Middle East Respiratory Syndrome Coronavirus Gene 5 Modulates Pathogenesis in Mice

• Published in: Journal of virology 2021-01, Vol.95 (3)
• Main Authors: Gutierrez-Alvarez, Javier, Wang, Li, Fernandez-Delgado, Raul, Li, Kun, McCray, Jr, Paul B, Perlman, Stanley, Sola, Isabel, Zuñiga, Sonia, Enjuanes, Luis
• Format: Article
• Language: English
• Subjects: Animals; Cell Line; Coronavirus Infections - immunology; Coronavirus Infections - pathology; Coronavirus Infections - virology; Cytokines - metabolism; Dipeptidyl Peptidase 4 - genetics; Disease Models, Animal; DNA, Complementary - genetics; Genome, Viral - genetics; Humans; Immunity, Innate; Lung - immunology; Lung - pathology; Lung - virology; Mice; Mice, Transgenic; Middle East Respiratory Syndrome Coronavirus - genetics; Middle East Respiratory Syndrome Coronavirus - pathogenicity; Mutation; Pathogenesis and Immunity; Viral Load; Viral Nonstructural Proteins - genetics; Viral Nonstructural Proteins - metabolism; Virulence - genetics
• ISSN: 0022-538X; 1098-5514
• DOI: 10.1128/JVI.01172-20

Middle East respiratory syndrome coronavirus (MERS-CoV) causes a highly lethal pneumonia that emerged in 2012. There is limited information on MERS-CoV pathogenesis, as data from patients are scarce and the generation of animal models reproducing MERS clinical manifestations has been challenging. Human dipeptidyl peptidase 4 knock-in (hDPP4-KI) mice and a mouse-adapted MERS-CoV strain (MERS -6-1-2) were recently described. hDPP4-KI mice infected with MERS -6-1-2 show pathological signs of respiratory disease, high viral titers in the lung, and death. In this work, a mouse-adapted MERS-CoV infectious cDNA was engineered by introducing nonsynonymous mutations contained in the MERS -6-1-2 genome into a MERS-CoV infectious cDNA, leading to a recombinant mouse-adapted virus (rMERS-MA) that was virulent in hDDP4-KI mice. MERS-CoV adaptation to cell culture or mouse lungs led to mutations and deletions in genus-specific gene 5 that prevented full-length protein expression. In contrast, analysis of 476 MERS-CoV field isolates showed that gene 5 is highly stable in both humans and camels. To study the role of protein 5, two additional viruses were engineered expressing a full-length gene 5 (rMERS-MA-5FL) or containing a complete gene 5 deletion (rMERS-MA-Δ5). rMERS-MA-5FL virus was unstable, as deletions appeared during passage in different tissue culture cells, highlighting MERS-CoV instability. The virulence of rMERS-MA-Δ5 was analyzed in a sublethal hDPP4-KI mouse model. Unexpectedly, all mice died after infection with rMERS-MA-Δ5, in contrast to those infected with the parental virus, which contains a 17-nucleotide (nt) deletion and a stop codon in protein 5 at position 108. Expression of interferon and proinflammatory cytokines was delayed and dysregulated in the lungs of rMERS-MA-Δ5-infected mice. Overall, these data indicated that the rMERS-MA-Δ5 virus was more virulent than the parental one and suggest that the residual gene 5 sequence present in the mouse-adapted parental virus had a function in ameliorating severe MERS-CoV pathogenesis. Middle East respiratory syndrome coronavirus (MERS-CoV) is a zoonotic virus causing human infections with high mortality rate (∼35%). Animal models together with reverse-genetics systems are essential to understand MERS-CoV pathogenesis. We developed a reverse-genetics system for a mouse-adapted MERS-CoV that reproduces the virus behavior observed in humans. This system is highly useful to investigate the role of specific