355 Unraveling and targeting the innate immune response in Multisystem Inflammatory Syndrome in Children (MIS-C)

OBJECTIVES/GOALS: The innate immune responses to Multisystem Inflammatory Syndrome in Children (MIS-C) are not fully known. Using samples from MIS-C, we will assess the cellular responses and develop a novel Tri-Specific Killer Engager (TRiKE) that engages innate immune cells to improve those responses. METHODS/STUDY POPULATION: We collected blood samples from 60 pediatric patients from which we isolated plasma and peripheral blood mononuclear cells. We received blood samples from 13 MIS-C, 32 severe acute COVID, 5 COVID-19 asymptomatic, and 15 COVID-19 negative patients. Using plasma, we then performed ELISAs to determine IgG antibody levels against SARS-CoV-2 and plaque reduction neutralization tests to determine neutralizing antibody functions. We isolated DNA to look at Fc receptor genetics. We also utilized utilize flow cytometry assays determine the phagocytosis and killing abilities of the innate cells from these patients. This data will be correlated with clinical outcomes. Additionally, we have developed a novel SARS-CoV-2 TRiKE which directs natural killer (NK) cell killing specifically to of COVID-19 infected cells. RESULTS/ANTICIPATED RESULTS: MIS-C patients had higher IgG antibody titers against SARS-CoV-2 compared to children with symptomatic or asymptomatic COVID. MIS-C patients also neutralized SARS-CoV-2 more effectively than children with acute symptomatic or asymptomatic COVID-19. We found natural killer cells and monocytes are dysfunctional in MIS-C patients and do not kill SARS-CoV-2 infected cells as well. Specifically, NK cells do not kill COVID-19 infected cells as well. To combat this, we have successfully generated and are now testing a Tri-Specific Killer engager (TRiKE) which binds one ends to NK cells, one end to the Spike protein on COVID-19 infected cells and contains IL-15 to improve NK cell function. We anticipate that we can improve NK cell killing of COVID-19 infected cells with this TRiKE. DISCUSSION/SIGNIFICANCE: We found that MIS-C patients have antibodies that can neutralize SARS-CoV-2 but that that innate immune cells that engage antibodies are dysfunctional. We are have successfully developed and are targeting this response with a TRiKE to improve innate immune cell functional; this may serve as an adjunctive therapeutic if proven successful.