thevaccinereaction--2020-09-07--The T-Cell Response to COVID-19 Infections and Immunity

Research into the immune response to SARS-CoV-2 infection has primarily focused on analyzing the blood of patients , who have recovered from COVID-19 , to measure whether they have developed neutralizing antibodies to the virus .
A key finding early in the pandemic was that any antibodies produced tend to be very short-lived.1 Several recent studies , however , have shown “ encouraging signs of strong , lasting immunity , ” including in patients who have had mild cases of COVID-19.2 One of the studies , which has not yet been peer reviewed , reported finding that , “ immunity @ @ @ @ @ @ @ after SARS-CoV-2 infection.
” 3 A study currently under review by the journal Nature , found that , “ recovered individuals developed SARS-CoV-2-specific IgG ( Immunoglobulin G ) antibody and neutralizing plasma , as well as virus-specific memory B- and T-cells that not only persisted , but in some cases increased numerically over three months following symptom onset.
” 4 This is the information researchers have been looking for to determine whether those who recover from mild or asymptomatic COVID-19 develop a strong and durable immunity that could lead to reduced transmission and @ @ @ @ @ @ @ Antibodies are Not the Only Important Players in Developing Immunity As explained by viral immunologist Zania Stamataki , PhD , there are two major types of “ memory ” immune responses that allow the body to recognize and quickly mount a protective response to a microbial infection.6 Among many other tools available in the complex human immune system , one type of response is powered by B-cells , which produce antibodies .
Another type is the T-cell response , which may involved either a “ killer T-cell ” that causes the destruction of @ @ @ @ @ @ @ ” that triggers B-cells to produce new antibodies.7 T-cell activation is reportedly common in patients with COVID-19 and has been seen in early results of vaccine trials .
T-cell activation may be able to prevent a second infection even in the absence of antibodies .
If SARS-CoV-2 follows the pattern of other coronaviruses , memory T-cells may last longer than antibodies.8 A study conducted by the Karolinska Institute in Sweden found that for every one person who tested positive for antibodies to SARS-CoV-2 , two were found to have T-cells specific for the @ @ @ @ @ @ @ patients with severe disease were likely to develop higher levels of antibodies and T-cells , while those with mild or asymptomatic disease generally had lower levels of antibodies but still showed a strong T-cell response .
Routine antibody testing would fail to identify patients who do not have antibodies but do have the T-cells that could provide protection from COVID-19 infection and transmission.9 According to Hans-Gustaf Ljunggren , MD , PhD , senior co-author of the Swedish study : T-Cell Cross-Reactivity May Be Linked to Infection With the Common Cold Another preprint study @ @ @ @ @ @ @ Berlin , Germany found that 15 of 18 hospitalized patients had helper T-cells specific to the spike protein on the virus .
Questioning whether those who have not been infected with SARS-CoV-2 might still produce the cells to fight infection , Andreas Thiel , PhD and fellow researchers found that 34 percent of 68 uninfected people had helper T-cells able to recognize SARS-CoV-2 .
This cross-reactivity was also identified in about half of stored blood samples from 2015 to 2018—before the world had heard of COVID-19 .
The researchers suggested that these cells @ @ @ @ @ @ @ previous infection with one of the four coronaviruses that cause the common cold , explaining that proteins in the other coronaviruses resemble those of SARS-CoV-2 .
Viral immunologist Steven Varga , PhD of the University of Iowa proposes that , “ one reason that a large chunk of the population may be able to deal with the virus is that we may have some small residual immunity from our exposure to common cold viruses.
” 11