Comparison of two enzyme-linked immunosorbent assays for detection of herpes simplex virus antigen

Advances in the management of viral infections

Viral infections are common in cancer patients. The risk and severity of infection are influenced by patient, disease, treatment, and viral factors. Severe viral infections are more likely to occur in treatment regimens that are more immunosuppressive. Historically, the most frequent severe infections have been due to herpesviruses, but more recently, other pathogens, especially community respiratory and hepatitis viruses, have received increasing attention as major viral pathogens in cancer patients. Because of the new diagnostic assays and the introduction of better therapeutic options, knowledge of viral infections is important in optimizing antineoplastic therapies.

The laboratory diagnosis of herpes simplex virus infections

Herpes simplex virus (HSV) types 1 and 2 cause genital herpes infections and are the most common cause of genital ulcer disease in industrialized nations. Although these infections are very common, the majority of them remain underdiagnosed because they are asymptomatic or unrecognized. A clinical diagnosis of genital herpes should always be confirmed by laboratory testing; this can be accomplished through the use of direct tests for viral isolation, the detection of antigen or, more recently, the detection of HSV DNA using molecular diagnostic techniques. Testing for serotypes is recommended because of the different prognostic and counselling implications. Type-specific HSV serology is becoming more readily available and will enhance the ability to make the diagnosis and guide clinical management in select patients.

Viral supraglottitis in an adult: a case presentation and literature update

Viral epiglottitis (supraglottitis) is a rare entity but its presentation can mimic that of bacterial epiglottis. Regardless of the causative agent, supraglottitis is a serious disease mostly affecting children and rarely seen in adults. Early suspicion and proper evaluation are mandatory to prevent a life-threatening crisis. In both children and adults the infectious aetiology in supraglottitis is predominantly bacterial while viruses are rare, especially in adults. We describe a case of supraglottitis in an adult in which the symptoms were insidious and blood indices suggested a bacterial aetiology. However, laryngoscopic examination revealed an ulcer over the left aryepiglottic fold and serology was positive for Herpes simplex virus (HSV) IgM. Because supraglottitis due to HSV is a rare entity with few reported cases in the literature, this case is presented to highlight the viral involvement in this disease and its management.

Specific diagnostic methods for herpesvirus infections of the central nervous system: a consensus review by the European Union Concerted Action on Virus Meningitis and Encephalitis

BACKGROUND

Herpesvirus infections of the central nervous system are often severe but are fortunately rare. The incidence of these infections has however, increased in recent years as a consequence of an increase in the number of immune-compromised individuals. New diagnostic procedures have improved our ability to diagnose these infections and herpesviruses may yet be implicated as the cause of further neurological diseases with no known aetiology. Methodological standards for selection and evaluation of patient materials are essential to the provision of reliable diagnosis, yet few studies have addressed this important issue.

OBJECTIVES

To describe and define methodological standards and reference methodology for diagnosis of herpesvirus infections of the CNS.

STUDY DESIGN

Information gathered by literature review.

RESULTS

Only for herpes simplex encephalitis is there sufficient data to allow the definition of reference methodology. Good methodological standards exist but few studies have adhered to these standards. As methods for the detection of specific intrathecal antibody synthesis are well established yet under-used in diagnostic virology, the principle of these measurements is reviewed in some detail.

CONCLUSIONS

Herpesvirus infections of the CNS are of increasing importance. High quality, multi-centre studies are needed to establish the value of the new diagnostic test procedures if further improvement in the diagnostic sensitivity and specificity of these procedures is to be achieved.

Quantitative determination and visualization of herpes simplex virus type 1 antigen, free and cell-bound by ELISA

A method of quantifying and visualizing herpes simplex virus type 1 antigen by indirect enzyme-linked immunosorbent assay (ELISA) is described. This assay is simplified by the use of polyclonal serum and can be applied to the quantification of free antigen as well cell-bound. Moreover, cell viral antigen can be visualized. Antigen sources were viral suspensions, infected cells and proteins extracted from infected cells. The assay was specific and its sensitivity was dependent on the antigen source. The technique was regarded as specific within a range showing a direct correlation (r > 0.8) between the concentration of the antigen and the net absorbance value (the difference of the absorbance obtained with the viral antigen minus the control antigen). The technique has advantages over other ELISA procedures: does not require monoclonal antibodies, or labelled antiviral immunoglobulins or antiviral serum from two different species. In addition total free antigen can be measured.

Comparison of a direct antigen enzyme immunoassay, Herpchek, with cell culture for detection of herpes simplex virus from clinical specimens

Direct enzyme immunoassay (Herpchek) was compared with culture on 21,522 specimens mainly from asymptomatic women for herpes simplex virus detection. Sensitivity and specificity were 73.8 and 97.7%, respectively. The 33% detection rate by enzyme immunoassay in 5 h increased to 43% when the enzyme immunoassay was combined with culture. Herpchek alone was not sensitive enough, but in combination with culture, maximum detection was achieved.

