Viruses & other Pathogens

Viruses & other Pathogens By Diana L. Duckworth Rustburg High School Campbell County

What are the characteristics of living things? • Cellular organization • Reproduction • Metabolism • Homeostasis • Heredity • Responsiveness • Growth & Development

Structure of Virus • Protein Capsule • Surrounds genetic material • DNA • RNA • No means of independent metabolism or growth • No means of independent reproduction • Dependent on host life form • Can evolve or change over time http://library.thinkquest.org/C0123260/basic%20knowledge/DNA.htm http://www.laportecounty.org/departments/animal_shelter/rabie_virus.html

Entry into Host Cell • Three ways • Plants – through tear in cell wall of cell • Bacteria – punches hole and injects DNA or RNA • bacteriophage • Animals – Endocytosis – cell engulfs bacteria http://www.britannica.com/EBchecked/topic-art/101396/698/Adsorption-to-and-entry-into-a-cell-of-an-enveloped http://bio-microscope.blogspot.com/2008/03/article-virus-structure-and-system.html

http://bioserv.fiu.edu/~biolab/labs/Genetics/phage_lab.htm Lytic Cycle Lysogenic Cycle

Two Types of Viruses • Cells have two types of genetic information – DNA and RNA • Viruses may contain either DNA or RNA • A DNA virus injects its DNA into the host cell, and the DNA can control the cell directly • Examples – HPV; Herpes; Epstein-Barr • A virus with RNA is called a retrovirus – retroviruses inject their RNA into a host cell and force the cell to make new viral DNA, which may then be integrated into the cell’s normal DNA • Examples – HIV, rhinovirus (common cold and flu)

Virus as Pathogen – disease causing agent Mumps http://www.southlakeland.gov.uk/Default.aspx?page=1466 Measles Chicken Pox http://www.ndsc.ie/hpsc/A-Z/VaccinePreventable/Measles/Factsheet/ http://www.vaccineinformation.org/photos/variaap005.jpg AIDS Rabies Cold Hanta Hepatitis Flu Polio SARS Hemorrhagic Fever Yellow Fever Small Pox http://www.indiana.edu/~pirt/bioterrorism/diseases-smallpox.html

Mode of Transmission • Insects – ticks, mosquitoes • Exchange of body fluids – sex, kissing, even oral sex, sometimes sweat • Airborne – coughing, sneezing puts viral particles out in aerosols • Direct contact – touching; many viruses such as flu and cold are long lived on surfaces

Host Cell Specificity • Many can only infect certain tissues or types of cells (must have proper receptors) • Hepatitis – liver cells • Many cancers – human papilloma virus – cells of the cervix (opening of uterus) • Influenza, Hanta virus – lung tissue • Tobacco Mosaic Virus – only plant cells http://www.cdc.gov/ncidod/diseases/hanta/hps/noframes/phys/printtechsection.htm

Combating Viral Pathogens • Vaccines – A substitute host such as fertilized chicken egg is infected • Eggs produce antibodies to combat virus • Virus is heat killed & antibodies are injected in a vaccination • Jenner – cowpox injected to combat small pox • Class of drugs called interferons work by hindering the uptake of viral particles in cells – commercial - Tamaflu

Uses for Viruses • Non – pathogenic viruses • Used in genetic engineering to transfer genetic material • Pathogenic viruses • Biological Warfare • Smallpox • Ebola and other hemorrhagic fevers http://incontiguousbrick.wordpress.com/2007/05/17/911-truth-virus/

Prions – mad cow disease - bse • Bovine spongiform encephalopathy • Incorrectly folded proteins • Cause normal proteins to fold in such a way as to be not functional http://biomed.brown.edu/Courses/BI108/2006-108websites/group09artificialblood/index.htm http://www.biophys.uni-duesseldorf.de/research/prions/index.html http://www.bioquest.org/bedrock/problem_spaces/prion/background.php

What are the characteristics of living things? • Cellular organization NO • Reproduction with help from host cells • Metabolism NO • Homeostasis NO • Heredity with help from host cells • Responsiveness limited • Growth & Development NO

Viruses & other Pathogens