[Oral immunization of suckling piglets against classic swine fever]. / Oralna imunizatsiia na bozaeshti praseta protiv klasichna chuma pri svinete.

Attempts were made to immunize suckling pigs against classic swine fever. The pigs were treated orally, originating from sows which were immunized on the 30th-40th and the 90th-100th day of pregnancy, as well as from sows which were vaccinated one month prior to impregnation. A Bulgarian lapinized K vaccine and a Soviet LK-VNIIVViM cell culture were used (immunization being carried out 1-2 hours before the newborns were allowed to suck) at the rate of 150 doses for both vaccines. It was demonstrated that the application of a live vaccine, which was patterned as cited above, eliminated the inhibiting action of colostral antibodies and induced stable postvaccinal immunity. However, the effectiveness of the immunity conferred depended on the vaccine used in each specific case. The Soviet vaccine, in which the amount of the virus per vaccinal dose was five times as much, was shown to be more appropriate to the needs for oral immunization of suckling pigs of sows that were immune to classic swine fever than the lapinized K vaccine.

[Development of ELISA for demonstrating antibodies to the swine pestivirus]. / Razrabotvane na ELISA za dokazvane na antitela sreshtu pestivirusa po svinete.

An indirect variant of the enzyme linked immunosorbent assay with the classic form of swine fever has been worked out. The test makes it possible to assess the level of antibodies with a great number of animals over a short period of time with no special equipment. The method has proved promising in taking prophylactic measures.

[Effect of prostaglandin F2 alpha on the immune response in rabbits]. / Vliianie na prostaglandin F2 alfa vurkhu imunniia otgovor pri zaitsi.

Investigations were carried out to make clear the effect of prostaglandin F2alfa on forming the primary immune response, using a model of the La Sota antigen. It was found that up to the 48h hour following the use of prostaglandins the immune response decreased, while at the 72nd hour no such drop was observed. It is suggested to pay due attention also to the application of prostaglandin preparations in taking immunoprophylactic measures in cattle breeding and industrial pig farming.

[Demonstration of the swine fever virus by the infection of cell cultures of lymphocytes and lysed red blood cells]. / Dokazvane na virusa na chumata po svinete chrez zaraziavane na kletuchni kulturi s limfotsiti i lizirani cherveni kruvni kletki.

A method was worked out for the diagnosing of swine fever by means of infecting sensitive cell cultures on lamellae with lyzed red blood cells and lymphocytes, the demonstration being performed through immunofluorescence. The new method made it possible to avoid killing of suspected animals for diagnostic purposes (in order to prepare suspensions of parenchymal organs and isolate the virus) while the characteristic morphologic changes were still not well manifested.

[Isolation of the Fab fragment from immune sera]. / Poluchavane na Fab-fragment ot imunni serumi.

A Fab-fragment was obtained from rabbit anti-swine JgG serum through the breakdown of JgG by means of the proteolytic enzyme pepsin in ion-exchange chromatography on DEAE cellulose. It was found that the Fab-fragment gave no positive precipitation in the immunodiffusion agar gel test, and in electrophoresis on 10 per cent acrylamide gel following preliminary breakdown with 1 per cent SDS and 2 per cent ME and heat treatment at 100 degrees C for 2 minutes it showed only one polypeptid chain with equal mobility as that of the light JgG chain. On the basis of the results obtained speculations are made of the mode and site where pepsin supposedly acts.

[Comparison of the indirect enzyme-bound immunosorbent method with the hemagglutination inhibition test in detecting Newcastle disease antibodies in vaccinated chickens]. / Sravniavane na indirektniia enzim-svurzan imunosorbenten metod s reaktsiiata vuzpirane na khemaglutinatsiiata pri otkrivane na antitela sreshtu psevdochumata vuv vaksinirani pileta.

The sensitivity of ELISA and the hemagglutination-inhibition test was comparatively studied in the demonstration of Newcastle disease antibodies in the sera of 57 vaccinated birds. Differences were established in the antibody titers as demonstrated by the two methods. The sensitivity of ELISA was found to be 100 times higher than that of the HI-test. Discussed is the possible use of ELISA in cases where no antibodies or low-titer hemagglutinating ones are demonstrated via the HI-test.

[Protein fraction changes in swine raised under different conditions]. / Promeni v beltuchnite fraktsii u svine, otglezhdani pri razlichni usloviia.

The total protein and the protein fractions were studied in pigs raised both under industrial conditions and on the personal farms. It was found that the process of immunogenesis in pigs varied largely parallel to the various conditions of raising. The numerous immunoprophylactic treatments under industrial conditions were found to have an adverse effect on the forming of the immune response, even without apparent antigen competition. The investigations aimed at elucidating the expediency of the adopted and very often unsubstantiated, repeatedly effected treatments for the rational use of mixed vaccines.

[Inhibition of NDV reproduction with antibodies against its F protein]. / Inkhibirane na reproduktsiiata na NDV s antitela sreshtu F-proteina.

