against CMV can also be used to stain cells obtained directly from the infected patients.

Detection of cytomegalovirus by dot-blot DNA hybridization using probes labelled with 32P by nick translation or random hexanucleotide priming

A DNA hybridization assay for the detection of human cytomegalovirus (HCMV) DNA was developed using random hexanucleotide-primed 32P-labelled Hind III restriction fragments of HCMV DNA as probes, and compared with a DNA hybridization assay using probes labelled with 32P by nick translation. Nick-translated probes were shown to be able to detect between 1 and 10 pg of homologous DNA or the DNA of 10-50 HCMV-infected fibroblasts. Random hexanucleotide-primed DNA probes lowered these detection limits to 0.1-0.5 pg of homologous DNA or one to five HCMV-infected fibroblasts. An increase in the autoradiographic exposure time from 18 h to 4 days increased the level of detection for homologous DNA or HCMV-infected fibroblast DNA by approximately five-fold. Preliminary screening of 35 urine samples by DNA hybridization using a random hexanucleotide-primed probe correctly identified three samples positive by virus isolation in tissue culture or immediate-early nuclear antigen detection and 29 of 32 samples negative by tissue culture.

Biotinylated and radioactive DNA probes for detection of varicella-zoster virus genome in infected human cells

We have developed and compared two DNA dot hybridization methodologies with similar probes (radioisotope-labelled and biotin-labelled) to detect varicella-zoster virus (VZV) DNA in three different cell cultures at varying times post-infection. Control cultures included uninfected monolayers of the same cells. Cellular DNA was isolated by a standard phenol extraction method, after which the DNA was quantified, serially diluted and blotted onto nitrocellulose or nylon membranes. The VZV DNA probe, which consisted of the large Hind III A fragment (27 of the total 125 kbp), was produced in two separate nick translation systems. The first contained 100 microCi [32P] and 0.4 microgram Hind III fragment A of the varicella genome, while the second probe employed a biotin-7-dATP analogue and 1.0 microgram of the Hind III fragment A. Direct visualization on the membrane or the exposed radiographic film showed a dot of varying intensity whenever viral genome was detected with either the biotin or the radioactive probe, respectively. With the [32P]-labelled probe, we detected VZV genomic sequences within 0.5 microgram total DNA at 12 h post-infection. This amount corresponded to approximately 5-10 pg of viral DNA. By comparison, hybridization with the biotin-labelled probe required 0.5-1.0 micrograms total DNA from infected cells. Similar tests on DNA extracted from uninfected cell samples were negative with both probes.

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.

Rapid detection of cytomegalovirus by fluorescent monoclonal antibody staining and in situ DNA hybridization in a dram vial cell culture system

By using dram vial cell culture methods, three commercially available tests for cytomegalovirus (CMV) detection were compared: direct fluorescent monoclonal antibody staining for CMV-specific early and late antigens (direct FA), indirect fluorescent monoclonal antibody staining for a CMV-specific early antigen (indirect FA), and in situ DNA hybridization with a biotinylated CMV-specific DNA probe kit (DNA probe). Of those tests, only the indirect FA provided consistent, reliable virus detection within the initial 24 h postinfection for serial 10-fold dilutions of CMV AD169 (laboratory strain) and for three selected urine samples. However, when used prospectively, the indirect FA failed to detect virus within the initial 10 days postinfection in 15 of 78 consecutive specimens that were eventually positive by cell culture. Although the indirect FA was more sensitive than the direct FA or DNA probe, its utility appeared limited to specimens with high CMV concentrations. On the basis of these data, we recommend that indirect FA be reserved as an adjunct to standard cell culture for selected samples in diagnostic hospital laboratories.

