Molecular cloning and partial nucleotide sequence of human papillomavirus type 1a DNA

Recent Advances in the Search for Antiviral Agents against Human Papillomaviruses

Infection by human papillomavirus (HPV) is extremely common and associated with the development of benign warts or malignant lesions of the skin and mucosa. Infection by a high-risk (oncogenic) anogenital HPV type, most often through sexual contacts, is the starting point of virtually all cases of cervical cancers and the majority of anal cancers. The same viral types are also increasingly being linked with a subset of head-and-neck and non-melanoma skin cancers. Although prophylactic vaccines are now available to protect against the four types most commonly found in cervical and anal cancers (HPV16 and HPV18) and anogenital warts (HPV6 and HPV11), these neither protect against all genital HPVs nor are of therapeutic utility for already infected patients. Thus, the need for antiviral agents to treat HPV-associated diseases remains great, but none currently exist. This article reviews the recent progress made towards the development of antiviral agents to treat HPV infections, from target identification and validation to the discovery of lead compounds with therapeutic potential. Emphasis has been placed on novel low-molecular-weight compounds that antagonize HPV proteins or, alternatively, inhibit cellular proteins which have been usurped by papillomaviruses and are mediating their pathogenic effects.

Complete nucleotide sequencing of an HPV-1a variant and determination of extant errors in the prototype HPV-1a sequence

The complete nucleotide sequence of an HPV-1a variant has been determined. The variant has over 99% nucleotide identity with the prototype HPV-1a sequence, with the majority of mutations occurring in the long control region. Additionally, remaining errors in the prototype HPV-1a sequence are reported.

Characterization of murine polyclonal antisera and monoclonal antibodies generated against intact and denatured human papillomavirus type 1 virions

Human papillomavirus type 1 (HPV1) virions, both as intact virion particles (IVP) and as detergent-denatured virions (DDV), were used to prepare polyclonal antisera and monoclonal antibodies (MAbs) in BALB/c mice. Anti-IVP antiserum contained type-specific HPV1 L2-reactive antibodies and no detectable HPV1 L1-reactive antibodies. Anti-IVP MAbs recognized a linear epitope between L2 amino acids 102 and 108 (PIDVVDP). Anti-DDV antiserum contained type-specific HPV1 L1-reactive and HPV1 L2-reactive antibodies. An anti-DDV MAb recognized a linear epitope between L1 amino acids 127 and 133 (AENPTNY). HPV1a L1- and L2-encoded polypeptides expressed in Saccharomyces cerevisiae and by in vitro translation were equivalent in size to the major and minor virion capsid proteins, respectively.

Alterations in the regulatory region of the human papillomavirus type 6 genome are generated during propagation in Escherichia coli

We analyzed the long control regions (LCRs) of seven human papillomavirus type 6b (HPV-6b) clones, which contained prototype HPV-6b sequences recloned into various plasmid vectors and propagated in different strains of Escherichia coli. Southern blot analysis and DNA sequencing demonstrated three different sequences, each distinct from the published prototype HPV-6b sequence. Two of the plasmids contained insertions of 24 and 94 base pairs (bp) and a 1-bp deletion. Four plasmids contained insertions of 24 and 58 bp and a deletion of 49 bp. One plasmid contained a single insertion of 77 bp. The 94-, and 58-bp insertions occurred at the same site and had 100% positional identity across their shared lengths. All changes were located in the purine-thymidine-rich region of the LCR (nucleotides 7292 to 7400). Two additional LCR sequences were detected by restriction analysis of two other HPV-6b clones. We conclude that the purine-thymidine-rich region of the LCR is a hot spot for recombination in E. coli and that the alterations are the result of recA-independent events. These results emphasize the need to rigorously prove that a cloned isolate is an authentic copy of the genomic DNA present in the original lesion. In addition, the data indicate that the HPV-6b LCR sequences employed in different laboratories may be different, even if their parental DNAs were identical. Finally, we discuss the need for caution in assigning biological significance to alterations in this region, in view of the limited data available on the true identity of the HPV-6b LCR.

Papillomaviruses in human skin warts and their incidence in an Argentine population

Human papillomavirus genomic types present in human warts of an Argentine population were studied. HPV DNA from single warts was obtained using an alkaline extraction procedure that resulted in a clean DNA preparation, which could be analyzed with several endonucleases. This method was used to isolate and insert the HPV DNAs of two genomic types into the Bam HI site of the pBR322 plasmid. Restriction maps of both HPV DNAs were constructed. According to these maps, one of the genomic variations was identical to HPV1a and the other to HPV2a. The incidence of HPV2 and of HPV1 in different types of skin warts was studied by a dot blot hybridization assay. Twenty-two out of 28 common warts were positive for HPV2 and negative for HPV1; four were positive for HPV1 and negative for HPV2 and two were negative for both. Five out of six plantar warts were positive for HPV1, and one was negative for both. Three out of seven filiform warts were positive for HPV2, three were positive for both probes, and one was negative for both. Southern blot analysis of HPV2 positive samples indicated that 80% were HPV2a and 20% another subtype not yet characterized. All plantar warts contained HPV1a. Msp I/Hpa II restriction analysis confirms previous results indicating that HPV1a DNA is partially methylated, while no evidence of methylation was found for HPV2a DNA.

