Lecture 34 DNA Viruses PDF

LECTURE 3: DS DNA VIRUSES AND DISEASES Yap Wei Boon, Ph.D Email: [email protected]  Learning outcomes In the end of the lecture, students are able to - Identify members of dsDNA viruses. - Discuss diseases caused by the viruses.  Herpesviri...

LECTURE 3: DS DNA VIRUSES AND DISEASES Yap Wei Boon, Ph.D Email: [email protected]  Learning outcomes In the end of the lecture, students are able to - Identify members of dsDNA viruses. - Discuss diseases caused by the viruses.  Herpesviridae (human herpesviruses, HHV) Can infect - others Recover - Latent infected patient - No symptom - self limiting - STD - Oral Sex - very contagious Kayap - Chicken pox - shingles Loading… * 8 important herpes viruses  HHV signature characteristics Icosahedral capsid surrounded by tegument proteins and virus mRNA. Envelope with glycoproteins. Cellular binding protein for HHV: co-receptor heparan sulfate main receptor nectins Infection occurs by endocytosis. Replication takes place in the nucleus.  Latent herpes infections Viral genome is switched off; only a few RNA are synthesized (latency associated transcripts, LATs). No virus protein synthesis. Loading… LATs (Latency-associated Transcripts) inhibit apoptosis to ensure neuron survival. Exception: Latent CMV infection in memory B cells. The virus synthesizes proteins to maintain the viral genome copy number as the B cells divide.  Eg. Shingles Herpes simplex  Papillomaviridae, human papillomaviruses (HPV) High risk human papillomavirus types : 16, 18 and 31. Low risk HPV (6 and 11) : skin warts and internal epithelial cell infection (genital warts and infection in vocal chords and respiratory tract). Sexually transmitted and causes cervical neoplasia. HPV infection does not kill the cells. Viral genome may be integrated into host genome or maintained as episomes in transformed cells. High risk E6 and E7 can transform primary human keratinocytes.  Polyomaviridae, eg. SV 40 Simian virus (SV) 40. First introduced into humans during mass vaccination campaign for Sabin polio vaccine (live vaccine). The vaccine was contaminated by SV 40 due to polio virus propagation in African green monkey kidney cell (Vero). Adheres to MHC class 1. Associated with neural tumors and mesothelioma (together with asbestos) in humans.  Poxviridae Brick-shaped and enveloped. Biconcave capsid. Cytoplasmic replication (carry own enzymes for mRNA synthesis). Loading…  Orthopoxvirus: vaccinia (live vaccine for smallpox disease), variola (etiological agent for smallpox disease*), monkeypox (Mpox)**. *eradicated globally from human populations. **Clade IIb causes an outbreak in 2022-2023, rarely fatal (99% of infected people will recover). The smallpox vaccine is used to prevent Mpox as the vaccine can confer Both are different from varicella-zoster infections (chickenpox and shingle), so varicella-zoster vaccines cannot protect high-risk individuals from smallpox and Mpox. Avipoxvirus: fowlpox. Capripoxvirus: sheeppox. Leporopoxvirus: myxoma of rabbit, spread by arthropods. famous v ins. Molluscipoxvirus: molluscum contagiosum in humans (direct contact or sexually transmitted), skin wart. among sex worker ~ farmer milk animals Parapoxvirus: orf virus or milker’s node virus (picit tetel (embu) infectSuipoxvirus: swinepox virus. Couinfect similar to ~ Monkeypox pig farmers)Yatapoxvirus: yabapox and tanapox of monkeys (Enzootic in African monkeys, spreading to humans through contact with infected monkeys, causing similar lesions in humans as in affected monkeys. Can be transmitted via insect bites from an unknown wild animal reservoir, probably a species of nonhuman primate.) human infected transmitamong monkeys until in contact with animal to G used but infectious ↳ not deadly economical 2) affect activity (farming Note: many poxviruses are potential zoonotic infectious agents. y ( pustule I filled with fluid/pus) from intectinone (2 weeks); 3 weeks to finallyactually recover recoveryperiod :5days  The virus can spread to humans from an animal host (rodents or nonhuman primates such as monkeys). The virus also can spread between people through close contact. In humans, Mpox can cause flu-like symptoms and an itchy, painful rash. Swollen lymph nodes. Fever and chills. Headache. Backache. Feeling very tired, called fatigue. Muscle aches and backaches. Then the blisters fill with pus, scab over and fall off over a period of 2 to 4 weeks. spread Central Clade 1 tends to spread regularly in Central Africa. at Africa It tends to cause more serious illness with mpox and is linked to more deaths from Mpox. It may spread more easily than clade 2. Clade 2 tends to spread regularly in West Africa. blister-like pustules Clade II causes less severe disease and is less likely to cause death than clade I. No specific antiviral drugs but can be treated with cidofovir (initial used to treat CMV retinitis) or low grade fever tecovirimat (initially used to treat cowpox and smallpox). 100 % effective not for monkey pox proven yet medication form poxis not torecoverpoxm (. n clinically  LECTURE 4: singleSSDNA VIRUSES Stranded AND DISEASES DNA Yap Wei Boon, Ph.D Email: [email protected]  Learning outcomes In the end of the lecture, students are able to: - Identify members of ssDNA viruses especially parvoviruses. - Discuss diseases caused by ssDNA viruses.  Parvoviridae X envelope ~ use to -carry small/tiny capside attach to receptor Parvoviruses: amongst the smallest viruses (18-26 nm in diameter), naked. Two subfamilies: Parvovirinae (vertebrate viruses) and Densovirinae (invertebrate viruses). Carry either a (+) or (-) strand DNA. target RBC -only Attach to blood group P antigen on RBC, endocytosed into RBC, and transported to the nucleus by microtubules. Depends on host proteins for virus replication.  Autonomous parvoviruses: parvovirus B19 (isolated from a healthy blood donor). Infect red blood cell precursors. asymptomatic, however, may cause the fifth disease (erythema infectiosum with “slapped cheek” appearance). may also cause: Crashes/redness i. acute arthritis. on the cheek ii. aplastic anemia in chronic hemolytic anemia patients. iii. Hydrops foetalis (transmitted from a pregnant woman to the fetus and may kill the fetus). In 2005, a new parvovirus was isolated from the nasopharyngeal aspirates of children with lower respiratory tract infection. -attach to RBC because precursor replicate rapidly they - autoimmune, anemia , blood disorder Limmunocompromised) - pregnant lady (mother experience lead to arthritis disease mild symptom); fetug's RBC divide virus to Coint pain) rapidly > transmit - J fetur > lead to abortion -