Cerebrospinal fluid soluble CD30 elevation despite suppressive antiretroviral therapy in individuals living with HIV-1

OBJECTIVES: The aim of this study was to assess soluble CD30 (sCD30), a protein that colocalises with HIV-1 RNA and DNA in lymphoid cells and tissues, in cerebrospinal fluid (CSF) as a marker of HIV-1 infection in the central nervous system (CNS). METHODS: This was a cross-sectional study using archived samples from two clinical cohorts. Soluble CD30 concentrations were measured in paired CSF and plasma from untreated viraemic individuals (n=52), individuals on suppressive antiretroviral therapy (ART) (n=33), HIV-1 controllers (n=10), participants with CSF HIV-1 ‘escape’ (n=11) and controls without HIV-1 infection (n=16). Nonparametric tests were used to compare levels across groups and evaluate correlations with HIV-1 RNA, CSF neurofilament light chain protein (NFL) and neopterin. RESULTS: Compared with controls (median 30 ng/mL, interquartile range [IRQ] 23–50), plasma sCD30 levels were elevated in viraemic participants (75 ng/mL, 52–116; P<0.001), but not in those on suppressive ART (38 ng/mL, 32–62). In contrast, CSF sCD30 levels were elevated in ART-suppressed individuals (34 ng/mL, 19–46; P=0.001) and in those with CSF ‘escape’ (33 ng/mL, 27–40; P=0.004) compared with controls (18 ng/mL, 11–23), but not in untreated viraemic individuals. No association was observed between CSF sCD30 and plasma HIV-1 RNA, concurrent or nadir CD4+ T cell count, duration of infection or plasma sCD30. CSF sCD30 correlated with CSF NFL (r=0.34, P=0.001). CONCLUSIONS: In contrast to plasma, sCD30 levels are elevated in the CSF of individuals with HIV-1 infection who are on suppressive ART. Elevated levels of sCD30 in the CSF may be an indicator of persistent CNS HIV-1 infection, although the mechanism underlying this elevation warrants further investigation.