In vitro and in vivo effect of PD-1/PD-L1 blockade on microglia/macrophage activation and T cell subset balance in cryptococcal meningitis

Utility of Cerebrospinal Fluid Protein Levels as a Potential Predictive Biomarker of Disease Severity in HIV-Associated Cryptococcal Meningitis

Background

Cerebrospinal fluid (CSF) protein levels exhibit high variability in HIV-associated cryptococcal meningitis from being normal to markedly elevated. However, the clinical implications of CSF protein levels in cryptococcal meningitis remain unclear.

Methods

We analysed data from 890 adults with HIV-associated cryptococcal meningitis randomized into two clinical trials in Uganda between 2015 and 2021. CSF protein was grouped into ≥100 mg/dL (n=249) and <100 mg/dL (n=641). We described baseline clinical variables and mortality by CSF protein levels.

Results

Approximately one-third of individuals had a baseline CSF protein ≥100 mg/dL. Those with CSF protein ≥100 mg/dL were more likely to present with Glasgow coma scale scores <15 (P<0.01), self-reported seizures at baseline (P=0.02), higher CD4 T-cells (p<0.001), and higher CSF white cells (p<0.001). Moreover, those with a baseline CSF protein ≥100 mg/dL also had a lower baseline CSF fungal burden (p<0.001) and a higher percentage of sterile CSF cultures at day 14 (p=0.02). Individuals with CSF protein ≥100 mg/dL demonstrated a more pronounced immune response consisting of upregulation of immune effector molecules pro-inflammatory cytokines, type-1 T-helper cell cytokines, type-3 chemokines, and immune-exhaustion marker (p<0.05). 18-week mortality risk in individuals with a CSF protein <100 mg/dL was 34% higher, (unadjusted Hazard Ratio 1.34; 95% CI, 1.05 to 1.70; p=0.02) than those with ≥100 mg/dL.

Conclusion

In cryptococcal meningitis, individuals with CSF protein ≥100 mg/dL more frequently presented with seizures, altered mental status, immune activation, and favourable fungal outcomes. Baseline CSF protein levels may serve as a surrogate marker of immune activation and prognosis.

PD-L1 negatively regulates antifungal immunity by inhibiting neutrophil release from bone marrow

Programmed death ligand 1 (PD-L1) has been shown to be inducibly expressed on neutrophils to suppress host immunity during polymicrobial sepsis, virus and parasite infections. However, the role of PD-L1 on neutrophil-mediated antifungal immunity remains wholly unknown. Here, we show that the expression of PD-L1 on murine and human neutrophils was upregulated upon the engagement of C-type lectin receptor Dectin-1 with its ligand β-glucans, exposed on fungal pathogen Candida albicans yeast. Moreover, β-glucan stimulation induced PD-L1 translocation into nucleus to regulate the production of chemokines CXCL1 and CXCL2, which control neutrophil mobilization. Importantly, C. albicans infection-induced expression of PD-L1 leads to neutrophil accumulation in bone marrow, through mediating their autocrine secretion of CXCL1/2. Furthermore, neutrophil-specific deficiency of PD-L1 impaired CXCL1/2 secretion, which promoted neutrophil migration from bone marrow into the peripheral circulation, thereby conferring host resistance to C. albicans infection. Finally, either PD-L1 blockade or pharmacological inhibition of PD-L1 expression significantly increased neutrophil release from bone marrow to enhance host antifungal immunity. Our data together indicate that activation of Dectin-1/PD-L1 cascade by β-glucans inhibits neutrophil release from bone marrow reserve, contributing to the negative regulation of antifungal innate immunity, which functions as a potent immunotherapeutic target against life-threatening fungi infections.

The effect of PD-1 expression on tumor-associated macrophage in T cell lymphoma

PURPOSE

Our study aimed to explore the programmed death 1 (PD-1) expression on tumor-associated macrophage (TAM) in T cell non-Hodgkin lymphoma (T-NHL) and its relationship with lymphoma prognosis. The effect of PD-1 expression on the function of macrophages was also studied.

METHODS

Multispectral image quantitative analysis was applied for detecting PD-1 expression on macrophages in T cell lymphoma tissues. The Kaplan-Meier analysis was performed to evaluate the value of PD-1 expression of TAM in predicting the overall survival of T-NHL. PD-1 overexpression THP-1-derived macrophage was constructed and was cocultured with Jurkat cells to explore the effect of PD-1 on macrophage function.

RESULTS

In 17 T cell lymphoma cases, the 1-year overall survival rate was significantly lower in patients with higher PD-1 expression on TAMs (0.25 vs 0.86, p < 0.05). After co-cultured with Jurkat cells, classically activated (M1)-related markers on PD-1 overexpressed macrophages were significantly lower than those on controls, while the expressions of alternatively activated (M2) related markers were similar. The PD-1 overexpressed macrophages showed inhibited phagocytosis (4.42% vs 40.7%, p < 0.001) and increased IL-10 secretion (144.48 pg/ml vs 32.32 pg/ml, p < 0.001).

CONCLUSION

High PD-1 expression on TAMs in T-NHL may predict poor prognosis. The PD-1 overexpression of macrophages significantly inhibited polarization of M1 macrophages and phagocytosis, and more IL-10 was excreted. These changes may enhance the pro-tumor effects of tumor microenvironment.

