Flash Learning For AIDS

Multimedia Learning System For AIDS-View Online
Multimedia Learning System For AIDS-View by Download

if fail or unable in view online or download, please logon to
https://www.drivehq.com/
By the
user name:dreamsky0804
password:12345678

go to my storage and
download the folder with name Biology Upper 6 CD3/l18/
all e-learning for AIDS including in this folder

**notices that the lessen for e-learning of Biology Upper 6 CD3 is under Government Malaysia. Only use for learning and not for sell!

Video Explanation of AIDS Process

The film below is very good explanation of the process of AIDS in body:


The film below is a very good explanation of the process of infection:

The AIDS Process in Body

Attachment to the Lymphocyte Membrane
On the surface membrane of all living cells are complex protein structures called "receptors". A receptor is often compared to a lock into which a specific key or "ligand" will fit. There are at least two receptors on T-lymphocytes to which the human immunodeficiency virus (HIV) sticks. The primary receptor, called "CD4", is shown on the right in the diagram. But a second receptor that loops through the cell membrane 7 times is critical for infection to occur.

HIV infection of a lymphocyte requires attachment of the virus to the cell membrane through both of these "ligand-receptor" links. In cells whose "7-transmembrane receptor" is different, the HIV "key" no longer matches the lymphocyte "lock" and attachment is incomplete. Those cells may avoid infection by HIV.

Entry of the Viral RNA
Tight attachment of the viral particle to receptors on the lymphocyte membrane enables fusion with the cell membrane. The viral contents, including viral RNA (shown in yellow) then empty into the cell's cytoplasm.

Like other viruses that infect human cells, HIV commandeers the host's machinery to make multiple copies of itself.

Reverse Transcription: Converting viral RNA into DNA

Viral RNA (yellow)
DNA (blue)

An enzyme (protein) that's part of the human immunodeficiency virus reads the sequence of viral RNA nucleic acids that have entered the host cell and transcribes the sequence into a complementary DNA sequence. That enzyme is called "reverse transcriptase" . Without reverse transcriptase, the viral genome couldn't become incorporated into the host cell, and couldn't reproduce.

Reverse transcriptase sometimes makes mistakes reading the RNA sequence. The result is that not all viruses produced in a single infected cell are alike. Instead, they end up with a variety of subtle molecular differences in their surface coat and enzymes. Vaccines, which induce the production of antibodies that recognize and binding to very specific viral surface molecules, are an unlikely player in fighting HIV, because throughout infection, HIV surface molecules are continually changing.

Integration of Viral DNA

Once the viral RNA has been reverse-transcribed into a strand of DNA, the DNA can then be integrated (inserted) into the DNA of the lymphocyte. The virus has its own enzyme called "integrase" that facilitates incorporation of the viral DNA into the host cells DNA. The integrated DNA is called a provirus.

Transcription: Back to RNA

As long as the lymphocyte is not activated or "turned-on", nothing happens to the viral DNA. But if the lymphocyte is activated, transcription of the viral DNA begins, resulting in the production of multiple copies of viral RNA. This RNA codes for the production of the viral proteins and enzymes (translation) and will also be packaged later as new viruses.

Translation: RNA to ProteinsThere are only 9 genes in the HIV RNA. Those genes have the code necessary to produce structural proteins such as the viral envelope and core plus enzymes like reverse transcriptase, integrase, and a crucial enzyme called a protease.

Viral Protease
When viral RNA is translated into a polypeptide sequence, that sequence is assembled in a long chain that includes several individual proteins (reverse transcriptase, protease, integrase). Before these enzymes become functional, they must be cut from the longer polypeptide chain. Viral protease cuts the long chain into its individual enzyme components which then facilitate the production of new viruses.

Assembly and Budding
Finally, viral RNA and associated proteins are packaged and released from the lymphocyte surface, taking with them a swatch of lymphocyte membrane containing viral surface proteins. These proteins will then bind to the receptors on other immune cells facilitating continued infection.

Budding viruses are often exactly like the original particle that initially infected the host. In the case of HIV, however, the resulting viruses exhibit a range of variations which makes treatment difficult.

Current Immunology Issues

Current Immunology Issues

1.
Autoimmune diseases

The immune system is regulated to recognize its own cells. Normally, it does not produce T cells to fight itself. However, there are times when antibodies are produced which fight the body’s own antigen tissues. These occurrences, which rarely happen, are called autoimmune diseases. Examples are rheumatoid arthritis, rheumatic fever, multiple sclerosis and a form of diabetes.

4. Allergies

Allergies are antigen-antibody responses that occur in some individuals as a result of exposure to specific substances. Examples include asthma, juvenile eczema and various gastro-intestinal disturbances. In similar conditions, the same allergen may not be dangerous to other individuals.

