Variable R1 region in varicella tester virus in fulminant type of acute retinal necrosis syndrome

Background/aims-Varicella tester virus (VZV) is a causative agent in acute retinal necrosis (ARN) syndrome. However, in spite of aggressive antiviral therapy, clinical characteristics among patients have varied. Different viral strains were examined to determine their respective role in producing clinical characteristics. The viral strains were also compared with those of previously reported ones. Methods-To differentiate VZV strains R1 and R5, variable regions of VZV were amplified by nested polymerase chain reaction (PCR) in 11 eyes of 10 patients. Sequence analysis was also performed. Results-Four cases had strains diverted only at the tip of the 3' end of the R1 variable region, similar to that of the H-N3 strain, which was previously reported. Conversely, other cases were diverted to other regions. Interestingly, some of the latter cases showed multiple PCR products in the R1 region that were generated by the truncation of either the 5' or 3' R1 region. Final visual acuities of these patients were less than 0.2. The former cases showed final visual acuities more than 0.4. Only two variants were from the R5 region. No patient had the same viral strain as the European Dumas type. Conclusion-These results showed that variable VZV strains participated in ARN. Using PCR of the R1 variable region, it was estimated that patients with a more fulminant type of ARN may have diverse viruses with extensive replication in the affected eyes.