Use of IgM-capture ELISA for confirmation of Japanese encephalitis infections in the Philippines.

In 2001, the Research and Biotechnology Division (RBD) of St Luke's Medical Center, in collaboration with the Institute of Tropical Medicine of Nagasaki University in Japan, initiated a long-term study of Japanese encephalitis in the Philippines. Laboratory confirmation of acute cases of Japanese. encephalitis was done by IgM-capture ELISA, which detects anti-JEV immunoglobulin M in cerebrospinal fluid (CSF) samples. In the period 2002-2004, a total of 614 CSF samples were submitted to RBD, and of these, 11.7% were positive for anti-JEV IgM: 17 in 2002, 18 in 2003, 32 in 2004, and 5 in 2005. Positive cases came from patients aged 2-77 years. In the 72 positive cases where gender was identified, 44 were male and 28 female. Possible co-infections with dengue virus were also detected by separate testing for anti-dengue IgM by ELISA in 17 CSF samples positive for JE.

Association of increased platelet-associated immunoglobulins with thrombocytopenia and the severity of disease in secondary dengue virus infections.

Severe thrombocytopenia and increased vascular permeability are two major characteristics of dengue haemorrhagic fever (DHF). To develop a better understanding of the roles of platelet-associated IgG (PAIgG) and IgM (PAIgM) in inducing thrombocytopenia and its severity of disease in patients with secondary dengue virus infection, the relationship between the PAIgG or PAIgM levels and disease severity as well as thrombocytopenia was examined in 78 patients with acute phase secondary infection in a prospective hospital-based study. The decrease in platelet count during the acute phase recovered significantly during the convalescent phase. In contrast, the increased levels of PAIgG or PAIgM that occurred during the acute phase of these patients decreased significantly during the convalescent phase. An inverse correlation between platelet count and PAIgG or PAIgM levels was found in these patients. Anti-dengue virus IgG and IgM activity was found in platelet eluates from 10 patients in an acute phase of secondary infection. Increased levels of PAIgG or PAIgM were significantly higher in DHF than those in dengue fever (DF). An increased level of PAIgM was associated independently with the development of DHF, representing a possible predictor of DHF with a high specificity. Our present data suggest that platelet-associated immunoglobulins involving antidengue virus activity play a pivotal role in the induction of thrombocytopenia and the severity of the disease in secondary dengue virus infections.