Abstract
Purpose :
Tubercular Uveitis (TBU) is a significant cause of treatable blindness in many endemic areas. Diagnosing TBU is challenging due to its diverse clinical manifestations, which often resemble other forms of infectious and immune-mediated uveitis. This study aims to investigate the Mycobacterium tuberculosis specific CD4 expression using flow cytometry at baseline and after 6 months of treatment in patients with TBU, compared to those with non-tubercular uveitis (NTBU), pulmonary TB (PTB), and healthy controls (HC).
Methods :
Blood was collected at baseline without treatment and again after 6 months of treatment. 86 Participants were divided into four groups: G1 (TBU, n=25), G2 (NTBU, n=35), G3 (PTB, n=6), and G4 (HC, n=16). TBU was defined as patients with clinical features and positive IGRA test. CD4 T cells were identified by ex vivo stimulation with PPD and flow cytometric analysis of intracellular cytokines and surface markers. We compared the percentages of expression of TNF-α, IFN-γ, IL-2 and GM-CSF in the PPD specific CD4 T cells.
Results :
A total of 86 patients were analyzed. The mean age was 52.2 years (SD 15). The gender distribution showed a female predominance (56.1%). Uveitis types predominantly included posterior uveitis, followed by anterior. At baseline, 80 samples were analyzed (G1: 24, G2: 34, G3: 6, G4: 16). GM-CSF and IFN-γ expression showed no significant differences. However, PPD specific CD4 percentages in G1 differed significantly from G2 and 3 (p < 0.001 and p = 0.029, respectively) (Figure 1A). Significant TNF-α and IL-2 expression differences were observed between G1 and 2 (p = 0.04 and p = 0.029, respectively) (Figure 1B and C). The 6-month follow-up of G1 (n=16) and 2 (n=13) revealed significant differences in %CD4 (p<0.001), TNFa (p=0.005), and IL2 (p=0.032) expression (Figure 1D-F). However, no significant differences were found when comparing baseline and 6-month data within G1 and 2.
Conclusions :
Our study highlights the significance of analyzing the expression of TNF-α, IL-2, and CD4 cell percentage as possible biomarkers for differentiating TBU from uveitis of other etiologies. However, it's important to note that, despite their distinctive characteristics, these markers did not exhibit changes post-treatment. Therefore, at this stage, they cannot be considered reliable indicators of inflammation resolution in TBU.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.