Module 5-2 - HIV Flashcards
How big is the HIV issue?
1 in 7 do not know they have it and over 1 million in the US have it alone
Globally 37.9 million have it and 32 million have died
In what groups has the highest Incidence of HIV?
African American gay and bisexual men, but Latino gay and bisexual men have increased in incidence over time
What area of the US has the largest incidence of HIV?
The South (52%)
What does HIV stand for?
Human Immunodeficiency Virus
What does AIDS Stand for?
Acquired Immunodeficiency Syndrome
It is the late stage of HIV and is the disease caused by it
What is the structure of an HIV viral particle?
Oval Shaped Protein Coat
Capside with RNA, enzymes, P24 Protein, and P17
Envelope with the lipid layer, GP120 and GP41 - Glycoproteins sticking out of the lipid membrane
What is special about the HIV P24 protein?
This protein serves as an antigen that we can test for antibodies and for the the virus presence/antigen
GP120 and GP 41
Glycoproteins that are like spikes sticking out of the lipid membrane and aids HIV in getting into cells
What is one of the components of HIV that makes it unique?
It contains reverse transcriptase enzyme
Most viruses cannot…
replicate on their own, they need to be in a cell to reproduce
Retrovirus
HIV
it inserts itself as vRNA and makes DNA from the vRNA, and then splices the vDNA into the genetic material of healthy cells
So, it enters the hosts genetic material causing a permanently infected cell
What does a new virus take from an infected cell when leaving?
It takes the phospholipid bilayer for itself
Capsid
The protein shell of a virus containing its genetic material
It has 2 strands of RNA, Reverse Transcriptase, and P17 and P24 proteins in it (in HIV)
Envelope
Lipid bilayer containing the virus and capsid that has GP120 and GP41 sticking out of it (in HIV) allowing access to cells
Made from the host cells membrane as it left the cell
How exactly does a retrovirus infect cells?
The GP120 and 41 on the surface allow it to bind to CD4 receptors on T4 cells and then inject its contents into the cytoplasm
The contents (2 RNA strands and reverse transcriptase) can then be used to make DNA
What aspect of HIV causes the immune deficiency disorder?
The fact that it infects and hurts T4 cells (thus hindering the immune response)
What occurs once reverse transcriptase uses the viral RNA to make DNA?
The DNA then goes from the cytoplasm into the nucleus, and along with other viral enzymes, inserts itself into the host cell genome
Once vDNA is inserted, its there permanently and the cell is infected and no longer your own
RNA can then be made using the DNA to make virions using the cells machinery
What can occur after the vDNA has entered the genome?
It can either go latent or activate and begin making viral particles (RNA and RTranscriptase)
Latent
A virus that inserts itself and remains dormant, not producing new viral particles
It can do this if there is not the right kind of GP on the surface or if the formation of a capsid hasn’t progressed to maturity yet for example
What happens once vDNA activates to make new Virions?
Proteases will cleave proteins made by viral mRNA and package them into a protein coat
The viral particles can then be put into the protein coat to make the immature capsid
The capsid can eventually make an envelope using the phospholipid bilayer of the cell and bud off the membrane to go make more infected cells and copies
Thera re classes of HIV meds addressing…
every step of HIV reproduction
What happens since the new virion takes a chunk of the membrane with it?
It will have GP120 and GP41 on its surface of the envelope
Can then connect to CD4 on other T4 cells and invade as a result
Where do the names of GP120 and GP41 come from?
their molecular weight
Why can T8 cells have difficulty killing virus infected cells?
If the virus DNA is already in the nucleus, the T8 cell cannot identify that the cell is infected unless the virus is actively replicating already
HAART
Highly Active Antiretroviral Treatment
HIV treatment method
It involves hitting the disease fast and hard as soon as you learn of infection with drugs that will eradicate it ASAP - its trying to prevent viral particles from seeding and allowing reproduction later
Seeding
When the viral DNA goes dormant and remains undetected and safe until it can widely disseminate and activate
Because of seeding, it is important to destroy all viral particles before seeding occurs to allow greater survival probability
Wanna stop this fast and early
Summation: Stages of Viral Replication
- HIV binds to the CD4 cell on T4 cells and RNA, proteins, and enzymes released into cytoplasm
- HIV Reverse Transcriptase converts vRNA into vDNA
- HIV vDNA then moves to the host nucleus and is spliced into the host genome/DNA
- HIV vRNA moves out of the nucleus to the cytoplasm and makes long chains of viral proteins and enzymes
- Immature viral particle forms containing cellular and HIV protein. Chains cut into smaller pieces by protease
- Infectious viral particle is now ready to be released containing HIV RNA, viral proteins and enzymes
The function of the immune system?
