Papova virus group

Antiviral Activities of Human Host Defense Peptides

Peptides with broad-spectrum antimicrobial activity are found widely expressed throughout nature. As they participate in a number of different aspects of innate immunity in mammals, they have been termed Host Defense Peptides (HDPs). Due to their common structural features, including an amphipathic structure and cationic charge, they have been widely shown to interact with and disrupt microbial membranes. Thus, it is not surprising that human HDPs have activity against enveloped viruses as well as bacteria and fungi. However, these peptides also exhibit activity against a wide range of non-enveloped viruses as well, acting at a number of different steps in viral infection. This review focuses on the activity of human host defense peptides, including alpha- and beta-defensins and the sole human cathelicidin, LL-37, against both enveloped and non-enveloped viruses. The broad spectrum of antiviral activity of these peptides, both in vitro and in vivo suggest that they play an important role in the innate antiviral defense against viral infections. Furthermore, the literature suggests that they may be developed into antiviral therapeutic agents.

The human polyomavirus BK (BKPyV): virological background and clinical implications

Polyomavirus BK (BKPyV) infects most people subclinically during childhood and establishes a lifelong infection in the renourinary tract. In most immunocompetent individuals, the infection is completely asymptomatic, despite frequent episodes of viral reactivation with shedding into the urine. In immunocompromised patients, reactivation followed by high-level viral replication can lead to severe disease: 1-10% of kidney transplant patients develop polyomavirus-associated nephropathy (PyVAN) and 5-15% of allogenic hematopoietic stem cell transplant patients develop polyomavirus-associated haemorrhagic cystitis (PyVHC). Other conditions such as ureteric stenosis, encephalitis, meningoencephalitis, pneumonia and vasculopathy have also been associated with BKPyV infection in immunocompromised individuals. Although BKPyV has been associated with cancer development, especially in the bladder, definitive evidence of a role in human malignancy is lacking. Diagnosis of PyVAN and PyVHC is mainly achieved by quantitative PCR of urine and plasma, but also by cytology, immunohistology and electron microscopy. Despite more than 40 years of research on BKPyV, there is still no effective antiviral therapy. The current treatment strategy for PyVAN is to allow reconstitution of immune function by reducing or changing the immunosuppressive medication. For PyVHC, treatment is purely supportive. Here, we present a summary of the accrued knowledge regarding BKPyV.

Verrucas. Guidelines for management

Most people will experience infection with human papilloma virus (HPV) at some point in their life. Diagnosis, based on clinical examination, is usually straight forward. Treatment can, however, be challenging. Indications for treatment include pain, interference with function, cosmetic embarrassment, and risk of malignancy. Clearance rates are highest in young, healthy individuals with short duration of infection. Treatment may be with destructive agents (keratolytics, cryotherapy, curettage and cautery, laser, photodynamic therapy), with antimitotic agents (podophyllin, bleomycin, retinoids), with immune stimulants (topical sensitizers, cimetidine), or with topical virucidal agents [formaldehyde (formalin), glutaral (gluteraldehyde)]. As yet, there is no single totally effective treatment for viral warts. Some patients may choose to leave their warts untreated until spontaneous resolution. In those who seek intervention, simple, well tolerated therapies should be chosen initially in preference to more complicated, potentially harmful agents. It is likely that future research will be directed to developing an antiviral agent specific for HPV which would be safe, effective and not prohibitively expensive.

An electron microscope study of the development of SV40 virus

Kidney cells, predominantly from Cercopithecus monkeys but also from baboons, were infected in vitro with the SV40 virus. The infectious cycle was studied with the electron microscope by means of thin sections of cells fixed from 3 hours up to 11 days after infection. The frequency of virus formation and various nuclear and cytoplasmic lesions in relation to the infection are described. The virus particles appear in the nucleus in close contact with the chromatin. In a small number of cells they have been observed as early as 10 to 12 hours after infection, but most often they appear 24 to 48 hours afterward. Their mean diameter is 33 mµ. They have no membrane and are frequently arranged as crystal-like structures. In addition to the appearance of virus, one observes various lesions in the nucleoplasm and particularly in the nucleolus, which shows an early hypertrophy and produces unusual, dense condensations in contact with the nucleolonema. The importance of these nucleolar lesions and the relationship between the SV40 virus and the polyoma, common wart, and Shope papilloma viruses are discussed.

