Looking into mucormycosis coinfections in COVID-19 patients using computational analysis

Mucormycosis infection may develop after using steroids treatment to improve the severely of the symptoms in coronavirus patients. The rising in the infection rate of mucormycosis has been noticed in patients after COVID-19 infection. To understand the high morbidity mucormycosis coinfection, the cell surface Glucose Regulated Protein 78 (CS-GRP78) was docked to the virus ACE2-SARS-CoV-2 RBD to create the ACE2-SARS-CoV-2 RBD-GRP78 complex which facilitates the virus entrance into the cell. The spore coat protein homolog 3 (CotH3) of mucormycosis was modeled and docked to the ACE2-SARS-CoV-2 RBD-GRP78 complex. The binding energies of CotH3 with RBD, ACE2, and GRP78 were calculated. The binding results show that GRP78 substrate-binding domain beta weakly binds to the spike RBD combined with ACE2 of the spike RBD-ACE2 complex. Its main function is to stabilize the binding between RBD and ACE2, while CotH3 has a strong affinity for the SARS-CoV-2 RBD, but not for ACE2 or GRP78. The CotH3 appeared to have the same affinity to RBD in the SARS-CoV-2 lineages with some preference to the lineage B.1.617.2 (Delta variant). The complex design illustrates that the coat protein of the fungi is more likely linked to the spike protein of the SARS-CoV-2 virus, which would explain the increased mortality mucormycosis coinfections in COVID-19 patients.