SEARCH · PubMed Health
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Explore the source record for details and available documents.
A regulatory gene (dtxR) responsible for iron-dependent repression of the toxin (tox) and siderophore genes in Corynebacterium diphtheriae was cloned and characterized. A DNA fragment carrying dtxR repressed expression of a tox-lacZ gene fusion in Escherichia coli DH5 alpha in a high-iron environment but not under low-iron conditions. A protein with mobility corresponding to approximately 28 to 29 kDa was identified as the product of the dtxR gene by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A shuttle vector designated pCM2.6 was constructed which carries the origin of replication from C. diphtheriae plasmid pNG2 and confers resistance to chloramphenicol in E. coli and C. diphtheriae. DNA fragments carrying dtxR were cloned into pCM2.6, and the hybrid shuttle plasmids were transformed by electroporation into wild-type C. diphtheriae C7(beta) and the regulatory mutant C7(beta)hm723, which produces toxin and siderophore constitutively under high-iron conditions. Expression of the cloned dtxR determinant did not affect the phenotype of C. diphtheriae C7(beta). In C. diphtheriae C7(beta)hm723, expression of cloned dtxR restored full repression of siderophore production and partial repression of diphtheria toxin production during growth in a high-iron environment.
The public immunization program against diphtheria, established in 1941, has almost eradicated the disease in Denmark, and 1956 became the first year without any notified cases. Since then, toxigenic strains have only been isolated five times--three cases of clinical diphtheria due to Corynebacterium diphtheriae biovar. mitis and two cases of tonsillitis/pharyngitis due to Corynebacterium ulcerans. The source of the infection was not identified in any of the cases. The first case of diphtheria in 1968 was imported from abroad. The following two cases in 1983 and 1985 were due to strains of the same phage type and peptide profile as the strains isolated during the epidemic in Sweden in 1984-1986. This indicates that the Danish cases and the Swedish epidemic derived from the same source. The diphtheria immunity of the Danish population is decreasing, and the level of protection is approaching the Swedish level. The impact is that a situation like that in Sweden may be anticipated with diphtheria epidemic in the lowest socio-economical groups--the skid row dwellers, alcoholics and drug abusers--if the immunization program against diphtheria is not intensified.
Immunity following diphtheria vaccination in childhood is temporary, and recent outbreaks of diphtheria in adult populations evoked interest in the effect of and side-reactions to revaccination of adults. 237 military recruits were randomly allocated to revaccination with 6 Lf tetanus toxoid or 6 Lf tetanus toxoid combined with 2 Lf or 5 Lf diphtheria toxoid. Side-reactions were recorded one week later, and antitoxin response was assessed after 4 weeks. Protective serum diphtheria antitoxin levels were attained by all subjects receiving diphtheria toxoid containing vaccines. Antibody response was related to dose, indicating a safer long-term protection by revaccination with 5 Lf diphtheria toxoid. All vaccinees, except one without documentation for primary vaccination, attained high tetanus antitoxin levels. Interference phenomena between toxoids were insignificant. Mild local reactions were reported by 22% of the vaccinees. More pronounced local reactions were experienced by 5% and systemic reactions by 3%, independent of vaccine. No serious reactions were observed. Reactions were significantly related to tetanus antitoxin response only. It was concluded that combined revaccination of adults, primary vaccinated around 20 years previously, may be performed without immune assessments.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
In view of the current efforts to find a reliable in vitro method which can suitably act as an alternative for determining the potency of the diphtheria component in a combined vaccine, we have analysed experimental batches by the method proposed by WHO [1] i.e. challenge method in guinea pigs. The same batches were also analysed by the alternative antibody induction method as suggested in the Indian Pharmacopoeia (I.P.) [2] which is similar to the old method suggested in the British Pharmacopoeia (B.P.) 1973. As per I.P. the initial part of raising the antibodies remains unaltered but the actual titration of diphtheria antitoxin from the immunised guinea pigs was performed by using the following in vitro methods: a) indirect haemagglutination test using human "O" red blood cells to coat diphtheria toxoid using chromic chloride as the coupling agent [3]; b) toxin neutralisation test using Vero cells [4]; c) a double diffusion technique in agar gel for titration of diphtheria antitoxin [5]. Our findings show clearly that the results of two in vivo methods i.e. Challenge Test, Alternative I.P. Method and the above-mentioned three in vitro methods are comparable and would certainly reduce the number of animals required by making a combination of in vivo and in vitro techniques to give us an assessment of the potency of the vaccine to be tested.
We compared immunogenicity and reactogenicity of a single dose of DTaP vaccine (containing tetanus and diphtheria toxoids and four acellular pertussis antigens) with conventional Td- or d-vaccines in 180 German adults. Antibody values against diphtheria and tetanus toxin and against the pertussis antigens fimbriae (FIM), filamentous hemagglutinin (FHA) and pertussis toxin (PT) were measured in pre- and post-immunization sera. Reactogenicity was determined by a patient diary card. Pre-immunization antibody values against diphtheria toxin were low in all three vaccine groups. After immunization, > or = 80% of the vaccinees in all three groups were fully protected (> or = 0.1 IU/ml), but geometric mean values were significantly higher in DTaP recipients compared to Td or d recipients (1.65 vs. 0.44 and 0.48, respectively; both P < 0.05). Pre-immunization antibody values against tetanus toxin were high in all three groups, and after immunization 100% of the vaccinees were protected (> or = 0.1 IU/ml). Furthermore, substantial antibody responses against pertussis antigens were elicited in DTaP recipients with geometric mean rises of 22.5, 4.1 and 7.5 for antibodies against FHA, fimbriae and PT, respectively. All three vaccines were well tolerated. Frequency and severity of local reactions were similar between DTaP and Td recipients and even less common in d recipients. Since DTaP did provide a significant boost of anti-pertussis antibodies and a significantly higher anti-diphtheria response than conventional Td vaccine without an increase of side effects, it might be an appropriate candidate for use in adults.
