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International audience; Viruses have been considered for a long time as by-products of biological evolution. This view is changing now as a result of several recent discoveries. Viral ecologists have shown that viral particles are the most abundant biological entities on our planet, whereas metagenomic analyses have revealed an unexpected abundance and diversity of viral genes in the biosphere. Comparative genomics have highlighted the uniqueness of viral sequences, in contradiction with the traditional view of viruses as pickpockets of cellular genes. On the contrary, cellular genomes, especially eukaryotic ones, turned out to be full of genes derived from viruses or related elements (plasmids, transposons, retroelements and so on). The discovery of unusual viruses infecting archaea has shown that the viral world is much more diverse than previously thought, ruining the traditional dichotomy between bacteriophages and viruses. Finally, the discovery of giant viruses has blurred the traditional image of viruses as small entities. Furthermore, essential clues on virus history have been obtained in the last ten years. In particular, structural analyses of capsid proteins have uncovered deeply rooted homologies between viruses infecting different cellular domains, suggesting that viruses originated before the last universal common ancestor (LUCA). These studies have shown that several lineages of viruses originated independently, i.e., viruses are polyphyletic. From the time of LUCA, viruses have coevolved with their hosts, and viral lineages can be viewed as lianas wrapping around the trunk, branches and leaves of the tree of life. Although viruses are very diverse, with genomes encoding from one to more than one thousand proteins, they can all be simply defined as organisms producing virions. Virions themselves can be defined as infectious particles made of at least one protein associated with the viral nucleic acid, endowed with the capability to protect the viral genome and ensure its delivery to the infected cell. These definitions, which clearly distinguish viruses from plasmids, suggest that infectious RNA molecules that only encode an RNA replicase presently classified among viruses by the ICTV (International Committee for the Taxonomy of Viruses) into families of Endornaviridae and Hypoviridae are in fact RNA plasmids. Since a viral genome should encode for at least one structural protein, these definitions also imply that viruses originated after the emergence of the ribosome in an RNA-protein cellular world. Although virions are the hallmarks of viruses, viruses and virions should not be confused. The infection transforms the ribocell (cell encoding ribosomes and dividing by binary fission) into a virocell (cell producing virions) or ribovirocell (cell that produces virions but can still divide by binary fission). In the ribovirocell, two different organisms, defined by their distinct evolutionary histories, coexist in symbiosis in the same cell. The virocells or ribovirocells are the living forms of the virus, which can be in fine considered to be a living organism. In the virocell, the metabolism is reorganized for the production of virions, while the ability to capture and store free energy is retained, as in other cellular organisms. In the virocell, viral genomes replicate, recombine and evolve, leading to the emergence of new viral proteins and potentially novel functions. Some of these new functions can be later on transferred to the cell, explaining how viruses can play a major (often underestimated) role in the evolution of cellular organisms. The virocell concept thus helps to understand recent hypotheses suggesting that viruses played a critical role in major evolutionary transitions, such as the origin of DNA genomes or else the origin of the eukaryotic nucleus. Finally, it is more and more recognized that viruses are the major source of variation and selection in living organisms (both viruses and cells), the two pillars of darwinism. One can thus conclude that the continuous interaction between viruses and cells, all along the history of life, has been, and still is, a major engine of biological evolution.

We identified a group of chronically HIV-1-infected patients in whom viral replication is spontaneously controlled without antiretroviral treatment. These patients account for less than 1% of HIV-infected patients. They are defined according to a virological definition: plasma viral load less than 400 copies RNA/ml in more than 90% of the samples tested and HIV positive serology known for more than 10 years. They should never have received antiretroviral therapy. The CD4 T cell count is not taken into account, which differenciate these patients from long-term non progressors. Fifteen patients HIV controllers have been studied in a preliminary work with two main results: i) the demonstration of a strong HIV-specific CD8 immune response and ii) the amount of viral DNA in PBMCs is very low and stable along the time. The aim of the ANRS EP36 study group is to precize the immunological and virological characteristics of these patients. First data seem to confirm an essential role of CD8 T cells to control viral replication, the absence of defective virus, and a normal susceptibility of the CD4 T cells from these patients to the infection with various HIV strains. This group of patients is homogeneous and its study supports physiopathological studies. To go further, a national survey of these patients has been set up to allow future study.

