Rapid detection, culture-amplification and typing of herpes simplex viruses by enzyme immunoassay in clinical samples

Real-time nested multiplex PCR for the detection of Herpes simplex virus types 1 and 2 andVaricella zoster virus

One hundred forty-nine specimens were tested in a LightCycler nested multiplex polymerase chain reaction (LCnmPCR) for Herpes simplex virus (HSV)1, HSV2, and VZV. Eighty-one were from genitourinary medicine (GUM) patients and the other 68 specimens were from other patients with skin lesions. The results were compared to a conventional multiplex nested PCR (nmPCR) using agarose gel electrophoresis. Twenty-five specimens were positive in both assays for HSV1 and 29 were positive for VZV. For HSV2 there were 27 positive in the LCnmPCR and 26 positive in the nmPCR assay. The melting temperatures (Tms) of each target were different with a mean of 84.75 degrees C for HSV1, 88.57 degrees C for HSV2, and 83.62 degrees C for VZV. The melting curves of positive specimens directly overlaid the melting curves of the positive controls in the assay. The LCnmPCR assay is a convenient alternative to conventional PCR using agarose gel electrophoresis. It improves specimen turnaround time by eliminating the need for gel electrophoresis, transillumination, and gel photography. It also shows increased sensitivity for HSV2 over our standard assay. This LCnmPCR reduces further the possibility of amplicon contamination with nested PCR protocols.

Detection and subtyping of Herpes simplex virus in clinical samples by LightCycler PCR, enzyme immunoassay and cell culture

BACKGROUND

Prompt laboratory diagnosis of Herpes simplex virus (HSV) infection facilitates patient management and possible initiation of antiviral therapy. In our laboratory, which receives various specimen types for detection of HSV, we use enzyme immunoassay (EIA) for rapid detection and culture of this virus. The culture of HSV has traditionally been accepted as the diagnostic 'gold standard'. In this study, we compared the use of real time PCR (LightCycler) for amplification, detection and subtyping of specific DNA with our in-house developed rapid and culture tests for HSV.

RESULTS

The LightCycler PCR (LC-PCR) detected and subtyped HSV in 99% (66/67) of HSV positive specimens, compared to 81% (54/67) by rapid antigen EIA or 57% (36/63) by culture. A specimen was considered positive when two or more tests yielded HSV identifications or was culture positive. Discordant results were confirmed with an in-house developed PCR-ELISA or DNA sequence analysis. The typing results obtained with the LC-PCR and by culture amplified test were completely concordant.

CONCLUSIONS

This study showed that the LC-PCR provided a highly sensitive test for simultaneous detection and subtyping of HSV in a single reaction tube. In addition to increased sensitivity, the LightCycler PCR provided reduced turn-around-times (2 hours) when compared to enzyme immunoassay (4 hours) or culture (4 days).

Inappropriate antidiuretic hormone secretion, abdominal pain and disseminated varicella-zoster virus infection: an unusual triad in a patient 6 months post mini-allogeneic peripheral stem cell transplant for chronic myeloid leukemia

Severe abdominal pain followed by inappropriate antidiuretic hormone secretion (SIADH) preceding by several days the skin manifestation of varicella-zoster virus (VZV) infection in an immunocompromised patient is described. This is a rare presentation of a severe infection described previously only once in a chronic myeloid leukemia (CML) patient 5 months post allo-BMT during immunosuppressive treatment with cyclosporin A. This is the first case described in the setting of non-myeloablative preparation with fludarabine and melphalan and followed by donor leukocyte infusion (DLI) 2 and 4 months post allo-BMT. The influence of these factors on development of VZV virus infection is discussed. We also highlight the high incidence and high mortality in VZV infection in immunocompromised patients as well as the frequent atypical presentation.

