Stability of (2'-5')oligoriboadenylates in various sera.

Avian and mammalian sera were found to contain an enzyme activity degrading 2-5A oligonucleotides. The most extensive degradation of the A2' p5' A was observed in chicken serum. Degradation of this compound is not affected by the presence of cAMP, dsRNA, Mg2+, but is significantly inhibited by EDTA. The enzyme activity described is not inactivated by heating to 56 degrees C for 30 min. The 5-mU3' p5' A has also been degraded in chicken serum.

Ovine scrapie: priorities and importance.

Ovine and caprine scrapie occupies a unique place among animal transmissive spongiform encephalopathies (TSE). It is an object of intensive biomedicinal, ecological and economical studies. Its causative agents are demonstrably associated with the development of TSE in farmed minks, goats and moufflons. Ovine strains of scrapie occurring in North America (particularly in the USA) differ from strains which occur in Europe and were present at the onset of development of TSE in three species of deer living in free nature and in captivity in the USA. The studies dealing with the development of bovine spongiform encephalopathy (BSE) of the English type have indicated justifiably that its origin is associated with one (or more) heretofore unidentified ovine strain. The development of a variant form, the Creutzfeldt-Jacob disease in humans, and transmission of the BSE agent to several families of bovidae, felidae and primates, puts stress on its zoonotic potential. All this leads to the conclusion that domesticated sheep are the decisive reservoir species of animal TSE. They have been infected to an unknown extent with the causative agent of BSE probably through contaminated meat-bone meal. The occurrence of natural ovine prion isolates with properties similar to those of the BSE agent requires that scrapie should be included in the surveillance of human and animal TSE. At present, scrapie is a noticeable disease also in other than European Communities Member States. It is on the list B of the International Epizootics Office. Many countries have initiated control of ovine scrapie. It should therefore become a topical question also in Central and Eastern European countries. Elimination or even eradication of ovine scrapie (or its causative agents) from populations of small and large domestic ruminants is the prerequisite for prevention of penetration of ovine pathogenic prions into the human feed chain. Moreover, it should be ensured that these species will be able to produce foods of a new type (immunotrition and similar) or proteins with therapeutic effects in the near future. Our study established that the PrP genotype of Valachian rams, the Slovak autochthonous breed, contains also VRQ and ARQ alleles encoding the susceptibility to scrapie. Their selection is part of the improvement of Slovak Valachian sheep towards resistance to scrapie.

[Testing the susceptibility of cultured cells to infection with bovine leukemia virus]. / Testovanie vnímavosti bunkových kultúr k infekcii vírusom bovinnej leukózy.

Different cell cultures were studied for their susceptibility to bovine leucosis virus infection. Syncytial assay was used for this study. The FLS/BLV+ cell line served as virus source. Cell lines BHK-21 and ZP-1/58 were found to be susceptible to syncytium formation. Large cells with one to three large nuclei, and loose nuclei reaching the size of syncytium were observed to occur in the BHK-21 and ZP-1/58 cell lines, apart from the syncytial formations. The virus specificity of the syncytia arising in these two cell lines was confirmed by the immunofluorescence assay. In the case of the immunoperoxidase assay, a positive result was obtained only in the BHK-21 cell line. The occurrence of syncytia and large nuclei was observed even in the cases when the BHK-21 cells were infected with the lymphocytes of leucotic cows.

[Immunological aspects of Marek's disease in chickens with maternal antibodies]. / Immunologické aspekty Markovej choroby u kurciat s materskými protilátkami.

The dynamics of the production of immunoprecipitation antibodies to Marek's disease virus was studied in the serum of chickens with maternal antibodies in relation to the occurrence of the immunoprecipitation antigens of Marek's disease virus in feather follicles. One-day-old chickens were infected by the contact method with Marek's disease virus. The first occurrence of immunoprecipitation antigen was detected on the 14th day after infection and this occurrence persisted throughout the experiment, i. e. until the 112th day after infection. The antibodies were first detected the 28th day after infection and their titre kept rising until the 98th day after infection. Immunoprecipitation antibodies and antigens of Marek's disease virus were detected in some tumorously changed kidneys. Immunoelectrophoretic examination revealed in the same kidneys immunoglobulins of the class IgY, IgA and beta-globulin. The slowest-migrating fraction of IgY, together with IgA, beta-globulin and C-reactive protein were detected in the skin extracts from infected poultry. Indirect haemagglutination enabled the detection of the presence of haemagglutination antibodies in rabbit immunoglobulin to the skin antigen of Marek's disease virus, and in avian immunoglobulin to the same virus. Haemagglutination antigen was revealed in the extract from tumorously changed kidneys.

