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ADENOVIRUS - Adenoviridae 2 genera o Aviadenovirus (avian) o Mastadenovirus Frequent cause of URT infections (colds) o 5-10% URT in children First isolated in human adenoids Widespread in nature Can undergo latent infection in lymphoid tissue, becoming reactivated sometime later Medium-sized (60-90nm) Non-enveloped, icosahedral Non-segmented, linear, dsDNA (26-45 Kbp) - - - - o Carries 22-40 genes Largest non-enveloped virus o They are the maximum size able to be transported through the endosome Endosome o Membrane bound compartment inside eukaryotic cells o Compartment of the endocytic membrane transport pathway from the plasma membrane to the lysosome Oncogenic potential Can be vectors to carry and express foreign genes for therapeutic purposes o Easily manipulated in vitro RETROVIRUS - - - - Most infects vertebrae Enveloped, RNA Replicated via a DNA intermediate Stores its nucleic acid in the form of a (+) mRNA genome o Serves as means of delivery of that genome into cells it targets as an obligate parasite Relies on the enzyme reverse transcriptase to perform the reverse transcription of its genome from RNA to DNA o Can be integrated into the host’s genome with an integrase enzyme Once in the host’s cell, the RNA strands undergo reverse transcription in the cytosol and are integrated into the host’s genome, at which point the retroviral DNA is referred to as a provirus Difficult to detect the virus until it has infected the host Retrovirus enters a host cell – provokes RNA strands inside of the normally-functioning cell – reverse transcription (violates central dogma) o DNA – RNA – Protein - Retrovirus inside of a cell = first two steps of the process will be switched o RNA – DNA o Host cell becomes provirus When retroviruses have integrated their genome into the germ line – their genome is passed on to a following generation Endogenous retroviruses o Makes up a large portion of the human genome o Most insertions have no known function and is often referred to as “junk DNA” o Play important roles in host biology Gene transcription Cell fusion during placental development in the course of the germination of an embryo Resistance to exogenous retroviral infection - HERPESVIRUS - Greek: Herpein: to creep = chronic, latent, recurrent infections Composed of relatively large dsDNA, linear Encodes 100-200 genes encased within an icosahedral protein cage ~100 herpesviruses have been isolated 8 known human herpesviruses HSV ½ o Infects humans Ubiquitous and contagious Symptoms o Watery blisters in the skin or mucus membranes of the mouth, lips, genitals - - - Heals with a scab characteristic of herpetic disease As neurotropic and neuroinvasive viruses o HSV 1 and 2 – persists in the body for the life of the carrier by becoming latent and hiding from the immune system in the cell bodies of nerves After initial infection, some experience sporadic episodes of viral reactivation or outbreaks o In an outbreak, the virus in a nerve cell becomes active and is transported via the nerve’s axon to the skin, where virus replication and shedding occurs and causes new sores No known cure for HSV infection o Treatments can reduce likelihood of viral shedding BACTERIOPHAGE - Viruses that infects bacteria Among the most common biological entities on earth Some named as a member of a T series Sea water o One of the densest natural sources for phages and other viruses - o Up to 9x108 virions/ml in microbial mats at the surface o Up to 70% of marine bacteria may be infected by phages Used over 60 years as an alternative to antibiotics in the former Soviet Union and Eastern Europe Seen as possible therapy against multi-drug resistant strains of many bacteria HIV/AIDS First reported in the US (1981) 33 million worldwide are infected Infection cycle o Virus hones in on CD4 T cells, infecting and killing them Without T cells, body cannot defend against invading bacteria or viruses Each HIV particle possesses glycoprotein (gp120) on its surface Precisely fits a cell-surface marker protein (CD4) on surfaces and T cells o After docking onto the macrophage CD4 receptor, HIV requires a second macrophage receptor (CCR5) to cross the cell membrane Once inside the macrophage, the HIV particle sheds its protective coat - RNA and reverse transcriptase left floating in the cytoplasm Double strand of DNA, complementary to RNA produced Viruses released via exocytosis Future of HIV treatment o Combination drug treatment AZT and protease inhibitors Keeps disease in check o Vaccine therapy May reduce reproductive capability of HIV o Blocking replication Chemokines bind to and block receptors CAF: prevents viral replication o Disabling receptors DISEASE VIRUSES INFLUENZA - Animal retroviruses distinguished by their capsid Types A, B, C Subtypes differ in protein spikes VIRUS AND CANCER - Association between Hep B and liver cancer HPV and cervical cancer 15% of all cancers worldwide RECOMBINATION PRIONS - - - Viral genes are readily re-assorted by genetic recombination Novel combinations of H and N spikes unrecognizable by human antibodies Inability to make perfect vaccines Flu pandemics EMERGING VIRUSES - - Ebola: 90% lethality SARS o 2003 o From civets in china eaten as delicacies COVID o UK variant B.1.1.7,20I/501Y.V1 More transmissible 70% more contagious Proteinaceous infectious particle Nobel prize 1997 Responsible for transmissible spongiform encephalopathies Scrapie: sheep Mad cow disease: cattle Humans o Kuru: fore people in new guinea o CJD VIROIDS - Tiny, naked molecules of RNA Important infectious disease agent in plants o Recent outbreak killed 10 M coconut palms in PH Resembles sequences of introns within ribosomal RNA genes o Capable of catalyzing destruction of chromosome integrity