An is the western blot. HIV antigen

An ELISA can be used to detect HIV. It is highly sensitive,
very accurate, widely available and can test a large number of samples at once
(health24, 2016). A commonly used ELISA is the indirect method, when HIV
antigen is placed in a 96 well plate, an antibody is inserted which will react
with the HIV antigen. The plate is washed and conjugate is added that can bind
to specific antibodies attached to the HIV antigen. After incubation and
washing, substrate is added that binds to the conjugate on HIV antigen-
antibody complexes and results in colour development which can be detected on a
spectrophotometer to find specific HIV antibody concentrations (HIV InSite,
2006). ELISAs are performed in a laboratory which means it can take a while for
results to be obtained. It is normally an accurate test with very few false
negative results produced, but false positives can be produced, meaning a
person can be wrongly diagnosed. If this occurs another ELISA should be performed
for the correct diagnosis. This can be time consuming and isn’t cost effective
(health24, 2016).  
Another technique that can be used is the western blot. HIV antigen is placed
on a polyacrylamide gel which is electrophoresed making the antigen proteins
migrate through the gel at different rates due to their molecular weight. The smaller
the molecular weight the further the proteins migrate. Once they have migrated
through the gel bands will form that are blotted onto nitrocellulose paper. This
paper is incubated with a primary antibody, washed and then incubated with a conjugated
secondary antibody which will react with specific HIV antigen-antibody
complexes to produce coloured bands. The sample is positive for HIV if the
bands on the paper are the characteristic band pattern for HIV (HV InSite,
2006).  Sometimes bands can be
indeterminates, where the band pattern isn’t the exact characteristic band
pattern. If this occurs another western blot should be performed otherwise it
could lead to misdiagnosis of a patient. This is more time consuming as only a
small amount of samples can be tested at one time (Fearon, M., 2005).

A treatment regime that can be used is a
nucleotide/nucleoside reverse transcriptase inhibitor. This disrupts the
formation of new DNA by the virus because instead of taking up a normal
nucleotide from the cell, the reverse transcriptase may take up a nucleotide/nucleoside
inhibitor instead. These inhibitors have a different structure to the nucleotides
present in the cell so the virus is not able to form chemical bonds required
for the formation of DNA therefore, the virus cannot be replicated, helping to
slow down the infection (Aidsmap, 2018).

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The first step in the defence against an infection is the
non specific, innate immune system. The virus passes through the physical
barriers such as the skin and then it encounters macrophages (CNAzone, 2016). HIV
is able to bind to the macrophages and infect them, making them lose their
ability to ingest and kill the virus so HIV proceeds to bind to dendritic cells
and get transported to the lymph nodes and the rest of the body, spreading the
infection. Because the virus is too strong to be destroyed so far it can enter
the host cell and this activates the complement cascade. In the cell synthesis
of viral proteins begins and degraded protein fragments from the HIV can be displayed
on MHC I which is recognised by the T cell receptor CD8.  CD8 can bind to the MHC I and activate T cells
to lyse the infected cell and secrete cytokines that can inhibit replication of
the virus and block entry into CD4 T cells. However this is ineffective in
destroying all of the infection so HIV enters the CD4 T cells and the adaptive
immune response is activated. Antibodies specific to gp120 and gp41 are made
and bind to these receptors to neutralise or destroy the virus (British Society
for Immunology). Although this is effective in destroying HIV, the virus is
able to replicate rapidly so by the time antibodies specific to the viruses receptors
have been made, the infection has spread rapidly. The virus can also mutate rapidly,
causing the variable regions to change shape so antibodies are no longer
specific (CNAzone, 2016).

HIV is a round enveloped virus which has proteins gp120 and
gp41 on its surface (, 2017). Inside the capsid of the virus are two identical
single stranded RNA molecules. The virus has three important enzymes used to
invade host cells which are reverse transcriptase, integrase and protease
(Rediscovering biology, 2017). The first step of transmission is when the gp120
from the virus binds to the CD4 receptors on the host cell. Gp41 from the virus
binds to the host cell surface and makes a channel between the two, inserting into
the plasma membrane of the host cell allowing the virus to transfer its RNA
into the host cells cytoplasm. Reverse transcriptase transcribes the RNA from the
virus into DNA which is then transported into the nucleus of the host cell by integrase.
Because the viral DNA is now in the nucleus of the host cell, it can be
replicated during cell division (German Advisory committee blood, 2016). Nef
protein from the virus is able to stop the host cell from making proteins essential
to cell defence so the cell isn’t able to fight back against the infection (PBD,

The human immune deficient virus (HIV) weakens the immune system
by attacking CD4 T cells (COHERE, 2012), the cell count becomes so low that the
immune system cannot fight the infection leading to it becoming more susceptible
to opportunistic infections (CSC’s HIV basics, 2017). This may lead to acquired
immune deficiency syndrome (AIDS), which can be life threatening. AIDS is a characteristic
set of symptoms resulting from the opportunistic infections damaging the immune
system. If a person with AIDS isn’t treated it could lead to death (Avert,
2018). There are two types of HIV: type 1 and type 2. Most infections are caused
by type 1 as it has a faster transmission rate and is more virulent. It is
increasingly prevalent in developing countries and has become pandemic, whereas
type 2 is endemic to primarily West Africa (Reeves & Doms, 2001). There are
three stages to a HIV infection, the first is the acute stage where the virus
is rapidly replicating (CDC, 2017), people normally have flu like symptoms
including fever, fatigue and swollen lymph nodes that can last up to several
weeks (CDC’s HIV basics, 2017). In the clinical latency stage the virus is
reproducing less and can last up to a decade or more. The last stage of the
infection can lead to AIDS. Symptoms include rapid weight loss, pneumonia and
extreme tiredness. Sometimes people with HIV participate in high risk
behaviours (CDC, 2017), the most common high risk behaviour is unprotected sex
(McGowan et al, 2004), other include sharing infected needles and sometimes
blood transfusions.

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