Virology: Structure, Classification, and Viral Multiplication - PDF

Okay, I will convert the images into a structured markdown format as requested. ### Structure and Classification of Viruses #### Definition * A single type of nucleic acid (DNA or RNA) which constitutes the viral genome. * Reproduction by replication of the genome (there is no growth or fissi...

Okay, I will convert the images into a structured markdown format as requested. ### Structure and Classification of Viruses #### Definition * A single type of nucleic acid (DNA or RNA) which constitutes the viral genome. * Reproduction by replication of the genome (there is no growth or fission). * An obligate intracellular parasite. Lacking enzymes for energy metabolism and lacking machinery for translation. #### Differences Between Viruses and Bacteria | | B | V | | :--- | :-------------------------------- | :-------------------------------- | | Size | Taille (M. optique) | Taille (M. éléctronique) | | | ADN et ARN | ADN or ARN | | | Enzymes for biosynthesis | | | | Croissance | | #### Structure of Viruses * **Obligatory elements:** Genome, Capsid (protein shell). * **Inconstant elements:** Envelope + internal proteins. * **Capsid:** protein in nature * **Genome:** DNA or RNA * **Virus Envelope:** internal proteins, nucleic acid, nucleoid, capsid, nucleocapsid * **Intermediate Structure:** Tegument; Interposed between the nucleocapsid and the envelope (in certain families). #### Virus Genome * Virus with DNA * **Monoatemic** * Linear: Daenoviridae BIS * Linear: Adenoviridae, Herpesviridae * **Bicatemic** * Partly Bicatemic: Hepadnaviridae(Hepatitis B) * Circular: Polyomaviridae * **Monocatemary** * Linear: Segmented; single stranded DNA. * Diploid * Virus with RNA * **Monocatemary** * Segmented; segment d'ARN * **Bicatemic** * Segmented: Reoviridae #### The Capsid * Assembly/polymerization of one or a small number of protein subunits. * **Capsid tubular with helicoidal symmetry** *Consists of units of morphological subunits: elongated sticks, rigid and hollow * Example: Influenza virus (Orthomyxoviridae), Rabies virus (Rhabdoviridae). * **Capsid icosahedral with cubic symmetry** * Capsomers assemble to form the capsid. *Includes: Rotavirus, Picornavirus Papillomavirus, Adenovirus * **Complex symmetry capsid (mixed)** * Shape of a biconcave lens. * Example: Poxvirus. #### Classification of Viruses * According to the Lwoff, Horne, and Tournier (LHT) system based on three criteria: * **Nature of Nucleic Acid:** (DNA/RNA); helicoidal, cubic. * **Symmetry of Nucleocapsid** * **Presence/Absence of Envelope.** #### Nomenclature * Family: Viridae * Subfamily: Virinae * Genus: Virus * Species: Individual Virus (e.g., Epstein-Barr Virus (EBV)) #### Viral Multiplication * Viruses are obligate intracellular parasites. * Viral RNA enters into competition with cellular RNA. * Viruses transport their genome, and some enzymes, but the host cell provides the energy and molecular precursors. * Viral multiplication cycle is complete only if it is a productive cycle. Note: Not always highly productive. * Viral life cycle is cyclical, involving intra- and extracellular stages * Cycle duration depends on size and complexity. #### Stages of the Multiplication Cycle * **Early Stages:** Initial steps * Attachment to the cell surface (electrostatic interaction) * Penetration (direct translocation, endocytosis, membrane fusion) * Uncoating * **Expression and replication of the viral genome** * **Late Stages:** Following replication * Maturation: Proteolysis and glycosylation. * Assembly: Nucleus (DNA viruses), Cytoplasm (RNA viruses). * Release: Lysis or budding. #### Virus-Cell Interaction * Infection leading to productive cycle: non-lytic. * Abortive cycle: cell non-permissive. * Cell sensitive. * Lytic Cycle * Cycle and Inductibility #### Cell Transformation * **Cancerous Cells:** Viral genome is not integrated into the host cell. * It resides within the cell in circular form (episome): stress immunity cycle. *Genome archiving and production *Infection *Productive cycle #### Vaccines * Antigenic preparations derived from a specific pathogen, capable of inducing an immune reaction. * Immunoprophylaxis: active. Protection begins slowly and duration. #### Two Types of Vaccines * **Live attenuated:** inactivated and complete. * **Inactivated:** (heat, formalin, beta-propiolactone) *Indicate