Polymerase chain reaction techniques: applications in parasitic diseases

dNTPs: Nucleotides; ESTs: Expressed sequence tags; HAT-RAPD-PCR: High annealing temperature random amplified polymorphic DNA PCR; HSP: Heat shock protein; ITS: Internal transcribed spacer; mRNA: Messenger RNA; MSP: Merozoite suiface proteins; MT-PCR: Multiplex tandam PCR; PCR: Polymerase chain reaction; qPCR: Quantitative basic PCR; qRtime-PCR: Quantitative real-time PCR; qRT-PCR: Quantitative reverse transcriptase PCR; QT-NASBA: Quantitative nucleic acid sequence-based amplification; RAPD: Random amplified polymorphic DNA; RFLP: Restriction fragment length polymorphism; RNA: Ribonucleic acid; Rtime-PCR: Real time PCR; RT-PCR: Reverse transcriptase PCR; SNP: Single nucleotide polymorphism;TLRs: Toll-like receptors

Novel regulatory SNPs in the promoter region of the TNFRSF18 gene in a Gabonese population

Parasites are accountable for driving diversity within immune gene families. We identified and investigated regulatory single nucleotide polymorphisms (SNPs) in the promoter regions of the tumor necrosis factor receptor superfamily member 18 (TNFRSF18) gene by direct sequencing in a group of male Gabonese individuals exposed to a wide array of parasitic diseases such as malaria, filariasis and schistosomiasis. Two new promoter variants were identified in 40 individuals. Both novel variants were heterozygous and were linked to SNP #rs3753344 (C/T), which has been described. One of the SNP variants (ss2080581728) was close to the general transcription factor site, the TATA box. We further validated these new promoter variants for their allelic gene expression using transient transfection assays. One new promoter variant with two base changes (C/T - ss2080581728/rs3753344) displayed an altered expression of the marker gene. Both novel variants remained less active at the non-induced state in comparison to the major allele. The allele frequencies observed in this study were consistent with data for other African populations. The detection and analysis of these human immune gene polymorphisms contribute to a better understanding of the interaction between host-parasite and expression of Treg activity.

Immunogenetics and infectious diseases: special reference to the mayor histocompatibility complex

Many studies have tried to identify genetic markers for infectious diseases, some of them have focused on human leukocyte antigens (HLA). The products of HLA genes interact with surface-specific receptors of T lymphocytes, resulting in activation of the host's immune response. Association of bacterial, viral, parasitic and fungal infections with the host's HLA has been widely investigated. The type and strength of this association differs among distinct populations, as well as among racial and/or ethnic groups. The new molecular methods for the identification of the HLA alleles, and the resulting new nomenclature, have contributed to a better understanding of this system. Unfortunately, this information has not been adequately transmitted to clinicians, which hampers the understanding of the association between the HLA system and diseases. We revised relevant studies on the association of HLA genes with infectious diseases, demonstrating their importance in the pathogenic mechanisms, through increased susceptibility or protection against infections and their complications.

Current millenium biotechniques for biomedical research on parasites and host-parasite interactions

The development of biotechnology in the last three decades has generated the feeling that the newest scientific achievements will deliver high standard quality of life through abundance of food and means for successfully combating diseases. Where the new biotechnologies give access to genetic information, there is a common belief that physiological and pathological processes result from subtle modifications of gene expression. Trustfully, modern genetics has produced genetic maps, physical maps and complete nucleotide sequences from 141 viruses, 51 organelles, two eubacteria, one archeon and one eukaryote (Saccharomices cerevisiae). In addition, during the Centennial Commemoration of the Oswaldo Cruz Institute the nearly complete human genome map was proudly announced, whereas the latest Brazilian key stone contribution to science was the publication of the Shillela fastidiosa genomic sequence highlythed on a Nature cover issue. There exists a belief among the populace that further scientific accomplishments will rapidly lead to new drugs and methodological approaches to cure genetic diseases and other incurable ailments. Yet, much evidence has been accumulated, showing that a large information gap exists between the knowledge of genome sequence and our knowledge of genome function. Now that many genome maps are available, people wish to know what are we going to do with them. Certainly, all these scientific accomplishments will shed light on many more secrets of life. Nevertheless, parsimony in the weekly announcements of promising scientific achievements is necessary. We also need many more creative experimental biologists to discover new, as yet un-envisaged biotechnological approaches, and the basic resource needed for carrying out mile stone research necessary for leading us to that "promised land" often proclaimed by the mass media

Evidence for biological inheritance of the eosinophil response to internal parasites in southeastern Brazil

Uma amostra de 177 indivíduos pertencentes a 120 famílias nucleares, completas ou incompletas, de Bambui, Estado de Minas Gerais, sudeste do Brasil, foi estudada com o objetivo de apurar algumas das causas da variabilidade da taxa de eosinófilos em pessoas parasitadas por vermes intestinais com ciclo de vida extra-digestivo. A análise de segregaçäo, aplicada aos dados sem correçäo para a assimetria, mostrou que a hipótese de um gene principal aditivo é consistente com os dados, enquanto que as hipóteses que supöem a açäo de um gene dominante, de um gene recessivo ou ainda herança multifatorial näo explicam, adequadamente, a significante agregaçäo familial observada. A correçäo mais parcimoniosa para assimetria mostrou resultados semelhantes, mas näo permitiu a distinçäao entre os modelos dominante e recessivo, embora permitisse a rejeiçäo do modelo codominante. Considerando que esse modelo supöe ser a assimetria devida ao entrelaçamento de duas distribuiçöes, esses resultados parecem concordar com aqueles obtidos quando os dados näo foram corrigidos. Pode-se sugerir que o papel desempenhado por vários fatores genéticos independentes na resistência/suscetibilidade à infestaçäo por helmintos seja determinado, principalmente, por suas capacidades de agir no estabelecimento de uma resposta eosinofílica.

Genetics of the immune responses and disease susceptibility

The identification of factors causing complex diseases contributes to the understanding of their pathophysiology and provides new diagnostic methods and potentially new prevention and treatment strategies. Polymorphic genes functioning in innate and acquired immune mechanisms participate in interindividual and interpopulational differences of susceptibility to many diseases of complex etiology and pathogenesis. Numerous studies have related especially the HLA genes to pathologic autoimmunity, and to the pathogenesis of infectious diseases and cancer. In recent years, the search for additional susceptibility genes has been facilitated by the resources and information generated by genome mapping and diversity analysis. Genes involved in immunity are being identified at an accelerating rate, and the investigation of implications of their variability regarding disease pathogenesis is beginning. Studies of Brazilian populations have especially contributed to recognition of genes modulating susceptibility to infections and their clinical outcome. Since genetic polymorphism differs between populations, the heterogeneity of the Brazilian populations, if properly explored, will add valuable information to the understanding of causes of complex diseases. Conversely, disease studies contribute to knowledge of the evolution and functional implications of genetic polymorphism.

Interet de l'epidemiologie appliquee aux maladies parasitaires

De nombreuses maladies transmissibles; dont les maladies parasitaires; sont distribuees de maniere heterogene dans les populations exposees; on constate en particulier des concentrations familiales que les facteurs de milieu n'expliquent qu'en partie comme dans l'exemple du paludisme; particulierement etudie a l'OCEAC; des modeles experimentaux animaux peuvent egalement avoir mis en evidence des facteurs genetiques intervenant dans la susceptibilite a la maladie