Antigenic variation in Giardia muris: New tools for the development of a vaccine against the human parasite Giardia lamblia.

RÓPOLO ANDREA S, ALICIA SAURA, PEDRO G CARRANZA, LUCAS E CAVALLIN AND HUGO D LUJAN.

Villa Carlos Paz

Congreso; XXXVIII Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2002

Giardia lamblia is a protozoan parasite of human that causes intestinal disease worldwide. G lamblia undergoes antigenic variation, a phenomenon that allows the parasite to evade the host?s immune response by changing its variant-specific surface proteins (VSP). Little is known about the immunophatology of giadiasis because there is no animal model of the disease. G. lamblia does not infect mice which are infected by Giardia muris. The biology of G. muris is mostly unknown due to the difficulty to culture it in vitro and the low efficiency to obtain viable trophozoites from infected animals. We have improved the isolation method as well as the culture medium, which allowed to isolate nucleic acid to study antigenic variation in G muris. The use of moderately degenerate primers designed from known G lamblia VSP genes allowed us to amplify by PCR50 products from G muris DNA which were isolated, cloned and sequenced, showing high homology with G. lamblia VSPs. Moreover, RT-PCR and Northern blot analysis indicated that VSP transcripts are present in G. muris? trophozoites. At the protein level G muris VSP exhibit the characteristics of VSPs from G lamblia, such as the conserved transmembrane domain and the cytosolic carboxy-terminal region. These results demonstrate for the first time that G. muris also undergo antigenic variation. This fact, together with the discovery in our laboratory on the molecular mechanism controlling antigenic variation in G lamblia, opens new ways for the development of a vaccine against Giardia.