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Follicular dendritic cells (FDCs) play a pivotal role in the germinal center (GC) response and in the development and regulation of B lymphocytes. Pathologic changes in GCs and a loss of FDCs have previously been noted in various viral infections, notably HIV-1. However, such changes have not been formally described in a chronic parasitic infection. In BALB/c mice infected with Leishmania donovani, parasites persist in the spleen for long periods, with associated splenomegaly. To examine the fate of FDC during the course of this chronic infection, we used 1) immunohistology, with FDC-specific mAbs; and 2) passive immunization with immune complexes, followed by light and electron microscopy. This study demonstrates that destruction of FDCs and a concomitant loss of GCs are associated with chronic visceral leishmaniasis. These pathologic effects are notable from 4 wk postinfection. At 8 wk postinfection and beyond, FDC are almost undetectable by both immunohistology and functional immune complex trapping. The loss of FDCs is associated with the infiltration of heavily parasitized macrophages into the GC, and reduction in parasite burden by chemotherapy is able to retard the process of FDC destruction. These data directly demonstrate for the first time the loss of FDCs during a chronic parasite infection and suggest a mechanism underlying the aberrant regulation of B cell function in murine visceral leishmaniasis.

The International Symposium on Leishmaniasis Vaccines, held in Olinda, Brazil, on March 9–11, 2009, congregated international experts who conduct research on vaccines against the leishmaniases. The questions that were raised during that meeting and the ensuing discussions are compiled in this report and may assist in guiding a research agenda. A group to further discussion on issues raised in this policy platform has been set up at http://groups.google.com/group/leishvaccines-l.

Effector responses induced by polarized CD4+ T helper 2 (Th2) cells drive nonhealing responses in BALB/c mice infected with Leishmania major. Th2 cytokines IL-4 and IL-13 are known susceptibility factors for L. major infection in BALB/c mice and induce their biological functions through a common receptor, the IL-4 receptor alpha chain (IL-4R alpha). IL-4R alpha-deficient BALB/c mice, however, remain susceptible to L. major infection, indicating that IL-4/IL-13 may induce protective responses. Therefore, the roles of polarized Th2 CD4+ T cells and IL-4/IL-13 responsiveness of non-CD4+ T cells in inducing nonhealer or healer responses have yet to be elucidated. CD4+ T cell-specific IL-4R alpha (LcKcre IL-4R alpha-/lox)deficient BALB/c mice were generated and characterized to elucidate the importance of IL-4R alpha signalling during cutaneous leismaniasis in the absence of IL-4-responsive CD4+ T cells. Efficient deletion was confirmed by loss of IL-4R alpha expresson CD4+ T cells and impaired IL-4-induced CD4+ T cell proliferation and Th2 differentiation. CD8+, gamma delta+ and NK-T cells expressed residual IL-4R alpha, and representative non-Tcell populations maintained IL-4/IL-13 responsiveness. In contrast to IL-4R alpha, and respresentative non-T cell populations maintained IL-4/IL-13 responsiveness. In contrast to IL-4R alpha-/lox BALB/c mice, which developed ulcerating lesions following infection with L. major, Lck cre IL-4R alpha-/lox mice were resistant and showed protection to rechallenge, similar to healer C57BL/6 mice. Resistance to L. major in Lckcre IL-4R alpha-/lox mice correlated with reduced numbers of IL-10-secreting cells and early IL12p35 mRNA induction, leading to increased delayed type hypersensitivity responses, interferon-gammaproduction, and elevated rations of inducible nitric oxide synthase mRNA/parasite, similar to C57BL/6 mice. These data demonstrate that abrogation of IL-4 signaling in CD4+ T cells is required to transform nonhealer BALB/c mice to a healer phenotype. Furthermore, a beneficial role for IL-4R alpha signaling in L. major infection is revealed in which IL-4/IL-13-responsive non-CD4+ T cells induce protective responses.

Wild-type human chorionic gonadotropin (hCG) has been used as a contraceptive vaccine. However, extensive sequence homology with LH elicits production of cross-reactive antibodies. Substitution of arginine(68) of the beta-subunit (hCG(beta)) with glutamic acid (R68E) profoundly reduces the cross-reactivity while refocusing the immune response to the hCG(beta)-specific C-terminal peptide (CTP). To investigate the molecular basis for this change in epitope usage, we immunized mice with a plasmid encoding a truncated hCG(beta)-R68E chain lacking the CTP. The animals produced LH-cross-reactive antibodies, suggesting that the refocused immunogenicity of R68E is a consequence of epitope masking by a novel disposition of the CTP in the mutant rather than a structural change in the cross-reactive epitope region. This explanation was strongly supported by surface plasmon resonance analysis using a panel of anti-hCG(beta)-specific and anti-hCG(beta)/LH cross-reactive monoclonal antibodies (mAbs). Whereas the binding of the LH cross-reactive mAbs to hCG(beta)-R68E was eliminated, mAbs reacting with hCG(beta)-specific epitopes bound to hCG(beta) and hCG(beta)-R68E with identical affinities. In a separate series of experiments, we observed that LH cross-reactive epitopes were silent after immunization with a plasmid encoding a membrane form of hCG(beta)-R68E, as previously observed with the soluble mutant protein itself. In contrast, the plasmid encoding the soluble secreted form of hCG(beta)-R68E evoked LH cross-reactive antibodies, albeit of relatively low titer, suggesting that the handling and processing of the proteins produced by the two constructs differed.

