Envelope retroviral

Some 24 per cent of all gene therapy clinical trials undertaken to date have employed retroviral vectors as gene delivery systems. Retroviruses are enveloped viruses. Their genome consists of ssRNA of approximately 5-8 kb. Upon entry into sensitive cells, the viral RNA is reverse transcribed and eventually yields double-stranded DNA. This subsequently integrates into the host cell genome (Box 14.1). The basic retroviral genome contains a minimum of three structural genes ... 

Human immunodeficiency virus (HIV) is a member of the retrovirus family, classified under the lentivirus genus. Retroviruses are enveloped RNA viruses, which contain a core of capsid proteins, viral RNA, and enzymes. All infectious retroviral virions contain an enzyme, reverse transcriptase, which catalyzes the formation of a complementary DNA strand from an RNA template. A double-stranded DNA copy of the viral RNA genome (proviral DNA) may then be integrated into and replicated with the host cell genome. 

Paramyxoviruses cause respiratory tract diseases such as croup and pneumonia, as well as measles and mumps. The envelope proteins of these viruses share some features in common with influenza and retroviruses. These similarities include a precursor protein that is cleaved into two fragments, the second of which, called El, bears a fusion peptide at its amino terminus. In addition, peptides from the paramyxovirus FI proteins assemble into stable helical bundles resembling HIV gp41 and influenza HA2 (Baker et al, 1999 Lawless-Delmedico et al, 2000 Zhao et al, 2000). The paramyxovirus F protein differs from influenza HA and retroviral TM... 

There are several options for the display of alien proteins using this technique. Proteins can be displayed on the envelope spike protein (Env), in which case selective pressure is placed on the population of viral particles before reinfection into fresh mammalian cells, much like phage display. So far, the potential of retroviral display for the generation and screening of eukaryotic expression libraries has only been demonstrated for small peptides. For example, avian leukemia virus (ALV) has been used to display a random peptide library (8-mer) and used to select specific sequences that bind to monoclonal antibodies that recognize short peptides (FLAG and HA tag antibodies). A lOOx enrichment of binding sequences was observed per round of selection.232... 

Immunotoxins must be internalized before they can function to kill a cell (1). We have targeted immunotoxins to the HIV-envelope proteins because they are the only virus-encoded structures on the surface of productively infected cells. Most virologists consider that retroviral-envelope proteins found on the cell surface are in the process of leaving the cell via viral budding. 

A FIGURE 4-43 Retroviral life cycle. Retroviruses have a genome of two identical copies of single-stranded RNA and an outer envelope. StepD After viral glycoproteins in the envelope interact with a specific host-cell membrane protein, the retroviral envelope fuses directly with the plasma membrane, allowing entry of the nucleocapsid into the cytoplasm of the cell. StepH Viral reverse transcriptase and other proteins copy the viral ssRNA genome into a double-stranded DNA. StepH The viral... 

F. C., Dixon, F.J., and Good, R.A. (1981) Low-Calorie Diet Selectively Reduces Expression of Retroviral Envelope Glycoprotein gp70 in Sera of NZB x NZW FI Hybrid Mice, J. Exp. Med. 154,1116-1124. 

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