Chronic helminth infections, such as schistosomes, are negatively associated with allergic disorders. Here, using B cell IL-10-deficient mice, Schistosoma mansoni-mediated protection against experimental ovalbumin-induced allergic airway inflammation (AAI) was shown to be specifically dependent on IL-10-producing B cells. To study the organs involved, we transferred B cells from lungs, mesenteric lymph nodes or spleen of OVA-infected mice to recipient OVA-sensitized mice, and showed that both lung and splenic B cells reduced AAI, but only splenic B cells in an IL-10-dependent manner. Although splenic B cell protection was accompanied by elevated levels of pulmonary FoxP3+ regulatory T cells, in vivo ablation of FoxP3+ T cells only moderately restored AAI, indicating an important role for the direct suppressory effect of regulatory B cells. Splenic marginal zone CD1d+ B cells proved to be the responsible splenic B cell subset as they produced high levels of IL-10 and induced FoxP3+ T cells in vitro. Indeed, transfer of CD1d+ MZ-depleted splenic B cells from infected mice restored AAI. Markedly, we found a similarly elevated population of CD1dhi B cells in peripheral blood of Schistosoma haematobium-infected Gabonese children compared to uninfected children and these cells produced elevated levels of IL-10. Importantly, the number of IL-10-producing CD1dhi B cells was reduced after anti-schistosome treatment. This study points out that in both mice and men schistosomes have the capacity to drive the development of IL-10-producing regulatory CD1dhi B cells and furthermore, these are instrumental in reducing experimental allergic inflammation in mice.

Staphylococcus aureus isolates from developed countries have been extensively analyzed with respect to their virulence patterns and clonal relatedness but there is only sparse information on the molecular diversity of S. aureus isolates from Africa. In particular, little is known about S. aureus isolates from asymptomatic carriers compared with isolates causing infections. From 2008 to 2010, we prospectively collected S. aureus isolates from asymptomatic carriers and infections in Lambaréné, Gabon, Central Africa. For these isolates, we determined major virulence factors, and performed multilocus sequence typing (MLST) and spa typing. Among 163 S. aureus isolates from asymptomatic carriers, we found the MLST clonal complexes (CCs) 5, 6, 7, 8, 9, 15, 25, 30, 45, 88, 101, 121 and 152; 3.7% were methicillin-resistant (MRSA). The clinical isolates were associated with CCs 5, 8, 9, 15, 88, 121 and 152; 11% were MRSA. Sequence types 1 and 88 were significantly associated with infection and sequence type 508 was associated with carriage. Remarkably, there was a high prevalence of Panton-Valentine leukocidin (PVL) -encoding genes both in disease-related isolates (57.4%) and in carrier isolates (40.5%). We found differences in the clonal structure and virulence pattern of Gabonese S. aureus isolates from asymptomatic carriers and infections. Of note, S. aureus isolates from Gabon show a very high prevalence of PVL-encoding genes, which exceeds the rates observed for developed countries.

Summaryobjectives To evaluate the epidemiologic data of parasitic infections and co-infections in pregnant women in Lambaréné, Gabon.methods In Lambaréné, Gabon -a region of high endemicity for Plasmodium falciparum and helminths -we conducted a longitudinal survey of malaria and helminth infections during pregnancy.results Of 388 pregnant women included in the study, 98 (25%) experienced at least one episode of P. falciparum infection (incidence of 2.6 infections per year of pregnancy). One hundred and seventy pregnant women (49%) were infected with intestinal helminths, and 41 (12%) harboured Shistosoma haematobium. In total, 230 (65%) pregnant women carried at least one parasitic infection are 74 (22%) harboured at least two or more parasite species. Ascaris lumbricoides and primiparity were independently associated with Plasmodium infection during pregnancy [odds ratio (95% confidence intervals) 2.4, (1.4-3.8); 2.1, (1.3-3.5), respectively].conclusion This study shows a high burden of parasitic infections with substantial degree of parasitic co-infections in pregnant women in a Central African region. This may have implications for immunological studies and operational research involving pregnant women.