MM is a hematological malignancy, supposed mainly not curable, except for some exceptional patients, despite the availability of numerous new drugs. The patients are highly susceptible to infections, both bacterial and viral, due to a defect immune status, both at the antibody level (hypogammaglobulinemia) and the cellular level. This immunosuppression is further worsened by the treatments, and especially high dose glucocorticoids used at each phase of the disease. Consequently, MM patients are highly susceptible to contract COVID19, and to develop a severe form. This has been confirmed in a first study in Spring, showing a mortality rate of 37%. Among all MM patients included in the cohort at the time of diagnosis of SARS-CoV-2 infection, blood samples will be collected at inclusion, at time of the infection acute phase in the most severe cases (when admitted in intensive care units), and at recovery. The following immune function tests will be evaluated, gammaglobulin measurements, lymphocytes counts, B, T, and NK cells analyses by cytometry, including exhaustion analyses. In addition, T cell repertoire sequencing looking for SARS-CoV-2- specific T cells, and serologies, will be evaluated at recovery and 6 months after MM treatment re-initiation.
