Hiv Is A Retrovirus And Has Two Types Biology Essay


HIV, Human Immunodeficiency Virus, is a virus which affects the human immune system and destroys it. The HIV virus is known as a retrovirus. This means that the virus's genetic material is encoded by RNA instead of DNA. However when the RNA starts to be incorporated into the cells of the host, DNA is produced by using the RNA sequence in the HIV virus as a template. This process is known as reverse transcriptase. Currently HIV is a major epidemic and, as there is no cure for it, it is a very deadly disease. (Peters, 2004).

According to Mortimer and Loveday (2001), there are two types of HIV viruses which consist of HIV-1 and HIV-2. The major type of HIV virus around the world is HIV-1 and this will normally lead to AIDS; HIV-2 is not very common but a majority of these cases are found in West Africa. The genomes for HIV-1 have origins which lead back to the chimpanzees whilst the HIV-2 virus genomes have origins leading back to sooty mangabey monkeys. Both types of HIV viruses do not differentiate greatly, however HIV-2 can take longer to reach the AIDS stage.

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The transmission of HIV occurs through the exchange of bodily fluids from a HIV positive person to an uninfected person. This is done by a number of ways, for example, cross contamination of blood, sexual intercourse, using contaminated needles, breast feeding and perinatal transmission (affected mother to foetus). The most common route is through unprotected sex. HIV is sexually transmitted due to the fact that the semen of an infected male contain T4 white blood cells, which contain HIV (Zimmerman and Zimmerman,2003). "Once introduced to the vagina or anus of a sexual partner", HIV and infected cells cross the mucous membrane and enter the blood stream.

Once in the blood the HIV virus encounters T4 cells, which are the main targets of HIV. This is because of a particular surface protein called CD4 that "fit hand-in-glove" with a glycoprotein, which protrudes from the lipid membrane of the virus, called glycoprotein 120 (gp120) (Zimmerman and Zimmerman,2003). This is anchored is position by another glycoprotein, gp41. Using gp120 the virus attaches to the cell membrane, then through a mechanism using the gp41, the lipid envelope of HIV fuses with the cell membrane. HIV can then enter the T4 cell and spill "its guts into the cell's interior" ( Zimmerman and Zimmerman,2003). As HIV is a retrovirus, it uses its 2 strands of RNA and the enzyme attached, reverse transcriptase. The reverse transcriptase uses the RNA coding to produce a double-stranded DNA. This DNA then enters the nucleus and becomes integrated with the host's genetic material (The British Medical Association,2004). When in the nucleus, HIV has done its job as the host cell then starts producing new viral RNA and protein. This new material assembles to form new viruses which leave the host. This host cell then dies (The British Medical Association,2004).

According to Zimmerman and Zimmerman (2003) HIV has the highest rate of mutation of all known viruses. They state that in the course of infection the virus can change its genes by as much as 30%. This "genetic instability" is due to the imprecise way which reverse transcriptase makes DNA from the viral RNA. These mutations usually are non-beneficial to the virus but occasionally one mutation causes one surface protein to change slightly thus the hosts immune system no longer recognises it, (Zimmerman and Zimmerman,2003). Consequently the immune system deteriorates, increasing the chances of developing serious infections and this can lead to AIDS. (Grahame-Smith et al, 2002).

AIDS or acquired immune deficiency symdrome, is the final stage of HIV. As HIV does not have a cure, AIDS also has no cure. Sufferers of either of these diseases do not face death due to the virus, however as the viruses suppress the immune system even small colds can become very fatal for an individual (Peters, 2004). AIDS can consist of the person developing a cancer such as 'Kaposi's sarcoma', a serious infection or 'AIDS-related dementia' (Fan et al, 2011). Nevertheless, not all individuals with HIV will contract AIDS. However, this is dependant on how HIV is initially treated. Most patients will develop AIDS within 10 years if HIV is not treated. On the other hand in around 20 years, 1 in 10 HIV-treated patients may develop AIDS (Peters, 2004).

