Like all viruses, HIV is not able to reproduce or express its genes without the help of a living cell. First the virus must be able to successfully infect a cell. To do so, HIV uses a veil of human proteins in a Trojan horse manner to infect immune cells. To go from cell to cell, HIV is packaged in an "envelope" or capsid made from viral proteins and proteins from human cell membranes. Like the ebola virus, HIV relies on proteins from human cell membranes to gain entrance into a cell. In fact, Johns Hopkins scientists have identified 25 human proteins that have been incorporated into the HIV-1 virus and aid its ability to infect other body cells. Once inside a cell, HIV uses the cell's ribosomes and other components to make viral proteins and to replicate. When new virus particles are formed, they emerge from the infected cell cloaked in a membrane and proteins from the infected cell. This helps the virus particles avoid immune system detection.