Memory cytotoxic SARS-CoV-2 spike protein-specific CD4+ T cells associate with viral control (preprint)

Little is known of the role of cytotoxic CD4+ T-cells in the control of viral replication. Here, we investigate CD4+ T-cell responses to three dominant SARS-CoV-2 epitopes and evaluate antiviral activity, including cytotoxicity and antiviral cytokine production. Diverse T cell receptor (TCR) usage including public TCRs were identified; surprisingly, cytotoxic CD4+ T-cells were found to have signalling and cytotoxic pathways distinct from classical CD8+ T-cells, with increased expression of chemokines and tissue homing receptors promoting migration. We show the presence of cytolytic CD4+ T-cells during primary infection associates with COVID-19 disease severity. Robust immune memory 6-9 months post-infection or vaccination provides CD4+ T-cells with potent antiviral activity. Our data support a model where CD4+ killer cells drive immunopathogenesis during primary infection and CD4+ memory responses are protective during secondary infection. Our study highlights the unique features of cytotoxic CD4+ T-cells that use distinct functional pathways, providing preventative and therapeutic opportunities.

End-to-End Protocol for the Detection of SARS-CoV-2 from Built Environments (preprint)

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes coronavirus disease 2019, is a respiratory virus primarily transmitted from person to person through inhalation of droplets or aerosols, laden with viral particles. However, as some studies have shown, virions can remain infectious for up to 72 hours on surfaces, which can lead to transmission through contact. For this reason, a comprehensive study was conducted to determine the efficiency of protocols to recover SARS-CoV-2 from surfaces in built environments. This end-to-end (E2E) study showed that the effective combination of monitoring SARS-CoV-2 on surfaces include using an Isohelix swab as a collection tool, DNA/RNA Shield as a preservative, an automated system for RNA extraction, and reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) as the detection assay. Using this E2E approach, this study showed that, in some cases, SARS-CoV-2 viral standards were still recovered from surfaces as detected by RT-qPCR for as long as eight days even after bleach treatment. Additionally, debris associated with specific built environment surfaces appeared to negatively impact the recovery of RNA, with Amerstat inhibition as high as 90% when challenged with an inactivated viral control. Overall, it was determined that this E2E protocol required a minimum of 1,000 viral particles per 25 cm2 to successfully detect virus from test surfaces. When this method was employed to evaluate 368 samples collected from various built environmental surfaces, all samples tested negative, indicating that the surfaces were either void of virus or below the detection limit of the assay. ImportanceThe ongoing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (the virus responsible for coronavirus disease 2019; COVID-19) pandemic has led to a global slow down with far reaching financial and social impacts. The SARS-CoV-2 respiratory virus is primarily transmitted from person to person through inhalation of infected droplets or aerosols. However, some studies have shown virions can remain infectious on surfaces for days, and can lead to human infection from contact with infected surfaces. Thus, a comprehensive study was conducted to determine the efficiency of protocols to recover SARS-CoV-2 from surfaces in built environments. This end-to-end study showed that the effective combination of monitoring SARS-CoV-2 on surfaces required a minimum of 1,000 viral particles per 25 cm2 to successfully detect virus from surfaces. This comprehensive study can provide valuable information regarding surface monitoring of various materials as well as the capacity to retain viral RNA and allow for effective disinfection.