Innate and adaptive immune responses to the injection of hybrid camouflaging erythrocyte Saccharolobus solfataticus-phosphotriesterase mutant-loaded nanoreactors to mice.

Prophylactic and post-exposure administration of phosphotriesterase-containing polymersome nanoreactors to mice challenged with paraoxon has proven to be very effective against poisoning by this organophosphate compound. The enzyme was an evolved mutant of Saccharolobus solfataricus phosphotriesterase (PTE), a hyperthermophilic archaea enzyme. The enzyme-polymersome nanoreactors (PTE-nRs) were camouflaged into mouse erythrocyte ghosts. We observed that 24 h and 7 days after the injection of PTE and PTE-nRs into the tail vein of mice induced a slight decrease of recruited immune cells in the peritonium upon zymosan injection and in PMA-induced reactive oxygen production. There was no detectable accumulation of PEG, a building block component of nanoreactor membrane. As well, ELISA test for the serum cytokine levels (interleukin-1β (IL-1 β), IL-2, IL-4, IL-6, IL-17, IFNγ and TNF-α) did not reveal an increase, besides slight elevation of L-12 under the injection of PTE-nRs. Moreover, injection of empty nanoreactors did not trigger anti-PEG IgG antibody generation. It is allowed resuming that the nanomaterial injections have induced only minor changes in the functioning of the innate immune cells. A tentative explanation for the safety of this enzyme is proposed. The global net electrostatic charge of PTE mutant is low compared to other related enzymes. Thus, it may be stated that the negatively charged surface of the enzyme mitigates immune response. The mild immunological responses to this archaea PTE mutant make this enzyme particularly safe for advanced studies in view of developing nanoreactors, using this enzyme as a catalytic bioscavenger against organophosphate poisoning.