Role Of Burkholderia Pseudomallei-Specific Igg2 In Adults With Acute Melioidosis, Thailand

Melioidosis is a life-threatening infectious disease caused by the gram-negative bacillus Burkholderia pseudomallei. An effective vaccine is needed, but data on protective immune responses in human melioidosis are lacking. We used ELISA and an antibody-dependent cellular phagocytosis assay to identify the major features of protective antibodies in patients with acute melioidosis in Thailand. We found that high levels of B. pseudomallei-specific IgG2 are associated with protection against death in a multivariable logistic regression analysis adjusting for age, diabetes, renal disease, and neutrophil count Serum from melioidosis survivors enhanced bacteria uptake into human monocytes expressing Fc gamma RIla-H/R131, an intermediate-affinity IgG2-receptor, compared with serum from nonsuivivors. We did not find this enhancement when using monocytes carrying the low IgG2-affinity Fc gamma Rlla-R131 allele. The findings indicate the importance of IgG2 in protection against death in human melioidosis, a crucial finding for antibody-based therapeutics and vaccine development.