Summary. Clostridium sordeiiii produces two toxins, designated HT (haemorrhagic toxin) and LT (lethal toxin), that are similar to toxins A and B of C . dzBciZe. The physicochemical properties of toxins HT and A were remarkably similar. The specific biological activities of toxin HT were almost the same as those of toxin A, and their NH,-terminal sequences shared close homology. The properties of toxins LT and B were similar, as were their NH2-terminal sequences, but toxin B was much more cytotoxic than toxin LT. Immunodiffusion analysis with specific antibodies showed that although toxins B and LT shared major antigenic determinants, each had unique epitopes. The results suggest that toxins B and LT have diverged more than toxins A and HT. Immunoblotting with antibodies to the toxins of C. dzficile showed that toxins HT and LT had common antigenic determinants.
In trodue tionSeveral studies have implicated Clostridium sordefiii as a cause of diarrhoea and enterotoxaemia in domestic and. more recently, as an agent of toxic shock-like syndrome in man.*? This species was once suspected to be the cause of pseudomembranous colitis (PMC) in man because the cytotoxicity of faecal filtrates from PMC patients was neutralised by C.
sordelfiiHowever, C . sordeiiii could not be isolated from the faeces of patients with PMC. This discrepancy was clarified when C. dificile was isolated from faecal samples of patients with PMC,9-' and it was shown that the toxins produced by this organism are neutralised by C. sordellii 2* l 3 Two toxins, A and B, have been purified from culture supernate of toxigenic strains of C. dzficife. ''-I6 Both are large proteins that are lethal to animals and cytotoxic. Toxin A is a potent enterotoxin that produces a haemorrhagic fluid response in the rabbit ileal loop assay.C . sordeifii produces two toxins that are similar to toxins A and B, which explains why C . sordeffii antitoxin neutralises the toxins of C . drficife. The production of two distinct toxins by C. sordefiii was first described by Arseculeratne er aI.,*' who extracted a haemorrhagic toxin from sporulating cells and an oedema-producing toxin from vegetative cells. The oedema-producing toxin was more lethal than the haemorrhagic toxin and the toxins are now referred to as LT (lethal toxin) and HT (haemorrhagic toxin) respectively. We have already described the purification of toxin HT by ultrafiltration and immuno-affinity chromatography with a monoclonal antibody (MAb) to toxin A, and have shown that toxin HT has biological activities and immunological properties similar to those of toxin A. * Popoff has purified toxin LT and shown that it is immunologically related to toxin B.22 The toxins produced by C. dzflcile and by C. sordeiiii have similar physicochemical as well as immunological and biological properties but they are not identical. Therefore, it was of interest to compare the properties of these toxins in more detail.
Materials and methods
Protein determinationProtein concentration was estimated by the method of Bradford23 w...
The goal of this study was to compare the immune response and the protection capacity induced by the dengue virus 2 (DENV-2) American and Asian genotypes in Macaca fascicularis monkeys. Animals were infected with American or Asian DENV-2 strains and challenged 1 year later with a DENV-2 Asian genotype strain. The viremia and monkey antibody levels were similar for the different strains after primary and secondary infection; however, the functionality of the antibody response was different. A limited viral replication was demonstrated after the secondary infection in all the monkeys. No virus was isolated in tissue culture, while reverse transcription-PCR showed a late positive reaction in four of five challenged monkeys. The immunoglobulin M response pattern and the detection of antibodies to specific proteins by Western blotting supported the protection data. Despite the demonstration of the protective effect after homologous challenge, a strong anamnestic antibody response was observed.Dengue fever and dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS) are caused by any of four closely related but antigenically distinct dengue virus (DENV) serotypes (DENV-1, DENV-2, DENV-3, and DENV-4).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.