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 diagnosis of rabies infection by means of a dot hybridization assay

Dot hybridization was used to detect specific rabies RNA in brains, either from experimental infection in mouse or from brain material to be processed for routine diagnosis. 32P cDNA probes were employed to identify minute amounts of specific viral RNA. Purified RNA was obtained after phenol extraction. The RNA was fixed on nylon membranes and hybridized with a pool of M13 inserts complementary to 200-400 nucleotides of each rabies gene and mRNA. Hybridized, labelled probes were detected by autoradiography. There was strong cross-hybridization between fixed rabies and street rabies virus RNA, which enable the detection of field strains for diagnosis purpose using a fixed rabies (PV strain) cDNA. A positive response was obtained with as little as 80 ng of brain RNA material from a fixed rabies-infected mouse. Detection of viral RNA was still specific 1 week after death, the brain material being left at room temperature. A total correlation was found when the samples were examined in parallel using a fluorescent rabies-specific antibody and by virus isolation on murine neuroblastoma cells. These data show that the use of rabies-specific cDNA probes in a dot-blot hybridization assay has great potential for the diagnosis of rabies.

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.

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.

DNA hybridization for detection of human cytomegalovirus in bronchoalveolar lavage and pharynx biopsy

A simplified hybridization procedure was used for detection of cytomegalovirus (CMV) in human specimens. The probe was a 32P-labelled cloned DNA fragment of CMV strain AD169. This probe did not hybridize to DNA from uninfected cells or other herpesviruses (herpes simplex virus, Epstein-Barr virus). Specific hybridization was obtained with unselected bronchoalveolar lavage specimens, but the sensitivity of the test (33%) was lower than that of culture (80%) and immunofluorescence (60%) assays which are routinely performed in our laboratory. The detection procedure was also carried out with pharynx biopsy specimens which had been kept frozen at -70 degrees C. CMV DNA was detected in 14% of tumour specimens and only in 1.7% of control specimens (p less than 0.05). The indications of DNA hybridization for CMV diagnosis are discussed.

Viral infections in the acquired immunodeficiency syndrome

The following communication is a tripartite synopsis of the role of viral infection in the acquired immunodeficiency syndrome (AIDS). The first section describes the impact of viral opportunistic infection in AIDS; for each virus, clinical presentation and diagnosis, laboratory diagnostic approaches (with emphasis on electron microscopy), and therapeutic interventions attempted to date are discussed. The second segment explores current theories on the pathogenesis of AIDS, and describes diagnostic and therapeutic approaches to the syndrome itself. The final section catalogues ultrastructural anomalies in the cells of AIDS patients, many of which have been mistakenly identified as etiologic agents.

Disseminated cytomegalovirus infection. Molecular analysis of virus and leukocyte interactions in viremia

Viremia is a hallmark of disseminated cytomegalovirus (CMV) infection and disease. Using conventional virus culture and a subgenomic cloned CMV DNA probe to detect viral DNA within leukocytes, we studied the virus-cell interactions involved in immunocompromised patients with viremic CMV infection. CMV was recovered by culture in 17/17 samples enriched for polymorphonuclear leukocytes. Viral DNA was detected by dot-blot hybridization in 16/17 (94%). In contrast, samples enriched for mononuclear cells yielded infectious CMV in culture in only 7/15 (47%) instances; nonetheless, viral DNA was present in 16/17 samples probed. The quantity of CMV DNA in polymorphonuclear cells was significantly greater than in mononuclear leukocytes (mean 13.1 vs. 9.1 estimated viral genome equivalents per 100 cells, respectively), and CMV was always recovered from these cells regardless of the amount of viral DNA present. Yet, when the amounts of CMV DNA were virtually identical in granulocytes and mononuclear cells (6.3 and 7.1 genomic equivalents, respectively) collected simultaneously, infectious CMV could not be recovered from mononuclear cells. Although several interpretations are possible, these data are consistent with the view that CMV exists within granulocytes in a mature infectious form during viremia. The virus interactions with mononuclear cells appear to be more complex, particularly in those cells that contain CMV DNA but do not yield infectious virus.

Diagnostic deoxyribonucleic acid probes for infectious diseases

Virtually all microorganisms contain some unique nucleotide sequences which can be the target of deoxyribonucleic acid probes. Probes have been used successfully to identify a wide variety of pathogens from the simple ribonucleic acid-containing polioviruses to the complex filarial worms Brugia malayi. Probe technology offers the clinical laboratory the potential both to extend the types of pathogens that can be readily identified and to reduce significantly the time associated with the identification of fastidious microorganisms. Over a dozen commercially prepared deoxyribonucleic acid probe tests are now available. This article explores the development of deoxyribonucleic acid probe tests and reviews the sensitivity, specificity, and predictive values of many of the diagnostic probes developed during the last several years. Prospects for newer, more sensitive detection systems for the products of hybridization reactions are also reviewed.

Detection of human cytomegalovirus DNA in human tonsillar lymphocytes

The human cytomegalovirus (HCMV) was first isolated in cell cultures from the oropharynx, which is thought to be a site of primary infection. Although HCMV can be recovered from the oropharynx during reactivation phases, its exact site of latency is not known. In the present study we demonstrated evidence suggesting the presence of latent HCMV in this anatomic region--in the palatine tonsils. Samples from 30 tonsils obtained by tonsillectomy were screened for the presence of HCMV. Out of the 30 tonsil donors, 23 were seropositive for HCMV. Three methods were used in attempts to demonstrate HCMV's presence in the tonsils: (1) viral isolation attempts on various cell cultures, (2) immunohistochemical staining--immunoperoxidase method--designed to detect viral antigens, and (3) DNA dot hybridization with a HCMV-DNA probe designed to detect viral DNA. Neither infectious HCMV nor other viruses were isolated in cell cultures. No viral antigens were detected by immunoperoxidase staining in the tonsillar tissue. Four out of the 30 tonsils studied were found to contain viral DNA. In one case in which the tonsillar mononuclear (MN) fraction was separated from the polymorphonuclear (PMN) fraction, only the first fraction contained the viral DNA.

Dot immunoperoxidase assay using monoclonal antibody for direct detection of cytomegalovirus in urine samples

A rapid, simple dot immunoperoxidase assay for the direct detection of cytomegalovirus in clinical urine samples was developed. The assay was performed on nitrocellulose paper dotted with urine pellets free of cellular debris. Cytomegalovirus was detected with a monoclonal antibody to the capsid antigen, and the complex was visualized by immunoperoxidase staining. Positive reactions appeared as well-defined dark blue spots. Of the 87 urine samples examined, 10 proved positive in the dot immunoperoxidase assay, and 77 proved negative. The results agreed completely with the detection of cytomegalovirus-induced antigens in cell cultures inoculated with clinical specimens.

Comparison of dot-blot DNA hybridisation and immediate early nuclear antigen production in cell culture for the rapid detection of human cytomegalovirus in urine

The sensitivity and specificity of four modes of two assays, immediate early nuclear antigen detection in cell culture (IENAD) at 24 and 48 h post-infection (p.i.) by immunofluorescence using a murine monoclonal antibody, and dot-blot DNA hybridisation with overnight or prolonged autoradiography using the 32P-labelled HindIII J fragment of human cytomegalovirus (HCMV) DNA as probe, were compared for the rapid detection of HCMV in urine. The sensitivity of IENAD was enhanced by low-speed centrifugation at the time of inoculation. DNA hybridisation with overnight autoradiography was significantly less sensitive than IENAD at 24 h p.i. (P less than 0.001), and even with prolonged autoradiography the hybridisation assay was slower and significantly less sensitive than IENAD at 48 h p.i. (P less than 0.02). The specificity of the two assays was virtually 100%. The sensitivity of DNA hybridisation was thus clearly inferior to that of IENAD.

Evaluation of Gen-Probe DNA hybridization systems for the identification of Mycobacterium tuberculosis and Mycobacterium avium-intracellulare

The Gen-Probe DNA hybridization system, rapid diagnostic assays for the identification of Mycobacterium tuberculosis (MTB) complex and Mycobacterium avium-intracellulare (MAIC) complex, were evaluated. Designed to identify a primary mycobacterial isolate, the former correctly identified 91 of 92 MTB and all 27 non-MTB isolates and controls when compared with conventional identification methods for a sensitivity of 98.91% and specificity of 100%. The latter correctly identified 63 of 64 MAIC isolates and controls and 31 of 32 non-MAIC isolates and controls when compared with conventional identification methods for a sensitivity of 98.43% and a specificity of 96.87%. The one false positive noted with the MAIC probe was an MTB misidentified as an MAIC. The two false negatives noted above were subsequently shown to be contaminated. The tests are fast and easy to perform and interpret.

