Diffuse large B-cell lymphoma remains the most frequent aggressive lymphoma worldwide, yet HIV-associated DLBCL presents distinct biological complexities that continue to challenge clinicians. Historically, researchers evaluated lymphomas through bulk genetic sequencing or standard immunohistochemistry, missing spatial cellular relationships. However, modern multiplex imaging and transcriptomics demonstrate that systemic immunodeficiency markedly remodels the surrounding tumor ecosystem. Consequently, clinicians must recognize how viral infection and antiretroviral therapy exposure fundamentally reshape tissue architecture, subclonal evolution, and immune escape mechanisms. Understanding these spatial networks offers pivotal insights for tailoring next-generation immunotherapeutic interventions.

Architectural Shifts in HIV-associated DLBCL Microenvironments

To decode tissue ecology, investigators applied imaging mass cytometry and spatial transcriptomics to pre-treatment diffuse large B-cell lymphoma biopsies across different immune backgrounds. Multiplex spatial analyses revealed that immune geography directly correlates with clinical outcomes. Specifically, researchers identified a distinct tumor-immune hot neighborhood in patients with HIV-associated disease. Although robust immune infiltration typically confers an antitumor advantage, this dense cellular niche unexpectedly correlated with inferior overall survival. Patients harboring this microenvironmental signature faced a significant hazard ratio of 3.16. Therefore, localized suppression within cellular neighborhoods fundamentally alters antitumor competence. Rather than signaling effective immune surveillance, this dense infiltration reflects severe functional exhaustion. Furthermore, these spatial associations illustrate that the qualitative composition of the microenvironment dictates prognosis far more than leukocyte abundance alone. By mapping cellular phenotypes across spatial coordinates, clinicians gain critical awareness regarding localized immune dysfunction that conventional histologic grading fails to capture.

Impact of Antiretroviral Therapy on Macrophage Infiltration

In addition to viral infection, prior exposure to antiretroviral therapy profoundly influences cellular composition within lymphomatous lymph nodes. Specifically, tumors arising in individuals with antiretroviral experience demonstrated significantly greater macrophage recruitment compared to antiretroviral-naïve counterparts. Spatial transcriptomic profiling confirmed extensive enrichment for pro-tumoral M2 macrophage markers, such as CD163, MRC1, and MARCO. Moreover, these myeloid cells actively co-expressed immune checkpoint transcripts, notably PDCD1 and CD274. Consequently, prolonged viral suppression and partial immune reconstitution induce an actively suppressive myeloid landscape rather than restorative antitumor immunity. These macrophages physically surround neoplastic B cells and prevent cytotoxic destruction. Furthermore, chronic antigenic stimulation alongside persistent inflammatory signaling recruits immature myeloid precursors that differentiate into tolerogenic effectors. As a result, the microenvironment in antiretroviral-experienced patients fosters an immunosuppressive barrier that shields lymphoma clones from host T-cell surveillance, highlighting myeloid reprogramming as a therapeutic target.

Divergent Epigenetic Niches and Polycomb Complex Regulators

Beyond extrinsic immune cells, tumor-intrinsic epigenetic networks exhibit distinct patterns that segregate according to viral status. Unsupervised clustering identified seventeen shared subclonal spatial niches within the lymphoma architecture, demonstrating marked intracohort heterogeneity. Interestingly, tumors from individuals with HIV displayed pronounced dysregulation of Polycomb Repressive Complex 1 components, particularly the oncogenic regulator BMI1. In contrast, lymphomas from HIV-negative patients exhibited predominant enrichment for Polycomb Repressive Complex 2 genes, notably the methyltransferase EZH2. Because Polycomb complexes govern stemness, cellular differentiation, and chromatin repression, these divergent epigenetic signatures reveal distinct pathways of lymphomagenesis. Specifically, BMI1 pathway activation in HIV-positive tumors promotes aggressive subclonal survival and sustained self-renewal despite host immunological disruptions. Conversely, EZH2-driven silencing reflects canonical epigenetic remodeling common to classic germinal center lymphomagenesis. Therefore, the degree of underlying immune dysregulation directly selects for unique subclonal survival mechanisms, providing rational targets for customized epigenetic therapies.