Function = Prevent/Fight Disease
It controls of eliminates viruses and other microbes that threaten the body with infection and disease
It eliminates damaged cells that are or may be cancerous
The immune system is divided into two branches…
- Antibody Mediated –> Copes with disease causing microbes in the blood
- Cell Mediated –> Copes with microbes located within cells
When does Cell Mediated Response v Humoral Response get to the viral particles compared to each other?
Humoral response get to the virus before it even enters the cell and cell mediated gets there after
What is so important about CD4 cells and HIV?
CD4 cells (Helper T Cells) coordinate and activate both B lymphocytes (antibody mediated) and cell killing cytotoxic (CD8) lymphocytes (cell mediated) - the cell mediated response copes with microbes located inside cells like viruses
However, HIV can infect and destroy CD4 cells (gets your body to attack the Helper cells since they are infected) –> loss of CD4 means the immune system will collapse with HIV disease
What is used as a marker of the progression of HIV?
Decline in (Absolute) CD4 cells
When are CD8 cells important for HIV infection?
In the initial immune response to HIV and the latent stage
What do CD8 cells do?
They kill infected cells that are producing virus
What can CD8 cells do to prevent HIV replication?
- They can kill the cell
- They can secrete soluble factors that suppress HIV replication by blocking and occupying receptors needed for the entry of certain strains of HIV into the target cell
What are the two issues that exist with HIV and CD8 cells ?
- If the CD8 cannot get the job done early enough, the HIV virus can seed, and once latent the CD8 cells cannot detect them until its too late
- New info shows 2 new strains of the HIV virus that target CD8 cells as well as CD4
If CD4 cells are infected with HIV, what occurs with CD4 cells to lead to increased susceptibility to opportunistic and other infections?
CD4 can not make interleukins to stimulate an immune response –> loss of stimulus for T and B cell activation occurs –> lymphopenia, decreased CD4/Cd8 ratio, and decreased delayed hypersensitivity –> increased risk
If CD4 cells are infected with HIV, what occurs with CD8 cells to lead to increased susceptibility to opportunistic and other infections?
CD8 cells have impaired feedback and cytotoxic activity since they cannot get orders from CD4 –> lymphopenia, decreased CD4/Cd8 ratio, and decreased delayed hypersensitivity –> increased risk
If CD4 cells are infected with HIV, what occurs with Macrophage cells to lead to increased susceptibility to opportunistic and other infections?
Macrophages have decreased chemotaxis, phagocytosis, IL-1 production, and ability to present antigens to cells (d/t no T4 response) –> Increased risk
If CD4 cells are infected with HIV, what occurs with B cells to lead to increased susceptibility to opportunistic and other infections?
B cells have diminished antibody production in response to antigens and decreased production of immunoglobulins –> decreased nonspecific serum immunoglobulin –> increased risk
Why does a drop in ratio between CD4 and CD8 cells cause delayed hypersensitivity?
It is referring to Type IV hypersens. (no antibodies)
There is no T4 stimulation leading to not enough T8 cells reacting to something to have an immune response happen
Absence of an immune response may mean…
either you do not have an infection or you could have no immune system
Anergy
No immune system and cannot mount an immune response
Why may we want to give an HIV patient a Tb test?
It is a common comorbidity
If we give the test and wait for the response and there is none, then they may not have enough T8 cells rather than not have Tb
What is a way to check if you have no immune system (anergy) or no exposure?
Expose them to yeast / yeast mold antigen which almost everyone has been exposed to
If they react to the yeast injection, they have no been exposed to Tb and have an immune system, but if they are Anergic they will not react to the yeast either
Which Interleukin is important for Chemotaxis?
IL-1
Why does macrophage presenting ability decrease with HIV?
T4 cells are not producing the needed cytokines that are supposed to amplify and stimulate and immune response
Those with HIV end up with strange rates of…
cancer and infection
What is HIV replication rate like?
