diseases in children under 5-year-old. Vaccine has been used
as an indispensable strategy to prevent S. pneumoniae infection
for more than 30 years. Our previous studies confirmed
that mucosal immunization with live attenuated strain SPY1
can protect mice against nasopharyngeal colonization of S.
pneumoniae and lethal pneumococcal infection, and the
protective effects are comparable with those induced by commercially
available 23-valent polysaccharide vaccine. However,
live attenuated vaccine SPY1 needs four inoculations to
get satisfactory protective effect, which may increase the risk
of virulence recovery. It is reported that heterologous primeboost
approach is more effective than homologous primeboost
approach. In the present study, to decrease the doses
of live SPY1 and improve the safety of SPY1 vaccine, we immunized
mice with SPY1 and DnaJ protein alternately. Our
results
showed that heterologous prime-boost immunization
with SPY1 and DnaJ protein could significantly reduce
the colonization of S. pneumoniae in the respiratory tract of
mice, and induce stronger Th1 and Th17 cellular immune
responses than SPY1 alone. These results indicate heterologous
prime-boost immunization method not only elicits
better protective effect than SPY1 alone, but also reduces the
doses of live SPY1 and decreases the risk of SPY1 vaccine.
This work is the first time to study the protective efficiency
with two different forms of S. pneumoniae candidate vaccine,
and provides a new strategy for the development of S. pneumoniae
vaccine.