6th Conference Program (Greek)
Created & Hosted
by HR-Net
Hellenic Virology
Volume 2, Number 1, 1997
Abstracts
- New technology anti-viral vaccines in veterinary medicine
S.K. Kritas (1), G. Koptopoulos (2), O. Papadopoulos (2), S.C. Kyriakis (1), D. Migos (3) - Water-borne plant viruses
P.C. Panayotou - Mechanisms of action of antiviral drugs and strategy approaches for the control of viral infections
E. Biziagos - Production of an inactivated rabies vaccine for animals in cell culture
O. Mangana-Vougiouka (1), E. Reboutzakou (2), K. Nomikou (1), A. Seimenis (3) - IgG avidity against viral capsid antigen of Epstein-Barr virus in infectious mononucleosis
K. Themeli-Digalaki, M. Economou, Ch. Koutsia-Karouzou - Seroprevalence of HHV 6 in the healthy population and in patients with fever of unknown origin
P. Karaboyia-Karafilidis, H. Vayiakou-Voudri, Chr. Kakari-Tsiropina, H. Kafkoula, C. Karakatsani-Polychronopoulou - New approaches of cell culture in virology
M. Ferrari, M.N. Losio
(1) Clinic of Medicine and (2) Laboratory of Microbiology and Infectious Diseases, Faculty of Veterinary Medicine, University of Thessaloniki, Thessaloniki 540 06 and (3) National Drug Administration, 284 Mesogion Avenue, Holargos 155 62 Athens
Hellenic Virology, 1997, 2(1): 7-17.
In this study, the current knowledge on the genetically engineered veterinary vaccines, mainly based on the state of the art of Aujeszky's disease virus of pigs, is reviewed. General basic information on the interactions between the virus and the host cell, as well as the genetic basis of virulence are presented in order to understand the genetic manipulations for vaccine production. Information is given on vaccines based on virus mutants deleted in non-essential proteins. These marker vaccines are used worldwide mainly in Aujeszky's disease eradication programs. Special reference is also made on the non-spreading live vaccines based on the deletion of essential viral proteins. Vector vaccines constructed by genetic recombination techniques are represented in veterinary practice bu vaccinia vectored rabies vaccines for the eradication of this disease from wildlife animals in Europe. The most exciting approach to vaccination with genetic material, the genetic immunization, is also reviewed. Finally, the latest developments on the feline leukemia virus vaccines are given. An attempt to describe the advantages and drawbacks of each vaccine group is made.
National Agricultural Research Foundation, Heraklion, Crete
Hellenic Virology, 1997, 2(1): 18-30.
During the last two decades, successful progress was made in the study of human, animal and plant water-borne pathogenic viruses. Recent research results have enriched our knowledge on the ways the water-borne plant virus diseases are spread and distributed. According to these methods, a large number of plant viruses are transmitted to great distances by surface water, ie rivers, creeks, lakes, irrigation or drainage water, while plant viruses were also detected in ground water, ie deep wells and springs. Finally, there are reports of plant virus isolations from the sea. Water-borne viruses are highly infectious and readily transmitted by manual inoculations. They have stable particles, a wide host range and a high concentration in plant tissues, particularly in root tissues. Although they do not have aerial vectors, their geographical distribution is worldwide. They belong to a rather restricted number of taxonomic units, ie families and genera. These water-borne plant viruses are protected by being aggregated or absorbed into organic and/or inorganic soil complexes and keep their infectivity. They can infect susceptible plants directly through the roots as the water moves downwards. Besides the already identified viruses, new viral entities have been isolated in regard to their pathogenicty and their host range. It remains to be seen if these viruses originate from forests and whether and to what extent they contribute to the forest decline in Europe and elsewhere as predisposing factors. There have also been reports of isolation of plant viruses from the sea. Particles of certain stable viruses have been detected at the outlets of sewage plants after biological treatment of infective faeces and excreta. These viruses derive from the consumption of virus-infected symptomatic or asymptomatic raw fruit and vegetables and they remained unharmed after passing through the alimentary tract and the subsequent dispersal into surface water. Migrating animals and birds are also implicated in the spread of viruses. Several human activities may create some practical problems connected with the dissemination and the spread of viral plant diseases. Such activities may be: (1) use of unsuitable fresh water for irrigation purposes, (2) use of semisolid and dried sludge by-products in agriculture, (3) consumption of raw virus-infected fruit and vegetables imported from distant areas, (4) unsuitability of liquid manure and dung for fertilization and (5) heaps of unsold or withdrawn fruit and vegetables which often build-up a potential source of infection.
Virology Laboratory, Diagnostic & Therapeutic Center, Rethymnon, Crete
Hellenic Virology, 1997, 2(1): 31-44.