The construction of recombinant vaccinia viruses (VV) is definitely a promising approach to develop vaccines for pets. To produce safer VV recombinant vaccines, it is necessary to understand the pathogenesis of VV infection. The goal of this study was to compare the biological properties of the extracellular and intracellular infectious particles of VV. Four biological properties were investigated: (i) the binding into cellular receptor(s); (ii) the mechanism of entry; (iii) the resistance to neutralisation by antibodies; (iv) the resistance to complement lysis. The results obtained in this study emphasize the differences existing between the two infectious forms of VV and demonstrate the adaptation of the extracellular particle to its role of virus dissemination in vivo. The results of this study implicate that VV strains used as expression vector in vaccinology should be deleted for genes required for EEV morphogenesis.

Six Rhesus macaques were hyperimmunized with either live infectious human immunodeficiency virus type 1 (HIV-1) or with beta-propiolactone--or formalin--inactivated HIV-1. The virus used was HIV-1 BX08, a primary virus isolate grown in human PBMC. Instead of eliciting virus-neutralizing antibodies, this regimen induced antibodies that enhanced HIV-1 infectivity for PBMC by 10 to 90 fold. Enhancement was also seen in a cell-to-cell fusion assay using a Semliki Forest virus replicon to express BX08 gp160 in CD4+, CCR5+ HeLa cell cultures. These observations raise the concern that whole virus particles-based HIV-1 vaccines might elicit enhancing antibodies that could play a facilitating role in the transmission and/or evolution of the disease.

Rotaviruses represent 80% of recognized viral etiologies and 140 million cases of diarrhea per year. They strike young children with similar frequency throughout the world, but the mortality rate is high in developing countries only, with some 870,000 deaths per year (WHO, 1997). Rotaviruses belong to the family of Reoviridae; they are segmented bicatenary RNA viruses, which explains their genetic variability, the presence of mixed infections, the establishment for some time already of a molecular epidemiology by electrophore types. The viruses are "naked" and thus resistant to the outside environment; their massive elimination, 10(8) to 10(10)viral particles per gram of faeces, begins with the first day of diarrhea. They are found in used water and can also be concentrated by shellfish; the environment thus constitutes a notable reservoir for the virus. Oral-faecal transmission is facilitated by deficient sanitary conditions. The 11 fragments of the genome each codify for 1 viral protein; 2 surface proteins, VP4 and VP7, bring about the formation of neutralizing antibodies, which are important for the protection and determination of different serotypes. A non structural protein--NSP4--would seem to intervene in the cytopathogenic effect and may act as a veritable viral enterotoxine. Numerous animal species are infected by rotaviruses which are district from the human ones. The pathology as it affects animals is of economic importance and of interest as an experimental and vaccinal model. Between human and animal rotaviruses there can be genetic rematchings and the VP6 protein is an antigen common to the group. The description of the other viruses responsible for diarrhea has benefited from widespread use of electronic microscopes from the very first years of study of rotaviruses. These other viruses belong to 6 different types: adenovirus, calcivirus, astrovirus, Norwalk agent and related viruses, coronavirus, enterovirus. They therefore have a structural and antigenic polymorphism but, except for the coronavirus, they are all "naked" virions with resistance in outside environments and means of transmission analogous to the rotaviruses. Clinical signs of viral gastroenterites, the age of the patient and epidemiological circumstances help in making an etiological diagnosis; the biological diagnosis has been simplified for the rotaviruses and the adenoviruses. Epidemics related to food, or of hydric and nosocomial origin, especially those due to the Norwalk agent, are under-declared and more frequent than those of bacterial origin. The prevention of dangers related to faeces, the improvement of sanitary conditions, health education, and better nutrition contribute to rotavirus prevention, but rotavirus diarrheas, the incidence of which is similar in developed and developing countries, would be more efficiently controlled through vaccination.