Comparison of three monoclonal antibody-based enzyme immunoassays for detection of herpes simplex virus in clinical specimens

Three commercial monoclonal antibody-based enzyme immunoassays (Herpchek, IDEIA HSV and SureCell HSV) for detection of herpes simplex virus antigen were compared with isolation of virus in cell cultures. A total of 51 culture positive and 49 culture negative consecutively collected specimens that had been stored at -70 degrees C for a period of up to ten months were used in the study. Herpchek, IDEIA HSV and SureCell HSV assays gave a sensitivity of 88.2%, 82.4% and 47.1% respectively, and a specificity of 95.9%, 93.9% and 83.7% respectively compared to cell culture. A blocking antibody test showed that two culture negative specimens contained herpes simplex virus-specific antigens. If these two specimens were considered to be true positive, Herpchek, IDEIA HSV and SureCell HSV assays had a sensitivity of 88.7%, 83.0% and 47.2%, and a specificity of 100%, 97.9% and 85.1% respectively. The positive predictive value (using the resolved sample results) for Herpchek, IDEIA HSV and SureCell HSV was 100%, 97.8% and 78.1% respectively, and the negative predictive value 88.7%, 83.6% and 58.8% respectively. These results demonstrated that Herpchek and IDEIA HSV are sensitive and highly specific assays. Results could be obtained in less than five hours after receipt of specimens. SureCell HSV gave results in 15 minutes, but both the sensitivity and specificity were too low for this test to be considered as a substitute for culture.

Laboratory techniques in the diagnosis of herpes simplex infection

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Determination of the optimal cutoff value for a serological assay: an example using the Johne's Absorbed EIA

Traditionally, in order to improve diagnostic accuracy, existing tests have been replaced with newly developed diagnostic tests with superior sensitivity and specificity. However, it is possible to improve existing tests by altering the cutoff value chosen to distinguish infected individuals from uninfected individuals. This paper uses data obtained from an investigation of the operating characteristics of the Johne's Absorbed EIA to demonstrate a method of determining a preferred cutoff value from several potentially useful cutoff settings. A method of determining the financial gain from using the preferred rather than the current cutoff value and a decision analysis method to assist in determining the optimal cutoff value when critical population parameters are not known with certainty are demonstrated. The results of this study indicate that the currently recommended cutoff value for the Johne's Absorbed EIA is only close to optimal when the disease prevalence is very low and false-positive test results are deemed to be very costly. In other situations, there were considerable financial advantages to using cutoff values calculated to maximize the benefit of testing. It is probable that the current cutoff values for other diagnostic tests may not be the most appropriate for every testing situation. This paper offers methods for identifying the cutoff value that maximizes the benefit of medical and veterinary diagnostic tests.

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.

Herpes simplex virus infections during the decade since the licensure of acyclovir

The development and use of acyclovir accelerated in the area of the natural history, epidemiology, and biology of herpes simplex viruses. The development of serologic assays that differentiate HSV-1 from HSV-2 demonstrated the worldwide distribution of genital herpes, the role genital ulcers play in facilitating HIV transmission, and the high frequency in which pregnant women acquire HSV infection. The high reactivation rate of HSV-2 infections, the often silent nature of genital herpes, and its widespread anatomic distribution in the genitourinary tract lead to frequent subclinical transmission. Identification and counselling of the asymptomatic carrier is necessary if we are to decrease the transmission of genital herpes.

Evaluation of an automated immunodiagnostic assay system for direct detection of herpes simplex virus antigen in clinical specimens

The Vitek ImmunoDiagnostic Assay System (VIDAS) is a 2 1/3-h automated qualitative enzyme-linked fluorescent immunoassay developed for the direct detection of herpes simplex virus (HSV) antigen in clinical specimens. A total of 356 clinical specimens submitted for HSV isolation were prospectively evaluated with the VIDAS, and the results of the technique were compared with those of both HSV isolation in cell culture and Herpchek, a nonautomated enzyme immunoassay. Compared to cell culture, VIDAS had a sensitivity of 91.6% and a specificity of 89.3%, with positive and negative predictive values of 82.6 and 95.0%, respectively. In comparison to Herpchek, VIDAS had a sensitivity of 93.7% and a specificity of 93.0%, with positive and negative predictive values of 89.4 and 95.9%, respectively. The results demonstrated that the VIDAS required minimal manipulation in order to produce results comparable to those of Herpchek and HSV isolation in cell culture.

Evaluation of an enzyme-linked immunoassay employing a covalently bound capture antibody for direct detection of herpes simplex virus

The FDL enzyme-linked immunosorbent assay (ELISA; Fairleigh Dickinson Laboratories, Inc., Abilene, Tex.) for the detection of herpes simplex virus (HSV) makes use of a covalently attached antibody. This assay was compared with viral isolation and with the Ortho HSV Antigen Detection ELISA (Ortho Diagnostic Systems, Inc., Raritan, N.J.). One hundred forty-eight specimens were tested. The FDL ELISA identified 66 of 104 specimens from which HSV was isolated, yielding a sensitivity of 63% and a specificity of 95%. These results compared favorably with those obtained by using the Ortho ELISA. The total test time was shorter and the washing step was simpler than that with the Ortho assay, making the FDL assay an attractive alternative to similar methodologies.