Viral Functions for RNA Viruses Reverse Transciptase Reverse Transcriptase o

Viral functions for rna viruses reverse transciptase

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Viral Functions for RNA Viruses: Reverse Transciptase Reverse Transcriptase o Makes a permanent, stable copy of DNA from a transient, unstable RNA o The virus doesn’t do any good until the viral integrase protein integrates the DNA into the genome—after this is when the virus can take effect ° HIV: Gene Expression—Assembly and Lysis Virus can remain latent inside host cells, as long as the cell is alive, they have an internal reservoir of HIV (called provirus ) At certain stages, the virus decides to replicate and can use the host enzymes to make the plus RNA strands o Viral DNA transcribed to make RNA that is translated to produce viral proteins (proteins are assembled by viral proteases) Makes polyproteins which are chopped by viral proteases Viral proteins and viral RNA are assembled Budding occurs to general viral particle (also lysis of the helper T-cells) Tends to replicate in macrophages, etc. without causing damage o But tends to cause lysis in Helper T-cells from budding ° HIV: Reservoirs and Transmission Reservoir: humans o Primarily emerged around 1900 from SIV 59
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Transmission: o Sexual contact Blood, semen, vaginal secretions o Contaminated blood/blood products o Infants via fetal transmission/during birth Virus is easily inactivated and must be transmitted by close contact in body fluids o Membrane is very delicate and it is not casually transmitted Not transmitted by casual contact—toughing, kissing, coughing, sneezing, insect bites, water, food fomites, etc. ° HIV Pathogenesis Causes disease by disrupting the immune system Mucosal cells are infected o Initially infects macrophages and dendritic cells o These cells then travel to the lymph nodes where they encounter and infect CD-4 helper T-cells (major place of replication) Nonspecific symptoms—flu like or with a rash Asymptomatic period follow o Some viral replication, but immune system regenerates Finally (5-15 yrs later) immune system is affected o The CD4 T-cell count drops and the body can no longer replace them o Opportunistic infections increase bc of the bad immune system—this is the major problem Acquired Immunodeficiency Syndrome (AIDS) Occurs when one has tested pos for HIV AND either: o CD4 T0cell counts are under 200 per microliter OR o CD4 T-cell account for fewer than 14% of all lymphocytes OR o One or more of a CDC-provided list of AIDS-defining illnesses ° Complications of AIDS Opportunistic infections o Fungal and parasitic infections ( Candida albicans, Pneumocystis, jirovecill, Toxoplazma, etc.) From bacteria, fungi, protists, viruses o Severe viral infections o Bacterial diseases (mycobacteria, enteric infections) Malignancies (Cancer) o Kaposi sarcoma, etc.
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  • Spring '19
  • cells, immune cells, Adaptive immune response

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