# Human guanylate-binding protein (GBP) 1 inhibits replication of severe acute respiratory syndrome coronavirus 2

## TL;DR

Human GBP1 protein inhibits SARS-CoV-2 replication in lab tests, but this effect was not seen in mice, suggesting it could be a target for new antiviral therapies.

## Contribution

Human GBP1 inhibits SARS-CoV-2 replication via a novel mechanism distinct from other GBPs and in multiple variants.

## Key findings

- Overexpression of human GBP1 inhibits SARS-CoV-2 and its variants in vitro.
- GBP1 does not restrict SARS-CoV-2 through actin remodeling or spike protein processing.
- Mouse GBP cluster did not show antiviral activity in a mouse infection model.

## Abstract

Severe respiratory syndrome coronavirus 2 (SARS-CoV-2) infections are associated with significant morbidity and mortality worldwide. Identification and characterization of intracellular proteins with antiviral activity (known as restriction factors) is a key first step towards the future development of novel host-directed antiviral therapies. In this study, we investigated the antiviral activity of 14 different interferon-stimulated gene (ISG) proteins against SARS-CoV-2. Overexpression of human guanylate binding protein (GBP) 1 resulted in potent inhibition of the ancestral SARS-CoV-2 strain, as well as against Alpha, Beta, Delta, Omicron BA.1, and Omicron BA.2 variants of concern (VOCs). Moreover, knockdown or knockout of endogenous human GBP1 resulted in enhanced titers of SARS-CoV-2. While hGBP1 can restrict some viruses via actin remodeling, our data indicate that this is not the mechanism here. Moreover, we show that unlike GBP2 and GBP5, which impair spike protein processing, GBP1 did not reduce infectivity of spike-pseudotyped viruses following titration on Caco-2 cells. Multiple human GBPs have been reported to inhibit SARS-CoV-2 in vitro; however, we report no significant differences in virus titers recovered from the upper or lower airways of SARS-CoV-2-infected wild-type mice compared to from mice lacking the chromosome 3 cluster of mouse GBPs (GBP1/2/3/5/7). Together, our studies describe the ability of human GBP1 to inhibit SARS-CoV-2 replication, highlighting this host protein as a potential target for the development of host-directed antiviral therapies against this virus.

Viruses like SARS-CoV-2 can cause widespread illness and death. While currently licensed antiviral drugs are critical tools, drug resistance can develop. Our immune system produces intracellular proteins called “restriction factors” that can limit virus replication within cells. These proteins are promising targets for developing new antiviral therapies. In this study, we identified one such protein, human GBP1, which inhibited a range of SARS-CoV-2 variants in vitro, including Delta and Omicron. Interestingly, GBP1 inhibited SARS-CoV-2 through a different mechanism to that of other human GBPs as it did not interfere with prosessing of the viral spike protein. Of interest, a cluster of mouse GBPs, including GBP1, did not demontrate significant antiviral activity in a mouse model of infection. Overall, our findings suggest that human GBP1 could be a valuable target for host-directed antiviral strategies and highlight the limitations of using mouse models to study certain aspects of human innate immunity.