Virology Quiz: Virus Assembly and Cultivation

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Questions and Answers

During which stage are new virus particles assembled from nucleic acid and proteins?

Replication stage

Synthesis stage (correct)

Release stage

Isolation stage

How are newly matured viruses typically released from host cells?

Only by programmed cell death

Through exocytosis only

By sudden rupture or gradual extrusion (correct)

Via passive diffusion through the cell wall

What is the primary requirement for virus replication?

High-sugar environments

Artificial nutrient media

Anaerobic conditions

Living host cells (correct)

Which method can be used to separate virions from host cells in a culture?

Centrifugation or filtration Signup and view all the answers

Where can viruses be cultivated in vivo?

Within a whole living organism, such as an animal Signup and view all the answers

Which of the following is NOT a reason for cultivating animal viruses?

Conducting chemical reactions Signup and view all the answers

What is meant by tissue tropism in the context of viral infections?

The preference of a virus for specific types of cells or tissues for growth Signup and view all the answers

Which site is NOT typically a target for viral introduction in an embryo?

Brain cavity Signup and view all the answers

What are the types of symmetry that can be found in viral nucleocapsids?

Icosahedral, helical, and complex Signup and view all the answers

How do enveloped viruses obtain their envelope?

By budding through a host cell membrane Signup and view all the answers

Which of the following describes a characteristic of dsRNA viruses?

They exemplify examples like Reoviruses Signup and view all the answers

Which classification method is used to categorize viruses?

Considering nucleic acid type, morphology, envelope presence, and size Signup and view all the answers

In which type of cells do most DNA viruses assemble?

Nucleus Signup and view all the answers

What defines a ssRNA-RT virus in the context of viral classification?

It possesses a DNA intermediate in its life cycle Signup and view all the answers

What is the significance of the capsid in viruses?

It serves as a protective protein coat for the genome Signup and view all the answers

What is a common requirement for viral replication to occur?

Entry into a living host cell Signup and view all the answers

What structural proteins are key antigens for determining antigenic variation in influenza viruses?

Hemagglutinin and Neuraminidase Signup and view all the answers

Which population is especially at risk when infected with the influenza virus?

Elderly and very young individuals Signup and view all the answers

Which specimen type is considered best for viral isolation of influenza virus?

Nasal washings Signup and view all the answers

What does the hemagglutination inhibition (HI) assay primarily test for in the context of influenza infection?

Antibodies against viral glycoproteins Signup and view all the answers

Which statement is true regarding the Paramyxoviridae family?

Respiratory tract is the primary route of infection. Signup and view all the answers

What is the genome type of the Paramyxoviridae?

Negative-sense single-stranded RNA Signup and view all the answers

How many subtypes of Hemagglutinin are recognized in influenza viruses?

15 subtypes Signup and view all the answers

What is the primary laboratory method used for the isolation of influenza viruses?

Viral culture in embryonated eggs Signup and view all the answers

What is a primary disadvantage of attenuated live-virus vaccines?

They have a risk of reversion to greater virulence. Signup and view all the answers

Which of the following statements about viral pathogenesis is true?

Destruction of virus-infected cells contributes to clinical illness. Signup and view all the answers

What is viremia?

The presence of virus in the bodily fluids. Signup and view all the answers

How do attenuated vaccines stimulate an immune response?

By replicating in the host and mimicking natural infection. Signup and view all the answers

What problem may arise due to coinfection with wild type viruses?

It may inhibit the replication of the vaccine virus. Signup and view all the answers

Which site is most commonly associated with the primary replication of viruses?

Gastrointestinal tract Signup and view all the answers

What is the main mechanism through which viruses spread within a host after primary replication?

Via the bloodstream or lymphatics. Signup and view all the answers

What is the primary factor influencing the degree of illness caused by viral infections?

The interaction between the virus and the host. Signup and view all the answers

What is the role of the fusion (F) glycoprotein in paramyxoviruses?

It participates in viral envelope formation. Signup and view all the answers

Which method is preferred for detecting IgM antibodies in rubella diagnosis?

Enzyme-linked immunosorbent assay (ELISA) Signup and view all the answers

What is a key feature of rubella when infection occurs during pregnancy?

It can lead to congenital abnormalities. Signup and view all the answers

Which bodily fluid is most sensitive for isolation of parainfluenza viruses?

Nasal washes Signup and view all the answers

Which option is not commonly associated with the identification of rubella virus?

Blood culture Signup and view all the answers

What characteristic makes enteroviruses different from rhinoviruses?

Enteroviruses are isolation from the lower intestinal tract. Signup and view all the answers

Which structural protein of paramyxoviruses is known for possible neuraminidase activity?

