Differential Cytokine Responses in Hospitalized COVID-19 Patients Limit Efficacy of Remdesivir

Abstract

A significant proportion of COVID-19 patients will progress to critical illness requiring invasive mechanical ventilation. This accentuates the need for a therapy that can reduce the severity of COVID-19. Clinical trials have shown the effectiveness of remdesivir in shortening recovery time and decreasing progression to respiratory failure and mechanical ventilation. However, some studies have highlighted its lack of efficacy in patients on high-flow oxygen and mechanical ventilation. This study uncovers some underlying immune response differences between responders and non-responders to remdesivir treatment. Immunological analyses revealed an upregulation of tissue repair factors BDNF, PDGF-BB and PIGF-1, as well as an increase in ratio of Th2-associated cytokine IL-4 to Th1-associated cytokine IFN-γ. Serological profiling of IgG subclasses corroborated this observation, with significantly higher magnitude of increase in Th2-associated IgG2 and IgG4 responses. These findings help to identify the mechanisms of immune regulation accompanying successful remdesivir treatment in severe COVID-19 patients.

Keywords: COVID-19; T-cells; disease progression; remdesivir (GS-5734); tissue repair.

Figure 1

Concentrations of immune mediators in COVID-19 patients treated with remdesivir (RDV). Heatmap of immune mediator levels in plasma samples of COVID-19 patients are responders (do not progress to intubation, n = 21) or non-responders (progress to intubation, n = 6) to RDV treatment. Concentrations are measured before [median 9 and 7 days post-illness onset (PIO)] and one week (median 16 and 13 days PIO) after RDV treatment for responders and non-responders, respectively. Immune mediator levels in timepoint matched (MTP) plasmas samples from non-intubated (n = 17, median 10 and 16 days PIO) or intubated (n = 10, median 6 and 12 days PIO) COVID-19 patients were also quantified for controls. RDV-treated and control patients are indicated with + and -, respectively. Each color represents the relative concentration of a particular analyte (blue = low concentration; red = high concentration). Each row represents one patient. Patient samples with concentration out of measurement range are presented as the value of Limit of Quantification (LOQ).

Figure 2

COVID-19 patients responding to remdesivir (RDV) treatment show up-regulation of recovery-associated immune mediators. Growth factors brain-derived neurotropic factor (BDNF), placental growth factor (PIGF-1) and platelet-derived growth factor BB subunit (PDGF-BB) levels in plasma before and after RDV treatment in non-intubated responders (n = 21, median 9 and 16 days post-illness onset (PIO), respectively) and intubated non-responders (n = 6, median 7 and 13 days PIO, respectively), and matched timepoint 1 and 2 in non-RDV-treated non-intubated (n = 17, median 10 and 16 days PIO, respectively) and intubated (n = 10, median 6 and 12 days PIO, respectively) controls. Statistical analyses were performed with Wilcoxon matched-pairs signed rank test when comparing between timepoints, and Mann Whitney U test when comparing across groups (ns, not significant. *P < 0.05; **P < 0.01). Immune mediator levels for healthy controls (n=23) are indicated by the black dotted line. Patient samples with concentration out of measurement range are presented as the value of Limit of Quantification (LOQ).

Figure 3

COVID-19 patients responding to remdesivir (RDV) treatment show an increase in T_h2 to T_h1 cytokine ratio. Immune mediator levels in inactivated patient plasma was measured with 45-plex Luminex assay. (A) IL-4 to IFN-γ ratio of non-intubated responders and intubated non-responders before and one week after treatment with RDV. Statistical analysis was performed with Wilcoxon matched-pairs signed ranked test (ns, not significant; *P < 0.05). (B) T_h2-associated immune mediators IL-21 and (C) IL-6 levels in plasma before and after RDV treatment in responders (n = 21, median 9 and 16 days post-illness onset (PIO), respectively) and non-responders (n = 6, median 7 and 13 days PIO, respectively), and matched timepoint 1 and 2 in non-RDV-treated non-intubated (n = 17, median 10 and 16 days PIO, respectively) and intubated (n = 10, median 6 and 12 days post intubation, respectively) controls. Statistical analyses were performed with Wilcoxon matched-pairs signed rank test when comparing between timepoints, and Mann Whitney U test when comparing across groups (ns, not significant; *P < 0.05; **P < 0.01). Immune mediator levels for healthy controls (n=23) are indicated by the black dotted line. Patient samples with concentration out of measurement range are presented as the value of Limit of Quantification (LOQ). ns, not significant.

Figure 4

S protein IgG subclasses responses in non-intubated or intubated patients with or without remdesivir (RDV) treatment. (A) IgG1, IgG2, IgG3, and IgG4 responses were analysed by screening plasma samples of non-intubated COVID-19 patients with RDV (n = 21) or without RDV (n = 17) treatment, and (B) intubated COVID-19 patients with RDV (n = 6) or without RDV (n = 10) treatment at 1:100 dilution against cells expressing the full-length SARS-CoV-2 spike protein, with healthy donors screened in parallel (n = 22). The ratio of combined IgG2 and IgG4 to combined IgG1 and IgG3 response (IgG_2/4/IgG_1/3) in RDV-treated patients with or without intubation before and after treatment and also in non-RDV-treated patients at matched time point 1 and 2 were computed and the increase in the ratio from the first to the second time point was plotted. Statistical analyses were performed with Mann Whitney U test (*P < 0.05).