6.5 The body’s response to HIV and AIDS Flashcards
why is the number of infections for HIV lower than predicted?
improved methodology for making estimates, better HIV surveillance by countries and changes in key epidemiological assumptions used to calculate the estimates
why has there been an improvement in the HIV research?
more investment in HIV prevention programs and great to access to drugs. advances in preventing new HIV infections and HIV related death
what is a syndrome?
A collection of symptoms related to the same cause which gradually destroys part of immune system
How is the lipid envelope surrounding a HIV particle formed?
from the host cell membrane as the new virus particles emerge from the cell cytoplasm
what are the glycoprotein molecules on the surface of HIV particles called?
gp 120
how do HIV particles invade T helper cells and macrophages?
gp 120 bind to the CD4 receptors on the surface of the T helper cells. the envelope around the virus fuses with the cell membrane enabling the viral RNA to enter the cell
once inside the host cell, what must the virus do?
It needs to make the host cell replicate new virus components
What is used to produce DNA from RNA?
The enzyme reverse transcriptase
viruses that contain RNA and use reverse transcriptase are known as…
retroviruses
How is the HIV DNA integrated into the host DNA?
using the HIV enzyme integrase
what will the host cell assemble for the new virus particles?
glycoproteins, nuclear material and new HIV virus proteins
What happens to the host cell after the viral particles leave?
it dies
Explain why a person affected with HIV has a deficient immune system
infected T helper cells will also be destroyed by T killer cells. This loss results in macrophages, B cells and T killer cells not being activated and therefore not functioning.
Explain why the rate of viral replication is greatly reduced after a few weeks
infected T helper cells are recognised by T killer cells which start to destroy them
what happens during the acute phase?
HIV antibodies appear in the blood after 3 to 12 weeks, symptoms may occur, the virus replicates rapidly and T killer cells destroy T helper cells
what are the three phases of HIV?
The acute phase, the chronic phase and the disease phase
what can happen during the chronic phase?
may be no symptoms, increased tendency of colds and dormant diseases like TB and shingles can reactivate
what happens during the disease phase?
increased viruses and less T helper cells indicates the onset of AIDS. The immune system is very weak so opportunistic infections take place.
What is mRNA splicing?
when introns are removed between transcription and translation
how has the discovery of mRNA splicing change the ‘one gene one protein’ theory?
we now know that one gene can code for several related proteins
