Heterophilic antibodies in sera from individuals without loxoscelism cross-react with phospholipase D from the venom of and spiders.

Background: Loxoscelism is a severe human envenomation caused by spider venom. To the best of our knowledge, no study has evaluated the presence of antibodies against venom in loxoscelism patients without treatment with antivenom immunotherapy. We perform a comparative analysis for the presence of antibodies capable of recognizing venom in a group of patients diagnosed with loxoscelism and in a group of people without loxoscelism.

Methods: The detection of venom, venom and recombinant phospholipases D from (PLDs) in sera from people with loxoscelism (Group 1) and from healthy people with no history of loxoscelism (Group 2) was evaluated using immuno-dot blot, indirect ELISA, and Western blot.

Results: We found naturally heterophilic antibodies (IgG-type) in people without contact with spiders or any clinical history of loxoscelism. Either serum pools or single sera from Group 1 and Group 2 analyzed by dot blot tested positive for venom. Indirect ELISA for venom recognition showed titles of 1:320 for Group 1 sera and 1:160 for Group 2 sera. Total IgG quantification showed no difference in sera from both groups. Pooled sera and purified IgG from sera of both groups revealed venom proteins between 25 and 32 kDa and the recombinant phospholipase D isoform 1 (rLlPLD1), specifically. Moreover, heterophile antibodies cross-react with PLDs from other species and the venom of spider.

Conclusions: People without contact with the spider venom produced heterophilic antibodies capable of generating a cross-reaction against the venom of and spiders. Their presence and possible interference should be considered in the development of immunoassays for venom detection.