New Zealand Scientists Publish Study of Antibodies That Neutralize COVID-19
by Neoteryx, on March 17,2021
AUCKLAND, NEW ZEALAND – March 2021 – New Zealand has proved to be one of the most successful nations in responding effectively to the coronavirus pandemic and controlling the spread of COVID-19 cases. Since SARS-CoV-2 struck in early 2020, New Zealand has kept its total count of COVID-19 infections under 2,500. In late February 2021, Auckland health officials reported three new cases of COVID-19, which threw New Zealand’s largest city into full lockdown to stem the spread. Despite these recent new cases, Auckland’s disease management track record has been impressive.
New Zealand’s unique environment as an island nation allows for controlled borders, which has aided its success in containing infections and preventing surges in COVID-19 cases. This also makes it a perfect case study environment for investigating immune responses among those in the population who have already recovered from COVID-19. For people who were exposed to COVID-19 early in the coronavirus pandemic, whether they had severe illness or only mild symptoms, the burning questions are: Have I developed antibodies against SARS-CoV-2, will these antibodies neutralize the virus, and how long will those antibodies last?
A research group at the University of Auckland launched a study to try and answer these very questions. In December of 2020, the research team led by Associate Professor Nikki Moreland, Alana Whitcombe and Dr. Reuben McGregor, released a preprint paper on their pilot study of COVID-19 antibody responses over time. The study, titled “Comprehensive analysis of SARS-CoV-2 antibody dynamics in New Zealand,” was published this month in the journal, Clinical and Translational Immunology (CTI). While the researchers used mainly plasma/serum samples for their study, whole blood microsamples collected using Mitra® devices from Neoteryx were also tested in a subset of the participants.
Auckland University’s longitudinal study involved a cohort of 112 participants (189 samples) who had previously tested positive for COVID-19. All samples were analyzed using a Luminex-based multiplex immunoassay, capable of measuring IgG (including subclasses 1, 2, 3 and 4), IgM and IgA antibodies to the Nucleocapsid, Spike and Receptor Binding Domain (RBD) of SARS-CoV-2. The longevity of the antibodies was measured over a 250-day period, with IgG against Spike and RBD persisting over the study period. In terms of classes of the IgG antibody, IgG1 and IgG3 were more prevalent and lasted longer than IgG2 and IgG4.
The research team also measured neutralizing antibodies, capable of blocking the entry of the SARS-CoV-2 viral invader and potentially protecting the host against COVID-19 re-infection, using a surrogate viral neutralization assay. “We learned that neutralizing antibodies to SARS-CoV-2 persist for up to eight months following a mild to moderate COVID-19 infection," said Dr. Reuben McGregor.
“This robust natural response, which appears to last for several months, can be attributed to the initial illness from exposure to SARS-CoV-2 without immune boosting through environmental re-exposure—something we are more certain of here in New Zealand given the lack of community transmission in our isolated setting,” said Associate Professor Nikki Moreland at the conclusion of the Auckland University study.
Lastly, the researchers tested the feasibility of using Mitra devices for measurement of total IgG in their Luminex assay. For this part of the study, Mitra extracts taken from whole blood (n=19) were compared with paired serum extracts. The researchers optimized the elution conditions, and assumed 50% adjustment to account for the HCT. Very high correlations were observed for Nucleocapsid (R2 = 0.9957), RBD (R2 = 0.9929), and Spike (R2 = 0.9918).
“The strong correlation between anti-RBD IgG and NAbs, combined with the demonstration in this study and by others that anti-RBD can reliably be measured from dried blood finger-prick samples, provides feasibility for future SARS-CoV-2 immunokinetic studies that incorporate RBD-IgG-based assays,” said Alana Whitcombe. “There is high value in conducting such studies at scale during COVID-19 Vaccine roll-out in settings like New Zealand, where the lack of circulating SARS-CoV-2 in the community provides an opportunity to gain novel insight on vaccine responses.”
Study details from the group’s published article are here: https://doi.org/10.1002/cti2.1261.
Whitcombe AL, McGregor R, Craigie A, et al at University of Auckland, New Zealand. Comprehensive analysis of SARS-CoV-2 antibody dynamics in New Zealand. medRxiv. December 2020:2020.12.10.20246751. doi:10.1101/2020.12.10.20246751
Baker MG, Wilson N, Anglemyer A, et al at University of Otago, Wellington, New Zealand. Successful Elimination of Covid-19 Transmission in New Zealand. August 2020. NEJM.org: https://www.nejm.org/doi/full/10.1056/NEJMc2025203
The COVID Time Machine: https://www.auckland.ac.nz/en/news/2021/01/12/the-covid-time-machine.html