Vaccine strategies against Pseudomonas aeruginosa infection in the lung.

Pseudomonas aeruginosa is an environmentally ubiquitous, extracellular opportunistic gram-negative bacteria that causes significant morbidity and mortality to a disproportionately high degree for infections with this bacteria compared with other gram-negative bacteria. Patients at particular risk of infection are those with compromised respiratory function, in intensive-care support and taking immunocompromising pharmaceutical agents. Once acquired, infection is difficult to eradicate with chemotherapy and attempts to vaccinate against infection have been of little success. Over the past five years, we have pursued the concept of mucosal immunisation against respiratory infection with P. aeruginosa. Initial studies in an acute animal model clearly demonstrated that mucosal immunisation with a killed whole bacterial cell preparation could induce protective immune responses in the lung. Subsequent studies have shown that the protective immune mechanisms were dependent on antigen specific CD4+ T cells, the activation of alveolar macrophages, the recruitment and activation of polymorphs, predominantly neutrophils, the controlled secretion of TNF-alpha, IL-1 and IFN gamma and the presence of antibody. We have hypothesised that the protective response is under the control of T cells. A pre-clinical human trial of an oral whole killed cell preparation has been completed with no adverse side effects. A limited open trial in patients with bronchiectasis has also been completed. Preliminary analysis of the results has demonstrated that after oral vaccination, specific lymphocyte responses were observed to P. aeruginosa.