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Certain symptoms can arise in people up to a month after being infected with HIV. These can consist of 'muscular and joint pain', 'fever', 'a rash', 'sore throat', a , 'mouth ulcers', and 'swollen glands' and can persist for up to a month (Bupa, 2010). Additional symptoms will generally not be seen after the primary symptoms have worn off for a long period of time (NHS Choices, 2010).

Symptoms related to AIDS can comprise of 'blurred vision', constant fatigue, 'shortness of breath', a 'dry cough', a long duration 'fever and swollen glands', 'night sweats', continuous diarrhoea, 'unexplained weight loss' and white spots on the tongue or in the mouth; pneumonia, tuberculosis and certain cancers can also emerge (NHS Choices, 2010).

Testing for HIV generally involves a HIV antibody test called an 'enzyme immunoassay' test, in which blood or oral fluid samples are tested in a laboratory for HIV antibodies. In a HIV infected patient, the body produces antibodies against the infection which remain in the body and show up in the antibody test. A second test, known as the 'Western blot' test is carried out to verify a positive result arising from the antibody test (Poindexter, 2010). As HIV antibodies can take time to show in the blood after a person has been infected, there is a possibility of obtaining a false negative result and so HIV testing is usually performed after the first three months of infection (Terrence Higgins Trust, n.d.). False results can be common in people suffering from HIV-2, which leads to a delay in diagnosis (All about AIDS, n.d.).

A 'Viral load test' involving Polymerase Chain Reaction can be used to calculate the quantity of HIV DNA in newborn babies whose mothers are HIV-positive; an antibody test will give a positive result, whether or not the child is infected with HIV, due to the fact that HIV antibodies are obtained from the mother and remain for up to 18 months. As a result, the Polymerase Chain Reaction process is used as an alternative test for HIV. (Avert, n.d.).

Although HIV is a relatively simple virus compared to others, there is no cure for it yet. This is because researchers are reluctant to inject people with a weakened yet live virus (Zimmerman and Zimmerman,2003). Due to the high rate of mutation in HIV, as discussed earlier, there is too high a risk that the weakened virus would mutate into a "not-so-weak" form. According to Zimmerman and Zimmerman (2003) scientists dare not used a killed virus in case any of the virus survived. They say that one solitary virus could "initiate a cycle of infection".

Treatment for HIV consists of taking antiretroviral drugs. These drugs are used to slow down the development of the HIV infection and cause life expectancy in HIV-positive people to increase by causing a reduction of the viral load in the blood (Joint Formulary Committee, 2010), hence making the recovery of the immune system possible (Bupa, 2010). A regular viral load count and 'CD4 cell count' of the blood is used as a means of establishing whether antiretroviral therapy should be used and if it is working and also the risk of obtaining a disease as a result of a weakened immune system. If the CD4 count of a HIV patient is '200 or less' then the chances of developing a serious infection related to HIV are great, whereas if the CD4 count is '500 or more' then the chances are low. (Libman et al, 2007).

The antiretroviral drugs fall into the following categories: 'nucleoside reverse transcriptase inhibitors', 'protease inhibitors', 'non-nucleoside reverse transcriptase inhibitors', 'nucleotide reverse transcriptase inhibitors', 'HIV entry and fusion inhibitors', and 'integrase inhibitors' (AHFS Drug Information, n.d.). The different types of antiretroviral drugs are combined and taken as a mixture known as 'highly active antiretroviral therapy' in order to reduce resistance of HIV to one particular antiretroviral drug (Joint Formulary Committee, 2010).

