Human cytomegalovirus (HCMV) is a linear double-stranded DNA β-herpesvirus controlled by a vigorous immune response so that infections are asymptomatic or symptoms are mild. If the immune system is compromised, HCMV can replicate to high levels and cause serious end organ disease [1]. On the other side, the immune receptors are in constant arm race with the viral proteins that specifically target them thus manipulate a wide range of immune responses. Therefore, accurately predicting their molecular interactions will be necessary for the development of safe and effective therapeutics to enhance immune responses and vaccination.
HCMV within its unique long (UL)/b’ locus, encodes the key immunomodulatory proteins [2], such as UL144 which is highly orthologous to tumour necrosis factor receptor HVEM (TNFR/SF14, herpesvirus entry mediator) thus resembling some of its promiscuity on the cell surface. HVEM binds the TNF ligands, LIGHT and LTa; the immunoglobulin inhibitory receptor, B and T lymphocyte attenuator (BTLA); and the natural killer cell–activating receptor CD160. However, the initial studies shown that UL144 selectively binds only BTLA [3], while avoiding activation of inflammatory signalling initiated by CD160 in natural killer (NK) cells. This molecular network is quite well described, however, the engagement of CD160 by UL144 has not yet been satisfactorily studied. One study reports the viral glycoprotein UL144 from rhesus CMV can bind human and rhesus CD160 with low affinity [4]. This interaction likely represents a divergence between viral species as primate BTLA and CD160 are highly homologous. Moreover, wild-type (wt) UL144 maintains many glycosylation sites which are not present in other viral species thus suggest a direct involvement of N-glycans in receptor recognition on immune cell. Here, we focused on the characterization of CD160 binding to viral UL144, whose mutual engagement could lead to disrupted signalling under various glycosylation condition. We accessed the binding by co-immunoprecipitation assay (co-PI) using recombinant his-tagged proteins (dgUL144, rhUL144-wt, UL144-wt, UL144-N91) and CD160 fused to Fc. We observed binding between all UL144-glycosylation deficient variants to CD160. Moreover, considering that the ectodomain of UL144 is highly polymorphic across primate CMV we examined both human and rhesus CMV UL144 selectivity for its cellular receptor thus the binding of rhesus CMV UL144 to human CD160 was also observed. However, to fully understand the molecular basis of these interactions, further analyses have to be performed.
This research was funded by the contribution of the Slovak Research and Development Agency under the project APVV-19-0376 and the contribution of the Scientific Grant Agency of the Slovak Republic under the grant VEGA-02/0026/22. IN was Marie Curie Fellow financed by program SASPRO co-funded by the European Union and the Slovak Academy of Sciences. Part of the research team was supported by the Interreg V-A SK-AT cooperation program by project CAPSID under the contract No. NFP305010V235 co-financed by the European Regional Development Fund.