Pb2070: immune responses after sars-cov-2 mrna-vaccination and infection at single cell resolution in patients with multiple myeloma

Topic: 13. Myeloma and other monoclonal gammopathies - Biology & Translational Research Background: Multiple myeloma (MM) is plasma cell neoplasia that is associated with suppression of the immune system and an elevated risk of COVID-19. To reduce COVID-19 associated mortality, mRNA-based vaccination has been routinely implemented. However, patients with MM show heterogenous and variant-dependent serological and cellular responses. To date, there is no functional or molecular data why patients with MM show such ambiguous response levels and how these resemble the immune status after breakthrough infection (BT). Aims: The present study aimed at deciphering immune responses after three doses of BNT162b2 mRNA-based vaccination or SARS-CoV-2 BT on the serological and functional T-cell level as well as at single cell resolution in the peripheral immune cell compartment in patients with MM. Methods: The serological responses were measured by anti-Spike IgG levels and in vitro plaque reduction neutralization test. The T-cell responses were evaluated by flow cytometry-based quantification of cytokine-positive SARS-CoV-2 specific T-cells after peptide stimulation. Peripheral immune cell subsets were quantified by flow cytometry. Additionally, T-, NK- and B-cell populations of peripheral blood mononuclear cells were subjected to cellular indexing of transcriptomes and epitopes (CITE) sequencing of whole transcriptome and targeted surface proteome after vaccination and/or BT. Additionally, disease-related and clinical outcome data were collected from electronical health care systems. Results: In the study cohort of 100 patients with MM and 23 healthy controls (HC), most patients with MM achieved a sufficient, but in comparison to HC still impaired, serological response against the wild-type (WT) strain while responses against the Omicron variant were similarly reduced in MM and HC after 3 doses of BNT162b2. The majority of patients with MM also displayed sufficient T-cell responses against WT and inferior response levels against Omicron. Interestingly, patients exhibiting a BT, regardless of the timepoint of BT, showed higher serological and/or T-cell responses with again heterogenous responses stratified per virus variant. Clinical factors associated with an inferior response after 3 doses were concomitant anti-MM therapy or low CD19+ B-cell counts. Single cell CITE sequencing enabled in-depth characterization of the peripheral immune cell compartment in the context of vaccination responses. Here, serological and T-cell responders showed significantly higher abundancies of CD4+ cytotoxic T cells, CD4+ memory T-cells and either FAS+ or TIM3+ CD16bright/CD56dim NK-cells. On a molecular level, these cells were characterized by a prominent enrichment of cytokine-responsive transcriptional patterns in the context of TNF-α, IFN-α, IL-1 and IL-12 response and signaling. The abundancies and functional qualities of these cell populations were validated by in vitro flow cytometry. Remarkably, patients with MM after BT showed similar cytokine-responsive single cell patterns regardless of the previous vaccination response status. Summary/Conclusion: Most patients with MM exhibited sufficient serological and T-cell responses against WT SARS-CoV-2 after mRNA vaccination or BT highlighting adequate immunogenicity despite the MM-associated immune deficit. However, responses against other variants were reduced and heterogenous. At single cell resolution, vaccination response or BT associated with cytokine-responsive patterns in peripheral immune cells which may be relevant for further improving vaccination approaches in immunosuppressed patients. Keywords: Immune response, Vaccination, Multiple myeloma, COVID-19