Immune response and protective efficacy of S9 ribosomal protein of  Streptococcus pneumoniae  in a model of sepsis.
Vaccination is the most promising strategy to reduce the incidence of pneumococcal infection. Although there are vaccines available, all of them are based on polysaccharide antigens (conjugated or not). In addition to their high cost, those vaccines do not cover all serotypes. To overcome these hindrances, we evaluated the immunogenicity and the protective efficacy of the S9 ribosomal protein of  Streptococcus pneumoniae  with the aim of developing a protein-based vaccine in the future. The gene encoding the S9 ribosomal protein was cloned in pET21-a expression vector, and the recombinant S9 protein was used to immunize mice. Significantly higher levels of anti-S9 immunoglobulin G were achieved (with predominance of immunoglobulin G1) in comparison with the control. Antibodies elicited against S. pneumoniae protein extract in rabbit recognized the recombinant S9 protein by Western blot, thus demonstrating its immunogenicity. Moreover, mice immunized with recombinant S9 protein and challenged with a virulent strain of S. pneumoniae presented a significant reduction of bacteremia after 24 h of infection as compared with the control. However, in the S9-immunized mice the onset of death was insignificantly delayed, but all of them died by the fourth day postinfection.
Research and Development Center, Ezequiel Dias Foundation (Funed), Belo Horizonte, MG, Brazil.
Helton Fernandes
HF
Araújo
Patrícia Cota
PC
Campos
Dhian Renato Almeida
DR
Camargo
Filippe Nonato Roberto
FN
Pereira
Michelle Lara
ML
Samuel
Marluce Aparecida Assunção
MA
Oliveira
Consuelo Latorre
CL
Fortes-Dias
Sophie Yvette
SY
Leclercq
D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D001428:Bacterial Vaccines / Q000276:immunology; D004195:Disease Models, Animal; D051379:Mice; D011008:Pneumococcal Infections / Q000276:immunology / Q000401:mortality / Q000517:prevention & control; D011817:Rabbits; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification; D000091243:Ribosomal Protein S9; D012269:Ribosomal Proteins / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification; D018805:Sepsis / Q000276:immunology* / Q000401:mortality / Q000517:prevention & control; D013296:Streptococcus pneumoniae / Q000235:genetics* / Q000276:immunology*
D000907:Antibodies, Bacterial; D001428:Bacterial Vaccines; D011994:Recombinant Proteins; D000091243:Ribosomal Protein S9; D012269:Ribosomal Proteins