, 2005). Amino acids E32, D34, and D91 coordinate with the Mg+2 ion, which is responsible for stabilizing the active site of the molecule; thus, their interaction with antibodies likely interferes with its toxic activity. Similar to our results, Dias-Lopes et al. (2010) identified antigenic and immunogenic properties of a 27-amino acid peptide (25NLGANSIETDVSFDDNANPEYTYHGYP51)

from LiD1; the substitution of some residues for alanine drastically reduced the recognition by neutralizing antibodies. Twelve out of 15 amino acids present in peptide 2 are present in the peptide sequence used by these authors. Interestingly, peptide 3 was the best predictor of high neutralizing antivenom because it was only recognized by high neutralizing LDN-193189 potency PCI-32765 sera. Peptide 3 is derived from a toxin of L. laeta venom, which is considered the most immunogenic and with the highest dermonecrotic potential compared to venoms from other species. In addition, L. laeta antivenom is more efficient in neutralizing the dermonecrotic effects of L. intermedia, L. gaucho, and L. laeta venoms. L. intermedia venom is sometimes considered to induce higher lethality than L. laeta venom but all these points are controversial. Therefore, SALOX antiserum from CPPI is still prepared after immunization

of horses using a mixt of three differents venoms ( de Oliveira et al., 2005). The use of peptide 3 in ELISA

appears to be promising for screening horse sera after completion of an immunization scheme. The lack of recognition of this epitope would suggest that the serum tested is not able to effectively neutralize the in vivo effects of dermonecrotic toxins. In this case, a new immunization scheme can be resumed Afatinib in vivo to improve the neutralizing efficiency of the serum. This study has allowed the identification of new antigenic regions that until now have not been described as being important in the induction of neutralizing antibodies, in particular for a L. laeta toxin. Our results also showed for the first time that the use of peptides that mimic these regions in an in vitro screening assay is able to roughly correlate the neutralizing potency of horse hyperimmune sera produced against Loxosceles sp. venom with antibody titer. We would like to thank Dr. Claude Granier for comments on this manuscript. The skillful scientific assistance of Msc. Luiz Felipe Minozzo Figueiredo is acknowledged. This research was supported by Fundação Araucária. “
“Bioprospecting of secondary metabolites can be an important contribution to economic growth in developing countries. Thousands of new compounds can arise from prospecting programs and indicate new bioactive and/or prototypes for pharmaceutical development.