Promising HIV Treatment, Reducing CD4+ T Cell Activation

A recent study in EBioMedicine analyzed the effects of nicotinamide mononucleotide (NMN) on CD4+ Thymus cells (T cells), which are T lymphocytes with CD4 receptors, and their role in immune activation during HIV-1 infection.

Background

In HIV-1 infections, approximately 30% of people undergoing combination antiretroviral therapy (cART) fail to adequately restore CD4+ T cells, increasing their susceptibility to immune deficiency syndromes (AIDS) and associated illnesses.

Research indicates that Vitamin D and Vitamin B3 (niacin), which are known to enhance Nicotinamide adenine dinucleotide (NAD) – crucial for cell metabolism and declining with age – are effective in immune modulation and supporting the restoration of CD4+ T cells. NMN, a direct NAD precursor without the adverse effects of other precursors, shows promise as a treatment for age-related conditions and for enhancing immune responses to infections and cancer.

Additional research is required because, despite the effectiveness of cART in reducing HIV-1 viremia, a significant number of individuals do not recover their CD4+ T cell count, leading to higher clinical risks. Understanding the role of NMN in modulating immune activation could provide new strategies for enhancing CD4+ T cell recovery and reducing disease progression in these patients.

About the study

In this study, researchers utilized peripheral blood from both HIV-1-uninfected donors and people living with HIV (PLWH) to isolate peripheral blood mononuclear cells (PBMCs). They employed Lymphoprep™ for density gradient centrifugation and various isolation techniques to minimize cell activation.

The isolated PBMCs and primary CD4+ T cells were cultured in R10 medium and modified for NMN treatment experiments. The HIV-1JRFL virus was propagated using the MOLT-4 CCR5+ cell line for virus preparation and infection, while the Human Embryonic Kidney 293 cells with a transfection receptor (HEK293T) cell line were used for packaging a non-replicable HIVJRFL-nLuc pseudovirus.

Researchers used a spinoculation technique to introduce these viruses into primary CD4+ T cells and the MOLT-4 CCR5+ cell line. They incorporated various control measures, such as mock infections and pre-treatment with Maraviroc, to ensure rigorous experimentation. Reactivation of the virus in ex vivo primary cell models and cell lines was achieved through specific treatments.

The MOLT-4 CCR5+ cells underwent cell transfection, followed by NMN treatment and RNA extraction. Mycoplasma-free cell lines played a crucial role in various assays, including anti-p24 Enzyme-Linked Immunosorbent Assay (ELISA) and luciferase assays, to measure NAD levels, cell viability, and pseudotyped virus responses. DNA and RNA extractions were conducted after NMN treatment or HIV-1 infection, with quantitative real-time PCR assays providing in-depth analysis.Flow cytometry was utilized for cell surface and intracellular staining.

The study also included experiments on humanized mice, with careful consideration of animal welfare and experimental conditions. The team monitored the mice’s plasma viral loads and cellular markers, collecting spleen samples for additional research. Advanced methods like Cytometry by Time-Of-Flight (CyTOF), Immunohistochemistry (IHC) staining, and RNA sequencing were used to assess the impact of NMN treatment at a molecular level. The research concluded with thorough statistical analyses and adherence to ethical standards, upholding research integrity.

Study results

In this study, researchers investigated the impact of NMN on HIV-1 infection in primary CD4+ T cells. They found that NMN treatment increased intracellular NAD levels and inhibited HIV-1 replication, leading to reduced viral p24 protein production in infected cells. This inhibition occurred without causing significant cell death, indicating that the reduced p24 production was not due to NMN’s toxicity.

Additionally, NMN did not markedly change the expression of the HIV-1 receptors CD4 and CCR5 in these cells. However, the study observed an increase in the frequency and mean fluorescence intensity (MFI) of C-X-C chemokine receptor type 4 (CXCR4) in NMN-treated CD4+ T cells. Despite these observations, NMN did not significantly impact the early stages of the HIV-1 life cycle, such as viral entry, reverse transcription, integration, and transcription. The researchers also explored the effects of NMN on CD25+ CD4+ T cells and HIV-1 replication.

They discovered that NMN treatment reduced the frequency of CD25+ and Human Leukocyte Antigen – DR Positive (HLA-DR+) cells, and significantly suppressed intracellular p24 in CD25+ CD4+ T cells. These findings suggested that NMN might influence the proliferation of infected cells. Furthermore, NMN was found to regulate CD25 expression in specific CD4+ T cell subsets and reduce the proliferation of primary p24+ CD4+T cells through CD25 downregulation. Transcriptomic analysis revealed that NMN treatment altered the expression of several genes associated with cell activation and proliferation.

In a humanized mouse model infected with HIV-1, the researchers found that combined NMN and cART treatment significantly enhanced CD4+ T cell reconstitution compared to cART alone. This combination also led to lower frequencies of apoptotic, hyperactivated, and CD25+ activated CD4+ T cells in the spleens of these mice. Moreover, the cART-plus-NMN group showed significantly lower frequencies of p24+ CD4+ T cells and proliferating ki67+ CD4+ T cells, indicating a suppressive effect on T cell hyperactivation and HIV-1 replication. These findings suggest that NMN, when combined with cART, has the potential to improve HIV-1 therapy by modulating CD4+ T cell activation and proliferation, thereby enhancing CD4+ T cell recovery and the overall effectiveness of the treatment.

For more information: Nicotinamide mononucleotide impacts HIV-1 infection by modulating immune activation in T lymphocytes and humanized mice. EBioMedicine.

doi: https://doi.org/10.1016/j.ebiom.2023.104877.