The patient, a 51-year-old male, presented with a three-day fever of 38.8°C, dry cough, and chills on March 25th. Other symptoms frequently reported in patients with COVID-19 were denied . In January 2019, he was diagnosed with multiple myeloma (MM) type IgA kappa, R-ISS stage I, and 1/4-CRAB criteria. Initially, he was treated with an induction quadruplet consisting of an anti-CD38 antibody in combination with bortezomib, lenalidomide and dexamethasone, followed by high-dose chemotherapy (HDCT) with melphalan 200 mg/m2 and autologous stem cell transplant (ASCT) in September 2019. He achieved complete remission after ASCT but remained MRD positive by flow cytometry (sensitivity 10-5). From January 2020 onwards, he received continuous lenalidomide maintenance treatment.
During monthly follow-up examination, we noticed severe type IgA and IgM immunoparesis, CTC grade II neutropenia, and CTC grade II lymphocytopenia. In January 2020, we also noticed a CD4+ T cell deficiency with 109 CD4+ T cells/ µl (normal values: 300-1400/µL) of whole blood.
At admission, a CT chest scan indicated mild bilateral pulmonary infiltrates, and community acquired respiratory viruses (CARV)-PCR testing showed positivity for SARS-CoV-2. Lenalidomide maintenance treatment was paused. Laboratory examinations showed neutropenia, lymphocytopenia, as well as moderately increased C-reactive protein (CRP) and interleukin-6 (IL-6) levels (Supplementary Tab. I). However, viral RNA was not detectable in the peripheral blood. During hospitalization, clinical symptoms worsened, and the fever persisted with 39.2°C. Important laboratory parameters, as summarized in Supp. Tab. I, showed lymphocytopenia (CTC grade IV), neutropenia (CTC grade I-III), a temporary decrease in the number of monocytes that persisted during hospitalization, and increased IL-6 levels with a maximum on day +6 (26.5 pg/ ml), accompanied by a slight increase in CRP, LDH and D-dimers. No alterations in pro-calcitonin, NT-proBNP, serum-creatinine or liver enzymes were detected. The clinical symptoms improved, and the temperature normalized from day +8, so that the patient could be discharged on April 2nd (day +9 from COVID-19 diagnosis, and day +12 from first symptoms).
Since then, he was regularly examined in our outpatient department. Neutrophil counts regenerated to CTC grade I neutropenia by April 24th (day +29), so we decided to resume lenalidomide maintenance.
Summarized, we observed that COVID-19 took a rather mild clinical course despite pulmonary affection in an immunocompromised patient with hematologic disease. We therefore raised the question on the immunological response that had combatted COVID-19, and we continued monitoring the immune response under re-treatment with lenalidomide. We quantified innate and adaptive immune cell subpopulations by multicolor flow cytometry, specific T-cell responses to SARS-CoV2, and cytokine serum levels during the course of disease and after re-introduction of lenalidomide until day +174. Despite overall lymphocytopenia with decreased CD3+ T cell numbers at COVID-19 diagnosis (Fig. 1a, Supplementary Tab. I), we observed a robust increase in cytotoxic CD3+CD8+ T cells with counts ranging from 233 cells/µl to 438 cells/µl of whole blood. The increased CD8+ T cell numbers were accompanied by an extraordinarily strong expression of HLA-DR on 86-95% of total CD8+ T-cell population, which is a marker for late activation (Fig. 1c), while CD69-expression as a marker of early activation remained constant (Fig. 1b).
CD19+ B-cell and CD3/CD56+ NK-cell levels were diminished at COVID-19 diagnosis, regenerated during the observation period, but started to decrease after lenalidomide re-introduction (Supplementary Tab. I).
Moreover, we followed up on innate immunity-derived cytokine response by monitoring Interleukin-1β (IL-1β), IL-6, Interleukin-8 (IL-8), Interleukin-10 (IL-10) and IP-10 (CXCL10, marker for interferon- γ) levels (Fig. 2a). To compare and rank the measured cytokine values into the COVID-19 landscape, we co-evaluated cytokine profiles from an age-matched patient with severe (= WHO scale 6) and with moderate COVID-19 symptoms (< WHO scale 4; Fig. 2b). As indicated by moderately elevated IP-10, the innate immune response was reflected by moderate induction of interferon-γ (Fig. 2b) . Although our patient had significantly elevated IL-6 levels during the hospitalization period, the levels normalized as the symptoms improved (Supplementary Tab. I, Fig. 2a). This was unlike to a critically ill control patient, whose IL-6, IL-1β and IP-10 levels persisted at high levels even 3 weeks after the COVID-19 diagnosis. In contrast, IL-10, known as anti-inflammatory regulator of immunity to infection , was strongly elevated in the myeloma patient but low in a critically ill COVID-19 patient.
Next, we performed an IFN-y ELISPOT assay with patient´s peripheral blood mononuclear cells (PBMCs) that were collected at day+44 and day +174, to examine the specific effector memory T-cell response to SARS–CoV-2 (Fig. 2 e-f). Despite low initial naïve T-cell counts, the patient was able to develop specific T-cell memory subsets that showed a type II interferon reactivity to peptides from SARS-CoV-2 membrane, nucleocapsid and spike protein to the time points tested. This is in line with increasing central memory and effector memory cell counts in the patient’s blood from day +29 to +44, especially in the CD3+ CD8+ T cell compartment. Additionally, this specific T-cell dependent immunity appeared to be long lasting as reactive T cells persisted at day+174.
The next finding was the detection of anti-SARS-CoV-2 type IgA and IgG antibodies in the patient’s serum at quite remarkable levels (Fig. 2 c-d). Qualitative anti-SARS-CoV-2 type IgG antibody detection was in parallel conducted in our virology department and remained positive even on day +174 (Table 1, Method: ELISA, Euroimmun, Lübeck, Germany). This is notable regarding pre-existing deficiency of CD4+ T cells and reduced IgA und IgM levels due to induction chemotherapy long before SARS-CoV-2 diagnosis. It reflects that not the absolute CD4+ T cells values, but their capacity to get activated and to differentiate into memory CD4+ T cells, could be crucial for completion of effective immunological response to SARS-CoV-2.
After re-introduction of lenalidomide, the activation status and distribution of cell populations remained unchanged despite an absolute decrease in lymphocyte subpopulations. In addition, specific IgG antibody levels and anti-SARS-CoV-2 reactive T-cells were also not affected by lenalidomide re-introduction, indicating persisting immunity despite the known immune modifying effects of this drug, at least in a 6 month view.
Furthermore, at every time point after day +11 the patient was tested for SARS-CoV-2, and the results remained negative (data not shown).