Forschung und Entwicklung
Corona-Forschung
Vektorassoziierte Erreger
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Chlamydia spp
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Sonstiges
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Omicron (B.1.1.529) BA.1 or BA.2-related effects on immune responses in previously naïve versus imprinted individuals: immune imprinting as an advantage in the humoral immune response against novel variants
Sissy Therese Sonnleitner, Samira Walder, Ludwig Knabl, Roswitha Poernbacher, Thomas Tschurtschenthaler, Eva Hinterbichler, Stefanie Sonnleitner, Viktoria Muehlmann, Wilfried Posch, and Gernot Walder
Abstract
Background: Immune imprinting is a phenomenon in which a person’s immune system develops a specific immunological memory of the pathogen or vaccine due to a previous exposure. This memory basically leads to a faster and stronger immune response in a subsequent contact to the same pathogen or vaccine. However, what happens if the pathogen has changed considerably in the meantime due to mutations in the main target region of antibodies, as in the evolution of SARS-CoV-2 from the ancestral strain to B.1.1.529 (Omicron)? In this case, does immune imprinting also confer an advantage in repeated contact and does it lead to a stronger immune response?
Method: To clarify these questions, we investigated the effects of immune imprinting in the context of SARS-CoV-2 by comparing a group of previously infection-naïve versus imprinted study participants and determined differences in humoral and cellular immune responses during and after infection with strain SARS-CoV-2 B.1.1.529 BA.1 and BA.2, respectively. We used a commercial CLIA, immunoblots, IFN-γ ELISpots and a plaque-reduction neutralization test to generate a clear and comparable picture of the humoral and cellular immune response in the two study groups.
Results: Imprinted participants developed significantly higher antibody titers and showed significantly stronger neutralization capacity against the ancestral strain, BA.1 and BA.5. The immune response of naïve study participants was narrower and related mainly to the receptor-binding domain, which resulted in a lower neutralization capacity against other strains including BA.5. Naïve study participants showed a significantly higher cellular immune response than the imprinted study group, indicating a higher antigenic challenge. The cellular immune response was directed against general structures of SARS-CoV-2 and not specifically against the receptor-binding domain.
Conclusion: Viral variant infection elicits variant-specific antibodies and prior mRNA vaccination or infection with a previous SARS-CoV-2 variant imprints serological responses toward the ancestral strain rather than variant antigens. On the other hand, our study shows that the initially higher specific antibody titers due to former imprinting via vaccination or prior infection significantly increased the humoral immune response, and therefore outperformed the humoral immune response of naïve study participants.
Keywords: SARS-CoV-2, omicron infection, immune response to omicron infection, serology, ELISpot, naïve versus imprinted, B.1.1.529
Links: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10225645/
Immune Responses Against SARS-CoV-2 WT and Delta Variant in Elderly BNT162b2 Vaccinees
Abstract
Residents of nursing homes are one of the most vulnerable groups during the severe acute syndrome coronavirus 2 (SARS-CoV-2) pandemic. The aim of this study was to characterize cellular and humoral immune responses in >70-year-old participants before vaccination, after first and second vaccination with BNT162b2, in contrast to second-dose-vaccinated participants younger than 60 years.
Links: https://www.frontiersin.org/articles/10.3389/fimmu.2022.868361/full
The mutational steps of SARS-CoV-2 to become like Omicron within seven months: the story of immune escape in an immunocompromised patient
Abstract
We studied a unique case of prolonged viral shedding in an immunocompromised patient that generated a series of SARS-CoV-2 immune escape mutations over a period of seven months. During the persisting SARS-CoV-2 infection seventeen non-synonymous mutations were observed, thirteen (13/17; 76.5%) of which occurred in the genomic region coding for spike. Fifteen (15/17; 88.2%) of these mutations have already been described in the context of variants of concern and include the prominent immune escape mutations S:E484K, S:D950N, S:P681H, S:N501Y, S:del(9), N:S235F and S:H655Y. Fifty percent of all mutations acquired by the investigated strain (11/22) are found in similar form in the Omicron variant of concern. The study shows the chronology of the evolution of intra-host mutations, which can be seen as the straight mutational response of the virus to specific antibodies and should therefore be given special attention in the rating of immune escape mutations of SARS-CoV-2.