Hepatitis C virus (HCV) is the main etiologic factor of post-transfusional and sporadic hepatitis, called non-A non-B in the past. These infections are characterized by a very high number of chronic carriers always with a persistent viral increase, but often at a slow pace. The seriousness of liver disease differs from one individual to another, varying from an asymptomatic form with minor or no liver injuries, to cirrhosis and hepatocellular carcinoma. Physiopathological mechanisms involved in liver injuries are still poorly understood. The direct role of immune response and of possible genetic factors is still under study. This review aims at summing up the discovery of HCV, its structure, and its variability in the various genome regions in the same individual and from one individual to another. The different methods and techniques to analyze this variability are also reviewed, as well as the various suggested ways of classifying the different types. The geographical distribution and both clinical and biological consequences of this variability are also discussed.

Oral hairy leukoplakia is a disease of the oral mucosa occurring almost exclusively in HIV-infected (mostly AIDS) patients and due to the opportunistic development of Epstein-Barr virus (EBV) within the oral epithelium. Clinically, it shows as whitish patches with a shaggy surface occurring on the lateral margins of the tongue, less frequently the buccal and labial mucosa or the soft palate. Histologically, it comprises parakeratotic hyperkeratosis, acanthosis and numerous koilocytoid cells within the stratum spinosum, i. e. cells with a pycnotic nucleus surrounded by a clear halo and pale-staining cytoplasm. Electronmicroscopy readily shows abundant Herpes-group viral particles within the upper epithelial layers. By immunohistochemistry, in situ molecular hybridization and Southern-blot EBV antigens and DNA have been demonstrated within the lesions whereas HPV and HIV are generally undetectable. In the present work we studied by light- and electronmicroscopy lesions from 8 HIV-seropositive individuals that fulfilled the clinical and histological criteria of OHL. Ultrastructural examination showed the presence in all cases of Herpes-type virions, which, in two of the cases studied by immunohistochemistry, proved to belong to the EBV. It is concluded that electronmicroscopy is a sufficiently sensitive examination to confirm the diagnosis of OHL suggested in the presence of an appropriate clinico-histological setting.

Viral particles can be visualized by electron microscopy using negative staining. Such an approach, widely used in research, provides a method for detecting virions which are present in clinical specimens. It is considered to be the method of choice in cases with suspicion of smallpox. Direct visualization has been systematically applied for the diagnosis of viral diseases in dermatology. Negative staining by pseudoreplication appears to be simple, rapid and efficient. It was thus possible to detect viruses in vesicle fluids, in scrapings and in crusts. During the course of this study 66 cases have been analyzed and viruses have been demonstrated in 49. If a skin lesion seems to be of viral origin, direct examination may confirm the clinical impression.

The two-dimensional immunoelectrophoresis has been applied to human adenovirus type-2 structural analysis. This method is both qualitative and quantitative and was used in the following studies. 1) Detection of major and minor capsid antigens. 2) Identification of viral antigenic components in the infected cell material. 3) Quantification of antigens and serological characterization of ts mutants. 4) Identification of polymeric forms of structural proteins. 5) Assembly analysis of capsid subunits. 6) Stoichiometric analysis of proteins within the virion. 7) Obtaining of monospecific sera.

