Simple microwave and thermal cycler boiling methods for preparation of cervicovaginal lavage cell samples prior to PCR for human papillomavirus detection

The advent of human papillomavirus detection for cervical screening

PURPOSE OF REVIEW

This review updates progress in the human papillomavirus (HPV)-based revolution in cervical screening and vaccination predicted to eventually eliminate cervical cancer.

RECENT FINDINGS

HPV PCR, patented by the author in 1987, has recently begun to replace cytology for primary cervical screening. I highlight the findings from large randomized clinical trials that have brought about this change, and progress with implementation. Australia was the first to introduce a national, publicly-funded HPV PCR-based program of primary screening, on 1 December 2017. The United Kingdom is set to follow, as are other countries. The widespread preference of self-sampling by under-screened women in particular will increase the effectiveness of population screening when using HPV tests. Coupled with improved vaccination now that more effective (nonavalent) HPV vaccines are being introduced, recent modeling predicts that cervical cancer will be markedly reduced, or even eliminated, in coming decades.

SUMMARY

The recent or pending change to more accurate cervical screening by HPV detection using PCR in various countries means less frequent screening for women. Women with an aversion to having their sample collected by a physician can collect their sample themselves, either at the doctor's rooms or at home, the sample then being mailed to the testing laboratory.

Effect of Conventional and Microwave Tissue Processing Technique on DNA Integrity: A Comparative Molecular Analysis

Background

Methods of diagnostic molecular biology are routinely applied on formalin-fixed, paraffin-embedded tissues processed via conventional method. Recently, there has been a growing interest to use microwave technology in histopathology laboratories to overcome the deficiencies of the conventional processing method. Thefore, this study was aimed to compare and analyze the quality and quantity of DNA obtained from tissues processed by conventional and microwave tissue processing techniques and to further ascertain the applicability of the latter for PCR (polymerase chain reaction based research).

Methods

Thirty fresh tissues of oral squamous cell carcinoma (OSCC) were included, and each sample was cut into two equivalent halves. One tissue half was processed by conventional manual method whereas the other half was processed using a domestic microwave oven. DNA was obtained from all the tissues which were then subjected to Polymerase chain reaction (PCR) to evaluate GAPDH (Glyceraldehyde-3-phosphate dehydrogenase) gene expression.

Results

The results revealed better DNA yield from microwave processed tissue while the quality of the DNA was alike from both the techniques.

Conclusion

On the basis of the results obtained, it can be concluded that DNA produced by microwave processed tissues was similar to that obtained by conventional processing technique in terms of quantity and quality. Thus, microwave processed tissue samples can be successfully used for further molecular studies and researches.

DNA and RNA Isolated from tissues processed by microwave-accelerated apparatus MFX-800-3 are suitable for subsequent PCR and Q-RT-PCR amplification

Over the past decade, methods of molecular biology have appeared in diagnostic pathology and are routinely applied on formalin-fixed, paraffin-embedded histological samples, processed via conventional embedding methods. Due to its reagent- and cost-effectiveness, embedding techniques that utilize microwave acceleration in one or more steps of histoprocessing are increasingly used by numerous laboratories. The demand arises that tissues processed this way should also be suitable for the requirements of molecular pathology. In this study, both conventionally embedded and MFX-800-3 machine-processed tissue samples from the same source were used for isolation of DNA and RNA and for performing PCR and real-time PCR. PCR amplification of the beta-globin gene, as well as the real-time PCR amplification of the ABL mRNA was successful in all cases. Our conclusion is that samples processed by the vacuum assisted automatic microwave histoprocessor MFX-800-3 are perfectly applicable for DNA and RNA isolation and provide appropriate templates for further PCR and realtime PCR studies.

Validation of QF-PCR for prenatal aneuploidy screening in the United States

OBJECTIVE

QF-PCR is an inexpensive and reliable method for aneuploidy screening; however, despite its obvious advantages, it is not in routine use in the United States. Our objective in the present study was to validate QF-PCR as a means for prenatal aneuploidy screening in our institution.

METHODS

A QF-PCR assay using 15 primer pairs located on chromosomes 13, 18, 21 X and Y was established for aneuploidy screening. Amniotic fluid (AF) and chorionic villus sampling (CVS) samples consisting only of the cells recovered from the plasticware discarded by our institutional cytogenetics laboratory were collected and DNA was prepared by a simple and inexpensive microwave procedure. QF-PCR was then performed and interpreted using established criteria.

RESULTS

687 consecutive prenatal samples were screened in a blinded prospective manner, and results were compared to those obtained by conventional cytogenetics. 100% of autosomal trisomies were detected, and there were zero false positives. A single case each of XXY and 45X were missed.

CONCLUSIONS

QF-PCR for prenatal aneuploidy screening was validated in our laboratory and has now been approved by the New York State Clinical Laboratory Evaluation Program. We propose a simple protocol for integrating QF-PCR into the normal cytogenetics laboratory workflow.

Comparison of DNA extraction from cervical cells collected in PreservCyt solution for the amplification of Chlamydia trachomatis

OBJECTIVE

The aim of this study was to compare and evaluate three methods of DNA extraction for the amplification of Chlamydia trachomatis in uterine cervical samples collected in PreservCyt solution. ThinPrep is the trade name for the slide preparation.

