RESUMO
DNA shuffling and screening technologies recombine and evolve genes in vitro to rapidly obtain molecules with improved biological activity and fitness. In this way, genes from related strains are bred like plants or livestock and their successive progeny are selected. These technologies have also been called molecular breeding-directed molecular evolution. Recent developments in bioinformatics-assisted computer programs have facilitated the design, synthesis and analysis of DNA shuffled libraries of chimeric molecules. New applications in vaccine development are among the key features of DNA shuffling and screening technologies because genes from several strains or antigenic variants of pathogens can be recombined to create novel molecules capable of inducing immune responses that protect against infections by multiple strains of pathogens. In addition, molecules such as co-stimulatory molecules and cytokines have been evolved to have improved T-cell proliferation and cytokine production compared with the wild-type human molecules. These molecules can be used to immunomodulate vaccine responsiveness and have multiple applications in infectious diseases, cancer, allergy and autoimmunity. Moreover, DNA shuffling and screening technologies can facilitate process development of vaccine manufacturing through increased expression of recombinant polypeptides and viruses. Therefore, DNA shuffling and screening technologies can overcome some of the challenges that vaccine development currently faces.
Assuntos
Embaralhamento de DNA , DNA/genética , Evolução Molecular Direcionada , Programas de Rastreamento , Vacinas de DNA/genética , Animais , Biologia Computacional , Engenharia Genética/métodos , Terapia Genética , Humanos , Proteínas Recombinantes de Fusão/imunologia , Recombinação Genética , Vacinas de DNA/imunologia , Vacinas Virais/genética , Vacinas Virais/imunologia , Vírus/genética , Vírus/imunologiaRESUMO
DNA shuffling facilitated the evolution of a human immunodeficiency virus type 1 (HIV-1) variant with enhanced replication in pig-tailed macaque peripheral blood mononuclear cells (pt mPBMC). This variant consists exclusively of HIV-1-derived sequences with the exception of simian immunodeficiency virus (SIV) nef. Sequences spanning the gag-protease-reverse transcriptase (gag-pro-RT) region from several HIV-1 isolates were shuffled and cloned into a parental HIV-1 backbone containing SIV nef. Neither this full-length parent nor any of the unshuffled HIV-1 isolates replicated appreciably or sustainably in pt mPBMC. Upon selection of the shuffled viral libraries by serial passaging in pt mPBMC, a species emerged which replicated at substantially higher levels (50 to 100 ng/ml p24) than any of the HIV-1 parents and most importantly, could be continuously passaged in pt mPBMC. The parental HIV-1 isolates, when selected similarly, became extinct. Analyses of full-length improved proviral clones indicate that multiple recombination events in the shuffled region and adaptive changes in the rest of the genome contributed synergistically to the improved phenotype. This improved variant may prove useful in establishing a pig-tailed macaque model of HIV-1 infection.
Assuntos
DNA Recombinante/genética , Variação Genética , HIV-1/genética , Leucócitos Mononucleares/virologia , Macaca nemestrina , Replicação Viral , Animais , Células Cultivadas , Evolução Molecular , Biblioteca Genômica , Infecções por HIV/virologia , HIV-1/classificação , HIV-1/fisiologia , Humanos , Dados de Sequência Molecular , Síndrome de Imunodeficiência Adquirida dos Símios/virologia , Vírus da Imunodeficiência Símia/genética , Vírus da Imunodeficiência Símia/fisiologia , Proteínas Virais/genética , Proteínas Virais/metabolismo , Proteínas Virais Reguladoras e Acessórias/genéticaRESUMO
Murine cells do not support efficient assembly and release of human immunodeficiency virus type 1 (HIV-1) virions. HIV-1-infected mouse cells that express transfected human cyclin T1 synthesize abundant Gag precursor polyprotein, but inefficiently assemble and release virions. This assembly defect may result from a failure of the Gag polyprotein precursor to target to the cell membrane. Plasma membrane targeting of the precursor is mediated by the amino-terminal region of polyprotein. To compensate for the assembly block, we substituted the murine leukemia virus matrix coding sequences into an infectious HIV-1 clone. Transfection of murine fibroblasts expressing cyclin T1 with the chimeric proviruses resulted in viruses that were efficiently assembled and released. Chimeric viruses, in which the cytoplasmic tail of the transmembrane subunit, gp41, was truncated to prevent potential interference between the envelope glycoprotein and the heterologous matrix, could infect human and murine cells. They failed to further replicate in the murine cells, but replicated with delayed kinetics in human MT-4 cells. These findings may be useful for establishing a murine model for HIV-1 replication.
