CDCA7L and viral infectious disease: Consistent with the reports that unlike the HR2 (or CHR) peptides, the HR1 (or NHR) peptides derived from the enveloped viruses with class I membrane fusion proteins (e.g., HIV-1, SARS-CoV, and MERS-CoV) have no or low activity to inhibit 6-HB formation, cell–cell fusion, and viral infection, mainly because these HR1 peptides tend to aggregate in physiological solutions [14,15,43,44,45], we found that MERS-HR1P and HKU4-HR1P also exhibited no fusion inhibitory activity, possibly for the same reason described above.