Soligenix (formerly known as DOR BioPharma) has reported the publication of an article in the January 2010 edition of Infection and Immunity, detailing the characteristics of several immunodominant regions of ricin A chain, the antigenic component of RiVax.
RiVax is Soligenix’s vaccine to protect against exposure to ricin toxin and is currently being evaluated in phase 1 human safety and immunogenicity trials, as well as nonhuman primate trials for efficacy.
In the study, the investigators produced and characterised a monoclonal antibody directed against a region (epitope) of the ricin A chain, previously known to be highly immunologically stimulatory (immunodominant) in humans. The monoclonal antibody was shown to bind the ricin A chain with high affinity, and to be capable of neutralising ricin toxin in a cell-based killing assay.
Moreover, when administered to mice, the neutralising antibody was sufficient to protect the animals against both systemic (intraperitoneal) and mucosal (intragastric) ricin challenge. These results advance the concept that antibodies present in the circulation at the time of toxin exposure not only protect animals against death, but may also prevent the toxin’s effects on mucosal tissues.
Nicholas Mantis, lead author of the study, said: “These data are important in terms of ricin vaccine development, since they firmly establish that pre-existing serum antibodies directed against linear determinants on the ricin A chain are sufficient to confer both systemic and mucosal immunity to ricin.”
Robert Brey, chief scientific officer of Soligenix, and a co-author of the study, said: “Vaccination by injection primarily induces antibodies in the circulation, and in the case of RiVax, these fundamental results further indicate that intramuscular vaccination will be expected to protect humans against ingestion of toxin or aerosolized toxin exposure. The publication of these results is exciting as they lead the way to the potential development of new applications utilising a key target of neutralising antibodies in vivo.”