Immunocytochemical Colocalization of Specific Immunoglobulin A with Sendai Virus Protein in Infected Polarized Epithelium |
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| Authors: | Hisashi Fujioka Steven N. Emancipator Masamichi Aikawa Dennis S. Huang Frank Blatnik Tracy Karban Kristin DeFife Mary B. Mazanec |
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| Affiliation: | From the *Institute of Pathology, the ‡Department of Pathology and the §Department of Medicine, Case Western Reserve University, Cleveland, Ohio 44106; and ‖The Institute of Medical Sciences, Tokai University, Boseidai, Isehara, Kanagawa 259-1193, Japan |
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| Abstract: | Immunoglobulin (Ig)A provides the initial immune barrier to viruses at mucosal surfaces. Specific IgA interrupts viral replication in polarized epithelium during receptor-mediated transport, probably by binding to newly synthesized viral proteins. Here, we demonstrate by immunoelectron microscopy that specific IgA monoclonal antibodies (mAbs) accumulate within Sendai virus–infected polarized cell monolayers and colocalize with the hemagglutinin– neuraminidase (HN) viral protein in a novel intracellular structure. Neither IgG specific for HN nor irrelevant IgA mAbs colocalize with viral protein. Treatment of cultures with viral-specific IgA but not with viral-specific IgG or irrelevant IgA decreases viral titers. These observations provide definitive ultrastructural evidence of a subcellular compartment in which specific IgA and viral envelope proteins interact, further strengthening our hypothesis of intracellular neutralization of virus by specific IgA antibodies. Our results have important implications for intracellular protein trafficking, viral replication, and viral vaccine development. |
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| Keywords: | immunoglobulin A, Sendai virus, mucosal immunity, colocalization, hemagglutinin– neuraminidase protein |
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