Pengantar Virus

PENGANTAR
VIRUS
dr. Fauzia Andrini M.Kes
Bagian Mikrobiologi / Unit Ketrampilan Medik
FK UR
PENDAHULUAN
Virus
intraseluler parasit
Tdd DNA/RNA, hanya dapat bermultiplikasi di sel
host
Virion : partikel virus
diameter 10-300 nm
virus terkecil (poliovirus) = molekul Hb pada RBC
mikroskop elektron
Virus terbesar : Poxvirus
Taksonomi : ordo (-virale), famili (-viridae),
subfamili (-virinae), genera (-virus)
STRUKTUR VIRUS
Bentuk virus
subunit yang membentuk protein
coat (kapsid)
DS/SS DNA atau SS/DS RNA
Asam nukleat dikelillingi oleh protein coat (kapsid)
Nukleokapsid
protein coat + asam nukleat
Susunan subunit
simetri kapsid
Ikosahedral
dan helical
“naked” or with outer envelope
Spikes
struktur protein/glikoprotein yg
menonjol, berperan pd kontak awal dgn sel host
Simetri Kapsid
Helical
disusun oleh subunit protein (protomer)
yg berikatan satu sama lain mengelilingi as.nuk
Ikosahedral
disusun oleh subunit protein
(kapsomer)
Envelope
Terdiri dari lemak dan
polisakarida
Ada virus yg
berenvelope, ada yg
tdk
Envelope
host cell
membran
escape
from
nucleus/cytoplasm
host cell by “budding”
Struktur Virus
Virus yang berenvelope
A = enveloped helical virus ; B = envelope
icosahedral virus
Virus berenvelope : > sensitif thd panas,
detergen, alkohol
Adenovirus & Virus Influenzae
KLASIFIKASI VIRUS
Tipe asam nukleat (DNA / RNA)
Simetri kapsid
Ada / tidaknya envelope lipid
Kriteria : tropisme (spesifisitas host (virus
binatang/manusia), bagian host (virus
SP/SSP), patogenisitas, transmisi
KLASIFIKASI VIRUS
Virus non envelope
Picornavirus
Papovavirus
Reovirus
Adenovirus
Parvovirus
Bentuk lain
Lebih simpel daripada
virus
Viroid
molekul RNA
tanpa pelindung protein
penyebab penyakit pd
tanaman
Prion
gen (-), tdd
spongiform
protein
encephalopaties pd
hewan, Creutzfeldt-Jakob
disease in human
Bakteriofaga
Virus yang
menginfeksi bakteri
Replikasi Virus
Virus have no ribosom (for protein
synthesis), no mitochondria (energy
production)
must invade host to multiply
Tahapan replikasi virus manusia :
attachment, penetration, uncoating,
biosintesis, assembly, release
Attachment / adsorption
Highly specific reaction
perlekatan virion
attachment proteins dgn cell surface
protein
Reseptor HIV (CD4) ; Rabies (acetylcholine
receptor)
Tissue tropism
Antibodi netralisasi (neutralizing antibody)
hrs jd sblm adsorpsi (prevent attaching)
spesifik utk virion attachment protein
Penetrating : non envelope by
endocytosis & envelope
Uncoating dan biosintesis
Uncoating
As nukleat virus dilepaskan dari
kapsid
Biosintesis
Ekspresi gen dan replikasi genom
First step : sintesis mRNA :
a.
Virus DNA
use host cell DNA-dependent
RNA polymerase (kec poxvirus krn bereplikasi
pd sitoplasma)
b.
Virus RNA
replikasi pd sitoplasma
* Retrovirus : integrasi DNA copy dgn DNA host
Virus RNA
Produksi mRNA virus utk sintesis protein
viral pd ribosom seluler (host) !!
SS RNA (+) polaritas
RNA tsb dpt lgs
mjd mRNA (picorna, toga, coronavirus)
SS RNA (-) polaritas dan DS RNA
membentuk mRNA via enzim polimerase
viral (Rabies,influenzae, reovirus)
SS RNA (+) polaritas
retrovirus
transkripsi mjd DNA copy by reverse
transcriptase virus
mRNA by RNA
polimerase host
Replikasi genom
mRNA
translasi oleh ribosom sel host
into viral protein :
a. Early protein
enzim utk replikasi
genom
b. Late protein
protein struktural utk
progeny virus
Latent infection
virus yg tdk segera
memulai biosintesis
dormant
virus
Herpes latent pd sel saraf
demam,
stress, sinar matahari sbg trigger
Assembly
Encapsidation
penggabungan komponen utk
membentuk virion
Construction of capsid and nucleocapsid
Release
a.
b.
-
Release
pelepasan dari
sel host :
Merusak sel host by loss
cell function or apoptosis
(most naked virus)
Envelope virus budding :
Cell death (jarang), misal
HIV-1
Cell survival : repaired
directly of plasma
membrane
Entry, dissemination, sheeding of
blood borne virus
REPLIKASI VIRUS HIV
Retrovirus
HIV
penyebab AIDS
Virus memasuki sel dg
fusi dg membran sel
atau masuk ke
vakuola & dilepaskan
ke dalam sel
Virus & Penyakit
DHF
Virus Dengue
Sal Pernaf
Adenovirus, Influenzae, Rhinovirus
SSP
poliovirus, coxsackievirus
Mata
Herpes
Hati
Hepatitis
TORCH
HIV - AIDS
SEKIAN DAN
TERIMA KASIH