Introduction To Virology Course PDF

Dr. Fatima Salah Mohammed M.B.B.S (U of K) MD of clinical pathology and virology (U of K) Course is divided into basic virology and systemic virology: Basic virology:  Basic characteristics of viruses  Viral Structure and replication  classification of viruses (viral families)  Viral pathogenesi...

Dr. Fatima Salah Mohammed M.B.B.S (U of K) MD of clinical pathology and virology (U of K) Course is divided into basic virology and systemic virology: Basic virology:  Basic characteristics of viruses  Viral Structure and replication  classification of viruses (viral families)  Viral pathogenesis and host defense  Anti viral drugs and vaccines  Laboratory diagnosis ……  Systemic virology :  Clinically important viruses like influenza virus, HIV,hepatitis viruses ……  We must learn about each virus the following:  Classification, morphology,epedimology, clinical importance,diagnosis ,prevention and management,    Prof. Isam El khidir lectures notes Reviewed articles Text books eg.: Review of clinical Medical Microbiology and immunology Basic characteristic and structure of viruses      Are they cells? How they first discovered? How can be seen? How they look like ? How they replicate? property viruses Cells Type of genetic material DNA or RNA DNA and RNA (nucleus) Mitochondria Absent present Ribosomes Absent present Multiplication by binary fission or mitosis No Yes Lipoprotein membrane Envelope protein in some viruses Cell membrane present in all cells Using electron microscope The basic structure of viruses is composed of: 1-Viral genome either DNA or RNA is the main component Can be linear or circular Single or double stranded Segmented or not segmented  2. Capsid protein : protein coat coded by viral genome give the characteristic structure, each capsid composed of identical subunits called capsomers, which composed of one or several proteins Viral genome capsid nulcleocapsid The nucleocapsid has two forms of symmetry: Icosahedral Helical particle *note Functional virus can be assembled in test tube, in absence of cell ad not need energy Viruses can be classified into : enveloped or non enveloped(naked) viruses  The envelope is a lipoprotein ,the lipid part is derived from host cell membrane by budding  Except herpes viruses derived their envelop from host nuclear membrane  Non –enveloped viruses are more resistant to external environment and disinfectants than enveloped one. (fecal oral route)    While enveloped viruses are transmitted directly by body fluid (respiratory droplets, blood) Envelope proteins and capsid protein elicit host immunity , act as antigens and used to classify the single vies type into different serotypes(antigenic variants)      enveloped viruses , in addition to capsid protein ,their envelop contain proteins with many functions Envelop proteins forming projection like structures (called spikes)mediate the attachment to specific receptors on host cell surface(e.g. SARS_covid_2 Spike protein bind to ACE_2 receptors) Envelop proteins act as antigens that induce host immunity These proteins used as targets for neutralizing antibodies(newborns to mothers with positive HBV) based on the varieties of these surface antigens the virus subcategorized into serotypes   Some proteins present between the envelope and the capsid e.g. matrix protein, nonstructural proteins and regulatory proteins Go and read about Atypical virus _like agents      Observing the virus growth curve we notice the following important points: In the first hours the virus disappears (eclipse period) Then start to accumulate inside the infected cells( detected invitro by cytopathic effect) Lastly hundred virus particles are released and cause cell lysis and death. Some viruses have latent period (herpesviruses) Stages of viral replications: 1. Attachment 2. Penetration 3. Uncoating 4. Early transcription 5. DNA synthesis 6. Assemly 7. Release      Is an alternative pathway for viral replication As the viral DNA becomes integrated into the host cell chromosome and no progeny virus particles are produced at that time, but the viral nucleic acid continues to function in the integrated state in a variety of ways Best examples for lysogeny is synthesis of several exotoxins in bacteria, such as diphtheria, botulinum, cholera, and erythrogenic toxins, encoded by the genes of the integrated bacteriophage (prophage)      Depending on: virus particle structure Viral genome viral replication and Newly introduced --gene sequencing DNA viruses :  Hepadnavirus --------HBV  Herpesvirus ----------HSV,CMV VZV,EBV,  Poxvirus -------------small Pox virus and molluscum contagious  Adenovirus ------------Adenovirus  Papillomavirus --------HPV  Polyomavirus ----------BK,JC  Parvovirus------------- Parvovirus B19 RNA viruses  1Picornavirus--------------Polio virus, HAV, Enteroviruses, rhinoviruses  Coronavirus ------------ coronavirus  Hepevirus----------HEV  Flavivirus---------Yellow fever virus  Retrovirus-------HIV,HLTV  Togavirus---------Rubella  Arenavirus-------LCV,Lassa fever virus  Bunyavirus--------Hanta virus  Filovirus-------Ebola virus  Orthomyxovirus -------Influenza virus  Paramyxovirus---------Measles, Mumps,RSV  Rhabdovirus-----------Rabies  Reovirus----------rotaviruses