The selected proteins, envelope glycoprotein (Q75008), protease (Q75002), reverse transcriptase (Q75002), and integrase (Q75002), were retrieved from the UniProt database, which is a part of the human immunodeficiency virus type 1 group M subtype C (isolate ETH2220), and are crucial in the infection mechanism (11, 67). Here, ERVW-1 is linked to infection.