Caracterização da antigenicidade e do efeito protetor em modelo murino de proteínas recombinantes de Erysipelothrix rhusiopathiae candidatas a antígenos vacinais
Resumen
Erysipelothrix rhusiopathiae is a gram-positive, bacilliform, and encapsulated bacterium that
causes swine erysipelas, a disease characterized by skin lesions and other symptoms such
as septicemia, arthritis, and endocarditis in the affected animals. Vaccines from attenuated or
inactive E. rhusiopathiae cells are available on the market, but they are not so effective to
overcome the acute form of the disease. Also, they can aggravate the symptoms of the
chronic form. E. rhusiopathiae extracellular proteins were detected as potentially antigenic. It
has previously been cloned the coding sequences for 11 genes related to these proteins in
the pJET1.2/blunt vector and pET28 expression vector. The present work aims to perform
heterologous expression of four of these proteins, named P1, P3, P6, and P7, for functional
characterization of their in vitro antigenicity and protection character against E. rhusiopathiae
in a murine model. For this, the following was performed: production of recombinant forms of
P1 and P7 proteins in Escherichia coli Rosetta strain (DE3) and of P3 and P6 proteins in
BL21 (DE3) strain; purification of the four recombinant proteins by affinity and molecular
exclusion chromatography. All recombinant proteins were successfully expressed in E. coli
and were functionally evaluated for: in vitro antigenicity by Western blot and ELISA, using
sera from swine immunized with the available commercial vaccine; protective effect in mice
by challenging with E. rhusiopathiae and monitoring of the animals survival; in vitro
antigenicity by ELISA using sera from mice immunized with recombinant proteins and
challenged with E. rhusiopathiae. The results demonstrated that all proteins are antigenic in
pigs and mice, but only P7 protein provides survival for at least one of the six challenged
mice. This work leads to the conclusion that the immunoproteomic analysis was a useful tool
for the discovery of new antigens of E. rhusiopathiae, however, the antigenic proteins have
limited protection effect for the proposals of effective new vaccines. New studies need to be
carried out in order to verify whether the protective effect of the recombinant proteins studied
here can be enhanced by changing the dosage or administration routes, or even by a
combination of P7 protein with other antigenic proteins for a greater protective efficacy
against E. rhusiopathiae.
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