Virus Cultivation Methods and Techniques

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Questions and Answers

What is the primary purpose of cultivating viruses?

To produce genetically engineered crops

To create antiviral drugs

To isolate and identify viruses in clinical samples (correct)

To genetically modify viruses for research

Which of the following is NOT a method for virus cultivation?

Inoculation into embryonated egg

Fermentation (correct)

Animal inoculation

Cell Culture

Why are plant cells considered challenging for virus cultivation?

They produce enzymes that deactivate viruses

They have an impermeable cell wall and cannot undergo cell division

They replicate too slowly to support virus growth

They lack specific receptors for virus entry (correct)

What preparation step is necessary before inoculating a virus into an embryonated egg?

Disinfecting the shell surface Signup and view all the answers

Which of the following statements about virus cultivation is true?

Viruses are obligate intracellular parasites. Signup and view all the answers

What is the role of minute scratch techniques in plant virus cultivation?

To facilitate virus entry into plant cells Signup and view all the answers

Which type of cells are used in tissue culture for virus cultivation?

Living eukaryotic cells Signup and view all the answers

What is the recommended age for chick embryos when inoculating for virus cultivation?

7-12 days old Signup and view all the answers

What is one advantage of using embryonated eggs for virus isolation compared to animal inoculation?

It provides a self-supporting environment for viral propagation. Signup and view all the answers

Which method is used to check the viability of the embryo in the egg before inoculation?

Candling the egg. Signup and view all the answers

What type of evidence can indicate the presence of a virus in inoculated eggs?

Mortality and deformities of the embryo. Signup and view all the answers

Why are embryonated eggs considered a suitable system for viral propagation?

They are an intact unit with their own sterile environment. Signup and view all the answers

What is one disadvantage of using animal inoculation for virus cultivation?

It requires a longer observation period. Signup and view all the answers

What route is commonly used for inoculating viruses in laboratory animals?

Intraperitoneal and subcutaneous routes. Signup and view all the answers

Which of the following statements is true regarding the use of embryonated eggs for viral research?

Embryos do not possess any defense mechanisms against viruses. Signup and view all the answers

What was the first instance documented for live inoculation in viral studies?

Investigation of yellow fever virus in human subjects. Signup and view all the answers

What is a major disadvantage of using animal inoculation for viral studies?

Limited variety of viruses that can infect animals Signup and view all the answers

Which type of cell culture is derived from human or animal cells and has a limited lifespan?

Primary cell culture Signup and view all the answers

What is a primary advantage of using cell cultures over animal inoculation?

Cell cultures are more convenient to handle Signup and view all the answers

Diploid cell cultures are primarily used for what purpose?

Isolation of fastidious viruses Signup and view all the answers

What type of culture is specifically mentioned as being used for the isolation of coronavirus?

Organ culture Signup and view all the answers

Continuous cell lines are primarily derived from which type of cells?

Cancer cells Signup and view all the answers

Which of the following is a limitation of primary cell cultures?

They have a restricted lifespan Signup and view all the answers

In cell culture, why is the use of embryonated chicken eggs becoming less common?

Cell cultures offer better convenience Signup and view all the answers

Study Notes

Cultivation of Viruses

Virus cultivation is essential for virus isolation
Viruses are obligate intracellular parasites; they replicate only within cells.
The primary aims of virus cultivation are:
- Isolating and identifying viruses in clinical samples
- Researching viral structure, replication, genetics, and effects on host cells
- Preparing viruses for vaccine production

Cultivation of Plant Viruses

Plant cells lack virus receptors, but have cell walls made of cellulose and hemicellulose
Cultivation is done by artificially wounding plant epidermis.
Wounds need to be very small to prevent cell death.
Fine powders (e.g., sand, carborundum, glass powder) are used to scratch epidermis.
Viral suspensions are sprayed onto the wounded area.
Infected plants are grown in glasshouses, away from other plants, to obtain pure virus suspensions.
Viruses are subcultured in young plants of the same species.