Crazy fast early on - billions per day with a high mutation rate (3300 mutants made per day)
99% of HIV in the blood is from newly infected cells
30% of HIV in plasma is replenished daily
How many days does it take for HIV entire population turnover?
14 days
What is the mutation rate of HIV?
1 in 3 replication cycles - 3300 mutant viruses per day
When does extensive HIV seeding occur?
early in the disease process
CD4 only has a lifespan of 1-2 days so if HIV is not taken care of early then the extensive seeing will occur
Sanctuary Sites
Body has a difficult time detecting HIV in these areas
HIV gets to these areas by going inside macrophages and crossing into the CNS to cause dementia (like a macrophage trojan horse)
These are the dendritic cells of the lymph nodes and glial cells of the CNS
Lifespan of a CD4 Cell
1.2 days (billions made, infected, and destroyed daily in HIV)
What happens to T4 cell levels over time with HIV?
The T4 infected cells will eventually be attacked by CD8 cells killing them and infected macrophages
Eventually you run out of T4 cells to keep up with viral replication rate
Transmissible Body Fluids for HIV
Blood
Semen
Vaginal Secretions
Breast Milk (so this is contraindicated in HIV+ women)
Cerebral Spinal Fluid
Synovial Fluid
Pleural and Amniotic Fluid
Non Transmissible Body Fluids for HIV
Urine
Sweat
Saliva
Tears
Vomit
Mucus
Feces
The virus can be found here but not transmitted here
How can vertical transmission of HIV be very low?
IF the mother is compliant with medication regimen
2-8% rather than 15% without (or 29% to 2% with AZT treatment)
Methods of Transmission for HIV
- Unprotected sex - oral, anal, vaginal
- Blood to blood contact - sharing needles, occupational exposure, fighting, tattooing, body piercing, transfusions
- Mother to newborn - in utero, childbirth, breast feeding
Risk Factors for HIV Infection
Sexual Activity
Injection Drug Use
Recipients of Blood Products (1975- March 1985)
Hemophiliacs who received Pooled Plasma
Children of HIV Infected Women
Needlestick accidents
How many children of HIV infected women will be infected without treatment?
30%
What is used to immediately treat post exposure needlestick accidents?
Retrovir (Zidovudine) - given ASAP within 24 hours!
What is the greatest HIV transmission risk?
Receptive Anal Intercourse (receptive meaning semen stays inside, and the membranes tear in this case)
there is a 95% chance of getting it from HIV infected blood donors but this rarely occurs nowadays
What is the least HIV transmission risk?
Insertive Vaginal intercourse is 1/10,000 chance (insertive meaning penis goes in but ejaculate was not)
There is a 1/1,000,000 chance to get HIV from screened blood though
Other Factors that increase HIV Risk?
- Acute infection about 12 weeks after HIV contraction makes transmission likelihood 26x more likely
- Other STIs can amplify risk x8
- Exposure to gender inequality and intimate partner violence can raise a womans HIV risk x1.5
Why is it that your HIV transmission risk is 26x more 12 weeks after contraction (during acute infection)?
the viral load has skyrocketed during the acute phase is why
Other factors that decrease HIV risk?
Circumcision (60%) lower in hetero males
Treatment as prevention
Pre exposure prophylaxis
Condoms (80% lower)
Only having intercourse with someone of the same sero status (HIV-HIV, Negative-Negative)
Tests for HIV
ELISA
Western Blot
p24 Antigen
Absolute CD4+ Lymphocyte count and CD4 Lymphocyte Percentage
HIV Viral Load Tests
CBC
DNA - Viral nucleic acid tests
Viral Culture
Immunofluorescence Antibody Testing
Urine and Saliva Serologic Testing
Home Testing
ELISA Testing
Enzyme Linked Immunosorbent Assay
Determines response of antibodies to HIV Virus
Used in children older than 18 mo
High sensitivity with low specificity - so lots of false positives
There is a plate of viral particles mixed and if there is antibodies they will bind to the antigens on the bottom of the plate, then if more antibodies that change color are added then it is a positive case
If blood washes off and no color change occurs it is negative
What is ELISA good as?
A Screening Test
High sensitivity means it can rule out those without HIV but low specificity means you can have a lot of false positives
Western Blot Testing
Confirms the presence of HIV Antibodies and is more specific for HIV
Useful children 18 mo and up
Positive HIV antibody test in children younger than 18 mo only indicates the mother is infected