Introduction Current diagnostic technology for syphilis is over 100 years old and relies on detection of either reagins or treponemal antibodies. The development of new tests formulated on the basis of host cellular response may allow for improved diagnosis and clinical management. We aimed to pilot an evaluation of sera cytokine profiles as a means to better understand the pathogenesis of early infections.
Methods Participants included men who have sex with men and transgender women with and without early syphilis recruited at two sexual health clinics in Lima, Peru. Median fluorescence intensity (MFI) of 63 cytokines in serum collected on day of diagnosis was measured using Luminex (eBioscience). We calculated the relative change in MFI between those with active (RPR titer ≥1:32, TPPA+) versus no syphilis infection (TPPA-) and compared groups using a two-sample t-test.
Results Among 5 participants with active syphilis infections and 5 without there were 11 cytokines that differed between the groups with a p-value <0.1. The relative change (ratio) in MFI between syphilis infected and syphilis uninfected specimens was 1.535 for interleukin-7 (p = 0.012), 2.062 for inducible protein-10 (p = 0.054), 2.390 for leptin (p = 0.067), 1.960 for vascular endothelial growth factor (p = 0.067), 1.712 for granulocyte-macrophage colony-stimulating factor (p = 0.069), 1.947 for interleukin-10 (p = 0.070), 3.479 for vascular endothelial growth factor D (p = 0.074), 0.687 for Eotaxin (p = 0.082), 2.532 for macrophage inflammatory protein-1beta (p = 0.090), 1.493for monocyte chemotactic protein-3 (p = 0.093), and 2.526 for platelet-derived growth factor-BB (p = 0.097).
Conclusion Cytokines associated with cellular immune response might be useful in differentiating those needing treatment for active syphilis from those not requiring treatment. All of the cytokines presented here are higher in the active syphilis group versus syphilis uninfected except for Eotaxin. Larger sample size and longitudinal data are required to characterise cytokine profiles associated with treatment response and cure. Identifying cytokine changes may provide a new opportunity for diagnostic testing for syphilis infection.
Disclosure of interest statement None.
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