It is known that CD81 participates, in concert with other tetraspanins, like CD63 and CD9, in many biological processes such as cell adhesion, migration, cell–cell fusion as well as in multiple steps of viral infection, especially in the case of HIV-1 (Ho et al., 2006; Jolly and Sattentau, 2007). The gene discussed is CD9; the disease is viral infectious disease.