Panoply™ Human FCGRT Over-expressing Stable Cell Line

Human astrovirus (HAstV) is a major cause of gastroenteritis, particularly in children, for which no vaccine or antiviral drug is currently available. Little is known about the host factors required for HAstV entry. Here, researchers used complementary CRISPR-Cas9-based knockout and activation screens to identify the neonatal Fc receptor (FcRn) and dipeptidyl peptidase IV (DPP4) as entry factors for HAstV infection in vitro. Disruption of FcRn or DPP4 reduced HAstV infection in permissive cells. Conversely, overexpression of these factors in non-permissive cells was sufficient to promote infection. The researchers observed direct binding of FcRn, while DPP4 did not, to HAstV virions and purified spike protein. This suggests that FcRn is a receptor for HAstV and DPP4 is a cofactor for cellular entry. Currently clinically used DPP4 and FcRn inhibitors prevented HAstV infection in cell lines and the human enteroids. These findings reveal the invasion mechanism of HAstV and available drug targets for limiting HAstV infection.

Here, the researchers treated Caco2 cells with one of these antibodies, nipocalimab, and found that this treatment blocked HAstV1 infection (Figure 1a). Nipocalimab also blocked HAstV infection in FCGRT-overexpressing HEK293T cells (Figure 1b). Gliptins, a class of oral medications widely used to treat type 2 diabetes, specifically inhibit DPP4 enzymatic activity and bind to the glucagon-like peptide interaction site. To assess whether DPP4 enzymatic activity is required for HAstV entry, the researchers administered sitagliptin, vildagliptin, or teneligliptin to Caco2 cells prior to HAstV infection. They found that, while teneligliptin and vildagliptin were less effective, sitagliptin effectively blocked infection of Caco2 cells with both HAstV1 and HAstV8 (Figure 1c). Similarly, DPP4 overexpressing HEK293T cells were sensitive to sitagliptin treatment (Figure 1d). Surprisingly, blocking DPP4 in FCGRT overexpressing HEK293T cells did not reduce HAstV1 infection, whereas blocking FcRn in DPP4 overexpressing HEK293T cells limited HAstV1 infection (Figure 1e, f) without altering DPP4 or FcRn receptor expression. Similarly, blocking FcRn in DPP4-deficient Caco2 cells abolished residual HAstV1 infection (from approximately 20% to <2%) (Figure 1g). These data suggest that the effects of FcRn are downstream of and independent of DPP4.

Figure 1. FcRn and DPP4 inhibitors are antiviral against HAstV. (Ingle H, et al., 2024)