Monoclonal Antibody-Based Enzyme Immunoassay for Epidemiological Studies of Asymptomatic Dengue Infection

Dengue virus (DENV) is the world most prevalent mosquito-transmitted virus. The incidence of dengue infection has been increasing and most of the infected people are asymptomatic or have non specific febrile illness. Laboratory test is essential to confirm dengue infection in epidemiological studies. We developed an indirect ELISA test based on monoclonal immunoglobulin against all four DENV serotypes and evaluated the test for the diagnosis of asymptomatic dengue infection in paired annual serum samples. The indirect ELISA was found to have a sensitivity 87.5% and specificity 78.3% at optimized cut off. The results from indirect ELISA demonstrate an incidence of asymptomatic dengue infection from children aged 4 - 11 years in Ratchaburi province, Thailand (2006-2009). These findings indicate that the indirect ELISA is suitable for serodiagnosis and seroepidemiological studies of asymptomatic dengue infection.

Serodiagnosis of asymptomatic dengue infection

Dengue virus(DENV) is a mosquito-transmitted virus that is expanding across the world,The incidence of dengue infection,especially severe disease,has been increasing,DENV consist of 4 serotypes of single stranded RNA viruses(D1-D4) in the genus Flavivirus,family Flaviviridae,Majority of dengue infections are asymptomatic cases,which cause difficulty in disease control and are important in dengue surveillance,There is still no gold standard to diagnose asymptomatic dengue infection,Plaque reduction neutralization test(PRNT) has been developed for many purposes such as immunological study,clinical study,vaccine trial and is currently the most sensitive and specific method for serological surveillance,However,PRNT shows some degree of cross reaction among different dengue serotypes especially secondary dengue infection cases and to other flaviviruses,Moreover,various modification since the beginning make PRNT lack of inter-laboratory standardization which is an important issue,This paper discusses the important of asymptomatic dengue infection and its diagnostic method.

Stability and infectivity of enteroviruses on dry surfaces:Potential for indirect transmission control

Hand,foot,and mouth disease(HFMD)is a contagious disease mainly occurring in young children,and outbreaks commonly occur among young children in the Asia–Pacific region including Thailand.Moreover,the World Health Organization(WHO)monitors HFMD in the Western Pacific region to detect outbreaks and other significant events by the Regional Event Based Surveillance System.HFMD is mainly caused by a group of enteroviruses(EVs)transmitted through direct contact(person to person)and indirect contact with contaminated objects(surface-to-hand).However,few studies have examined the surface stability of EVs.In this study,we investigated the stability of enterovirus A71(EV-A71)and coxsackievirus A16(CVA16)on three different dry surfaces(wood,plastic,and stainless steel)using the endpoint titration using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide(MTT)staining of viable cells and real-time polymerase chain reaction(viral genome detection).The results revealed that virus infectivity dramatically decreased within a few hours on dry surfaces.However,viral RNA could be detected on dry surfaces for up to 28 days.Concerning heat inactivation,both EV-A71 and CVA16 were inactivated after exposure to 60°C for 15 min.Information on virus stability on different dry surfaces will provide useful information for HFMD transmission control.