Route and type of nutrition influence mucosal immunity to bacterial pneumonia

Objective To develop a model of established respiratory immunity against Ps eudomonas aeruginosa pneumonia and to investigate the effects of route and type of nutrition on this immunity. Summary Background Data Diet influences the ability of gut-associated lymph oid tissue (GALT) to maintain mucosal immunity. Complex enteral diets and c how maintain normal GALT populations against established IgA-mediated antiv iral respiratory immunity. Both intravenous and intragastric total parenter al nutrition (TPN) produce GALT atrophy, but only intragastric TPN preserve s established antiviral immunity. The authors hypothesized that both GALT-d epleting diets (intragastric and intravenous TPN) would impair immunity aga inst bacterial pneumonia. Methods P. aeruginosa was administered intratracheally to determine the mor tality rate at increasing doses, and liposomes containing P. aeruginosa ant igens were used to generate effective respiratory immunization. In the fina l experiment, mice received liposomes containing P. aeruginosa antigens to establish immunity and then were randomized to chow, complex enteral diets, intragastric TPN, or intravenous TPN, After 5 days of diet, mice received live intratracheal P. aeruginosa, and the death rate was recorded at 24 and 48 hours, Results The LD50 and LD100 were 9 x10(7) and 12 x 10(7), respectively. Immu nization reduced the mortality rate from 66% to 12%. This immunization was maintained in mice fed chow or a complex enteral diet and was lost in anima ls receiving intravenous TPN, Intragastric TPN partially preserved this res piratory immunity. Conclusions Protection against bacterial pneumonia can be induced by prior antigenic immunization. This protection is lost with intravenous TPN, parti ally preserved with a chemically defined enteral diet, and completely prese rved with chow or complex enteral diets. Both route and type of nutrition i nfluence antibacterial respiratory tract immunity.