Cross-reactive influenza-specific antibody-dependent cellular cytotoxicity in intravenous immunoglobulin as a potential therapeutic against emerging influenza viruses.

Background: Intravenous immunoglobulin (IVIG) is a purified pool of human antibodies from thousands of donors that is used to prevent or treat primary immune deficiency, several infectious diseases, and autoimmune diseases. The antibodies that mediate antibody-dependent cellular cytotoxicity (ADCC) against heterologous influenza strains may be present in IVIG preparations.
Methods: We tested 8 IVIG preparations prior to the 2009 H1N1 swine-origin influenza pandemic and 10 IVIG preparations made after 2010 for their ability to mediate influenza-specific ADCC.
Results: ADCC mediating antibodies to A(H1N1)pdm09 hemagglutinin (HA) and neuraminidase (NA) were detected in IVIG preparations prior to the 2009-H1N1 pandemic. The HA-specific ADCC targeted both the HA1 and HA2 regions of A(H1N1)pdm09 HA and was capable of recognizing a broad range of HA proteins including those from recent avian influenza strains A(H5N1) and A(H7N9). The low but detectable ADCC recognition of A(H7N9) was likely due to rare individuals in the population contributing cross-reactive antibodies to IVIG.
Conclusions: IVIG preparations contain broadly cross-reactive ADCC mediating antibodies. IVIG may provide at least some level of protection for individuals at high risk of severe influenza disease, especially during influenza pandemics prior to the development of effective vaccines.
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