VIROLOGI

INAYATI HABIB

Sifat-sifat Umum Virus

Penyebab infeksi terkecil, 20 - 300nm. Genom: RNA atau DNA saja, terbungkus

protein, kadang dikelilingi membran lipid di luar sel: virus non aktif ; replikasi pd sel

hidup disebut Parasit tk. Genetik/obligat intraseluler

asam nukleat: informasi genetik agar sel hospes msintesis makromolk.u/ virus baru

hospes beragam, inf pd org unisel/tk tinggi

Perbedaan Virus dg Mikroorganisme lain

Gambar Struktur Virus

Definisi bagian -bagian Virus

Kapsid: lapisan protein yg menutupi genom asam nukleat

nukleokapsid: kapsid + asam nukleat yang diselubungi

unit struktur: blok penyusun protein dasar dari lapisan

kapsomer: unit morfologik pada mikroskop elektron pada permukaan partikel virus ikosahedral

Definisi Bagian-bagian Virus

Selubung : selaput mengandung lemak mengelilingi beberapa partikel virus

Virion : partikel virus lengkap, bbrp jenis sifatnya sama dg nukleokapsid

virus cacat: partikel virus secara fungsional kekurangan bbrp aspek replikasi

Gambar Morfologi Virus

FIVE BASIC STRUCTURAL FORMS OF VIRUSES IN NATURE

• Naked icosahedral : e.g. poliovirus, adenovirus, hepatitis A virus

• Naked helical : e.g. tobacco mosaic virus. So far no human viruses with this structure are known• Enveloped icosahedral : e.g. herpes virus, yellow fever virus, rubella virus• Enveloped helical : e.g. rabies virus, influenza virus, parainfluenza virus, mumps virus, measles virus• Complex : e.g. poxvirus

Teori Evolusi Virus (2 hipotesis)

Virus berasal dari komponen sel hospes yang menjadi otonom

Komponen tersebut menyerupai gen yang telah mempunyai kemampuan hidup yang tidak tergantung pada hospes.

Virus berasal dari sel hidup yang bebas

Klasifikasi Virus Jenis asam nukleat ukuran dan morfologi kerentanan thd pengaruh fisik dan kimiawi adanya enzim khusus sifat-sifat imunologik metode penularan alami inang, jaringan & tropisme sel patologi, pembtk badan inklusi simptomatologi

KLASIFIKASI VIRUS

PENYAKIT SISTEMIK penyakit menyebar ke

seluruh tubuh mell. aliran darah & berpengaruh ke berbagai organ.

Contoh: Vaksinia,Campak, Rubella,Cacar air, demam kuning, dengue, enterovirus

PENYAKIT PRIMER Virus dpt mencapai

organ ttt melalui aliran drh, saraf perifer / jalur lain, predileksi di organ tertentu

Klasifikasi berdsrkan simptomatologi kelemahannya: virus yg sama sbbkan peny. berbeda ATAU peny. sama disbb virus beda

PENYAKIT PRIMER

Peny. Sal. Nafas : influenza, parainfluen, pneumonia viral, faringitis adenovirus

Peny. Mata: konjungtivitis, herpes

Peny. Kulit/mukosa: herp. simplek 1/oral & 2/genital, herp.zoster,

Peny. Ssn saraf: Poliomyelitis,meningitis, rabies.

Peny. Kelj. Ludah: gondong , CMV

Peny. Sal. Pencernaan: rotavirus,adenovirus enterik.

Peny. Hati: Hepatitis A, B,C, demam kuning, herpes, rubella

Peny. Lwt hub. Sexual: molusk.kontagiosum, HSV 2, AIDS,hepatitis.

Klasifikasi berdasarkan sifat Biologi, Kimia dan fisika

VIRUS DNA Parvovirus, Papovirus,

Adenovirus,Herpes virus, Pox virus, Hepadna virus

VIRUS RNA Picornavirus,

Kalisivirus, Reovirus, Arbovirus,Togavirus Flavivirus, Arenavirus, Rabdovirus,RetrovirusBunyavirus, Orthomiksovirus,paramiksovirus, Corona dan Delta virus

Macam-macam VIRUS

INTERNATIONAL CLASSIFICATION OFVIRUSESPrimary characteristics used in classification

Viruses are classified according to the nature of their genome and their structure

INTERNATIONAL CLASSIFICATION OFVIRUSES Secondary characteristics

Replication strategy Sometimes a group of viruses that seems to

be a single group by the above criteria is found to contain a subgroup of viruses which have a fundamentally different replication strategy - in this case the group will be divided based on the mode of replication

