SARS-COV-2 Reinfection
We need to know the following to follow this talk
What is reinfection?
What is reactivation?
What is a carrier?
What is false negative?
What is a false positive?
What is the sensitivity of a test?
What are immunoglobulins?
What is the role of IgM, IgG, and IgA?
What is seroconversion?
What is class-switching?
How long do the memory B cells live?
Notes
Immunoglobulins are formed from the day 7-10. First IgM and then IgG. (In case of SARS-COV-2 N protein, IgG is formed from the day 4th.)
IgA will be formed and sent to live in the mucus membranes.
Immunoglobulins peak near 3 months.
Formed antibodies live from a few weeks to months in the body.
Memory cells are formed in the process that will respond within 24-48 hours when the pathogens arrives in our body again.
New IgG and IgA are formed to combat the virus.
in case of SARS-COV-1 the antibodies were produced up to 3 years after the recovery.
In rhesus monkeys the SARS-COV-2 reinfection was not successful.
What can fail our immune system?
1. Weak immune system.
2. Immunosuppression
3. False negative tests
4. False positive tests
5. Viral mutation
Immune System Response to SARS-COV-2 is humoral in nature
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IgG against N proteins starts on the day 4
Most patients seroconverting by day 14
Peak specific IgM after 9 days of the infection.
Class switching to IgG in the second week.
Mobeen’s thoughts:
Enough time is not passed to know how long the antibodies will live?
Enough time is not passed to detect how long the memory cells can continue to produce antibodies to the virus?
I will take standard immune response and say that we will be immune for at least 3 months to 3 years. 3 months considering the existing antibodies. 3 years considering the memory cells.
Reinfection is not possible during the immune phase.
Reactivation is not proved.
Possibly false negative at the time of discharge. Or false positive at the re-test. Or a more sensitive test that can pick up the remnant RNA pieces from the mucus membranes and the cells.
GIT can keep the virus for 50 days after the recovery, but is not significant.
Do we have carriers? Folks that are asymptomatic but allow the virus to shed?
SARS-COV-1 (from 2012-2015) shows that the coronavirus antibodies can be produced for up to 3 years after the recovery.
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Reinfection could not occur in SARS-COV-2 infected rhesus macaques
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Excerpt from the study
Importantly, the unsuccessful rechallenge in NHP models suggested that the re-positivity from discharged patients could not be due to reinfection.
Re-detectable positive RNA test in recovered patients.
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Maybe the new test was hypersensitive in these RP patients (RP = re-detectable positive)?
Study found that the patients remained asymptomatic, their disease did not progress, and they did not cause infections to others.
Excerpt from the discussion
And from a recent longitudinal study in SARS-CoV-2 infected rhesus macaques, reinfection could not occur in convalescent monkeys [20]. Long-term follow-up of these close contacts with RP patients will warrant the evaluation of possible risk of RP
It may have been a less sensitive test.
Excerpt from the study
Our data support the notion that the false negatives using commercial kit may partially account for the RP, because the kits had only 30%–50% positive rate of detection
Maybe the immune response via IgA was not sufficient to clear the virus from the mucus membranes?
Excerpt from the study
Nor could we exclude immunological factors including low mucosal immune responses such as low IgA levels.
Study where patients were positive after 5-13 days of discharge. They did not have disease progression and they did not make their family members sick.
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Study thinks that these folks may be carriers.
Let’s understand the antibodies. Immune cell behavior, and memory cells. Let’s also look at the passive immunity i.e. antibodies given from outside.
Antibodies are produced about 7-10 days. IgM first and then IgG.
Memory B cells respond within 24-48 hours. (Reference: [ Ссылка ])
Passive immunity lasts from a few weeks to months.
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Possibly the virus got reactivated instead of reinfection
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