Current antiviral treatments often target specific viral components, which can lead to the rapid emergence of drug-resistant mutants. Targeting host signaling pathways, including their associated cellular factors, that are important for virus replication is a novel approach toward the development of next-generation antivirals to overcome drug resistance. Various cellular receptor tyrosine kinases (RTKs) have previously been shown to play important roles in mediating viral replication including coronaviruses. In this study, we examined the roles of RTKs in SARS-CoV-2 replication in two cell lines, A549-ACE2 (human lung epithelial cells) and Vero-E6 (African Green Monkey kidney cell), via chemical inhibitors. We showed that the HER2 inhibitor Lapatinib significantly reduced viral replication in both cell lines, the TrkA inhibitor GW441756 was effective only in A549-ACE2 cells, while the EGFR inhibitor Gefitinib had little effect in either cell line. Lapatinib and GW441756 exhibited a high therapeutic index (CC₅₀/EC₅₀ > 10) in A549-ACE2 cells. Time-of-addition experiments indicated that Lapatinib may inhibit the early entry step, whereas GW441756 can affect post-entry steps of the viral life cycle. These findings suggest the important roles of HER2 and TrkA signaling in SARS-CoV-2 infection in human lung epithelial cells and support further investigation of RTK inhibitors as potential COVID-19 treatments.

Background: Live viral vector-based vaccines are known to elicit strong immune responses, but their use can be limited by anti-vector immunity. Here, we analyzed the immunological responses of a live-attenuated recombinant Pichinde virus (PICV) vector platform (rP18tri). Methods: To evaluate anti-PICV immunity in the development of vaccine antigen-specific immune responses, we generated a rP18tri-based vaccine expressing the lymphocytic choriomeningitis virus (LCMV) nucleoprotein (NP) and administered four doses of this rP18tri-NPLCMV vaccine to mice. Using MHC-I tetramers to detect PICV NP38-45 and LCMV NP396-404 epitope-specific CD8+ T cells, we monitored vector- and vaccine-antigen-specific immune responses after each vaccination dose. Results: LCMV NP396-404-specific effector and memory CD8+ T cells were detected after the first dose and peaked after the second dose, whereas PICV NP38-45-specific memory CD8+ T cells increased with each dose. PICV-binding IgG antibodies peaked after the second dose, while anti-PICV neutralizing antibodies (NAbs) remained low even after the fourth dose. Immunization with the rP18tri-NPLCMV vaccine significantly reduced LCMV viral titers in a chronic LCMV Clone 13 infection model, demonstrating the protective role of LCMV NP-specific T cells. Conclusion: These findings provide important insights into the antigen- and vector-specific immunity of the rP18tri-NPLCMV vaccine and support the development of NP-based vaccines against arenavirus pathogens.