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Apicomplexan parasites are responsible for some of the most devastating human and veterinarian diseases and are parasites of great economic importance. Apicomplexa include Plasmodium, Toxoplasma and Babesia species. The pathogenic mechanisms developed by Apicomplexa parasites, in particular those that reside in a parasitophorous vacuole, involve considerable changes to the host cell, including the expression of variable surface proteins required for immune evasion. In Plasmodium falciparum infections, host cell remodeling is responsible for disease symptomology and severity in the human host. This work represents a multi-faceted study of antigenic secretion and the role of secreted antigens in pathogenesis. We study in detail the mechanisms of antigen secretion in Apicomplexa parasites. By use of comparative genomics, we find Plasmodium Export Element (PEXEL)-like motifs in a subset of Cryptosporidium and Babesia secreted proteins. However, in Babesia the motif functions as a spherical body targeting sequence, suggesting that secretory mechanisms in Apicomplexa are adapted to the parasite's intracellular lifestyle. To elucidate the relationship and function of exported antigens, we first focused on P. falciparum to determine gene co-expression modules. We found that in vivo, export modules are composed of constitutively or variably expressed genes, the latter group associated with patient clinical phenotypes. We then focused on a novel gene family called "phist" and show, using transcriptional expression profiling, its role in P. falciparum cytoadherence. In total, we demonstrate that antigen secretion is an evolutionary mechanism in Apicomplexa parasites and that variant expression of the genes encoding these antigens may allow parasites to adapt to environmental stresses.

The spirochete Borrelia hermsii avoids the immune response of its mammalian host through multiphasic antigenic variation. Serotype specificity is determined by Variable major proteins (Vmp), in the outer membrane. Through a non reciprocal recombination between linear plasmids, a formerly silent vmp gene replaces another vmp gene at a telomeric expression locus downstream from a common expression site. B. hermsii before and after the switch from serotype 7 to serotype 21, was examined in detail. The nucleotide sequence of the vmp7 and vmp21 genes and flanking regions was determined. The vmp7 and vmp21 are 77% identical in their coding sequence, and the deduced translation products are 63% identical. No antigenic cross reactivity is observed between Vmp7 and Vmp21. This suggests a folding of the proteins in which the similar regions are buried, and not exposed when it is presented at the bacterial surface. Vmp7 and Vmp21 have consensus sequences of prokaryotic lipoproteins and are processed as such when expressed in E. coli. The 5' regions of silent and expressed vmp7 and vmp21 were compared. Silent and active vmp7 and vmp21 genes shared a block of homologous sequence at their 5' ends. Sequences upstream of silent vmp7 and vmp21 genes lacked a promoter and differed substantially from each other. In this antigenic switch a vmp gene was activated by a recombination event which placed it downstream of a promoter. The vmp gene promoter is preceded by a poly(dT dA) ran and three imperfectlyrepeated elements of 2 kb. Each of the 2 kb repeats contains inverted repeats of approximately 0.2 kb at their termini. There is no evidence of the presence of similar elements elsewhere in the genome of B. hermsii. One or more of these elements may stimulate vmp gene switch or expression. The African relapsing fever species Borrelia crocidurae and the American species B. hermsii display many similarities. In both species the vmp genes are localised to linear plasmids, and the vmp genes are activated on the transcriptional level. The nucleotide sequence of their expression sites, however, are not related. Still, the possibility that the switch is mechanistically similar in B. crocidurae and B. hermsii, cannot be ruled out. The binding of B. crocidurae causes aggregation of erythrocytes around the spirochete. The aggregation is reminiscent of the erythrocyte rosetting seen in malarial infections. The erythrocytes at the B. crocidurae surface may protect them from clearance by the host. Thus, the rosetting may constitute an additional mechanism in B. crocidurae for the evasion of the immune reaction. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1994, härtill 5 uppsatser.</p> / digitalisering@umu

Serologically related arenaviruses have been isolated from West Africa, Mozambique, Zimbabwe and the Central African Republic. Human disease is only associated with the West African isolates. The virulence of Mozambique, Zimbabwe and Central African Republic isolates in humans is not known. This Thesis is an account of work carried out by the author to compare the biological characteristics of isolates from West Africa, Mozambique and Zimbabwe. It describes the successful isolation and identification of the aetiological agents, their physicochemical and antigenic characteristics and describes in vivo studies using mice, guinea pigs and Rhesus monkeys. A direct comparison was made with a patient diagnosed as having Lassa fever. The disease in man and monkeys following infection with Lassa virus was similar. The Rhesus monkey and guinea pig proved suitable experimental models in which to study and compare the pathogenic responses and also to evaluate various aspects of protection. These animal models when immunised with the viruses from Mozambique and Zimbabwe were protected when subsequently challenged with Lassa virus. The Mozambique and Zimbabwe isolates proved to have morphological and physicochemical characteristics not dissimilar from West African Lassa viruses and those members of the arenavirus family from South America. Serological and immunochemical investigations suggest the existence of both common and unique antigenic determinants on the viruses from Mozambique, -Zimbabwe and West Africa. This grouping also coincides with the geographic separation of the viruses, i.e. Lassa - West Africa and Mopeia -southeast Africa. Similar differences in host susceptibility have also been demonstrated. Lassa virus produces a fatal haemorrhagic disease while Mopeia isolates produce only an asymptomatic infection. The combined data suggests the possibility of two virus groups within the 'Old World' arenavirus classification. The proposed name, 'Mopeia', forms one group and includes the viruses from Mozambique and Zimbabwe. The Lassa strains from West Africa form the second group. It is suggested that the Mopeia viruses are minor antigenic variants of Lassa and should be included within the arenavirus family.

