Name: MCPH 4
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MCPH 4 - Details

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• Distinguished from other infectious agents as very small and filterable

VIRUSES

General Characteristics OF Viruses

1 Obligatory Intracellular parasites 2 Contain a single type of nucleic acid 3 Contain protein coat that surrounds the nucleic acid 4 Multiply inside living cells by using the synthesizing machinery of the cell 5 Cause the synthesis of specialized structures that can transfer the viral nucleic acid to other cells. 6 Few or no enzymes for their own metabolism

There are __ number of antiviral drugs developed a. few b. many

A. few It is difficult to create a drug which does not interfere with the normal functioning of the host cell which viruses use as machinery

Viruses contain plasma membrane

Viruses are what type of parasites?

Intracellular parasites

Can viruses pass through filters?

No Too small size

Viruses contains both DNA and RNA

No, they either have DNA or RNA only

Are viruses sensitive to antibiotics?

No Only Antiviral works

Are viruses affected by interferons?

Yes They are proteins secreted by the immune system to fight viruses

Naturally occurring proteins that are made and secreted by the cells of the immune system.

Interferons

• For the virus to infect cell, the outer surface of the virus must what?

Chemically interact with the specific receptor sites of the cells If achieved, it will be held by hydrogen bond

• When infected with a virus, the host’s immune system is stimulated to produce what?

Antiodies

• Proteins that interact with the surface protein of the virus • These interactions will either inactivate or stop the infection

Antibodies

• Viruses genes are susceptible to what?

Mutation Help them escape antibodies

Receptor sites of bacteria is found on

• The cell wall, fimbriae, or flagella.

Receptor sites for animals or humans is found on

• Plasma membrane

• Viruses that infect bacteria

Bacteriophage

Viral size of viruses

• 20 to 1000 nm in length can be determined by electron microscope

A complete, fully developed infectious viral particle which is composed of nucleic acid serves as a vehicle for transmission from one host cell to another

Virion

• Can be linear, circular, or in separate segments • single or double stranded

Nucleic acid

What are the structures of Virion?

1 Nucleic acid 2 Capsid 3 Envelope

• a protein coat that surrounds the nucleic acid. • The structure is usually determined in the type of nucleic acid and accounts for most of the mass of viruses

Capsid

• Each capsid is composed of protein subunits called what?

Capsomeres

• a single type of protein or several types.

Capsomeres

• Covers the capsid, outer surface • Usually comes from the host cell’s plasma membrane plus through the process of extrusion

Envelope some envelope have spikes

• Serve as attachment, protection and identification

Spikes

• Are capsid that are not covered by enveloped that protects the nucleic acid from nuclease enzymes

Nonenveloped viruses

Enzymes that cleave the nucleic acid in biological fluid; it also promotes attachment to susceptible hosts

Nuclease enzymes

• The process of forcing out or migration from its normal processes

Extrusion

GENERAL MORPHOLOGY of viruses; types;

• Helical Viruses • Polyhedral Viruses • Enveloped Viruses • Complex Virus

Viruses are classified by what?

• differences in the structures of their coats

• This is used to detect antibodies and antigens.

Serological methods

• This is used to detect antibodies and antigens.

Serological methods

• This is used to detect antibodies and antigens.

Serological methods

• This is used to detect antibodies and antigens.

Serological methods

• This is used to detect antibodies and antigens.

Serological methods

• Long rods • Rigid or flexible • The nucleic acid is found within a hallow-cylindrical capsid in helical structure

Helical Viruses

• The capsid is usually shaped as an icosahedron

Polyhedral Viruses

• A polyhedron with 20 triangular faces and 12 corners

Icosahedron

• Roughly spherical • They can be helical or polyhedral viruses

Enveloped viruses

• Complicated structure • Different shape

Complex virus

Examples of Helical Viruses

Rabies Virus, Ebola (Virus) hemorrhagic fever

Examples of Polyhedral viruses

Adenovirus, Poliovirus

Examples of Enveloped viruses

Influenza virus (Enveloped helical) Herpes Simple Virus (Enveloped polyhedral)

Examples of Complex virus

Bacteriophage o Head part is polyhedral o Tail is helical

1. • For the family name, we usually add the suffix __ 2. • For the genus name, we add the suffix __

1. –viridae 2. –virus

What method used in Growing Bacteriophages in the Laboratory?

