Relevance of the diversity among members of the Trypanosoma cruzi trans-sialidase family analyzed with camelids single-domain antibodies.

RATIER L (1RA AUTORIA COMPARTIDA); URRUTIA M (1RA AUTORIA COMPARTIDA); PARIS G; ZAREBSKI L; FRASCH AC; GOLDBAUM FA

Plos ONE

Public Library of Science

Lugar: San Francisco, United State; Año: 2008 vol. 3 p. 1 - 11

1932-6203

The sialic acid present in the protective surface mucin coat of Trypanosoma cruzi is added by a membrane anchored transsialidase (TcTS), a modified sialidase that is expressed from a large gene family. In this work, we analyzed single domaincamelid antibodies produced against trans-sialidase. Llamas were immunized with a recombinant trans-sialidase andinhibitory single-domain antibody fragments were obtained by phage display selection, taking advantage of a screeningstrategy using an inhibition test instead of the classic binding assay. Four single domain antibodies displaying strong transsialidase inhibition activity against the recombinant enzyme were identified. They share the same complementaritydetermining region 3 length (17 residues) and have very similar sequences. This result indicates that they likely derived froma unique clone. Probably there is only one structural solution for tight binding inhibitory antibodies against the TcTS usedfor immunization. To our surprise, this single domain antibody that inhibits the recombinant TcTS, failed to inhibit theenzymatic activity present in parasite extracts. Analysis of individual recombinant trans-sialidases showed that enzymesexpressed from different genes were inhibited to different extents (from 8 to 98%) by the llama antibodies. Amino acidchanges at key positions are likely to be responsible for the differences in inhibition found among the recombinantenzymes. These results suggest that the presence of a large and diverse trans-sialidase family might be required to preventthe inhibitory response against this essential enzyme and might thus constitute a novel strategy of T. cruzi to evade the hostimmune system.