HLA-DRB1 and giardiasis: First, four MHC class II alleles were chosen, the MHC class II I-Ak and I-Ad that are expressed in mice widely used as model for giardiasis, as well as the HLA-DRB1 * 03: 01 and HLA-DRB1 * 13: 01 alleles that are related to an increased risk of G. lamblia infection (AL-Khaliq et al., 2020; El-Beshbishi et al., 2020).