Structural stability of SARS-CoV-2 virus like particles degrades with temperature

Abstract

SARS-CoV-2 is a novel coronavirus which has caused the COVID-19 pandemic. Other known coronaviruses show a strong pattern of seasonality, with the infection cases in humans being more prominent in winter. Although several plausible origins of such seasonal variability have been proposed, its mechanism is unclear. SARS-CoV-2 is transmitted via airborne droplets ejected from the upper respiratory tract of the infected individuals. It has been reported that SARS-CoV-2 can remain infectious for hours on surfaces. As such, the stability of viral particles both in liquid droplets as well as dried on surfaces is essential for infectivity. Here we have used atomic force microscopy to examine the structural stability of individual SARS-CoV-2 virus like particles at different temperatures. We demonstrate that even a mild temperature increase, commensurate with what is common for summer warming, leads to dramatic disruption of viral structural stability, especially when the heat is applied in the dry state. This is consistent with other existing non-mechanistic studies of viral infectivity, provides a single particle perspective on viral seasonality, and strengthens the case for a resurgence of COVID-19 in winter.

Functional Severe Acute Respiratory Syndrome Coronavirus 2 Virus-Like Particles From Insect Cells

“…In this manuscript, we show that SARS-CoV-2 VLPs can be efficiently produced in insect cells, which are generally considered as more robust and cost-effective producer cells than mammalian hosts. Previous studies report expression of SARS-CoV-2 VLPs in 293T and Vero cell lines ( Boson et al, 2020 ; Plescia et al, 2020 ; Swann et al, 2020 ; Xu et al, 2020 ; Sharma et al, 2021 ), and one recent study in insect cells ( Mi et al, 2021 ); however, the authors do not specify the yield. It has to be noted that the glycosylation pattern of proteins expressed in insect cells differs from that of the native form produced in human cells, which is important for viral surface glycoproteins, as they play important roles in virus–host recognition and immune recognition and evasion.…”

“…Recently, production of SARS-CoV-2 originating VLPs has been reported as well. Described particles can be divided into several subtypes, depending on the technology used: homotypic VLPs composed of coronaviral proteins only ( Boson et al, 2020 ; Lu et al, 2020 ; Plescia et al, 2020 ; Swann et al, 2020 ; Xu et al, 2020 ; Kumar et al, 2021 ; Sharma et al, 2021 ); heterotypic (chimeric) VLPs, where the SARS-CoV-2 S protein is incorporated into a heterologous viral scaffold (animal viruses or bacteriophages) ( Fougeroux et al, 2021 ; Roy et al, 2021 ; Tan et al, 2021 ); and heterotypic VLP where no coronaviral proteins are present, but fragments of coronaviral genetic material are encapsulated in either plant viruses or bacteriophages and may be used, for example, for diagnostic purposes ( Chan et al, 2021 ). Some authors also classify pseudoviruses displaying SARS-CoV-2 S protein as VLPs ( Ju et al, 2021 ).…”

The outbreak of COVID-19 in Taiwan in late spring 2021: combinations of specific weather conditions and related factors

“…Despite the diverse results, most studies concluded a negative correlation between temperature and COVID-19 transmission (McClymont & Hu 2021 , Paraskevis et al 2021 ). Laboratory research found that the structural stability of the SARS-CoV-2 virus quickly decreases at warm temperatures (Sharma et al 2021 ). It was believed that the incidence of COVID-19 can drop in the summertime.…”

Evolutionary trajectory of SARS-CoV-2 and emerging variants

“…Furthermore, cold and dry environments can have immunosuppressive effects on a potential host, further increasing the chances of infection [240][241][242]. Evidence suggests decreased transmission of SARS-CoV-2 in warmer climates [243][244][245][246], likely due to degeneration of viral structural stability with increasing temperatures [247]. Decreased transmission of SARS-CoV-2 was not observed during the summer of 2020 [11,248] likely because of the sheer number of cases and an immunologically naïve population.…”