Hydroxychloroquine reduces T cells activation recall antigen responses

Abstract

Background: In the context of the current COVID-19 pandemic, there is still limited information about how people suffering from autoimmune diseases respond to the different COVID vaccines. The fact that they are taking an immunosuppressant or other drugs that aim to decrease the immune system activities, such as hydroxychloroquine (HCQ), could also impact their ability to respond to a COVID vaccine and vaccines in general.

Methods: Heathy donors were given 200mg of HCQ daily for 6-weeks to assess HCQs impact on the systemic T cells and humoral immune response. Peripheral blood mononuclear cells (PBMC) and plasma were obtained at baseline and 6-weeks after starting daily HCQ. Flow cytometry assays were designed to determine changes in T cell activation and T cell responses. Bead array multiplex were used to analyse antibodies and cytokine levels before and after HCQ intake.

Results: As anticipated, HCQ treatment decreased ex vivo T cell activation. We observed a decrease in CD4+CD161- expressing CCR5 (p = 0.015) and CD69 (p = 0.004) as well as in CD8+CCR5+ (p = 0.003), CD8+CD161+CCR5+ (p = 0.002) and CD8+CD161+CD95+ (p = 0.004). Additionally, HCQ decreased the proportion of Th17 expressing CD29 (p = 0.019), a subset associated with persistent inflammation. The proportion of T regulatory cells expressing the inhibitory molecule TIGIT was also reduced by HCQ (p = 0.003). As well, T cells from people on HCQ were less responsive to activation and cytokine production following stimulation with recall antigens and memory T cells were less likely to produce both IFNγ and TNFα following stimulation.

Conclusion: This study shows HCQ is associated with lower T cell activation and decreased T cell cytokine production. While this study was not performed with the intent of looking at COVID vaccine response, it does provide important information about the changes in immune response that may occur in patient taking HCQ as a treatment for their autoimmune disease.

Fig 1. A pair-wise comparison of the quantity of total IgG in the plasma at baseline (BL) and following for 6-weeks (Wk 6) of HCQ treatment.

A) Total IgG, B) select influenza specific isolates. Data was analyzed using Wilcoxon paired rank test and p values <0.05 were considered significant.

Fig 2. Effect of HCQ on T cell subsets from ex vivo PBMCs.

Data were analyzed using Wilcoxon paired rank test and p values <0.05 were considered significant. A) Changes in the proportion of CD4+ T cells in the fresh blood of participants treated with HCQ for 6-weeks. B) Changes in the proportion of CD8+ T cells in the fresh blood of participants treated with HCQ for 6-weeks. C) Changes in the proportion of T cell markers in the cryopreserved blood of participants treated with HCQ for 6-weeks. T regulatory cells (Tregs), Mucosal associated invariant T cells (MAIT). Data was analyzed using Wilcoxon paired rank test and p values <0.05 were considered significant.

Fig 3. Effect of HCQ on T cell activation markers post stimulation with 2μg/mL CEF (cytomegalovirus, Epstein Barr virus, and influenza virus) peptide pool.

A) Changes in CD4+ T cell markers following 12-hour stimulation. B) Changes in CD8+ T cell markers following 12-hour stimulation. C) Changes in CD4+ T cell markers following 7-day stimulation. D) Changes in CD8+ T cell markers following 7-day stimulation with CEF. Data was analyzed using Wilcoxon paired rank test and p values <0.05 were considered significant.

Fig 4. Effect of HCQ on cytokines after a 12-hour stimulation with 2μg/mL CEF (cytomegalovirus, Epstein Barr virus, and influenza virus) peptide pool.

A) Cytokine production determined by subtracting the amount of cytokine detected in the unstimulated condition from each of the stimulated conditions used in this study, B) Cytokine expression in unstimulated cells, C) cytokine expression following stimulation with the CEF peptide pool. D) Co-expression of multiple cytokines, p<0.05 (*), p<0.01 (**), pie colours represent different co-expression options, arc legend colours indicate the three cytokines assessed. Data was analyzed using Wilcoxon paired rank test and p values <0.05 were considered significant.