Detection of opsonizing antibodies directed against a recently circulating Bordetella pertussis strain in paired plasma samples from symptomatic and recovered pertussis patients.

Correlates of protection (CoPs) against the highly contagious respiratory disease whooping cough, caused by Bordetella pertussis, remain elusive. Characterizing the antibody response to this pathogen is essential towards identifying potential CoPs. Here, we evaluate levels, avidity and functionality of B. pertussis-specific-antibodies from paired plasma samples derived from symptomatic and recovered pertussis patients, as well as controls. Natural infection is expected to induce protective immunity. IgG levels and avidity to nine B. pertussis antigens were determined using a novel multiplex panel. Furthermore, opsonophagocytosis of a B. pertussis clinical isolate by neutrophils was measured. Findings indicate that following infection, B. pertussis-specific antibody levels of (ex-) pertussis patients waned, while the avidity of antibodies directed against the majority of studied antigens increased. Opsonophagocytosis indices decreased upon recovery, but remained higher than controls. Random forest analysis of all the data revealed that 28% of the opsonophagocytosis index variances could be explained by filamentous hemagglutinin- followed by pertussis toxin-specific antibodies. We propose to further explore which other B. pertussis-specific antibodies can better predict opsonophagocytosis. Moreover, other B. pertussis-specific antibody functions as well as the possible integration of these functions in combination with other immune cell properties should be evaluated towards the identification of CoPs against pertussis

IL-2 producing memory CD4+ T lymphocytes are closely associated with the generation of IgG-secreting plasma cells

The role of specific CD4(+) T cell subsets in the induction of Immoral immune responses in humans is largely unknown. In this study, the generation of hepatitis B surface Ag-specific CD4(+) T lymphocytes following vaccination was closely monitored and characterized at the single-cell level. The appearance and absolute numbers of hepatitis B surface Ag-specific IL-2 producing effector memory CD4(+) T lymphocytes was solely and tightly related to Ab titers reached. This relation remained present many years after vaccination. Subsequently, a relation was found between Ab titers and number of IL-2 producing memory CD4(+) T lymphocytes for various other Ags. These observations matched the findings of an in vitro assay, using different T cell subsets to induce B cell differentiation into IgG-producing plasma cells. By depleting for IL-2 producing memory T cells, we demonstrated that these cells are important for B cell differentiation into IgG-producing plasma cells. Finally, blocking the action of IL-2 with an IL-2R-alpha Ab inhibited the differentiation of B lymphocytes into IgG-producing plasma cells. Based on these findings, we conclude that the development of Ag-specific IL-2-producing memory T cells appears to be essential for the development of IgG-secreting plasma cells in humans

Sensitization by intratracheally injected dendritic cells is independent of antigen presentation by host antigen-presenting cells

Adoptive transfer of antigen-pulsed dendritic cells ( DC) in the airways of mice has been used as a model system for eosinophilic airway inflammation, which allows studying the DC-specific contribution of genes of interest or reagents to induced inflammation by genetically modifying DC or exposure of DC to compounds prior to injection in the airways. Antigen transfer and CD4(+) T cell priming by endogenous antigen-presenting cells (APCs) may interfere with the correct interpretation of the data obtained in this model, however. We therefore examined antigen transfer and indirect CD4(+) T cell priming by host APCs in this model system. Transfer of antigen between injected DC and host cells appeared to be minimal but could not be totally excluded. However, only direct antigen presentation by injected DC resulted in robust CD4(+) T cell priming and eosinophilic airway inflammation. Thus, this adoptive transfer model is well suited to study the role of DC in eosinophilic airway inflammation. J. Leukoc. Biol. 85: 64-70; 2009