[Testing the immunogenicity of the dermal antigen in Marek's disease virus]. / Overovanie imunogenicity kozného antigénu vírusu Markovej choroby.

An experiment was performed to study the immunogenicity of the dermal antigen of Marek's disease virus, extracted from the skin of 30-day-old chickens, infected with Marek's disease virus on the first day of life. Three kinds of samples were tested: (1) dermal antigen centrifuged at 10 000 g per 0.5 h, (2) dermal antigen centrifugated at 10 000 g per 0.5 h and 100 000 g per 1 h, (3) dermal antigen treated like sample (2) and partly purified by DEAE-cellulose chromatography. Samples (1) and (2) were inoculated to two-day-old chickens and the vaccination was repeated, using complete Freund's adjuvant, 21 days later. Sample (3) was inoculated to two-day-old chickens with DEAE-dextran. All the three groups were challenged together with the controls (non-vaccinated chickens) on the seventh day after the first vaccination. A reduction of mortality was observed in the chickens vaccinated with and re-vaccinated with sample (1) (23.07%) and in the chickens vaccinated with sample (3) (30.76%). The chickens of the latter group were the last to start dying from Marek's disease--only after the 10th week of life. In the chickens which had been vaccinated and revaccinated with sample (2) the mortality was not reduced. The study is continued, with particular emphasis on the relationship of DEAE-dextran to protection against Marek's disease.

[The effect of sodium nitrite on rats infected with avian sarcoma virus]. / Vplyv Dusitanu sodného na krysy infikované vtácím sarkómovým vírusom.

A potential effect of sodium nitrite was studied as exerted on carcinogenesis elicited by the avian sarcoma virus in the body of rats. In the case of the infection of the rats with indefective avian sarcoma virus B77 (Bratislava strain; ID50 10-25/0.1 ml) and i. p. inoculation of sodium nitrite, great mortality occurred already on the 20th day p. i. On the 125th day p. i. the cumulative mortality in this group was 76.92%; on the other hand, in the control groups (rats inoculated with sodium nitrite or avian sarcoma virus) no deaths occurred before this period. The rats infected with a double dose of the virus were not observed to show pronounced changes in mortality. It was only on the 125th day that cumulative mortality in the group of rats infected with the avian sarcoma virus and rats inoculated s. c. with sodium nitrite was 87.5% and in the group of animals which had only been infected with the virus the mortality was 64.26%. The patho-morphological changes were in keeping with the hitherto described changes in rats infected with the avian sarcoma virus. In the trial no effect of sodium nitrite on the patho-morphological changes induced by the avian sarcoma virus was observed.

[Neuroallergic activity of anti-rabies vaccines]. / Neuroalergická aktivita antirabických vakcín.

The safety and neuroallergic activity of current commercial and experimental rabies vaccine were studied by detecting the patho-histological changes in the central nervous system of laboratory animals (guinea-pigs) according to the method recommended by the World Health Organization (Gispen, 1975). Six rabies vaccines were tested in the experiments. The vaccines are as follows: lyophilized rabies vaccine - human; lyophilized rabies vaccine - veterinary; rabies vaccine U. S. P. duck embryo - human; avianized rabies vaccine - veterinary; inactivated rabies vaccine from strain Vnukov-32 - human; live cell rabies vaccine from strain Vnukovo-32 - veterinary. Patho-histological changes indicating the neuroallergic activity of the vaccines were observed in laboratory animals (varying range and intensity of these activities, to which the following vaccines were applied: lyophilized vaccine - veterinary and lyophilized rabies vaccine - human. The cell rabies vaccines from strain Vnukovo-32 were found to be safe; they can be recommended for their merits (including nonreactogenicity) to be used in veterinary practice in rabies immunoprophylaxis.

[Transmission of Marek's disease to wild feathered game]. / Prenos Markovej choroby na vol'ne zijúcu pernatú zver.

