LIPOSOMALLY-ENCAPSULATED RICIN TOXOID VACCINE DELIVERED INTRATRACHEALLY ELICITS A GOOD IMMUNE-RESPONSE AND PROTECTS AGAINST A LETHAL PULMONARY DOSE OF RICIN TOXIN

A small study was performed to examine whether the instillation of ric in toroid vaccine into the lungs of Porton rats offered protection fro m lethal effects of subsequent intratracheal challenge with ricin toxi n, Further the immune response to liposomally-encapsulated vaccine and the protection offered was compared with vaccine either adsorbed to A lhydrogel adjuvant or as a simple aqueous solution. The formaldehyde-t reated ricin toxin vaccine (RTV) was administered at two dose levels, 500 and 100 mu g kg(-1) body weight to groups of rats, on two occasion s by intratracheal instillation, Liposomally-encapsulated vaccine (LRT V) produced a higher titre of ricin-specific antibodies than Alhydroge l-vaccine (ARTV) and vaccine solution., When challenged with 3 LD50 of ricin by intratracheal instillation 7 weeks after the second vaccine instillation, all rats in both LRTV dose groups survived with minimal signs of incapacitation, Analysis of antibody secretion by spleen cell s, 14 days post challenge, showed that the Ige isotype in the LRTV gro up was significantly higher than that in the ARTV and RTV groups and a lso that the proportion of specific IgA in lung fluid was higher in th e LRTV group than in the ARTV and RTV groups, The results of this stud y indicate that effective vaccinations against inhaled ricin could be achieved with liposomally-encapsulated ricin toroid, via the lung and should be investigated further. (C) 1997 Elsevier Science Ltd.