Wednesday, November 25, 2020 8:23:59 PM
Aylin Woodward
Wed, November 25, 2020, 8:36 AM PST·6 min read
Immunity to the coronavirus involves more than just antibodies. T cells and B cells protect us long-term, too.
A new study found that these other elements of immunity persist at least eight months in a majority of COVID-19 patients and could protect most people against coronavirus reinfection for years.
We now have the best answer yet to a crucial, lingering question about COVID-19: how long immunity lasts.
New research suggests that recovered coronavirus patients likely have a robust immune memory that persists for at least eight months. This memory relies on more than just antibodies — it also involves white blood cells known as T cells and B cell that have impressive powers of recollection. Combined, these layers of protection enable the immune system to recognize and re-attack the coronavirus should it ever invade again, thereby preventing another infection.
To assess how long immunity to the virus lasts across these various layers of the immune system, scientists measured how many — and what types of — immune cells recovered coronavirus patients had months after they got sick. Their research, though not yet peer-reviewed, offers hope that those who've already gotten infected likely won't be ill again for quite some time.
"Most people are making most parts of the immune response to this virus, and those parts are still around six to eight months later," Shane Crotty, a virologist at La Jolla Institute for Immunology in California and a co-author of the study, told Business Insider. "That looks like generally good news for having protective immunity."
While antibodies wane, T cells and B cells persist
Some research has suggested that coronavirus antibodies — blood proteins that protect the body from subsequent infection — fade within a few months. But concerns about those findings can discount the role of killer T cells, which identify and destroy infected cells, as well as helper T cells that inform B cells about how to craft new antibodies.
"All of those elements are designed to work together: If in any given person one's not so great, the other arms of the immune system can compensate. So it makes sense to measure everything," Crotty said.
A scanning electron micrograph of a human T lymphocyte (also called a T cell) from the immune system of a healthy donor. NIAID
So his group measured both types of T cells, as well as B cells and antibodies, in blood samples from 185 people who'd recovered from COVID-19. Nearly 40 of the participants gave blood multiple times, some more than six months after their illness. This enabled the researchers to assess how patients' immune responses changed over time.
Their results showed that patients' levels of coronavirus-specific T cells declined slightly between four and six months, then held steady after that. The researchers think it's likely that lT cells and antibodies stay consistent after that six-month mark, since that's typical of other viruses.
"It takes one to two weeks for antibodies and T cell responses to develop after an infection. Those then increase and peak," Alessandro Sette, an immunologist at La Jolla and Crotty's coauthor, told Business Insider. "Between four and six months they go down, and then tend to plateau out around six months.
"What you see at six to eight months is what you get in terms of immune response, so that's when you want to look for any indication whether you have developed a memory or not."
The study results also indicated that patients' B cell levels increased between the one-month and six-month marks. That's especially good, Sette explained, since B cells are the source of future antibodies.
"Once the initial viral invasion is gone, B cells will stop fighting, stop making antibodies," he said. "But they're still there if the attack resumes: If you have an expanding army of B cells circulating in the body, that would regenerate a antibody response."
Antibodies, however, declined measurably by the six-month mark, according to the study. But Crotty said that decline is "quite reasonable for any infection" and not on its own a reason to be concerned.
Coronavirus-targeting T cells could last for years
Sette and Crotty could only look at recovered coronavirus patients eight months post-infection, since the pandemic began about a year ago. But they think the slow rate of decline in patients' T cell and B cell counts means those cells will last far longer than the time period analyzed in the study.
"The immune responses are following the expected playbook, and they're stable over at least eight months," Sette said, adding that "the trajectory doesn't indicate they're going to crash at eight months and one day."
White blood cells developed in response to other viruses can stick around for years. T cells specific to smallpox, for example, take about 10 years to disappear after an infection, while B cells for that virus stick around for 60 years.
T cells specific to SARS, another coronavirus that shares 80% of its genetic code with this new one, also seem to stick around long-term. A July study looked for T cells in blood samples from 23 people who survived SARS. Sure enough, those survivors still had SARS-specific memory T cells 17 years after getting sick.
A small number of patients had 'weak immune memory'
Crotty's study found that about 90% of people develop robust immunity to the coronavirus — undergirded by antibodies, T cells, and B cells. But not everyone developed all three immune elements to the same degree, and a small subsection of participants developed only some, or none, of them.
Those patients seem to have "quite weak immune memory," Crotty said, so could be susceptible to reinfection relatively quickly.
"You really want to have the whole orchestra of the immune system coming together to defeat the virus," Sette said.
The reason for this person-to-person variation isn't clear, but the study authors found that patients who fared better during their bout of COVID-19 had multiple types immune cells working for them. Those who fared poorly had one or less.
But until scientists have more time to study the virus, Sette and Crotty said, there won't be a way to predict how long a given person's coronavirus immunity will last after they're infected.
"There's just no way to do quick blood test to say you're going to have immune memory for 10 years," Crotty said. "So we'll just have to wait and see."