Antibody-producing stimuli and antigen-antibody responses trigger the secretion of histamine in the body. Histamine causes inflammation, rashes and bronchio-constrictions (in asthma). The number of eosinophils increases to ease the symptoms of the allergies by eliminating histamine in the bloodstream.

5. Interferon

Interferon is a protein of low molecular mass that is produced naturally in mammals and birds. It has anti-viral characteristics and is produced by the cells of the body during viral infections. It is biologically very active and is only needed in small quantities. Interferon acts by limiting viral infection and division. Because interferon delays cell growth, it could be used as an anti-cancer agent under certain conditions.

Prevention

Prevention

1. HIV is normally found in the blood, semen or vaginal fluids of the carrier. Infection can occur during blood transfer, transfer of vaginal fluid or semen from the carrier to the victim through the following ways:

(a) having sex with an HIV carrier

(b) sharing of needles or syringes with an HIV carrier

(c) transfer of HIV by a mother who is a carrier to the foetus before birth

(d) blood transfusions from an infected donor to the recipient.

2. Based on the ways in which HIV is transmitted from a carrier to a potential victim, HIV infection and AIDS can be prevented through a healthy lifestyle by avoiding

(a) casual sex, sex with prostitutes or drug addicts. If sex cannot be avoided, such as sex between husband and wife, one of whom is a carrier, then condoms should be used to reduce the risk of AIDS infection.

(b) drug addiction, drug injection or sharing needles and syringes with others

(c) the sharing of shaving razors or toothbrushes which could be contaminated with HIV infected blood

3. HIV cannot be contracted through nonsexual touch or saliva.

Symptoms Of AIDS

Symptoms of Aids

1. In the initial stages of infection, many of those infected do not show any symptoms of the disease and are called carriers.

2. After some times, the HIV infected person shows various symptoms including fever, weight loss, recurring bouts of diarrhea, persistent cough, fatigue, candidiasis infection in the mouth and pharynx and swollen lymph nodes.

3. Eventually, the infected person contracts pneumonia (lung inflammation), Kaposi’s sarcoma (skin cancer) and lymphoma (cancer of the lymphatic system).

4. The person is also likely to face mental disturbances as well as disruptions of the nervous system as a result of the infected nerve cells.

5. After five years, approximately 20% of carriers develop full blown AIDS and death occurs within the next two years.

Infection and replication of AIDS

Infection and Replication:

1. During infection, HIV attaches itself to the T4 cell membrane through a glycoprotein obtrusion in its outer membrane. Soon after that, the outer membrane of the virus breaks down, releasing RNA and the enzyme reverse transcriptions. This enzyme catalyzes the transcription of the viral RNA to DNA. The viral DNA that is formed then enters the T4 cell nucleus to combine with the T4 cell DNA. This results in the viral DNA becoming a permanent gene carrying HIV in the T4 lymphocyte of the infected person.

2. The viral DNA does not become active for some time. However, it could become activated when the body of a person responds to a certain infection through T4 lymphocyte activity. In the activated T4 lymphocyte, RNA and the viral protein replicate to form HIV core units which then leave the host cell, picking up a sample of the original outer membrane, which is still attached to the T4 cell. This way, a new generation of HIV is released into the blood. This new population of HIV then attacks other T4 cells, particularly those in the lymph nodes. As a result, the immune system of the person is crippled, making him or her more susceptible to various infections.

3. HIV also infects the brain cells causing them to be gradually damaged. HIV can also attack bone marrow and cause the precursor cells in blood tissue to become an HIV ‘pool’.

The Immune System

The immune system is a system within all vertebrates (animals with a backbone) which in general terms, is comprised of two important cell types: the B-cell and the T-cell. The B-cell is responsible for the production of antibodies (proteins which can bind to specific molecular shapes), and the T-cell (two types) is responsible either for helping the B-cell to make antibodies, or for the killing of damaged or "different" cells (all foreign cells except bacteria) within the body. The two main types of T-cells are the "helper"T-cell and the cytotoxic T-cell. The T-helper population is further divided into those which help B-cells (Th2) and those which help cytotoxic T-cells (Th1). Therefore, in order for a B-cell to do its job requires the biochemical help of Th2 helper T-cells; and, for a cytotoxic T-cell to be able to eliminate a damaged cell (say, a virally-infected cell), requires the biochemical help of a Th1 helper T-cell.