The following wild feathered game were tested from 6 to 12 months of age: common pheasant (Phasianus colchicus), common gray partridge (Perdix perdix), European quail (Coturnix coturnix), and Greek partridge (Alectoris graeca). Only pheasant was found to be susceptible to infection with a virulent virus of Marek's disease. In this bird the first clinical symptoms of the disease (nervous changes) were observed in 28 days from infection. Immunoprecipitation antibodies to the Marek's disease virus occurred in the serum on the 75th day from infection, and patho-morphological changes, typical of acute Marek's disease, were observed on the 75th to 85th day from infection. The remaining species of wild feathered game appeared not to be susceptible to infection with the Marek's disease virus. In these birds, like in pheasants, immunoprecipitation antigens of the Marek's disease virus were not found to be present in the epithelial cells of feather follicles. In the infected Greek partridge, common gray partridge and quail, serum was not found to contain any antibodies. Laying quail had no antibodies in the yolk of the eggs they laid. The results indicate a different oncogenesis of Marek's disease in the domestic fowl and pheasant. It is concluded that wild feathered game play no important role in the epizootology of Marek's disease.

[Pathogenesis of experimental rabies infection in foxes and cats infected with viruses isolated from hamsters (Cricetus cricetus)]. / Patogenéza experimentálnej rabickej infekcie lísok obycajných a maciek domácich infikovaných vírusom izolovaným z chrckov rol'ných (Cricetus cricetus).

All the infected foxes (9) contracted the disease and died from rabies the 20th-21st day from infection with the virus isolated from hamster. Out of the total number of 9 cats experimentally infected by intramuscular infection, seven showed symptoms of clinical disease on the 18th-34th day from infection. The infected dogs, wolves and rabbits did not show clinical disease. In the post mortem examination of eight foxes the rabies virus or rabies antigen was detected in all parts of the CNS and in n. ischiadicus. Of the extraneural organs, the virus was present, in all animals, in the pharyngeal salivary glands, and in one fox also in the tongue. The bioassay on the eye was positive in all cases. The rabies antigen was detected in 4 foxes in the thigh muscle, in liver and spleen, and in all 8 foxes in lungs and cornea, in 5 cases in kidney, and in 3 cases in heart and tongue. Seven cats were examined post mortem by the inoculation test on mice and the PMIF-staining test; it was found that the rabies virus, or rabies antigen, was distributed in the same manner as in foxes.

[Distribution of rabies antigen in the central nervous system of rats and mice experimentally infected with rabies strains isolated from hamsters (Cricetus cricetus)]. / Distribúcia rabického antigénu v CNS potkanov a mysí experimentálne infikovaných kmenmi vírusu besnoty izolovanými z chrckov rol'ných (Cricetus cricetus).

The comparative experiments were carried out to study the distribution of the rabies antigen in the central nervous system (CNS) of sewer-rats and mice experimentally infected with three "hamster" strains (for comparison also with "fox" strain 1151); it was found out that with microscopical observation of preparations stained by the method of direct immunofluorescence the "hamster" strains produced a blended picture of fluorescing particles characteristic of strains with a reduced virulence and virulent strains. As for mice infected with strains 3 O and 7 E the rabies antigen was detected in all parts of CNS as early as 24 hours after infection. In this period the rabies antigen strain 9 E was not detected in lumbar spinal cord and that with strain 1151 was detected only in the Ammonian horns. After 48 hours the rabies antigen in mice was detected in all parts of CNS with all four strains used. In sewer-rats, with regard to their lower susceptibility to the rabies virus, the first detection of rabies antigen in CNS was recorded on the 6th day after infection with strains 3 O, 7 E and 1151, whereas with strain 9 E as late as the 9th day in lumbar spinal cord and not in all animals.

[Testing of poultry for susceptibility to sarcoma viruses in the C subgroup]. / Testovanie hydiny na vnímavost k sarkómovému vírusu z podskupiny C.