Hemagglutinin (HN) glycoprotein Signup and view all the answers

What is a limitation of antigen detection methods for viral diagnosis?

They are less sensitive than viral isolation methods. Signup and view all the answers

What is a significant limitation of serological assays for diagnosing viral infections?

They may be affected by the presence of multiple antigens. Signup and view all the answers

Which method has replaced the isolation of viral DNA from brain tissue in diagnosing certain viral infections?

PCR amplification of viral DNA. Signup and view all the answers

What is the primary risk posed by Cytomegalovirus (CMV) infections in infants?

Congenital infections leading to severe congenital anomalies. Signup and view all the answers

What is the most common specimen type used for PCR assays when diagnosing CMV infections?

Blood and urine samples. Signup and view all the answers

How long does it typically take for cytological changes to appear when culturing the CMV virus?

2-3 weeks. Signup and view all the answers

What type of viruses are known to be etiologic factors in the development of human tumors?

Oncoviruses. Signup and view all the answers

What does the detection of IgG antibodies indicate in serological testing?

Past infection. Signup and view all the answers

Which virus is strongly associated with cervical cancer among other tumors?

Human papilloma virus. Signup and view all the answers

Study Notes

Virology - Lecture 1

Nucleic acids (DNA and RNA) are hereditary material in nearly all organisms.
DNA is located mostly in the cell nucleus.
DNA has four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T).
Human DNA has about 3 billion bases, with over 99% being the same in all people.
The order of these bases determines the organism's information.
DNA bases pair up: A with T, and C with G.
A nucleotide is a base, sugar, and phosphate molecule.
Nucleotides form two long strands that create a DNA double helix.
RNA is an important molecule, also made of nucleotides.
Each RNA nucleotide has a nitrogenous base, ribose sugar, and a phosphate, like DNA.
RNA is typically single-stranded, in contrast to DNA's double helix.
RNA contains ribose, while DNA has deoxyribose.
RNA has the bases: Adenine (A), Uracil (U) (instead of thymine in DNA), Cytosine (C), and Guanine (G).

Virology - Viruses

Viruses are the smallest unicellular infectious agents (20 nm to 300 nm in diameter).
Viruses contain only one type of nucleic acid (RNA or DNA).
The nucleic acid is encased in a protein shell (capsid).
The capsid may be surrounded by a lipid membrane.
Viruses are obligate intracellular molecular parasites.
Viral genome is composed of DNA or RNA.
Viruses synthesize virion components in a host cell.
Progeny virus particles spread infection to new cells.

Virus Structure

Viruses have various symmetries
Icosahedral symmetry is a Platonic solid with twenty faces.
Helical symmetry of the capsid forms a spiral-like structure.
Complex symmetry structures have an undefined symmetry.

Virus Classification

Virus classification considers nucleic acid type, capsid symmetry, presence of an envelope, and size.
Seven groups exist: double-stranded DNA, single-stranded DNA, double-stranded RNA, single-stranded positive sense RNA, single-stranded negative sense RNA, single-stranded RNA with DNA intermediate, and double-stranded DNA with RNA intermediate.

Virus Replication

Viral replication occurs in seven stages: attachment, entry, uncoating, transcription/mRNA production, synthesis of virus components, virion assembly, and release.
Viruses attach to the host's cell membrane.
Viral nucleic acid enters a host cell by endocytosis (animal cells) or pinocytosis (plant cells).
Viral enzymes remove the capsid.
Host cell machinery produces mRNA from viral nucleic acid.
Viral components are assembled into new viruses.
Newly formed viruses are released from the infected host cell, sometimes causing the cell to rupture.

Viral Infection of a Cell

Viruses infect host cells (eukaryotic or prokaryotic), and are separated from host cells using centrifugation or filtration.

Cultivation of Viruses

Viruses can be grown in vivo (in a living organism - e.g., embryonated eggs) or in vitro (in test tubes or cell cultures).
Viruses need a host cell for replication.
Filters are used to separate virions from larger particles

Anti-viral Chemotherapy

Antiviral drugs target viral replication but do not harm host cells.
Viral replication varies, and drugs must be selective.
Difficult to develop effective antiviral drugs due to the dependence of viral replication on host machinery.

Viral Vaccines

Viral vaccines stimulate an immune response.
Killed-virus vaccines use inactivated viruses.
Attenuated-live virus vaccines use weakened viruses.
Extreme care is required to prevent the residual live virus in a killed-virus vaccine.
Live viral vaccines may cause a less severe illness, but some must be boosted to maintain the immune response, whereas killed virus vaccines are generally easier to create and store but their effect often needs boosting to maintain response.

