HIV Flashcards
HIV consists of 2 strands of what molecule?
- single stranded RNA in an envelope
what are main 2 types of surface antigens on HIV molecule?
- GP120
- GP41
-> important in allowing virus to bind to host cell
host cell of interest in HIV is?
- T helper cell or CD4 cell
what receptors are on CD4 cell?
- CD4 receptor
- CCR5 co-receptor
binding of CD4 cell and HIV receptors allows for what?
- enables the viral envelope to fuse with the cell surface membrane (fusion)
- allowing single stranded RNA to enter the cell
after single stranded DNA is in the cell what is the next process to occur?
- reverse transcriptase
- RNA is converted to DNA
-> now have a DNA copy of viruses RNA
-> this can then be incorporated into the host’s own genome
what is the term used to describe when virus RNA is incorporated into a host’s genome
- integration
what can occur once RNA is part of host’s genome?
- transcription
- translation
thus creating viral proteins which can be packaged together to form another virus through a process called budding (when RNA comes off membrane of the host cell)
final part of the process creates what cell?
- mature virion
- another virus
what is HIV?
- single stranded RNA retrovirus that infects and replicates within the human immune system using host CD4 cells
what kind of virus is HIV?
- RNA retrovirus
- MSM is the risk group for the majority of prevalent infections and new infections in the UK
how is HIV transmitted?
- sexual transmission accounts for 79% of the new infections in the UK
what are some factors increasing transmission risk?
- anoreceptive
- trauma
- genital ulceration
- concurrent STI
what is parental transmission?
- process of acquiring an infectious agent into ones body through something other than GI (enteral route)
- ie injection drug use, infected blood products, iatrogenic
mother-to-child infection can be transmitted through which ways?
- in utero/trans-placental
- delivery
- breastfeeding
what is the pathophysiology behind HIV infection?
- firstly infection of mucosal CD4+ cell
- transport to regional lymph nodes
- infection established within 3 days of entry
- dissemination of virus
what is CD4?
- glycoprotein found on the surface of a range of cells, including T helper lymphocytes (CD4+ cells), dendritic cells, macrophages, and microglial cells
- they are essential for induction of adaptive immune response
what do CD4+ Th lymphocytes do?
- recognise MHC2 antigen-presenting cell
- activation of B-cells
- activation of cytotoxic T cells (CD8+ cells)
- cytokine release
what effects do HIV infections have on the immune response?
- reduced circulating CD4+ cells
- reduced proliferation of CD4+ cells
- reduction in CD8+ T cell activation -> dysregulated expression of cytokines
- reduction in antibody class switching -> reduced affinity of antibodies produced
- chronic immune activation
this will increase susceptibility to viral infections, fungal infections, mycobacterial infections and infection-induced cancers
how does primary HIV infection present?
- up to 80% present w sympoms
- onset 2-4 weeks after initial infection
- fever
- rash (maculopapular)
- myalgia
- pharyngitis
- headache/asceptic meningitis
- v high risk of transmission at this stage
what is an opportunistic infection?
- infection by an individual that does not normally produce disease in a healthy individual
- but will in those with weakened immune systems i.e. in people living w HIV
those with HIV can go on to develop?
- AIDS
what kind of opportunistic infections are those living with HIV at risk of?
bacterial infection
- mycobacterium tuberculosis
- recurrent pneumonia
viral infection
- CMV
- herpes simplex
- bronchitis/pneumonitis
- progressive multifocal leukoencephalopathy (PML)
parasitic infection
- cerebral toxoplasmosis
fungal infection
- pneumocystis jiroveci pneumonia (PCP)
- candidiasis - oesophageal, bronchial/tracheal/pulmonary
what are some symptoms and signs of PCP?
- insidious onset SOB and dry cough
- will see exercise oxygen desaturation
- CXR may be normal, interstitial infiltrates, reticulonodular markings
- Dx: BAL and immunofluorescence +/- PCR
- Mx: high dose co-trimoxazole
what is the prophylaxis for patients with PCP and a CD4+ <200
- low dose co-trimoxazole - also offers some protection against cerebral toxoplasmosis
what kind of TB can patients w HIV get?
- more likely to have symptomatic primary infection, reactivation of latent TB, miliary TB, extrapulmonary TB
what is cerebral toxoplasmosis?
- infection of the brain or spinal cord caused by a single-celled parasite called toxoplasma gondii
- reactivation of latent infection - multiple cerebral abscess, chorioretinitis
- CD4+ <150
how does cerebral toxoplasmosis present?
- headache, fever, focal neurology, seizures, reduced consciousness, raised ICP
what can be CD4 count be in those w HIV and CMV?
- <50
- people with CD4+ <50 should have ophthalmic screening
reactivation of CMV can cause what kind of complications?
- retinitis
- colitis
- oesophagitis
how does CMV present?
- reduced visual acuity, floaters, abdominal pain, diarrhoea, PR bleeding
what is progressive multifocal leukoencephalopathy?
- JC virus (reactivation)
- CD4 <100
- presents w rapidly progressing, focal neurology, confusion, personality change
what are some skin infections that can affect those w HIV?
- herpes zoster - multidermatomal, recurrent
- herpes simplex - extensive, hypertrophic, aciclovir resistant
- HPV - extensive, recalcitrant, dysplastic
what is ‘slims disease’?
- HIV associated wasting
- it has multiple causes -> metabolic, anorexia, malabsorption/diarrhoea, hypogonadism
Name 3 types of cancers related to AIDS
- Kaposi’s sarcoma
- non-hodgkin’s lymphoma
- cervical cancer
what is Kaposi’s sarcoma?
- vascular tumour caused by HHV8
- presents: cutaneous, mucosal, visceral (pulmonary, GI)
mx for kaposis sarcoma?
- anti-retrovirals, local therapies, systemic chemo
