Expression of Streptococcus pneumoniae PspA1 and PspA3 antigens in lactic bacteria.

Author(s)

Ivana Barros de Campos

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Ciências Biomédicas (ICB/SDI)
• Defense date: 2006-03-20

Examining board members

Paulo Lee Ho; Maria Cristina de Cunto Brandileone; Luis Carlos de Souza Ferreira

• Advisor: Paulo Lee Ho

Abstract

Streptococcus pneumoniae is an important respiratory pathogen that causes pneumonia, meningitis and otitis media. The current vaccine in use is composed of capsular polysaccharides (PS) derived from 23 different serotypes, and has little efficacy in young children, elderly and in patients with immunodeficiencies. PS-protein conjugate vaccines are more effective, but their production is expensive for widespread use. Moreover, the increase in antibiotic-resistant S. pneumoniae clinical isolates supports the development of new and more effective vaccines. The use of live recombinant lactic acid bacteria (LAB) as antigen delivery and presentation systems represents a promising strategy for mucosal vaccination, since they are generally regarded as safe bacteria (GRAS-status) and are able to elicit both systemic and mucosal immune responses. In this work, Lactococcus lactis, Lactobacillus casei and Lactobacillus helveticus were engineered for constitutive expression of PspA (Pneumococcal Surface Protein A), an important S. pneumoniae virulence factor. Recombinant bacteria were able to express PspA in two cellular locations: intracellular or cell-surface exposed, as analyzed by Western-blot, using polyclonal antibodies produced against recombinant PspA purified from E. coli. Stimulation of humoral immune system was evaluated in terms of production of anti-PspA IgG in the sera or IgA in saliva, after intranasal administration of recombinant LAB in mice. (AU)