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Questions and Answers

What is a consequence of transcriptional errors in viruses?

Decreased virion production

Inhibition of viral protein assembly

Formation of viral inclusion bodies

Introduction of new mutants with clinical importance (correct)

Which process may contribute to the release of virus particles from infected cells?

Budding from the cell surface (correct)

Membrane fusion with neighboring cells

Cell wall rupture

Intracellular digestion

What type of test is primarily used to assess an acute viral infection?

Histopathological tests

Antibody detection tests

Antigen detection tests (correct)

Latent infection tests

What characterizes latent viral infections, such as those caused by herpes viruses?

Viral genome present without cell damage Signup and view all the answers

Which method is commonly used to detect viral antigens in samples?

Immunofluorescence Signup and view all the answers

What occurs during the lysis of an infected cell?

Release of intact infectious virions Signup and view all the answers

What is one of the roles of viral vaccines?

Prevention of viral infections Signup and view all the answers

What can happen to cells infected by certain viruses over time?

They may transform into tumor cells Signup and view all the answers

What is the primary definition of a virus?

A sub-microscopic obligate intracellular parasite Signup and view all the answers

What is the function of envelope glycoproteins on a virus?

To facilitate attachment to target cells Signup and view all the answers

What term describes the protein shell that surrounds the nucleic acid of a virus?

Capsid Signup and view all the answers

Which type of nucleic acid may a virus contain?

Single-stranded RNA or DNA Signup and view all the answers

What is required for viral penetration into a host cell?

Metabolic activity of the host cell Signup and view all the answers

Which statement correctly describes early and late viral proteins?

Early proteins are produced before DNA or RNA replication Signup and view all the answers

How do viruses replicate if they have RNA genomes?

They require their own polymerases to replicate Signup and view all the answers

Which mechanism is NOT involved in viral penetration into host cells?

Passive diffusion through the cell membrane Signup and view all the answers

What distinguishes antiviral drugs from antibiotics?

Antiviral drugs specifically target viral infections. Signup and view all the answers

Which of the following is NOT an example of an antiviral agent?

Amoxicillin Signup and view all the answers

Why do we need different influenza vaccines each year?

Influenza viruses mutate quickly. Signup and view all the answers

What is a common source of influenza infection?

Airborne droplets from coughs and sneezes Signup and view all the answers

Which of the following statements about viruses is true?

Viruses can contain either DNA or RNA as their genetic material. Signup and view all the answers

Which type of vaccine is considered genetically engineered?

Recombinant vaccines Signup and view all the answers

What is one major difference between viruses and bacteria?

Viruses cannot survive without a host cell. Signup and view all the answers

Which of the following best describes a live attenuated virus vaccine?

It contains weakened live virus that cannot cause disease. Signup and view all the answers

Which of the following drugs is NOT used for the treatment of viral infections?

Ciprofloxacin Signup and view all the answers

What do we refer to when discussing infection prevention measures?

Public health guidelines and hygiene practices Signup and view all the answers

What may occur if a virus causes a latent infection?

Reactivate due to immune changes leading to virus production Signup and view all the answers

What is a significant reason for performing PCR or antigen detection tests?

To assess acute infections Signup and view all the answers

How do some viruses exit the host cell without killing it?

Through budding from the cell surface Signup and view all the answers

In which testing method would you find serum samples analyzed for specific antiviral antibodies?

Rapid tests Signup and view all the answers

What may potentially lead to the formation of inclusion bodies in viral infections?

The accumulation of virions during assembly Signup and view all the answers

Which of the following methods is NOT used for antigen detection during viral diagnosis?

Western blotting Signup and view all the answers

What distinguishes the common outcome of viral infections characterized by host cell damage versus those that lead to cell death?

Progeny viruses are produced in cases of cell damage Signup and view all the answers

Which factor might contribute to the lack of virus progeny despite viral infection?

Unique resistance of the infected cell Signup and view all the answers

What is the function of capsomers in a virus?

They form the protein shell that encloses the nucleic acid. Signup and view all the answers

Which of the following statements about viral genomes is incorrect?

Viral genomes are always linear in structure. Signup and view all the answers

What defines host species and cell tropism for viruses?

The specificity of the reaction between viral proteins and host receptors. Signup and view all the answers

What is a key requirement for the active process of viral penetration?

The target host cell's metabolic activity. Signup and view all the answers

Which statement best describes the characteristics of 'Early' viral proteins?

They are commonly involved in the replication of viral nucleic acids. Signup and view all the answers

What does the nucleocapsid of a virus consist of?

The combination of the capsid and its enclosed nucleic acid. Signup and view all the answers

What is the primary function of viral glycoproteins?

To facilitate attachment to specific host cell receptors. Signup and view all the answers

Which type of polymerases do viruses with RNA genomes need?

Viral polymerases which they must synthesize or bring. Signup and view all the answers

Which of the following antiviral agents is specifically indicated for the treatment of influenza?

Tamiflu Signup and view all the answers

What is the fundamental characteristic that differentiates viruses from bacteria?

Viruses contain either DNA or RNA but not both. Signup and view all the answers

Which type of vaccine is least likely to elicit a cellular immune response?

