Week 2 - E - HIV - What, How, WHo, Opportunistic infections, diagnosis Flashcards
What does HIV stand for? WHat does untreated HIV cause?
Human Immunodeficiency virus - HIV
Untreated HIV causes AIDS Acquired immunodeficiency syndrome
What percentage of all deaths of people living with HIV is caused by AIDS?
1/4 of deaths in people living with HIV is caused by aids (due to a late diagnosis of HIV)
Does HIV decrease the life expectancy of patient?
Patients with a diagnosis of HIV have a normal life expectancy - treatment is very good nowadays
HIV 1 and HIV 2 HIV 1 originated in west african most likely by the common chimpanzee HIV 2 originated also in west africa by the sootey mangabey WHich type of HIV is msot widespread worldwide and most infectious?
HIV 1 is more worldwidespread and is more infectious than HIV 2
HIV 1 likely inferred origiin was the common chimpanzee in West africa
What type of virus is HIV?
HIV is a retrovirus
What is a retrovirus?
This is a single stranded RNA virus than once infecting the host cell, it goes back to DNA using its reverse transcriptase enyzme to produce its own DNA copy from its RNA genome
What are the target sitesfor HIV? What are the main cell type that expresses these receptors?
The target cells are the CD4+ receptors
The main cell type expressing these receptors are the T helper lymphocytes (CD4+ cells)
What cells other than the T helper lymphocytes express CD4+ receptors?
Dendritic cells
Macrophages
Microglia
T helper lymphocytes express the CD4+ receptors and HIV binds to the CD4+ receptors and then enters the lymphocytes WHat is CD4+ again? What cells express the CD4+ recpetors?
It is a glycoprotein found on the surface of a range of cells
- T helper lymphocytes
- Dendritic cells
- Macrophages
- Microglia
What do CD4+ Th lymphocytes do?
These cells are essential for the adapative immune response - specific immune response
Adaptive immunity also includes a “memory” that makes future responses against a specific antigen more efficient.
What is the non-specific immune response that comes to play within hours of the ntigen presenting itself to the body?
This is the innate immune response
CD4 cells (These are the T helper lymphcoytes that experess the CD4 receptors) help orchestrate the immune response and recognize the MHC2 APC (antigen presenting cells) WHat do CD4 cells do once the MHC2 antigen presenting cell binds to it? (three things)
- They activate B antibodies
- They activate cytotoxic T cells (CD8+)
- Activate cytokine release
When CD4 cells aren’t working, their can be a lot of problems with the immune system
HIV infection has a big effect on the immune response It causes sequestration of the CD4+ cells in lymphoid tissue - what does this mean?
This means there is an accumulation of CD4+ cells in lymphoid tissue and therefore a reduced circulating CD4+ cells to help fight infection
HIV also causes Reduced proliferation of CD4+ cells Reduction CD8+ (cytotoxic) T cell activation How does it also decrease the affinity of antibodies produced?
It causes a reduction in antibody class switching - therefore cant change the antibody produced so a decrease in the likelihood of antibody combining to the antigen
As stated HIV has many effects on the immune response Reduction in circulating CD4+ cells Reduction in proliferation of CD4+ cells Reduction inCD8+ (cytotoxic T cells) activation Reduction in antibody class switching which reduces the affinity of antibodies produced What does all this make the person more suceptible to?
- Viral infections
- Fungal infections
- Mycobacterial infections
- INfection-induced cancers
What are the normal parameters of CD4+ Thelper lymphocyte cell count? What is the threshold for opportunistic infection?
500-1600 cells/mm3 is the normal parameters for Thelper lymphocyte cell count
Threshold for opportunistic infection is when the count is <200cells/mm3
There is rapid replication in very early and very late HIV infection How often does the HIV virus replicate in early infection?
HIV virus replicates every 6-12 hours in early infection
After being infected with the HIV virus, 80% of people develop symptoms when?
80% of people develop symptoms within 2-4 weeks of being infected with the virus
After the acute HIV stage, what is the next stage in the HIV infection? How long oes the asymptomatic HIV stage tend to last?
This is the asymptomatic HIV infection stage where there is ongoing viral replication without symptoms with a decreasing CD4 cell count
Lasts roughly 8ish years
Early on huge amounts of virus replicated and CD4 count therefore decreases There is then a small immune response to the HIV where the viral load decreasesThen the HIV slowly continues to replicate before AIDS related conditions causes a massive spike in viral load at the end
What is the CD4+ cell count when the aids related condition kicks in? Without treatment,what is the avergate time until death?
Usually below 200cells/mm3
Average time until death is approx 9-11 years without treatment
Commonest transmition is in the mucosal CD4 cells The muscosal CD4 cels take the virus into circulation and transport to regional lymph nodes How long does the virus take to infect the CD4 cells DNA and therefore how long do you have to give post exposure prophylaxis treatment?
