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PYC2605 Study Notes
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PYC2605 Summary Notes
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PYC2605 This document is an editable PDF document which contains questions and answers from past exam papers from 2015 up until 2020, as well as many extra assignment questions and answers.
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PYC2605NOTES
, CHAPTER 1: HIV and AIDS – A brief history
1.1 The birth of a new epidemic
Aids was first reported in South Africa in 1983, and it was diagnosed in two
homosexual men
Dr. Luc Montagnier of the Louis Pasteur Institute in France discovered the virus
causing AIDS in 1983
Dr. Robert Gallo of the US propagated the virus in cell culture in 1984, and also
played a huge role in the discovery of the first HIV antibody tests, which became
available in 1985
AIDS is short for Acquired Immunodeficiency Syndrome; the disease is acquired
because it is caused by a virus (HIV or the human immunodeficiency virus)
Immunodeficiency refers to the inability of the immune system to defend itself
against infections
A syndrome is a medical term for a collection of specific signs and symptoms
that occur together and that are characteristic of a specific condition
1.2 The origin of HIV
Little is known about the origins of any human virus, let alone HIV
Many theories were disproved over the years, however the idea that the virus
crossed the species barrier from primates to humans was correct
It was discovered that HIV (the human virus) was related to SIV (the simian
immunodeficiency virus), found in primates
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, As seen in Figure 1.1, HIV can be further divided into HIV Type 1 and 2
HIV-1 has been classified into 3 groups: M (major), O (outlier) and N (non-M
and non-O)
The world epidemic is currently dominated by the M HIV-1 viruses
The dominant virus in Southern Africa is HIV-1 subtype C
HIV Type 2 (HIV-2) is mostly restricted to West Africa
HIV-2 is less pathogenic than HIV-1, and its progression to disease is slower
An ancestor of HIV-1 group M virus was transmitted from a chimpanzee,
sometime around the 1930s, in equatorial West Africa
HIV-1 group N probably originated from gorillas
HIV-2 groups A,B and G originated from the sooty mangabey monkeys
1.3 The global AIDS epidemic
Sub-Saharan Africa remains the most heavily affected region in the world
HIV incidence is the percentage of new cases of infection in a defined
period of time (usually in one year); this percentage is calculated by dividing
the number of new infections by the number of previously uninfected people
HIV incidence is very difficult to measure
HIV prevalence is the percentage of people living with HIV (as a proportion
of the total population) at a specific time
HIV prevalence is measured based on data from a combination of the
following surveys: antenatal clinic surveillance of pregnant women,
population and community-based surveys, studies among specific groups
who are involved in high-risk behavior and reports of AIDS-related deaths
Antenatal (pre-birth) surveillance programme involves the annual testing of
the blood of pregnant women in the public health sector who visit antenatal
clinics
The surveillance is anonymous and unlinked
National household surveys consist of testing large samples of the national
population, with their informed consent; those surveys are useful for assessing
HIV trends in a country and for providing the prevalence of HIV in terms of
age, sex, race and geographical areas
It is impossible to know exactly how many people are infected with HIV at
any given time, and only estimates can be given
1.4 The world’s response to the AIDS epidemic
In South Africa, AIDS was seen by the apartheid government as a ‘gay’
disease, that would ‘sort itself out’
The first major step was the creation of the National AIDS Convention of
South Africa (NACOSA) in 1993
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, The Mandela government refused to provide AZT to pregnant women to
prevent mother-to-child transmission in 1998 (four years after it was proven
to be successful in the USA)
During the Mbeki era, antiretroviral therapy was refused for pregnant
women; eventually, in 2002, the South African High Court ordered the
government to make nevirapine available to pregnant women, to
prevent mother-to-child transmission of HIV
New clinical guidelines for the management of HIV and AIDS, as well as
guidelines to prevent mother-to-child transmission, were implemented on
1 April 2010
Worldwide, no other virus has led to so much research and new
developments than HIV
In 1994, AZT (Zidovudine) was the first drug to be used for antiretroviral
therapy, and it was recommended to pregnant women infected with HIV
in the USA
In 1995, the use of combination antiretroviral therapy or HAART was
introduced, and two years later, the number of deaths due to AIDS began
to decline in developed countries
Great effort was put into developing ways to prevent HIV infection, such
as vaccine research, the development of an effective microbicide and
male circumcision research
CHAPTER 2: HIV and the Immune System
2.1 The Immune System
Has several lines of defense
The first line of defense of the body is made up of the physical barriers
(e.g. the skin), which are non-specific defenses (they will not keep
pathogens out)
The second line of defense: when the skin is broken and pathogens enter
the body, there will usually be an inflammatory reaction at the area of the
entry
The inflammation is a wake-up call for the innate immune system to take
over and deal with infectious agents or pathogens that entered the body
(also a non-specific response)
The innate immune system consists of plasma proteins and white blood
cells (leukocytes)
Plasma proteins identify invaders, assist antibodies with killing pathogens,
call phagocytes (‘eating cells’) to the site of infection (so that they can
eat the invader) or directly attacking and killing the enemy; one of the
best known plasma protein is interferon (usually produced when the body
is infected by a virus)
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