[Show abstract][Hide abstract] ABSTRACT: Toxoplasmosis, a zoonotic disease caused by Toxoplasma gondii, is an important public health problem and veterinary concern. Although there is no vaccine for human toxoplasmosis, many attempts have been made to develop one. Promising vaccine candidates utilize proteins, or their genes, from microneme organelle of T. gondii that are involved in the initial stages of host cell invasion by the parasite. In the present study, we used different recombinant microneme proteins (TgMIC1, TgMIC4, or TgMIC6) or combinations of these proteins (TgMIC1-4 and TgMIC1-4-6) to evaluate the immune response and protection against experimental toxoplasmosis in C57BL/6 mice. Vaccination with recombinant TgMIC1, TgMIC4, or TgMIC6 alone conferred partial protection, as demonstrated by reduced brain cyst burden and mortality rates after challenge. Immunization with TgMIC1-4 or TgMIC1-4-6 vaccines provided the most effective protection, since 70% and 80% of mice, respectively, survived to the acute phase of infection. In addition, these vaccinated mice, in comparison to non-vaccinated ones, showed reduced parasite burden by 59% and 68%, respectively. The protective effect was related to the cellular and humoral immune responses induced by vaccination and included the release of Th1 cytokines IFN-γ and IL-12, antigen-stimulated spleen cell proliferation, and production of antigen-specific serum antibodies. Our results demonstrate that microneme proteins are potential vaccines against T. gondii, since their inoculation prevents or decreases the deleterious effects of the infection.
[Show abstract][Hide abstract] ABSTRACT: Tailed phages are genome delivery machines exhibiting unequaled efficiency acquired over more than 3 billion years of evolution.
Siphophages from the P335 and 936 families infect the Gram-positive bacterium Lactococcus lactis using receptor-binding proteins anchored to the host adsorption apparatus (baseplate). Crystallographic and electron microscopy
(EM) studies have shed light on the distinct adsorption strategies used by phages of these two families, suggesting that they
might also rely on different infection mechanisms. Here, we report electron microscopy reconstructions of the whole phage
TP901-1 (P335 species) and propose a composite EM model of this gigantic molecular machine. Our results suggest conservation
of structural proteins among tailed phages and add to the growing body of evidence pointing to a common evolutionary origin
for these virions. Finally, we propose that host adsorption apparatus architectures have evolved in correlation with the nature
of the receptors used during infection.
Full-text · Article · Nov 2012 · Journal of Virology
[Show abstract][Hide abstract] ABSTRACT: Toxosplasma gondii is the model parasite of the phylum Apicomplexa, which contains numerous obligate intracellular parasites of medical and
veterinary importance, including Eimeria, Sarcocystis, Cryptosporidium, Cyclospora, and Plasmodium species. Members of this phylum actively enter host cells by a multistep process with the help of microneme protein (MIC)
complexes that play important roles in motility, host cell attachment, moving junction formation, and invasion. T. gondii (Tg)MIC1-4-6 complex is the most extensively investigated microneme complex, which contributes to host cell recognition and
attachment via the action of TgMIC1, a sialic acid-binding adhesin. Here, we report the structure of TgMIC4 and reveal its
carbohydrate-binding specificity to a variety of galactose-containing carbohydrate ligands. The lectin is composed of six
apple domains in which the fifth domain displays a potent galactose-binding activity, and which is cleaved from the complex
during parasite invasion. We propose that galactose recognition by TgMIC4 may compromise host protection from galectin-mediated
activation of the host immune system.
Full-text · Article · Mar 2012 · Journal of Biological Chemistry
[Show abstract][Hide abstract] ABSTRACT: Eimeria spp. are a highly successful group of intracellular protozoan parasites that develop within intestinal epithelial cells of poultry, causing coccidiosis. As a result of resistance against anticoccidial drugs and the expense of manufacturing live vaccines, it is necessary to understand the relationship between Eimeria and its host more deeply, with a view to developing recombinant vaccines. Eimeria possesses a family of microneme lectins (MICs) that contain microneme adhesive repeat regions (MARR). We show that the major MARR protein from Eimeria tenella, EtMIC3, is deployed at the parasite-host interface during the early stages of invasion. EtMIC3 consists of seven tandem MAR1-type domains, which possess a high specificity for sialylated glycans as shown by cell-based assays and carbohydrate microarray analyses. The restricted tissue staining pattern observed for EtMIC3 in the chicken caecal epithelium indicates that EtMIC3 contributes to guiding the parasite to the site of invasion in the chicken gut. The microarray analyses also reveal a lack of recognition of glycan sequences terminating in the N-glycolyl form of sialic acid by EtMIC3. Thus the parasite is well adapted to the avian host which lacks N-glycolyl neuraminic acid. We provide new structural insight into the MAR1 family of domains and reveal the atomic resolution basis for the sialic acid-based carbohydrate recognition. Finally, a preliminary chicken immunization trial provides evidence that recombinant EtMIC3 protein and EtMIC3 DNA are effective vaccine candidates.
[Show abstract][Hide abstract] ABSTRACT: P335 lactococcal phages infect the Gram+ bacterium Lactococcus lactis using a large multiprotein complex located at the distal part of the tail and termed baseplate (BP). The BP harbors the receptor-binding
proteins (RBPs), which allow the specific recognition of saccharidic receptors localized on the host cell surface. We report
here the electron microscopic structure of the phage TP901-1 wild-type BP as well as those of two mutants bppL − and bppU−, lacking BppL (the RBPs) or both peripheral BP components (BppL and BppU), respectively. We also achieved an electron microscopic
reconstruction of a partial BP complex, formed by BppU and BppL. This complex exhibits a tripod shape and is composed of nine
BppLs and three BppUs. These structures, combined with light-scattering measurements, led us to propose that the TP901-1 BP
harbors six tripods at its periphery, located around the central tube formed by ORF46 (Dit) hexamers, at its proximal end,
and a ORF47 (Tal) trimer at its distal extremity. A total of 54 BppLs (18 RBPs) are thus available to mediate host anchoring
with a large apparent avidity. TP901-1 BP exhibits an infection-ready conformation and differs strikingly from the lactococcal
phage p2 BP, bearing only 6 RBPs, and which needs a conformational change to reach its activated state. The comparison of
several Siphoviridae structures uncovers a close organization of their central BP core whereas striking differences occur at the periphery, leading
to diverse mechanisms of host recognition.
Full-text · Article · Oct 2010 · Journal of Biological Chemistry
[Show abstract][Hide abstract] ABSTRACT: Eimeria tenella is the causative agent of coccidiosis in domestic chickens. We report the complete backbone and side chain NMR assignments for the second microneme adhesive repeat of the microneme protein 3 of E. tenella.
No preview · Article · Dec 2009 · Biomolecular NMR Assignments