Problems in detection of cytomegalovirus in urine samples by dot blot hybridization

A hybridization assay for the detection of cytomegalovirus (CMV) in urine specimens was established. Two different DNA fragments were used as hybridization probes: the HindIII L fragment (11.7 kilobases) and the EcoRI J fragment (10.6 kilobases) of the human CMV strain AD169. These probes were used in an isolated and highly purified form and therefore did not cross hybridize with vector sequences. As shown by hybridization with DNA from CMV-infected and uninfected cells, the assay was highly CMV specific and sensitive (detection limit, 750 to 500 fg of CMV DNA). A total of 122 urine specimens were examined by DNA hybridization, virus isolation, and the detection of CMV-induced early nuclear protein. The results coincided in 91% of the samples. The application of DNA hybridization to urine samples, however, is not without problems, and some of the pitfalls and drawbacks are discussed.

Congenital cytomegalovirus infection with osteolytic lesions: use of DNA hybridization in diagnosis

A case of congenital cytomegalovirus (CMV) infection with long-bone lesions is presented. The bone lesions consisted of broad regions of generalized osteopenia with irregular fragmentation and spiculization at the zone of provisional calcification. Diagnosis of CMV infection was made by DNA spot hybridization of the urine sediment to DNA from the Towne strain of CMV, demonstrating the usefulness of DNA hybridization for identification of CMV in clinical specimens. Bone lesions associated with congenital CMV infection are useful early clues to diagnosis but can be indistinguishable from those of congenital rubella syndrome.

Comparison of in situ DNA hybridization and immunological staining with conventional virus isolation for the detection of human cytomegalovirus infection in cell cultures

The sensitivity of immunochemical staining and in situ DNA hybridization for the detection of human cytomegalovirus (HCMV) was compared with that of virus isolation. Human diploid fibroblasts were infected with serial, 10-fold dilutions of HCMV strain AD169 and examined at various intervals between 1 and 42 days after inoculation, using the three methods being compared. HCMV-DNA was detected by in situ hybridization using a biotin-labeled HCMV probe and CMV early antigen (EA) by immunochemistry using a specific monoclonal antibody. During the first 2 days after inoculation detection of EA appeared to be the most sensitive method. After the fifth day the sensitivity of the immunochemical and in situ hybridization methods was similar and equalled that of conventional virus isolation. However, 2-5 times more HCMV-DNA than HCMV-EA positive cells were detected. Our results indicate that both detection of HCMV-EA by immunological staining and HCMV-DNA by in situ hybridization are suitable methods for rapid and sensitive detection of HCMV infections.

Rapid detection of cytomegalovirus by tissue culture, centrifugation, and immunofluorescence with a monoclonal antibody to an early nuclear antigen

A rapid, sensitive and specific assay for the detection of cytomegalovirus (CMV) was developed utilizing MRC-5 cells in 24-well plates containing round coverslips. Centrifugation expedited the detection of CMV early antigen with monoclonal antibody. Immunofluorescent staining 16 h after inoculation with a stock CMV preparation (AD-169), demonstrated an 11-fold increase in the number of nuclear inclusions when the specimens were centrifuged (18 +/- 2.2) as compared to the non-centrifuged specimen (1.6 +/- 0.9). However, the number of nuclear inclusions depended on the age of the MRC-5 cells. They were more sensitive to CMV infection between 4 and 11 days after the cells were seeded into plates. Among 159 patient samples cultured for CMV, 23 (14%) were positive by the rapid method (mean of 32 h) and 18 (11%) by routine tissue culture (mean of 12 days). Cytomegalovirus in urine was detected within 1.3 days, whereas buffy coats (2.3 days) and bronchial washings (2.5 days) took longer. Staining for CMV inclusions at more than one time point was necessary for the optimal detection of CMV by the rapid method. We recommend using this assay system as it is rapid, specific, sensitive and versatile for the detection of CMV in many biological specimens.

