Immunodominant proteins α-1 giardin and β-giardin are expressed in both assemblages A and B of Giardia lamblia.
BACKGROUND
To date, eight assemblages of Giardia lamblia have been described, but only assemblages A and B are known to infect humans. Despite the fact that the genomic, biological, and clinical differences found between these two assemblages has raised the possibility that they may be considered different species, there is relatively limited information on their phenotypic differences. In the present study, we developed monoclonal antibodies against alpha-1 and beta giardin, two immunodominant proteins produced during G. lamblia infection, and studied their expression and localization in WB (assemblage A) and GS trophozoites (assemblage B).


RESULTS
The polyclonal antibodies generated against WB trophozoites, particularly those recognizing intracellular proteins as well as the proteins present at the plasma membrane (variable-specific surface proteins), showed cross-reactivity with intracellular proteins in GS trophozoites. The use of monoclonal antibodies against beta giardin indicated ventral disc localization, particularly at the periphery in WB trophozoites. Interestingly, although beta giardin was also restricted to the ventral disc in GS trophozoites, the pattern of localization clearly differed in this assemblage. On the other hand, monoclonal antibodies against alpha-1 giardin showed plasma membrane localization in both assemblages with the bare area of GS trophozoites also being distinguished. Moreover, the same localization at the plasma membrane was observed in Portland-1 (Assemblage A) and in P15 (Assemblage E) trophozoites.


CONCLUSIONS
We found differences in localization of the beta giardin protein between assemblages A and B, but the same pattern of localization of alpha-1 giardin in strains from Assemblages A, B and E. These findings reinforce the need for more studies based on phenotypic characteristics in order to disclose how far one assemblage is from the other.
Laboratorio de Microbiología e Inmunología, Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET, Friuli 2434, (5000) Córdoba, Argentina.
Constanza
C
Feliziani
María C
MC
Merino
María R
MR
Rivero
Ulf
U
Hellman
María C
MC
Pistoresi-Palencia
Andrea S
AS
Rópolo
D000595:Amino Acid Sequence; D000818:Animals; D002462:Cell Membrane; D003598:Cytoskeletal Proteins / Q000737:chemistry / Q000235:genetics* / Q000276:immunology; D005260:Female; D005786:Gene Expression Regulation; D016829:Giardia lamblia / Q000145:classification / Q000235:genetics* / Q000254:growth & development / Q000276:immunology; D005873:Giardiasis / Q000469:parasitology*; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D021381:Protein Transport; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics* / Q000276:immunology; D016415:Sequence Alignment; D053058:Trophozoites / Q000737:chemistry / Q000254:growth & development / Q000378:metabolism
D003598:Cytoskeletal Proteins; D015800:Protozoan Proteins; C038207:giardin protein, Giardia lamblia