The strains of HIV-1 can be classified into four groups. The most important group, M(main), is the ‘major’ group and is responsible for the majority of the global HIV epidemic.
Subtype A is common in West Africa.
Gp41, known as glycoprotein 41, is a subunit of the envelope protein complex of retroviruses which includes human immunodefiiciency (HIV).
Gp41 is transmembrane protein that contains several sites within its ectodomain that are required for infection of host cells.
Due to its importance in host cell infection, it has also gained much attention as a potential target for HIV serological test for diagnosis. | 