A solution hybridization assay for ribosomal RNA from bacteria using biotinylated DNA probes and enzyme-labeled antibody to DNA:RNA

Rapid, convenient and non-isotopic nucleic-acid hybridization methods are needed for this technology to have practical use in clinical diagnostic tests. A method for hybridization of RNA with a DNA probe in solution followed by capture and measurement of the hybrid is described. DNA probes complementary to 23S rRNAs from Escherichia coli and Bacillus subtilis were labeled with a photoactivable biotin reagent. Hybridization of the biotinylated probes with rRNA was complete in less than 5 min. The resultant hybrids were allowed to bind simultaneously to succinylated avidin immobilized on latex and to beta-galactosidase-labeled Fab' fragments of a monoclonal antibody-specific for DNA:RNA. Finally, beta-galactosidase associated with the captured hybrids was measured colorimetrically. The hybridization method can detect less than 1000 bacteria per assay and has broad specificity to permit detection of the various genera of bacteria that infect the urinary tract.

Detection of CMV in urine: comparison between DNA-DNA hybridization, virus isolation, and immunoelectron microscopy

Rapid detection of CMV-DNA in urine specimens by dot-blot hybridization was compared to conventional virus isolation and to virus identification using solid-phase immunoelectron microscopy (SPIEM). To detect viral DNA, 32P-labeled EcoR1 J fragment of CMV-DNA was used as a probe in the hybridization assay. In addition, DNA extracted from infected human embryo fibroblasts (amplified DNA) was also hybridized to the same probe. Urine specimens were obtained from 10 renal transplanted patients, seven premature infants, three family members, and five children suspected of CMV infection. CMV was isolated from 10 urine specimens and SPIEM detected viral particles in nine specimens. Ten positive samples were identified as such by hybridization with DNA extracted directly from urine specimens, while hybridization with amplified DNA yielded 17 positives. Only in one urine specimen, positive by virus isolation and SPIEM, DNA was not detected by the hybridization assays. Elevated IgG or IgM-specific antibodies were found in 10 patients. Hybridization with amplified DNA proved the most sensitive and relatively rapid assay, as compared with direct DNA detection in urine, tissue culture isolation, SPIEM, or serologic tests.

Detection of Leishmania parasites by DNA in situ hybridization with non-radioactive probes

In situ hybridization techniques develop rapidly into diagnostic tools of considerable value for detection of viruses and bacteria. Here we report the application of this technique for the detection of Leishmania parasites. Biotin-labelled total promastigote DNA was hybridized to cultured Leishmania parasites and to blood and impression smears of infected mice. In promastigotes kinetoplasts were strongly stained, nuclei somewhat more diffuse. In amastigotes both nuclear and kinetoplast DNA hybridized strongly. Amastigotes were easily detected in tissue of infected mice by their stable configuration of kinetoplast and nuclei. Cross-hybridization was observed between Leishmania donovani and L. tropica, but not between these two and L. braziliensis or Trypanosoma cruzi. A minor aspecific staining of host cell nuclei in the smears did not interfere with the detectability of the parasites.

Application of DNA-based diagnosis to patient care: the example of hemophilia A

DNA-based carrier testing and prenatal diagnosis are rapidly expanding medical applications of recombinant-DNA technology. The ultimate goal of DNA-based diagnosis is the determination of the causative mutation, but, in general, this is possible only for large deletions, insertions, or certain nonsense mutation that, in most diseases, involve only a few percent of affected families. If direct diagnosis of the carrier state or fetal disease state is not feasible, indirect diagnosis can be performed by following the segregation of linked polymorphisms through the family pedigree. For such indirect diagnosis, DNA from multiple family members must be analyzed. Although this procedure is highly accurate in many families, errors can potentially occur because of meiotic recombination, genetic heterogeneity, new mutations, and nonpaternity. In this review, a general introduction to DNA-based diagnosis of mendelian diseases is presented and the methods and strategy are outlined. The use of these techniques for the diagnosis of hemophilia A is then described to illustrate the principles of diagnosis and to highlight some of the complexities encountered. DNA-based diagnosis is in its infancy and has the potential to revolutionize preventive medicine.

