J O McGee

Episomal and integrated human papillomavirus in cervical neoplasia shown by non-isotopic in situ hybridisation.

It was postulated that non-isotopic in situ hybridisation (NISH) signal types 1-3 for human papillomavirus in cervical biopsy specimens represent episomal or integrated virus. The aim of this study was to validate this hypothesis by independent molecular techniques. Fresh cervical intraepithelial neoplasia (CIN) and squamous cell cancer (SCC) tissue were examined for NISH signal pattern by hybridising with digoxigenin labelled HPV 16. DNA was extracted from the same samples and analysed by restriction endonuclease digestion and Southern blotting to determine the physical state of the viral genome. Six CIN biopsy specimens showed a type 1 NISH signal for HPV 16. On Southern analysis these biopsy specimens contained only episomal HPV 16. Three SCC with a type 2 NISH signal contained integrated HPV 16 by Southern analysis. Two specimens, a CIN 3 and an SCC with a type 3 NISH signal for HPV 16, showed the presence of both episomal and integrated HPV 16 with conventional Southern analysis and two dimensional gel electrophoresis. These results show that episomal HPV can be reliably determined by NISH type 1 signal, integrated HPV by type 2, and a combination of both episomal and integrated HPV, by a type 3 signal in archival paraffin wax embedded cervical biopsy specimens. This will add another variable to the epidemiological studies of HPV infection. In particular, it will now allow retrospective studies to be done to define the role of episomal and integrated HPV in the evolution of cervical intraepithelial neoplasia and other cervical disease associated with this virus.

Interphase cytogenetics using biotin and digoxigenin labelled probes I: relative sensitivity of both reporter molecules for detection of HPV16 in CaSki cells.

This study was undertaken to develop technology for the detection of nucleic acid using two different DNA probe reporter molecules, the ultimate aim being to differentially label two nucleic acids within the same nucleus. Digoxigenin and biotin were used to label DNA probes. The absolute and relative sensitivity of digoxigenin and biotin labelled DNA probes for detecting integrated human papilloma virus 16 (HPV16) was investigated in CaSki cells by non-isotopic in situ hybridisation (NISH). Several methods for the detection of labelled probes were also investigated. The optimal sensitivity of digoxigenin labelled probe was equivalent to that of biotin when alkaline phosphatase was used as the final detector. The median number of discrete viral signals discernible in each cell with the most sensitive detection system was seven to eight with both labelled probes. The average number of HPV16 genomes in each CaSki cell, derived by dot blot hybridisation, was about 270. The calculated absolute sensitivity of NISH for viral detection in this system is complex because of variation of signal size and number. Nevertheless, one signal per nucleus equates to as little as 30 to 40 viral copies, and probably much less. The ability to distinguish up to 15 discrete signals with both digoxigenin and biotin labelled probes in the nuclei of CaSki cells indicates that these methods will be useful in interphase cytogenetics in material routinely fixed in aldehyde.

Interphase cytogenetics using biotin and digoxigenin labelled probes: III. Increased sensitivity and flexibility for detecting HPV in cervical biopsy specimens and cell lines.

A monoclonal antibody to digoxin enabled sandwich techniques to be used for the detection of hybridised digoxigenin labelled probes in cultured cells and paraffin wax sections. This system has greater flexibility than alkaline phosphatase conjugated polyclonal antidigoxigenin antibody and permits the use of alternative detector enzymes, such as horseradish peroxidase and fluorescence labels. The APAAP detection system that does not require the use of biotin can also be used in situations where endogenous biotin is a problem. The low level of background staining combined with precise substrate deposition of the amplified peroxidase system gives higher sensitivity and resolution. This permits localisation of closely adjacent chromosomal loci in interphase nuclei. The most sensitive peroxidase based digoxigenin detection system visualises two and a half to 12 copies of human papillomavirus (HPV) per nucleus. This system is also suitable for the analysis of low copy number HPV infection of cervical tissues.

In situ evidence for HPV 16, 18, 33 integration in cervical squamous cell cancer in Britain and South Africa.

