HIV Flashcards
What does HIV cause?
- Human immunodeficiency virus (HIV) 1 is the cause of acquired immunodeficiency syndrome (AIDS)
- Both HIV-1 and HIV-2 cause AIDS, but HIV-1 is found worldwide, whereas HIV-2 is found primarily in West Africa.
Important properties of HIV
- one of two important human T-cell lymphotropic retroviruses
- infects/kills helper (CD4) T lymphocytes, resulting in the loss of cell-mediated immunity and high probability that host will develop opportunistic infections. Other cells (e.g., macrophages and monocytes) that have CD4 proteins on their surfaces can be infected also
- belongs to lentivirus subgroup of retroviruses, which cause “slow” infections with long incubation periods
- bar-shaped (type D) core surrounded by envelope containing virus-specific glycoproteins (gp120 and gp41) * genome of consists of two identical molecules of single-stranded, positive-polarity RNA and diploid
Describe the genome of HIV
most complex of the known retroviruses
In addition to the typical retroviral genes gag, pol, and env, which encode the structural proteins, the genome RNA has six regulatory genes: Two of these, tat and rev, are required for replication, and the other four, nef, vif, vpr, and vpu, not required and termed “accessory” genes
What does the gag gene of HIV do?
1) Gag gene: encodes internal “core” proteins (p24) .
2) pol gene: encodes several proteins, including the virion “reverse transcriptase;’ which synthesizes DNA by using the genome RNA as a template, an integrase that integrates the viral DNA into the cellular DNA, and a protease that cleaves the various viral precursor proteins.
3) env gene encodes gp160 (precursor glycoprotein that is cleaved to form the two envelope (surface) glycoproteins, gp120 and gp4l)
What does the gag, pol, and env genes of HIV do?
1) Gag gene: encodes internal “core” proteins (p24) .
2) pol gene: encodes several proteins, including the virion “reverse transcriptase;’ which synthesizes DNA by using the genome RNA as a template, an integrase that integrates the viral DNA into the cellular DNA, and a protease that cleaves the various viral precursor proteins.
3) env gene encodes gp160 (precursor glycoprotein that is cleaved to form the two envelope (surface) glycoproteins, gp120 and gp4l)
On the basis of differences in the base sequence of the gene that encodes gpl20, HIV has been subdivided into subtypes (clades) A through I. The B clade is the most common subtype in North America. Subtype B preferentially infects?
mononuclear cells and appears to be passed readily during anal sex, whereas subtype E preferentially infects female genital tract cells and appears to be passed readily during vaginal sex.
In HIV three enzymes are located within the nucleocapsid of the virion
reverse transcriptase, integrase, and protease
What does reverse transcriptase do for HIV?
It’s the RNA-dependent DNA polymerase that is the source of the family name retroviruses. It transcribes RNA genome into proviral DNA. A bifunctional enzyme; it also has ribonuclease H activity. Ribonuclease H degrades RNA when it is in the form of an RNA-DNA hybrid molecule. Thedegradation of the viral RNA genome is an essential step in the synthesis of the double-stranded proviral DNA. Integrase, another important enzyme within the virion, mediates the integration of the proviral DNA into the host cell DNA. The viral protease cleaves the precursor polyproteins into functional viral polypeptides.
One essential regulatory gene is the tat (transactivation of transcription) gene, which encodes a?
protein that enhances viral (and perhaps cellular) gene transcription. The Tat protein and another HIV-encoded regulatory protein called Nef repress the synthesis of class I MHC proteins,
Transport of late mRNAs from nucleus to cytoplasm
Rev
Activation of transcription of viral genes
Tat
