In the present study, IgG antibody response was found positive in all 11 (100%) HIV seropositive Cryptosporidium positive (Gp I) and 10 (100%) HIV seronegative Cryptosporidium positive (Gp III) including 4 (100%) post-transplant (Gp IIIa) patients while in the Cryptosporidium negative groups (Gp II, IV and V), 3 (12%) patients with other parasitic infections showed positive response. This evidence concerns the gene GPI and parasitic infectious disease.