Human papillomavirus type 16 DNA sequence

The complete nucleotide sequence of HPV16 DNA (7904 bp) cloned from an invasive cervical carcinoma was determined. Homology comparisons allowed us to align the major open reading frames with the other published papilloma virus DNA sequences. The general organization of the open reading frames is similar to that of the other four papillomavirus (BPV1, HPV1a, HPV6b, CRPV) already sequenced. The sequence reveals an interruption of the reading frame coding for a suspected E1 protein.

Detection and localization of human papillomavirus DNA in human genital condylomas by in situ hybridization with biotinylated probes

We have examined the distribution of human papillomavirus (HPV) DNA in paraffin sections of humans warts by in situ hybridization with biotin-labeled DNA probes. Recombinant plasmid DNAs (HPV-1, -6, -11, -16) were labeled by nick translation with biotinylated deoxyuridine triphosphate. Paraffin sections were hybridized with the probes for 18 h in stringent or non-stringent conditions, and DNA-DNA hybrids were detected by immunocytochemistry. Paraffin sections of warts were also examined for the presence of HPV capsid antigen with the avidin-biotin peroxidase complex method for immunocytochemistry. HPV DNA was detected and localized in paraffin sections from a plantar wart, a laryngeal papilloma, and seven anogenital condylomas. The specific HPV type present in each lesion was determined by hybridization under stringent conditions with the homologous DNA probe. The papillomas were found to contain many more cells with replicating virus DNA, as demonstrated by in situ hybridization, than was apparent from the number of cells containing detectable virus antigen. In situ hybridization with biotin-labeled probes is an effective technique for the identification of HPV infection in routinely collected and processed tissue specimens.

Uneven distribution of methylation sites within the human papillomavirus la genome: possible relevance to viral gene expression

A homogeneous preparation of human papillomavirus type 1a (HPV-1a) DNA resisted complete cleavage by the methylation-sensitive restriction endonuclease HhaI. Ten fragments additional to those predicted from the known HPV-1a DNA sequence were resolved by agarose gel electrophoresis of the HhaI-cleaved viral DNA. By determining the composite structures of the additional HhaI viral fragments, evidence was found for part-methylation of six of the thirteen HhaI sites. Two of the modified HhaI sites were localized to the 3'-end of the putative early gene region. The other four modified Hha-I sites were situated within the L1 open reading frame of the putative late gene region. Ten successive restriction endonuclease sites occurring close to and within an area of high CG density which surrounds the 5' end of the putative early gene region, were not modified detectably. The possible relevance of DNA methylation to the control of HPV-1a gene expression in epidermal cells is discussed.

DNA sequence and genome organization of genital human papillomavirus type 6b

The complete nucleotide sequence of the circular double-stranded DNA of the genital human papillomavirus type 6b (HPV6b) comprising 7902 bp was determined and compared with the DNA sequences of human papillomavirus type 1a (HPV1a) and bovine papillomavirus type 1 (BPV1). All major open reading frames are located on one DNA strand only. Their arrangement reveals that the genomic organization of HPV6b is similar to that of HPV1a and BPV1. The putative early region includes two large open reading frames E1 and E2 with marked amino acid sequence homologies to HPV1a and BPV1 which are flanked by several smaller frames. The internal part of E2 completely overlaps with another open reading frame E4. The putative late region contains two large open reading frames L1 and L2. The L1 amino acid sequences are highly conserved among analyzed papillomavirus types. By sequence comparison, potential promoter, splicing and polyadenylation signals can be localized in HPV6b DNA suggesting possible mechanisms of genital papillomavirus gene expression.

Molecular cloning and characterization of human papilloma virus DNA derived from a laryngeal papilloma

Papilloma virus DNA from a laryngeal papilloma was cloned in phage lambda L 47 and characterized after cleavage with different restriction enzymes. Hybridization with the DNAs of human papilloma virus types 1, 2, 3, 4, 5, and 8 showed no homology under stringent hybridization conditions. Human papilloma virus type 6 DNA, however, was partially identical to laryngeal papilloma virus DNA; different restriction enzyme fragments hybridizing with the other DNA were identified on each genome. The degree of homology was determined by reassociation kinetics to be 25%. According to the present nomenclature, laryngeal papilloma virus therefore represents a different type of human papilloma virus and is tentatively designated as human papilloma virus type 11. Sequences homologous to laryngeal papilloma virus DNA were also found in four of nine additional laryngeal papillomas. Attempt to detect homologous DNA in 12 carcinomas of the larynx were negative.