Streptococcus pneumoniae (
pneumococcus) is a
human pathogen that can cause
otitis media,
pneumonia and, in severe cases,
meningitis and
bacteremia. The
pneumococcus expresses PotD, a
protein belonging to the
polyamines transporter complex called PotABCD. PotD is a
membrane-associated protein that binds
polyamines and has been shown to be important for
virulence. In this
work we demonstrate that subcutaneous
immunization with rPotD reduces the
bacterial load in the nasal
tissue of
mice, following intranasal challenge with a type 6B
pneumococcus. The protective effect correlated with the induction of high levels of
antibodies in the immunized group; the
antibodies were able to increase bacterial
phagocytosis by
mouse peritoneal
cells. The
cellular immune response was characterized by the
production of
gamma-interferon,
IL-2 and
IL-17 by splenocytes and
nitric oxide by peritoneal
cells of immunized
mice, upon stimulation with rPotD. Taken together our results suggest that PotD is a promising candidate to be included in a
protein based
pneumococcal vaccine, able to induce phagocytic
antibodies, a Th1
cellular immune response and
production of
IL-17, reducing nasopharyngeal colonization, the main event responsible for
transmission of pneumococci in
humans.