Methods of Virus Cultivation

Three basic laboratory substrates are used:
- Embryonated eggs
- Tissue culture
- Animal inoculation

Virus Cultivation: Animal Inoculation

Viruses not cultivable in eggs or tissue culture are sometimes cultivated in laboratory animals.
Animals selected are healthy and free of communicable diseases.
Inoculation methods include intraperitoneal and subcutaneous routes.
Viruses multiply in the host, causing disease.
Observation of animals for disease symptoms and death is critical.
Infected tissue is examined for viruses, which are then isolated and purified.
Animal inoculation was initially used with human volunteers in the study of yellow fever virus.

Advantages of Animal Inoculation

Used to diagnose, determine pathogenesis, and clinical symptoms.
Production of antibodies can be identified.
Primary isolation of certain viruses.
Studying viral replication, immune responses, epidemiology, and oncogenesis reliably using mice.

Disadvantages of Animal Inoculation

Expensive and difficult to maintain animals.
Difficulty selecting animals appropriate for a particular virus.
Some human viruses either cannot be grown in animals or cause no noticeable disease in animals.
No model systems are provided for vaccine development.
Generation of escape mutants is possible
Animal welfare concerns.

Virus Cultivation: Embryonated Eggs

Pasture first used embryonated hen's eggs for virus cultivation in 1931.
The chosen egg type affects cultivation.
Viruses are inoculated into 7- to 12-day-old chick embryos.
Eggs are prepared for inoculation by disinfecting the shell (e.g., with iodine) and penetrating it with a sterile drill.
Eggs are candled to confirm embryo health before inoculation.

Embryonated Eggs: Use and Advantages

Though not all viruses can grow in embryonated eggs, many do.
Useful for rapid virus isolation and vaccine/antigen production.
More economical and convenient than animal inoculation.
Inoculation can be performed through amniotic, allantoic, chorioallantoic membrane, yolk sac, or intravenous/intraembryonic routes.
Detection methods include mortality, deformities, hemorrhages, lesions, presence of specific antigens in the fluids using HI, SN, FAT or other serological tests.
Eggs are a suitable means for virus isolation, stock culture maintenance, and vaccine production.
Advantages
- The rapid differentiation of embryonic cells in a closed, sterile environment fosters virus replication efficiently.
- Eggs offer a self-supporting unit complete with sterile environment and nourishment.
- They provide several embryonic tissues receptive to viral replication.
- Defence mechanisms are not engaged in embryonated eggs.
- They are cost-effective and easy to maintain.

Virus Cultivation: Cell Cultures

Prior to cell culture, viruses were propagated only using whole animals or embryonated eggs.
Cell cultures have superseded embryonated eggs as the preferred growth medium for many viruses
They consist of cells grown in culture media in a laboratory setting.
- Can be handled and propagated as bacterial cultures, more convenient than whole organisms (animals or eggs).

Types of Tissue Culture

Three main types of tissue culture
- Organ culture
- Explant culture
- Cell culture

Types of Cell Culture

Primary cell culture
- Derived from animal or human cells.
- Limited lifespan, cannot be serially cultured.
- Suitable for primary virus isolation and vaccine production.
- Examples include monkey kidney cells and human amnion cells.
Diploid cell culture (semi-continuous cell lines)
- Contain the same chromosome number as parent cells.
- Used for isolating fastidious viruses and producing viral vaccines.
- Examples include human embryonic lung (HEL) and rhesus embryo cells.
Heteroploid culture (continuous cell lines)
- Derived from cancerous cells.
- Can be maintained through subculture or deep freezing.
- Not useful for vaccine production due to their cancerous origin.
- Examples include HeLa (cervical cancer), Hep-2 (laryngeal cancer), Vero (monkey kidney), and BHK-21 (hamster kidney).

Advantages of Cell Culture

Relative ease, broad spectrum, cheaper, and more sensitive than other methods.

Disadvantages of Cell Culture

Requires trained technicians with experience.
State-level health labs usually don't perform virus isolation in-house.
Samples are often sent to central lab facilities for analysis.

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Description

This quiz covers the essential aspects of virus cultivation, including the methods used for isolating and identifying viruses in clinical and plant samples. It delves into the principles behind virus propagation and the techniques implemented for effective research and vaccine production. Test your understanding of the intricacies of virus cultivation processes across different organisms!