Introduction to Virology Flashcards by Unknown Unknown

They are obligate, intracellular parasites.

Viruses

How well did you know this?

Not at all

Perfectly

They are infectious agents consisting of nucleic acid molecule packaged into a protein (capsid)

Viruses

How well did you know this?

Not at all

Perfectly

Aside from protein capsids, viruses may also be covered by

lipid envelope
glycoproteins

How well did you know this?

Not at all

Perfectly

Aside from protein capsids, viruses may be ____ (_____) or non-enveloped

enveloped (lipid envelope)

How well did you know this?

Not at all

Perfectly

Nucleic acid of viruses can be either ____ or ____

How well did you know this?

Not at all

Perfectly

They can infect all known life-forms

Viruses

How well did you know this?

Not at all

Perfectly

They are only able to multiply within living cells of hosts

Viruses

How well did you know this?

Not at all

Perfectly

Viruses have no ____ which means they cannot synthesize ATP

ribosomes

How well did you know this?

Not at all

Perfectly

Viruses have a wide range of _____ and _____

structures
genomes

How well did you know this?

Not at all

Perfectly

It’s the process by which a virus produces disease in the host.

Viral pathogenesis

How well did you know this?

Not at all

Perfectly

These genome carried by a protein capsid is enough to enter cells, hijack the host machinery to replicate and persist over time.

DNA or RNA genome

How well did you know this?

Not at all

Perfectly

Modes of Viral Infection

Local Infection
Generalized Infection

How well did you know this?

Not at all

Perfectly

This means the cellular damage remains at the initial site of infection and replication such as the skin, mucous membranes, respiratory, GI, genital tract

Local infection

How well did you know this?

Not at all

Perfectly

Sites of Local Infection

Skin
Mucous membranes
Respiratory
GI
genital tract

How well did you know this?

Not at all

Perfectly

It refers to when virus replicates at primary site then spreads via the blood (viremia) or lymphatics (replicates in lymph nodes); reaches target organ, replicates, then spreads via primary viremia; reaches other target organs, replicates then spreads via the bloodstream (secondary viremia)

Generalized Infection

How well did you know this?

Not at all

Perfectly

How does the virus spread after replicating at the primary site, spreads, and after reaching the target organ?

via Primary viremia

How well did you know this?

Not at all

Perfectly

How does the virus spread once it replicated after reaching the other target organs?

via Secondary viremia

How well did you know this?

Not at all

Perfectly

An example of a disease you can get in the virus-infected local site

Rhinovirus

How well did you know this?

Not at all

Perfectly

An example of the disease you can get in a virus-infected target organ

Parainfluenza type 3
rabies

How well did you know this?

Not at all

Perfectly

An example of the disease you can get in the target organ via primary viremia

Carnivore protoparvovirus 1

How well did you know this?

Not at all

Perfectly

An example of the disease you can get in the target organ via secondary viremia

Canine morbillivirus

How well did you know this?

Not at all

Perfectly

Potential Consequences of virus-animal relationships

Animal is resistant to viral infection
Asymptomatic or subclinical infection
Acute viral infection
Chronic viral infection
Tumor formation

How well did you know this?

Not at all

Perfectly

It is a potential consequence of virus-animal relationship where in the existence of death, recovery, or persistent infection are involved.

Acute viral infection

How well did you know this?

Not at all

Perfectly

It’s a potential consequence of virus-animal relationship whereas no relationship is even established.

Animal is resistant to viral infection

How well did you know this?

Not at all

Perfectly

It's a potential consequence of virus-animal relationship whereas there is the existence of recovery or persistent infection

Asymptomatic or subclinical infection

It is a potential consequence of virus-animal relationship where in the recurrent clinical disease or persistent infection are involved

Chronic viral infection

It's a potential consequence of virus-animal relationship where in viruses are tumorigenic.

Tumor formation

It does not always lead to disease but can lead to acute and chronic infections in the susceptible host.

Viral infection

Viral infection can lead to such infections as it does not always lead to disease

Acute and Chronic infections

In the virus-host relationship, some ____ may be resistant.

hosts

In the virus-host relationship, some ____ are tumorigenic.

viruses

Variation in size of Viruses

20-100 nm diameter

It is a degree of pathogenicity of a virus.

Virulence

The factors that influence the degree of virulence are:

- Production of cytotoxic effects by the virus - Replication strategies of the virus. - Tissue tropism - Dose of the infecting virus - Route of exposure

Viruses are composed of?

- Nucleic acid - Capsid

The nucleic acid of viruses can be either?

- DNA - RNA

It is the protein coat of viruses.

Capsid

Properties of Viruses

- Nucleic acid - General morphology - Strategy of multiplication/ replication

Form/ structure of nucleic acid can be:

- Circular - Linear - Separate molecules (segmented)

Types of morphology of Viruses

- Helical viruses - Polyhedral viruses - Enveloped viruses - Complex viruses

Example of a polyhedral virus

Icosahedron

How many triangular faces does icosahedron and what is the morphology of this virus?

- 20 - Polyhedral viruses

Restriction of viral infection and/or replication to certain cells or tissues

Viral tropism

Viruses with ____ ______ can replicate in a variety of cell types, organisms and host species.

broad tropism

Example of a virus with broad tropism.

Pseudorabies (Suid alphaherpesvirus I)

This virus infects the respiratory tract, CNS, and fetus in swine. It is also fatal to other animal species except monkeys.

