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Author: Mia
Introduction: Most studies on immunity to SARS-CoV-2 focus on circulating antibodies, with limited understanding of mucosal defenses that prevent virus replication and further spread. Recently, a research team analyzed the nasal and plasma antibody responses of COVID-19 hospitalized patients one year later, including the period of SARS-CoV-2 vaccination.
Recently, researchers from Imperial College London and the University of Liverpool published a study titled "SARS-CoV-2-specific nasal IgA wanes 9 months after hospitalisation with COVID-19 and is not induced by subsequent vaccination" in the Lancet journal EBioMedicine. The study showed that the decline in nasal IgA responses 79 months after infection with COVID-19 and the minimal impact of subsequent vaccination may explain the lack of durable nasal defense against reinfection after initial infection and the limited impact of vaccination on transmission. This finding highlights the need to develop a vaccine against and that enhances nasal immunity.
DOI: https://doi.org/10.1016/j.ebiom.2022.104402
Research Background
01
Intramuscular vaccines are highly effective in preventing severe COVID-19 and can reduce hospitalizations. However, current vaccines provide only short-lived protection against respiratory virus replication, further spread and the continued emergence of mutations. In contrast, mucosal immune defense can be induced after respiratory infection SARS-CoV-2, inhibiting viral replication and spread. Nasal IgA is the most abundant mucosal antibody and provides an important first-line defense against respiratory tract infections .
To date, there have been few studies on the long-term persistence of nasal antibodies, and those that have been conducted have been relatively small and have yielded mixed results - suggesting that nasal antibodies can last between three and nine months. Therefore, further studies on mucosal and systemic immunity in critically ill patients are necessary.
Through the ISARIC4C and PHOSP-COVID consortium, the research team collected plasma and nasal absorption samples from 446 adults hospitalized with COVID-19 between February 2020 and March 2021. They then measured antibodies in the participants' noses and plasma, as well as the duration of antibody neutralization responses to the original strain, the Delta and Omicron (BA.1) variant , by electrochemiluminescence.
Plasma antibody responses are more durable than nasal antibody responses
02
The results of the study showed that nasal antibodies (anti-S and anti-NP IgA) appeared within 4 weeks after COVID-19 infection, but weakened to the same level as pre-COVID-19 pandemic controls after 9 months. Anti-spike protein neutralizing antibodies (anti-S-IgG) appeared within 14 days after infection, increased 2181-fold after 9 months, and remained higher than pre-pandemic controls thereafter. These data demonstrate that nasal and plasma IgG responses are durable after COVID-19, whereas first-line defense nasal IgA antibodies only persist for 9 months..
Nasal and plasma antibody responses 12 months after infection
Of all participants, 307 had received their first dose of vaccine between 6 and 12 months of age. After vaccination, both nasal and blood antibodies increased, but there were obvious differences in nasal IgA and IgG responses. The changes in nasal antibody IgA were small and temporary. Therefore, vaccination cannot fully restore mucosal IgA responses.
In addition, in the neutralization response analysis of the strains, nasal IgA and IgG responses combining Delta and Omicron RBD appeared within 28 days after infection and continued to increase for at least 9 months. However, nasal IgA bound Omicron for the shortest time . At its peak, nasal IgA binding to and Omicron was only 10-fold higher than in controls, while nasal IgA binding to the original strain RBD was 28-fold higher. This may explain to a certain extent why Omicron is easily infected with repeatedly.
Research Significance
03
Researchers said that if future vaccines are to completely prevent infection and transmission, they will need to significantly increase nasal IgA. So far, intranasal and aerosolized vaccines show the most promise in this regard. Therefore, the development of mucosal vaccines must be prioritized to better prevent respiratory infections.
Reference:
https://www.thelancet.com/journals/ebiom/article/PIIS2352-3964(22)00584-9/fulltext
Note: This article is intended to introduce the progress of medical research and cannot be used as a reference for treatment plans. If you need health guidance, please go to a regular hospital.
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