Biology - immunity?

Question

Many of the secondary infections are caused by bacteria,fungi and protozoans. what distinguishes a virus, such as HIV, from these organisms?

The enzyme reverse transcriptase is found inside the virus. what is its significance to the virus?

Which cells when so infected, disrupt the immune system resulting in susceptibility of the host to secondary infection?

Why have vacines against HIV had little success?

Answer 1

A virus isn't really alive in the way the other microbes you mentioned are. They are living creatures whereas a virus seems to be a piece of DNA/RNA that usually has a protein coat, and is ultimately derived from living organisms. Reverse transcriptase is an enzyme that writes DNA from an RNA template, the other way round from other living things and is essential for many viruses to replicate.
It is the T cells that are infected by HIV, although they do not make antibodies they are essential for the immune system working properly.
Viruses can mutate even faster than bacteria, since they do not require a large number of genes to keep them alive, they are not as likely to fizzle out from some bad mutations the way a living thing can. This high mutation rate makes it less likely that a vaccine will work, especially since it is the protein coat not its contents that vaccines are usually made to work against. And it doesn't help that there are several different strains.

Answer 2

Reverse transcriptase is the enzyme that allows retroviruses like HIV to write their genetic code into host DNA, even though these viruses have RNA (like a flu virus). That is their fanciest trick.

Viruses replicate by having just the minimum components necessary to look like ordinary substances that host cells normally accept into themselves through the cell membrane. They carry genetic information like that trojan horse in ancient Greece carried human attackers into a city to take it over.

The virus's genetic material gets treated like any other DNA or RNA strand once it is inside, and the parts of the cell that make proteins start to make the virus's proteins instead of host proteins.

The cell itself has no way of stopping the process. It sends out gamma interferon, and maybe something else, to warn other cells and alert the immune system.

HIV is a difficult virus to make a vaccine for because it goes through so many generations of host cell infection so quickly, and has too many opportunities to mutate around anything that is thrown at it.

The body will make an enormous number of new helper T white blood cells to replace the ones that are getting infected every day. AIDS is the condition that will result when the body just can't maintain the count. It wears down. Helper T's are necessary to fight ordinary infections.

Answer 3

A virus relies entirely on its host to survive. Many scientists even question whether a virus is a living organism. Viruses consist of RNA or DNA enclosed in a protein shell.

In the case of HIV-1, reverse transciptase converts the RNA of the virus into DNA that is then intergrated into the host cell's genome (via intergrase). This conversion and intergartion forces the host cell to make the parts for additional viruses.

Any disruption of lymphocytes can increase the likelihood of secondary infection.

Answer 4

Viruses cannot replicate their DNA without infecting a host. The reverse transcriptase in the virus takes over the DNA replication machinery in the host cell and coopts it to replicate the virus. HIV attacks B and T cells. HIV mutates constantly