Diagnosis of herpes simplex virus infections in the clinical laboratory by LightCycler PCR

Herpes simplex virus (HSV) causes several clinical manifestations in both normal and immunocompromised hosts; this agent is the most frequently detected virus in diagnostic laboratories. Recovery of the virus in cell culture is considered the "gold standard" for detection of this virus from sources other than cerebrospinal fluid. LightCycler is a newly developed, commercially available system designed to rapidly perform PCR, with real-time detection of PCR products by a fluorescence resonance energy transfer assay. We compared the detection of HSV for 200 specimens (number of genital specimens, 160; number of dermal specimens, 38; number of ocular specimens, 2) by shell vial cell cultures (MRC-5) and by LightCycler PCR. Of a total of 88 (44%) HSV strains detected, 69 (78%) were detected by both shell vial cell cultures and LightCycler PCR (DNA polymerase target). A total of 19 (22%) specimens were detected exclusively by LightCycler PCR. No specimens were positive by the shell vial assay only. All 19 discrepant samples had HSV DNA detected by an independent PCR directed to the thymidine kinase gene of the virus. The melting curve analysis feature of the LightCycler instrument identified identical genotype results for HSV type 1 (HSV-1) and HSV-2 from 84 of 88 (96%) positive samples. Specimens can be extracted, target HSV DNA can be amplified, and HSV PCR products can be identified by genotype within 2 h after receipt of specimen into the laboratory. The increased level of accurate identification (all 88 positive samples) compared with that of shell vial cell culture (69 of 88 samples identified as positive) and the agreement of LightCycler PCR results with all shell vial positive results indicate the potential for routine implementation of this technology for laboratory diagnosis of HSV infections.

Comparison of six nucleic acid extraction methods for detection of viral DNA or RNA sequences in four different non-serum specimen types

BACKGROUND

Extraction of viral nucleic acids from serum samples is widely used in diagnostic pathology tests. However, the heterogeneous nature of non-serum samples may contribute to variations in the yields of viral nucleic acids with different extraction methods and specimen types.

OBJECTIVES

Six different methods were compared for optimal extraction of viral DNA or RNA from four types of non-serum specimens.

STUDY DESIGN

The DNA viruses used were herpes simplex virus and cytomegalovirus. The RNA viruses were poliovirus, rotavirus and small round structured virus. The specimens used were from respiratory, genital, faecal and peripheral blood mononuclear cell samples. The extracted nucleic acids were amplified by PCR and detected in an enzyme immunoassay using digoxygenin-labelled amplicons.

RESULTS AND CONCLUSIONS

For extraction of viral DNA, the phenol-chloroform method yielded the highest amount of DNA as judged by endpoint titration. The three methods compared for extraction of viral RNA used guanidine isothiocyanate and the QiaRNA kit was shown to yield the highest amount of viral RNA.

A comparison of virus isolation, indirect immunofluorescence and nested multiplex polymerase chain reaction for the diagnosis of primary and recurrent herpes simplex type 1 and type 2 infections

134 swabs in viral transport medium were received from 126 patients with suspected clinical HSV-1 and HSV-2 infections. They were tested by (i) nested multiplex polymerase chain reaction NMPCR (strongly positive specimens had visible bands on both rounds of PCR) without prior extraction, (ii) culture in primary rhesus monkey kidney, E6-Vero, RD and HEp-2 cells and (iii) antigen detection by immunofluorescence (IF). Antigen detection employed four novel pools (A-D) of monoclonal antibodies (Mab): A was HSV-1 specific, B was HSV-2 specific while C and D were generic. In comparison to NMPCR the sensitivity and specificity of (i) culture was 59% (22/37) and 100% (134/134), (ii) IF by Pool A was 59% (16/27) and 100% (117/117), (iii) IF by Pool B was 40% (4/10) and 100% (130/130) and (iv) IF by Pools C and D were 60% (18/30) and 100% (96/96). Specimens positive by culture were more likely to be strongly positive by NMPCR (chi2 P = 0.004). Typing by each method concurred on all occasions. NMPCR was cost effective, easier to perform and was the most sensitive method for HSV detection. It should become the method of choice for HSV diagnosis.