Biomedical subjects

V Denchev

Publications and source records attributed to V Denchev.

17 recordsLinked to original sources

PubMed1992

Humoral and cell-mediated immunity in mice after immunization with live oral vaccines of Salmonella typhimurium: auxotrophic mutants with two attenuating markers.

Persistence and clearance of the vaccinal strains, humoral and cell-mediated immune response and protective immunity were assessed in ICR mice, immunized intraperitoneally or intragastrically with double-marker auxotrophic mutants of Salmonella typhimurium strains 1771 and 3334 (his-pur-). Strain 3334 possesses in addition the antiepidemic Hst (high sensitivity to tensides) marker which confers decreased survival in the gut and environment. The results showed that the strains are not overattenuated. They revealed preserved multiplication capacity, established carrier state for 28-30 days and induced humoral and cell-mediated immunity as measured by passive haemolysis and microagglutination or footpad swelling tests, respectively. The immune response was determined by biological features of the strains. Strain 1771 induced synthesis of O- and H-antibodies 7-11 days earlier than strain 3334. Footpad reactions appeared 3-4 days after immunization and a week before the serum antibodies. Cell-mediated immunity showed clear correlation with the protection against challenge with a virulent strain. The present results suggest that the double-marker auxotrophic mutants of S. typhimurium might prove very useful in the development of a live vaccine in further studies on livestock.

Administration, Oral↗

PubMed1991

Technological aspect of the production of live dysentery vaccines for oral administration.

An experimental technology for the production of live freeze-dried vaccines prepared from attenuated Shigella flexneri 2a and Shigella sonnei I strains was developed. It is based on the cultivation of bacterial strains in a fermentor under conditions which ensure high yields. The strains grow in S-form, their antigenic structure is preserved and they remain non-virulent. The attenuating markers are stable. The freeze-dried vaccines retain good immunogenicity when applied intra-intestinally to rats.

Administration, Oral↗

PubMed1990

Potential Shigella flexneri 2a and Shigella sonnei I live vaccinal strains. Characterization of immunogenicity in animal models.

Rats and rabbits were immunized intraintestinally with different doses of virulent and nonvirulent live Shigella flexneri 2a and Shigella sonnei I strains. The nonvirulent strains had one or two attenuating markers. The period of excretion with the faeces of the bacteria and of their polysaccharide antigens, the proliferation of antigen-binding and antibody-producing cells in the spleens and gut-associated lymphoid tissues and the levels of antibodies in sera and faeces were studied. Attenuated strains S. flexneri 2a 77 and S. sonnei I 3359 induced the most potent and long lasting local immune response.

Animals↗

PubMed1988

[Stability of Shigella flexneri attenuated strain 2A 77 ADE- RIF-r after cultivation in a fermenter and lyophilization].

The method for the cultivation of S. flexneri attenuated strain 2a 77 ade- rifr in a fermenter with the use of casein fermentative broth containing 200-250 mg% of amino nitrogen has been developed. No changes in the properties of the initial strain have been found after its cultivation in a fermenter or after the lyophilization of the cultures grown in a fermenter. After cultivation in casein fermentative broth with 100 mg% of amino nitrogen the presence of S-R dissociation has been established, the S colonies having the properties of the initial strain. The reversion of the R colonies to prototrophism in adenine and differences in the level of their resistance to rifampicin are observed. The study of the plasmid profile of the initial strain and its ade+ revertants has revealed the disappearance of plasmids with a molecular weight of 140 MD in these revertants. All clones under study (ade+ and ade-) show negative results in the keratoconjunctival test. The conditions of cultivation and the causes of reversion are discussed.

Fermentation↗

PubMed1988

Local and systemic immune response in rabbits after intraintestinal immunization with a double-marker attenuated strain of Salmonella typhimurium.

Local and systemic immune response was studied in 3 groups of rabbits immunized and reimmunized 190 days later with S. typhimurium double-marker attenuated strain 1,771 and doses ranged from 20.10(9) to 0.2.10(9) cells. Another group of rabbits was immunized with extract (hydroxylammine) vaccine. It was found that the attenuated strain persisted for considerable time in the gut, and induced pronounced and continuous immune response as measured by the passive hemagglutination test. The serum antibody response had the character of a secondary one with switching on the synthesis of IgM to IgG already after basic immunisation. By the Coombs' technique it was shown that specific immunoglobulins demonstrated in feces were secretory antibodies of the class IgA (SIgA). The immune response developed after reimmunization was still more vigorous and prolonged pointing to an immune memory existance. It was possible to obtain well manifested immunity with the lowest dose. The extract vaccine revealed only weak and transitory serum and intestinal antibody levels without SIgA appearance. The results obtained in this setup make S. typhimurium 1771 a perspective candidate for a live vaccine.

Animals↗

PubMed1987

Technological investigations with attenuated strains of Shigella for production of live vaccines. 1. Cultivation in a fermenter of an attenuated strain S. flexneri 2a with two markers.

A method was developed for cultivation of the strain Shigella flexneri 2a 77 with two attenuated markers. It ensures the preservation of the initial properties of the strain. The regimen for control of dissolved oxygen level was optimized. It was established that yeast extract is a necessary component of the nutritive medium used. The role of the phase and quantity of the inoculum for growth of the bacterial population has been clarified. Fresh fermenter culture, applied in rats, shows a high immunogenic activity. After lyophilization, the cultures retain 50-70% of the immunogenic activity of the non-lyophilized cultures. The method makes preconditions for the production of a live attenuated dysentery vaccine for oral administration.

Animals↗

PubMed1985

[Liver enzyme function and humoral immunity in workers exposed to vinyl chloride].

The work aims at studying the enzyme function of the liver, as well as the humoral immunity of workers engaged in the production of vinyl chloride and polyvinylchloride with proved hepatotropic and Raynaud syndromes. About 191 workers /experimental group/ from the synthesis and polymerization of vinyl chloride and 2 control groups--34 persons from Varna and 54 from G. Traĭkov were examined. The following biochemical and immunological studies were performed: GOT, GPT, GGTP, alkaline phosphatase, IGG, circulating immune complexes, titer of the complement, cryoglobulins in the serum and identification of the sediments by immunoelectrophoresis. It was established that the immune system was included in the early phases of toxic effect. Disturbances in the enzyme function and humoral immunity were registered both in workers with hepatotropic and Raynaud syndromes.

Antibody Formation↗

PubMed1975