Immunological memory to SARS-CoV-2 assessed for greater than six months after infection
Jennifer M. Dan, Jose Mateus, View ORCID ProfileYu Kato, Kathryn M. Hastie, Caterina E. Faliti, Sydney I. Ramirez, April Frazier, Esther Dawen Yu, Alba Grifoni, Stephen A. Rawlings, Bjoern Peters, Florian Krammer, Viviana Simon, Erica Ollmann Saphire, Davey M. Smith, Daniela Weiskopf, Alessandro Sette, View ORCID ProfileShane Crotty
doi: https://doi.org/10.1101/2020.11.15.383323
ABSTRACT
Understanding immune memory to SARS-CoV-2 is critical for improving diagnostics and vaccines, and for assessing the likely future course of the pandemic. We analyzed multiple compartments of circulating immune memory to SARS-CoV-2 in 185 COVID-19 cases, including 41 cases at ≥6 months post-infection. Spike IgG was relatively stable over 6+ months. Spike-specific memory B cells were more abundant at 6 months than at 1 month. SARS-CoV-2-specific CD4+ T cells and CD8+ T cells declined with a half-life of 3-5 months. By studying antibody, memory B cell, CD4+ T cell, and CD8+ T cell memory to SARS-CoV-2 in an integrated manner, we observed that each component of SARS-CoV-2 immune memory exhibited distinct kinetics.
Recent INO News
- INOVIO to Present at Upcoming Scientific Conference • PR Newswire (US) • 09/17/2024 08:30:00 PM
- Form 424B5 - Prospectus [Rule 424(b)(5)] • Edgar (US Regulatory) • 08/13/2024 10:22:02 AM
- Form 8-K - Current report • Edgar (US Regulatory) • 08/13/2024 10:06:54 AM
- INOVIO Reports Second Quarter 2024 Financial Results and Recent Business Highlights • PR Newswire (US) • 08/08/2024 08:05:00 PM
- INOVIO Reports Inducement Grant Under Inducement Plan • PR Newswire (US) • 08/01/2024 08:05:00 PM
- Inovio Receives Advanced Therapy Medicinal Product Certificate from European Medicines Agency for Quality and Non-Clinical Data for Lead Candidate INO-3107 • PR Newswire (US) • 07/25/2024 08:05:00 PM
- INOVIO to Report Second Quarter 2024 Financial Results on August 8, 2024 • PR Newswire (US) • 07/25/2024 12:00:00 PM
- INO-3107 Awarded the Innovation Passport Designation Under U.K. Government's Innovative Licensing and Access Pathway • PR Newswire (US) • 07/11/2024 12:00:00 PM
- INOVIO Announces Appointment of Steven Egge as Chief Commercial Officer • PR Newswire (US) • 07/02/2024 08:05:00 PM
- INOVIO Reports Inducement Grant Under Inducement Plan • PR Newswire (US) • 07/01/2024 08:00:00 PM
- INOVIO Added to Russell 2000® Index Effective July 1, 2024 • PR Newswire (US) • 07/01/2024 12:00:00 PM
- INOVIO to Participate in Virtual Fireside Chat Hosted by Stephens Inc. • PR Newswire (US) • 06/04/2024 12:00:00 PM
- INOVIO Reports Inducement Grants Under Inducement Plan • PR Newswire (US) • 05/31/2024 08:48:00 PM
- Form 8-K - Current report • Edgar (US Regulatory) • 05/28/2024 08:01:02 PM
- Form 4 - Statement of changes in beneficial ownership of securities • Edgar (US Regulatory) • 05/22/2024 08:51:58 PM
- Form 4 - Statement of changes in beneficial ownership of securities • Edgar (US Regulatory) • 05/22/2024 08:51:38 PM
- Form 4 - Statement of changes in beneficial ownership of securities • Edgar (US Regulatory) • 05/22/2024 08:51:16 PM
- Form 4 - Statement of changes in beneficial ownership of securities • Edgar (US Regulatory) • 05/22/2024 08:51:00 PM
- Form 4 - Statement of changes in beneficial ownership of securities • Edgar (US Regulatory) • 05/22/2024 08:50:34 PM
- Form 4 - Statement of changes in beneficial ownership of securities • Edgar (US Regulatory) • 05/22/2024 08:50:11 PM
- Form 4 - Statement of changes in beneficial ownership of securities • Edgar (US Regulatory) • 05/22/2024 08:49:53 PM
- Form 4 - Statement of changes in beneficial ownership of securities • Edgar (US Regulatory) • 05/16/2024 09:13:02 PM
- Form 4 - Statement of changes in beneficial ownership of securities • Edgar (US Regulatory) • 05/16/2024 09:12:10 PM
- Form 4 - Statement of changes in beneficial ownership of securities • Edgar (US Regulatory) • 05/16/2024 09:11:09 PM
- Form 4 - Statement of changes in beneficial ownership of securities • Edgar (US Regulatory) • 05/16/2024 09:10:00 PM
VHAI - Vocodia Partners with Leading Political Super PACs to Revolutionize Fundraising Efforts • VHAI • Sep 19, 2024 11:48 AM
Dear Cashmere Group Holding Co. AKA Swifty Global Signs Binding Letter of Intent to be Acquired by Signing Day Sports • DRCR • Sep 19, 2024 10:26 AM
HealthLynked Launches Virtual Urgent Care Through Partnership with Lyric Health. • HLYK • Sep 19, 2024 8:00 AM
Element79 Gold Corp. Appoints Kevin Arias as Advisor to the Board of Directors, Strengthening Strategic Leadership • ELMGF • Sep 18, 2024 10:29 AM
Mawson Finland Limited Further Expands the Known Mineralized Zones at Rajapalot: Palokas step-out drills 7 metres @ 9.1 g/t gold & 706 ppm cobalt • MFL • Sep 17, 2024 9:02 AM
PickleJar Announces Integration With OptCulture to Deliver Holistic Fan Experiences at Venue Point of Sale • PKLE • Sep 17, 2024 8:00 AM