Clinical trials - edible vaccines

Antigen expression in plants has been successfully shown in the past, like LT-B (ETEC) in tobacco and potato, rabies virus-G protein in tomato, HBsAg in tobacco and potato, norwalk virus in tobacco and potato; CT-B (Vibrio cholerae) in potato.

a.ETEC

Charles Arntzen at Boyce Thompson Institute, USA, accomplished the first published successful human trial in 1997. Eleven volunteers were fed raw transgenic potatoes expressing LT-B. Ten of these individuals developed neutralizing antibodies and six developed mucosal responses.

b.Norwalk virus

Seroconversion is the development of detectable specific antibodies to microorganisms in the serum as a result of infection or immunization.
Nineteen out of 20 people fed with transgenic potato expressing Norwalk virus(cause of dysentery) antigen showed seroconversion.

c.Cholera

Transgenic potato with CT-B gene of Vibrio cholerae was shown to be effective in mice. Co-expression of mutant cholera toxin subunit A (mCT-A) and LT-B in crop seed has been shown to be effective by nasal administration and is extremely practical.

References:

a. http://www.nature.com/embor/journal/v1/n5/full/embor535.html

b.Lal P, Ramachandran VG, Goyal R, Sharma R. Edible vaccines: Current status and future. Indian J Med Microbiol [serial online] 2007 [cited 2008 May 2];25:93-102. Available from: http://www.ijmm.org/text.asp?2007/25/2/93/32713