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Antibodies and T Cell Responses to COVID-19 Virus Persist Three Months After Infection
April 26, 2021
- SARS-CoV-2 has caused a pandemic that affects many countries with more than 13 million cases and at least 570,000 deaths as of July 15, 2020.
- Modeling research studies have shown that SARS-CoV-2 infection can produce immunity to reinfection for at least one year.
- A number of studies reported that patients infected with SARS-CoV-2 can produce an antibody response.
- However, reported data had focused mainly on hospitalized patients where only virus-specific IgG and IgM antibodies were analyzed.
- One study found that all their patients are seropositive for IgG and neutralizing antibodies 41 to 53 days after illness onset.
- In another study, researchers detected neutralizing antibodies and high concentration of IgG in most of their patients that are newly discharged or two weeks after discharged.
- In a recent study, neutralizing antibodies were detected in patients 8 weeks after discharged however, the concentration decreased significantly and about 13% of the symptomatic patients become negative for IgG antibody at the start of the convalescent stage.
- The convalescent stage refers to the late stage of infection where a patient starts to recover and returns to normal health, but may still be able to transmit the disease to others.
- These data suggest seeking more information about protective immunity and the proper amount of time that should be recommended for quarantine.
- Other researchers pointed to T cells as the potential key to solving this problem.
- Memory T cells specific to SARS-CoV-2 have been observed in the peripheral blood of one-case patient two weeks after the start of symptoms.
- Also, a number of studies reported the presence of CD8+ and CD4+ T cells specific to SARS-CoV-2 in most of the COVID-19 convalescent patients 3 to 5 weeks after the start of symptoms.
- A lot of studies can provide useful information about protective immunity however, the dynamics, duration, and nature of immunity produced during SARS-CoV-2 infection are still not well understood.
- In this study, researchers measured virus-neutralizing antibodies, antibodies against the spike protein, receptor binding domain, nucleoprotein of SARS-CoV-2, and the T cell responses up to 121 days after the start of symptoms.
- The study includes 25 patients infected with SARS-CoV-2.
- IgG against SARS-CoV-2 proteins as well as IgM against the receptor-binding domain was detected in all patients by 14 days after the start of symptoms with peak levels achieved by 15 to 30 days at the start of symptoms.
- Additionally, all patients produced neutralizing antibodies.
- The IgG and neutralizing antibodies were detectable 3 to 4 months after the start of symptoms.
- However, the concentration of IgM antibodies rapidly declined.
- About 65% of the patients have CD4+ or CD8+ T cell responses specific to COVID-19 virus 3 to 4 after the start of symptoms.
- The results provide important information that IgG, neutralizing antibodies, and T cell responses continue in most of the patients for at least 3 to 4 months after infection.