Detection of cytomegalovirus infections in specimens other than urine by the shell vial assay and conventional tube cell cultures

Blood, bronchoscopy-lavage, biopsy (lung, liver, kidney), sputum, and other (cecum, bone) specimens were inoculated into shell vials and conventional cell tube cultures seeded with MRC-5 cells over a 23-month period. Of 1,472 specimens, 182 (12.4%) yielded cytomegalovirus (CMV)-positive results from 81 patients. Significantly more CMV-positive specimens were detected in shell vials (n = 154; 84.6%) than in conventional tube cell cultures (n = 126; 69.2%) (P less than 0.01). We found that 98 (53.8%) of the total 182 and 41 (42.7%) of the 96 blood specimens positive for CMV were detected by both the shell vial assay and conventional tube cell cultures. However, 56 (30.7%) of the total 182 and 31 (32.3%) of the 96 blood specimens positive for CMV were obtained exclusively in shell vials after detection with monoclonal antibody. Alternatively, 28 (15.4%) of the total 182 and 24 (25%) of the 96 blood specimens positive for the virus were isolated only in conventional tube cell cultures. Thus, although the shell vial assay was more sensitive and rapid than the conventional tube cell culture method, both systems must be used, especially for blood specimens, for the laboratory diagnosis of CMV infections.

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.

Comparative efficacy of handwashing agents against cytomegalovirus

Conscientious handwashing is often recommended as an important method for limiting transmission of cytomegalovirus (CMV) from infected individuals to health, education, and child care professionals. To assess the efficacy of handwashing, fingertips of radiation-sterilized latex gloves were inoculated with 0.2 mL of ten different CMV strains. Virus in each inoculum was quantitated by plaque assay. After five minutes, viral inocula were allowed to remain (control), or were washed away by dropwise application of 10 mL of distilled water (DI), 5 mL of 0.08% soap followed by 5 mL of DI, 5 mL of 0.01% chlorhexidine gluconate followed by 5 mL of DI, or 5 mL of 0.025% povidone-iodine solution followed by 5 mL of DI. Separate glove fingertips were sampled 5, 15, 30, 60, 120 and 240 minutes after washing and cultured in duplicate for CMV. Similar studies were performed using human cadaver skin. Ordinary soap was as effective at preventing CMV recovery as other more expensive agents. For inocula with less than 5 log10 pfu CMV/mL, washing with water alone was as effective as other agents. This was confirmed in similar studies with human hands using five CMV stains. Handwashing is probably an effective method for removing CMV from contaminated hands.

Cytomegalovirus infection in homosexual men. Relationship to sexual practices, antibody to human immunodeficiency virus, and cell-mediated immunity

To investigate the relationships among cytomegalovirus infection, sexual behavior, human immunodeficiency virus (HIV) seropositivity, and indexes of cellular immunity, 180 homosexual men and 26 heterosexual men were studied. Among the homosexual men, cytomegalovirus seropositivity was associated with increased T8 lymphocyte counts (p less than 0.001) and reduced T4/T8 ratios (p = 0.006); these results were independent of HIV infection. Cytomegalovirus seropositivity was also associated with increasing age, numbers of sexual partners, and the practice of anal-receptive intercourse. At the first visit, cytomegalovirus was isolated from none of 13 cytomegalovirus-seropositive heterosexual subjects, compared with 62 (36 percent) of 171 seropositive homosexual men (p less than 0.005). Viral isolation was most common from semen. Among 32 cytomegalovirus-seropositive homosexual subjects from whom culture specimens were obtained more than four times over 10 to 30 months, 72 percent of the specimens were culture-positive. The mean duration of cytomegalovirus excretion in semen was 22 months, and in urine, the duration was nine months. Cytomegalovirus excretion was associated with younger age and reduced lymphocyte proliferation in response to cytomegalovirus, but not with antibody to HIV. Cytomegalovirus infection is sexually transmitted among homosexual men, perhaps by rectal intercourse, and is associated with alterations in T lymphocyte subsets. Most seropositive homosexual men excrete cytomegalovirus intermittently, primarily in the semen.

