Open AccessA Recombinant Fragment of Human Surfactant Protein D Binds Spike Protein and Inhibits Infectivity and Replication of SARS-CoV-2 in Clinical Samples
Author(s) -
Taruna Madan,
Barnali Biswas,
Praveen M. Varghese,
Rambhadur Subedi,
Hrishikesh Pandit,
Susan IdiculaThomas,
Indra Kundu,
Sheetalnath Rooge,
Reshu Agarwal,
Dinesh Mani Tripathi,
Savneet Kaur,
Ekta Gupta,
Sanjeev K. Gupta,
Uday Kishore
Publication year - 2021
Publication title -
american journal of respiratory cell and molecular biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.469
H-Index - 161
eISSN - 1535-4989
pISSN - 1044-1549
DOI - 10.1165/rcmb.2021-0005oc
Subject(s) - infectivity , vero cell , recombinant dna , virology , coronavirus , viral replication , biology , in silico , virus , microbiology and biotechnology , gene , covid-19 , medicine , infectious disease (medical specialty) , biochemistry , disease , pathology
Coronavirus disease (COVID-19) is an acute infectious disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Human SP-D (surfactant protein D) is known to interact with the spike protein of SARS-CoV, but its immune surveillance against SARS-CoV-2 is not known. The current study aimed to examine the potential of a recombinant fragment of human SP-D (rfhSP-D) as an inhibitor of replication and infection of SARS-CoV-2. The interaction of rfhSP-D with the spike protein of SARS-CoV-2 and human ACE-2 (angiotensin-converting enzyme 2) receptor was predicted via docking analysis. The inhibition of interaction between the spike protein and ACE-2 by rfhSP-D was confirmed using direct and indirect ELISA. The effect of rfhSP-D on replication and infectivity of SARS-CoV-2 from clinical samples was assessed by measuring the expression of RdRp gene of the virus using quantitative PCR. In silico interaction studies indicated that three amino acid residues in the receptor-binding domain of spike protein of SARS-CoV-2 were commonly involved in interacting with rfhSP-D and ACE-2. Studies using clinical samples of SARS-CoV-2-positive cases (asymptomatic, n = 7; symptomatic, n = 8) and negative control samples ( n = 15) demonstrated that treatment with 1.67 μM rfhSP-D inhibited viral replication by ∼5.5-fold and was more efficient than remdesivir (100 μM) in Vero cells. An approximately two-fold reduction in viral infectivity was also observed after treatment with 1.67 μM rfhSP-D. These results conclusively demonstrate that the rfhSP-D mediated calcium independent interaction between the receptor-binding domain of the S1 subunit of the SARS-CoV-2 spike protein and human ACE-2, its host cell receptor, and significantly reduced SARS-CoV-2 infection and replication in vitro .