INCOMPLETE SIMIAN PAPOVAVIRUS SV40. FORMATION OF NON-INFECTIOUS VIRAL ANTIGEN IN THE PRESENCE OF FLUOROURACIL

A study was made of the effects of 5-fluorouracil (FU) and 5-fluorodeoxyuridine (FUDR) on the replication of the simian papovavirus SV40 in cercopithecus monkey kidney cells and on the production of virus antigen by these cells. Both drugs markedly suppressed the production of new infectious virus by SV40-infected cells. Synthesis of viral protein was also markedly suppressed by FUDR, but not by FU. In the presence of FU, infected cells produced large amounts of viral protein which were detected by the fluorescent antibody technique. The antigen was not distributed in a particulate fashion as in untreated cells. Diffuse virus antigen was observed in the nuclei of FU-treated cells, resembling the distribution of antigen near the end of the eclipse period in untreated, infected cultures. This stage of antigen production presumably preceded viral assembly. Virus particles with or without cores were rarely seen with the electron microscope in infected FU-treated cells, although large numbers of SV40 particles were readily visualized in untreated, infected cells. It appears that at least one antigenic protein of this papovavirus is synthesized abundantly in FU-treated cells, but is not assembled into virus shells in the presence of the inhibitor.

A LABILE INTRANUCLEAR RNA ASSOCIATED WITH THE DEVELOPMENT OF ADENOVIRUSES

The nucleic acids produced intracellularly during the replication cycles of both DNA and RNA viruses can now be identified rapidly using a sensitized procedure based on staining with the fluorochrome acridine orange. Cellular DNA, viral DNA (both single and double stranded forms), cellular RNA, and RNA arising as a result of viral stimulus can be differentiated. The intracellular development of virus specific DNA, RNA, and protein has been studied in monkey kidney cells infected with adenoviruses types 3 and 7. It has been possible to detect a labile RNA in the nucleus from 16 to 20 hours after inoculation. When the cultures are treated with puromycin at this time, this RNA can be accumulated under certain conditions in the nucleus and demonstrated cytochemically. At the same time the production of specific viral protein as determined by staining with fluorescein-labeled antibodies is markedly inhibited. However, intranuclear double stranded DNA continues to be formed for a time. When puromycin is added to the system early in the eclipse period virus-specific DNA and labile RNA cannot be detected.

Human papillomaviruses (HPV) in gynaecological cytology: from molecular biology to clinical testing

Molecular epidemiological and pathological studies show that different HPV types are associated with different cervical lesions allowing classification of the viruses into types associated with 'high', 'intermediate' and 'low' risk of cervical neoplasia. However, HPV infection often regresses and, where it is associated with neoplasia, is an early event. This suggests that other factors are involved in the carcinogenic process, and there is some mechanistic basis for the interaction of epidemiologically defined factors with HPV infection in the process of cervical carcinogenesis. With the refinement of techniques for HPV detection in clinical material, HPV testing is now a realistic possibility, but how this should be performed and in what clinical situation(s) is still uncertain. Particular areas of interest are: (i) the assessment of patients with borderline cytological changes or mild dyskaryosis; and (ii) the definition of those patients at greater risk of invasive disease. Clinical trials are needed before the utility of HPV testing can be properly assessed.

Human papillomavirus (HPV) infections and their associations with oral disease

More than 65 distinct types of human papillomavirus (HPV) have been identified to date. Several of the HPV types have been proposed as etiologic agents of squamous cell carcinoma. In the oral cavity, HPVs have been found associated with several benign squamous cell proliferations. Evidence from histology and DNA hybridization studies suggests that HPV is also involved in oral carcinogenesis. It is apparent, however, that substantial amount of confusion exists in the diagnosis of oral HPV infections. The keratotic, papillary lesions in the oral cavity are usually small and easily overlooked. The gross appearance of these viral lesions is not distinct enough to be readily diagnosed by the clinicians. Degenerative changes found on oral mucosa frequently simulate koilocytosis. Thus, caution should be exercised to avoid overdiagnosis of HPV infection in the oral cavity. The present review summarizes the current evidence available on HPV infections in general and on oral HPV infections in particular. The diagnostic techniques available as well as the problems encountered in the distinction of these lesions are also discussed in short.

