Innovative immunization protocols using chimeric recombinant protein for the production of polyspecific loxoscelic antivenom in horses.

This research investigates the development of an antivenom for treatment of spider bites from the Loxosceles species using an innovative immunization protocol in horses. The study showed that using a chimeric recombinant protein combined with initial doses of venoms can produce antibodies similar to traditional antivenom, but with less usage of crude venom.

Chimeric Protein Development

• The researchers created a chimeric protein, known as rCpLi, which exhibits three epitopes (parts of an antigen recognised by the immune system) of rLiD1, a dermonecrotic toxin from the venom of Loxosceles intermedia spider.
• This rCpLi protein was used as the basis for the experimental immunization protocol conducted on horses.

A New Immunization Protocol

• The team experimented with different immunization protocols on horses, including immunization with rCpLi alone and a combination of rCpLi and initial doses of venom.
• The outputs of these new protocols were then compared with the traditional method of antivenom production using crude Loxosceles gaucho, Loxosceles laeta, and L. intermedia venoms as antigens.

Efficacy of the New Protocol

• The researchers found that horses immunized with three initial doses of crude venom containing a mixture of L. intermedia, L. gaucho and L. laeta, followed by nine doses of rCpLi, were able to generate antibodies with the same reactivity as those produced through the traditional method.
• Results from in vivo and in vitro neutralization tests showed that the antivenoms produced using the new immunization procedures can neutralize the dermonecrotic activity of Loxosceles venoms.

Potential Implications

• Some of the sera produced in this study met the potency requirements necessary for potential therapeutic use in humans, indicating this could provide a robust approach for developing antivenoms in the future.
• An additional advantage of the new protocol is that it used about 67% less crude venom than the traditional method. This reduction could lessen the negative impact on the spider population, as fewer spiders would be needed to produce the venom.