Vaccine properties of antigens entrapped in microparticles produced
by spray-drying technique and using various polyester polymers.
Baras B, Benoit M, Poulain-Godefroy O, Schacht A, Capron A, Gillard
J, Riveau G
Laboratoire des Relations Hote-Parasite et Strategies Vaccinales, INSERM
U167, Institut Pasteur de Lille, 1 rue du Professeur Calmette, BP-245,
F-59019, Lille, France. ipv@pasteur-lille.fr
The present study investigated the suitability of various microparticles
produced by spray-drying technique to entrap and preserve the physiochemical
and biological properties of an antigen. These microparticles were constituted
either by poly(lactide) polymers characterized by various molecular weight
or poly(lactide-co-glycolide) polymers. The recombinant 28 kDa glutathione
S-transferase of Schistosoma mansoni (rSm28GST) characterized by major
epitopes involved in the active site of this enzyme was selected as model
antigen. The microparticles were characterized by a mean size </=5 microm
and an antigen loading of approximately 2% (w/w). The analysis by SDS-PAGE
electrophoresis of the rSm28GST released from microparticles confirmed
the conservation of its physicochemical characteristics. The conservation
of the native structure of the entrapped antigen was confirmed by detecting
its enzymatic activity after release from microparticles. A single intraperitoneal
immunization of mice with rSm28GST entrapped in microparticles resulted
in a specific antibody response, which remained high for at least 7 months.
The analysis of the isotype profile indicated that immunized mice primarily
produced anti-rSm28GST immunoglobulin (Ig) G1 with the coexistence of lower
IgG2a and IgG2b levels. Finally, the recognition of the major epitopic
regions and the neutralization of the enzymatic activity of the rSm28GST
by the antisera confirmed the specificity of the response against the native
structure of the antigen. These results confirmed the integrity of the
entrapped antigen. Moreover, our results supported the hypothesis that
the duration of antigen release is the limiting factor for the duration
of antibody production. Indeed, the use of polymers characterized by different
molecular weights allowed us to modify the duration of the immune response.
Together, these results demonstrated that microencapsulation of an antigen
by spray-drying preserved its crucial characteristics required to
generate an effective humoral immune response after a single-dose administration.
PMID: 10618547, UI: 20087306