The capsid of small papova viruses contains 72 pentameric capsomeres: direct evidence from cryo-electron-microscopy of simian virus 40

The three-dimensional structure of the simian virus 40 capsid is remarkably similar to the structure of the polyoma empty capsid. This similarity is apparent despite striking differences in the methods used to determine the two structures: image analysis of electron micrographs of frozen-hydrated samples (SV40 virions) and an unconventional x-ray crystallographic analysis (polyoma empty capsids). Both methods have clearly resolved the 72 prominent capsomere units which comprise the T = 7d icosahedral capsid surface lattice. The 12 pentavalent and 60 hexavalent capsomeres consist of pentameric substructures. A pentameric morphology for hexavalent capsomeres clearly shows that the conserved bonding specificity expected from the quasi-equivalence theory is not present in either SV40 or polyoma capsids. Determination of the SV40 structure from cryo-electron microscopy supports the correctness of the polyoma structure solved crystallographically and establishes a strong complementarity of the two techniques. Similarity between the SV40 virion and the empty polyoma capsid indicates that the capsid is not detectably altered by the loss of the nucleohistone core. The unexpected pentameric substructure of the hexavalent capsomeres and the arrangement of the 72 pentamers in the SV40 and polyoma capsid lattices may be characteristic features of all members of the papova virus family, including the papilloma viruses such as human wart and rabbit papilloma.

Identification of proteins encoded by the L1 and L2 open reading frames of human papillomavirus 1a

The human papillomavirus 1 (HPV-1) virion is composed of two virally encoded proteins: a 57,000-molecular-weight polypeptide (57K polypeptide), which is the product of the L1 open reading frame (ORF), and a 78K polypeptide, which is derived from the L2 ORF. The 57K (L1) product, which represents the major structural component, appears to be disulfide cross-linked in virus particles. The 78K (L2) protein is a minor component of the virion and does not appear to be disulfide linked either to the L1 gene product or to itself. Analysis of virus particles banding at different buoyant densities revealed differences in the L2 content of heavy-full and light-full virions. Antiserum prepared against a bacterially expressed fragment of the L1 ORF was found by immunofluorescence to cross-react with HPV-2 and bovine papillomavirus 1 virions in wart sections. No cross-reactivity was observed with antisera prepared against either the N- or C-terminal halves of the L2-encoded protein. Similarly, antisera prepared against purified virus particles (disrupted and nondisrupted) reacted only with an expressed fragment of the L1 ORF and not with either L2-encoded polypeptides or proteins derived from the E1, E2, E4, E6, or E7 ORFs. This indicates that the L1 protein contains the papillomavirus common antigens.

Microbial oncogenesis

For more than a century, medical investigators have sought to incriminate microorganisms in the cause of cancer. The first scientific evidence of such a relationship came in 1911, with the first successful induction of a tumor using a cell-free extract. Since that time, considerable data have accrued linking retroviruses, herpes viruses, the hepatitis B virus, papovaviruses, and adenoviruses to various malignant neoplasms. There is also increasing evidence that certain bacteria and parasites participate as cofactors in the development of some cancers. Although proof of cause-and-effect relationships has been difficult to obtain, there can be little doubt that microorganisms occasionally play pivotal roles in the origin of some cancers. Whether attempted intervention against these cancers is best directed against the oncogenic microorganisms themselves or against other environmental cofactors is not yet clear. Nevertheless, the successful application of tumor vaccines in the prevention of Marek's disease in chickens and in modifying the outcome of oncogenic herpesvirus infections in nonhuman primates offers hope of at least limited application of microbial vaccines in the prevention of human cancer.

