Thiolated Recombinant Human Tumor Necrosis Factor-Alpha Protects against Plasmodium berghei K173-Induced Experimental Cerebral Malaria in Mice

The introduction of reactive thiol groups in recombinant human tumor necrosis factor (TNF) alpha (rhTNF-α) by the reagent succinimidyl-S-acetylthioacetate resulted in the formation of a chemically stabilized rhTNF-α trimer (rhTNFα-AT; as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis). rhTNFα-AT showed a substantially enhanced protective efficacy against the development of experimental murine cerebral malaria (ECM) after intravenous injection compared to the protective efficacy of nonmodified rhTNF-α. Administration of thiolated rhTNF-α with protected thiol groups (rhTNFα-ATA; no stabilized trimers in vitro) exhibited the same protective efficacy against ECM, while in vitro bioactivity was reduced. Parasitemia was significantly suppressed in rhTNF-treated mice that were protected against ECM but not in treated mice that developed ECM. Protection against ECM was not related to increased concentrations in plasma of soluble TNF receptor 1 and 2 directly after injection or at the moment of development of ECM in nontreated mice. The results indicate that thiolation of rhTNF-α leads to the formation of stable trimers with increased potential in vivo.