Download Viruses

Viruses II – Interaction with
the cells
Lecture 90
Mgr. M. Jelínek
[email protected]
Plan of this lecture
1. Reproduction cycle of viruses
2. Important viral groups
Reproduction cycle of viruses
• 1. Adsorption of virion on the cell surface
and pervase inside
• 2. Reproduction of viral macromolecules in a
cell
• 3. Releasing of matured virions from a cell
Enter to a cell across cellular membrane
• Fussion of membranes, nucleocapsids is released to
cytotoplasm
• Receptor mediated endocytosis
• Injection of DNA to cytoplasm - bacteriophages
Reproduction of viruses in a cell
Reproduction (lytic) cycle – virus multiplies in a cell and spreads to other
cells, horizontal transmision
Virogeny (for bacteriophages lyzogeny) – integration to the genom (integrated
NA is called provirus), replication with cellular genom, vertical transmision
Mechanism of replication
Latence – genom of
virus is in the cell, but
viral proteins are not
expressed, or in very
low level
1) Releasing of NA from capsid
2) Syntesis of early proteins
3) Replication of NA
4) Syntesis of late, especialy structural proteins
5) Maturation of virions - autoagregation
Perzistence – genom of
virus is in cell and a
little viral proteins or
particles is produced
Releasing of virions from cells
• During of cell lysis: Iniciated by viral proteins, or by autolytical
procceses of damaged cell, necrosis
• Exocytosis virions: active procces (budding), virions move to
membrane, where are budded and leave cell by exocytosis
Results:
• Death of cell – necrosis iniciated by viral proteins, iniciated by large
budding, apoptosis,
• Cytopatic efect: damage of a cell, a tissue, an organ, can be
reversible, possibility of cell transformation
• Without cell injuring
Plan of this lecture
1. Reproduction cycle of viruses
2. Important viral groups
Clasification of viruses
• There were used system by diseases,
hosts, shape...
• So-called Baltimor´s scheme is used
• Viruses are not divided according to their
nucleid acid but replication strategy
• Because of a big number of species, viral
family are used
ds DNA viruses
•
•
•
•
Papilomaviruses – hogwarts, cervix carcinoma
Polyomaviruses: animals
Adenoviruses: respiration, gastrointestinalis
Herpesviruses: virus herpes simplex 1, virus
varicella-zoster, EBV - virus Epstein-Barr)
(infection mononukleosis, Burkitt´s lymfoma)
• Poxviruses: smallpox/variola
A strategy is similar to normal cell´s replication and
transcription. Some viruses use cell´s polymerases,
some use their own.
+ss RNA viruses
• Picornaviruses - virus poliomyelititis –
polio, hepatitis A, rhinoviruses
Vaccination:
Salk ´s – inactivated virus 1955
Sabin´ s – atenuated virus 1962
+ss RNA
• Flaviviruses – tips born encefalitis,
dengue feber, spread by insect, tips or
mosquito
hepatitis C virus – by body fluids – still no
vaccination
• Togaviry - rubeolla
- ss RNA viruses
-ssRNA viruses:
• Orthomyxoviruses – influenza A, B
segmented genom, others are non - segmented, except
of mutations, there is recombinations of fragments
Paramyxoviruses - measles, mumps
• Rabdoviruses: rabies virus
• Filoviruses - ebola, hemohargical febers
Reoviruses- dsRNA
Typical producing of
virospheres – place
of intenzive
production of viral
proteins
• Very common children
diarrhoea
• Strategy similar to RNAviruses
Rotavirus
Retroviruses a hepadnaviruses
• Retroviruses – HIV, HTLV1, Kaposhi
sarkom
• Hepadnaviruses – hepatitis B
Some examples of
ANTIVIROTICS
• Blocking of decomposition of virus
• Influenza virus A Amantadin – blocking of
ion channel on surface of capsid
• Virus enters a cell, but can not „unpack“
itself
• There exists resistance
• Inhibition of replication
• Mostly
analogs
of
nucleosids
–
fosforylation
• Inhibition of reverse transcription
• Viral polymerase is blocked with high
specifity than cell´s – possibility of
cytotoxicity
Mechanism of
effect of acyklovir
– inhibition of
synthesis of viral
DNA
Acykloguanosin
Cyclovir, Herpex, Acivir, Acivirax(), Zovirax, Aciclovir (Sanofi-Aventis) and Zovir (GSK)
INHIBITORS of REVERSE
TRANSKRIPTASE
• Important medicament of HIV a HBV
• Azidothymidine (Zidovudine; AZT)
• Inhibitors of proteases
• HIV proteases – nedeed for maturation of
virus
• It cleaves viral polyprotein on functional fu
proteins, that creates HIV virion
• Inhibition of releasing of virus from
cells
• Influenza A a B, zanamivir – tamiflu