Is Obesity One of Physiological Factors which Exert Influenza Virus-induced Pathology and Vaccine Efficacy?

ABSTRACT

Obesity has been considered a risk factor for infectious diseases including the influenza virus. Most epidemiological investigations indicated that obesity is connected to the severity of influenza, although there are some exceptions. Many studies using obese humans and animal models showed that immune response was impaired in the obese group, increasing susceptibility and severity of influenza virus. However, the exact mechanism by which obesity inhibits anti-viral immune response remains unknown. This review discusses current studies about the properties of immune cells in obesity. In obesity, the balance of adipokines is disrupted and the level of proinflammatory cytokine is increased compared with non-obese control. Moreover, macrophages induced systemic inflammation by secreting cytokines such as TNF-alpha and IL-6, antigen presenting capacity of dendritic cells was diminished which affect T cell responses, and influenza-specific antibody production seems reduced and decreased even faster after vaccination in obese mouse. The number of circulating T cells and proliferation of mitogen-stimulated T cells dropped and T cell memory was significantly low in influenza infected obese mouse. Therefore, obesity may be one of factors for disease progression in influenza virus infection and vaccine efficacy.