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. The dominant HIV subtype in the Americas, Western Europe and Australasia is subtype B. As a result, the great majority of HIV clinical research has been conducted in populations where subtype B predominates.
In contrast, there is less research available for subtype C, although just under half of all people living with HIV have subtype C. Subtype C is the dominant form in Southern Africa, Eastern Africa, India, Nepal, and parts of China
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. | 
