Detrimental Effect of Trypanosoma brucei brucei Infection on Memory B Cells and Host Ability to Recall Protective B-cell Responses.

BACKGROUND: Trypanosoma brucei brucei evades host immune responses by multiple means, including the disruption of B-cell homeostasis. This hampers anti-trypanosome vaccine development. Because the cellular mechanism underlying this pathology has never been addressed, our study focuses on the fate of memory B cells (MBCs) in vaccinated mice upon trypanosome challenge. METHODS: A trypanosome variant surface glycoprotein (VSG) and fluorescent phycoerythrin were used as immunization antigens. Functional and cellular characteristics of antigen-specific MBCs were studied after homologous and heterologous parasite challenge. RESULTS: Immunization with AnTat1.1 VSG triggers a specific antibody response and isotype-switched CD73+CD273+CD80+ MBCs, delivering 90% sterile protection against a homologous parasite challenge. As expected, AnTat1.1 VSG immunization does not protect against infection with heterologous VSG-switched parasites. After successful curative drug treatment, mice were shown to have completely lost their previously induced protective immunity against the homologous parasites, coinciding with the loss of vaccine-induced MBCs. A phycoerythrin immunization approach confirmed that trypanosome infections cause the general loss of antigen-specific splenic and bone marrow MBCs and a reduction in antigen-specific immunoglobulin G. CONCLUSIONS: Trypanosomosis induces general immunological memory loss. This benefits the parasites by reducing the stringency for antigenic variation requirements.

Establishment of a Standardized Vaccine Protocol for the Analysis of Protective Immune Responses During Experimental Trypanosome Infections in Mice.

To date, trypanosomosis control in humans and animals is achieved by a combination of parasitological screening and treatment. While this approach has successfully brought down the number of reported T. b. gambiense Human African Trypanosomosis (HAT) cases, the method does not offer a sustainable solution for animal trypanosomosis (AT). The main reasons for this are (i) the worldwide distribution of AT, (ii) the wide range of insect vectors involved in transmission of AT, and (iii) the existence of a wildlife parasite reservoir that can serve as a source for livestock reinfection. Hence, in order to control livestock trypanosomosis the only viable long-term solution is an effective antitrypanosome vaccination strategy. Over the last decades, multiple vaccine approaches have been proposed. Despite repeated reports of promising experimental approaches, none of those made it to a field applicable vaccine format. This failure can in part be attributed to flaws in the experimental design that favor a positive laboratory result. This chapter provides a vaccine protocol that should allow for a proper outcome prediction in experimental anti-AT vaccine approaches.

Modification of cellular DNA by synthetic aziridinomitosenes.

Two synthetic aziridinomitosenes (AZMs), Me-AZM and H-AZM, structurally related to mitomycin C (MC) were evaluated for their anticancer activity against six cancer cell lines (HeLa, Jurkat, T47D, HepG2, HL-60, and HuT-78) and tested for their DNA-modifying abilities in Jurkat cells. Cytotoxicity assays showed that Me-AZM is up to 72-fold and 520-fold more potent than MC and H-AZM, respectively. Me-AZM also demonstrated increased DNA modification over MC and H-AZM in alkaline COMET and Hoechst fluorescence assays that measured crosslinks in cellular DNA. Me-AZM and H-AZM treatment of Jurkat cells was found to sponsor significant DNA-protein crosslinks using a K-SDS assay. The results clearly indicate that the AZM C6/C7 substitution pattern plays an important role in drug activity and supports both DNA-DNA and DNA-protein adduct formation as mechanisms for inducing cytotoxic effects.