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

Comparison of the rapid second generation directigen EIA with cell culture and immunofluorescence for the detection of respiratory syncytial virus in nasopharyngeal aspirates

BACKGROUND

A second generation-RSV enzyme immunoassay (EIA) was compared with cell culture and immunofluorescence to determine the improved efficacy of this reformulated system.

OBJECTIVES

This study was performed to identify whether the EIA might serve an ancillary function during non-operational virology hours, or whether the EIA may serve as a replacement of the commonly used direct fluorescent assay (DFA).

STUDY DESIGN

During the 1992-1993 (September-April) RSV season, 124 freshly collected nasopharyngeal (NP) aspirates were tested by the EIA and the DFA for the presence of antigen to the infectious agent. Infectivity was performed by tube culture cytopathic effect (TC-CPE) in parallel with the two antigen detection methodologies.

RESULTS

Thirteen of the 48 confirmed positive specimens (27%) failed to yield infectious virus by TC-CPE. The sensitivity, specificity, positive and negative predictive values of the EIA were 90, 95, 91 and 94% respectively. This observed sensitivity of 90% using freshly collected NP aspirates, represents a marked improvement over an earlier generation EIA kit.

CONCLUSIONS

Considering the simplicity and speed of this EIA (10 min), the test is recommended for use by medical personnel when facilities for DFA and traditional virus culture are not readily available.

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.

A fifth human cytomegalovirus glycoprotein B genotype

Genetic variation in glycoprotein B (gB) may play a role in human cytomegalovirus (HCMV) pathogenesis. Using restriction endonuclease digestion and DNA sequencing, a unique gB genotype was identified in eight HCMV strains isolated from five patients with the acquired immune deficiency syndrome. Nucleic acid homology to the four previously described gB genotypes ranged from 79 to 91% for the two major variable regions of gB. Studies of the role of gB in HCMV pathogenesis should recognize the existence of live gB genotypes.

Significance of leukocyte concentration in the performance of the quantitative cytomegalovirus (CMV) antigenemia assay

BACKGROUND

The quantitative cytomegalovirus-antigenemia (CMV-Ag) assay is an important technology in the regimen of tests utilized in the care and management of acquired immunodeficiency syndrome (AIDS) and other immunocompromised patient groups. Performance of this assay is contingent upon the appropriate processing of the polymorphonuclear leukocyte (PMNL) compartment of the peripheral blood. However, a cell input standard in the performance of the CMV-Ag assay, has not been established. Interpretive differences between laboratories utilizing the CMV-Ag assay may reflect this lack of test uniformity.

OBJECTIVES

To determine the effect of different PMNL concentrations on the quantitation of CMV in peripheral blood. The leukocyte concentration resulting in optimal rates of viral detection, will be compared with the shell vial assay-indirect immunofluorescent assay (SVA-IFA), and conventional tube culture (TC-CPE).

STUDY DESIGN

A total of 74 freshly collected blood specimens were tested by the CMV-Ag assay, using cytospin preparations consisting of 2 x 10(5), 4 x 10(5) and in preliminary experiments, 8 x 10(5) PMNLs/slide. Data obtained from these studies were compared to SVA-IFA and TC-CPE. Viral load was monitored among 11 symptomatic patients through sequential testing of these patients at the start of ganciclovir (GCV), foscarnet (PFA), or combination drug therapy.

RESULTS

Among 74 blood specimens tested by the CMV-Ag assay, cytospin preparations consisting of 4 x 10(5) compared with 2 x 10(5) PMNLs/slide, affected a mean positive cell increase of 215% (P = 0.03). PMNL slide preparations consisting 8 x 10(5) cells produced background levels which prevented accurate reading of slides. The CMV-Ag assay was more sensitive than the SVA-IFA, but equivalent to TC-CPE. Among 11 patients started on drug therapy, viral load was markedly reduced in 8 within 2-3 weeks; three patients (2 deceased within 3 weeks after receiving therapy), showed no decrease in viral load. One patient was identified as harboring a PFA resistant strain.

CONCLUSIONS

A PMNL concentration of 4 x 10(5) cells facilitated the reading of CMV-Ag assay slide preparations. The modified CMV-Ag assay furthermore, is applicable in the monitoring of viral load for the tracking of susceptible or resistant CMV strains.

