The Human Immunodeficiency Virus Quiz

Answer: Because of the RNA material in the viral core

Most viruses have DNA in their core, which when incorporated into the host cell's DNA is replicated, spreading the viral infection. Retroviruses on the other hand have RNA in their core. This single strand RNA is synthesised into double stranded DNA inside the host cell before it is incorporated into the host cell's DNA, enabling viral replication.

Answer: Kinshasa, Democratic Republic of Congo

Through out the years scientists have collected blood samples from people who have died of unknown causes and archived them for future analysis. In recent years some of these samples have been screened for the presence of HIV antibody. The oldest sample to test positive for HIV was collected from a man in Kinshasa, Democratic Republic of Congo in 1959. No blood samples predating the Kinshasa 1959 sample have tested positive for HIV to date.

Answer: Simian Immuno Deficiency Virus

The genetic structure of certain sub types of the Simian Immuno Deficiency Virus (SIV) strongly resembles that of HIV-1 and HIV-2. These viruses are found among primates in the same regions in Central and Western Africa believed to be the early epicentre of the HIV pandemic. Virologists have therefore theorised that SIV somehow managed to cross the species barrier in the middle of the twentieth century, infecting humans. HIV is the first retrovirus to do so.

Answer: Dr. Robert Gallo and Dr Luc Montagnier

In 1983 Dr Luc Montagnier of the Pasteur Institute, France claimed to be the first to isolate the HIV Type 1 virus, responsible for the acquired immune deficiency syndrome being reported among gay men in America, and heterosexual populations in Central Africa during the early 1980's.

A year later Dr Robert Gallo of America claimed that he had in fact been the first to isolate the virus. After a protracted court case it was decided to recognise Gallo and Montagnier as co-discoverers of the HIV-1 virus.

Answer: CD4 receptors and co receptors

HIV envelope proteins gp. 41 and gp. 120 bind to CD4 receptors and co receptors found predominantly in Helper T lymphocytes (CD+4 cells). This allows the virus to bind the viral membrane to the cellular membrane of the host cell. The core of the virus, containing viral RNA and the enzymes necessary for viral replication is then released into the cytoplasm of the host cell.

Answer: All of these

Once the viral core has gained entry into a host cell, the RNA and various enzymes are released into the cytoplasm. Reverse transcriptase then acts upon the viral RNA, turning it into a single strand of DNA, and copies the single strand to produce the double strand required for viral replication.

The viral enzyme intergrase then inserts the viral DNA into the human DNA strands inside the nucleus of the host cell. The viral DNA can then use the host cells mechanisms to produce mRNA which results in the cell replicating viral RNA and enzymes which in time will turn into new virions. Once the virion is released from the host cell, protease enzyme causes the proteins inside the cell to mature. Once this is complete, the virion is ready to infect a new cell.

Answer: Seroconversion

Seroconversion occurs within 4 to 8 weeks after initial infection, when HIV inside host cells starts to bud and mature. Once the virus is released into the blood stream it elicits an immune response. During this time the person may experience the flu like symptoms common to all acute viral infections.

This is called Seroconversion Illness. Once the immune response is activated HIV antibodies are produced and the infected person will test positive in an HIV antibody assay (ELISA).

Answer: Enzyme-Linked Immuno Sorbent Assay

ELISA or the Enzyme Immuno Sorbent Assay is a technique used to detect the presence of a specific antibody or antigen in a sample. This is the most common and least expensive method for detecting HIV antibody in a person wanting to find out their HIV status. ELISA tests can either be conducted at a laboratory or as a rapid "home style" test.

The ELISA test detects the presence of HIV antibody so it will be inaccurate if the person is in the Window Period (has not yet seroconverted, therefore has not started to produce antibodies).

Answer: The window period

Traditional HIV diagnostic tests such as ELISA are designed to recognise the presents of HIV antibody. At initial infection the virus is undetectable as it is inside the host cell and the immune system is unable to react to antigens on the viral membrane. Only once the virus starts to "bud" or leave the host cell is the immune system able to access the virus and start producing HIV antibody.

The period when the virus is "under cover" is called the Window Period, and usually lasts between 4 to 8 weeks.

This means that during this initial stage of infection the person will test negative in an antibody assay even though they are in fact infected with the virus.

Answer: Decrease viral load by interrupting the function of the enzymes responsible for viral replication.

There are several categories of ARV (Anti Retroviral) medication. All of them affect the functioning of one or more of the enzymes or proteins responsible for viral replication. Nucleoside Reverse Transcriptase Inhibitors (NRTI's) such as AZT and 3TC act on reverse transcriptase and mimic the normal building blocks of HIV DNA. Non- Nucleoside Reverse Transcriptase Inhibitors such as Nevirapine directly inhibits reverse transcriptase, disrupting the process of RNA to DNA synthesis. Protease Inhibitors such as Indinavir and Saquinavir act by inhibiting protease, which interrupts maturation of immature HIV virions. Finally Fusion Inhibitors bind to gp41protiens on the viral membrane preventing the virus from binding to CD4 receptors on the prospective host cell.

All the information in this quiz is referenced from Alta van Dyk (2008) "HIV Care and Counselling. A Multidisciplinary Approach". 4th Ed. Pearson Education. South Africa (ISBN978 1 7702 5171 7)