Cross-reactions between Hymenoptera and reptiles
Anaphylaxis to snake venoms is rare but has been described after
recurrent exposure through snake bites or inhalation of dried venom in
9-10% of snake handlers.160,161 Even regular skin
contact with snake venom without a bite can lead to
anaphylaxis.162 It appears that anaphylaxis to snake
venoms is IgE-mediated. However, it has also been shown that snake
envenoming is characterized by significant complement activation and
release of inflammatory mediators leading to non-allergic anaphylaxis
(formerly called anaphylactoid reactions).163
Snake venoms are a complex mix of enzymatic and non-enzymatic proteins
and peptides. Potential candidates for cross-reactivity are PLA2,
hyaluronidase164, and dipeptidyl peptidase
IV.165 Snake PLA2s belong to class I or II PLA2s
sharing less than 19% SI with bee PLA2 (class III), indicating that
there is no relevant cross-reactivity. Higher identities
(>40%) are seen with the class III PLA2 fromHeloderma (Gila monster).
Hyaluronidases and dipeptidyl peptidases of bees and wasps share about
30% of their sequence with snake homologs (Table E1; sequences of
proteins were searched in the Uniprot knowledgebase166and compared with Clustal Omega167). In this light,
clinically relevant cross-reactivity to snake proteins appears to be
highly unlikely. Consequently, no case report of insect venom allergic
patients who also reacted to snake venom has been published so far.