Accessing Natural Killer Cell Antibody-Dependent Cell-Mediated Cytotoxicity Via CMV-Specific Hyperimmune Human Immunoglobulin
Sunday, March 6, 2016
South Exhibit Hall H (Convention Center)
Anastasiya Yermakova, Ph.D., Pinaki B. Banerjee, Ph.D., Levi B. Watkin, Ph.D., Alexandre F. Carisey, Ph.D., Cindy De Los Santos, Gail J. Demmler-Harrison, M.D., Jordan S. Orange, MD PhD FAAAAI
Rationale: Natural killer (NK) cells are essential in control of Human Cytomegalovirus (HCMV) as demonstrated by patients lacking these cells. NK cells kill both by spontaneous cytotoxicity against infected cells and by recognizing those coated with IgG via antibody-dependent cell-mediated cytotoxicity (ADCC). Mechanisms underlying the latter are less well understood.  Since polyclonal human IgG is used in the treatment of certain HCMV infections, we hypothesized that CMV-specific IgG accesses a specific and favorable biology from NK cells via antiviral ADCC which is accentuated further by therapeutic hyperimmune anti-CMV IgG (CMV-IVIG).

Methods: The efficiency of CMV-IVIG versus standard-IVIG in recognizing HCMV-infected human fibroblasts was measured using imaging flow cytometry and frequency of conjugation with NK cells and mobilization of their cytolytic machinery determined via time-lapse confocal microscopy with highly quantitative image analysis.

Results: We demonstrate that CMV-IVIG detects infected cells more efficiently than standard-IVIG or spontaneous NK cell activity, leading to a higher frequency of conjugate formation between NK cells and HCMV-infected fibroblasts. Further, coating of HCMV-infected fibroblasts with CMV-IVIG imparts an increased efficiency to NK cell cytotoxicity via an increase in polarization of lytic machinery within the NK cell.

Conclusions: CMV-IVIG imparts increased CMV eradication efficiency to NK cells via antiviral ADCC as evidenced by an increase in recognition of infected fibroblasts, greater conjugate formation and more efficient organization of NK cytolytic machinery.  The quantitative assessments also underscore unique attributes of antiviral ADCC relative to spontaneous cytotoxicity against HCMV-infected cells.