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
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