Thesis (Ph. D.)--University of Missouri--Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves : 128-138). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1998. / Typescript. Vita. Includes bibliographical references (leaves 87-91). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1998. / Typescript. Vita. Includes bibliographical references (leaves 87-91). Also available on the Internet.

Highly pathogenic avian influenza (HPAI) virus poses a significant economic disease burden to the poultry sector of Vietnam, and is a credible threat for emergence of novel zoonotic viruses. This thesis examines the molecular evolution and epidemiology of HPAI A(H5) viruses in Vietnam identified through the national poultry surveillance system. The investigations comprised analysis of detection rates and geographic distribution of A(H5) clade variants from samples collected in live bird markets (LBMs); comprehensive analysis of whole genome sequences of viruses collected from 2012 to 2015; development of laboratory protocols for production of reference chicken antisera; and in-depth antigenic characterisations of contemporary A(H5N1) isolates. The findings underscored the high prevalence and widespread distribution of HPAI A(H5) virus within apparently healthy poultry sampled in LBMs and the difficulties in designing appropriate and effective disease management strategies. Whole genome analysis revealed significant diversification and reassortment of A(H5) viruses, with substantial in-situ evolution of clade 1 and 2.3.4 viruses between 2010 and 2012 and lineage replacements involving clade 2.3.2.1 and 2.3.4.4 viruses during 2014-2015. Antigenic analysis of contemporary A(H5N1) clade variants using chicken antisera produced at the National Center for Veterinary Diagnostics (NCVD) proved to be feasible and reproducible, and recapitulated similar patterns of clade clustering as ferret antisera. Antigenic relationships between existing poultry vaccines and circulating field viruses also appeared aligned with in-vivo vaccine challenge studies, in terms of protection profiles. Given the co-circulation of multiple, antigenically distinct clade variants, there is a great need for vaccine strategies capable of inducing broadly cross-reactive immunity. If traditional inactivated vaccines are used, bivalent or trivalent formulations may be required. The results strongly suggest that antigenic data could ultimately be used as a surrogate (or as a precursor) to challenge studies that take time and resources to conduct, thus potentially enabling more rapid assessments and decisions about poultry vaccine selection by Vietnamese animal health authorities.

Orientador: José Maurício Sforcin / Resumo: A própolis é um produto resinoso, elaborado pelas abelhas a partir de diferentes partes das plantas, e se destaca por suas inúmeras propriedades biológicas, e pela possibilidade de aplicação na indústria farmacêutica. Recentemente, nosso grupo tem estudado sua ação sobre monócitos – células do sistema fagocítico mononuclear que exercem importante função na resposta imune. Neste projeto, visamos investigar a possível ação moduladora da própolis na apresentação de antígenos por monócitos humanos, utilizando um antígeno infeccioso (subunidade B da enterotoxina termolábil de Escherichia coli - EtxB), um antígeno tumoral (MAGE-1), o ácido retinóico (AR) e lipopolissacarídeo (LPS), simultaneamente ou não a própolis, avaliando o possível efeito citotóxico dos tratamentos, a expressão de receptores celulares (TLR-2, TLR-4, HLA-DR, CD40, CD80) e a produção de citocinas (TNF-α, IL-6, IL-10 e IL-12). A modulação da autofagia foi avaliada através da expressão de genes que codificam as proteínas Beclin-1 e LC3-II, utilizando a rapamicina simultaneamente ou não a própolis. A própolis não alterou a viabilidade dos monócitos humanos e exerceu efeito citoprotetor nas células incubadas com os estímulos. A própolis manteve a expressão basal dos receptores de superfície celular; porém, em associação com MAGE-1 e LPS, diminuiu a expressão de CD40 estimulada pelos antígenos isoladamente. Em associação com AR, a própolis manteve a ação do antígeno sobre os receptores. Já a associação da própolis co... (Resumo completo, clicar acesso eletrônico abaixo) / Mestre

Two-dimensional electrophoretic protein profiles of in vivo and in vitro propagated T.pallidum subsps. pallidum Nichols strain were analyzed and compared. This comparative analysis revealed two in vitro synthesized, cytoplasmic cylinder-associated polypeptides with molecular masses 29.5 and 34.7 kDa, pI 5.62, and one in vitro "lost" polypeptide with molecular mass 34.7 kDa, pI 5.34. integral membrane proteins of in vitro and in vivo propagated T. pallidum was identified by phase partitioning with the nonionic Triton X-114, and twelve outer membrane-associated, antigenic proteins were identified in western blots probed with pooled human secondary syphilitic sera. The solubilization of the outer membrane of T. pallidum with Triton X-114 were monitored by electron microscopy. Treatment of freshly harvested 35S labeled T. pallidum with 1% Triton X-114 resulted in solubilization of the outer membrane and reduction of the diameter of the treponemes from .14 +/- .02 micrometers to .095 +/- .003 micrometers. Examination of thin sections of untreated organisms showed integrity of outer and cytoplasmic membranes. In contrast, thin sections of Triton X-114-treated trponemes showed integrity of the cytoplasmic membrane but the loss of the outer membrane. The cytoplasmic cylinders generated by detergent treatment retained their periplasmic flagella, as judged by electron microscopy and immunoblotting. Integral membrane proteins of Treponema phagedenis were also identified by phase partitioning with Triton X-114, and sizteen cross-reactive, outer membrane-associated, outer membrane-associated, antigenic polypeptides were identified in western blots probed with pooled human secondary syphilitic sera. The results of this study indicate that tow-dimensional protein profiles of in vivo and in vitro propagated T.pallidum are almost identical except for the differences mentioned. This results also indicate that 1% Triton X-114 selectively solubilizes the outer membrane, and the antigenic hydrophobic proteins present in the detergent phrase are located exclusively in the outer membrane.