In a previous study three types of HPV signal were described in CIN. It was suggested that a type 1 signal represented episomal HPV while a type 2 signal represented integrated HPV; and a type 3 signal was indicative of both episomal and integrated HPV. To test this hypothesis 91 squamous cell cancers (SCC) of the cervix from Britain and South Africa were examined for HPV 6, 11, 16, 18, 31, 33, 35. Of the South African group (n = 69) 64% contained HPV types 16 (n = 29) and 18 (n = 15). The SCC in the British group (n = 22) contained HPV 16 and HPV 33 in 12 and three cases, respectively. Of the HPV positive biopsy specimens, 86% showed a type 2 signal in keratinising and non-keratinising tumours and the remainder a type 3 signal. Type 3 signal was present only in keratinising tumours. The presence of punctate signal in 100% of HPV containing SCC, together with localisation of HPV signal to sister chromatids in tumour cell mitotic figures in vivo, provides further evidence for type 2, and the punctate component of type 3 signal representing viral integration.

Interphase cytogenetics using biotin and digoxigenin labelled probes II: Simultaneous differential detection of human and papilloma virus nucleic acids in individual nuclei.

A method was developed for the simultaneous detection of viral and human DNA in contrasting colours in routine formalin fixed, paraffin wax embedded biopsy specimens. This was achieved by non-isotopic in situ hybridisation (NISH) with a biotinylated Y chromosome probe and digoxigenin labelled probe for human papilloma virus type 6 (HPV 6). The tissues studied were peripheral lymphocytes, tonsil, and penile warts. The hybridisation signals produced by biotinylated probes were visualised in red using streptavidin peroxidase and those produced by digoxigenin labelled probes as a blue/black colour using anti-digoxigenin alkaline phosphatase. In lymphocytes and tonsil 95-100% of cells had a detectable Y chromosome; in warts only 60-70% of infected keratinocytes near the skin surface had a demonstrable Y chromosome. This suggests that this chromosome is lost or occluded in cell maturation. In simultaneous double hybridisation with both probes, HPV and Y sequences were demonstrable within the same nucleus in penile warts. This technique permits the simultaneous differential detection of two nuclei acid sequences in interphase nuclei and will have application in analysis of putative dual HPV infections and in determining the intranuclear spatial relations between nucleic acids in interphase nuclei.

In situ human papillomavirus (HPV) genotyping of cervical intraepithelial neoplasia in South African and British patients: evidence for putative HPV integration in vivo.

In South Africa asymptomatic wart virus infection diagnosed by morphological criteria occurs in 16-20% of all ethnic groups; the incidence in black women is 66%. To identify human papillomavirus (HPV) types the prevalence of HPV in cervical intraepithelial neoplasia (CIN) in South African women (n = 72) with age matched British women (n = 73) was compared by non-isotopic in situ hybridisation (NISH) using digoxigenin labelled probes for HPV 6, 11, 16, 18, 31, 33 and 35 on archival biopsy specimens. A higher proportion of British biopsy specimens (68%) contained HPV than those from South Africa (50%) in CIN 2 and 3; this difference was due to HPV 16. Thirty six per cent of the positive biopsy specimens from South African women also contained HPV 33/35 compared with 16% in the United Kingdom. There was no difference in HPV detection with age in either group. These data indicate that HPV types vary geographically, with minor HPV types being more common in South Africa. Three qualitatively distinct NISH signals were observed; a diffuse (type 1) signal in superficial cells, mainly koilocytes; a punctate signal (type 2) in basal/undifferentiated cells in CIN 3; and combined type 1 and 2 signals in CIN with wart virus infection (type 3). The punctate signal may represent HPV integration.

Identification of HHV8 in early Kaposi's sarcoma: implications for Kaposi's sarcoma pathogenesis.