Pseudorabies (Suid alphaherpesvirus I)

Specific types of cells a virus can infect in its host species represent the _____ of the virus

Host range

They are usually species-specific.

Viruses

It is determined by attachment sites (receptors on the cells).

Host range

Classification of viruses

- Animal/ human virus - Plant virus - Bacterial virus (bacteriophage)

What is the classification of viruses based on?

- Type of nucleic acid - Strategy for replication - morphology

Virus family names end in ____

-viridae

Virus Order names end in ____

-virales

Virus Genus names ends in ____

-virus

It is a group of viruses sharing the same genetic information and ecological niche.

Viral species

Only half of viruses are currently classified in what taxon?

order

How many viruses are only currently classified in orders?

Half of viruses

Virus subfamily names end with ____

-virinae

It is generally the "common name" of the virus.

Species

Classification of Species

- Subtypes - Serotypes - Strains - Isolates - Variants

Serotypes include _________ which includes strains human rhinovirus IA and human rhinovirus IB

Human rhinovirus I

The Baltimore classification system is made by this Nobel laureate. (And what year?)

David Baltimore (1970s)

This classification of viruses classify them based on their genome and replication strategy,

Baltimore classification systm

The Baltimore Classification system classified viruses based on what?

- their genome - replication strategy

How many classes are there in the Baltimore classification system?

What are the 7 classes in the Baltimore classification system?

class I: dsDNA viruses class II: ssDNA viruses class III: dsRNA viruses class IV: positive-sense ssRNA viruses class V: negative-sense ssRNA viruses class VI: RNA viruses that reverse transcribe class VII: DNA viruses that reverse transcribe

Viruses replicate intracellularly using the host cell machinery to create new infectious particles called ____

virions

What does the virus depend on to undergo several steps of replication?

Depending on the type of nucleic acid

Stages of Viral Replication

1. Attachment 2. Penetration 3. Uncoating 4. Biosynthesis 5. Assembly 6. Release

They are made and assembled into new virions that are released by budding.

- Viral RNA - Viral proteins

In influenza virus infection, they attach the virus to a host epithelial cell.

viral glycoproteins

It is endocytosed.

Virus

Laboratory Detection of Viruses being done.

- Electron microscopy - Virus isolation - Detection of viral antigen - Detection of viral nucleic acids - Detection of antibodies against virus.

It's an essential tool for visualizing viruses because their size is too small to visualize by light microscopy.

Electron microscopy

Types of Electron microscopes used to detect viruses.

- Transmission electron microscopes (TEM) - Scanning Electron microscopes (SEM)

Transmission electron microscopes (TEM) and Scanning Electron Microscopes (SEM) can magnify up to how many times?

50 to 50 million times

Viruses are way too small to be even visualized by this type of microscopy.

Light microscopy

Viruses can be isolated by growing them in the appropriate host cells such as?

- in vivo (e.g. egg) - in vitro (e.g. baby hamster kidney (BHK) cells)

Viruses can then be purified via?

- Centrifugation (high-speed ultracentrifuge) - Filtration (e.g. 0.2 micrometer)

What is the pore size in filtration that removes other microorganisms and allows viruses to pass through?

0.2 micrometer

It uses primary and/or secondary antibodies for detection.

Detection of viral antigen

In the detection of viral antigen, usage of _____ are applied for detection?

primary and/or secondary antibodies

What are used for the detection of viral antigen?

- Enzyme-linked immunosorbent assay (ELISA) - Immunofluorescence - Immunohistochemistry

What are used for the detection of viral nucleic acids?

- Polymerase chain reaction - RT-PCR - Real-time quantitative PCR (Real-time qPCR)

What are used for the detection of antibodies against virus?

- ELISA - Immunochromatography (rapid test)

Where do viruses only replicate?

in living cells

They are formerly used extensively for the cultivation of viruses.

Embryonated eggs

Such techniques have greatly improved to cultivate viruses.

Cell culture techniques

Three routes of virus infection:

- Chorioallantoic membrane - Amniotic cavity - Yolk sac

Techniques for tissue cultures

1. Explant cultures 2. Cell cultures 3. Cell lines are passaged, 4. For primary cell lines, number of passages in finite 5. Viruses exhibit microscopic changes on the cells 6. Determination of virus concentration

It is wherein explant tracheal cultures are required for some coronaviruses.

Explant cultures

An example of explant culture

- explant tracheal cultures are required for some coronaviruses

Cell cultures can be?

- primary - semi-continuous - continuous

An example of primary cell culture

Chicken fibroblast from chick embryo

An example of continuous cell culture

baby hamster kidney (BHK) cell line

What classification of cell culture is the example chicken fibroblast from chick embryo be under in?

Primary cell culture

What classification of cell culture is the example baby hamster kidney (BHK) cell line be under in?

Continuous cell culture

It means cell lines are transferred or sub-cultured from one culture vessel to another.

Cell lines are passaged.

For primary cell lines, the number of passages is ____

finite

The finite number of primary cell lines has a what?

endpoint

What is the endpoint called in the finite number of passages in primary cell lines?

Hayflick limit

The microscopic changes on the cells that viruses exhibit.

Cytopathic effect (CPE)

Various titration methods to determine virus concentration:

- 50% lethal dose (LD₅₀) in mice or embryonated eggs - 50% tissue culture infective dose (TCID₅₀) in cells