Characterization of the dengue virus-induced helper cytokine

Abstract

Dengue type 2 virus (DV) induces a subpopulation of T lymphocytes of mouse spleen to secrete a soluble helper cytokine (HF) which enhances the DV-specific IgM antibody plaque forming cells (PFC). The present study undertaken to purify and characterize HF shows that it can be purified by low pressure liquid chromatography (LPLC) using Sephacryl S-200 column. HF consisted of two subunits, having a M_r of 6 5-68 kDa on SDS-PAGE, and both had similar activity. The isoelectric point of HF was 6.5. HF-specific antisera (HFAS) raised in mice neutralized the activity ofHF in mice, reacted with it in a Western blot assay, and bound HF in an immunosorbent column. HF bound to DV-antigen in an immunosorbent column and enhanced only the DV-specific PFC. HF had no effect on PFC against heterologous antigens such as Japanese encephalitis virus, Coxsackie B₄ virus or sheep red blood cells. HF generated in mice of H-2^k haplotype, enhanced DV-specific PFC in the same strain of mice but had no effect on that in the H-2^d or H-2^q haplotype strains of mice. Thus, DV-induced HF with a M_r of 6 5-6 8 kDa, antigen-specificity and genetic-restriction differs from most of the similarly acting cytokines but appears similar to the cell-free form of T cell receptor α, β dimer.