Elevated circulating TLR4+ monocytes in patients with liver fluke Opisthorchis viverrini is associated with advanced periductal fibrosis.

INTRODUCTION: Opisthorchis viverrini (Ov) infection can lead to several disease manifestations of the bile duct including advanced periductal fibrosis (APF) and the most severe complication, cholangiocarcinoma (CCA). Monocytes migrate to the infection site and differentiate into tissue macrophages to express and release molecules such as cytokines, reactive oxygen species, and growth factors. TLR4+ monocytes are classified as having a pro-tumor phenotype and secrete tumor-promoting factors. The aim of this study is to investigate the role of monocytes in the pathogenesis of opisthorchiasis. METHODOLOGY: We used flow cytometry to measure the number of TLR4+ monocytes in the circulating blood of Ov infected patients with or without APF compared to healthy, non-Ov-infected controls. RESULTS: We found, for the first time, that patients with AFP have elevated numbers of circulating TLR4+ monocytes when compared to patients without fibrosis and healthy individuals. Intriguingly, when we measured ROS from these monocytes, we found increased ROS production in patients with APF. CONCLUSIONS: We propose that excessive production of ROS from these TLR4+ monocytes may lead to excessive injury of surrounding tissue and hence contribute to the pathological processes that lead to the development of advanced periductal fibrosis.

Neutrophils form extracellular traps in response to Opisthorchis viverrini crude antigens, which are elevated in neutrophils from opisthorchiasis patients with hepatobiliary abnormalities.

Opisthorchis viverrini (Ov) infection can cause several disease conditions of the bile duct including hepatobiliary abnormalities (HBAs) and the most severe, cholangiocarcinoma (CCA). Fibrosis occurs when tissues are damaged and normal wound-healing responses are dysregulated. Neutrophils are the first cells to migrate to an infection site to protect the host from intruding extracellular pathogens through a wide range of effector mechanisms such as phagocytosis, production of reactive oxygen species, proteases, or release of neutrophil extracellular traps (NETs). In this work, we used confocal microscopy to assess whether Ov crude antigens can cause release of NETs from neutrophils from Ov-free individuals. We demonstrated for the first time that these antigens could induce release of NETs ex vivo in a dose-dependent manner from neutrophils isolated from Ov-free individuals. Intriguingly, when we measured NETs from neutrophils isolated from Ov-infected patients, we found increased spontaneous production of NETs in patients with HBAs. Interestingly, exposure to Ov crude antigens lowered the level of NETs released by neutrophils from patients with active Ov infection regardless of HBA status. We propose that in the case of acute Ov infection, even when concentration of Ov antigens is relatively low, neutrophils can form NETs. However, when this infection becomes chronic, manifesting as a definite HBA, the levels of NET production are reduced when treated with Ov crude antigens. Excessive production of proinflammatory mediators from these NETs might have effects on the parasites, but may also lead to excessive injury of surrounding tissues resulting in HBAs and may lead eventually to the most severe complications such as CCA.

Phenotypic and functional changes of T cell subsets after CoronaVac vaccination.

BACKGROUND: The pandemic coronavirus disease 2019 (COVID-19) is a major global public health concern and several protective vaccines, or preventive/therapeutic approaches have been developed. Sinovac-CoronaVac, an inactivated whole virus vaccine, can protect against severe COVID-19 disease and hospitalization, but less is known whether it elicits long-term T cell responses and provides prolonged protection. METHODS: This is a longitudinal surveillance study of SARS-CoV-2 receptor binding domain (RBD)-specific IgG levels, neutralizing antibody levels (NAb), T cell subsets and activation, and memory B cells of 335 participants who received two doses of CoronaVac. SARS-CoV-2 RBD-specific IgG levels were measured by enzyme-linked immunosorbent assay (ELISA), while NAb were measured against two strains of SARS-CoV-2, the Wuhan and Delta variants. Activated T cells and subsets were identified by flow cytometry. Memory B and T cells were evaluated by enzyme-linked immune absorbent spot (ELISpot). FINDINGS: Two doses of CoronaVac elicited serum anti-RBD antibody response, elevated B cells with NAb capacity and CD4+ T cell-, but not CD8+ T cell-responses. Among the CD4+ T cells, CoronaVac activated mainly Th2 (CD4+ T) cells. Serum antibody levels significantly declined three months after the second dose. INTERPRETATION: CoronaVac mainly activated B cells but T cells, especially Th1 cells, were poorly activated. Activated T cells were mainly Th2 biased, demonstrating development of effector B cells but not long-lasting memory plasma cells. Taken together, these results suggest that protection with CoronaVac is short-lived and that a third booster dose of vaccine may improve protection.