This project seeks to develop a prototype systems for the analysis of single levitated micrometre-sized particles captured from an ambient aerosol. The systems is designed to use Raman scattering to establish chemical nature of the particle, whilst simultaneously recording spatial elastic light scattering data from which an assessment of particle size, shape and physical structure may be acieved.Thismulti-parametric approach should provide a means of discriminating atmospheric particles whose toxitcity is determined by morphology as well as chemical composition. Areas of application could include environmental monitoring, source apportionment, occupational air quality investigation and potentially as part of a strategy for bio-aerosol detection, other

In our preceding study, we showed that infection of mice with Mycobacterium microti leads to a dramatic increase in Ia expression on local inflammatory macrophage populations. However, the majority of these cells did not contain intracellular organisms. To evaluate the effect of parasitism of macrophages by M. microti, Ia-induction experiments were performed in vitro. We show here that Ia expression is increased on peritoneal macrophages treated with either crude lymphokine preparations or recombinant gamma-interferon (gamma-IFN) and that this expression is suppressed by M. microti in a dose dependent fashion. The degree of suppression varied between macrophage populations and could be achieved to a lesser extent with killed organisms. It was partially reversed with indomethacin but only poorly so at high infection levels. Inhibition of Ia expression may be of importance in the generation and maintenance of chronic infection.

Copyright University of Bremen, The viability of introducing phase tracing into our ray tracing with diffraction on facets model is investigated. In order to prove the method, Monte Carlo ray-tracing results for a slit, based on our diffraction formula and including phase, are compared with the Fraunhofer diffraction formula. In a next step, light scattering results obtained with this method for a long conducting column and a long dielectric column with square cross section are compared with SVM.

CBA/Ca mice were infected by either the intravenous or intraperitoneal route with Mycobacterium microti and the subsequent changes in local macrophage populations examined. Following infection, the number of macrophages increased and they showed greater expression of both MHC Class II molecules. This response was not dependent on viability of the mycobacteria, in contrast to reports with other microorganisms such as Listeria. Studies in sublethally irradiated mice indicated that persistent antigen could give rise to a response after a period of host recovery which was radiation dose dependent. This procedure also highlighted differences in the regulation of different murine class II antigens in vivo, as seen by delayed re-expression of I-E antigens. Macrophage accessory cell function, as assessed by an in vitro T cell proliferation assay, correlated with Ia expression after fixation, but not after indomethacin treatment; this highlights the diverse nature of regulatory molecules produced by these cells.

Original paper can be found at: http://www.scattport.org/files/mie-halle/Hergert-Mie-Theory-1908-2008-Booklet_Uni-Bremen-2008.pdf Copyright University of Bremen, At the University of Hertfordshire we measure and model light scattering by small particles, in particular by such relevant for climate research. The measurements comprise phase functions, linear polarization of single levitated particles (ice analogues, Saharan dust) and 2D scattering patterns for interpretation of airborne instrument data (SID, PPD1). In order to extend the applicability of geometric optics towards lower size parameters, we have developed the ray tracing with diffraction on facets (RTDF) model. It combines ray tracing with diffraction on flat facets, and is suitable for rapid computation of scattering on faceted dielectric objects such as ice crystals. or by facetted approximations of more complex shapes. Due to its low computational cost it allows the calculation of 2D scattering patterns, which are useful for interpretation of nephelometric data.

Recent studies with models of cutaneous leishmaniasis have provoked much interest in the role of CD4+ T cell subsets in determining the outcome of infectious disease. In Leishmania major infections, cure vs progressive disease correlates with the expansion of Th1-like or Th2-like CD4+ populations, respectively. We have investigated whether similar responses are associated with the differential patterns of infection seen in models of visceral leishmaniasis, caused by L. donovani. Splenic lymphocytes from infected Lsh congenic C57BL/10 (Lshs;H-2b) and B10.L-Lshr (Lshr;H-2b) mice and MHC congenic non-curing B10.D2/n (Lshs;H-2d) mice were examined for the production of cytokines representative of these CD4+ populations (IL-2, IL-3, IL-4, IL-5, and IFN-gamma). In all three strains examined, there was no evidence for the production of Th2-restricted cytokines. In addition, levels of serum IgE were depressed during the early phase of infection, indicative of in vivo IFN-gamma production. In the non-curing B10.D2/n strain, late phase of infection was associated with the decreased ability to produce cytokines in response to Ag and not with the production of IL-4 or IL-5 in response to Ag or mitogen. Serum IgE levels were also not raised above levels seen in uninfected controls. C57BL/10 mice were vaccinated with SDS-PAGE fractionated amastigote Ag bound to nitrocellulose and cytokine levels determined at various times after infection. The protocol used for vaccination was able to induce significant modulation of the course of infection in this strain and it was clear that IFN-gamma production in vitro provided an excellent correlate of rate of cure. Occasional individuals produced low levels of IL-5 in culture in response to parasite Ag, but this did not correlate with disease progression. Together, these data suggest that over-expansion of Th2-type cells and production of their specific cytokines (IL-4 and IL-5) is not a contributing factor to the variable long term course of L. donovani infection in these strains of mice.