Virus, Fungi and Parasites

What does obligate intracellular mean? Cant grow or replicate outside a host What are the four things that viruses are classified on? -Type of nucleic acid -Morphology -Presence/absence of an envelope -Host organism What is a naked virus? No outer membrane/envelope Can viruses move on their own? No How do viruses enter a cell? Endocytosis or fusion How do viruses synthesise their components? -Production of viral mRNA -mRNA directs synthesis for proteins What two ways do viruses release their contents? -Cytolysis -Budding How do nucleic acids release via cytolyInflux of water and then the lysis of cells sis? What is release by budding? Exocytosis What is a cytocidal infection? -An infection that results in cell death -Rapid onset but clears quickly What are the 6 types of viral vaccines? -Live (weakened) -Killed -Component vaccines -Vector vaccines -mRNA vaccines -DNA vaccines What are the two ways we can produce virus particles? -Cell cultures -Embryonated hen's eggs How does HIV release its proteins? Budding How does viral DNA get made from ssRNA? Reverse transcriptase What are the four classifications of protozoa? -Amoeba -Flagellates -Ciliates -Sporozoa How are amoeba classified? Move by pseudopodia 1/6 How are flagellates classified? Have flagella How are ciliates classified? Have cilia How are sporozoa classified? -Have an apical complex -Are all parasitic What is the most common and most severe causative agent of malaria? Plasmodium falciparum Why does malaria only affect female mosquitoes? They need blood for the production of their eggs Where do the sporozoites from mosquitos develop into merozoites? The liver What causes the release into the blood from the liver of merozoites? Liver cell rupture Asexual How do merozoites develop once infected into a RBC? What are the 3 stages in malaria symptoms? -Cold stage -Hot stage -Sweating stage What are the severe symptoms of malaria? -Shock -Severe anaemia due to haemolysis -Pulmonary oedema -Liver failure (leading to jaundice) -Swelling/rupturing of the spleen What is chemoprophylaxis? Use of drugs to prevent disease What type of bacteria is malaria caused by? Plasmodium What is the main treatment for areas with no drug-resistant P.falciparum? Chloroquine What is the treatment for areas with chloroquine-resistant P.falciparum? -Mefloquine (Lariam) (or doxycycline) 2/6 Why are protozoal infections hard to treat? -They are eukaryotic cells -Harder to develop antimicrobial medications that specifically target them What is a helminth? Parasitic worm Do helminths have circulatory tracts? No What part of a helminth's skin makes them hard to treat? -Thick cuticle -Difficult for our immune system to eradicate How do helminths attach to the GI tract of humans? -Scolex (hooks for attachment) -May also have suckers What are the three classes of helminths? -Nematodes (round worms) -Cestodes (tapeworms) -Trematodes (flukes) How is the large roundworm transmitted? Fecal-oral How is the threadworm transmitted? Fecal-oral How are hookworms transmitted? -Larvae penetrate skin -Larvae are usually found in soil How is the whipworm transmitted? Fecal-oral What is ascariasis? Roundworm infection Where do nematodes live in humans? -Subcutaneous tissue -Lymphatic vessels What is the name of the larvae that nematodes release? Microfilariae -Elephantiasis -Causes enlargement of parts of the body What is lymphatic filariasis? 3/6 What is onchocerciasis? -River blindness -Microfilariae (larvae) enter internal tissue of the eye What is loiasis? -Loa Loa worm -Travels through subcutaneous tissue -Causing inflammation in the skin and eye What are cestodes? -Tapeworms -Humans are usually the primary host (ingestion of cysts from undercooked meat/fish) What is the issue with trematodes? -Live for decades in tissues or blood vessels -Cause progressive damage to vital organs What do trematodes use as an intermediate host? Snail What is the second largest economically impacting parasitic disease in the world? Schistosomiasis What is Schistosomiasis causes by? -Schistosoma spp. -Main route of contamination is through infected water (due to eggs being secreted by urine/faeces) What are the main symptoms of schistosomiasis? -Rash -Immune system responses -Organ damage Eggs (or larvae in nematodes and cesWhat is the best way to diagnose schistodes) detected in faecal or urine samtosomes, nematodes and cestodes? ples How are tissue living nematodes detect- Tissue samples and microfilaria will be ed? present in the blood Nematode infection has been shown to How can helminths be used as therapeuprotect against allergic diseases (e.g. tics? asthma and dust mites) How do fungi reproduce? Spores 4/6 -Rigid Do fungi have rigid or flaccid cell walls? -Due to presence of many polysaccharides Are fungus eukaryotic or prokaryotic? Eukaryotic What are the 3 types of fungus? -Yeast -Moulds -Macroscopic filamentous fungi (mushrooms) What molecule is present in fungal cell membranes and not other eukaryotes? Ergosterol Describe the structure of a fungus cell wall. -Outer layer of mannan -Beta-glucan joined layers of mannan to chitin -Then on the inside is the cell membrane with embedded ergosterol How does yeast grow? -Budding -Binary fission How does mould grow? -Grow as masses of overlapping and interlinking hyphal filaments (mycelium) -Reproduce by formation of spores What are hypha? A single thread of fungal mycelium What does it mean if the fungus is dimor- Can switch between yeast and hyphal phic? (mould) forms What are mycelium? -A collective of hypha -Can be separate or non-separate What are mycoses? Fungal infections What are the 3 types of mycoses? -Superficial and cutaneous -Subcutaneous -Systemic/deep 5/6 -Pathogenic fungi that cause skin infecWhat is a dermatophyte with an exam- tions ple? -e.g. ringworm -Cause tinea infections What is the main target molecule of many antifungals? Ergosterol -Inhibition of synthesis of ergosterol What are the two main ways antifungals -Direct binding of ergosterol leading to use ergosterol to kill fungal infections? leaky cells Name some ways (other than ergosterol) that antifungals work? 6/6 -Targeting DNA/RNA -Targetting microtubules