Maintenance of neutralizing SARS-CoV-2 antibodies over five months in convalescent SARS-CoV-2 afflicted patients.
Short title: Serologic study on the longevity of humoral immunity against SARS-CoV-2.
Sissy Therese Sonnleitner1,3, Martina Prelog4, Bianca Jansen1, Chantal Rodgarkia-Dara5, Sarah Gietl1, Carmen Maria Schönegger1, Stephan Koblmüller2, Christian Sturmbauer2, Wilfried Posch3, Giovanni Almanzar4, Hanna Jury4, Norbert Nowotny6,7, Gernot Walder1.
1 Dr. Gernot Walder GmbH, Medical Laboratory, Department of Virology, 9931 Ausservillgraten 30, Austria. sissy.lamprecht@infektiologie.tirol
2 Institute of Biology, University of Graz, Universitaetsplatz 2, 8010 Graz, Austria.
3 Division of Hygiene and Medical Microbiology, Medical University of Innsbruck, 6020 Innsbruck, Austria.
4 University Hospital Wuerzburg, Department of Pediatrics, University of Wuerzburg, Josef-Schneider-Str. 2, Wuerzburg, Germany.
5 THP Medical products, Shuttleworthstrasse 19, 1210 Vienna, Austria.
6 Viral Zoonoses, Emerging and Vector-Borne Infections Group, Institute of Virology, University of Veterinary Medicine Vienna, Veterinaerplatz 1, 1210 Vienna, Austria.
7 Department of Basic Medical Sciences, College of Medicine, Mohammed Bin Rashid University of Medicine and Health Sciences, Building 14, Dubai Healthcare City, Dubai, United Arab Emirates.
ABSTRACT
Level and duration of protective immunity against SARS-CoV-2 after primary infection is of crucial importance for preventive approaches. In order to provide evidence for the longevity of specific antibodies, we investigated the generation and maintenance of neutralizing antibodies of convalescent SARS-CoV-2-afflicted patients over a five month period post primary infection using an immunofluorescence assay, a commercial chemiluminescent immunoassay and an in-house enzyme-linked plaque-reduction neutralization assay.
We present the successful application of an improved version of the plaque-reduction neutralization assay, which can be analyzed optometrically, significantly simplifying the interpretation of the results. Based on the results of the plaque-reduction neutralization assay, neutralizing antibodies were maintained in 85.3% of convalescent individuals without significant decay over five months. Furthermore, a positive correlation between severity of infection and neutralizing titer was shown.
In conclusion, SARS-CoV-2-afflicted individuals have been proven to be able to establish and maintain neutralizing antibodies over a five months’ period after primary infection which allows to hope for long-lasting presumably protective humoral immunity after wild-type infection or even after vaccination.
Keywords: SARS-CoV-2, immunity, longevity, neutralization test, IgG antibodies
INTRODUCTION
Little is known about persistence of the immunologic footprint left in a convalescent SARS-CoV-2 afflicted patient and first publications showed discrepancies concerning the longevity of specific IgG antibodies . The development of specific antibodies in the acute phase of COVID-19 is well documented and most patients display specific antibody responses between day 10 and day 21 post infection (Kellam & Barclay, 2020; Long et al., 2020). Whereas milder courses of disease may result in a delayed generation of antibodies, in a small number of cases, patients may even stay antibody-negative after infection with SARS-CoV-2 . In comparable studies, seropositivity rate reached up to 90% and 100% Studies investigating the persistence of the antibody response are rare, but it is known that antibodies to other coronaviruses wane over time, in the range of 12 – 52 weeks from the onset of symptoms onwards (. Short follow-up studies showed preservation of SARS-CoV-2 IgG antibody levels over the course of seven weeks (Xiao et al., 2020), at least in 80% of patients (Jianyun et al., 2020). In comparison, 90% and 50% of SARS-CoV-1 infected patients have been shown to maintain IgG antibodies for two and three years, respectively (.
Short-term immunity is defined as the wane of specific antibodies after a period of about 40 weeks, which leads to annual or otherwise periodic outbreaks as is well-known from nonSARS-like human coronaviruses (nonSARS-like hCoVs) as well as influenza viruses . The knowledge of duration of protective immunity against SARS-CoV-2 after primary infection is of great importance for the understanding of possible future scenarios of herd protection after wild-type infection or vaccination.
In this study, we accompanied 34 volunteers representing the first SARS-CoV-2 afflicted patients in East Tyrol and investigated the course of specific antibody responses beginning in convalescence 21-43 days after the onset of symptoms until 5 months (22 weeks) later.
In order to analyze potentially protective neutralizing IgG antibodies against SARS-CoV-2, we developed and introduced a fast and reliable novel enzyme-linked neutralization assay (ELNA) that allows the determination of neutralization antibodies within 30 hours.
MATERIAL & METHODS