Accuri C6 Flow Cytometer System
Originally published online as doi:10.1189/jlb.1008653 on August 3, 2009

Published online before print August 3, 2009
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(Journal of Leukocyte Biology. 2009;86:1259-1268.)
© 2009 Society for Leukocyte Biology

Antigen delivery by {alpha}2-macroglobulin enhances the cytotoxic T lymphocyte response

Edith V. Bowers, Jeffrey J. Horvath, Jennifer E. Bond, George J. Cianciolo and Salvatore V. Pizzo1

Department of Pathology, Duke University Medical Center, Durham, North Carolina, USA

1. Correspondence: Department of Pathology, Duke University Medical Center, 200 Trent Dr., Durham, NC 27710, USA. E-mail: Pizzo001{at}mc.duke.edu

ABSTRACT

{alpha}2M* targets antigens to APCs for rapid internalization, processing, and presentation. When used as an antigen-delivery vehicle, {alpha}2M* amplifies MHC class II presentation, as demonstrated by increased antibody titers. Recent evidence, however, suggests that {alpha}2M* encapsulation may also enhance antigen-specific CTL immunity. In this study, we demonstrate that {alpha}2M*-delivered antigen (OVA) enhances the production of specific in vitro and in vivo CTL responses. Murine splenocytes expressing a transgenic TCR specific for CTL peptide OVA257–264 (SIINFEKL) demonstrated up to 25-fold greater IFN-{gamma} and IL-2 secretion when treated in vitro with {alpha}2M*-OVA compared with soluble OVA. The frequency of IFN-{gamma}-producing cells was increased ~15-fold, as measured by ELISPOT. Expansion of the OVA-specific CD8+ T cell population, as assayed by tetramer binding and [3H]thymidine incorporation, and OVA-specific cell-mediated cytotoxicity, as determined by a flow cytometric assay, were also enhanced significantly by {alpha}2M*-OVA. Furthermore, significant CTL responses were observed at antigen doses tenfold lower than those required with OVA alone. Finally, we also observed enhanced humoral and CTL responses by naïve mice following intradermal immunization with {alpha}2M*-OVA. These {alpha}2M*-OVA-immunized mice demonstrated increased protection against a s.c.-implanted, OVA-expressing tumor, as demonstrated by delayed tumor growth and prolonged animal survival. The observation that {alpha}2M*-mediated antigen delivery elicits specific CTL responses suggests the cross-presentation of antigen onto MHC class I. These results support {alpha}2M* as an effective antigen-delivery system that may be particularly useful for vaccines based on weakly immunogenic subunits or requiring dose sparing.

Key Words: vaccination • cytokines • spleen