RSV-specific ADCC in different age groups; the development of an ADCC killing assay with serum antibodies

Abstract

RSV is a globally prevalent virus which is particularly problematic at an early age. Research speculates that young children have a different antibody-dependent cellular cytotoxicity (ADCC) capacity compared to adults regarding RSV. However, it remains undecided if this difference causes higher symptoms in young children. ADCC is generally examined through an antibody-dependent Natural Killer cell activation (ADNKA) format. This format uses viral antigen to measure Natural Killer (NK)-cell activation and does not represent actual killing of an infected cell. The research described in this paper implements and optimises an ADCC killing assay. Here, a lung epithelial target cell line is infected with RSV, inducing presentation of whole virus antigen. This cell line is co-incubated with RSV-antibody containing serum, whereafter the opsonised cells are incubated with a NK-92 effector cell line. The killing of the target cell line is measured by flow cytometry. In this study, we optimised different aspects of the ADCC killing assay. These aspects include: the infection incubation of the target cells, the optimal choice of target cell, the optimal choice of NK cell, and the optimal serum dilution. The optimisation was successful. However, limitations to the target cell killing emerged, which should be further optimised for a more conclusive assay. Finally, we implemented the optimised ADCC killing assay using serum of different age groups, comparing the ADCC capabilities of serum antibodies from 24-month-old children and adults. We found a correlation between ADCC and IgG serum antibody levels. The ADCC capabilities of adult serum antibodies seemed to be higher compared to the 24-month-old antibodies. However, this result was yielded from a pilot study. Therefore, more validation and research should be implemented. In conclusion, we created an ADCC assay which can be implemented for further research studying RSV-specific ADCC. While there is still room for improvement within the assay, it is able to produce results about ADCC capabilities on RSV-infected target cells.