Activation of anti-SARS-CoV-2 human CTLs by extracellular vesicles
engineered with the N viral protein
Abstract
We investigated an innovative anti-SARS-CoV-2 immune strategy finalized
to oral administration of extracellular vesicles (EVs) inducing an
anti-SARS-CoV-2 N CD8+ T cytotoxic lymphocyte (CTL) immune response. We
previously reported that the SARS-CoV-2 N protein can be uploaded at
high levels in EVs upon fusion with Nefmut, i.e., a biologically
inactive HIV-1 Nef mutant incorporating into EVs at quite high levels.
Here, we analyze the immunogenic properties in human cells of EVs
engineered with SARS-CoV-2 N fused at the C-terminus of either Nefmut or
a deletion mutant of Nefmut referred to as NefmutPL. Analysis of in
vitro produced EVs proven the uploading of N protein also when fused
with truncated Nefmut. Mice injected with DNA vectors expressing each
fusion protein developed robust SARS-CoV-2 N-specific CD8+ T cell immune
responses. When ex vivo human dendritic cells were challenged with EVs
engineered with either fusion products, the induction of a robust
N-specific CTL activity, as evaluated by both CD107a and trogocytosis
assays, was observed. Through these data we achieved the
proof-of-principle that engineered EVs can be instrumental to elicit
anti-SARS-CoV-2 CTL immune response in human cells. This achievement
represents a mandatory step towards the upcoming experimentations in
pre-clinical models.