Virology

Reproduction and cultivation

Types of virus interaction with cell

Abortive. When abortive infection replication of virus progeny is interrupted in someone stage.

Productive. Productive infection results in viral replication with the production of virus progeny and death of the host cel.

Integrative (latent, persistent). Integrative infection occur when virus genome integrate into cell chromosome..

Stages of viral replication

1. Adsorption (attachment)

2. Penetration

3. Uncoating of the viral genome

4. Gene expression, transcription, early and late viral protein synthesis

5. Genome replication

6. Assembly of progeny virions

7. Release virions from cell

Early events

Middle events

Late events

Adsorption of animal viruses

Entry of enveloped viruses into host cell

a) b)

General scheme replication of poxviruses

Replication in DNA viruses

Replication in RNA viruses

Maturation of virions

Assembly of viruses is a self-assembly process

Tobacco mosaic virus maturation

Nucleus of a cell, containing a crystalline mass of adenoviruses

Release of mature viruses from host cell

Budding release of retroviruses

Maturation of an enveloped virus

Основні ефекти, що викликають віруси в клітинах: Морфологічні (ЦПД, вірусні включення) Фізіологічні (зміна клітинних мембран – плинність, ліпідний

склад, мембранний потенціал) Біохімічні (переключення генетичної інформації, зміни у

обмінних процесах, зміни у цитоскелеті клітин, поява нових ферментів)

Генотоксичні (руйнуваня або зміни геному клітини, хромосомні аберації)

Біологічні (поява нових антигенів, малігнізація)

Methods cultivating of animal viruses

Live animal organism Chicken embryo Cell (or tissue) culture

Cultivation viruses in newborn mice

Advantages:

Study of pathogenesis

Examination of vaccines and antiviral drags

Disadvantages:

Not-universal method

Presence own viruses and bacteria in animal organism

Sign of viral infection in animals

Mouse with paralysis of back extremities

Death

Symptoms of illness

Newborn mice that are behind in development

Virus cultivation in bird embryos

Advantages:

Standardized system

Sterile system

Possibility to cultivate viruses and make viral vaccines

Disadvantages:

Not-universal method

Possible presence own latent viruses

Virus cultivation in bird embryos

The signs of viral growth in bird embryos are:

death of the embryo

defects in embryonic development

pocks ( localized areas of damage in the membranes )

Other methods for detection of viruses that do not produce visible changes in embryo:

direct examination with electron microscope

hemagglutination test

serological test

Pocks developing on a chorioallantoic membrane caused by herpes simplex viruses I and II types

Cell culture

there is the aggregate of human, animal or plant cells that are cultivated in vitro with using of complex nutrient mediums and conditions of cultivation

Cell cultures

Cells of macaque kidneys

Cells of human embryo

HeLaCells of pig embryo (RES)

Methods detection of viruses in cell culture

Cytopathic effect (CPE) Inclusion body formation Coloured test Plaque formation under agar or bentonit Hemadsorbtion Hemagglutination Detection viral antigens in infected cell with

serological test Detection of virions under electron microscope

Types of viral CPE

Type of CPE Instance

Cell rounding and detachment from the substrate

Smallpox virus, influenza virus

Cell lysis Polioviruses, togavirus

Syncytium formation (a mass of fused cells)

Respiratory syncytial virus, herpes simplex viruses

Transformation and proliferation. Oncogenic viruses as retroviruses, some herpesviruses

Cell lysis caused by enterovirus

Normal cells Vero Infected cells Vero after poliovirus reproduction

Syncytium formation caused by herpesvirus

CPE caused by adenovirus

Intact cells HeLa Clumping of infected cells

Inclusion body formation

Gvarniery bodies

Negry bodies

Plaque formation

Plaques under agar

Plaques under bentonit

Normal cells Infected cells

Plagues

Detection viruses that have hemagglutinins

Hemagglutination Hemadsorbtion

Red cells Viruses Hemagglutination

Attachment phages on bacterial surface

Phages that attached to bacterial flagellum

Penetration of tailed phage

Multiplication of bacteriophages

Releasing phages from ruptured bacterium

A bacterial cell, crowded with viruses, has ruptured and released numerous virions that can attack nearby susceptible cells.

The lysogenic state in bacteria

Lysogeny

is a condition in which viral DNA is inserted into the bacterial chromosome and remains inactive for an extended period.

Virulent phage propagates in bacteria and induces its death

Temperate phage after entering in the bacterium integrates their DNA in the chromosome of the host cell and turn into prophage.

Life cycle of phage lambda – lytic and reproductive infection

Lysogenic cell is the bacterial cell carrying a prophage

Animal DNA viruses families

Family Strand type

Capsid type Envelope Size

Common Name of Important Members

Poxviridae Double None + 130-300 Smallpox virus; complex virus; brick-shaped

Herpes-viridae

Double Icosahedral + 150-200 Herpes simplex virus, Varicella zoster virus, Epstein-Barr virus

Adeno-viridae

Double Icosahedral - 70-90 Human adenoviruses

Papova-viridae

Double Icosahedral - 45-55 Human papillomavirus

Hepadna-viridae

double Icosahedral + 42 Hepatitis B virus

Parvo-viridae

Single Icosahedral - 18-26 Parvovirus B19

Animal RNA viruses families (1)

Family Strand type

Capsid Type Envelope Size (nm)

Common Name of Important Members

Picorna-viridae

Single Icosahedral - 20-30 Hepatitis A virus, poliovirus, coxsackieviruses, rhinoviruses

Calciviridae Single Icosahedral - 35-40 Norwalk virus

Togaviridae Single Icosahedral + 45-70 Rubella virus, western equine encephalitis

Flaviviridae Single Icosahedral + 40-70 Yellow fever virus, Japanese encephalitis virus

Paramyxo-viridae

Single Helical + 125-250 Parainfluenza virus, mumps virus, measles virus

Animal RNA viruses families (2)

Family Strand type

Capsid Type Envelope Size (nm)

Common Name of Important Members

Filoviridae Single Helical + 790-970 Ebola and Marburg viruses

Bunyaviridae Single Helical + 90-100 Bunyamwera virus, Hanta virus

Reoviridae Double Icosahedral - 60-80 Human rotavirus, Colorado tick fever virus

Orthomyxo-viridae

Single Helical + 80-120 Influenza viruses

Animal RNA viruses families (3)

Family Strand type

Capsid Type

Envelope Size (nm)

Common Name of Important Members

Rhabdo-viridae

Single Helical + 60-75 Rabies virus

Retroviridae Single Icosahedral + 100 Human immunodeficiency virus (AIDS), oncoviruses

Arenaviridae Single ? + 50-300 Lassa virus; lymphocytic choriomeningitis virus

Corona-viridae

Single Helical + 80-130 Human infectious bronchitis and corona viruses