METHODS

Thirty-eight samples collected in LCx buffer medium, which were identified as C. trachomatis infected by ligase chain reaction (LCR), were selected for this study. DNA from the PreservCyt samples was extracted by three methods: (i) QIAamp kit, (ii) boiling in Tris-EDTA buffer with Chelex purification, and (iii) Proteinase K digestion with Chelex purification. Sample DNA was tested for the presence of C. trachomatis by PCR using cryptic plasmid research (CTP) primers and major outer membrane protein research momp gene (MOMP) primers. Real-time (LightCycler) PCR for relative C. trachomatis quantification following DNA extraction was performed using primers (Hsp 60) for the 60 kDa heat-shock protein hsp60 gene.

RESULTS

Amplification using CTP primers was the most successful with each of the extraction protocols. Boiling in buffer was the least successful extraction method. QIAamp was the best extraction method, yielding the most positives with both the CTP and MOMP primers. Proteinase K-Chelex extraction gave similar sensitivity to QIAamp extraction with CTP primers but lower for MOMP primers.

CONCLUSIONS

The DNA extraction method must be carefully selected to ensure that larger PCR amplicons can be successfully produced by PCR and to ensure high sensitivity of detection of C. trachomatis. In this study it was found that the QIAamp extraction method followed by PCR with the CTP primers was the most successful for amplification of C. trachomatis DNA.

Detection of vaccinia virus, herpes simplex virus, varicella-zoster virus, and Bacillus anthracis DNA by LightCycler polymerase chain reaction after autoclaving: implications for biosafety of bioterrorism agents

OBJECTIVE

To determine whether autoclaving suspensions of vaccinia virus, herpes simplex virus (HSV), varicella-zoster virus (VZV), and Bacillus anthracis inactivate infectivity of these agents but allow detection of target DNA by LightCycler polymerase chain reaction (PCR).

MATERIAL AND METHODS

Swabs were inserted into tubes containing serial 10-fold dilutions (10(-1) to 10(-5); 500 microL; 6 samples per dilution) of vaccinia virus, HSV, VZV, or a single suspension of 10(8) colony-forming units of B anthracis (2 samples). One half of the samples were autoclaved, and the remainder were not. An aliquot of each not autoclaved sample served as a control for infectivity.

RESULTS

Autoclaving swabs saturated with suspensions of vaccinia virus, HSV, or VZV eliminated the infectivity of these agents; however, DNA was detectable in most autoclaved samples in dilutions of 10(-1) to 10(-4) by LightCycler PCR. All not autoclaved specimens were detected by culture (infectivity) except for VZV and, in most dilutions of 10(-1) to 10(-3), by assay of target DNA by LightCycler PCR. Similarly positive results were obtained for PCR assessment of sporulated B anthracis.

CONCLUSIONS

Standard autoclaving procedures eliminated the infectivity of viruses (and B anthracis), but target DNA was often retained for detection by LightCycler PCR. Current recommendations indicate that the laboratory diagnosis of smallpox virus infection be performed only within Biosafety Level 4 facilities. We suggest that, in addition to the requirement for immediate coordination with public health officials, the federal government consider expanding the existing guidelines for processing these specimens to encourage immediate collection, autoclaving, and testing by LightCycler PCR to differentiate smallpox virus from other dermal pathogens such as HSV and VZV by specific qualified laboratories.

Biotechnical use of polymerase chain reaction for microbiological analysis of biological samples

Since its introduction in the mid-80s, polymerase chain reaction (PCR) technology has been recognised as a rapid, sensitive and specific molecular diagnostic tool for the analysis of micro-organisms in clinical, environmental and food samples. Although this technique can be extremely effective with pure solutions of nucleic acids, it's sensitivity may be reduced dramatically when applied directly to biological samples. This review describes PCR technology as a microbial detection method, PCR inhibitors in biological samples and various sample preparation techniques that can be used to facilitate PCR detection, by either separating the micro-organisms from PCR inhibitors and/or by concentrating the micro-organisms to detectable concentrations. Parts of this review are updated and based on a doctoral thesis by Lantz [1] and on a review discussing methods to overcome PCR inhibition in foods [2].

Microwave antigen retrieval for immunocytochemistry on formalin-fixed, paraffin-embedded post-mortem CNS tissue

Microwave antigen retrieval methods were assessed for a panel of antibodies on formalin-fixed, paraffin-embedded sections from a range of human central nervous system (CNS) tissues taken at post-mortem. The immunoreactivity of a number of antigens (synaptophysin, PGP9.5, GFAP, carbonic anhydrase II, CD68, ferritin, HLA-DR, alpha beta-crystallin, measles and herpes viruses) was markedly enhanced by this procedure compared with other methods of antigen unmasking, such as trypsinization. Enhancement was noted both by an increased number of positive cells and by the intensity of reactions within individual cells and their processes. Furthermore, the microwave method produced uniform immunostaining over large surface area sections with no loss of morphological detail. Large cryostat sections of CNS tissue can be difficult to obtain with good morphology. The ability to retrieve a wide range of antigen in formalin-fixed, paraffin-embedded CNS tissue will greatly increase the range of investigations that can be carried out on this type of stored material.