12.1 Retroviral vectors

Among the viral vectors used for gene therapy trials, retrovirus is the most commonly used RNA virus. Retroviruses are the first to develop for the application of gene therapy related studies. Retroviruses are the RNA containing enveloped viruses and are classified into oncoretroviruses, lentiviruses, and spumaviruses.

Retroviruses are enveloped viruses having two copies of ssRNA genome. The viral genome codes for three essential proteins; namely gag , pol , and env (Figure 2). The genome is flanked with long terminal repeats (LTR) in its terminal end. The gag gene in retroviruses codes for capsid, matrix, and nucleocapsid proteins. The pol gene codes for viral enzymes protease, integrase, and reverse transcriptase. The env gene codes for surface glycoproteins, which mediates the virus entry into the cells. Oncoretroviruses only codes for these three proteins while lentiviruses and spumaviruses are more complex in nature (discussed in later chapter).

Figure 12.1 Schematic diagram of retrovirus: