Giardia lamblia (syn. Giardia duodenalis,
Giardia intestinalis) infections are associated with continuous antigenic variation of the parasite which is mediated by the parasite's major
surface antigen, named variant
surface protein. Offspring mice and corresponding mothers were infected with G. lamblia clone GS/M-83-H7 (expressing
variant surface protein H7) and various parameters of this
infection were assessed in a long-term follow-up investigation. Our experimentation revealed that variant
surface protein H7-type trophozoites were replaced by new variant-type trophozoites during the early stage of
infection (around day 8 p.i.), but the original variant-type re-emerged at at least two time-points during the later stages of
infection (at days 22 and 42 p.i.). Such periods of variant
surface protein H7-type trophozoite re-expansion were accompanied by transient production of intestinal
IgA against variant-specific
epitopes on a 314-aa N-terminal region of
variant surface protein H7. At late stages of
infection (between days 42 and 200 p.i.), most mice produced intestinal
IgA against both
variant surface protein H7 and other
antigens of the parasite. At these stages,
infection seemed to be resolved in most mice, but occasional reappearance of relatively high (at day 64 p.i.) or at least detectable (at days 80 and 120 p.i.) amounts of intestinal parasites indicated that G. lamblia GS/M-83-H7
infections in mice may enter into a latent chronic phase which is interrupted by sporadic breakthroughs of parasite growth.