Aluminosilicates enhance the infectivity of cytomegalovirus in urine using centrifugation-enhanced antigen detection technology

Due to the inherent lability of CMV, necessary laboratory identification of this infectious agent is often compromised by a delay in specimen transport. Previous studies have addressed the phenomenon of infectivity enhancement/reduction in the rate of infectivity loss by the incorporation into various viral assay systems of trace concentrations of the adsorbents montmorillonite (bentonite [M]) or kaolinite (kaolin [K]). We extended these studies to the clinical setting to identify whether such aluminosilicates would effect an enhanced level of CMV infectivity. The shell vial assay-indirect immunofluorescent assay (SVA-IFA) was utilized in comparative testing throughout this study. The addition of trace concentrations of M or K to the SVA-IFA was found to enhance the infectivity of CMV in urine by 115 and 126%, respectively. The total CMV detection rate by SVA-IFA was 29% (30/105). Three of the 30 (10%) CMV positive specimens were detected only in shell vials which had been supplemented with K or M. Two specimens were isolation positive alone. The addition of K or M to shell vials immediately prior to the start of the SVA-IFA has the potential of (a), enhancing assay readability by increasing the number of fluorescent focus units per vial monolayer and (b), of detecting positive urine specimens with low viral titers which might otherwise not be identified using the conventional SVA-IFA procedure.

Cell culture-PCR technique for detection of infectious cytomegalovirus in peripheral blood

We determined the efficacy of PCR for the direct detection of infectious cytomegalovirus (CMV) in specimen-inoculated MRC-5 tube cultures (cell culture-PCR [CC-PCR]). Parallel testing was performed by a shell vial assay-indirect immunofluorescence assay (SVA-IFA) and isolation (conventional MRC tube cultures [TC-CPE]. The sensitivity, specificity, and positive and negative predictive values for CC-PCR, SVA-IFA, and TC-CPE were 81, 99, 94, and 94%, 86, 100, 100, and 96%, and 77, 100, 100, and 93%, respectively. Future application of CC-PCR may be directed toward its use as a screening tool for cytomegalovirus genotypic variants.

Acute lumbosacral polyradiculopathy in acquired immunodeficiency syndrome: experience in 23 patients

We reviewed our experience in 23 patients with acquired immunodeficiency syndrome (AIDS) who had acute lumbosacral polyradiculopathy. The patients developed a distinctive syndrome of rapidly progressive flaccid paraparesis and areflexia that was frequently associated with sphincter disturbances. Persuasive laboratory evidence of a cytomegalovirus polyradiculopathy (polymorphonuclear pleocytosis or confirmatory cerebrospinal fluid culture) was found in 15 of the 23 patients. Treatment with ganciclovir in these patients led to clinical stabilization, although worsening during the first 2 weeks of treatment was common. Most patients with cytomegalovirus polyradiculopathy had severe residual deficits. Metastasis from systemic lymphoma accounted for the polyradiculopathy in 2 other patients. A more benign syndrome was identified in the remaining 6 patients. They generally had slower clinical progression and less severe neurological deficits at their nadir than did patients with cytomegalovirus polyradiculopathy. Unlike patients with cytomegalovirus infection, their cerebrospinal fluid showed a predominantly mononuclear pleocytosis. Moreover, spontaneous improvement without treatment was common. Our experience together with the published experience of others suggests that the acute lumbosacral polyradiculopathy in AIDS is a clinical syndrome with different etiologies and variable clinical outcome. Recognition of this heterogeneity is necessary for the management of individual patients, as well as the interpretation of treatment results.

Antiviral susceptibility testing of cytomegalovirus from primary culture using shell vial assay to detect the late viral antigen

Susceptibility testing of 68 cytomegalovirus (CMV) peripheral blood isolates to Ganciclovir (DHPG) and 11 blood isolates to Foscarnet (PFA), was performed on primary culture isolates using the shell vial assay methodology (SVA-IFA, that is, quantitation of fluorescent focus units, FFUs), with an anti-CMV monoclonal antibody to the late viral antigen. A positive reaction in monolayer cultures of MRC-5 cells was characterized by cytoplasmic fluorescence with inclusions at both or more commonly off one end of the elongated fibroblast nucleus. Isolates from conventional MRC-5 tube cultures displaying a 1+ (10% cytopathic effect) were inoculated into shell vials containing DHPG concentrations of 0, 1.5, 3, 6, 12, or 24 microliters/ml shell vials containing 400, 500, 800, or 1200 microM PFA. The optimal readability of monolayers (expressed as FFUs per monolayer) occurred at 96 h after treatment with DHPG and at 36-48 h with PFA. Resistance to DHPG was determined at the concentration of antiviral agent necessary to reduce the number of FFUs to 90% or 50% of the control [that is, the 90% minimum inhibitory concentration (MIC90) or MIC50]. Six of 68 isolates showed an MIC90 > 12 or an MIC50 > 1.5 microgram/ml, and were considered DHPG resistant. Three of the six isolates were from AIDS patients with late-stage disease who had never received DHPG therapy. All but one (specimen 2400) DHPG-resistant isolates revealed MIC90 values to a PFA concentration of 500 microM, which is considered an achievable peak plasma level in patients undergoing PFA therapy. The single DHPG- and FPA-resistant isolate was obtained from a patient displaying marked clinical resistance to both drugs.(ABSTRACT TRUNCATED AT 250 WORDS)

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.