Question

Retroviruses are often envolved in gene therapy, where a genetically engineered virus enters and infects a cell through env protein of a different virus. This method provides a wider host range for engineered virus vector. How can a virus be generated in which more than one env protein can be incorporated into a retrovirus particle by budding?

Answer 1

Gag protein and Env glycoprotein is a major retroviral structural proteins that are essential for forming infectious virus particles.

Env is synthesized, processed, and transported to plasma membrane. Incorporation of Env into progeny virions is mediated by the interaction between Env, Gag, pol and certain host factors. They encode regulatory and accessory proteins that are required for replication in host cell.

Gag is necessary for the assembly, budding, and release of virus-like particles. Gag is synthesized on cytosolic ribosomes and assembled as a polyprotein precursor. After budding and release, the polyprotein is cleaved into several domains by the viral protein protease. The major domains of the precursor Gag: matrix (MA), capsid (CA), and nucleocapsid (NC).

MA : They target Gag precursor protein to the site of assembly such as at the plasma membrane (PM). They also incorporate Env glycoprotein into virions.

CA : This is used for Gag-Gag interactions during virus assembly.

NC : It is used for nucleic acid binding domain of Gag. This is is also responsible for the binding and incorporation of the viral RNA genome into virions. This is mediated by Gag interactions with genomic RNA.

HIV is a retrovirus that has enzyme reverse transcriptase that allow it to copy RNA into DNA and use that DNA "copy" to infect human, or host, cells. When HIV infects a cell, first it attaches to and fuses with the host cell. Then viral RNA is converted into DNA and the virus uses host cell machinery to replicate itself by reverse transcription process....