Contrasting immune fingerprints of chronic hepatitis B Virus infection in adults from South Africa and the United Kingdom

Background and aims: Hepatitis B Virus (HBV) interaction with the immune system is a key determinant of infection outcome. As the HBV field advances towards novel therapies (amongst which immunoregulatory drugs), enhanced risk stratification, and cancer prevention, there is a pressing need to better understand the immunological profiles that underlie diverse disease outcomes. Unfortunately, while accounting for almost 70% of all HBV infections worldwide, African populations have been neglected in clinical studies. We set out to compare circulating levels of ten cytokines, alongside host demographics and viral biomarkers, in cohorts based in the United Kingdom (UK) and South Africa (SA). Method: Serum samples were obtained from adult patients enrolled at Oxford University Hospitals, UK (n=60), and the Tygerberg Hospital in Cape Town, SA (n=32) with chronic HBV monoinfection (ethics ref.N17/01/013). HBsAg, HBeAg and HBV VL were estimated using standard clinical laboratory protocols, and HBcrAg were quantified using a chemiluminescent assay (Lumipulse G HBcrAg assay, Fujirebio). GM-CSF, IFNa2a, IL-2, IL-6, IL-8, IL-10, IL-21, IP-10, PD-1 and TNF-a were quantified using multiplex ELISA (K151AEL-1, MesoScaleDelivery). Patient meta-data were recorded at the time of recruitment, supported by Electronic Patient Records where available. For the analysis, using a euclidean distance, samples were hierarchically clustered based purely on standardised log-transformed cytokine measurements using Ward’s method for linkage. P values were calculated using Mann Witney test in Prism v. 8.0. Results: There were no significant differences between the two cohorts in terms of age (p=0.09), sex (p=0.07) or treatment (p= 0.61). HBV related biomarkers were comparable between the two cohorts, including HBcrAg (p=0.06), viral load (p > 0.99), HBeAg status (p=0.74) and ALT (p=0.81). However, the two cohorts presented distinct immune profiles. The SA cohort is dominated by a decreased level of IL-2, IL-10 and IFNa2a, while IP-10, PD-1 and IL-6 are increased (p<0.0001 forall except IFNa2a, p=0.09) compared to the UKcohort. These clusters did not co-vary with otherattributes of the patient, markers of infection or treatment (Figure 1). Of note, the SA cohort could be subdivided into three immune profiles, but without any significant differences. Conclusion: In this study, CHB patients from SA and the UK have distinct immune profiles, which are not clearly related to other host features or laboratory characteristics of infection. At present, it is unclear if these differences are attributable to host characteristics, viral genetics, exposure to treatment, or other environmental influences. Our data highlight the need for further populationbased studies to unravel the diversity in immune profiles. Enhanced understanding of the mechanisms that determine disease outcomes and treatment response are needed to support interventions that reduce the burden of liver disease associated with HBV.