In considering HCMV antigens one must take into consideration not only structural proteins of virus particles but also HCMV specific proteins associated with the infected cell, for all of these proteins may play a part in eliciting an humoral and/or cell-mediated immune response in the infected individual. The virion is composed of some 35 polypeptides ranging in molecular weight from 12 000 to more than 200 000 daltons (Table I). Viral polypeptide synthesis at the level of the infected cell occurs in three waves, the immediate early, the early and the late (Table II). During the immediate early and early phases a dozen polypeptides appear. Two glycoproteins appear during the early period but these are poorly represented in the virion. Many antigens have been described both in the cytoplasm and nucleus during these periods (Table II). Viral DNA synthesis marks the beginning of the late phase of virus replication. Many new proteins and glycoproteins appear but not all of them will become part of the virus particle (Table II). It is interesting to compare the kinetics of appearance of antibodies as detected by different serodiagnostic techniques, at the time of primary infection, with the location of the antigens which these antibodies detect in the infected cells (Table III). CMV-IgM, the first antibodies to be detected, react with late appearing intracellular nuclear inclusion antigens. This contrasts with the relatively long time required for the development of neutralizing antibodies which react with antigens accessible not only on the viral envelope and at the infected cell membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

Electron microscope studies showed a high production of melanosomes and viral particles budding into the cisternae of the endoplasmic reticulum in cells derived from a subcutaneous metastasis. The history of this subline (HM6B-A) has been summarized elsewhere. An amelanotic subline (provided by the same patient) did not show similar virus particles. When infected with a vesicular stomatitis virus (VSV) thermolabile mutant (tl), these cells produced a VSV pseudotype in which a thermosensitive antigen was modified. Modification of surface VSV antigens was also detected by neutralisation tests. Using these tests, the VSV-pseudotype particles could be used as a tool to detect one or more antigens to a "putative" human melanomavirus, which might be only partially expressed.

Simian adenovirus 7, either complete virus or its capsid subunits, agglutinates Rat (Sprague-Dowley) red blood cells in the presence of heterotypical antiserum. Haemagglutination takes place at 4 degrees C and room temperature. The antigen could not be eluted and its haemagglutinin properties are heat-stable. The reaction is specific. It is inhibited by homologous antiserum only. This property and its characteristics permit a camparison of this strongly oncogenic adenovirus to the human adenovirus of subgroup III of Rosen.

Canine infectious laryngotracheitis virus, an adenovirus designated CAV-2, induces numerous changes in the nucleus and cytoplasm of canine kidney cells (MDCK). The following features could be observed on ultrathin sections examined in the electron microscope: a shift of the nucleolus towards the nuclear membrane and a compression of the latter by the virus particles; the release of virions into the cytoplasm following the tearing or evagination of the nuclear membrane; the attachment of virus particles onto the numerous microtubules of the infected cell. Microfilaments appear to be involved into the vectorial movement of virus particles towards the cytoplasmic membrane in the final phase of infection.

Regardless of the duration of the culture period, the amount of both glycoprotein G and sialic acid bound to the rabies virion as not modified. The major proteins of the viral suspension were the same proteins as those of the virion, except one glycoprotein (MW 70,000).

Whilst practising routine controls with an electron microscope on NIL 2 cell cultures infected by the rabies virus, the occasion arose to reveal certain features of the morphogenesis of this virus and the particular action of glutaraldehyde which alters the aspect of the rabies virus. During the cultures, we witnessed, in succession, the production of morphologically normal virions, then progressively degraded virions whilst the cells recover and develop towards a chronic infection state. Glutaraldehyde treatment of the suspensions proved to be of great interest for electron microscopy observation.

The present study was undertaken with purpose to investigate the relationships between intraepithelial proliferations of malpighian mucosa and the presence of group specific papilloma virus antigens. The investigations allowing to give viral types or subtypes, the hybridization technics, are very heavy and not disponible in routine practice. The detection of widely distributed genus specific HPV antigen using PAP immunohistochemical labeling in different lesions and their association with displastic or neoplastic processes is presented. Only few studies were performed on oral mucosal proliferations, showing the association of these viral proteins with papillomatous or condylomatous lesions. Our work is directed towards the identification of the HPV antigens in more advanced lesions and in the mucosal epithelium surrounding and perhaps preexistent with the buccal cancer.