Detection of HIV RNA after CAR T-Cell Therapy in a Relapsed/Refractory Diffuse Large B-Cell Lymphoma Patient: Possibility of False Positivity and Clinical Implications

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J Korean Cancer Assoc. 2025;.crt.2025.491

Publication date (electronic) : 2025 June 30

doi : https://doi.org/10.4143/crt.2025.491

Sang Eun Yoon¹, Kyungmin Huh², Tae Yeul Kim³, Hee Jae Huh³, Seok Jin Kim¹, Won Seog Kim^,1

¹Division of Hematology-Oncology, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea

²Division of Infectious Diseases, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea

³Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea

Correspondence: Won Seog Kim, Division of Hematology and Oncology, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-ro, Gangnam-gu, Seoul 06351, Korea Tel: 82-2-3410-6548 E-mail: wskimsmc@skku.edu

Received 2025 May 8; Accepted 2025 June 26.

Abstract

Introduction

Chimeric antigen receptor (CAR) T-cell therapy using lentiviral vectors has emerged as an effective treatment for relapsed or refractory B-cell lymphomas. Because lentiviral vectors contain genetic elements derived from human immunodeficiency virus (HIV), nucleic acid–based HIV assays may yield false-positive results after CAR T-cell therapy. However, this phenomenon remains underrecognized in routine clinical practice. We report a case of persistent HIV RNA positivity following lentiviral vector–based CAR T-cell therapy in a patient with relapsed/refractory diffuse large B-cell lymphoma (R/R DLBCL), highlighting the diagnostic challenges and clinical implications of assay cross-reactivity.

Case Report

A 64-year-old male patient presented with weight loss accompanied by night sweats and was diagnosed with stage IV diffuse large B-cell lymphoma, activated B-cell type, and double-expression disease after imaging and bone marrow evaluation. The patient underwent eight cycles of R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisolone) chemotherapy, achieving a complete response. However, 16 months later, the disease relapsed, and he subsequently received three cycles of R-ICE (rituximab, ifosfamide, carboplatin, and etoposide) chemotherapy followed by autologous stem cell transplantation. After 14 months of remission, the patient experienced disease relapse and was treated with tisagenlecleucel (tisa-cel, Kymriah) as the third-line treatment. Prior to CAR T-cell infusion, infectious disease screening, including HIV, hepatitis C virus, and hepatitis B virus, was all negative. Elecsys HIV Duo assay (Roche Diagnostics GmbH) was used for HIV screening. Four months after the tisa-cel infusion, disease progression was observed in the retroperitoneal mass and adrenal gland, necessitating additional novel CD20-targeted CAR T-cell therapy through a clinical trial (Fig. 1).

Fig. 1.

Clinical course and tumor progression sites after sequential therapies. ASCT, autologous stem cell transplantation; BM, bone marrow; CR, complete response; DLBCL, diffuse large B-cell lymphoma; PD, progressive disease; R-CHOP, rituximab, cyclophosphamide, doxorubicin, vincristine, prednisone; R-ICE, rituximab, ifosfamide, carboplatin, etoposide.

Repeated infectious disease screening was performed as part of the preparation for the subsequent CAR T-cell therapy (Table 1). HIV reverse transcription polymerase chain reaction was performed at this time in accordance with a study protocol; Roche Cobas HIV-1 assay (Roche Diagnostics GmbH), which targets both 5’ long terminal repeat (LTR) region and gag gene [1], reported the detection of HIV-1 RNA at 48 copies/mL (80 IU/mL). A follow-up test 7 days (62 copies/mL, 104 IU/mL) and 1 month later (22 copies/mL, 37 IU/mL) showed persistent but low-level HIV-1 RNA detection, prompting further investigation to determine whether this was a false-positive result or a true HIV infection. Stored samples were analyzed to trace the onset of HIV RNA positivity, including serum at the time of apheresis, Kymriah infusion bag-washed residual cells, and serial serum samples collected 1 month after tisa-cel infusion and at disease progression using Roche Cobas HIV-1 assay. Retrospective HIV RNA analysis demonstrated no HIV RNA detection in serum samples before CAR T-cell infusion but positive Roche Cobas HIV-1 assay in Kymriah infusion bag-washed residual cells and serial serum samples, suggesting a treatment-related emergence of detectable lentiviral RNA.

Table 1.

Longitudinal quantitative PCR analysis across different sample types and time points in HIV RNA detection in a patient receiving CAR T-cell therapy

To further distinguish between a false-positive result due to lentiviral vector cross-reactivity and actual HIV infection, additional testing was performed on serial serum samples currently collected at three different time points. Additional testing was performed using the Alinity m HIV-1 assay (Abbott Molecular) [2], which targets the 5′ LTR and pol gene, and the Abbott RealTime HIV-1 assay (Abbott Molecular) [3], which targets only the pol gene. According to analysis, the dual-target Alinity m HIV-1 assay showed HIV RNA positivity, similar to our hospital’s previous findings. However, the single-target Abbott RealTime HIV-1 assay was consistently negative in all samples. The patient’s serum acquired two weeks after the first HIV RNA false-positive result was also tested negative on western blot for HIV (Korea Disease Control Agency).

Discussion

This case highlights a critical issue in interpreting positive HIV RNA assays following CAR T-cell therapy [4,5], mainly when lentiviral vectors are used for transduction [6]. Persistent positive results in assays targeting 5’ LTR and/or gag gene suggest cross-reactivity with the lentiviral vector rather than actual HIV infection. The absence of HIV RNA detection before CAR T-cell infusion and its subsequent emergence post-treatment further support the hypothesis of vector-derived RNA detection. False-positive HIV RNA results in patients undergoing CAR T-cell therapy can lead to misdiagnosis, unnecessary anxiety, and potentially inappropriate treatment interventions. Our findings suggest clinicians should carefully interpret HIV RNA positivity in this setting and consider assay design (including or excluding 5’ LTR or gag gene targets), clinical context, and confirmatory testing to distinguish vector-related signals from actual infection. To our knowledge, while a previous report has documented false-positive HIV results following lentiviral vector-based CAR T-cell therapy [5], our case is among the first to demonstrate this phenomenon using comprehensive multi-assay comparison and residual vector analysis, and likely the first reported case in Korea. This case underscores the need for awareness of lentiviral vector-induced false-positive HIV RNA results in CAR T-cell recipients. Given the expected expanding use of CAR T-cell therapies in hematologic and oncologic malignancies, further studies are warranted to develop diagnostic algorithms that can effectively differentiate actual HIV infection from the false-positivity from treatment-related lentivirus in patients receiving gene-modified cellular therapies.

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