Obtained were the JgG and Fab fragments from a monovalent serum against the F-protein of the Newcastle disease virus. Both the JgG and the Fab fragment inhibited the virus reproduction in cell cultures of chick embryo fibroblasts and BHK21 if they were added after the adsorption and virus penetration of the cells. The inhibitory action of the antibodies was due to their direct fixation by the newly synthesized F-protein in the cells infected with the virus. The rate of inhibition of the Newcastle disease virus as shown by the JgG and Fab fragments of the serum produced against a pure F-protein was the same with the use of chick embryo fibroblasts as with BHK21.

[Demonstration of Newcastle disease virus by enzyme-linked immunosorbent assay]. / Dokazvane virusa na Niukiasulskata bolest (NDV) chrez enzim-svurzaniia imunosorbenten metod.

Investigations were carried out with regard to the application of the sensitive, rapid, and effective enzyme-linked immunosorbent assay (ELISA) in the demonstration of the Newcastle disease virus (NDV). Used was the peroxydase-marked immunoglobulin fraction of the anti-DV rabbit serum in the microconditions of the double-antibody method. The demonstration of the NDV was in a cultivation liquid of NDV-infected BHK21 cells. As control served intact cells as well as strains Roussev and La Sota of NDV pruified through ultracentrifugation on an isokinetic saccharose gradiend. It is stated that ELISA is much more sensitive than the hemagglutination test and the agar gel immunodiffusion test.

[Trails with levamisole to stimulate immunity against Newcastle disease in poultry]. / Opiti za stimulirane na imuniteta sreshtu psevdochuma po ptitsite s levamizol.

Attempts to stimulate the immunity against Newcastle disease in birds aged 2 months, of the Leghorn breed, were carried out. It was found that levamisol at the rate of 3 mg/kg body weight given once, parenterally, 24 hours prior to or after the immunization of the birds with a live La Sota vaccine or given three times, parenterally or orally, did not stimulate the humoral immune response. No differences were found in the level of the total protein, protein fractions, and the titer of the hemagglutinating antibodies between the test and the control birds. There was, however, prolongation of the time of effective immunity in the levamisol-treated and vaccinated birds as against the birds that were vaccinated against Newcastle disease only. Discussed in the possible mechanism of stimulating the immunity with levamisol.

[Diagnostic value of agglutination reaction with buffered Brucella antigen stained with rose bengal]. / Vurkhu diagnostichnata stoinost na RA s buferiran brutselen antigen, otsveten s bengalsko rozovo.

A specific buffered antigen has been obtained, employing a method developed by the authors, stained with Bengal rose and intended for performing a fast agglutination reaction to confirm brucellosis. The antigen produces a clear and demonstrative agglutination reaction with positive sera. Practically, the test is readily carried out, and can be made a routine both in every serologic laboratory and for investigations under field conditions. The reaction produced with this antigen can determine dependably the epizootic status on a farm or in the herd. The diagnostic value of the antigen is essential, especially with swine. Besides, it shows a wide a diagnostic scope for brucellosis with all species of animals (97--98 per cent).

[Control of immunity against swine plague by the viral neutralization test on rabbits]. / Kontolirane na imuniteta protiv chuma po svinete chrez virusneutralizatsionen test na zaitsi.

An idea may be got on the properties of the vaccine by applying a specific gamma-globulin against swine fever in pigs, mixed in definite amounts with lapinized K-vaccine and this mixture is injected to rabbits. By studying the mixture of sera from pigs, vaccinated against swine fever prior to a fixed period of time, and the K-vaccine, applied to rabbits, an idea may be obtained on the tension of the immunity and re-vaccination requirements may be assessed.

[Effect of aflatoxin on the serum profile and antibody formation in chickens]. / Vliianie na aflatoksina vurkhu serumniia profil i obrazuvaneto na antitela u pileta.

Experiments were carried out to follow up the effect of aflatoxin on the production of hemagglutinating antibodies in birds vaccinated against Newcastle disease and the changes in the serum profile. Birds that had been given a feed mixture with 560 and 640 mcg per kg for 20 days showed a lower titer of hemagglutinating antibodies and a drop of the alpha1, alpha2, beta1, gamma2-globulin fractions as well as a rise of the albumin and gamma1-globulin fractions. The liver and kidneys of the treated birds showed dystrophic changes.

[Differentiation of non-specific positive brucellosis reactions using an antigen stained with rose bengal]. / Diferentsirane na nespetsifichni polozhitelni reaktsii za brutseloza chrez antigen, otsveten s bengalsko rozovo.

A Brucella buffered antigen, stained with Bengal rose by a method of the authors, was obtained. It showed a high distinguishing capacity with regard to the nonspecific agglutinations after Huddleson and Wright at a negative complement-fixation test for brucellosis with sera from cattle, pigs, sheep, and horses. Such differentiation, however, proved to be incomplete and for sera of different animals varied within the range of 34 to 0.0 per cent.