Cells go through a natural life cycle which includes growth, maturity, and death. This natural life cycle is regulated by a number of factors, and the disruption of the cycle is involved in many disease states. For example, cancer cells do not die the way normal cells do at the end of their life cycle. Here we look at the various processes by which cells age and die, both programmed and unprogrammed.

Lentivirus vector based on the human immunodeficiency virus-1 (HIV-1) has become a promising vector for gene transfer studies. A popular feature of the lentivirus vector is its ability of gene transfer and integration into both dividing and non-dividing cells. The pseudotyped envelope with vesicular stomatitis virus envelope G (VSV-G) protein broadens the target cell range.

Researchers use viral vectors for gene delivery because of their infectious nature and ability to introduce specific genes into a cell. A virus must first be packaged with the gene of interest to be introduced. The virus is then quantified, purified, and finally transduced into the target cell.

Recombinant viruses are excellent tools for the introduction of genetic material into host cells. There are many choices, and each viral vector has its place. In order to choose the best viral vector for your research goals, ask yourself the following questions:

• Do you plan to infect dividing or non-dividing cells?

• Do you need transient or stable expression of your gene?

• Are you concerned about a possible immune response from your target cell upon infection?