multiple boosters. #### Method to obtain attenuated virus. * Cell passage in series: Ligne cellulaure 2, liniée cellulaire l * Thermosensitivity: Virus saveges, 34℃, 33℃, Virus atténues * Genome reassortment: Virus sauvage, virus savege * Non pathogenic virus used to vaccinate against a virus of the same family *Example: Virus de la vaccine immunise contre le virus de la variole #### Immune Response to Vaccines * **Cellular and Humoral:** Phagocytes / macrophages (CPA) * Present to cells with immune competence * **LT:** (immunity with humoral mediation) * **LB:** Plamocyte → IgA #### Secondary and Primary 1. contact with Ag, differential and slow response 2. * Anamnestic. *Rapid, durable and important response. #### Factors * influenced by: * Age. * Genetic Factors #### New Vaccines Approach * Vaccines are based on * Synthetic Peptides. * Viral Ags. * Recombinant Viruses. * Transgenic Plants. * **Side Effects:** see poly. #### General Mechanisms of Viral Infections * The environment plays an important role in climatic conditions * **Winter:** Transmission of respiratory infections. * **Summer:** Transmission of enteroviruses and infections to HIV. #### Pathogenesis of Viral Infection * Pathways of virus penetration * Respiratory tract *Localized and general infections are presented with alterations to respiratory endothelium *Diffusion by lymphatic route *Transmission by inhalation. *Transmission by contaminated air. * Digestive tract *Isolated localized resistant viruses. *Transmission by ingested foods that are contaminated * Skin *Rabies and Ebola * Reservoir of viruses and transmission conditions * Fragile Virus enveloped: via direct contract and touch * Resistant Virus : rivers, pools, alteration of the epithelium #### Viral Dissemination in the Organism * Conjonctiva: * Instrument ophthalmic, swimming pool. * Genital tract: * Infected location(HPV) * During sex (HIV). * Mother / infant * Transplacental * Moment of delivery. * Penetration * Local Multiplication. * Lymphatic diffusion * Viremia (short period). * Target organ / tissue. * Rarely occurs in the bone. #### Incubation Period: time between exposure and initial signs * Short (1-5j) * Infections localized * Exception * Long(10-20j) * Infections generalized : * Verues: infection localized. * Arboviroses: infection generalized and short. * Attachment of target tissues #### SNC * **SNC:** the spread is hematogenous * * **Lesions:** -meningitis * **Brain: -** Cerebellum. ME #### * The rabies virus (of rage) disseminates along the nerve files #### Le foie * Le foie - targets hepatotropic virus (of hepatitis) * Liver : - targets hepatotropic viruses *Ciel de la fore janne et carton porvialarides #### -T.hématopoiétique *The virus (GB) EBV LBH LV (L.Lmacophaques) #### Divers * -Gol salivates ( oreillons, rage, HSV, CM) * Muscles strides(griffe) *Gods mancuries (ereillons nage) *Cuar( virus con achic B) #### Excretion * The excretion occurs by: * Respiratory tract. * Skin. * Intestinal tract. * Urine. * Sperm. * Milk ### Diagnosis Techniques in Virology #### Virology Diagnostic Techniques * **Detection:** Detection of viral infection. * **Quantification:** Quantify the viral infection. * **Identification:** Identify the viral infection. *The choice depends on the goal #### Direct Diagnostic * **Indications:** Confirmation of diagnosis and identification of epidemics. * **Measure:** Measure the severity of the parameters * Follow-up HE #### Pratical Precaution *Is important understand *It is important to understand of each virus *It is important to understand * **Type and timing of collection** * **Site and time** - a collection of good time is critical * **Rich collection/ chronology** #### Technical specifications * **General rule** *Conservation in the correct time / medium in transfer. #### Methods of Direct Diagnosis * **Cell culture:** * Reference * Information joined to the collection (see poly) * **Realization of la culture** * Inoculation, on the cellular Prelevement * Nutritious Medium * Condition(37℃, 95%humiditiy, 5%CO²) * Duration / Imeis * **Lecture** * **Look at visible elements in the culture** * * l’état * Others are realized *Seroneutralization *Inhibition de the hemaggutination *Techniques immunogiques I aim to provide great detail in these transcriptions. If you need any additional help, let me know!