Paediatric uveitis: more than meets the eye: Connecting inflammation in the eyes to the external environment, altered immunity and systemic disease

Abstract

In this thesis we studied paediatric uveitis in the context of systemic disease. We addressed the relevance of testing for nephrological inflammation in children with uveitis as TINU may lead to chronic kidney disease. We further saw that white matter abnormalities on brain MRI are common in paediatric uveitis although we do not yet know if and how these findings are related to the disease process of uveitis. We also found that HLA-DRB1*15:01 uveitis presents with a characteristic uveitis phenotype where signs of intermediate inflammation were predominant. Peripheral capillary leakage on fluorescein angiography, especially following a fern-like leakage pattern, was also characteristic in HLA-DRB1*15:01 positive uveitis. After a mean follow-up of 8.5 years 5.0% of the uveitis patients with the HLA-DRB1*15:01 allele developed MS. The HLADRB1*15:01 allele is also associated with MS, and our findings point towards a shared aetiology between MS and HLA-DRB1*15:01 positive uveitis. To further support this theory, we found that EBV may have a role as potential trigger for T cells and B cells in paediatric uveitis, similarly to in MS. We used an Infectious Disease Epitope Microarray to profile IgG antibody response in paired aqueous humour and serum samples from paediatric uveitis patients and controls. The microarray consisted of 3760 linear B cell epitopes from the Immune Epitope Database (IEDB) from 196 pathogens known to cause infection in humans. We included samples from 18 patients with paediatric uveitis and six age-matched controls. High IgG antibody response against different peptide sequences of the Epstein-Barr Virus Nuclear Antigen 1 (EBNA1) were found across the samples. Within the EBNA1 antigen, we identified a specific epitope: the Epstein-Barr Virus (EBV) (AA 402-406) epitope – against which patients with uveitis showed higher IgG titers in the aqueous humour than controls. More specifically, we noted that high EBNA1 IgG was associated with the presence of the HLA-DRB1*15:01 allele. We also examined the T cell response of patients with paediatric uveitis against the complete EBV EBNA1 antigen and to the EBV (AA 397-408) epitope we identified in our antibody study. We used an ELISPOT to measure the IFN-γ production in response to these two different antigen conditions. Overall, 82% of uveitis patients had a positive T cell response against the complete EBV EBNA1 pool. No statistically significant differences were seen in number of spot forming units per 106 cells against the EBV EBNA1 pool between HLA-DRB1*15:01 positive compared to HLA-DRB1*15:01 negative uveitis patients. A positive T cell response against the EBNA1 AA 397-408 epitope was measured in one uveitis patient; a homozygote HLA-DRB1*15:01 positive patient with intermediate uveitis. We determined the composition of the gut microbiome and ocular surface microbiome (OSM) in children with paediatric uveitis using 16S rRNA amplification and sequencing. The beta diversity of tear fluid from children with uveitis differed significantly from controls, indicating that the OSM is altered during ocular inflammation. In the faeces samples of uveitis patients, we found elevated levels of the pro-inflammatory species Escherichia–Shigella and Prevotella, although these increases did not reach statistical significance.