Impact of Candida albicans hyphal wall protein 1 (HWP1) genotype on biofilm production and fungal susceptibility to microglial cells

Abstract

The hyphal wall protein 1 (HWP1) gene of Candida albicans encodes for a fungal cell wall protein, required for hyphal development and yeast adhesion to epithelial cells; yet, its role in pathogenesis remains largely unknown. In the present study, we analyzed two C. albicans laboratory strains, the DAY286 (HWP1/HWP1) and the null mutant FJS24 (hwp1/hwp1) and six clinical isolates [3 harbouring the homozygous HWP1 gene (HWP1/HWP1) and 3 the heterologous gene (HWP1/hwp1)]. Biofilm production, fungal HWP1 mRNA levels and ultrastructural morphology were investigated; also, the susceptibility of these strains to microglial cells was evaluated, in terms of fungal damage and immune cell-mediated secretory response. When comparing the two laboratory strains, biofilm was produced to a similar extent independently on the genetic background, while the susceptibility to microglial cell-mediated damage was higher in the hwp1/hwp1 mutant than in the HWP1/HWP1 counterpart. Also, transmission electron microscopy revealed differences between the two in terms of abundance in surface adhesin-like structures, fungal cell wall shape and intracellular granules. When comparing the clinical isolates grouped according to their HWP1 genotype, reduced biofilm production and increased susceptibility to microglial cell-mediated damage occurred in the HWP1/hwp1 isolates with respect to the HWP1/HWP1 counterparts; furthermore, upon exposure to microglial cells, the HWP1/HWP1 isolates, but not the HWP1/hwp1 counterpart, showed enhanced HWP1 mRNA levels. Finally, both laboratory and clinical isolates exhibited reduced ability to stimulate TNFα and nitric oxide production by microglial cells in the case of heterozygous or null mutant HWP1 genotype. Overall, these data indicate that C. albicans HWP1 genotype influences pathogen morphological structure as well as its interaction with microglial cells, while fungal biofilm production results unaffected, thus arguing on its role as virulence factor that directly affects host mediated defences.

Antibiofilm and Antivirulence Activities of 6-Gingerol and 6-Shogaol Against Candida albicans Due to Hyphal Inhibition

“…The down-regulations of HWP1 and ECE1 by 6-gingerol or 6-shogaol are consistent with their observed effects on biofilm formation and hyphal development. HWP1 encodes a hyphal wall protein that is essential for hyphal development (Nobile et al, 2006b) and intercellular adherence (Orsi et al, 2014). Previously, we reported that camphor and fenchyl alcohol from cedar leaf oil (Manoharan et al, 2017b) and alizarin from the roots of the madder genus (Manoharan et al, 2017a) inhibit C. albicans biofilm formation by reducing hyphal formation by suppressing the gene expressions of HWP1 and ECE1 .…”

Role of microglia in fungal infections of the central nervous system

“…108 Biofilm formation seems to protect C. albicans from microglial damage impairing fungal cell phagocytosis, cytokine release, and NO production. 109 The b-glucans on the surface of C. albicans are detected by TLR-2 and 4, as well as Dectin-1 expressed on the surface of retinal and intraparenchymal microglia. [110][111][112] However, these carbohydrates may attenuate TLRmediated NF-kB activation, decreasing the capacity of microglia to release inflammatory cytokines in response to the pathogen.…”

Candida Biofilms: Development, Architecture, and Resistance

“…Proteomics analysis of biofilm matrix isolated using this optimized method revealed the presence of specific proteins (including glyceraldehyde 3-phosphate dehydrogenase and pyruvate kinase) in the biofilm matrix. Additional Candida genes implicated in biofilm formation include ACE2 ( 93 ), YWP1 ( 94 ), HWP1 ( 95 ), LL34 ( RIX7 ) ( 96 ), ALS3 ( 97 , 98 ), GAL10 ( 99 ), VPS1 ( 100 ), SUR7 ( 101 ), GUP1 ( 102 ), PEP12 ( 103 ), TPK1/2 ( 104 ), NRG1 (transcriptional repressor) and its target BRG1 (GATA family transcription factor) ( 105 ), UME6 (transcriptional regulator), HGC1 (a cyclin-related protein), SUN41 (a putative cell wall glycosidase), EFG1 ( 106 , 107 ), STV1 and VPH1 (Golgi/vacuolar subunits of vacuolar proton-translocating ATPase isoforms) ( 108 ), CEK1 (map kinase) ( 109 ), CDK8 ( 88 ), BCR1 ( 110 ), SPT20 ( 111 ), and SAC1 (PIP phosphatase) ( 112 ). In addition, quorum sensing molecules (such as 3R-hydroxy-tetradecaenoic acid [3R-HTDE, a beta-oxidation metabolite of endogenously present linoleic acid] [ 113 ]), farnesol ( 114 – 117 ), and cis -2-dodecenoic acid (BDSF) ( 118 ) and metabolic processes (e.g., carbohydrate assimilation, amino acid metabolism, and intracellular transport) ( 119 ) and glycolytic flux and hypoxia adaptation ( 120 ) have been suggested to play critical roles in Candida biofilm formation.…”