Experiments were performed to test the conventional chickens of the Ross I and Tetra-B broiler hybrid and the Shaver Starcross 288 and Slovgal laying hybrid for their susceptibility to the poultry sarcoma virus of subgroup C (B77). The chickens were inoculated six days from hatching and the first sarcomata began to appear at the inoculation spot on the fourth day. The first deaths were observed on the eighth day from inoculation, and the necropsy revealed frequent metastases. Regressive fluid was also found to develop in some cases. On the basis of the haematological examination of all hybrids, significant lymphocytopenia and heterophilia were determined; in addition to this, a significant drop in the basophile count was ascertained in the Tetra-B hybrid and a significant rise in the monocyte count was found in the Slovgal hybrids. Also, a frequent occurrence of a high number of large lymphocytes, a random occurrence of large thrombocytes, and individual myelocytes and metamyelocytes were also observed. The results suggest that the tested poultry represent progressive (highly susceptible) types of poultry, in relation to sarcoma virus of subgroup C.

[The effect of adjuvant substances on the antigenic activity of cellular antirabies vaccine in experiments on cattle]. / Vplyv adjuvantných látok na antigénnu aktivitu bunkovej antirabickej vakcíny v pokusoch na hovädzom dobytku.

Trials were conducted with young cattle to study the effect of adjuvants, applied subcutaneously and intramuscularly, upon the antigenic activity of live and inactivated cell rabies vaccine prepared from the Vnukovo -32 strain at the level of the 107th series cell passage. Cerebral vaccine of Fermi type was also used in the trials for comparison. The antibodies were parallelly titrated by four methods, three of which were conducted in vitro. The levels of antirabies antibodies indicate a possibility of fortifying the antigenic activities of inactivated vaccine by means of the Bioveta Nitra oil adjuvant and the activities of the live vaccine by means of adjuvant prepared after Buchnev . The antigenic activity of the Czechoslovak-produced cerebral rabies vaccine for veterinary use is extraordinarily low.

Immunogenic and antigenic activity of an experimental oral rabies vaccine prepared from the strain Vnukovo-32/107.

The immunogenic and antigenic activity of an experimental live oral rabies vaccine prepared from the strain Vnukovo-32/107 was evaluated on the basis of results obtained in 3 sets of experiments. These were carried out as model experiments on white mice, then on target animals--red foxes (Vulpes vulpes) and a related species--farm-bred polar foxes (Alopex lagopus). For quantitative determination of the immunogenic activity of the orally or subcutaneously administered rabies vaccines in model experiments on mice a method was used that had been developed in our laboratory. Antibodies were detected and quantified by an ELISA kit that had also been developed in our lab. Tenacity of the experimental vaccine (infectious tissue culture medium after yolk addition) was verified at different temperatures; the effects of storage temperature upon virus titre and immunogenic activity were investigated. An important part of the experiments--evaluation of the antigenic and immunogenic activity of the live vaccine at oral vaccination (vaccination baits, conditions simulating field vaccination) was carried out in foxes. The immunogenic activity (challenge experiments with a street virus on day 180 and 360 after vaccination) was evaluated in common foxes (Vulpes vulpes). The results document a high immunogenic and antigenic activity of the experimental live oral rabies vaccine. The strain Vnukovo-32/107 is suitable for the industrial manufacturing of vaccination baits. In the target species--common foxes challenged on day 180 after primovaccination an 83% protection was observed. Challenge on day 180 after revaccination (or day 360 after primovaccination), the orally immunized foxes proved to be 100% protected. For parallel evaluation of the immunogenic activity of an oral vaccine and for antibody titration it is recommended to employ the quantitative mice test and an ELISA technique, respectively.

Quantification of residual virulence of the Vnukovo-32/107 rabies virus vaccination strain.