Whenever any foreign substance or agent enters our body, the immune system is activated. Both B- and T-cell members respond to the threat, which eventually results in the elimination of the substance or agent from our bodies. If the agent which gains entry is the kind which remains outside of our cells all of the time (extracellular pathogen), or much of the time (virus often released) the "best" response is the production by B-cells of antibodies which circulate all around the body in the bloodstream, and eventually bind to the agent. There are mechanisms available which are very good at destroying anything which has an antibody bound to it. On the other hand, if the agent is one which goes inside one of our cells and remains there most of the time (intracellular pathogens like viruses or certain bacteria which require the inside of one of our cells in order to live), the "best" response is the activation of cytotoxic T-cells (circulate in the bloodstream and lymph), which eliminate the agent through killing of the cell which contains the agent (agent is otherwise "hidden"). Both of these kinds of responses (B-cell or cytotoxic T-cell) of course require specific helper T-cell biochemical information as described above.

Usually, both B-cell and cytotoxic T-cell responses occur against intracellular agents which provides a two-pronged attack. Normally, these actions are wonderfully protective of us. The effect of HIV on the immune system is the result of a gradual (usually) elimination of the Th1 and Th2 helper T-cell sub-populations.

Information sites:
site1
site2

About T4 Cell

Figure above show T-lymphocyte of human

What is T4 cell?

T4 cell is a helper T cell that displays the CD4 molecule on their surface protein. It’s called as T4 lymphocyte. They also have on their surface, epitope receptors called T-cell receptors (TCRs) that, in cooperation with the CD4 molecules, have a shape capable of recognizing peptides from exogenous antigens bound to MHC-II molecules on the surface of antigen-presenting cells (APCs) and B-lymphocytes. The TCR recognizes the peptide while the CD4 molecule recognizes the MHC-II molecule.

*T-CELL RECEPTOR: The receptor on the surface of T-lymphocytes that bind corresponding peptide epitopes of protein antigens bound to MHC molecules.

*CD MOLECULE: Cluster of Differentiation molecules are molecules serving as phenotypic markers for characterizing and distinguishing leukocyte subsets and functions. For example, CD4 molecules are found on the surface T4-lymphocytes and play a role in immune recognition.

*ANTIGENS: Antigens that enter from outside the body, such as bacteria, fungi, protozoa, and free viruses.

*MHC-II MOLECULES: Class II HLA molecules are made primarily by antigen-presenting cells (APCs, eg, macrophages and dendritic cells) and B-lymphocytes. They bind peptide epitopes from exogenous antigens to enable immune recognition by T4-lymphocytes.

*ANTIGEN-PRESENTING CELL (APC): APCs include dendritic cells, macrophages, and B-lymphocytes. APCs engulf and degrade protein antigens into peptide epitopes, bind those epitopes to MHC molecules, and place them on their surface where they can be recognized by the T-cell receptors of T-lymphocytes.

*B-LYMPHOCYTES:White blood cells that mediate humoral immunity (the production of antibody molecules). B-lymphocytes recognize epitopes of antigens by way of antibody molecules called sIg present on their surface and, after activation, eventually differentiate into antibody-secreting plasma cells.

What is HIV?

The Human Immunodeficiency Virus (HIV) is the virus that leads to AIDS. HIV belongs to a subset of retroviruses called lentiviruses (or slow viruses), which means that there is an interval -- sometimes years -- between the initial infection and the onset of symptoms. HIV is less than 0.2 um in diameter.

Previous names for the HIV include human T-lymphotropic virus-III (HTLV-III), lymphadenopathy-associated virus (LAV), or AIDS-associated retrovirusARV).

Upon entering the bloodstream -- through mucous membranes or blood-to-blood contact -- HIV infects the CD4+T cells and begins to replicate rapidly.

HIV enters the body, and begins to disable the body's immune system by using the body's aggressive immune responses to the virus to infect, replicate and kill immune system cells. Gradual deterioration of immune function and eventual destruction of lymphoid and immunologic organs is central to triggering the immunosuppression that leads to AIDS.

Timeline of AIDS

• 1981 Gay Cancer
• 1982 Haitians Hemophyliacs
• 1983 AIDS Prejudice
• 1984 Virus
• 1985 Rock Hudson, Saliva OK
• 1986 T-Cells AZT
• 1987 Reagan
• 1988 Macrophages
• 1989 Going Public. 27,408 deaths
• 1990 Ryan White, Condoms in School
• 1991 Sex Drugs & Aids, Magic Johnson
• 1992 Arthur Ashe
• 1993 Needles, AZT resistance
• 1994 Losing Ground? 49,311 deaths
• 1995 #1 killer of young adults
• 1996 Cycle of Destruction. 37, 359 deaths
• 1997 CCR5, Cocktails
• 1998 Death Rates, Plunge Cocktail Side Effects
• 1999 New Directions, New Frustrations
• 2000 China
• 2001 Free care in Botswana

The AIDS Epidemic in group:
• 1981-1987
• 1988-1990
• 1991-1993
• 1994-1997
• 1998-1999
• 2000
• 2001