HIV/AIDS

Question 1

HIV-1 vs HIV-2

Answer 1

HIV-1 and HIV-2 share much - basic gene arrangement, modes of transmission, intracellular replication pathways and clinical consequences: both result in AIDS. However, HIV-2 is characterised by lower transmissibility and reduced likelihood of progression to AIDS. Plasma viral loads are consistently lower in HIV-2, as are average levels of immune activation however more IL-2; is produced and humoral responses include neutralisation. Overall, the immune response to HIV-2 appears more protective against disease progression

Question 2

Describe the HIV virus

Answer 2

HIV is a positive stranded RNA virus but unusually has two identical RNA strands that are dimerized. This dimeric structure is thought to be essential for effective RNA replication and stabilisation.

Question 3

What are the transmission route of HIV?

Answer 3

• Unprotected sexual intercourse with infected partner
• Vertical transmission (from mother to child in utero, during delivery or through breast milk)
• Injection drug use

Question 4

What are the stages of infection of HIV?

Answer 4

• CD4 binding is a necessary first step but entry into the cell requires a coreceptor that binds to CD4. The two coreceptors are CCR5 and CXCR4.
• CD4 is expressed on the surface of Th cells, T reg cells, monocytes, macrophages, and dendritic cells. CCR5 is predominantly expressed on T cells (memory and activated), gut associated lymphoid tissues (GALT), macrophages, dendritic cells, and microglia. CXCR4 is expressed on T cells (naïve and resting CD4 lymphocytes, as well as CD8 cells), B cells, neutrophils, and eosinophils.

Question 5

What are the phases of HIV infection?

Answer 5

Question 6

What are the co-infections with HIV?

Answer 6

Question 7

What are the reservoirs for HIV?

Answer 7

• Tissue resident T follicular helper (TFH) cells and follicular dendritic cells (FDC) are long- lived viral reservoirs that reside within B cell follicles (BCF) found in secondary LTs.
• In these sites low levels of cell activation and residual levels of immune activation and inflammatory mediators are heightened during ART
• Antiretroviral (ARV) drug penetration into tissue sites of viral persistence is very heterogeneous - this can generate an environment that allows for allows for low level, intermittent viral replication can occur

Question 8

What is antiretroviral chemotherapy (ART)?

Answer 8

Question 9

Give 4 examples of ART and what their target is

Answer 9

Question 10

What are the HIV testing options?

Answer 10