Functional characterization of black widow spider neurotoxins synthesised in insect cells.

alpha-latrotoxin, alpha-latroinsectotoxin and the low-molecular-mass protein from black widow spider venom were synthesised in insect cells using the baculovirus expression system. SDS/PAGE analysis of recombinant-virus-infected cells revealed novel proteins that migrated with sizes similar to those of the neurotoxins from spider venom. The identities of these proteins as alpha-latrotoxin, alpha-latroinsectotoxin or the low-molecular-mass protein were confirmed by immunoblot analysis of infected cells with anti-(alpha-latrotoxin), anti-(alpha-latroinsectotoxin) or anti-(low-molecular-mass protein) IgG. Neither the low-molecular-mass protein nor alpha-latrotoxin were toxic upon injection into Trichoplusia ni larvae or upon virus-derived synthesis directly in the cytoplasm of the target tissue. Analysis of the biological activity of the recombinant virus encoding alpha-latroinsectotoxin, however, revealed a strong toxic effect on the T. ni larvae. These data indicate that the toxic effect of the native insectotoxin may be promoted by the alpha-latroinsectotoxin subunit alone and provides evidence that the mechanism of action of alpha-latroinsectotoxin may be mediated by internalisation of part of the neurotoxin alpha-subunit molecule.

Suppression of the chloroquine resistance of Plasmodium berghei by treatment of infected mice with a microsomal monooxygenase inhibitor.

Administration of a combination of chloroquine and the copper-lysine complex, copper(lysine)(2), an inhibitor of microsomal monooxygenases, considerably decreased the parasitaemia level of mice infected with a chloroquine-resistant strain of Plasmodium berghei. When given separately, chloroquine and the complex had no antimalarial effect. Use of a combination of monooxygenase inhibitors and chloroquine therefore appears to be a promising addendum to the chemotherapy of malaria caused by chloroquine-resistant parasites.