Immunization of mice with single PspA fragments induces antibodies capable of mediating complement deposition on different pneumococcal strains and cross-protection
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2010-03
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PspA is an important candidate for a vaccine with serotype-independent immunity against pneumococcal
infections. Based on sequence relatedness, PspA has been classified into three families comprising six clades.
We have previously addressed the cross-reactivity of antibodies against PspA fragments containing the
N-terminal and proline-rich regions of PspA from clades 1 to 5 (PspA1, PspA2, PspA3, PspA4, and PspA5) by
Western blot analysis and reported that anti-PspA4 and anti-PspA5 were able to recognize pneumococci
expressing PspA proteins from all of the clades analyzed. We have now analyzed the functional capacity of these
antibodies to bind and to mediate complement deposition on intact bacteria in vitro. Our results show that both
PspA4 and PspA5 elicit antibodies that are able to bind and to mediate complement deposition efficiently on
pneumococcal strains bearing PspA proteins from clades 1 to 5. Moreover, mice immunized with PspA4 and
PspA5 were protected against an intranasal lethal challenge with strains expressing PspA proteins from the
two major families. PspA4 and PspA5 are thus able to induce antibodies with a high degree of cross-reactivity
in vitro, which is reflected in cross-protection of mice. We have also analyzed the contribution of the nonproline
(NonPro) block within the conserved proline-rich region to the reactivity of anti-PspA antibodies, and the
results indicate that N-terminal -helical region, the blocks of proline repeats, and the NonPro region can
influence the degree of cross-reactivity of antibodies to PspA.
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Moreno, Adriana T. et. al. Immunization of mice with single PspA fragments induces antibodies capable of mediating complement deposition on different pneumococcal strains and cross-protection. Clinical and Vaccine Immunology, Washington, v. 17, n. 3, p. 439-446, Mar. 2010.