Systematic screening of 96 Schistosoma mansoni cell-surface and secreted antigens does not identify any strongly protective vaccine candidates in a mouse model of infection

Background: Schistosomiasis is a major parasitic disease affecting people living in tropical and sup-tropical areas. Transmission of the parasite has been reported in 78 countries, causing significant morbidity and around 200,000 deaths per year in endemic regions. The disease is currently managed by the mass-administration of praziquantel to populations at risk of infection; however, the reliance on a single drug raises the prospect of parasite resistance to the only treatment widely available. The development of an effective vaccine would be a more powerful method of control, but none currently exists and the identification of new immunogens that can elicit protective immune responses therefore remains a priority. Because of the complex nature of the parasite life cycle, identification of new vaccine candidates has mostly relied on the use of animal models and on a limited set of recombinant proteins.

Methods: In this study, we have established an infrastructure for testing a large number of vaccine candidates in mice and used it to screen 96 cell-surface and secreted recombinant proteins from Schistosoma mansoni. This approach, using standardised immunisation and percutaneous infection protocols, allowed us to compare an extensive set of antigens in a systematic manner.

Results: Although some vaccine candidates were associated with a statistically significant reduction in the number of eggs in the initial screens, these observations could not be repeated in subsequent challenges and none of the proteins studied were associated with a strongly protective effect against infection.

Conclusions: Although no antigens individually induced reproducible and strongly protective effects using our vaccination regime, we have established the experimental infrastructures to facilitate large-scale systematic subunit vaccine testing for schistosomiasis in a murine infection model.

Detection and Characterization of Autoantibodies to Neuronal Cell-Surface Antigens in the Central Nervous System

Autoimmune encephalitis (AIE) is a group of disorders in which autoantibodies directed at antigens located on the plasma membrane of neurons induce severe neurological symptoms. In contrast to classical paraneoplastic disorders, AIE patients respond well to immunotherapy. The detection of neuronal surface autoantibodies in patients' serum or CSF therefore has serious consequences for the patients' treatment and follow-up and requires the availability of sensitive and specific diagnostic tests. This mini-review provides a guideline for both diagnostic and research laboratories that work on the detection of known surface autoantibodies and/or the identification of novel surface antigens. We discuss the strengths and pitfalls of different techniques for anti-neuronal antibody detection: (1) Immunohistochemistry (IHC) and immunofluorescence on rat/primate brain sections; (2) Immunocytochemistry (ICC) of living cultured hippocampal neurons; and (3) Cell Based Assay (CBA). In addition, we discuss the use of immunoprecipitation and mass spectrometry analysis for the detection of novel neuronal surface antigens, which is a crucial step in further disease classification and the development of novel CBAs.

Time-dependent resistance or susceptibility of tumor cells to cytotoxic antibody after exposure to a chemotherapeutic agent

We report that a chemotherapeutic agent (melphalan) can affect the sensitivity of tumor cells to cytotoxic antibody. Depending on the time interval between drug treatment and subsequent exposure to antibody and complement, the tumor cells can be either more resistant or more susceptible to antibody when compared to control cells. The number of tumor cells surviving the combined treatment was determined by a colony inhibition assay. The two antisera used in this study were directed against either virus-specific or myeloma protein-specific antigens on the surface of S107 murine myeloma cells; identical results were obtained with both sera. Twenty-four hours after exposure to the drug, the number of tumor cells surviving the antibody treatment increased. During this period of increased resistance, the tumor cells were temporarily arrested in the G(2) phase of the cell cycle. After this period of maximal resistance, the effect of cytotoxic antibody on the cells changed such that 4 days after melphalan treatment the cells were significantly more susceptible to the antibody than were the sham-treated control cells. The period of increased susceptibility correlated with an increased density of S107 myeloma protein and viral antigens on the surface of the tumor cells. Eight days after the drug treatment, the susceptibility of the tumor cells and the density of surface antigens both returned to normal levels. This study shows that the correct time interval between exposure to a drug and subsequent treatment with antibody is critical for maximal killing of the tumor cells. The basis for the differential sensitivity of the tumor cells to anti-body may be related to the drug-induced changes in the cell cycle and in antigen expression on the cell surface.

Antigenic properties of endogenous type-C viruses from spontaneously transformed clones of BALB-3T3

During long-term tissue culture of spontaneously transformed clones from BALB/c 3T3 mouse-embryo cells, some clones spontaneously begin to produce high titers of endogenous murine type-C viruses. The antigenic properties of these viruses have been analyzed by indirect immunoelectronmicroscopy and can be classified into two distinguishable populations: (a) BALB/c murine myeloma-associated extracellular viruses that carry a specific envelope antigen, xVEA, different from the typical murine leukemia viral envelope antigens; and (b) previously uncharacterized type-C viruses that have neither xVEA nor the murine leukemia viral envelope antigens. The former produces PC1 antigen and the latter might induce a new cell-surface antigen. Neither of these two populations of BALB/3T3 endogenous type-C viruses was able to infect BALB/c cells but both could infect NIH Swiss cells. A single BALB/3T3 clone, then, can release infectious endogenous type-C viruses with at least two different antigenic properties. We conclude that BALB/c somatic cells contain preexisting genetic information for production of at least closely related but, nevertheless, distinct type-C viruses.

Inhibition or enhancement of immunological injury of virus-infected cells

Within hours after infection of cells with herpes simplex, vaccinia, influenza, or Newcastle disease virus, new antigens appeared on the surface of infected cells. The interaction of specific antiviral antibody and complement with these antigens resulted in cell destruction, which was quantitated by the release of (51)Cr. A number of factors can influence the degree of cell destruction, including the density of viral antigens on the surface of infected cells, the nature of the antiviral antibody, and the presence of anti-immunoglobulins. The immunological destruction of virus-infected cells may on the one hand serve as a defense mechanism against certain viral infections, while on the other hand it may contribute to the pathology of the host.

N-acetyl-D-galactosaminyltransferase in human serum and erythrocyte membranes

This study demonstrates the presence of an N-acetyl-D-galactosaminyltransferase in human serum and in erythrocyte membranes. This enzyme catalyzes the transfer of N-acetyl-D-galactosamine from UDP-N-acetyl-D-galactosamine to a mucin receptor and 2'-fucosyllactose that have blood group H activity and may be responsible, therefore, for blood group A antigenicity. It was present in the serum of individuals with blood group A or AB but was absent from those with blood group B or O. The activity measured in the erythrocyte membrane was low and did not show clear-cut separation among donors of different blood groups. The specificity of this enzyme in serum was suggested by the ability of 2'-fucosyllactose to act as an acceptor, as well as desialyzed porcine submaxillary mucin, while lactose and desialized fetuin failed to accept N-acetyl-D-galactosamine. The catalytic properties of the N-acetyl-D-galactosaminyltransferase from serum and from erythrocyte membranes were similar.