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Unformatted text preview: NOV 11 th . Baculovirus • Double stranded circular DNA • Infected unit is called the virion- composed of nucleic acid surrounded by protein coat called the capsid around the capsid is an evelope which completes the virion infective unit. • There are usually greater than 100 virions per PIB (Polyhedral inclusion body) • Granulovirus- inclusion body is called granule usually just one virion per granule • Both of these viruses can multiply in the nucleus of the insect • Hymenoptera- bee, wasps the viruses multiply only in the nuclei and in the midgut epithelium • Baculovirus are extremely virulent and will kill 450species of insect daily. • Cousin of the NPV are the cytoplasmic polyhedrosis virus CPV-cypovirus o Cypovirus- the genome consists of various sized fragments that look like donuts, 10 segments. o CPV cause chronic infection o Causes the insect to be sluggish, slow growing, vomit, diarrhea, if makes it to adult stage fecundity will be very low, few eggs hatch, fewer live. Baculovirus infection mechanism mainly looking at NPV • Main infection starts per os. • Enters the midgut, exposed to alkaline environment, starts to break up • cracks start to form in the crystal, these cracks allow the proteases in the insect gut to get at more of the protein. Almost 99% of all viruses are lost, only need 1 virus to infect insect. Virion passes through the periotrophic membrane where it encounters the midgut epithelial cells. Beginning what is called the primary infection. • The columnar cells are the dominant cells that are infected by NPV. • Virion will almost always make contact with the microvillus. When this happens the envelope and the cell membrane dissolve releasing the nucleocapsin into the cell, new capsid is formed. • The new capsids go into the cytoplasm and then the cell membrane. Nucleocapsid makes contact with cell membrane and gets budded out for the cell, you have a virus. Begins secondary infection stage. • The budded viruses can go anywhere in the cell. When the budded virus makes contact with the cell membrane of the fat body cell, it will cause the cell to phagocytose the virus. End up with the budded virus in a phagosome that will fuse with the lysosome, forming a phagolysosomal vesicle. • The lysosome has very acidic pH, the acidic pH is necessary to activate the peplomeres of gp64. The peplomeres contact the membrane of the hybrid, causes both membranes to dissolve upon contact. Releasing the nucleocapsins into the cytoplasm. • Work their way to the nuclear pore of the nucleus and it is injected in. • DNA unwinds forming chromatin. Have viroplasms in which DNA is replicated, capsids forming about the DNA, viralplasma is then referred to as the virogenicstroma....
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