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Infection and Immunity publishes positive pre-clinical results with Soligenix's RiVax.


28 December 2009 - US biopharmaceutical company Soligenix Inc (OTC: SNGX) said today that Infection and Immunity has published in its January 2010 edition an article 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 I human safety and immunogenicity trials, as well as nonhuman primate studies for efficacy.

The article, entitled "A Monoclonal Immunoglobulin G Antibody Directed against an Immunodominant Linear Epitope on the Ricin A Chain Confers Systemic and Mucosal Immunity to Ricin," is the result of collaborative efforts between the Wadsworth Center of the New York State Department of Health (Albany, NY) and Soligenix. The research was funded in large part by several National Institutes of Health (NIH) grants to the company for the development of RiVax.

In this 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 passively to mice, the neutralising antibody was sufficient to protect the animals against both systemic (i.e., intraperitoneal) and mucosal (i.e., 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, the company said. This is an important finding, as ricin is toxic to humans following ingestion and inhalation. The study is also significant because it raises the possibility of using specific linear determinants on the ricin A chain as markers for protective immune responses in humans. Immunological readouts, such as the ability of serum antibodies to react with specific neutralising epitopes on the ricin A chain, along with other markers that are currently in use to investigate human immune responses, will be essential in fully evaluating the efficacy of candidate ricin vaccines such as RiVax, in the absence of the ability to perform vaccine efficacy trials in humans, Soligenix added.

Soligenix's chief scientific officer and co-author of the study, Robert Brey, said that vaccination by injection primarily induces antibodies in the circulation, and in the case of RiVax, these results further indicate that intramuscular vaccination will be expected to protect humans against ingestion of toxin or aerosolised toxin exposure.

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Publication:M2 Pharma
Date:Dec 28, 2009
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