viruses and retroviruses

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Questions and Answers

What is the primary function of the glycoprotein gp120 in the life cycle of HIV?

binds to surface molecules CD4 of T helper cells, macrophages etc.

What is the purpose of the integrase enzyme in the replication cycle of HIV?

inserts the viral DNA into host cells chromosome

What is the term for the latent period of HIV infection, during which the virus is not actively replicating?

clinical latency period

What is the threshold below which the T cell count drops, indicating the progression of HIV to AIDS?

after 6-7 years, T cell count drops the threshold Signup and view all the answers

What is the term for the process by which HIV releases its genetic material into the host cell?

Viral envelope fuses with cell membrane (gp41) releasing contents into the cell Signup and view all the answers

What is the enzyme responsible for converting HIV RNA into DNA, allowing the virus to replicate?

reverse transcriptase Signup and view all the answers

What is the final stage of HIV infection, characterized by a severely weakened immune system?

AIDS Signup and view all the answers

What is the primary cause of gastrointestinal symptoms in individuals with HIV/AIDS?

Infection of the GI tract Signup and view all the answers

What type of cancer is a common respiratory symptom in individuals with HIV/AIDS?

Lung cancer Signup and view all the answers

What is the primary mechanism of action of nucleotide or nucleoside RT inhibitors in treating HIV infection?

Inhibiting reverse transcriptase Signup and view all the answers

What is the role of integrase inhibitors in treating HIV infection?

Inhibiting HIV integration into host DNA Signup and view all the answers

Why is it necessary to take anti-retroviral therapy for life in individuals with HIV infection?

There is no cure for HIV, and treatment must be continued to suppress the virus Signup and view all the answers

What is the significance of HIV accessory genes in the viral life cycle?

They perform various functions necessary for HIV replication Signup and view all the answers

what is nef?

accessory gene that encodes for nef protein which plays an important role in HIV pathogenesis. Signup and view all the answers

What is the primary function of the enzyme reverse transcriptase in the retrovirus replication cycle?

To convert ssRNA into dsDNA Signup and view all the answers

What is the purpose of the integrase enzyme in the retrovirus replication cycle?

To integrate the viral genome into the host chromosome Signup and view all the answers

What type of genome does a retrovirus have, and what are its characteristic features?

Diploid, ssRNA, capped and polyadenylated Signup and view all the answers

What are the three main genes encoded by the retrovirus genome, and what do they encode for?

Gag, Pol, and Env; encoding for structural proteins, enzymes, and surface glycoproteins respectively Signup and view all the answers

What is the fate of the retrovirus genome after it integrates into the host chromosome?

It can either progress onwards or remain latent as a provirus Signup and view all the answers

What is the structure of a retrovirus, and what are its outer and inner components?

Spherical shape with an outer enveloped phospholipid membrane, transmembrane and surface proteins, and an inner matrix, capsid, and nucleocapsid Signup and view all the answers

What is the primary function of the capsid in a virus?

Protecting the nucleic acid Signup and view all the answers

What is the difference between enveloped and unenveloped viruses?

Enveloped viruses have a phospholipid membrane, while unenveloped viruses do not. Signup and view all the answers

What determines the shape of a virus?

The arrangement of the capsid proteins Signup and view all the answers

What is the role of attachment sites in the life cycle of a virus?

Binding of the virus to the host cell cytoplasmic membrane Signup and view all the answers

What is the purpose of viral mRNA?

Translation into viral proteins Signup and view all the answers

What is the Baltimore classification based on?

How viruses make their mRNA Signup and view all the answers

What is the result of penetration in the life cycle of a virus?

Entry of the nucleic acid into the host cell Signup and view all the answers

What is the function of enzymes in viral replication?

To facilitate mRNA synthesis and translation Signup and view all the answers

What is the characteristic feature of viral genomes?

They can be RNA or DNA, but not both Signup and view all the answers

Study Notes

HIV Structure and Replication

HIV is a lentivirus that causes AIDS, transmitted through sexual contact and bodily fluids.
HIV does not survive outside the body and cannot reproduce outside of the host cell.
HIV's life cycle involves:
Binding of gp120 to CD4 surface molecules on T helper cells and macrophages
Fusion of viral envelope with cell membrane, releasing contents into the cell
Conversion of RNA to DNA by reverse transcriptase
Integration of viral DNA into host cell chromosome
Transcription and translation of viral genome to produce viral proteins
Assembly and release of new viruses through budding

Phases of HIV Infection

Acute phase: sharp peak in 10-12 weeks, symptoms include fever, and a rapid drop in T cells
Clinical latency period: no symptoms, slow decrease in T cells, and increase in HIV
AIDS stage: severe weakening of immune system, increase in HIV copies, and appearance of opportunistic infections

Symptoms of AIDS

Gastrointestinal Symptoms

Abdominal pain
Diarrhea
Weight loss
Infection of GI tract

Respiratory Symptoms

TB
Lung cancer

Neurological Symptoms

Headaches
Memory loss
Skin disorders
Herpes
Thrush
Eye infections

Treatment of HIV

No cure for HIV, but anti-retroviral therapy (ART) can manage the infection
Combination of nucleotide or nucleoside RT inhibitors, integrase inhibitors, and other drugs

Retrovirus Structure and Replication

Enveloped, spherical shape, 80-120nm in diameter
Composed of phospholipid membrane, matrix, capsid, and enzymes (proteases, integrase, and reverse transcriptase)
Genome: diploid, ssRNA, capped and polyadenylated
Encodes at least 3 genes: gag, pol, and env
Replication cycle: attachment, penetration, synthesis, assembly, and release

Viruses

Structure of a Virus

Can be enveloped or unenveloped (naked)
Composed of nucleic acid (DNA or RNA) and capsid
Shapes: icosahedral, helical, or complex
Highly symmetric
Can contain RNA or DNA, but not both
Can be double-stranded or single-stranded, linear or circular

Life Cycle of a Virus

Attachment (adsorption) of virus to host cell receptor
Penetration of virus into host cell through endocytosis or fusion with plasma membrane
Uncoating of virus
Synthesis of viral mRNA and protein
Assembly and release of new viruses

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Description

Learn about the structure and function of retroviruses, including their spherical shape, envelope, and genome. Discover how they replicate and the diseases they can cause, such as AIDS and cancer.