Is Aflatoxin B1 A Biomarker for Pathogenic Potential of Aspergillus flavus

Given the opportunity and the host immune status, Aspergillus flavus can produce aspergillosis affecting various body organs, while its toxin, Aflatoxin B1 (AFB1) has been implicated as a carcinogen in hepatocellular carcinoma. Based on previous findings, A. flavus can be divided into two groups, (i) isolates that can synthesize AFB1, and (ii) isolates unable to produce AFB1. The aim of this study was to assess whether AFB1 can be used as a marker to differentiate clinical and non-clinical isolates of A. flavus. Representative clinical isolates were obtained from patients while non-clinical isolates were obtained from the environment. Isolates were identified as A. flavus using selective media. AFB1 production was assessed through cultural assays and genes for aflatoxin production, aflR and aflS, were amplified using PCR. Conditioned media and methanol extract of A. flavus isolates were prepared and tested for AFB1 presence using Liquid Chromatography-Mass Spectrometry (LC-MS). Additionally, conditioned media and extract were tested for their cytotoxic effects on primary human brain microvascular endothelial cells (HBMEC) and immortalized human heptaoma cells (Huh7). Both clinical and non-clinical isolates of A.flavus exhibited aflatoxin production, albeit some clinical isolates produced excessive AFB1 (up to 15785 ng/mL). Importantly, A. flavus isolates produced higher levels of AFB1, exhibited increased host cell cytotoxicity, whereas strains exhibiting negligible amount of aflatoxin exhibited minimal cytotoxic effects suggesting AFB1 as a marker for pathogenic potential of A. flavus. The ability of aflatoxigenic A. flavus to produce host cell death in primary cells raises additional concern for patients suffering from A. flavus infection.