Komposisi Virus

PROTEIN Fx: transfer as.nukl ant

sel hospes, lindungi genom virus, plekatan dg sel hospes, struk. partk. virus, tentukan sifat antigenik virus

KARBOHIDRAT glikoprotein, sbg Ag

ptg, pd permk punya slbng u/ melekat virus

ASAM NUKLEAT 1 jenis as.nukleat

(DNA/RNA), informasi genetik, genom untai tunggal/ganda,lingkar/untaian,segmen/tdk

LEMAK Fosfolipid slbng virion,

virus mgd lemak peka eter, kemamp infeksi hilang

Rx Virus thd Agen Fisik & Kimia

PANAS & DINGIN stabilitas bervariasi,

virus ikosahedral > stabil, virus berslbng > peka thd panas, kemamp. inf hilang pd 50 - 60oC, 30 mnt, dpt diawetkan pd suhu dibwh titik beku (4oC), virus berslbng: hilang kemamp. inf setelah penyimpanan lama

GARAM pd garam 1 mol/L

stabil, tetap aktif walau dipanaskan 1 jam 50oC, vaksin polio disimpan dlm dingin .

pH dan RADIASI pH 5-9 stabil,

enterovirus thn asam, virus hancur pd basa, nonaktif pd UV/sinar X

Rx Virus thd Agen Fisik & Kimia

DETERJEN deterj. non ionik & Triton K100 melarutkan unsur

lemak pd slbng virus, SDS larutkan selubung & memecah kapsid

FORMALDEHID berx dg as. nukleat shg kemamp inf.hilang, genom

ganda > sulit dinonaktifkan formald. ANTIBIOTIKA & ANTIBAKTERI LAIN tdk berefek (alk.formalin,yod.), organik klor dosis >

tinggi dpt inaktifkan virus .

Agen Seperti Virus

VIROID Molk.tunggal,RNA sirk.

tanpa selubung, RNA kecil tdk mengkode protein, peny. Tanamn.

VIRUS CACAT As Nukleat & protein,

Replikasi butuh ‘virus helper’, cacat oleh karena mutasi/delesi materi genetik.

PSEUDOVIRION DNA sel hosp. mganti

DNA viral dlm kapsid slm inf virus.dpt infek. sel,tapi tdk replikasi.

PRION Protein ,tanpa as. Nukl,

ME: filamen-2 = virus/ bakteri , resist. UV, panas,formalin,nuklease, Inaktif pd otoklaf , hipoklorit & NaOH

PROSES PERTUMBUHAN VIRUS

Siklus Pertumbuhan dibagi 3 tahap: tahap awal: penempelan, penetrasi,

pelepasan selubung tahap tengah: ekspresi gena &

replikasi gena tahap akhir: pengemasan dan

pelepasan virion

PROSES INFEKSI VIRUS

Pengenalan Sel Target protein luar sebagai ‘reseptor binding

site’, yang berikatan dengan reseptor protein spesifik pada permukaan sel hospes

Penetration The virus enters the cell in a variety of ways according to

the nature of the virus.

Enveloped viruses (A) Entry by fusing with the plasma membrane. Some

enveloped viruses fuse directly with the plasma membrane. Thus, the internal components of the virion are immediately delivered to the cytoplasm of the cell (figure 1).

(B) Entry via endosomes at the cell surface (figure 2) Non-enveloped viruses

Non-enveloped viruses may cross the plasma membrane directly or may be taken

up into endosomes. They then cross (or destroy) the endosomal membrane.

Penetration

Fusion  of a virus with the plasma membrane after attachment to  a cell surface receptor  Figure A

Fusion of a virus with the membrane of an endosome Figure B

Penempel & Penetrasi Virion Parental

Setelah menempel, penetrasi membran plasma, melepas genom, replikasi

Replikasi Genom dan Ekspresi Gena

tahap 1: sintesis m RNA tahap 2: tergantung asam nukleat virus

v. DNA: replikasi di nukleus (Poxvirus)

v. RNA: replikasi . di sitoplasma (kec Influenza)

Pelepasan Virion

setelah matur, protein viral ditransport, budding, insersi membran plasma eksterna hospes

Release

Virus may be released due to cell lysis or if enveloped,may bud from the cell.

Budding viruses (figures 3 and 4) do not necessarily kill the cell.

Some budding viruses may be able to set up persistent infections.

Not all released viral particles are infectious. The ratio of non-infectious to infectious particles varies with the virus and the growth conditions.

Figure 3. Transmission electron micrograph of HIV-1, budding and free   CDC

Figure 4. HIV budding from human lymph tissue (TEM x133,335) © Dennis Kunkel Microscopy, Inc.  Used with permission

Transkripsi dan Replikasi Genom Virus

Tahap- tahap Replikasi Virus