ABSTRACT
Objective To study the immune intervention effect and mechanism of blockage of macrophage-mediated PD1 /PD-L1 pathways with functional PD-L1(programmed cell death ligand-1,PD-L1)monoclonal antibody upon tuberculosis(TB)relapse in mice. Methods Female C57BL/6 mice were infected by tail vein injection of 106CFU M. tuberculosis H37Rv to obtain active TB infection. Two weeks postinfection, the mice in different groups were administered isoniazid(10 mg/kg)(group ISO)and isoniazid combined with PD-L1 monoclonal antibody(50 μg/each)(group ISO+PD-L1)respectively,continued for four weeks to obtain latent infection. The subsequent relapse was monitored. Among the treatment groups,the TB relapse was induced by TNF-α antibody(50 ug/each)for four weeks from the beginning of latent stage. At each scheduled time point, bacterial loads and pathological changes in the lung, spleen and liver were quantitatively analyzed,thereby,the in vivo intervention effect of PD-L1 monoclonal antibody on tuberculosis recurrence in mice was revealed. The in vitro experiment was further explored whether knock-down the expression of PD-L1 on the infected macrophages could accerlate the macrophage apoptosis. Results The bacterial burden reached 3-4 Lg(CFU/mL),and granuloma lesions were extensive in the lung, spleen and liver in the all infected groups, which appeared as active TB stage at 2nd week postinfection. After treated,the bacterial burden of the lung,spleen and liver was decreased, and the pathological lesions alleviated in the group ISO and group ISO+PD-L1, compared with the model control group, showing significant differences, but there was no significant difference between the two treatment groups. However, compared with the group ISO,the group ISO+PD-L1 had a significantly lower bacterial load and milder pathological lesions during the relapse period. Futhermore, knock-down the expression of PD-L1 on macrophages with anti-PD-L1 or PD-L1-siRNA promoted apoptosis in macrophages. Conclusions Blockade of the PD1/PD-L1 pathway by PD-L1 functional antibody can inhibit TB relapse in mice,and knock-down the expression of PD-L1 on macrophages or PD1/PD-L1 pathway with functional antibody can promote apoptosis in macrophages,which together indicate that PD-L1 blockage can effectively promote isoniazid treatment of TB and remarkably inhibit the recurrence of TB in mice.
ABSTRACT
Objective To investigate the role of pathogenic Leptospira interrogans lipopolysaccha-ride (L-LPS) and outer membrane proteins (L-OMP) in the apoptosis of mouse macrophages (J774A.1) and their association with Fas/FasL pathway .Methods Phenol-water extraction and Triton X-114 phase separation were used to extract L-LPS and L-OMP from L.interrogans serogroup icterohaemorrhagiae serovar Lai strain Lai, respectively.Polymyxin B ( PMB) and protease K ( PK) were used to treat L-LPS and L-OMP, respectively.J774A.1 cells were stimulated by L.interrogans strain Lai with or without ultraviolet inactivation.In parallel, the cells were stimulated by extracted L-LPS and L-OMP with or without PMB and PK treatments .The apoptosis and necrosis of J 774 A.1 cells before and after treatment were detected by flow cytometry.The siRNAs were used to silence the expression of Fas or FasL gene in J 774A.1 cells and their inhibitory effects were further validated by using real-time fluorescent quantitative RT-PCR.Flow cytometry was used to detect the effects of L-LPS or L-OMP on the apoptosis of J774A.1 cells with Fas or FasL gene-knockdown .Results L.interrogans strain Lai with or without ultraviolet inactivation could cause similar early apoptosis rates (47.1%and 55.6%) and late apoptosis/necrosis rates (7.6%and 7.9%).The ear-ly apoptosis rates of 1×105 J774A.1 cells were 40.4%and 34.0%after the treatment with 100 ng of L-LPS and 100 μg of L-OMP for 4 h.The late apoptosis/necrosis rates of the cells were 7.5%and 6.9%upon the treatments with L-LPS and L-OMP, respectively.However, the apoptosis or necrosis of the cells was not ob-served when using L-LPS and L-OMP pre-treated by PMB and PK, respectively.Silenced expression of Fas or FasL gene reduced the L-LPS-induced J774A.1 cells apoptosis (P<0.05), while decreased early apopto-sis rate of J774A.1 cells mediated by L-OMP was only observed in Fas gene-knockdown cells (P<0.05). Conclusion Both L-LPS and L-OMP can cause the Fas/FasL-associated apoptosis of macrophages , which is beneficial for L.interrogans to establish the productive infection in hosts .