Sexually transmitted infections Flashcards
Describe the structure Human Immunodeficiency virus
what is around the virus? what is present on this? important ones?
what is the viral nucleic acid? how many copies?
important proteins (3)
Virus has an envelope
Viral proteins are present on the envelope
Important ones are glycoprotein 120 and glycoprotein 41
There are some host cell proteins on the envelope
Viral nucleic acid is RNA
There are two copies of the RNA
Other important proteins include reverse transcriptase, integrase, protease
Describe replication cycle of Human Immunodeficiency virus
what does HIV bind to? what other receptor too?
what viral protein is used for attachment? what then changes shape? effect of this?
now what happens? what is lost?
how does the rna use reverse transciptase? effect of this?
what is made? what does it become? where does it go and what does it do there?
what is the effect of this and what is made? where? where do they go next?
HIV binds to the CD4 receptor on cells
Another receptor, the chemokine receptor, is also used
The viral protein used for attachment is the gp120
Then the gp41 changes shape and helps the virus to fuse with cell membrane
Virion enters cell
Loses envelope
Viral RNA is reverse transcribed to DNA
Complementary DNA, cDNA, is made
The cDNA is made into a double stranded copy
This becomes circular
Travels to nucleus
Integrates into host DNA
Viral messenger RNA made In cytoplasm translated to proteins Virus capsid made Some proteins glycosylated Travel to cytoplasmic membrane Virus buds off
How does the virus kill cells
what does the virus mainly infect?
what brings attention to TH attention?
what recognise these atnigens?
what is made once recognised? what else is made? what happens to cell?
what speeds up virus replication? outcome of this?
Virus mainly infects Thelper cells.
There are cells that function as assistants to Th cells
Antigen presenting cells
They bring the antigen to Th cells attention
The Th cells use molecules on their surface called T cell receptors to touch and recognise these antigens
Once they recognise the antigens they make interleukins IL2
They also make interleukin receptors
The cell is activated
If this cell is infected with HIV and the cell is activated, virus starts to replicate fast.
Virus proteins are made fast
Out come is cell death
Diagnosis of HIV
General clinical manifestations Fever Lethargy Malaise Headache Sore throat myalgia
clinical diagnosis (too general)
Headache Other neurological symptoms Gastrointestinal diarrhea Rash Urticaria Loss of hair Ulcerations in mucocutaneous areas
Lab diagnosis
what is detected? (2)
if positive what do you do?
whats the next test?
Fourth Generation HIV test.
Detects HIV antibodies and an HIV antigen p24
If positive, do a second assay to confirm
Then carry out a PCR to look for viral RNA
Learning Objective - Outline the epidemiology of sexually transmitted virus infections
what is distrubution like?
difference over the years?
The key point to learn about the statistical data shown is that worldwide there are a large number of HIV infected people.
The number has lowered in the last few years.
You don’t need to remember the numbers.
Remember there are some areas in the world that the incidence of infection is higher.
You don’t need to remember the exact locations.
Herpes simplex virus - durations
3 different phases?
duration of viral shedding?
recurrence - viral shedding? heal?
days 0 - 6 = vesicular pustule
days 6 - 12 = wet ulcer
days 12 - 20 = dry crusts
duration of viral shedding = 12 days
FOR RECURRENCE
viral shedding = 5 days
healed = 12 days
Herpes virus - how it works
what happens after the lesion is healed?
what causes a recurrent infection?
After the lesions have healed, there is establishment of the latent infection in the dorsal root ganglia innervating the mucosal areas involved in acute infection
The virus is on the skin until it migrates up inside the axon to the dorsal root ganglion. Then, at any time, the virus can start replicating again and migrates back down the axon towards the skin where it causes a recurrent infection
Herpes virus - latency + activation
what is latency?
what is reacrtivation?
Latency- Virus replication stops and very few virus proteins are made
Reactivation- There is release of the latent virus from the infected ganglia, this causes infection of the epithelial cells, leading to a recurrent infection, clinical or subclinical.
You can get infected with herpes simplex 1, even if you only have one sexual partner, the more sexual partners the higher the risk of infection with HSV-1.
Some individuals will not have any recurrences, while others may have over 15.
Herpes structure and types
types? envelope? size? seen under light microscope? what is inside the envelope? what is made of? structure? what is between this and the envelope?
describe the virus
There is a herpes simplex type 1 and type 2.
They are enveloped and around 120-300nm in size.
They cannot be seen under a light microscope.
There is a nucleocapsid inside the enveloped structure and the nucleocapsid is made of capsomeres.
The nucleocapsid has an icosahedral structure.
In between the nucleocapsid and the envelope there is the tegument.
The virus is a double stranded DNA virus, the DNA is linear and codes for more than 70 polypeptides.
Herpes diagnosis
lab based apporach
based on symtoms
lab based = take a swab and use the sample for pcr amplification of the viral dna
Herpes viral infection
where does it attach?
what fuses?
what enters cell and what is lost?
where does it go? what happens here? what is made?
what happens in the cytoplasm? what goes from here to the nucleus?
what happens to these and where do they go next?
Attachment to cell epithelial
Use of specific receptors. Which one uncertain.
Fusion of viral envelope with cell envelope.
Penetration
Lose envelope in the process
Nucleocapsid enters cell
Transport of the nucleocapsid through the cytoplasm to the nucleus
Viral DNA released in the nucleus
Viral DNA becomes circular
Replication of viral DNA in the nucleus
mRNA generated
The translation process takes place in the cytoplasm
Viral capsids assemble in the cytoplasm
Capsids transported to the nucleus
DNA packaged into empty capsid
Nucleocapsid containing DNA buds through the inner lamella of the nuclear membrane
Virus egress through the cell
Papillomavirus
structure?
enevlope?
genome?
what does it lead to? what is available for this?
Non enveloped - Icosahedral DNA genome -circular genome Family Papovaviridae Vaccination programme available Cervical cancer diagnosis = clincial and lab based
Papilloma virus infection is common in the population and not everyone infected will show symptoms
Papillomavirus - clinical course
how long can it incubate for?
how long is active growth and host containment?
what can the patient end up with?
The clinical course of the disease is as follows, it can incubate for a many months until the first lesion appears. ( 1 - 8 months)
There is then active growth and host containment of the disease, it then moves into late stage. (3 - 6 months)
Patient can end up with sustained clinical remission or persistent or recurrent disease.