Nucleoside reverse transcriptase inhibitors are analogues of nucleosides which have been synthetically produced (AHFS Drug Information n.d.). They competitivly inhibit reverse transcriptase and stop the chain of HIV DNA being formed by becoming part of the chain. (Katzung, 2003) This drug type is phosphorylated in the body to '5-triphosphates', which are then incorporated into the viral DNA by viral reversal transcriptase. This then leads to chain termination (Randall, Kendall and Alexander, 2009) thus stopping the viral RNA from being converted to DNA, which is usually then integrated into the host's genome. This means that HIV cannot multiply as easily in the body, and thus reduces the rate of infection/effects of the HIV virus. An example of this is abacavir, this is often given to HIV patients in combination with lamivudine and zidovudine (BNF, 2009).

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Zidovudine is a nucleoside reverse transcriptase inhibitor that is used with other antiretroviral drugs as treatment for HIV (Saeb-Parsy et al, 1999); it can also be taken by pregnant women as a means of hindering HIV from passing to the child. (AHFS, n.d.). As an analogue of thymidine, Zidovudine stops HIV replicating (Khan, 2008) by working as described above.

Non-nucleoside reverse transcriptase inhibitors inhibit the action of reverse transcriptase by binding to a secondary site on the enzyme (AHFS Drug Information, n.d.).

Etravirine is a non- nucleoside reverse transcriptase inhibitor. HIV enters and infects the cell with a single stranded RNA genome. The enzyme reverse transcriptase catalyses the synthesis of viral double stranded DNA from the viral RNA, the DNA is then incorporated into the host cell DNA ready for replication and cellular processes. Etravirine impedes the action of reverse transcriptase which inhibits the formation of double stranded DNA and thus prevents the retrovirus from replicating.

Resistance to first generation drugs in this class does not result in resistance to Etravirine. This is because it is a diarylpyrimidine which means that it has multiple conformational isomers which can bind to the enzyme reverse transcriptase, enhancing enzyme and drug interaction despite previous mutations.

Protease inhibitors stop the activity of the enzyme HIV protease, which is a part of the process of DNA replication (AHFS Drug Information, n.d.). HIV protease makes new virus HIV cells if the patient is affected by HIV (CATIE, 2007). Thus inhibition of the enzyme results in virus particles being formed that are not infectious and not fully developed (AHFS Drug Information, n.d.), and hence the production of more HIV virus cells is blocked (CATIE, 2007).

As outlined by the Joint Formulary Committee (2010), the drug Ritonavir is a protease inhibitor drug. However, if low dosages of this drug are used with other protease inhibitor drugs, it can increase the effectiveness of that particular drug. Drugs of this type should be used with precaution especially in patients who suffer from the following cases; diabetes, haemophilia, lipodystrophy syndrome, hepatitis B and C.

Another example of a protease inhibitor drug is Darunavir. This drug competes with viral particles for the active site of a HIV protease. This results in the blocking of more HIV infected proteins being produced (GMC, n.d.).

Generally, the first combination of drugs given consists of two nucleoside reverse transcriptase inhibitors and one non-nucleoside reverse transcriptase inhibitor. If HIV is resistant to this combination in people then the non-nucleoside reverse transcriptase inhibitor is changed with a protease inhibitor. This is also the case in those with a psychiatric illness or those who would like to be pregnant (Joint Formulary Committee, 2010). An example of this could be: Zidovudine and Lamivudine and Lopinavir boosted with Ritonavir (MEDIC 8, n.d.). The antiretroviral drugs can cause side effects when they are initially used. These can consist of a rash, diarrhoea, nausea, 'aching muscles', fatigue, dizziness, and sleeping problems (Bupa, 2010).

The modern HIV and AIDS pandemic is one which has caused mass devastation throughout this world. There is a double stigma attached to HIV and AIDS sufferers, firstly the stigma attached to a terminally ill person. Secondly there is the stigma associated with the assumption that the patient has contracted HIV/Aids from non-socially acceptable activities such as drug use or anal sex. There is also the social labeling of 'guilty' and 'innocent' patients, those who contracted from there own actions and those who have contracted through no 'fault' of their own, i.e. new born babies. Being infected with HIV can have ruinous effects on the social life of a specific individual, they may receive hostile reactions and discrimination from the public or even those close to them.

