Hiv Aids Paper - It's Effect on the Immune System

THE HUMAN IMMUNODEFICENYC VIRUS

AND IT'S EFFECT ON THE IMMUNE SYSTEM

By Shawn Rutledge

Immunology

Dr. James Daly

MARCH 27, 2011

Introduction

The HIV virus was discovered in 1983 by noble prize winners Luc Montagnier and Francoise Barre-Sinouss. Since then the disease has been associated with the development of AIDS in 1984. AIDS is a retrovirus called "Acquired Immunodeficiency Syndrome." Its counterpart the "Human Immunodeficiency Virus" (HIV) has infected and killed 30 million people worldwide, infected and greater than this number affected. When untreated HIV leads to acquired immune deficiency (AIDS) a condition that renders the body's nature defense system (immune system) helpless against infection. Individuals that have adequate health care are treated with highly active anti-retro viral therapy (HARRT). While treatment is effective it is also very expensive and unavailable in most third world countries. Individuals treated with HARRT experience side effects and development of viral resistance is a common problem. The retrovirus drug HARRT cannot cure HIV; therefore, it could never cure HIV infection. Given the complex socioeconomic, political and scientific problems that limit the efficiency of HARRT, development of a preventative or therapeutic vaccine remains a very challenge problem for HIV/AIDS research. Research scientists from various parts of the world are working together to develop new and more effective treatment to combat this incurable disease. In this paper, I will focus on the effects of HIV on the immune system, social economic problems and HIV prevention.

THE HUMAN IMMUNODEFICIENCY VIRUS

The HIV is part of a group of viruses called retrovirus. The word "retrovirus" means that this type of virus is capable of copying RNA and DNA. According to research biologist, there are no discovered organisms besides the HIV/AIDS on earth that has the ability to copying RNA and DNA. The virus has two exact copies of single-stranded RNA as its genetic (genome) material in its center.

The genome is surrounded by a core of tightly packed proteins. The core itself is surrounded by membranes called an "envelope." The envelope is composed of fatty (lipids) molecules and different membrane-bound proteins. One of the membrane -bound proteins can bind to a particular protein on the surface of immune cells, called T-cells. As a result, the virus becomes attached. When the protein binds, the virus will migrate inside the T-cell the envelope is removed by enzymes inside the cell. The internal core is exposed and broken down. This last phase results in exposure of the virus's RNA genetic material. An enzyme attached to the RNA, called "reverse transcriptase" begins to make complimentary base-pair single-stranded copies of the RNA into DNA. The single strand of DNA is also copied by the reverse transcriptase to make double-stranded DNA. The DNA is inserted into one of 46 chromosomes within our cells; The DNA that was inserted into the cell is used as a template for making more virus particles. These new virus particles can be released from the infected cell and infect adjacent cells ( Parson and Grant, 2009).

THE IMMUNE SYSTEM

The immune system is very complex system found in most vertebrate. It contains two important cell types, T-cells and B-cells. The B-cells are responsible for the production of antibodies, while T-cells are responsible for helping B-cells make antibodies and for killing different (except bacteria) types of damaged cells within the body. There are two types of T-cells, "Helper" T-cell and cytotoxic T-cell. The helper T-cell is divided into two groups, T-helper1 which helps the B-cells and T-helper2 which helps cytotoxic T-cells. In order for a B-cell to accomplish its job it requires assistance from the Th2-helper T-cell and for a cytotoxic T-cell to kill damaged cells, it requires help from a Th1 helper T-cell. When a foreign agent or substance invades the body, the immune system is activated. The T-cell and B-cell will respond to the threat and eliminate foreign substance from the body. Foreign agents such as extracellular pathogens or virus's that were just released, will gain entry and remain outside the cell at all times . The best response to fight these pathogens would be the production of B-cell antibodies, which circulate around the body in the bloodstream, and eventually bind to the pathogen or agent. The body contains excellent biochemical mechanisms that are very effective at eliminating pathogens that have an antibody attached to it. However, intracellular pathogens such as virus's and particular bacteria will migrate inside the eukaryote cell and stay there for a long period of time. The best defense against intracellular pathogens is the activation of cytotoxic T-cells; these cells will eliminate the agent by killing the cell which contains the agent. Both responses require biochemical information from the helper T-cell. Usually, B-cell and cytotoxic T-cell responses occur against intracellular agents. These reactions are very efficient at protecting the body from pathogens that invade the immune system. The effect of HIV on the immune system is the result of a slow elimination of T-helper1 and T-helper2 population (Wang et.al., 2010).

HOW HIV EFFECTS THE IMMUNE SYSTEM

HIV is classified as a lentivirus, due to its long period of incubation between initial infection and development of AIDS. The envelope that is part of HIV contains proteins called gp120. The gp120 protein recognizes a protein on the helper T-cells called CD4+, and physically associates with it. The CD4+ protein is a permanent part of both helper Th1 and Th2 T-cell membrane, making CD4+ a specific receptor for HIV. This virus however, can also infect other cells such as macrophages and certain cells that are involved in engulfing substances through a process known as phagocytosis. (Wang et.al., 2010). As a result of the interaction of CD4+ on helper T-cells, HIV specifically infects important cells that are necessary to activate both B-cell and cytotoxic T-cell immune responses. Without helper T-cells, the body cannot properly produce antibodies. Therefore, infected cells containing