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.

Objective TNF-α monoclonal antibody drugs are widely used to treat conditions such as rheumatic arthritis and ankylosing spondylitis. On the other hand, it is also a wide concern that the application of these drugs may increase the susceptibility of patients to infections such as tuberculosis and listeriosis. The aim of this study was to establish a mouse model of Listeria monocytogenes infection and to evaluate the effect of TNF-α monoclonal antibody on the host susceptibility to this infection. Methods Six SPF 14-week old female C57BL/6 mice and 12 SPF 14-week old female TNF-α humanized mice were injected with saline or adalimumab intravenously, and challenged with intraperitoneal injection of 104 CFU Listeria monocytogenes 24 h later. After one day or 4 days, the mice were sacrificed to examine the pathological lesions and the bacterial load in the spleen and liver. Results Four days after infection, the area of microabscess in the liver tissues was significantly increased in the adalimumab-treated group. The bacterial load in the spleen and liver tissues of the adalimumab-treated group was significantly higher than that of the C57BL/6 mouse control group and TNF-α humanized mouse control group (P ＜ 0. 05). However, the distribution of macrophages in the liver tissues and B cells in the spleen tissues were similar among groups. Conclusions TNF-α plays an important role in the host immune responses to Listeria monocytogenes infection. After the intervention with TNF-α monoclonal antibody, the progress of host disease is significantly exacerbated.

Objective This study was performed to establish and compare guinea pig models of tuberculosis using intranasal and aerosol infection routes at different doses.The overall goal was to provide a foundation for establishing a standardized guinea pig model of tuberculosis for the study of respiratory tract infection.Methods Twenty-four female guinea pigs were randomly divided into six groups of four guinea pigs each.They were then infected with two doses of Mycobacterium tuberculosis through either the aerosol route(groups A,B,and C)or intranasal route(groups D,E,and F).Aerosol infection groups consist of 3 groups:group A(Aerosol control group,uninfected control group),group B(Aerosol low-dose group,5×102 CFU),and group C(Aerosol high-dose group,5×103 CFU)Intranasal infection groups also consist of 3 groups:group D(Intranasal control group,uninfected control group),group E(Intranasal low-dose group,1×104 CFU),and group F(Intranasal high-dose group,5×104 CFU).The clinical manifestations of the guinea pigs were observed after infection.All guinea pigs were euthanized on day 14.Lung,spleen,and liver tissues were obtained for gross examination and histopathological analysis using hematoxylin-eosin staining to identify characteristic lesions associated with tuberculosis.Acid-fast staining was performed on in situ tissues and organs followed by bacterial culture to analyze the bacterial load.Results The guinea pigs in four infection groups(B,C,E,and F)exhibited macroscopic tuberculosis lesions in the lung,spleen,and liver.Histopathological examination revealed the presence of tuberculous granuloma lesions.Acid-fast staining and bacterial load analysis demonstrated that the bacteria were primarily localized in the lung tissue of aerosol-infected groups B and C,with a few also present in the spleen and liver,and the bacterial load was 104～105 CFU/mL.In intranasal infection groups E and F,bacteria were found in the lung,spleen,and liver with a similar bacterial load of 104～105 CFU/mL.There was no significant difference in lesion severity or bacterial load among groups B,C,E,and F;however,groups B,C,and F showed low standard deviations for both pathology and etiology.Conclusions A guinea pig model of acute tuberculosis was successfully established using two doses administered through distinct routes of infection.Pathological examination and pathogenic analysis demonstrated that an aerosol dose of 5×102 CFU of Mtb effectively established a homogeneous model of acute tuberculosis with good consistency among the animals.Additionally,intranasal infection with 5×104 CFU of Mtb produced a relatively uniform model of tuberculosis.Notably,however,aerosol infection at 5×102 CFU progressed to an acute tuberculosis model more rapidly than intranasal infection at 5×104 CFU.