Immunobiology of African Trypanosomes: Need of Alternative Interventions

Trypanosomiasis is one of the major parasitic diseases for which control is still far from reality. The vaccination approaches by using dominant surface proteins have not been successful, mainly due to antigenic variation of the parasite surface coat. On the other hand, the chemotherapeutic drugs in current use for the treatment of this disease are toxic and problems of resistance are increasing (see Kennedy (2004) and Legros et al. (2002)). Therefore, alternative approaches in both treatment and vaccination against trypanosomiasis are needed at this time. To be able to design and develop such alternatives, the biology of this parasite and the host response against the pathogen need to be studied. These two aspects of this disease with few examples of alternative approaches are discussed here

Crystal Structure of a Human Single Domain Antibody Dimer Formed through VH-VH Non-Covalent Interactions

Single-domain antibodies (sdAbs) derived from human VH are considered to be less soluble and prone to aggregate which makes it difficult to determine the crystal structures. In this study, we isolated and characterized two anti-human epidermal growth factor receptor-2 (HER2) sdAbs, Gr3 and Gr6, from a synthetic human VH phage display library. Size exclusion chromatography and surface plasmon resonance analyses demonstrated that Gr3 is a monomer, but that Gr6 is a strict dimer. To understand this different molecular behavior, we solved the crystal structure of Gr6 to 1.6 Å resolution. The crystal structure revealed that the homodimer assembly of Gr6 closely mimics the VH-VL heterodimer of immunoglobulin variable domains and the dimerization interface is dominated by hydrophobic interactions

Control of Trypanosoma evansi infection is IgM mediated and does not require a type I inflammatory response

Very recent reports have documented that Trypanosoma evansi, the etiological agent of the livestock disease "surra," can cause human trypanosomiasis. In contrast to trypanosomes causing human African trypanosomiasis, T. evansi has a wide geographic distribution and host range, yet information about the immunobiological aspects of T. evansi trypanosomiasis is limited. Here, we show that, although T. evansi causes the induction of tumor necrosis factor (TNF), interferon-gamma, and nitric oxide during the early stage of infection, none of these molecules are crucial for parasitemia control and survival of the infected animal. However, TNF and TNF receptor 2 affect the induction of late-stage anemia. Using B cell-and immunoglobulin M (IgM)-deficient mice, we identified IgM as being crucial for parasitemia control and host survival. Collectively, our results show that, compared with other trypanosomes, T. evansi displays a distinct host-parasite interaction profile, give that, despite an infection-associated induction of proinflammatory molecules, only IgM antibodies contribute significantly to parasite control

Single-domain antibody functionalized quantum dots for cellular imaging of cancer cells

Peer reviewed: YesNRC publication: Ye

Single-domain antibody functionalized CdSe/ZnS quantum dots for cellular imaging of cancer cells

Photoluminescent (PL) semiconductor nanocrystals, when spherical in shape also termed as quantum dots (QDs), have attracted significant attention in biolabeling and bioimaging applications. Usually, such biooriented applications require targeting to the site of interest, and the use of antibodies is acknowledged as one common strategy for specific and compelling targeting. Conventional antibodies and some of their derivatives have been tested as targeting agents; to the best of our knowledge, the present study is the first with the use of single-domain antibodies (sdAbs) to overcome some disadvantages related to issues such as stability, aggregation, and production cost. Our sdAbs, which are small but fully functional recognition proteins and derived from camelid species, are superior to all of the above antibody choices. This manuscript addresses our efforts on the synthesis and targeting of bioconjugated PL QDs with a sdAb named EG2, which binds strongly to epidermal growth factor receptor (EGFR), a protein of which is widely known as a tumor marker. PEGylation was performed at the same time. The entity of our PEGylated-and-sdAb-conjugated QDs, presented as proof of principle, is robust in specific labeling of EGFR on in vitro grown SK-BR3 and MDA-MB468 human breast-cancer cells.Peer reviewed: YesNRC publication: Ye

Isolation of funcitonal single domain antibody by whole cell immunization: Implications for cancer treatment.

Carcinoembryonic antigen related cell adhesion molecule (CEACAM) 6 is over-expressed in different types of cancer cells. In addition, it has also been implicated in some infectious diseases. Targeting this molecule by an antibody might have applications in diverse tumor models. Single domain antibody (sdAb) is becoming very useful format in antibody engineering as potential tools for treating acute and chronic disease conditions such as cancer for both diagnostic as well as therapeutic application. Generally, sdAbs with good affinity are isolated from an immune library. Discovery of a new target antigen would require a new immunization with purified antigen which is not always easy. In this study, we have isolated, by phage display, an sdAb against CEACAM6 with an affinity of 5 nM from a llama immunized with cancer cells. The antibody has good biophysical properties, and it binds to the cells expressing the target antigen. Furthermore, it reduces cancer cells proliferation in vitro and shows an excellent tumor targeting in vivo. This sdAb could be useful in diagnosis as well as therapy of CEACAM6 expressing tumors. Finally, we envisage it would be feasible to isolate good sdAbs against other interesting tumor associated antigens from this library. Therefore, this immunization method could be a general strategy for isolating sdAbs against any surface antigen without immunizing the animal with the antigen of interest each time.Peer reviewed: YesNRC publication: Ye

Interferon-γ and nitric oxide in combination with antibodies are key protective host immune factors during Trypanosoma congolense Tc13 infections

The control of chronic Trypanosoma congolense trypanosomiasis was analyzed using several gene-deficient mouse strains. First, interferon (IFN)-γ receptor (IFN-γ-R)-deficient mice were used to show that IFN-γ-mediated immune activation is crucial for parasitemia control. Second, infections in major histocompatibility complex (MHC) class II-deficient mice indicate that this molecule is needed for initiation of IFN-γ and subsequent tumor necrosis factor (TNF) production. Downstream of IFN-γ-R signaling, inducible NO synthase (iNOS)-dependent trypanosome killing occurs, as is shown by the hypersusceptible phenotype of iNOS-deficient mice. Besides proinflammatory responses, B cells and, more specifically, immunoglobulin (Ig) G antibodies are crucial for parasite killing. Hence, parasitemia control is abolished in B cell-deficient mice, whereas IgM-deficient mice control the infection as efficiently as do wild-type mice. In addition, splenectomized mice that have a normal IgM response but an impaired IgG2a/3 response fail to control T. congolense infection. Collectively, these results suggest that host protective immunity against T. congolense is critically dependent on the combined action of the proinflammatory mediators/effectors IFN-γ, TNF, and NO and antiparasite IgGs. © 2006 by the Infectious Diseases Society of America. All rights reserved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe