MOLECULAR NEUTRALIZATION STUDIES ON MYOTOXIN II, A LYSINE-49 PHOSPHOLIPASE A2 FROM THE VENOM OF THE SNAKE Bothrops asper.

Mini-Symposium - Abstracts

11 MOLECULAR NEUTRALIZATION STUDIES ON MYOTOXIN II, A LYSINE-49 PHOSPHOLIPASE A2 FROM THE VENOM OF THE SNAKE Bothrops asper.

B. LOMONTE

Clodomiro Picado Institute, School of Microbiology, University of Costa Rica, San José, Costa Rica.

Phospholipases A2 (PLA2) with skeletal muscle-damaging activity are widely distributed among venomous snakes. In the genus Bothrops, there is a family of basic myotoxins sharing a high structural homology, antigenic cross-reactivity and pharmacological properties. Its members seem to fall into two categories: enzymatically-active (Asp-49) PLA2s and enzymatically-inactive (Lys-49) PLA2-like proteins. B. asper myotoxin II and B. jararacussu myotoxin I are two well-characterized proteins of the latter group, which demonstrates that PLA2 activity is not required for the expression of their muscle-damaging activity. B. asper myotoxin II, in addition, is capable of inducing edema and of lysing a variety of cultured cell types.

Neutralization of B. asper myotoxin II has been studied using polyclonal and monoclonal antibodies as well as heparins. Using synthetic peptides of myotoxin II, a heparin-binding region has been identified. The interaction of heparins with this site, including residues 115-129 (with a possible contribution of residues 36 and 38) leads to the neutralization of its myotoxic and cytolytic activities. In contrast to two other peptides of myotoxin II, peptide 115-129 is capable of lysing endothelial cells, albeit with ~10-fold lower efficiency than the toxin. However, no evidence of myonecrosis has been obtained upon injection of this peptide. Molecular dynamics analyses predict that the three-dimensional structure of the free peptide may be similar to its native conformation, according to the crystal structure of myotoxin II. By coupling peptide 115-129 to diphtheria toxoid as a carrier, rabbit antibodies have been raised. These antibodies recognize both the peptide and the toxin, in agreement with this prediction. The neutralizing ability of these site-specific antibodies is currently being investigated.

CORRESPONDENCE TO:

Dr. Bruno Lomonte - Departamento de Imunologia, Facultad de Microbiologia, Universidad de Costa Rica, San Jose, Costa Rica. email: [e-mail]

Publication Dates

• Publication in this collection
  08 Jan 1999
• Date of issue
  1997