The gene expression and proteomic profiling of Acanthamoeba isolates

The free-living protozoan Acanthamoeba can cause severe keratitis known as Acanthamoeba Keratitis (AK) and granulomatous amoebic encephalitis (GAE). The pathogenesis of Acanthamoeba includes intricate interactions between the organism and the host's immune system. The downstream analysis of a well-annotated genome assembly along with proteomic analysis can unravel several biological processes and aid in the identification of potential genes involved in pathogenicity.

Based on the next-generation sequencing data analysis, genes including lysophospholipase, phospholipase, S8/S53 peptidase, carboxylesterase, and mannose-binding protein were selected as probable pathogenic targets that were validated by conventional PCR in a total of 30 Acanthamoeba isolates. This was followed by real-time PCR for the evaluation of relative gene expression in the keratitis and amoebic encephalitis animal model induced using keratitis (CHA5), encephalitis (CHA24) and non-pathogenic environmental isolate (CHA36). In addition, liquid chromatography-mass spectrometry (LC-MS/MS) was performed for keratitis, encephalitis, and non-pathogenic environmental isolate before and after treatment with polyhexamethylene biguanide (PHMB).

The conventional PCR demonstrated the successful amplification of lysophospholipase, phospholipase, S8/S53 peptidase, carboxylesterase, and mannose-binding protein genes in clinical and environmental isolates. The expression analysis revealed phospholipase, lysophospholipase, and mannose-binding genes to be significantly upregulated in the keratitis isolate (CHA 5) during AK in the animal model. In the case of the amoebic encephalitis model, phospholipase, lysophospholipase, S8/S53 peptidase, and carboxylesterase were significantly upregulated in the encephalitis isolate compared to the keratitis isolate. The proteomic data revealed differential protein expression in pathogenic versus non-pathogenic isolates in the pre and post-treatment with PHMB.

The gene expression data suggests that lysophospholipase, phospholipase, S8/S53 peptidase, carboxylesterase, and mannose-binding protein (MBP) could play a role in the contact-dependent and independent mechanisms of Acanthamoeba pathogenesis. In addition, the proteomic profiling of the 3 isolates revealed differential protein expression crucial for parasite growth, survival, and virulence. Our results provide baseline data for selecting possible pathogenic targets that could be utilized for designing knockout experiments in the future.