Pseudotime Trajectories and Immune Checkpoint Upregulation

Computational pseudotime analysis offers dynamic insights into how lymphomas evolve along continuum transcriptional states. Trajectory modeling positioned antiretroviral-naïve, antiretroviral-experienced, and HIV-negative tumors along progressively later transcriptional stages. This biological ordering demonstrates that immune reconstitution drives evolutionary progression toward mature immune escape. For example, CD47 expression consistently increased along pseudotime in antiretroviral-experienced tumors, whereas it progressively decreased in HIV-negative cohorts. Neoplastic cells upregulate this antiphagocytic signal to evade clearance by surrounding macrophages. In contrast, HIV-negative tumors selectively lost CD58 expression to evade cytotoxic recognition, a mechanism absent in HIV-positive cohorts. Additionally, paired whole exome sequencing revealed that tumors with high mutational burdens transitioned from proliferative states into immune-engaged microenvironments. Conversely, low-burden lymphomas accumulated dense extracellular matrix signatures and myeloid programs, yielding a heavily fibrotic architecture. Consequently, mutational burden directly dictates whether the tumor microenvironment develops an inflamed phenotype or a desmoplastic stromal barrier.

Therapeutic Opportunities in HIV-associated DLBCL

These biological discoveries carry immediate and actionable implications for future oncologic treatment protocols. Historically, clinical trial protocols systematically excluded people living with human immunodeficiency virus due to concerns over drug interactions or heightened toxicity. However, these spatial findings establish that antiretroviral-experienced tumors harbor a profoundly immunosuppressive, checkpoint-enriched microenvironment. Because these malignancies exhibit prominent PD-1, PD-L1, and CD47 axes, they represent ideal candidates for targeted immune checkpoint blockade and anti-CD47 macrophage phagocytosis therapies. Furthermore, targeting Polycomb Repressive Complex 1 using novel small-molecule inhibitors could disrupt subclonal propagation in virus-associated cohorts. Combining macrophage-reprogramming antibodies with established chemoimmunotherapy regimens could overcome microenvironmental resistance mechanisms. In addition, recognizing whether a patient presents as treatment-naïve or antiretroviral-experienced helps oncologists anticipate tumor-immune interactions. Ultimately, integrating spatial biology into clinical care paves the way toward equitable precision medicine, ensuring vulnerable patient populations access modern targeted therapeutics.

How does antiretroviral therapy alter the lymphoma microenvironment in HIV-positive patients?

Antiretroviral therapy substantially remodels the lymphoma microenvironment by driving marked myeloid infiltration and phenotypic polarization. Rather than generating effective antitumor immune responses, treated individuals develop dense infiltrates of M2 macrophages expressing CD163, MRC1, and MARCO. Furthermore, these cells display high levels of checkpoint markers including PD-1 and PD-L1. Consequently, partial immune reconstitution under antiretroviral therapy fosters an immunosuppressive tissue landscape that protects malignant B cells from cytotoxic destruction.

Why is CD47 upregulation significant in antiretroviral-experienced diffuse large B-cell lymphoma?

Neoplastic cells express CD47 as a potent antiphagocytic "do not eat me" signal that interacts with SIRP-alpha receptors on surrounding macrophages. In antiretroviral-experienced lymphoma tissues, CD47 expression rises progressively across developmental pseudotime states, directly counteracting the elevated local macrophage density. Consequently, malignant clones evade myeloid phagocytosis despite abundant macrophage infiltration. This upregulation highlights CD47 pathway inhibition as a highly promising therapeutic strategy to restore macrophage-mediated antitumor clearance in this specific patient cohort.

What distinct epigenetic mechanisms differentiate HIV-positive from HIV-negative lymphomas?

Spatial transcriptomic clustering reveals divergent chromatin-modifying dependencies between these patient populations. Specifically, HIV-associated lymphomas exhibit significant dysregulation of Polycomb Repressive Complex 1, driven by the oncogenic transcription factor BMI1, promoting subclonal renewal and survival. In contrast, lymphomas arising in immunocompetent, HIV-negative individuals demonstrate enriched Polycomb Repressive Complex 2 signaling, primarily governed by the methyltransferase EZH2. Therefore, clinicians and translational researchers must consider distinct epigenetic inhibitors tailored specifically to the patient's underlying immune status.

Disclaimer: This content is for informational and educational purposes only. It is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Refer to the latest local and national guidelines for clinical practice.

References

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