Pathogenesis of Viral Diseases

Viruses enter, replicate, spread, and cause damage in susceptible cells.
Viral spread can be via the bloodstream or lymphatic system.
Viral infections may cause various effects in the body resulting in clinical illness including damage or destruction to host tissues.

Viral Shedding

Viral shedding is the release of viruses from the host.
The shedding occurs differently based on the agent and stage of disease (e.g., some shed in dead-end infections or different steps).

Cell Injury and Clinical Illness

Virus-infected cells in the target tissue lead to the development of diseases.
The degree of illness varies.

Genetic of Viruses

DNA viruses infect animals with predominantly double-stranded DNA genomes.
Exceptions exist in viral genomes including some RNA viruses.
RNA viruses can have single-stranded RNA genomes, however some have double-stranded genomes.
Retroviruses are a notable group of RNA viruses. The order mononegavirales (Rhabdoviruses, paramysxoviruses and Filoviridae) is unique in that their negative strand contains both (+) and (-) RNA

Orthomyxoviruses (Influenza Viruses)

Influenza viruses are important respiratory pathogens, often causing worldwide epidemics.
Influenza virus particles are usually spherical and about 100 nm in diameter. Single-stranded RNA genome.
The subtypes differ based on HA and NA glycoproteins. This determine important antigens that determine the antigenic variability of the virus and host immunity.

Clinical Finding, Diagnosis, Serology

Influenza attacks the upper respiratory tract, especially in high-risk populations, such as the elderly, the young and those with underlying conditions.
Isolation of the virus from samples, serology (testing of antibodies), and other diagnostic methods aid in their diagnosis.

Paramyxoviruses & Rubella Virus

Important respiratory pathogens in infants and young children (parainfluenza).
Paramyxovirus particles are variable in shape and size, and can range up to 700nm.
RNA is nonsegmented and linear, of negative-sense.
The viral genome is about 15kb in size.
Viruses contain six structural proteins, three involved in RNA and three that are part of the viral envelope.
Direct viral antigen detection (e.g., immunofluorescent ) is frequently done, and nasal washes, Bronchoalveolar lavages, and lung biopsies are used for viral isolation.
Lab Diagnosis include Antigen Detection, Isolation and Identification of virus, and Serology.

Rubella (German Measles)

A mild viral illness, can be dangerous to unborn fetuses.
The virus (Rubivirus) is a positive-sense single-strand RNA virus without segmentation or an envelope.
Lab Diagnosis: Clinical diagnosis can be un-reliable. Isolation and Identification of the virus, (e.g., swabs taken six days before and after rash) is made. Serology (testing for antibodies) is often helpful but serum may need to be screened and specific antibodies tested

Enteric Viruses & Rhinoviruses

Enteroviruses and rhinoviruses are common in the human gastrointestinal and respiratory systems.
Enteroviruses inhabit the alimentary tract, and rhinoviruses are in the nose, and throat.
Viral replication can lead to serious effects on the nervous system, but is dependent on the specific type of virus involved, and affects different areas of the body depending on the agent type(s).
Diagnositic testing includes culturing the virus or PCR-based approaches to finding the virus, or by identifying antibodies indicative of a past or current infection

Herpes Viruses (HSV, VZV, CMV)

Herpes viruses produce lifelong persistent infections.
They have large genomes and diverse clinical effects that range from localized infections to those with much broader host ranges and systemic effects.
Diagnosis can include identifying certain visible sores or lesions from the virus to directly identify the virus, as well as using PCR techniques or looking at antibodies indicative of past or current infections.

Oncoviruses

Viruses can be an etiological factor in several types of human cancers, including cervical and liver cancer.
Tumor viruses are important in carcinogenesis, acting as a factor in the process
Viruses can be direct or indirect factors. Most DNA tumor viruses are direct, acting immediately on growth control and replication pathways within a target tissue. RNA tumor viruses must work via an intermediate step or stages, involving different parts of cellular response and genetic machinery of a susceptible cell.
Human papilloma viruses (HPV), ,EBV (Nasopharyngeal carcinoma) and other tumor viruses can cause a number of cancers.

Hepatitis Viruses

Hepatitis viruses cause inflammation of the liver.
Types include Hepatitis A, B, C, D, E and other less common varieties.
The virus causes inflammation and or acute illness in addition to damage.
Hepatitis A is transmitted by the fecal-oral route, whereas B hepatitis is blood-borne, and C is similar. Other varieties may be more broadly transmitted or restricted.

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Description

Test your knowledge on viral assembly, replication, and cultivation methods in this comprehensive quiz. Explore the concepts of tissue tropism, viral classification, and the characteristics of different types of viruses. This quiz covers essential aspects of virology for students and enthusiasts alike.