Family is an important source of support for HIV patients. However, there are many cases in which families do not offer love and care, but instead shun and reject their relative. A woman from Zimbabwe was kept away from her family and had to sleep in the kitchen after her family found out she was HIV positive. Children who are HIV positive may endure bullying by other children or receive abuse from other parents, driving them out of their own home. In total, over 79% of people infected feared social discrimination; their identity was normally kept secret from the community, including even the health professionals. Children in Zimbabwe in particular have fallen victim to the disease, with the life expectancy expected to decrease to 27 years by 2010 as stated by UNICEF, more and more of them are becoming orphans. This could mean that more criminal activity will take place as young people are more likely to be involved in it without the guidance from their parents. Negative social consequences of HIV and Aids can be also be exemplified in countries such as Malaysia and Syria where HIV positive students will be banned from studying in certain countries such as Malaysia and Syria.

Contrary to the expected code of ethics and general good practice, HIV patients can be exposed to prejudice and mistreatment in modern Healthcare systems. Breaches in confidentiality are a common occurrence between patients and medical staff. GMC guidelines states, "Patients have a right to expect that information about them will be held in confidence by their doctors. Confidentiality is central to trust between doctors and patients." Positive test results should be given on a one to one basis between the patient and clinician with no third party being involved. Violation of these guidelines may lead to the exposure of the patient's conditions to people to whom they did not intend to inform. The social stigma and discrimination associated with HIV and Aids patients will be amplified (GMC, n.d.).

HIV patients may be further ostracized in healthcare facilities by being refused access or by being refused treatment due to the stigma associated with this disease. Incompetent or unequipped facilities are a huge issue especially in poorer countries which leads to patients not being prioritized by doctors and nurses due to their fears of contracting HIV. Poor medical resources may mean that drug treatment for patients is non-existent and patients can be perceived as hopeless cases and cause further segregation from society. The AIDS drugs are very expensive. It makes the country's health system become overburdened. The lack of resources leads to health system under strain and increase the risk for workers infected by AIDS or other disease (Beresford, 2001).

People living with HIV and Aids in modern society can experience inequity in the work place. They may encounter mockery, hateful abuse and segregation from their employers or co-workers. They may loose their jobs or not be offered positions due to their illness. This is exemplified in China where national policy states that people who are applying for civil servant positions that have HIV are ineligible for the job. Unemployment leads to many financial and social problems for people as they will be unable to properly provide for their families or themselves. Rulian Wu from the International Labour Organization states, "If the government discriminates against people with HIV, then the other sectors will follow." HIV patients can endure wide-scale alienation and continuous social rejection.

HIV and Aids have had a significant economical impact on the world. In Africa particularly it has caused the overwhelming deterioration of the countries economy and irreparable damage to society. As stated by Harvard University economist Jeffrey Sachs, "AIDS damages society by killing the people which responsible for building the society. In turn, AIDS undercuts economic growth and development" (Beresford, 2001).

The large number of people infected with AIDS has led to many households losing their income due to the illness or death of their family members. It may lead to more households being pushed below the poverty line. As stated by UNAIDS, Lost experienced workers and skilled professionals will lower the productivity of the country and weaken their confidence in the future, in turn, they are less willing to invest to their country (Beresford, 2001). Consequently this contributes to the other social problems such as a rise of the sex trade as people need new ways to bring in money.

Many households affected by AIDS cannot afford to send their children to school which lowers the education level of their country and in turn lowers the competitiveness of their country. At one South African University, two-thirds of students are infected by HIV. The death of students will result in the loss of potential skilled workers and also waste educational investment. The AIDS epidemic also makes it difficult for Africa to attract more investment from other countries as foreign investors are increasingly concerned. As stated by UNAIDS, when HIV prevalence rates rise more than 20%, gross domestic product in those countries will be lowered by 2% per year. It has stated that economic impact by AIDS is significant and it is a long term problem (Beresford, 2001).


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