Higher HTLV-1c proviral loads are associated with blood stream infections in an Indigenous Australian population

Background: An association between blood stream infections (BSI) and HTLV-1 seropositivity in Indigenous Australians might result from HTLV-1 mediated inflammation and parasite coinfections that provide portals of entry for bacteria. Objectives: To determine whether BSI risk increases with HTLV-1c proviral load (PVL) and to identify the pathogens responsible in the context of HTLV-1 related conditions. Study design: Indigenous adults admitted to Alice Springs Hospital, central Australia, were recruited as cases or controls according to whether they had a BSI. Clinical data were extracted from case notes and the hospital pathology database. HTLV-1 serology and PVL assays were then performed and risk factors for BSI were determined for HTLV-1 infected subjects. Results: Risk factors were compared between 44 cases and 30 controls who were HTLV-1 Western blot positive. In a multivariable model, high HTLV-1c PVL was predictive of BSI during the study period (OR, 9.10; 95% CI, 2.40-34.4). Median (IQR) HTLV-1c PVL (copies per 100 PBL) was 39-fold higher for patients recording any BSI (0.116 (0.009, 0.277)) relative to those who had no BSI (0.003 (0.000, 0.067))(p = 0.0007). Mean (SD) PVL for subjects with no BSI (n = 27), 1 BSI (n = 37) and ≥2 BSI (n = 10) during the study period were 0.120 (0.301), 0.271 (0.622) and 0.500 (0.654) copies per 100 PBL, respectively (p = 0.0007). Five BSI were associated with possible complications of HTLV-1; strongyloidiasis (3), infective dermatitis (1), HTLV-1 associated bronchiectasis (1). Conclusions: Higher HTLV-1c PVL predicts BSI risk; however; most BSI were not associated with recognised complications of HTLV-1 infection.