Rabbit ocular mucosal immune system stimulated by HSV–1 gD peptides mixed with the mucosal adjuvant CpG and administered mucosally as eye drops

Abstract

Abstract: : Purpose:Mucosal surfaces constitute an impressive first–line defense system that is frequently exposed to an array of exogenous antigens and pathogens. The Ocular Mucosal Immune System or OMIS, is the immune barrier that protects the surface of the eye. OMIS plays a crucial role in ocular immunity, tolerance and inflammation. Understanding and being able to manipulate OMISimmunity is the first step in developing protection against serious external–ocular infections, such as HSV. Methods: We conducted ocular immunizations using several well–characterized immunogenic peptides derived from herpes simplex virus type 1 (HSV–1) glycoprotein–D, together with CpG mucosal adjuvant in rabbits. All rabbits received two eye drops in both eyes (given at 21 day intervals for 3 doses) of a pool of peptides (100microg each peptide) + CpG 2007 mucosal adjuvant (100microg of CpG per dose) in a total volume of 25microL. Control animals received the CpG 2007 alone. The CpG 2007 adjuvant was chosen because it was previously shown to enhance B and T cell immunogenicity in rabbits (Coley Pharmaceutical Group). Animals were studied for 3 mos for ocular mucosal and systemic B and T cell responses. Results: Ocular administration of HSV–1 gD peptides containing predicted B and T cell epitopes emulsified with CpG DNA induced both systemic and ocular mucosal immune responses in rabbits. Both IgA and IgG antibody responses were obtained against each of the individual peptides composing the pool. Peptide and HSV–1 specific sIgA was elicited in tears. Peptide specific T cells were induced in the conjunctiva and in PBMCs . Conclusions: These data prove that topical administration of HSV–1 peptide epitopes and CpG adjuvant stimulated (a) HSV specific local antibody response (tear IgA & IgG), (b) a local ocular T cell response (predominantly Th–1), and (c) systemic cellular immune responses.

Keywords: herpes simplex virus • immunomodulation/immunoregulation • antigen presentation/processing