Dengue virus serotype-2 impairs proliferation of healthy donors' T lymphocytes.

OBJECTIVES: T lymphocytes are not infected by dengue virus (DENV), nevertheless it is possible that exposure to DENV may affect their function. T lymphocytes from DENV-infected individuals are impaired in their proliferative capacity, although this effect has been attributed to altered function of antigen-presenting cells rather than to an intrinsic defect on T lymphocytes. Here we analyzed whether T lymphocytes from healthy donors became impaired in their proliferative capacity following in vitro exposure to DENV serotype-2 (DENV-2), as well as the possible mechanisms for this. METHODS: Isolated CD4+ and CD8+ T lymphocytes from healthy donors were in vitro exposed to DENV-2, before polyclonal activation, cell proliferation, IL-2 synthesis. IL-2Rα expression, nuclear translocation of NF-AT and NF-κB, and intracellular calcium flux were assessed. RESULTS: In vitro exposure of both CD4+ and CD8+ T lymphocytes from healthy donors to DENV-2 impairs cell proliferation, IL-2 synthesis, and IL-2Rα (CD25) cell membrane expression. Signalling wise, exposure to DENV-2 impairs the nuclear translocation of NF-AT, downstream of intracellular calcium mobilization, as well as that of NF-κB. CONCLUSION: In the course of a dengue infection, direct exposure of T lymphocytes to DENV could affect cell-mediated immune responses.

Class specific antibody responses to newborn larva antigens during Trichinella spiralis human infection.

A follow-up study of the class antibody responses to newborn larva (NBL) antigens in individuals involved in an outbreak of human trichinellosis was carried out by ELISA assays. The data showed that similar kinetics of antibody responses of different magnitude developed in trichinellosis patients; it was low by week 3, a peak raised by week 5 and decreased from week 7 up to the end of the study. The IgA-ELISA assay was the most sensitive and specific while the IgM was the least sensitive and specific. IgA antibodies to NBL antigens were detected in 80% of patients while IgE, IgG and IgM responses were observed in 44, 31 and 19% of the patients by week 3, respectively. From weeks 5 to 7, IgA antibodies were found in 89 to 100% of the patients while lower percentages (0-82%) were found for the other isotypes. Reactivity of IgA, IgE, IgG and IgM to NBL antigens decreased from week 37 to 57 after infection (0-38%). These results suggest that detection of IgA antibodies may be useful for early diagnosis and epidemiological studies in human trichinellosis.

The stage-specificity of the IgA response to newborn larva and TSL-1 antigens of Trichinella spiralis in humans infected with the parasite.

Characterization of human IgA responses to newborn larva (NBL) and TSL-1 antigens was carried out by ELISA assays. Relevant and differential IgA antibody responses to these antigens were detected in humans infected with T. spiralis. The inhibition ELISA results showed that the IgA response to NBL antigens was inhibited significantly by both NBL and TSL-1 antigens and to a lesser extent when phosphorylcholine (PC) was used as inhibitor. In contrast, the IgA response to TSL-1 antigens was inhibited by the homologous antigen and to a lesser extent by the NBL and PC. Thus, the early IgA antibodies developed in trichinellosis patients contained a portion of IgA antibodies directed to PC which is present in TSL-1, A and NBL component. Another portion of antibodies to NBL are directed to other common non-defined epitopes present in TSL-1 and NBL antigens. All together these results suggest that the IgA response to common epitopes in antigens of both stages of the parasite may be useful for early diagnosis and epidemiological studies of human trichinellosis.