Batterjee Medical College: Nonspecific Defenses and Interferons

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What is the primary mechanism by which interferons inhibit virus replication?

By blocking the production of viral proteins
By inducing the synthesis of a ribonuclease that cleaves cell mRNA
By degrading viral mRNA (correct)
By entering the cell and interacting with viral proteins

Which type of interferon is involved in activating macrophages?

Delta interferon
Gamma interferon (correct)
Beta interferon
Alpha interferon

What is the characteristic of Natural Killer cells that allows them to recognize and destroy infected cells?

They recognize cells that do not display class I MHC proteins (correct)
They have an antigen receptor on their surface
They recognize cells that display class II MHC proteins
They recognize cells that display class I MHC proteins

Which type of RNA virus is the most potent inducer of interferons?

Double-stranded RNA virus (C) Signup and view all the answers

What is the mechanism by which Natural Killer cells kill infected cells?

By releasing granzymes (C) Signup and view all the answers

What is the primary function of viruses producing receptors for immune mediators such as IL-1 and TNF?

To prevent the activation of antiviral processes (D) Signup and view all the answers

What is the term for individuals who produce virus for long periods of time and can serve as a source of infection for others?

Carrier state (C) Signup and view all the answers

What type of host defense against viruses is comprised of interferons and natural killer cells?

Nonspecific immunity (A) Signup and view all the answers

Which type of infection is characterized by a long incubation period, often measured in years?

Slow virus infection (C) Signup and view all the answers

What is the main site of disease for slow virus infections such as progressive multifocal leukoencephalopathy?

Brain (D) Signup and view all the answers

What is a characteristic of viruses that distinguishes them from cells?

They are capable of independent replication (A) Signup and view all the answers

What is the structure composed of nucleic acid genome and capsid proteins?

Nucleocapsid (B) Signup and view all the answers

What is the symmetry of a viral nucleocapsid?

Spherical (icosahedral) symmetry or helical symmetry (B) Signup and view all the answers

What is the size range of viruses?

~20 nm to ~300 nm (B) Signup and view all the answers

What is the function of the capsid?

To cover the genome (A) Signup and view all the answers

Why can't the presence of IgG be used to diagnose a current infection?

Because IgG can be due to a past infection (A) Signup and view all the answers

What is the significance of a fourfold or greater increase in antibody titer in the convalescent serum sample?

It is used to diagnose a current infection (B) Signup and view all the answers

What is the 'gold standard' in viral diagnosis?

The presence of viral DNA or RNA (D) Signup and view all the answers

What is the purpose of labeled probes in viral diagnosis?

To identify specific viral nucleic acids (D) Signup and view all the answers

What is the purpose of reverse transcriptase in viral diagnosis?

To amplify small amounts of viral nucleic acids (A) Signup and view all the answers

What is the result of phenotypic mixing between two different viruses?

The progeny viruses can infect cells of species that the parental viruses could not. (C) Signup and view all the answers

What is the term for transmission of a virus from mother to offspring?

Vertical transmission (D) Signup and view all the answers

What is an example of a virus that uses the surface antigen of another virus as its outer coat protein?

Hepatitis D virus (A) Signup and view all the answers

What is the term for the process by which one virus produces a protein that can be used by another virus?

Complementation (A) Signup and view all the answers

What are the main portals of entry for viral infection?

Respiratory, gastrointestinal, and genital tracts (D) Signup and view all the answers

What is the process by which two different viruses infect the same cell and progeny viruses contain proteins of both parental viruses?

Phenotypic mixing (A) Signup and view all the answers

What is the term for the process by which segments of the genome RNA of influenza virus are exchanged?

Reassortment (C) Signup and view all the answers

What is the incubation period of a viral infection?

The period before symptoms appear (B) Signup and view all the answers

What are the four stages of viral infection in a person?

Incubation, prodromal, specific-illness, and recovery (B) Signup and view all the answers

What is the term for the transmission of a virus from one individual to another?

Horizontal transmission (D) Signup and view all the answers

What is the primary function of viral surface proteins?

To mediate attachment to host cell receptors (A) Signup and view all the answers

What is the purpose of matrix proteins in viral structure?

To link viral proteins and envelope proteins (A) Signup and view all the answers

What is a characteristic of enveloped viruses?

They are easily inactivated (D) Signup and view all the answers

What determines the host and organ specificity of a virus?

Viral surface proteins (B) Signup and view all the answers

What is a characteristic of naked viruses?

They survive longer in the environment (B) Signup and view all the answers

What is the result of adsorption of an enveloped virus to two cells at the same time?

Cell fusion (B) Signup and view all the answers

What is unique about the genome of parvoviruses?

It is single-stranded (C) Signup and view all the answers

Where do DNA viruses replicate, except for poxviruses?

Nucleus (D) Signup and view all the answers

What is the typical function of early proteins in viral replication?

Enzymes used in synthesis of viral components (A) Signup and view all the answers

How do poliovirus and retroviruses translate their mRNA?

Into precursor polyproteins (A) Signup and view all the answers