The main properties of Flaviviruses Taxonomic Classification Important Arbovirus and Virus Properties Rodent-Borne Virus Embers Genus flavivirus Brazilian encephalitis Spherical, 40-60 nm in (Rocio virus ), dengue diameter. Genome: Japanese B encephalitis, positive-sense, single- Kyasanur Forest disease stranded RNA, 11 kb in size louping ill, Murray Valley Genome RNA infectious encephalitis, Omsk Envelope. Three structural hemorrhagic fever, Russian polypeptides, two spring-summer glycosylated Replication: encephalitis, St Louis cytoplasm. Assembly: encephalitis, tick-borne within endoplasmic encephalitis, West Nile reticulum. All viruses fever, and yellow fever serologically related viruses. Arthropod-borne (mosquitoes, ticks
The main properties of Flaviviruses
Transmission Replication The virus infects the arthropod vectors(e.g, mosquitoes), replicating in the arthropod's gut The virus then spreads to other organs and particularly the salivary glands Once the virus is the salivary glands, the infected arthropod vector is able to transmit the virus to a vertebrate host The most successful hosts are monkeys, bats birds and some domestic animals Humans are usually dead-end hosts because the virus is unable to replicate to create a high enough titer to re-infect the vector
Transmission & Replication The virus infects the arthropod vectors (e.g., mosquitoes), replicating in the arthropod's gut. The virus then spreads to other organs and particularly the salivary glands. Once the virus is the salivary glands, the infected arthropod vector is able to transmit the virus to a vertebrate host. The most successful hosts are monkeys, bats, birds and some domestic animals. Humans are usually dead-end hosts because the virus is unable to replicate to create a high enough titer to re-infect the vector
The flavivirus lifecycle >Binds to cells via viral Virus attachment Virus neutralization E proteins 8人、免 and enhancement >Enters cells via (ADE) endocytosis Clathrin-mediated pr >Fuses with endosomal Virus membranes under low A)Endosome pH; >Releases viral genome pH-dependent into the cytoplasm; fusion in the endosome H5.7 >Replicates in cytoplasm uNcoating Virus >Assembles in maturation cytoplasmic reticulum (ER pH6.0 H6.7 Buds into Golgi H7.2 Golgi >Release mature virions out of cell amiculum(ER)
The flavivirus lifecycle Binds to cells via viral E proteins; Enters cells via endocytosis; Fuses with endosomal membranes under low pH; Releases viral genome into the cytoplasm; Replicates in cytoplasm; Assembles in cytolasmic reticulum (ER); Buds into Golgi; Release mature virions out of cell
Generalized transmission cycle of tick-borne flaviviruses Small mammals >virus is passed to succeeding tick stages during moulting uremIc (transstadial transmission), as well Cofeeding tick as transovarially to progeny of Unfed larvae Fed larvae Transstadial adult ticks transmission >Both male and female ticks are E Unfed nymph involved in transmission Cofeeding tick >Tick-borne encephalitis virus Fed adult Small mammals may be transmitted to uninfected 哪兽 ticks cofeeding on a vertebrate Unfed adult Fed nymph host without the requirement for Tick bite active viremic infection of the host 0 Oral infection
Generalized transmission cycle of tick-borne flaviviruses Virus is passed to succeeding tick stages during moulting (transstadial transmission), as well as transovarially to progeny of adult ticks. Both male and female ticks are involved in transmission. Tick-borne encephalitis virus may be transmitted to uninfected ticks cofeeding on a vertebrate host without the requirement for active viremic infection of the host
Flavivirus Encephalitis >Inflammation of the brain due to flavivirus infection Humans shows an age-dependent susceptibility: Infants and the elderly being most susceptible >clinical findings: incubation period: 4-21 days Symptoms a. A sudden onset of headache, chills, fever(lasting 4-10 days), vomiting, generalized pain; b. 24-48 hours later, develops marked drowsiness, mental confusion tremors or coma in severe cases Sequelae is mild to severe, including mental deterioration, personality changes
Flavivirus Encephalitis Inflammation of the BRAIN due to flavivirus infection. Humans shows an age-dependent susceptibility: Infants and the elderly being most susceptible. Clinical findings: incubation period: 4-21 days Symptoms: a. A sudden onset of headache, chills, fever (lasting 4-10 days), vomiting, generalized pain; b. 24-48 hours later, develops marked drowsiness, mental confusion, tremors or coma in severe cases. Sequelae is mild to severe, including mental deterioration, personality changes