Blocking the CTLA-4 and PD-1 pathways during pulmonary paracoccidioidomycosis improves immunity, reduces disease severity, and increases the survival of infected mice

Immune Phenotypes in Patients With Invasive Mould Infection Support the Use of PD-1 Inhibition as Potential Treatment Option

BACKGROUND

Invasive mould infections (IMI) cause substantial morbidity and mortality in populations at risk. Novel treatment approaches are urgently needed. Targeting immune checkpoints may reverse hyporesponsiveness of the innate and adaptive immune systems.

METHODS

In this prospective, observational study, we investigated immune checkpoint expression levels on immune cells in patients with invasive aspergillosis (IA; n = 25) and mucormycosis (MU; n = 7). Healthy controls (HC; n = 5) and patients with matched haematological diseases but without IMI served as control populations (CP; n = 10). Multicolour flow cytometry analysis was used to compare immune cell subsets and the expression of immune-regulatory molecules in peripheral blood mononuclear cells (PBMCs).

RESULTS

Lymphocyte subsets and immune phenotypes in PBMCs were similar between patients with IMI and haematological CP, except for regulatory T cells, which were increased in PBMCs of patients with IA and MU compared to HCs. In IA and MU, PBMCs showed increased expression of immune checkpoint molecules compared to healthy controls and matched haematological CP, with this effect being more pronounced in IA than in MU. We found heterogeneous, disease-, molecule-, and patient-specific expression patterns of immune checkpoint molecules. For example, PD-1 expression was highest in MU PBMCs, followed by IA PBMCs, while HC PBMCs showed lower expression levels. Overall mortality in our patient population was 44.0% (IPA) and 80.0% (MU).

CONCLUSIONS

We report an immune phenotype consistent with T-cell exhaustion in IMI, indicating potential contributions from haematological treatment, underlying disease, and infection. However, the primary underlying cause remains unclear and requires further investigation. A marker that was notably higher in IMI patients was PD-1, and treatment approaches specifically targeting this molecule may be promising.

Effects of combined cytotoxic T-lymphocyte antigen 4 and programed death 1 ligand-receptor blockade on interferon-gamma production in bovine leukemia virus-infected cattle

Background and Aim

In chronic viral infections, cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) and programmed death ligand 1 (PD-L1) significantly suppress immune responses. The CTLA-4 receptor abundance in regulatory T cells showed a positive association with viral load and a negative association with interferon-gamma (IFN-γ) production in bovine leukemia virus (BLV)-infected cattle. Blocking this receptor boosted IFN-γ production, recovering immune response against this illness. In human cancer patients, not everyone responded positively to non-immunotherapy using CTLA-4 receptor antibodies. The present study analyzed the synergistic effects of CTLA-4 and PD-L1 receptor blockade on IFN-γ production in BLV+ cattle in vitro.

Materials and Methods

The genes for bovine CTLA-4 and PD-L1 were artificially produced. The amino acid sequences of the extracellular receptor domains were sourced from the National Center for Biotechnology Information PubMed database. The western blotting and liquid chromatography with tandem mass spectrometry (LC-MS/MS) techniques were employed for the characterization of recombinant CTLA-4 (rCTLA-4) and recombinant PD-L1 (rPD-L1) proteins. The immunoinhibitory effects of recombinant proteins in Staphylococcus enterotoxin B (SEB)-stimulated cattle peripheral blood mononuclear cells (PBMCs) were investigated. Enzyme-linked immunosorbent assay (ELISA) was used to analyze monoclonal antibodies against rCTLA-4 and rPD-L1. Antibodies generated from peripheral blood mononuclear cells of healthy and BLV-seropositive cows were employed to evaluate their blocking capabilities.

Results

The resulting recombinant proteins specifically reacted with commercial homogeneous monoclonal antibodies (mAbs) using ELISA and anti-His-tag mAbs using western blotting. Analysis of the proteins using LC-MS/MS revealed correspondence with the sequences of rCTLA-4 and rPD-L1 located in the Mascot database. rCTLA-4 and rPD-L1 proteins inhibited IFN-γ production in bovine PBMCs of activated SEB. When PBMCs from cows were cultured with activated SEB containing rCTLA-4 and rPD-L1, the mAbs increased IFN-γ production in PBMCs. The combined cultivation of mAbs and PBMCs from BLV+ cattle enhanced IFN-γ production in the cells.

Conclusion

These findings suggest that the combined blockade of bovine CTLA-4 and PD-L1 receptors can be used as a therapy for bovine leukemia. However, it was shown that a single PBMC sample from a BLV-positive donor did not amplify the synergistic effect. Therefore, it is necessary to perform further studies on a larger population and assessing a wider range of cytokines.