Expanded Viral Screening Could Cut Post‑Transplant Complications, New Data Suggest
Transplant teams are confronting a hidden threat: viruses that lie dormant until the immune system is suppressed. Recent studies on occult hepatitis B, human T‑cell lymphotropic virus (HTLV) and cytomegalovirus (CMV) reactivation provide data on the frequency of these infections and on challenges in their detection [1][2][3].
Key takeaways
- Occult hepatitis B infection is common in anti‑HBc‑only carriers, and immunosuppression dramatically raises the odds of detectable viral DNA [1].
- HTLV‑1/2 testing can be confounded by false‑positive results after high‑dose IVIG and false‑negative results in immunosuppressed patients [2].
- CMV reactivation continues to cause graft‑related morbidity even with pre‑emptive monitoring, and its timing with graft‑versus‑host disease (GVHD) remains complex [3].
Occult hepatitis B: a silent risk under immunosuppression
Patients who test positive only for hepatitis B core antibody (anti‑HBc) – without surface antigen or surface antibody – are often labeled “isolated anti‑HBc carriers.” In a cohort of more than a thousand such carriers, almost half had low‑level HBV DNA, indicating occult infection [1]. Immunosuppression was the strongest independent predictor of detectable HBV DNA, increasing the odds by more than fourteen‑fold; younger age and referral to gastroenterology or infectious‑disease specialists were also associated with positivity, while male sex was not an independent predictor [1]. The authors suggest that HBV DNA testing in anti‑HBc‑positive patients before immunosuppression aligns with existing guidelines, but note that their predictive model reflects a single‑institution experience and may not be universally applicable [1].
HTLV‑1/2: hidden pitfalls in low‑prevalence settings
Human T‑cell lymphotropic virus types 1 and 2 are rare in many parts of Europe. A retrospective review of 10,891 screening tests in southern Germany identified two major challenges: (1) immunosuppressed individuals may yield false‑negative results because of reduced antibody production, and (2) 74 % of high‑dose IVIG batches contained HTLV‑1/2 antibodies, leading to false‑positive screening results in recipients without underlying infection [2]. In four patients with neurological disease, elevated HTLV‑1/2‑specific antibody indices indicated intrathecal antibody production, suggesting true infection can involve the central nervous system [2].
CMV reactivation and GVHD: a bidirectional dance
In a single‑center cohort of allo‑HSCT recipients followed through day 100, CMV reactivation and acute GVHD showed a bidirectional temporal association: CMV reactivation could precede GVHD, and established GVHD could precede CMV reactivation [3]. Despite a standardized pre‑emptive strategy (viral load monitoring and treatment at predefined thresholds), CMV‑related complications such as end‑organ disease and delayed platelet engraftment requiring eltrombopag remained common [3]. Survival at day 100 did not differ markedly between patients with or without CMV reactivation or GVHD, but morbidity persisted [3]. The cohort did not receive letermovir, an antiviral now recommended for CMV prophylaxis in many transplant protocols; therefore, the study does not provide direct evidence on the impact of letermovir [3].
Uncertainties and the road ahead
The hepatitis B predictive model was derived from a single institution and requires external validation before broader policy use [1]. HTLV screening in low‑prevalence regions may generate false‑positive results when IVIG is used and false‑negative results in immunosuppressed patients, limiting its immediate utility [2]. For CMV, the relative benefits of universal prophylaxis versus targeted pre‑emptive therapy remain unresolved, and the optimal timing of antiviral initiation relative to GVHD onset has not been defined by the cited study [3].
Future multicenter research that harmonizes testing protocols, compares outcomes across different screening intensities, and incorporates immune‑reconstitution analyses will be needed to determine how best to mitigate viral complications after transplantation.
