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24 Apr 2020

Serological Assays For SARS-CoV-2

Chris Mok and Tomas Lv published with Malik Peiris, Co-Director at HKU-Pasteur, and Leo Poon, School of Public Health (HKU), in Eurosureveillance on serological assays for SARS-CoV-2

>>> Serological assays for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), March 2020

The true severity of COVID-19 remains a major knowledge gap because mild or asymptomatic infections are difficult to estimate. The invisible "iceberg" of mild infections needs to be estimated to fully assess disease severity.
 
"Population-based sero-epidemiology studies provide crucial information to assess development of herd immunity and calibrate our response to this pandemic" says Malik Peiris, Co-Director at HKU-Pasteur
 
In order to carry out age-stratified population-based sero-epidemiology, it is important to validate serological methods that can be used in such large-scale studies. HKU-Pasteur Research Pole and the School of Public Health at HKU have developed an ELISA assay biosafety level 2 containment, based on the recombinant receptor-binding domain (RBD) of the SARS-CoV-2 spike protein for use as a screening assay, and neutralization tests using live virus in biosafety level 3 containment as confirmatory tests. The RBD ELISA assay is specific and correlates well with a confirmatory test with neutralization, which provides greater assurance of protection.
 
"The RBD ELISA can be completed in a day, whereas the neutralization confirmation takes 4 days more"
says Chris Mok, team leader at HKU-Pasteur.
 
Thus, screening with our ELISA assay is a reliable approach for large-scale sero-epidemiological studies, which are crucial to assess infection attack rates in the population and to accurately define disease severity and herd immunity.
 

15 Apr 2020

Stability of SARS-CoV-2 in different environmental conditions

Malik Peiris, co-director at HKU-Pasteur, and Leo Poon, School of Public Health of the University of Hong Kong, reported in a recent publication on the stability of SARS-CoV-2 in different environmental conditions.

They tested the infectivity of the virus after submitting it to different temperatures, and investigated its stability on different surfaces. They showed that after an incubation temperature of 70°C, the time for virus inactivation was 5 mins, or more surprinsingly, that a detectable level of infectious virus could still be present on the outer layer of a surgical mask after 7 days. 

You can find the detailed outcomes online: Stability of SARS-CoV-2 in different environmental conditions

03 Apr 2020

Chris Mok and team to publish in Science to provide molecular insights into antibody recognition of SARS-CoV-2

Chris Mok, team leader at HKU-Pasteur, published in Science with his team and with colleagues from Scripps Research Institute, USAproviding molecular insights into antibody recognition of SARS-CoV-2:

>>> A highly conserved cryptic epitope in the receptor-binding domains of SARS-CoV-2 and SARS-CoV

This paper sheds new light into antibody recognition of SARS-CoV-2. To this end, they used the Receptor Binding Domain (RBD) of the Spike protein of SARS-CoV-2, which is the region of the Spike protein that allows virus entry into cells by interacting with its specific receptor.  

They took advantage of CR3022, a neutralizing monoclonal antibody previously isolated from a convalescent SARS patient, to determine its crystal structure in complex with the RBD of the SARS-CoV-2 Spike protein. This antibody targets a highly conserved epitope that enables cross-reactive binding with the Spike proteins of both SARS-CoV and SARS-CoV-2. Structural alignment of the CR3022-SARS-CoV-2 RBD complex with the ACE2-SARS-CoV RBD complex further indicates that binding of CR3022 would not clash with ACE2.  

This analysis implies that the neutralization mechanism of CR3022 for SARS-CoV does not depend on direct blocking of receptor binding, which is consistent with the observation that CR3022 does not compete with ACE2 for binding to the RBD. Overall, this study provides insight into how SARS-CoV-2 can be targeted by the humoral immune response and revealed a conserved, but cryptic epitope shared between SARS-CoV-2 and SARS-CoV.