AIMS: Kaposis sarcoma is a vascular tumour of uncertain pathogenesis possibly caused by an infectious agent, identified in high risk groups. Accumulating solution phase polymerase chain reaction (PCR) and seroepidemiological data suggest that a previously undescribed herpes DNA virus (human herpesvirus 8 (HHV8)) is the causative agent. Using a unique cohort of early Kaposis sarcoma, the precise cell type infected with HHV8 in such lesions was identified to elucidate further the role of HHV8 in the pathobiology of Kaposis sarcoma. METHODS: Sixteen cases of early Kaposis sarcoma (derived from skin and lymph node) were assessed for the presence of HHV8 using both standard solution phase PCR and TaqMan PCR to the KS330 Bam region of HHV8. In situ amplification was also performed on a selected group in an attempt to identify the candidate infected cells. RESULTS: Using both conventional solution phase and TaqMan PCR, 87% of cases were positive. In addition, HHV8 amplicons were localised in situ to endothelial and spindle cell proliferations in early Kaposis sarcoma. The HHV8 viral load varied from lesion to lesion. CONCLUSIONS: The presence of HHV8 in early lesions supports a role for HHV8 in the pathogenesis of Kaposis sarcoma. Coupled with recent seroepidemiological studies, these results suggest that HHV8 is the aetiological agent of Kaposis sarcoma. Its precise interaction with other factors known to be involved in the development of Kaposis sarcoma, including cytokines and anti-apoptosis genes, requires elucidation.

Non-isotopic detection of in situ nucleic acid in cervix: an updated protocol.

Recently, sensitive non-isotopic in situ hybridisation (NISH) methodology for the detection of human DNA and human papilloma virus (HPV) DNA in archival paraffin blocks of cervix was described. An amended protocol, now used in this laboratory for detection of these genes by NISH is presented. The amendments include the following: protease digestion at 37 degrees C; tissue dehydration in air rather than ethanol; stringency washing in formamide solution; blocking non-specific binding of avidin alkaline phosphatase with a modified buffer; and increasing the concentration of avidin alkaline phosphatase for detecting low abundance DNA. These changes simplify and increase the sensitivity of the protocol such that Y chromosome repeats are visualised in almost all female cells.

HHV8 and Kaposi's sarcoma: a time cohort study.

AIMS: The recent finding that human herpes virus 8 (HHV8) is found in the majority of Kaposis sarcoma (KS) cases supports the epidemiological observation that the tumour may be caused by an infectious agent. This study aimed to address when and how HHV8 evolved. METHODS: A cohort of African endemic KS (49 samples from 45 patients) and European KS (18 samples from 13 patients), spanning 27 years, was assessed for the presence of HHV8 by both standard solution phase polymerase chain reaction (PCR) and the newly described technique of TaqMan PCR. RESULTS: HHV8 was present in approximately 49% (24 of 49 tissue samples) of the African cases and in more than 90% (16 of 18 tissue samples) of the European cohort, in keeping with recent seroepidemiological data. CONCLUSIONS: HHV8 is strongly linked to the development of KS; however, in some patients, other factors may operate. The utility and flexibility of TaqMan PCR in detecting low copy viral target in human tissues was demonstrated.

Model system for optimising mRNA non-isotopic in situ hybridisation: riboprobe detection of lysozyme mRNA in archival gut biopsy specimens.

The aim of this study was to optimise conditions for mRNA detection by nonisotopic in situ hybridisation (NISH) using biotinylated and digoxigenin labelled riboprobes. Because lysozyme gene transcripts are present at high concentrations in Paneth and other alimentary cells, archival gut biopsy specimens were chosen as a model system for these experiments. Most of the variables in NISH, from unmasking of mRNA, to its ultimate detection by peroxidase or alkaline phosphatase based detection systems, were examined in detail. The most important findings were that simultaneous heating of tissue targets and riboprobes at 95 degrees C for 15 minutes before hybridisation at 50 degrees C for two hours gave the most intense signal for lysozyme mRNA in Paneth cells, Brunners glands, and lamina propria macrophages; digoxigenin labelled riboprobes gave a higher signal to noise ratio than their biotinylated counterparts, and probes 600 base pairs long were superior to shorter probes. It is concluded that the mRNA NISH method may be generally useful for detecting gene transcription in archival clinical biopsy specimens.