Cookies on this website
We use cookies to ensure that we give you the best experience on our website. If you click 'Continue' we'll assume that you are happy to receive all cookies and you won't see this message again. Click 'Find out more' for information on how to change your cookie settings.

Authors:Gallais et al. 

Journal/ Pre-Print:medRxiv 

Tags: Clinical, Diagnostics, Immunology/Immunity 

Research Highlights

  1. Exposure of individuals to SARS-CoV-2 positive patients could lead to the development of COVID-19 symptoms and SARS-CoV-2 specific T cell responses, in the absence of seroconversion. 

Summary

Nine SARS-CoV-2-infected patients from seven families developed mild COVID-19 symptoms, SARS-CoV-2 specific T cell responses and seroconversion for anti-viral immunoglobulin.  Of the eight household members who were exposed to the infected individuals, six reported COVID-19-like symptoms yet did not produce an antibody response according to three distinct antibody tests. Six of the eight exposed individuals did however produce SARS-CoV-2 specific T cell responses against viral structural and accessory proteins. Even though the study is limited in sample size, it shows SARS-CoV-2 specific T cell responses in the absence of seroconversion. The authors argue that reliance on serological testing would lead to aunderestimation of COVID-19 prevalence, although the incidence of this phenomenon is not yet established. It would be also of interest to understand how the absence of seroconversion impacts long-term protection from reinfection. 

Impact for SARS-CoV2/COVID19 research efforts  

Understand the immune response to SARS-CoV2/COVID19  

Develop diagnostic tools for SARS-CoV2/COVID19 
 

Study Type  

  • In vitro study 

  • Patient Case study 

Strengths and limitations of the paper 

Novelty: Gallais et al. described the absence of SARS-CoV-2 specific humoral responses, despite the development of mild symptoms and specific T cell responses. Possible underestimation of COVID-19 prevalence if epidemiological data is based on antibody titres. 

Standing in the field:  A strength in this study is the use of three commercial serological assays for S and N-specific immunoglobulin.   The discrepancy between humoral and cellular responses is confirmed in a recent larger cohort (https://www.biorxiv.org/content/10.1101/2020.06.29.174888v1) where interestingly healthy donors and exposed relatives were twice as likely to have virus-specific memory T cell responses than antibody responses. 

Appropriate statistics:No statistics used 

Viral model used: SARS-CoV-2 PCR-confirmed infected patients and exposed relatives from March 2020 in Strasbourg, France. T cell responses against common coronavirus (HCoV-299E and HCoV-OC43) peptides was also assessed. 

Translatability: Virus-specific T cell responses may be a more sensitive measure of SARS-CoV-2 infection than serological assays.   

Main limitations:  

  • Small sample size and no grouped statistics, although the patient information is well described.  It is not clear if the index patients or contacts have pre-existing conditions or medications.   

  • The enrolment strategy for these patients is unclear.  If these households were selected for their discrepancies in seroconversion after SARS-CoV-2 exposure, what was the total number of households available for enrolment?  This is important to understand the frequency of the absence of seroconversion.