ERVW-1 and infection: Hence, HIV-1 Env is responsible for virus attachment to target cells, membrane fusion and subsequent genome-bearing capsid entry into the cytoplasm, thereby initiating the productive infection process (Markosyan et al., 2003; Chang et al., 2005; Dobrowsky et al., 2008; Wilen et al., 2012; Melikyan, 2014; Sood et al., 2017; Stultz et al., 2017; Iliopoulou et al., 2018; Chen, 2019).