Recombinant interleukin-2 stimulates lymphocyte recovery in patients with severe COVID-19

A recently identified type of pneumonia, referred to as coronavirus disease 2019 (COVID-19), which is caused by severe acute respiratory syndrome coronavirus-2, has rapidly spread worldwide. Lymphopenia and a proinflammatory cytokine storm frequently occur in patients with severe COVID-19. However, to the best of our knowledge, no specific immunomodulatory therapy for COVID-19 has been reported to date. In the present retrospective case-control study, the potential therapeutic effect of recombinant human interleukin-2 (rIL-2) in patients with severe COVID-19 was demonstrated. A total of 59 patients with severe COVID-19 were admitted to the Union Hospital of Tongji Medical College (Wuhan, China) between 29th January 2020 and 29th February 2020 and were included in the present study. In total, 20 patients received subcutaneous injection of rIL-2 (1 million IU per day) for 7-10 days in addition to regular treatment and were classified as the rIL-2 group. Furthermore, 20 of the 39 patients receiving regular treatment, without the intervention of rIL-2, were matched as the control group. Patients in these two groups were subjected to propensity score matching in terms of clinical characteristics such as age, sex, symptoms, signs, laboratory data and comorbidities. Changes in the lymphocyte count, as well as IL-6 and C-reactive protein (CRP) levels, were analyzed at the time of admission and discharge and any differences between the rIL-2 and non-rIL-2 groups were determined. The results demonstrated an increase in the lymphocyte count and a decrease in CRP levels in the rIL-2 group compared with that in the non-rIL-2 group. The difference in the change of the lymphocyte count between the rIL-2 group and non-rIL-2 group was statistically significant (P<0.01). Although CRP levels were decreased to a greater extent in the rIL-2 group, the difference between the two groups was not statistically significant (P>0.05). Collectively, the present results suggested that administration of rIL-2 may be a prospective adjuvant therapy for patients with severe COVID-19 and its effects may be mediated by increasing lymphocyte numbers.