Viral Genetics & Interactions (PDF)

Viral genetics and genetic interactions between viruses  Viral genetics DNA – ssDNA – dsDNA – Part ss part ds (Hepadna viruses) – Supercioled (Papilloma) – Closed circular/ linear (Circo/Adeno) RNA – +ve sense – -ve sense – Ambisense – ssRNA – dsRNA – RNA wi...

Viral genetics and genetic interactions between viruses  Viral genetics DNA – ssDNA – dsDNA – Part ss part ds (Hepadna viruses) – Supercioled (Papilloma) – Closed circular/ linear (Circo/Adeno) RNA – +ve sense – -ve sense – Ambisense – ssRNA – dsRNA – RNA with DNA intermediate  Mutation & Recombination Genotypic classification of mutants – Point mutation – Insertion and Deletion – reassortant Phenotypic classification – Plaque mutation – Antibody escape mutation – “hot mutant” – Attenuated mutant – Antigenic drifting – Conditional lethal Host ranged mutants Temperature sensitive mutants/ cold adaptive mutants Plaque assay  Recombination Reassortment Complementation Multiplicity reactivation – The production of recombinant virus progeny following the simultaneous infection of each host cell by two or more virus particles, all of which are incapable of multiplying because they carry lethal mutations induced by exposure to a mutagen Defective viruses Defective interfering particles (DI) Phenotypic mixing  Genetic recombination Influenza HIV Poliovirus REASSORTMEN T  Superinfection exclusion primary viral infection induces resistance to subsequent infection by similar viruses Cytoplasmic accumulation of Borna disease virus (BDV) nucleocapsid components prevents a subsequent infection of a different BDV strain The sim protein of bacteriophage P1 appears to block injection of nucleic acid by superinfecting phage at the cell membrane equine infectious anemia virus secretes a soluble protein that masks its cell surface receptor, blocking binding of subsequent viruses  Embbeded viruses reticuloendotheliosis virus embedded in the fowl pox genome fowlpox strains carrying the embedded reticuloendotheliosis virus cause immunosuppression in chickens while reticuloendotheliosis virus-free strains do not  Heterologous transactivation Many viruses encode powerful promoters and transactivating proteins. Transactivation of the genes of one virus species by gene products of a heterologous virus Direct binding and transactivation of a heterologous viral promoter is documented in the case of cytomegalovirus transactivating protein (IE2-86) HIV-1 long terminal repeat Herpes simplex virus protein US11 controls splicing of HTLV-1 and HIV-1