Impact of ECTV C15 expression on the early immune response in the popliteal lymph node (scRNA-seq)

Orthopoxviruses, such as variola and Mpox, encode a myriad of immunomodulatory proteins to promote pathogenesis. One notable family is the B22 family of proteins, which are highly conserved surface glycoproteins that potently inhibit T cell activation in vitro and ex vivo. Using the model poxvirus, ectromelia (ECTV), our lab has demonstrated that its B22 protein, C15, is capable of inhibiting both CD4+ and CD8+ T cells both in vitro and ex vivo, similar to other B22 proteins. Furthermore, we have also identified an additional function of C15: antagonism of NK cells during early infection. Specifically, C15 antagonizes the engagement of NK cells with infected cells in the popliteal lymph node during the innate immune response to infection. This inhibition by C15 promotes viral dissemination and replication, such that in the absence of C15, viral replication is significantly stunted. To date, there has not been any work investigating the mechanisms underlying this NK cell inhibition. To broadly explore the cell type-specific changes occurring during this critical window, we performed single cell RNA-seq on popliteal lymph nodes at 24 and 48 hours post-infection.