During seasonal epidemics, influenza viruses cause approximately 250,000-500,000 deaths annually. Young, elderly and immune compromised people are those mainly at risk for developing severe disease. Pandemics return periodically and although the most recent pandemic, caused by a new strain of human H1N1, has proven less fatal than feared, variants with increased virulence may arise. Recently, influenza A viruses of swine origin have caused the first pandemic of the 21st century. These newly emerged pandemic viruses are the result of the exchange of gene segments originating from human classical swine and avian-like swine influenza viruses and have spread worldwide within a few months. Preparedness to confront an influenza pandemic is still a major public health issue. Preventive vaccination has historically been the primary means of influenza control.
Of the many animal influenza virus infection models that are being used, macaques have the advantage that their immune system most closely resembles that of humans, and that they have shown a good predictive value of vaccine immunogenicity and protective efficacy and can be used to identify pathogenic mechanisms. The macaques are also sensitive for WNV infection and thus offers unique insights into the WNV biology and WNV-induced pathological events, and enable us to evaluate the immune response and efficacy of prototype human vaccine candidates that are being developed using mouse models. Ultimately, vaccine safety and efficacy needs to be demonstrated in a suitable NHP species before they can be tested in clinical trials.
Flu and WNV infection models offers a unique model for the evaluation of potential therapies, and to study the immune mechanisms involved induced by for instance potential vaccine candidates. Additionally to the evaluation of prophylactic vaccines (intended to prevent infection), research is on-going towards the development and evaluation of new strategies for intervention/therapeutic vaccination (intended to strengthen the immune system of already infected individuals to improve their capacity to suppress the virus). One important aspect of evaluating potential vaccine candidates will be finding "correlates of protection". If a vaccine protects against a viral infection it is of utmost importance to know which mechanism is responsible for the protective activity. With this knowledge one could make better and /or stronger vaccines.