Construction of Streptococcus pneumoniae strains derived from TIGR4 expressing different variants of the antigen PspA (Pneumococcal surface protein A)

• Grant number: 16/14316-8
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: October 01, 2016
• End date: September 30, 2017
• Field of knowledge: Biological Sciences - Biochemistry - Molecular Biology
• Principal Investigator: Eliane Namie Miyaji
• Grantee: Jéssica Gunther Montero Fanizzi
• Host Institution: Instituto Butantan. Secretaria da Saúde (São Paulo - Estado). São Paulo , SP, Brazil

Abstract

Streptococcus pneumoniae is an important human pathogen, causing severe diseases such as pneumonia, bacteremia, sepsis and meningitis. The currently available vaccines are based on the response against the capsular polysaccharide, but they have some shortcomings such as high cost and restricted serotype coverage. The development of new vaccines against pneumococcal infections thus remains a priority and alternative strategies are being pursued, such as the use of protein antigens. Among several proteins currently being studied as vaccine antigens, PspA (Pneumococcal surface protein A) is one of the most promising ones. PspA shows variability between strains and our group has previously shown that some PspA variants are able to induce antibodies with broader cross-reactivity with different pneumococcal strains and also to induce cross-protection against invasive disease and colonization models in mice. Recently, we have established a model of co-colonization of mice with clinical isolates expressing different PspA variants. Co-colonization is very common in children and an ideal vaccine antigen should lead to the reduction of both colonizing strains without favoring the outgrowth of one of the strains. This project aims at improving the co-colonization model through the construction of pneumococci derived from the TIGR4 strain expressing different PspAs. These new strains will have the exact same genetic background, differering only in the expressed PspA. We will use the Sweet Janus Cassette, which allows gene knockout followed by allelic exchange. Antibiotic resistance cassettes will then be introduced in the obtained strains downstream of the ami operon. These cassettes will substitute the truncated element IS1167 and will allow the differentiation of the bacteria in the co-colonization model of the nasopharynx. (AU)