Immunoglobulin fragment F(ab’)2 against RBD potently neutralizes SARS-CoV-2 in vitro

Authors: Pan et al. Link to paper: https://www.biorxiv.org/content/10.1101/2020.04.07.029884v1

Journal/ Pre-Print: bioRxiv

Key Words: neutralizing antibodies, SARS-CoV2, immunoglobulin fragment

RESEARCH HIGHLIGHTS 

1. Immunisation with recombinant RBD of SARS-CoV2 spike protein elicits high-titre neutralising antibodies in mice and in horses

2. These antibodies are active as F(ab’)2 fragments and block viral entry in vitro

SUMMARY

This study demonstrates that RBD is immunogenic and subsequently induces high titre nAbs in vivo in mice and horses. The neutralising potential of these antibodies was then examined in vitro. In comparison to nAbs yielded from a small cohort of patients who had since recovered from SARS-CoV-2, it was shown that a only a small proportion of these patients have effective nAbs.

IMPACT FOR SARS-COV2/COVID19 RESEARCH EFFORTS

· Vaccine development

· Preventing further transmission of SARS-CoV-2

· Treatment of SARS-CoV-2 positive patients

STUDY TYPE

· In vitro study

· In vivo study (e.g. mouse, NHP)

STRENGTHS AND LIMITATIONS OF THE PAPER

Novelty: They show that neutralizing antibodies against the RBD of the SARS-CoV2 spike protein produced in horses can neutralize the virus in vitro F(ab’)2 fragments and offer this as a better alternative to the treatment of COVID19 with convalescent plasma.

Standing in the field: Fits in with previous work looking at the role of neutralizing antibodies in SARS-CoV

Appropriate statistics: No statistics in paper

Viral model used: SARS-CoV2 live viruses used were from National Virus Resource, Wuhan institute of Virology, Chinese Academy of Sciences

Translatability: Yes, the use of horse F(ab’)2 fragments against RBD could be used as a therapeutic treatment for COVID-19

Main limitations: The mechanism of action by which F(ab’)2 fragments neutralize SARS-CoV-2 in vitro remains unclear i.e: do these fragments prevent binding to hACE2?

Whilst the in vitro neutralizing data looks very promising, it is not shown in this study whether or not this also works in vivo.

Lack of statistical analysis.