The virus takes about 3 days to infect CD4 cells
DNA and therefore have up to 72 hours to start post-exposure prophylaxis treatment 3 days after the virus has established itself into the CD4 DNA, get the huge rapid spike in DNA replication and dissemination of the virus
As stated, up to 80% of people present with symptoms 2-4 weeks after initial infection What are the combination of symptoms in the primarry infection stage?
Most people experience sort of flu like sympotms in this time period
- Fever
- Rash
- Myalgia
- Pharngitis
- Headache
A young woman is contacted by the public health nurse and informed that one of her sexual contacts tested positive for HIV. The young woman comes into the clinic to be tested. She tells the nurse that she has heard that people who are infected with HIV have a period when they test negative even though they are very infectious.
What is this period called? a) infectious stage b) primary infection c) viral set point d) window stage
b) primary infection
What type of rahs appears in the primary infection of HIV? Are people infectious at this stage?
People usually get a widespread maculopapular rash
There is a very high risk of transmission at the primary infection stage
In the asymptomatic phase there is ongoing viral replication causing ongoing CD4 count depletion until opportunistic infection occurs
Define an opportunistic infection Opportunistic infections include - PCP, TB, Toxoplasmosis, Cytomegalovirus, skin infections etc
An infection caused by a pathogen that does not normally cause infection in a healthy individual
It uses the opportunity of a weakened immune system to cause disease
What is the fungus like lung infection that is not commonly found in the lungs of healthy people, but, being a source of opportunistic infection, it can cause a lung infection in people with a weak immune system? It is the most common opportunistic infection in people with HIV infection
This is pneumocystis pneumonia (PCP)
WHat bacteria causes pneumocystic pneumonia? What are the symptoms? What is the CD4 threshold?
Caused by penumocystic jirovecii
Get a dry cough, SOB and oxygen desaturations on exercise
CD4+ threshold is less than 200cells/mm3
How is the diagnosis of PCP carried out? CXR may be normal but when abnormal Get the interstitial infiltrates (can look like cardiac failure but without the cardiomegaly)
Bronchoealveolar lavage (BAL) and immmunoflouresence - this is basically when a fluid is squirted into the lungs via a bronchoscope and then aspirated and examined under immunoflouresence
HIV can cause reactivation of toxoplasmosis infection - this infection is lifelong and lies latent but is an opportunistic infection Toxoplasmosis releases trophozoites that migrate mostly to eye, brain and muscle What parasite causes toxoplasmosis? What is the CD4 threshold? What are the signs (CT) and sympptoms?
Caused by toxoplasmosis gondii
CD4 threshold is usually lower than 150cells/mm3
Get focal neuropathy - headaches, seizures, reduced consciousness, raised ICP, fever
Can see multiple cerebral abscesses on CT scan
CMV can cause retinitis, colitis and oesophagitis commonly What are the symptoms of infection usually? What is the treatment?
Symptoms usually include reduced visual acuity and floaters in the eye
Abdo pain and diarrhoea
Treatment is IV ganciclovir
What is the difference between condyloma acuminatum and condyloma lata?
Condyloma acuminatum is genital warts caused by HPV (usually types 6 and 11 amongst others)
Condyloma lata is very infectious cutenous lesions in the secondary stage of syphilis - usually painless raised lesions
What is the wasting syndrome linked to HIV known as? It is where there is HIV related cachexia (Cachexia or wasting syndrome is loss of weight, muscle atrophy, fatigue, weakness, and significant loss of appetite in someone who is not actively trying to lose weight.)
This is slim’s disease
What organism causes kaposi’s sarcoma? What does this sarcoma look like? What is the treatment?
- Kaposi’s sarcoma is caused by human herpes virus 8
- It is a vascular tumour which presents with red/brownish lesions
- Treat the sarcoma by treating the HIV - HAART
EBV can cause Burkitt’s lymphoma and primary CNS lymphoma - both types of non-hodgkin’s lymphoma Usually presents at more advanced HIV What is different about the cancer cells in non-hodgkins and hodgkins lymphoma?
A doctor can tell the difference between Hodgkin’s lymphoma and non-Hodgkin’s lymphoma by examining the cancer cells under a microscope.
If the doctor detects the presence of a specific type of abnormal cell called a Reed-Sternberg cell, the lymphoma is classified as Hodgkin’s.
How many patients with HIV are found to be anaemic? What type of thrombocyopenia should you give a HIV tests in? (also give test if persistant thrombocytopenia, neutropenia and leucopenia) What is thrombocytopenia?
Anaemia affects up to 90% of patients with a HIV infection
If diagnosing somebody with idiopathic thrombocytopenia then they should be given an HIV test
Thrombocytopenia is when there is a low platelet (Thrombocyte) count
If there is a clinical symptoms of HIV, should have an HIV test regardless of whether you think it was HIV or not His HIV test was positive and CD4 count was 191 What does this CD4 count mean? 8 years prior turns out Alan had had pharnygitis, and a skin rash, what does this show?
This CD4 count means he is at risk of opportunistic infection
This 8 year prior symptoms shows he may have had primary infection symptoms of HIV at the age of 19
