The Chinese prescription lianhuaqingwen capsule exerts anti-influenza activity through the inhibition of viral propagation and impacts immune function

Influenza virus, as a common respiratory pathogen, causes seasonal epidemics and occasional severe worldwide pandemics. The most recent event including the 2009 H1N1 pandemic (“swine flu”), and the 2013 H7N9 virus outbreak in China, which led to significant morbidity and mortality [1, 2].

Human influenza virus infections primarily affect the upper respiratory tract, resulting in clinical symptoms, including cough, fever, sore throat, rhinorrhea and congestion, occasionally followed by lower respiratory diseases like pneumonia [3, 4]. It has been reported that pneumonia causes approximately 80% mortality via influenza virus infection [5]. Upon pathogen infection of the respiratory tract, the host immune system is activated to resist and clear the infection. Airway epithelium cells and alveolar macrophages release multiple pro-inflammatory cytokines and chemokines, such as tumor necrosis factor (TNF-?), interleukin-6 (IL-6), interferon (IFN), and other chemokines, including IL-8, monocyte chemoattractant protein-1 (MCP-1), and macrophage inflammatory protein (MIP). This release results in the attraction and activation of additional inflammatory cells, including macrophages and neutrophils, into the lungs, initiating the innate immune system that is crucial for the clearance and resolution of viral particles [6, 7]. Factors implicated in severe influenza include robust cytokine production, otherwise known as the “Cytokine storm”. This effect has been considered one of the major contributors to the lethal disease caused by the 1918 pandemic strain and H5N1 viruses [8, 9].

Under physiological conditions, anti-inflammatory cytokines regulate the response of inflammation and attainment of equilibrium. However, the double-sided functions of cytokines could either be beneficial or detrimental to hosts. Under pathological conditions in which the balance is disrupted, pro-inflammatory responses may spiral out of control and excessive pro-inflammatory cytokines and inflammatory immune cells may contribute to additional tissue damage and inflammation [10, 11].

Vaccination is the most effective way to prevent influenza infection now. However, the high genetic variability of the virus renders the protection incomplete. In cases of a newly emerging strain, vaccination is only available a few months after the first appearance, leaving the population vulnerable during the crucial early phases of the pandemic [4]. Currently, two classes of antivirals are used as anti-influenza drugs: amantadine derivatives that blocking the virus-specific M2-ion channel and two neuraminidase (NA) inhibitors: oseltamivir (Tamiflu) and zanamivir (Relenza), both of which are approved by the FDA [12, 13]. Laninamivir was approved for the treatment of influenza in Japan in 2010. These drugs interfere with the activity of viral neuraminidase. In addition, the nucleoside analogues ribavirin and favipiravir (T-705) exhibit a suppressive effect against almost all RNA based human viruses [13]. However, resistant viruses against these prophylactic agents have emerged in recent years. Amantadine resistance has been detected in human and avian H5N1 strains, and an increasing number of clinical strains have been confirmed as resistant NA inhibitors, including oseltamivir and zanamivir [12, 14]. Additionally, all of these therapies are aimed at inhibiting virus propagation and spread; thus, the inflammation resulting from infection and the disease remain untreated. Because the severe outcome of influenza virus infection is associated with the aberrant production of inflammatory cytokines, maintaining the immune system in an appropriately robust condition may be detrimental for the prevention of the severe symptoms of influenza [15, 16].

LH-C composed of 13 herbs was extended from two TCM prescriptions: Maxing Shigan Tang and Yinqiao San. Maxing Shigan Tang was originally described in a classical Chinese book Shanghan Lun of Han Dynasty for the treatments of febrile diseases, it has been prescribed in treating bronchitis, pneumonia and early stage of measles [17]. Yinqiao San from the TCM monograph Wenbing Tiaobian of Qing Dynasty was mainly used for the treatment of “Warm disease” characterized by fever, thirst and headache. LH-C has been used in treating regular seasonal influenza for decades. Recently, A randomized controlled trial for the comparison of LH-C with oseltamivir in therapeutic effects on patients with mild H1N1 infection demonstrated that LH-C has a significant effect on the alleviation of fever, cough, sore throat and fatigue, it also showed comparative therapeutic effectiveness in reduction of illness duration and viral shedding duration [18, 19].

In the present study, we attempted to elucidate the mechanisms of LH-C anti-influenza activity, we examined the effect of LH-C on different influenza virus strains, and further addressed the impact of LH-C on the cell line and BALB/c mice, with particular focus on its anti-inflammation potential.