One lot of a nationally distributed diphtheria and tetanus toxoids and acellular pertussis (DTaP) vaccine was recalled in January 1999 because of a subpotent diphtheria toxoid component. To evaluate vaccine immunogenicity, children who had received the recalled lot for at least 2 of the 3 doses of their primary series were identified. Diphtheria antitoxin (DAT) levels were then prospectively assessed before and after dose 4 of (fully potent) DTaP vaccine. Of the 105 children evaluated, 84% had prevaccination DAT levels <0.10 IU/mL, which is the level generally accepted as protective. DAT levels rose a mean of 92-fold after dose 4; 100% of subjects had DAT levels >or=0.10 IU/mL, and 69% had DAT levels >or=1.0 IU/mL. These results indicate that diphtheria potency testing can identify vaccine that is less immunogenic when administered during the primary series. The booster response to dose 4, although reduced, was sufficient to confer adequate protection in the interval before receipt of the fifth dose of DTaP.
Diphtheria toxin (tox) and its regulatory element (dtxR) from 72 Corynebacterium diphtheriae strains isolated in Russia and Ukraine before and during the current diphtheria epidemic were studied by PCR-single-strand conformation polymorphism analysis (PCR-SSCP). Twelve sets of primers were constructed (eight for tox and four for dtxR), and three regions within tox and all four regions of dtxR showed significant variations in the number and/or sizes of the amplicons. Two to four different SSCP patterns were identified in each of the variable regions; subsequently, tox and dtxR could be classified into 6 and 12 different types, respectively. The great majority of epidemic strains from both Russia and Ukraine had tox types 3 and 4, and only in a single preepidemic strain isolated in Russia were all eight tox regions identical to those of C. diphtheriae Park-Williams No. 8 (tox type 1). Epidemic strains from Ukraine can easily be identified by dtxR type 5, while the majority of the Russian epidemic strains have dtxR of types 2 and 8. No differences in the tox regions between mitis and gravis biotype strains were observed. However, dtxR types 2, 5, and 8 were identified only in the gravis biotype, and dtxR type 1 was characteristic for the mitis biotype strains. PCR-SSCP is a simple and rapid method for the identification of variable tox and dtxR regions that allows for the clear association of tox and dtxR types with strains of distinct temporal and/or geographic origins.
A mouse model to estimate the potency of the diphtheria toxoid component in diphtheria-tetanus vaccines and diphtheria-tetanus-pertussis vaccines has been developed as an alternative to the conventional method of testing in guinea-pigs. Optimal conditions with regard to dose, route and period of immunization have been standardized. The maximum levels of antitoxin were detected five weeks after vaccination and the s.c. route was found to be optimal. Potency data have been compared with other studies in mouse models and with those obtained by the conventional method in guinea-pigs.
The 3rd part of the paper deals with the results of a combined revaccination against diphtheria and tetanus in a group of 25 children after allogeneic bone marrow transplantation (BMT) with and without graft versus host disease (GvHD) and after autologous transplantation. It can be shown that in the allogeneic transplanted groups with and without GvHD it is possible to build up a tetanus and diphtheria antitoxin titre in a safe protective cause by a 2nd basic immunisation consisting of 3 single vaccinations starting about 9 to 12 months later. For autologous transplanted children only 1 to 2 vaccinations at a later term than for the allogeneic transplanted children may possibly be sufficient.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
The biochemical characteristics of specific receptor molecules for diphtheria toxin on the surface of two toxin-sensitive cell lines (Vero and BS-C-1) were examined. Diphtheria toxin was found to bind to a number of different proteins in Nonidet P-40 solubilized extracts of 125I-labeled cells. In contrast, permitting diphtheria toxin to bind first to labeled intact cells, which were subsequently solubilized and subjected to immunoprecipitation with anti-diphtheria toxin, resulted in a far more restricted profile of diphtheria toxin-binding proteins that possessed Mrs in the range of 10,000-20,000. Direct chemical cross-linking of radioiodinated diphtheria toxin to cell surface proteins resulted in the appearance of several predominant bands possessing Mrs of approximately 80,000. The Mr approximately 80,000 complexes were shown to be composed of radiolabeled diphtheria toxin (Mr 60,000) and unlabeled Mr approximately 20,000 cellular proteins. These complexes were judged to be a result of specific binding in that their appearance could be preferentially inhibited by the addition of a 100-fold excess of unlabeled diphtheria toxin. The formation of the Mr approximately 80,000 complexes was sensitive to prior trypsin treatment of the cells and to known inhibitors of diphtheria toxin binding. Furthermore, prior incubation of the cells with diphtheria toxin at 37 degrees C ("down regulation") markedly and specifically reduced the subsequent formation of the Mr approximately 80,000 cross-linked complexes, and these down-regulated cells were less sensitive to diphtheria toxin in cytotoxicity assays. Further incubation of down-regulated cells at 37 degrees C restored their ability to form Mr approximately 80,000 complexes; this regeneration requires protein synthesis and restores the cells' sensitivity to diphtheria toxin-mediated cytotoxicity. These results strongly suggest that a Mr 10,000-20,000 cell surface protein is, or constitutes a portion of, the functional diphtheria toxin receptor.