CD4 and infection: This model might not be able to fully recapitulate the activity of mucus-associated proteins, such as mucins, [51] which inhibit HIV via several mechanisms, including, among others: (i) hindering of the viral particle movement [52]; (ii) fusion inhibitory activity [53]; and (iii) inhibition of HIV trans-infection of CD4+T cells by binding to DC-SIGN [54].