In vitro immune responses of human PBMCs against Candida albicans reveals fungal and leucocyte phenotypes associated with fungal persistence

Nidia Alvarez-Rueda,Adel Touahri,Barbara Misme-Aucouturier,Patrice Le Pape,Célia Rouges,Marjorie Albassier

doi:10.1038/s41598-020-63344-6

Abstract

Although there is a growing understanding of immunity against Candida albicans, efforts need to be pursued in order to decipher the cellular mechanisms leading to an uncontrolled immune response that eventually oppose disease eradication. We describe here significant intra- and inter-subject variations in immune response patterns of major human leucocyte subsets following an in vitro challenge with C. albicans clinical isolates. We also observed that there are Candida isolate-dependent changes in leucocyte phenotypes. Through a combination of multiple fungal growth and flow cytometric measurements, coupled to the tSNE algorithm, we showed that significant proliferation differences exist among C. albicans isolates, leading to the calculation of a strain specific persistent index. Despite substantial inter-subject differences in T cells and stability of myeloid cells at baseline, our experimental approach highlights substantial immune cell composition changes and cytokine secretion profiles after C. albicans challenge. The significant secretion of IL-17 by CD66+ cells, IFN-γ and IL-10 by CD4+ T cells 2 days after C. albicans challenge was associated with fungal control. Fungal persistence was associated with delayed secretion of IFN-γ, IL-17, IL-4, TNF-α and IL-10 by myeloid cells and IL-4 and TNF-α secretion by CD4+ and CD8+ T cells. Overall, this experimental and analytical approach is available for the monitoring of such fungal and human immune responses.

Highlights

There is a growing understanding of immunity against Candida albicans, efforts need to be pursued in order to decipher the cellular mechanisms leading to an uncontrolled immune response that eventually oppose disease eradication
Peripheral leucocyte cells from 16 healthy volunteers were challenged by C. albicans after fresh leucocyte fraction separation by gradient centrifugation
The variation of immune phenotypes according to the intra- and inter-subject differences was followed by flow cytometry over a 3-month period

Summary

Introduction

There is a growing understanding of immunity against Candida albicans, efforts need to be pursued in order to decipher the cellular mechanisms leading to an uncontrolled immune response that eventually oppose disease eradication. Efforts need to be pursued in order to decipher the cellular mechanisms leading to an uncontrolled immune response that eventually oppose disease eradication The capture of these dynamic and complex interactions strongly depends on the study design (cell line types, single vs multicellular models, Candida species and time interaction). Due to the natural individual variation of immune responses that could influence the fitness signatures in humans, we focused our analysis on a pilot prospective study including 16 healthy subjects to investigate the intra- and inter-variability of immune responses and fungal proliferation For this purpose, immune responses from 16 healthy subjects were evaluated 2, 4, and 6 days after in vitro challenge by three different C. albicans clinical isolates to examine immune cell markers (CD3, CD4 and CD8 T lymphocytes and CD66 and CD14 myeloid cells) and cytokine secretion profiles (IFNγ, IL-17, IL-4, TNF-α and IL-10) by flow cytometry. We provide raw components to infer Candida fitness in interactions with the major innate and adaptive human immune cells

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