CD4 and infection: Siglec-1 is the most recent lectin receptor implicated in HIV uptake and trans-infection, with the mechanism of the capture, internalisation and retention of exogenous virus in ‘vesicular caves’ seen on MNPs70–73 described before this interferon-inducible receptor was implicated.72,74–77 The formation of these caves sequesters the virus from the external environment, protecting it from neutralising antibodies and cellular immune responses, before it can be transferred to CD4 T cells.