The present work summarizes the results of 11 groups of experiments carried out with the aim to complexly quantify the residual virulence of a cold mutant of the Vnukovo-32/107 rabies virus vaccination strain intended for the preparation of an oral rabies vaccine (Kamark) for the immunization of free-living carnivores. According to WHO prescriptions, residual virulence was quantified in experiments on carnivores, mainly red foxes (Vulpes vulpes)--the presumed target species, and farm-bred polar foxes (Alopex lagopus)--a related species. Further experiments were carried out in cats, dogs, non-target autochthonous micromammals, predatory birds (Microtus arvalis, Apodemus flavicollis, Falco tinnunculus) and in a large number of laboratory animals--white mice. At oral administration (including extremely high doses) the strain Vnukovo-32/107 proved to be apathogenic to the target carnivores--Vulpes vulpe and Alopex lagopus as well as cats, dogs and the autochthonous micromammals. For Falco tinnunculus the strain proved to be apathogenic even at intramuscular and intracerebral administration. The residual virulence of the Vnukovo-32/107 vaccination strain, also quantified by comprehensive model experiments on white mice of different weight categories that had been infected orally, subcutaneously, intramuscularly, intracerebrally, by contact, with ingestion of rabic material or by modelled immune suppression, proved to be extremely low-levelled. The strain under investigation revealed a high level of attenuation and a low level of residual virulence and proved to be suitable for the preparation of non-reactogenic oral vaccine intended for foxes, an extremely susceptible target species.

[Spongiform encephalopathies (prionoses) in animals]. / Spongioformné encefalopatie (prionózy) zivocíchov.

Spongiform encephalopathies constitute a growing group of diseases of the central nervous system which, contrary to other neurodegenerative processes, can be transferred experimentally from one animal species to another. They can develop spontaneously on a hereditary familial basis, the conform prion protein developing in the posttranslation process having the character of in infectious agent initiating the degeneration of nerve cells. The mechanism of such as infection differs from other infectious diseases. The bovine spongiform encephalopathy agent, discovered in Great Britain in 1985 has an extensive zoonosis potential and has overcome the interspecies barriers. The key problem in spongiform encephalopathies of animals is the definitive explanation of their etiology, pathogenesis, intravital diagnosis as well as interspecies relationships. (Tab. 5, Ref. 11.)

[The niches and pathways of animal pathogens]. / Niky a cesty patogénov k zivocíchom.

Infectious diseases are not a relict of the past but a topical phenomenon determined by complex evolution of the currently existing and constantly changing microbial agents and their hosts. With regard to abundance of species within the microbial kingdom and rate of its changes and development, it is difficult to predict the role of the microbial factor in mortality of humans and animals. The study and generalization of sequential similarities of microbial virulence factors after the completion of genome sequencing of principal pathogens can play a positive role in this direction. At present, molecular-genetic methods allow us to study the phylogenetic relationships of microbes and categorize them according to new criteria. The efficient control of diseases caused by microbes requires knowledge on their physiological and ecological niche from which they penetrate, in various ways, into the host organisms and, under suitable conditions, induce mass diseases. This process has several stages and, in the recent period, it is increasingly affected by human activities. The knowledge on all participants in this process, i.e. the microbe and its niche, factors of virulence and pathways of their dissemination, requires a scientifically based surveillance. Abundance and variability is characteristic for both microbial kingdom and microbial niche. Some identification of pathogenic properties of microorganisms and factors affecting their movement from their niche to the recipients results in activation of old classical diseases (e.g. plague, cholera, tuberculosis etc.) or emerging of new, so far unknown infections diseases ("emerging inf. disease"--EID), caused for example by lentiviruses, oncoviruses, filiviruses, bartonella, borrelia etc. This has provided the basis for establishment of new medical trends and approaches, such as "Emergency medicine" or "Travel medicine", expressing their purpose by their names. The control of existing or proposed infectious diseases in the 21st century (in which majority of factors such as urbanization, environmental factors, evolution of the microbial kingdom, will contribute to the persistence or "emergence" of new diseases) will be affected by the input of new knowledge in the field of molecular biology, such as introduction of biosensors, genetic tests, microchips, new generation of DNA vaccines, enteric vaccines and antibodies produced by transgenic animal bioreactors or plants, "customized" vaccines assessed for individual genetic profiles, etc. (Tab. 5, Ref. 21.)

Hydrolysis of adenylyl(2'-5')adenosine in chick embryo sera.

Similar to adult chick sera in chick embryo sera the enzyme activity hydrolyzing the core of the dimer of A-5A - adenylyl(2' -5')adenosine is present. The enzyme activity possesses the same properties in both sera. Heating of the serum to 60 degrees C for 30 minutes does not affect the enzyme activity. A marked decrease in activity occurs after heating of the serum to above 65 degrees C. Hydrolysis of A2' p5' A in the serum is more efficient under alkaline conditions (pH 9-10) than at physiological pH 7.2-7.4.