Synthesis and Surface Expression of Hyaluronan by Dendritic Cells and Its Potential Role in Antigen Presentation

Abstract Hyaluronan (HA) is a large glycosaminoglycan consisting of repeating disaccharide units of glucuronic acid and N-acetylglucosamine. HA is known to act as a filling material of extracellular matrices and as an adhesive substrate for cellular migration. Here we report that dendritic cells (DC) express mRNAs for HA synthases and hyaluronidases, actively synthesize HA, and display HA on their surfaces. Interestingly, HA expression levels on DC were not significantly altered by their maturation states. With respect to physiological function, three specific HA inhibitors, i.e., bovine proteoglycan, a 12-mer HA-binding peptide (GAHWQFNALTVR) termed Pep-1, and an oligomeric Pep-1 formulation, all interfered with DC-induced activation of CD4+ T cells isolated from DO11.10 TCR transgenic mice. For example, Pep-1 oligomer efficiently inhibited DC-dependent cluster formation, IL-2 and IFN-γ production, and proliferation by DO11.10 T cells in vitro without affecting the viabilities of DC or T cells, DC function to uptake exogenous proteins, or DC-T cell conjugate formation at earlier time points. These observations suggest a paracrine mechanism by which DC-associated HA facilitates some of the late changes in T cell activation. Although T cells constitutively expressed mRNAs for HA synthases and hyaluronidases, their surface HA expression became detectable only after activation. Oligomeric Pep-1 and bovine proteoglycan both inhibited mitogen-triggered T cell activation in the absence of DC, suggesting an autocrine mechanism by which HA expressed by T cells assists their own activation processes. Finally, adoptively transferred DO11.10 T cells showed progressive mitosis when stimulated with Ag-pulsed DC in living animals, and this clonal expansion was inhibited significantly by administration of Pep-1 oligomer. Our findings may introduce a new concept that relatively simple carbohydrate moieties expressed on DC and perhaps T cells play an important immunomodulatory role during Ag presentation.</jats:p

Hyaluronidase of Bloodsucking Insects and Its Enhancing Effect on Leishmania Infection in Mice

Hyaluronidases are enzymes degrading the extracellular matrix of vertebrates. Bloodsucking insects use them to cleave the skin of the host, enlarge the feeding lesion and acquire the blood meal. In addition, resulting fragments of extracellular matrix modulate local immune response of the host, which may positively affect transmission of vector-borne diseases, including leishmaniasis. Leishmaniases are diseases with a wide spectrum of clinical forms, from a relatively mild cutaneous affection to life-threatening visceral disease. Their causative agents, protozoans of the genus Leishmania, are transmitted by phlebotomine sand flies. Sand fly saliva was described to enhance Leishmania infection, but the information about molecules responsible for this exacerbating effect is still very limited. In the present work we demonstrated hyaluronidase activity in salivary glands of various Diptera and in fleas. In addition, we showed that hyaluronidase exacerbates Leishmania lesions in mice and propose that salivary hyaluronidase may facilitate the spread of other vector-borne microorganisms

Lyapunov spectrum of asymptotically sub-additive potentials

For general asymptotically sub-additive potentials (resp. asymptotically additive potentials) on general topological dynamical systems, we establish some variational relations between the topological entropy of the level sets of Lyapunov exponents, measure-theoretic entropies and topological pressures in this general situation. Most of our results are obtained without the assumption of the existence of unique equilibrium measures or the differentiability of pressure functions. Some examples are constructed to illustrate the irregularity and the complexity of multifractal behaviors in the sub-additive case and in the case that the entropy map that is not upper-semi continuous.Comment: 44 page

Stability in antigenic reactivity of the major outer surface protein, OspA, in borrelia burgdorferi, during persistent infection in Syrian hamsters

The spirochete Borrelia burgdorferi is the causative agent of Lyme disease, a multisystem disorder that can cause a variety of disorders in susceptible mammalian hosts. The immune response of infected mammals, including humans, is ineffective in clearing B. burgdorferi as demonstrated by the ability to reisolate the spirochete from naturally and experimentally infected hosts after extended periods of time. Recent evidence suggests that this pathogen evades the immune response in part through changes in antigenic reactivity.The purpose of this study was to determine if outer surface protein A (OspA) of B. burqdorferi varies in the course of infection in Syrian hamsters and thus potentially plays a role in evading the host immune response. To assess the degree of change, differences in the binding of a murine monoclonal antibody (H5332) were measured using IFA and ELISA techniques over a 9-week period of time.Results of this study suggest that OspA is persistently expressed in infected Syrian hamsters for at least 9-weeks. Moreover, this protein, or at least the epitope that H5332 binds with, is stably expressed. These results indicate OspA, or at least the epitope of OspA that I probed, does not appear to contribute to the evasive mechanisms of 8. burgdorferi in Syrian hamsters.Thesis (M.S.)Department of Biolog

Stability in antigenic reactivity of the major outer surface protein, OspA, in borrelia burgdorferi, during persistent infection in Syrian hamsters

The spirochete Borrelia burgdorferi is the causative agent of Lyme disease, a multisystem disorder that can cause a variety of disorders in susceptible mammalian hosts. The immune response of infected mammals, including humans, is ineffective in clearing B. burgdorferi as demonstrated by the ability to reisolate the spirochete from naturally and experimentally infected hosts after extended periods of time. Recent evidence suggests that this pathogen evades the immune response in part through changes in antigenic reactivity.The purpose of this study was to determine if outer surface protein A (OspA) of B. burqdorferi varies in the course of infection in Syrian hamsters and thus potentially plays a role in evading the host immune response. To assess the degree of change, differences in the binding of a murine monoclonal antibody (H5332) were measured using IFA and ELISA techniques over a 9-week period of time.Results of this study suggest that OspA is persistently expressed in infected Syrian hamsters for at least 9-weeks. Moreover, this protein, or at least the epitope that H5332 binds with, is stably expressed. These results indicate OspA, or at least the epitope of OspA that I probed, does not appear to contribute to the evasive mechanisms of 8. burgdorferi in Syrian hamsters.Department of BiologyThesis (M.S.