Solid media: Plaque method • Procedure is to grow the bacteria then add the virus to multiply

How to count viruses?

• By looking at the plaques or white cotton appearance The counting is through PFU

Growing Animal Viruses in the Laboratory 3 METHODS

1 Living animals 2 Embryonated eggs 3 Cell culture

• It is used as a diagnostic procedure for identifying and isolating a virus from clinical specimen.

Living Animals

• A fairly convenient and inexpensive method. • They are widely used in viral isolation and even in vaccines.

Embryonated eggs

• Replaced the embryonated eggs as the preferred growth medium for many viruses • The cells are grown in culture media therefore it can be propagated and handled like bacterial cultures

Cell culture (Normal and Transformed Cells)

In culture media, Grow in a monolayer across the container.

Primary cells

In culture media, Grow in several layers

Transformed cells

O They develop from human embryos and they can be maintained for about 100 generations. And, they are widely used for cultivating viruses that require human hosts.

Transformed or Diploid Cell Lines

They are derived from tissue cells and they tend to die out after a few generations

Normal or Primary Cell Lines

Viral Identification

• Electron Microscopy • Serological methods • RFLPs • PCR

• This is used to detect antibodies and antigens.

Serological methods

Example of serological method

Western blotting

• A laboratory method used to detect specific protein molecules from among a mixture of proteins.

Western Blotting

• This test uses amplicons

RFLPs (restriction fragment length polymorphs)

• A piece of DNA or RNA that is the source and/or product of amplification or replication events

Amplicons

• At the end of the process it will cause lysis and death of the host cell.

Lytic cycle

• At the end of the process it will not kill the host cell, rather the host cell will remain alive.

Lysogenic cycle

• This is an active cellular process by which nutrients and other molecules are brought into the cell. • It means the whole structure of the cell will enter the plasma membrane.

Endocytosis

• The viral envelope will fuse with the plasma membrane and will release the capsid into the cell’s cytoplasm.

Fusion

• An enzymatic removal of the Capsid proteins • Separation of the viral nucleic acid from its protein coat.

Uncoating

1. If DNA virus, biosynthesis is in the __ 2. If RNA virus, biosynthesis is in the __

1 nucleus 2 cytoplasm

• Late manifestation because of the slow viral infection or slow synthesis

Cancer cells

• It is when the viral DNA or RNA, and Capsid proteins will assemble to form a complete virus

Maturation

• Study of viruses

Virology

Are used to treat infectious diseases

• Antimicrobial drugs

Differences between Disinfectants and Antimicrobial drugs

• Disinfectants are often need to act within the host • Antimicrobial drugs, to be called ideal, should kill the harmful microorganisms without damaging the host

• The mechanism of inhibition in which antibiotic comes from

Antibiosis

• A substance produced by microorganisms that in small amounts inhibits another microorganism

Antibiotic

The fully synthetic sulfa drugs are technically antimicrobial drugs and not __ which is a distinction often ignored in practice

Antibiotics

• Succeeded in first clinical trials of penicillin

1940, Howard Florey and Ernst Chain

• Mostly, our antibiotics is from a strain of microorganisms such as what?

Streptomyces, bacillus, penicillum, and cephalosporium

Examples of gram positive rods

Bacillus subtilis Bacillus polymyxa

Examples of ACTINOMYCETES

Streptomyces nodosus Streptomyces venezuelae Streptomyces aureofaciens Streptomyces erythraeus Streptomyces fradiae Streptomyces griseus Micromonospora purpureae

Examples of FUNGI

Cephalosporium spp. Penicillium grisofulvum Penicillium notatum

Source of Bacitracin

Bacillus subtilis

Source of Polymyxin

Bacillus polymyxa

Source of Amphotericin B

Streptomyces nodosus

Source of Chloramphenicol

Streptomyces venezuelae

Source of Chlortetracycline

Streptomyces aureofaciens