Inactivated Vaccines Signup and view all the answers

Why is it necessary to develop a new influenza vaccine each year?

Influenza virus mutations result in changed antigenic properties. Signup and view all the answers

Which of the following conditions is primarily caused by a virus?

Influenza Signup and view all the answers

Antiviral drugs are designed to target which of the following?

Viral replication mechanisms Signup and view all the answers

In the case of Grandfather Ali, which misconception did he address regarding flu treatment?

The flu is caused by a virus, not a bacterium. Signup and view all the answers

What type of viral genome can be found in viruses?

Either DNA or RNA Signup and view all the answers

Which of the following is likely to be a common source of influenza infection?

Respiratory droplets from infected individuals Signup and view all the answers

What is a crucial reason for differentiating between antiviral drugs?

Each antiviral drug has specific indications based on the virus type. Signup and view all the answers

Study Notes

General Virology

Viruses are defined as submicroscopic, obligate intracellular parasites that only replicate inside living host cells.
Virions (virus particles) do not grow or undergo division.
Viral structure includes a protein shell (capsid), containing the nucleic acid (RNA or DNA). Some viruses have an outer envelope made of lipids derived from host cells.
Viral shapes include helical, icosahedral, and complex.
Virus size varies significantly, from 15 to 300 nanometers.
Viral replication involves six key steps: adsorption, penetration, uncoating, replication, assembly, and release.
Viral infections can cause various effects on host cells, including lysis (host cell death), or converting them into a permanent infected state.
Viral infections are diagnosed by detecting viral genetic material (DNA or RNA) using PCR, identifying viral antigens, or by detecting antibodies against the virus.

Viral Replication

Viral replication occurs in six main stages:
Adsorption: Viruses attach to specific receptors on host cells.
Penetration: The virus enters the host cell. This involves translocation (movement across the cell membrane), endocytosis (entry in vesicles), or fusion (viral envelope merging with the cell membrane).
Uncoating: The viral genome is released from the capsid.
Replication: The viral genome is replicated, and viral proteins are synthesized either using viral or cellular polymerases.
Assembly: New viral particles are assembled. Sites of assembly may form inclusion bodies.
Release: The new viral particles are released from the host cell either by exocytosis (budding), or cell lysis.

Viral Classification

Viruses are classified based on their nucleic acid type (DNA or RNA), strandedness (single or double), linearity (linear or circular), and segmentations. This classification is crucial for understanding viral behavior and developing targeted treatments.

Viral Structure

Viruses consist of a genetic material (RNA or DNA) enclosed in a protein coat (capsid).
Some viruses have an additional outer envelope derived from the host cell membrane, which can be crucial for infecting new cells.
The capsid is composed of protein subunits called capsomeres.
The nucleic acid determines the virus' genetic properties.

Viral Replication Mechanisms

Translocation: The entire virion moves across the cell membrane.
Endocytosis: The virus enters the host cell membrane within vesicles.
Fusion: The viral envelope fuses with the cell membrane.

Effects of Viral Infections on Cells

Some viral infections result in host cell death and new virus production (lytic infections).
Some infections lead to a persistent state where host cells remain infected but are not necessarily killed, or they can cause chronic infections or tumors.
Certain viruses can exist in a latent state, where the viral genome remains inactive until a trigger activates replication.

Genomic Transcription & Translation

Mammalian genes only synthesize DNA & RNA in the nucleus; thus, viruses replicating in the cytoplasm must make their own polymerases to replicate and transcribe viral genes. This is a critical aspect of viral pathogenesis.
Messenger RNA is translated into viral proteins by host ribosomes, or the viral proteins might bring their own polymerases. The "early" proteins are often involved in replication and transcription, while "late" proteins are structural components of the new virions. This distinct timing of protein production is important.

Assembly

Viral proteins assemble into new viral particles inside the host cell.
Assembly sites may lead to the formation of inclusion bodies, which aid in diagnosing viral infections. These are visible aggregates of viral proteins inside infected cells.

Release

Viruses are released via exocytosis through host cell membrane, or cell lysis. Different release mechanisms have differing effects.

Prevention and Treatment

Vaccination is a key method for preventing viral infections, inducing immunity to specific viral types.
Antiviral drugs are available but they are highly specific to particular viruses and have limited uses.

Laboratory Diagnosis

Viral infections are diagnosed using different methods:
- Detecting viral genome using PCR, offering high precision.
- Detecting viral antigens.
- Antibody detection to determine prior infection (used for chronic conditions or past exposure).

Clinical Case

Grandfather Ali exhibited symptoms suggestive of a viral infection (cold). The incorrect advice to use antibiotics is a crucial point about differentiating viral and bacterial infections. The need for accurate diagnosis before prescribing treatment is paramount.

Summary

Viruses are microscopic agents that cause human infections.
Viral genomes comprise DNA or RNA.
Viral replication requires host cell machinery, frequently with the viral genome being a template for other viral genes.
The replication cycle can lead to host cell death (lysis).
Diagnosis often involves detecting viral nucleic acids (PCR), antigens, or antibodies.
Prevention frequently utilizes vaccines.
Antiviral medicine exists but tends to be targeted to specific types of viruses.

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