Correlation of Visual Outcomes in Patients with Acanthamoeba Keratitis Based on Genotypes and Presence of Viral Endosymbionts

Abstract

Purpose : This study aimed to characterize the genotype and presence of viral endosymbionts such as Giant Viruses (GV) including Pandoravirus (PV) and Mimivirus (MV) as well as Herpes Simplex Virus (HSV) 1 and 2 in clinical isolates of patients with microbiological and/or histological confirmed AK at the Bascom Palmer Eye Institute (BPEI), and to assess the relationship between endosymbionts and patients' visual outcomes.

Methods : 16 acanthamoeba isolates were collected from patients with AK and grown on non-nutrient agar. PCR and DNA sequencing were used to identify the Acanthamoeba species, genotype and screen for the presence of viral endosymbionts (GV and HSV). Retrospective chart review was performed to collect demographic information and best-corrected visual acuities (BCVA) at time of AK diagnosis and last follow up.

Results : A. castellanii was found in 9/16 (56%) of the isolates, followed by A. polyphaga in 1/16 (6%) and A. triangularis in 1/16 (6%). T4 genotype was found in 16/16 (100%) of the samples. GV were found in 11/15 (73%) of the samples, of which 8/15 (53%) were positive for PV, 3/15 (20%) for MV, and 1/12 (8%) for both. HSV was present in 5/12 (41%) of the isolates, of which 1/12 (8%) was positive for HSV-1, 3/12 (25%) for HSV-2, and 1/12 (8%) for both. In 3/11 (27%), both GV and HSV were present. In 4/16 (25%) of the isolates, no endosymbionts were found. 16 eyes of 16 patients were included, with ages ranging from 19 to 67 years (M=45.1, SD=16.7). 81% being female and 19% male. Patients with endosymbionts had an average BCVA of 1.74 and 0.82 LogMAR at diagnosis and final follow-up, respectively. Patients without endosymbionts had BCVA of 2.30 and 0.60 LogMAR at diagnosis and final follow-up. Patients with GV had an average BCVA of 1.68 and 0.87 LogMAR, and patients with HSV an average of 1.29 and 0.54 LogMAR. Patients with both GV and HSV had an average BCVA of 1.38 and 0.65 LogMAR.

Conclusions : The presence of viral endosymbionts in patients' isolates was associated with a worse final BCVA compared to those without endosymbionts. A. castellanii was the most frequently found species among the tested samples, and T4 genotype was identified in all samples. The number of samples with endosymbionts was greater than those without. Among the identified endosymbionts, GV was the most prevalent and was associated with lower final BCVA compared to those with HSV.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.