Ricin toxoid

Griffiths, G.D., Bailey, S.C., Hambrook, J.L., Keyte, M., Jayasekera, P., Miles, J. and Williamson, E. (1997) Liposomally-encapsulated ricin toxoid vaccine delivered intratracheally elicits a good immune response and protects against a lethal pulmonary dose of ricin toxin. Vaccine, 15, 1933-1939. 

Kende, M., Yan, C., Hewetson, J., Frick, M.A., Rill, W.L. and Tammariello, R. (2002) Oral immunization of mice with ricin toxoid vaccine encapsulated in polymeric microspheres against aerosol challenge. Vaccine, 20, 1681-1691. 

Active immunization with ricin toxoid is designed to provide long-lasting protection against a subsequent ricin challenge. Since inhalation... 

A potential problem with ricin toxoid immunization is that at least some preparations have shown a tendency to revert to the toxic form when stored at room temperature or 4°C (Griffiths et al, 1998). This has led to the examination of different vaccination candidates based upon ricin A chain (Griffiths et al, 1998). The challenge is to develop a ricin A chain derivative that is sufficiently immunogenic to be used as a vaccine without having the enzymatic activity of the complete ricin A chain molecule. 

Inherent barriers to the production and widespread use of the formalin-inactivated toxoid, including local reactogenicity, the potential for reversion, and expectations of a difficult manufacturing process, have led to an ongoing interest in development of improved ricin vaccines (Lord et al., 1987 Lemley and Wright, 1992 Lemley and Creasia, 1995 Griffiths et al., 1999 Smallshaw et al., 2002 Marsden et al., 2004 Olson et al., 2004). 

Griffiths, G.D., Phillips, G.J. and Bailey, S.C. (1999) Comparison of the quality of protection elicited by toxoid and peptide liposomal vaccine formulations against ricin as assessed by markers of inflammation. Vaccine, 17, 2562-2568. 

Griffiths GD, Bailey SC, Hambrook JL et al. (1998). Local and systemic responses against ricin toxin promoted by toxoid or peptide vaccines alone or in liposomal formulations. Vaccine, 16, 530-535. 

Hewetson JF, Rivera VP, Lemley PV et al. (1995). A formalinized toxoid for protection of mice from inhaled ricin. Vaccine Res, 4, 179-187. 

F. Vaccination. Vaccination is the preferred method of biological defense. Fully licensed vaccines are currently available for anthrax, cholera, plague and smallpox. Vaccines for botulinum toxoid, Q fever, Rift Valley fever, tularemia, and VEE currently exist as IND products and would be available only under protocol with informed consent, therefore would not be readily available on the battlefield. No vaccine is currently available either FDA licensed or under IND status, for glanders, brucellosis, Staphylococcus enterotoxin B, ricin, or T-2 mycotoxins. 

Continued investigation of antiricin antibodies as well as formalin-treated toxoid immunization is appropriate, but should be considered low priority for domestic preparedness due to the high cost of developing a licensed product, the limited potential of mass exposure to ricin, and the low probability of any potential means of developing a mass-exposure technique. 

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