Distinct early IgA profile may determine severity of COVID-19 symptoms: an immunological case series

Christine Dahlke; Jasmin Heidepriem; Robin Kobbe; Rene Santer; Till Koch; Anahita Fathi; My L. Ly; Stefan Schmiedel; Peter H. Seeberger; Marylyn M. Addo; Felix F. Loeffler

We analyzed the data in more detail towards individual proteins over time ( Fig. 2a-d) . On day 6 in patient #1, the IgA antibodies ( Fig. 2a ) only target the ORF1ab polyprotein. At d10, the IgA response is still low and at d22 it turns into a broad response targeting the spike (S), membrane (M), ORF8, and nucleocapsid (N) proteins. While most IgA ORF1ab signals increase over time in patient #1, three signals decrease considerably. These might have resulted from a non-protective cross-reaction, which are silenced by the immune system. In contrast, in the same patient #1 (Fig. 2c) , some IgG responses were already present on d6, targeting the S and M protein. In patient #2 with mild symptoms (Fig. 2b ), we observed a stronger and more focused IgA response at d3 against the S, E, N, and ORF1ab proteins compared to patient #1, whereas in the IgG response ( Fig. 2d) , we only observed one stronger response towards the S protein.