La Bacillus anthracis causante de la infección del carbunco, debe su toxicidad a las modificaciones citosólicas que causan sus factores tóxicos: Factor Letal (FL), Factor de Edema (FE) y a la proteína que los transloca al interior de la célula, llamada Protectora de Antígeno (PA). Se seleccionó una clona que codifica fragmentos de anticuerpos vNAR, de la familia IgNAR ( inmunoglobina Nuevo Receptor de Antígeno) del tiburón Heterodontus francisci no inmune y que reconoce a PA y se espera que tenga la capacidad  de neutralizar la actividad de PA en ensayos in vitro y eventualmente pueda fungir tratamiento alterno en la infección del carbunco.The bacteria Bacillus anthracis, the causal agent of anthrax, owes its toxity to the enzymatic activity of Lethal Factor (LF), Edema Factor (EF), and the Protective Antigen (PA) protein whose main activity is to translocate LF and EF into the citosol. We isolated a clone that expresses vNAR antibody fragments, belonging to the IgNAR family (Immunoglobulin New Antigen Receptor) from a non-immunized shark Heterodontus francisci, capable of recognizing PA. The vNAR selection was possible by affinity bioselection assays from a library of M13 bacteriophage expressing the vNAR protein in its surface. The transformation of Escherichia coli TOP10F´ with plasmid pComb3X was also necesary to induce protein expression of soluble vNAR with IPTG. Immunodetection and recognition assays were performed by ELISA. We expect this isolated clone to be able to neutralize PA activity in  in vitro assays and eventually become an alternative treatment for anthrax infections.