Evaluation of the proteolytic activity of type a botulinum neurotoxins from different sources against synaptic target proteins

CABALLERO PA; TRONCOSO M; PAREJA V; FIGUEROA E; FERNÁNDEZ RA; PATTERSON, S.I.; SOSA, MA

San Luis

Congreso; XXXII Reunión Anual de la Sociedad de Biología de Cuyo; 2015

Sociedad de Biología de Cuyo

Botulinum neurotoxin (BoNT) type A, produced by Clostridium botulinum (Cb), is a prevalent serotype in strains from Mendoza soils. Soil (Su) is the main reservoir for Cb, and is possibly one of the infectious sources for infant botulism (IB). The high incidence of IB in breast-fed infants with no history of complementary feeding raises the possibility that soil is an important source of infection. In previous studies we found that cultured strains obtained from Su and from IB cases differ in morphology and also in some BoNTs biological properties. In this study we evaluated the proteolytic activity of the different BoNTs against target proteins. Rat brain homogenates were incubated with BoNT from either Su or IB and compared with that of the A-Hall strain, under controlled conditions. Proteolysis of SNAP-25 was analyzed by Western blot with specific monoclonal antibodies, detected by chemiluminescence. The quantitation of SNAP-25 was normalized to actin levels. We observed that the protein is cleaved into smaller fragments by the Su toxin, but to a greater degree than with the A-Hall. However, the IB toxin showed low activity against this synaptic protein. The differential effect of the toxins is consistent with the higher toxicity of Su compared to other strains. The differences between Su and IB toxins imply a more powerful proteolysis-based toxic activity in the former. Interestingly, they could also indicate that the bacterium is highly modified during transit through the infant digestive tract.