Human papillomavirus in cervical condylomata. An immunohistochemical study

Twenty-seven cervical condylomata were studied by morphological and immunohistochemical methods (peroxidase-antiperoxidase technique according to Sternberger, with some modifications). The antiserum was obtained from rabbits immunized by human papillomavirus virions; 37% of condylomata stained positively and the koilocytotic cells showed a dark brown nuclear stain. This technique, not particularly useful for diagnostic purposes, could be employed to obtain better understanding of the natural history of these cervical neoplasias.

The primary structure and genetic organization of the bovine papillomavirus type 1 genome

The complete nucleotide sequence of the doubt-stranded circular DNA of bovine papillomavirus type 1 (BPV-1) was determined. Analysis of this sequence in conjunction with known transcriptional data for the virus provides a basis of determining the organization of the papillomavirus genome. All the major open reading frames are located on the same DNA strand. The region transcribed in BPV-transformed cells contains open frames in all three translational frames whereas the region transcribed in productively infected bovine fibropapillomas is characterized by two large open reading frames partitioned by a single translational stop codon. The localization of sequences diagnostic of promoters and polyadenylation sites suggests that splicing is involved in the biosynthesis of the viral mRNAs. A sequence comparison indicates the genome organization of the bovine papillomavirus and that of the members of the simian virus 40-polyomavirus subgroup to be distinct, suggesting that these two groups of viruses are evolutionarily unrelated.

Progressive multifocal leukoencephalopathy in a patient with Hodgkin's disease

This is a report on a 78-year-old patient with Hodgkin's disease of mixed cell type in stage III B, who, because of his age, underwent only mild cytostatic therapy. Two months after beginning of treatment, cerebellar neurological symptoms developed. He died of bronchopneumonia 3 months later. At autopsy progressive multifocal leukoencephalopathy with multiple demyelinated areas in the cerebellum was established. Paracristallinic structures within nuclei of glial cells resembling papovavirus formations were detected by electron microscopy.

Condylomatous epithelial changes in the uterine cervix and their relationship to cervical carcinogenesis

Two hundred twenty-six (226) women with histologically verified dysplastic or neoplastic epithelial lesions in the uterine cervix were assessed for the presence (CO-series) or absence (N-CO-series) of the three newly established types of condylomatous lesions. Both the CO-series and the N-CO-series comprised 113 patients. Histologic changes fulfilling the previously outlined criteria of the (a) flat, (b) inverted and (c) papillomatous condylomas were found in association with all degrees of epithelial atypia, from mild dysplasia to frankly invasive carcinoma. The flat type was most common, comprising 69% of all condylomas. The inverted and papillomatous types were relatively rare, with frequencies of 18.6% and 12.4%, respectively. The mean age of the patients in the CO-series was 30.9 years, that of the N-CO-series patients was 39.3 years (p less than 0.0001). The causal relationship between the cervical condylomas and cervical carcinoma is discussed. The conclusion is drawn that this possibility needs to be seriously considered when searching for a venereally transmitted agent as an etiologic factor of cervical carcinoma.

Studies on the role of C-type viruses in the development of epithelial tumors induced with DMBA

Epithelial tumors were induced using 0.5 per cent solution of DMBA in two strains of mice--one infected with leukoviruses (Swiss mice), and the other is free of these viruses (hairless mice). Tumors from 15 mice of each strain were examined light- and electron-microscopically. Depending on the period of administration of the carcinogen, benign growths of the type of papilloma or keratoacanthoma were obtained, or malignant tumors. In the tumors in Swiss mice electron microscopy revealed a distinct increase in the numbers of viruses in comparison with surrounding skin and intact skin of healthy mice of this strain. In spite of certain histologic differences between tumors produced in Swiss and hairless mice, the results argue against a role of leukoviruses in the pathogenesis of experimentally induced epithelial tumors in mice.