Landmark clinical observations and immunopathogenesis pathways linked to HIV and Cryptococcus fatal central nervous system co-infection

Cryptococcal meningitis remains one of the leading causes of death among HIV-infected adults in the fourth decade of HIV era in sub-Saharan Africa, contributing to 10%-20% of global HIV-related deaths. Despite widespread use and early induction of ART among HIV-infected adults, incidence of cryptococcosis remains significant in those with advanced HIV disease. Cryptococcus species that causes fatal infection follows systemic spread from initial environmental acquired infection in lungs to antigenaemia and fungaemia in circulation prior to establishment of often fatal disease, cryptococcal meningitis in the CNS. Cryptococcus person-to-person transmission is uncommon, and deaths related to blood infection without CNS involvement are rare. Keen to the persistent high mortality associated with HIV-cryptococcal meningitis, seizures are common among a third of the patients, altered mental status is frequent, anaemia is prevalent with ensuing brain hypoxia and at autopsy, brain fibrosis and infarction are evident. In addition, fungal burden is 3-to-4-fold higher in those with seizures. And high immune activation together with exacerbated inflammation and elevated PD-1/PD-L immune checkpoint expression is immunomodulated phenotypes elevated in CSF relative to blood. Lastly, though multiple Cryptococcus species cause disease in this setting, observations are mostly generalised to cryptococcal infection/meningitis or regional dominant species (C neoformans or gattii complex) that may limit our understanding of interspecies differences in infection, progression, treatment or recovery outcome. Together, these factors and underlying mechanisms are hypotheses generating for research to find targets to prevent infection or adequate therapy to prevent persistent high mortality with current optimal therapy.

The Emerging Role of Rab5 in Membrane Receptor Trafficking and Signaling Pathways

Ras analog in brain (Rab) proteins are small guanosine triphosphatases (GTPases) that belong to the Ras-like GTPase superfamily, and they can regulate vesicle trafficking. Rab proteins alternate between an activated (GTP-bound) state and an inactivated (GDP-bound) state. Early endosome marker Rab5 GTPase, a key member of the Rab family, plays a crucial role in endocytosis and membrane transport. The activated-state Rab5 recruits its effectors and regulates the internalization and trafficking of membrane receptors by regulating vesicle fusion and receptor sorting in the early endosomes. In this review, we summarize the role of small Rab GTPases Rab5 in membrane receptor trafficking and the activation of signaling pathways, such as Ras/MAPK and PI3K/Akt, which ultimately affect cell growth, apoptosis, tumorigenesis, and tumor development. This review may provide some insights for our future research and novel therapeutic targets for diseases.

Macrophages participate in the immunosuppression of condyloma acuminatum through the PD-1/PD-L1 signaling pathway

BACKGROUND

The aim of this study was to investigate whether macrophages can participate in the immunosuppression of condyloma acuminatum (CA) by expressing PD-1/PD-L1.

METHODS

The infiltration of macrophages and expression of programmed death-1 (PD-1) and PD-1 ligand 1 (PD-L1) on wart lesions and in normal skin tissues were detected by immunohistochemistry assay. The amounts of M1- and M2-type macrophages derived from THP-1 cells were measured by flow cytometry. The expression of cytokines on macrophages was examined by using enzyme-linked immunosorbent assay (ELISA). The protein expression of PD-1 and PD-L1 on macrophages was detected by western blotting.

RESULTS

The macrophages were significantly increased, while PD-1 and PD-L1 were highly expressed on wart lesions compared to normal controls. More M2-like macrophages than M1-type macrophages were present on wart lesions. The M2-like macrophages in the CA groups showed high expression of interleukin-10 (IL-10), transforming growth factor (TGF-β), PD-1, and PD-L1 compared to normal controls.

CONCLUSION

Macrophages participate in the immunosuppression of CA by expressing PD-1/PD-L1.

Decreased PD-1 expression on circulating CD4+T cell and PD-L1 expression on myeloid dendritic cell correlate with clinical manifestations in systemic juvenile idiopathic arthritis

OBJECTIVES

Programmed cell death-1 (PD-1) and its ligand (PD-L1) mediate negative signal in autoimmune diseases. While little is known about its role in juvenile idiopathic arthritis (JIA). The study aimed to reveal the circulating cell profile and the relative PD-1/PD-L1 expression of JIA subsets, elucidating their underlying immunomodulatory mechanisms.

METHODS

We detected the circulating cells and the relative PD-1/PD-L1 signaling in 101 JIA patients and 50 controls by flow cytometry and analyzed their association with disease activity and clinical manifestations.

RESULTS

Different from other JIA types, active systemic JIA (sJIA) patients had lower percentage and count of CD4⁺T cells and lower PD-1 expression on them compared with healthy controls (P<0.05), active polyarthritis (P<0.05) and enthesitis-related arthritis (ERA) patients (P<0.05). Also, they had higher percentage and count of myeloid dendritic cell (mDC) and lower PD-L1 expression on mDC compared with healthy controls (P<0.05). Both PD-1 on CD4⁺T cell and PD-L1 on mDC were negatively correlated with JADAS-27 in sJIA patients (P<0.05). In addition, PD-1 expression on CD4⁺T cell was negatively associated with the number of involved joints (P<0.05) and PD-L1 on mDC was lower in patients with fever (P<0.01), which could further divide patients into two groups of different manifestations.

CONCLUSIONS

Our finding displayed decreased CD4⁺T cell, increased mDC and reduced PD-1/PD-L1 signal in sJIA PBMC comparing with other JIA subsets, which might be helpful in JIA differential diagnosis and responsible for distinct clinical manifestations via different mechanisms.