Comparison of an avidin-biotin immunoassay with three commercially available immunofluorescence kits for typing of herpes simplex virus

Quantification of 5-methylcytosine, 5-hydroxymethylcytosine and 5-carboxylcytosine from the blood of cancer patients by an enzyme-based immunoassay

BACKGROUND

Genome-wide aberrations of the classic epigenetic modification 5-methylcytosine (5mC), considered the hallmark of gene silencing, has been implicated to play a pivotal role in mediating carcinogenic transformation of healthy cells. Recently, three epigenetic marks derived from enzymatic oxidization of 5mC namely 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC), have been discovered in the mammalian genome. Growing evidence suggests that these novel bases possess unique regulatory functions and may play critical roles in carcinogenesis.

METHODS

To provide a quantitative basis for these rare epigenetic marks, we have designed a biotin-avidin mediated enzyme-based immunoassay (EIA) and evaluated its performance in genomic DNA isolated from blood of patients diagnosed with metastatic forms of lung, pancreatic and bladder cancer, as well as healthy controls. The proposed EIA incorporates spatially optimized biotinylated antibody and a high degree of horseradish-peroxidase (HRP) labeled streptavidin, facilitating signal amplification and sensitive detection.

RESULTS

We report that the percentages of 5mC, 5hmC and 5caC present in the genomic DNA of blood in healthy controls as 1.025±0.081, 0.023±0.006 and 0.001±0.0002, respectively. We observed a significant (p<0.05) decrease in the mean global percentage of 5hmC in blood of patients with malignant lung cancer (0.013±0.003%) in comparison to healthy controls.

CONCLUSION

The precise biological roles of these epigenetic modifications in cancers are still unknown but in the past two years it has become evident that the global 5hmC content is drastically reduced in a variety of cancers. To the best of our knowledge, this is the first report of decreased 5hmC content in the blood of metastatic lung cancer patients and the clinical utility of this observation needs to be further validated in larger sample datasets.

Detection of cutaneous herpes simplex virus infections by immunofluorescence vs. PCR

BACKGROUND

Detection of cutaneous infections with herpes simplex virus (HSV) has proven difficult, as serum antibody tests sometimes are not sensitive and specific enough for that purpose.

OBJECTIVE

This study was conducted to compare the sensitivity for detection of HSV of an immunofluorescence method (Syva Microtrak) and an internally controlled PCR.

METHODS

Cutaneous swabs from skin lesions were analysed by immunofluorescence separately for HSV types 1 and 2 and by competitive PCR. Detection of PCR products was done by ELISA, if positive additionally by agarose gel electrophoresis.

RESULTS

Of 79 samples 34 were PCR-positive by ELISA (34 = 100%), of which 23 (68%) were also positive on the agarose gel. Eleven samples (32%) were positive by immunofluorescence. No sample was positive by immunofluorescence and negative by PCR.

CONCLUSIONS

These results demonstrate that immunofluorescence using Syva Microtrak is not suitable for exclusion of herpes simplex virus infection as sensitivity was only 32%. However, as immunofluorescence is cheaper and faster than PCR, first screening can be done with immunofluorescence, and negative samples can be investigated by PCR to finally prove or exclude the presence of HSV DNA.

Comparison of various transport media for viability maintenance of herpes simplex virus, respiratory syncytial virus, and adenovirus

Seven viral transport media (VTM) were compared for effectiveness in preserving the infectivity of herpes simplex virus (HSV), respiratory syncytial virus (RSV), and adenovirus. The media tested were Richards viral transport, sucrose-phosphate-glutamate (SPG), Virocult, HH medium, tryptose phosphate broth, cell culture medium, and Bartel's viral transport. Two laboratory strains of HSV (McIntyre and 333) and two clinical isolates (A0301 and A0386), comprising two HSV-1 types and two HSV-2 types, were suspended in each transport medium, kept at 4 degrees C and 22 degrees C, and assayed for surviving virus at various times of up to 2 weeks. Similar testing was done with RSV Long strain and adenovirus type 2. Of the seven media, Richards viral transport, SPG, Virocult, and HH medium, followed closely by tryptose phosphate broth, best preserved HSV infectivity at both 4 degrees C and 22 degrees C. Analysis of decay rates of RSV revealed comparatively rapid decay in SPG and Virocult. Adenovirus was stable in all media and at both temperatures tested. These results indicate that viral transport and subsequent culture isolation are possible using many different VTMs if transport times are kept to a minimum (< 1 day), but if transport extends to longer times, or low levels of virus are present in the specimen, Richards viral transport and HH medium appeared to be the best overall transport media for the viruses tested.

Centrifugation-shell vial technique for rapid detection of herpes simplex virus cytopathic effect in Vero cells

A centrifugation-shell vial technique for herpes simplex virus detected the virus in 50 (24.6%) of 203 specimens by cytopathic effect at 48 h, compared with detection of the virus in 47 (23.2%) specimens by immunofluorescence at 24 h. The rapid detection of cytopathic effect may be useful to laboratories that are not interested in typing all herpes simplex virus specimens but that wish to reduce the cost of herpesvirus cultures.

Suitability of new chlamydia transport medium for transport of herpes simplex virus

A new chlamydia transport medium (ChlamydiaPort; Scott Laboratories, Inc., Fiskeville, R.I.) was evaluated for its suitability as a transport medium for herpes simplex virus (HSV). Two laboratory HSV strains (McIntyre and 333) and two clinical isolates (AO218 and AO301) were suspended in ChlamydiaPort, ViraPort (Scott Laboratories), and cell culture medium and maintained at 2 and 22 degrees C. Samples were tested at various time intervals to determine surviving virus. The range of half-lives of the HSV strains held at 2 degrees C in ChlamydiaPort medium was from 3.5 to 10 days, while virus stability was greater in ViraPort and less in cell culture medium. These HSV strains held at 22 degrees C in ChlamydiaPort had half-lives from 1.5 to 6 days, which were significantly greater than the half-lives of the viruses held in either tissue culture medium or ViraPort. Clinical specimens were tested for virus by using the Selecticult-HSV (Scott Laboratories) system to determine the performance of the transport medium under field conditions. Clinical specimens maintained up to 5 days at ambient temperatures in ChlamydiaPort medium appeared suitable for diagnostic testing without detectable loss of positive specimens. In addition, there was a significant decrease in the average time required for diagnosis when compared with a standard transport system, Virocult (Microdiagnostics, Cleveland, Ohio). These results show that HSV infections can be successfully diagnosed in distant virology laboratories by shipping specimens in ChlamydiaPort transport medium at ambient temperatures.