Ultrastructural features of human juvenile laryngeal papillomas

The ultrastructural organization of 12 juvenile laryngeal papillomas was investigated. Four patients were more than 40 years old but had carried the disease since childhood. The other 8 patients were 2-10 years old and had carried the disease from 1-5 years. There is regularly observed a discontinuity of the basement membrane and the basal cells of ten exhibit abundant cytoplasmic processes. In the stratum spinosum there is often found glycogen-like inclusions as well as Odland bodies and keratohyalin granules. In the superficial layers there are nuclear remnants as in parakeratosis. Virus-like particles of a diameter around 330 A have been demonstrated in a disintegrated superficial cell. The scarcity of such particles is discussed with possible regard to a transformation occurring in the superficial layers of the papilloma and to the high shedding rate of the surface cells.

Intranuclear inclusions in a case of Creutzfeldt-Jakob disease: an ultrastructural study

Two types of intranuclear inclusions were described in a brain biopsy from a patient with Creutzfeldt-Jakob disease. The first type of intranculear inclusion was papova virus-like and was observed within 20% of the nuclei of all astrocytes and neurons examined. The particles measured 32 nm in diameter and consisted of a dense core surrounded by a multi-layered shell. The second type of intranuclear inculsion was a granulo-fibrillar nuclear body found within the nuclei of astrocytes and neurons. The possible significance of these inculsions to the etiology of Creutzfeldt-Jakob disease is discussed.

Simian virus 40-host cell interactions. II. Cytoplasmic and nucleolar accumulation of simian virus 40 virion protein

We have used immunofluorescence in parallel with transmission and scanning electron microscopy to characterize the unusual cytoplasmic and nucleolar accumulation of Simian virus 40 (SV40) virion protein (C antigen) at restrictive temperatures (39 to 41 C) in monkey cells infected with a temperature-sensitive mutant of SV40 defective in virion assembly, tsB11. Cytoplasmic and nucleolar accumulation of C antigen did not occur in wild-type-infected cells at any temperature. Wild-type- and tsBll-infected cells were not distinguishable at 33 C by immunofluorescence or electron microscopy. Temperature-shift experiments using metabolic inhibitors of DNA (cytosine arabinonucleoside, 20 mug/ml), RNA (actinomycin D, 5 mug/ml), and protein synthesis (cycloheximide, 2 x 10(-4) to 10 x 10(-4) M) were used to investigate the requirements for ongoing DNA, RNA, and protein synthesis in the distribution of virion protein between the nucleus, nucleolus, and cytoplasm. The transport of C antigen from the nucleolus and cytoplasm into the nucleus was complete after a temperature shift-down (41 and 39 to 33 C). Limited virus particle formation occurred after the shift-down in the presence of actinomycin D and cycloheximide, indicating some of the 39 to 41 C synthesized virion protein could be used for capsid assembly at 33 C in the absence of further virion protein synthesis. Nucleolar and cytoplasmic accumulations of C antigen occurred in the absence of drugs after a shift-up (33 to 39 C and 41 C) indicating a continuous requirement for the tsB11 mutant function. Furthermore, the virion protein synthesized at 33 C remained confined to the nucleus when the cells were shifted to 39 and 41 C in the presence of actinomycin D or cycloheximide. In the presence of cytosine arabinonucleoside, however, the virion protein accumulated in large aggregates in the nucleus and nucleolus after the shift-up, but did not migrate into the cytoplasm as it did in drug-free tsB11-infected control cells. Colchicine (10(-3) M) had no effect on the abnormal accumulation of C antigen during shift-up or shift-down experiments suggesting that microtubular transport plays little if any role in the abnormal transport of tsB11 virion protein from cytoplasm to nucleus. Although virus particles were never observed by electron microscopy and V antigen was not detected by immunofluorescence at 39 or 41 C in tsB11-infected cells, dense amorphous accumulations were formed in the nucleoli and cytoplasm. We suggest that the tsB11 function is continuously required for the normal transport of SV40 virion protein between the cytoplasm, nucleolus, and nucleus and for the assembly of capsids and virions. Several possible mechanisms for the altered tsB11 function or protein are discussed. One of the virion proteins may also be involved in some presently undetermined nucleolar function during SV40 productive infection.