Molecular diagnosis of infectious diseases by nucleic acid hybridization

Diagnostic microbiology has traditionally relied on the cultivation of an infecting agent in an in vitro system. However, the limitations of these methods have led to the development of alternative, molecular techniques which can detect specific microbial proteins or nucleic acids directly in body fluids. One such method, nucleic acid hybridization, has many attractive features including the potential for high sensitivity and specificity, the detection of a chemically stable analyte and the use of uniform reagents. Nucleic acid hybridization reactions have been used to detect a variety of microbial pathogens in assay formats using extracted nucleic acids or tissue sections. However, wider application of these techniques is limited by the fact that current methods employ radioisotopically labelled probes and cumbersome assay procedures. Solutions to these problems have been sought by the development of non-radioactive hybridization techniques which utilize enzymatic detection methods and by the development of rapid hybridization assays performed in solution. Further improvements in labelling techniques, assay formats and enzymatic detection methods should allow for the wider application of nucleic acid hybridization reactions in diagnostic microbiology.

[Technic of nucleic acid hybridization and its significance for diagnostic problems]

Nucleic acid hybridization techniques (e.g., Southern blotting and in situ hybridization) gain increasing importance in laboratory medicine, as demonstrated by examples in this paper. The molecular basis of this approach to detect nucleic acids homologous to known DNA probes is explained. It is concluded that this technique has advantages in the detection of pathogens compared to other methods used in laboratory medicine.

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.

Nucleic acid probes in clinical microbiology

The infectious disease applications of nucleic acid probe have been described. In addition, the basic procedures of nucleic acid probe technology have been discussed, as have the factors affecting implementation of probe technology in diagnostic laboratories. Despite the questions raised, nucleic acid probes will become part of the diagnostic laboratory in the near future. Commercial interests are developing and marketing new probes, reagents, and kits which will expedite the employment of this technology. High-volume reference laboratories will first use probes as part of a battery of tests which will include ELISA and monoclonal antibody methods. In all probability, probes will replace methods: that have proven to be ineffective, difficult, or costly such as culturing for some enteric pathogens and Legionella, that require long incubation periods, such as mycobacteria, or that have high costs and low yields, such as virology.

Detection of varicella-zoster virus in lymphocytes by DNA hybridization

The availability of cloned varicella-zoster virus (VZV) DNA probes allows rapid detection of viral-specific DNA by "dot-blot" hybridization in lymphocytes or in lesion aspirates. Thirty-six blood specimens were obtained from 25 patients with suspected varicella or zoster. VZV-specific DNA was demonstrated in 15 lymphocyte preparations of nine patients with varicella and in one with disseminated zoster out of five patients with zoster. VZV-specific DNA was detected prior to rise in antibodies, indicating early viremia in these patients. Virus isolation from lesions and serological tests confirmed VZV infections. VZV-specific DNA was detected in lymphocytes of three patients out of six with active herpetic lesions, whereas it was not detected in lymphocyte specimens from two patients with undiagnosed rash or four with lymphoproliferative diseases, who did not present varicella or zoster, or from 18 healthy controls. No signal was obtained in herpes simplex virus (HSV)-infected and -uninfected cell lines. The hybridization assay proved that specific and viral or cellular DNAs other than VZV did not cross-hybridize with the probe. The sensitivity limit of detection was 4-15 pg of homologous DNA, and the assay was accomplished within 72-96 hr. These results point to the possible rapid diagnosis of VZV infection in patients suspected of varicella or generalized zoster. In addition, simultaneous infection with both VZV and HSV seems to occur in some patients.

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.

Detection of hepatitis A virus in seeded estuarine samples by hybridization with cDNA probes

The development and trials of a nucleic acid hybridization test for the detection of hepatitis A virus (HAV) in estuarine samples within 48 h are described. Approximately 10(4) physical particles of HAV per dot could be detected. Test sensitivity was optimized by the consideration of hybridization stringency, 32P energy level, probe concentration, and nucleic acid binding to filters. Test specificity was shown by a lack of cross-hybridization with other enteroviruses and unrelated nucleic acids. Potential false-positive reactions between bacterial DNA in samples and residual vector DNA contamination of purified nucleotide sequences in probes were eliminated by DNase treatment of samples. Humic acid at concentrations of up to 100 mg/liter caused only insignificant decreases in test sensitivity. Interference with hybridization by organic components of virus-containing eluates was removed by proteinase K digestion followed by phenol extraction and ethanol precipitation. The test is suitable for detecting naturally occurring HAV in samples from polluted estuarine environments.