HLA class I histocompatibility antigen, HLA-A (HLAA), of 365 aas and 1 C-terminal TMS (Saunders and van Endert 2011). It acts with beta-2 (β-2) microglobulin B2M (P61769). There are many HLA antigens (HLAA, B, C, E, F and G, all homologous to each other and of 338 to 366 aas in length with a C-terminal TMS. Tapasin (TAPA, TABBP, NGS17 of 448 aas) is a necessary accessory protein for proper presentation of peptide antigens (Sadegh-Nasseri et al. 2008). A charged amino acyl residue in the transmembrane/cytoplasmic region of tapasin influences MHC class I assembly and maturation (Petersen et al. 2005). The human specific poxvirus molluscum contagiosum virus (MCV) has developed robust immune evasion strategies (Harvey et al. 2019). MCV-encoded MC80 can disrupt MHC-I antigen presentation in human and mouse cells. MC80 shares moderate sequence-similarity with MHC-I, and it associates with components of the peptide-loading complex. Expression of MC80 results in ER-retention of host MHC-I and thereby reduced cell surface presentation. MC80 accomplishes this by engaging tapasin via its luminal domain, targeting it for ubiquitination and ER-associated degradation in a process dependent on the MC80 transmembrane region and cytoplasmic tail. Tapasin degradation is accompanied by a loss of TAP, which limits MHC-I access to cytosolic peptides (Harvey et al. 2019).