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212 Preferential Induction of Mucosal IgA Abs to the ELDKWA gp41 Epitope of HIV-1 following Parenteral Immunization in the Presence of the Pan DR Epitope
N. Decroix, C. P. Quan, and J.-P. Bouvet*
INSERM, Paris, France
Background: We have recently shown the induction of Abs to ELDKWA in the mucosa following parenteral administration of this key peptide coupled with tetanus toxoid (TT). Here we investigate possible improvements this response to provide a mucosal vaccine.
Methods: Synthetic ELDKWA-containing peptides were coupled with proteins by disulfide exchange, or synthesized on-line with the artificial peptidic immunogen Pan DR epitope (PADRE). BALB/c mice were I.M. injected every month in the presence or absence of alum. Vaginal fluids (VF) were collected by lavage with PBS and pooled. Intracellular Abs were extracted from mucosal (intestinal) and systemic (splenic) tissues according to the perfusion-extraction method. IgA and IgG Abs were assayed by ELISA against the EKNEQELLELDKWASLWC sequence coupled with OVA.
Results: Both IgA and IgG Abs were detected in the VF, confirming the validity of this method. As a carrier of the ELDKWASLWC peptide, fragment C of the tetanus toxin led to a higher IgA response, but its potential toxicity and cost rule out its use as a vaccine. Comparison between the monomeric and dimeric forms of ELDKWA coupled with TT showed similar results. Immunization with these protein-coupled peptides led to higher IgA responses in the presence of adjuvant. The use of ELDKWA synthesized on-line with PADRE displayed the best IgA responses in VF. Of major interest, the IgA response to this aKXVAAWTLKAAaZELDKWASLW soluble molecule largely predominated over IgG, the best dose being 1 mg/injection. Moreover, investigation of the intracellular Abs showed a preferential response in mucosal over splenic tissues. This response was primarily of the IgA isotype, whereas minor responses were observed in the serum.
Conclusions: We demonstrate here that parenteral immunization against ELDKWA synthesized on-line with the potent immunogen PADRE may induce an IgA Ab response preferentially triggered in the mucosal immune system, including VF and gut. The safety of this vaccine (which does not contain any adjuvant, animal component, bacterial toxin, or live organisms) and its possible industrial synthesis at a reasonable cost suggest a new approach for mucosal vaccinations both against AIDS and other mucosa-transmitted diseases.
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