Current antiviral chemotherapy is based on the virus life cycle and on the determination of potential targets during the various phases of this multiplication cycle. The development of specific antiviral drugs that are minimally toxic to normal cells has ushered in a new era of antiviral therapy. In theory, antiviral drugs work by interacting directly with the virus, with a viral-encoded enzyme or other protein or with a cellular receptor or factor required for viral replication or pathogenesis. In practice, the viral enzymes and proteins that affect the assembly of the virus have been the effective molecular targets of antiviral treatment to date. An understanding of the ways in which antiviral drugs can interact with viral or cellular factors is a necessary prelude to the development of safe and effective antiviral drugs. By knowing how antiviral agents act at a molecular level, we can create better and safer drugs, avoid conflicting actions of drugs, and improve the synergistic effects of drug combinations. Much of the progress is due to the definition of structure-function relations. By exploiting virus-specifc events, drug designers have produced agents that are not unacceptably toxic to the patient despite the obligate intracellular location of the virus and its dependence upon host cell metabolic functions. The general assumption that in their replicative cycle viruses strictly follow the normal metabolic pathways of the cell and that it would be impossible to block virus replication without affecting normal cell metabolism is no longer tenable. In recent years, it has become increasingly evident that viruses and virus-infected cells exhibit some characteristics which are quantitatively or qualitatively different from normal uninfected cells. These differences are most clearly shown by the herpesviruses, which are capable of inducing a wide variety of specific enzymes (ie thymidine kinase, DNA polymerase, 3'5'-exodeoxyribonuclease, ribonucleotide reductase and dUTP pyrophosphatase) that are either absent from the uninfected cell or fundamentally different from their normal cellular counterparts. By virtue of a broadened substrate specificity, virus-induced enzymes like the herpesvirus-encoded thymidine (deoxycytidine) kinase may recognize as substrate thymidine and deoxythymidine analogues which are not recognized as a substrate by the cellular kinases and thereby restrict their phosphorylation and antiviral action to the virus-infected cell. Other specific events that occur only in virus-infected cells and could therefore serve as appropriate targets for the action of antiviral substances are: (i) viral adsorption with subsequent fusion of the virions with the cell membrane, as required for virus penetration and release, (ii) virus uncoating, which may also require the interaction of virus and cellular membranes, (iii) release and/or activation of nucleic-acid polymerase with subsequent synthesis of viral DNA or RNA, which is often achieved by virus-specific DNA or RNA polymerases, (iv) reverse transcription and viral DNA integration in the case of retroviruses, (v) proteolytic cleavage of viral precursor proteins, which is an essential step in the assembly of virions, (vi) maturation of viral mRNA (5'-capping, methylation, 3'-adenylation) which may impose greater demands on the cell than the maturation of cellular mRNA, (vii) glycosylation of viral proteins, which is required for the assembly of enveloped viruses, and (viii) assembly and release of the newly synthesized viral particles. Most of the antiviral agents that have been reported to date act at one or more of these targets. These unique steps in the process and the interfering compounds are the subject of this review.
(1) Center of Veterinary Institutes of Athens, Institute of Infectious and Parasitic Diseases, Virology Department, (2) Center of Veterinary Institues of Athens, Institute of Biological Products and (3) WHO Mediterannean Zoonoses Control Center
Hellenic Virology, 1997, 2(1): 45-51.
Rabies has been endemic in different regions of Greece up to 1977. During the decade that followed, the disease was low sporadic and confined to the north-eastern borders of the country. From 1987 to this date, Greece is rabies-free. Among the measures taken to control the disease in animals was a live freeze-dried vaccine, prepared since 1952 using the modified LEP and HEP rabies strains and propagated in chick embryos. A compulsory nation-wide vaccination programme contributed to the immunzation of the major part of owned dogs and to the education of the public. For a more efficient and safe immunization of susceptible domestic animals, an experimental inactivated antirabies vaccine was prepared in cell cultures. Rabies Virus, Pasteur Strain (PV), passage 182 in Baby Hamster Kidney (BHK) cells was used. The virus was propagated in Hamster Adult Kidney cells in Dulbecco's medium with 10% Fetal Calf Serum (FCS). The cells were infected under suspension at 37C for 2h. The rate of infection of the cells was observed by the immunofluorescence method. The supernatant fluid was collected in approximately 72h, titrated in mice, centrifuged and then inactivated with beta-propiolactone 1/4,000 at 37C for 2h. 10% Al(OH)3 was added as adjuvant for adsorption of the virus and 0.1% sodium merthiolate as preservative. The vaccine was distributed in vials of one dose (1ml) and stored at 4C. The final product was tested for inactivation, safety, sterility and immunogenicity. The last test was performed according to the NIH method, in our laboratory as well as in France. A direct ELISA test was also performed for antibody detection in mice and dogs. Following the satisfactory results obtained at the laboratory level, larger scale immunization trials in dogs should be performed aimed at further evaluating the safety and efficacy of the vaccine.
Microbiology Department, General Peripheral Hospital "Asklipios", Voula, Athens
Hellenic Virology, 1997, 2(1): 52-55.
A total of 104 serum samples from patients suffering from clinical infectious mononucleosis were tested by an indirect immunofluorescence assay for avidity of Epstein-Barr virus (EBV) capsid antigen immunoglobulin G, involving a wash step with phosphate-buffer saline-8M urea. Sixty eight samples showed serological markers of recent EBV infection and 30 cases had serological evidence of prior infection. In the avidity assay, eighty two samples from patients had recent infection. The avidity assay showed a sensitivity at least equal to that of classical serological procedures for diagnosing EBV infectious mononucleosis. This assay may help to disriminate between primary and secondary infections.
Virology Department, General Peripheral Hospital "G. Gennimatas", Athens
Hellenic Virology, 1997, 2(1): 56-59.
Serum samples of 340 healthy persons and 50 patients with fever of unknown origin were evaluated for IgG and IgM antibodies of HHV 6. IFA assay (Stellar USA) was used for the determination of HHV 6 antibodies. The results of this study are summarised as follows: in the healthy population, IgG antibodies were detected in 254/340 (74.70%) and specific IgM antibodies in 13/340 (3.82%). In the group of patients, IgG antibodies were detected in 38/50 (76%) and IgM antibodies in 9/50 (18%). None of the patients had specific IgM antibodies to CMV, EBV or HSV-1 and HSV-2. Our results indicate that HHV 6 may be one of the etiologic agents of fever of unknown origin.
Istituto Zooprofilattico Sperimentale della Lombardia e dell' Emilia, Brescia, Italy
Hellenic Virology, 1997, 2(1): 60-65.
In this paper we examine some general considerations on the role played by cell culture techniques in virology together with the view of more advanced technologies.