Thymoglobulin and Basiliximab Induction Dosing and Infectious Outcomes in Kidney Transplant Recipients: A Retrospective Analysis

Background: Induction immunosuppression with thymoglobulin (ATG) or basiliximab in kidney transplantation reduces acute rejection while modulating cytomegalovirus (CMV) and BK virus (BKV) infection risks. Factors such as induction dosing, advanced age, and mycophenolate mofetil (MMF) exposure may contribute to infectious complications. This study investigated the effects of ATG and basiliximab dosing, age ≥70, and MMF area under the curve (AUC) on infection outcomes. Methods: A retrospective cohort study of 296 kidney transplant recipients (266 ATG, 30 basiliximab; living/deceased donors) from 2017–2023, excluding 2020 due to COVID-19 disruptions, compared ATG (3–6 mg/kg) with basiliximab (20 mg, days 0 and 4) induction. Primary outcomes were CMV viremia (>1,000 IU/mL) and BKV infection (viremia or nephropathy) within 12 months. Secondary outcomes included ATG dosing (total and adjusted body weight), MMF AUC (target 30–60 mg h/L), and age ≥70 effects. High-risk (D+/R–) patients received valganciclovir prophylaxis. Wilcoxon rank-sum tests assessed differences (p<0.05). Results: Among 296 recipients (58% male, 68% White, mean age 53), CMV incidence was 18.6% (ATG) vs. 10.0% (basiliximab, p=0.24); BKV incidence was 13.6% vs. 10.0% (p=0.78). In ATG-treated patients aged ≥70 (n=19) vs. <70 (n=247), dosing was lower (median total dose 250 vs. 400 mg, p<0.0001; adjusted 3.0 vs. 4.8 mg/kg, p<0.0001), yet CMV rates were higher (31.6% vs. 15.4%, p=0.10), with similar BKV rates (15.8% vs. 13.8%, p=0.73). Overall, ATG dosing showed no association with CMV (p=0.26 total, p=0.11 adjusted) or BKV (p=0.10 total, p=0.67 adjusted). Initial MMF AUC showed no correlation with CMV (46 [38–58] vs. 52 [40–63] mg h/L, p=0.21) or BKV (44 [38–62] vs. 51 [40–63] mg h/L, p=0.34), although dose reductions were required >20% patients. Conclusion: ATG dosing variations did not influence CMV or BKV infection rates, nor did basiliximab significantly reduce infections vs. ATG. Elevated CMV risk in recipients aged ≥70, despite significantly lower ATG dose, suggests tailored, milder immunosuppression. Additional investigation of MMF dosing and corresponding MMF AUC is warranted to clarify their roles in infection risk stratification.