Anti-HBV Activities of Polysaccharides from Thais clavigera (Kuster) by In Vitro and In Vivo Study

Hepatitis B virus (HBV) infection remains a major global health problem. It is therefore imperative to develop drugs for anti-hepatitis B with high-efficiency and low toxicity. Attracted by the observations and evidence that the symptoms of some patients from the Southern Fujian, China, suffering from hepatitis B were alleviated after daily eating an edible marine mollusk, Thais clavigera (Kuster 1860) (TCK). Water-soluble polysaccharide from TCK (TCKP1) was isolated and characterized. The anti-HBV activity of TCKP1 and its regulatory pathway were investigated on both HepG2.2.15 cell line and HBV transgenic mice. The data obtained from in vitro studies showed that TCKP1 significantly enhanced the production of IFN-alpha, and reduced the level of HBV antigens and HBV DNA in the supernatants of HepG2.2.15 cells in a dose-dependent manner with low cytotoxicity. The result of the study on the HBV transgenic mice further revealed that TCKP1 significantly decreased the level of transaminases, HBsAg, HBeAg, and HBV DNA in the serum, as well as HBsAg, HBeAg, HBV DNA, and HBV RNA in the liver of HBV transgenic (HBV-Tg) mice. Furthermore, TCKP1 exhibited equivalent inhibitory effect with the positive control tenofovir alafenamide (TAF) on the markers above except for HBV DNA even in low dosage in a mouse model. However, the TCKP1 high-dose group displayed stronger inhibition of transaminases and liver HBsAg, HBeAg, and HBV RNA when compared with those of TAF. Meanwhile, inflammation of the liver was, by pathological observation, relieved in a dose-dependent manner after being treated with TCKP1. In addition, elevated levels of interleukin-12 (IL-12) and interferon gamma (IFN-gamma), and reduced level of interleukin-4 (IL-4) in the serum were observed, indicating that the anti-HBV effect of TCKP1 was achieved by potentiating immunocyte function and regulating the balance of Th1/Th2 cytokines.