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Herpesviridae

Herpesviridae

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Herpesviridae

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  1. Herpesviridae Herpes zoster, herpes simplex, Epstein-Barr virus

  2. Herpesviridae • The Herpesviridae are a large family of DNA viruses that cause diseases in humans and animals. • Herpesviridae can cause latent or lytic infections. • There are eight distinct viruses in this family known to cause disease in humans.

  3. Human Herpesvirus (HHV) classification

  4. Replication of DNA viruses • In DNA viruses, such as Herpes, the viral DNA is released into the nucleus of the host cell where it is transcribed into early mRNA for transport into the cytoplasm where it is translated into early viral proteins. • The early viral proteins are concerned with replication of the viral DNA, so they are transported back into the nucleus where they become involved in the synthesis of  multiple copies of viral DNA. • These copies of the viral genome are then templates for transcription into late mRNAs which are also transported back into the cytoplasm for translation into late viral proteins. • The late proteins are structural proteins (e.g. coat, envelope proteins) or core proteins (certain enzymes) which are then transported back into the nucleus for the next stage of the replication cycle.

  5. אבעבועות רוח ושלבקת חוגרתChickenpox (Varicella) & Shingles (Herpes Zoster) תעודת זהות • משפחת הרפסוירוס (Herpesvirus) • פוליהדרלי • קופסית חלבונית • מעטפת • דנ"א דו-גדילי

  6. Shingles • Shingles appear as a painful rash. • It consists of red patches of skin with small blisters (vesicles) that look very similar to early chickenpox. • Shingles usually clears in 2 to 3 weeks and rarely recurs.

  7. Facts About Shingles (Herpes Zoster) • Shingles is a disease caused by the varicella-zoster virus, the same virus that causes chickenpox. • After an attack of chickenpox, the virus lies dormant in the nerve tissue. As we get older, it is possible for the virus to reappear in the form of shingles. Shingles is estimated to affect 2 in every 10 people in their lifetime. • This year, more than 500,000 people will develop shingles. Fortunately, scientists are doing research to find a vaccine to prevent the disease.

  8. WHAT ARE THE SYMPTOMS OF SHINGLES? • Early signs of shingles include burning or shooting pain and tingling or itching generally located on one side of the body or face. The pain can be severe. Rash or blisters are present anywhere from 1 to 14 days. • IS THERE A CURE OR TREATMENT FOR SHINGLES? • There is no cure for shingles, but the severity and duration of an attack of shingles can be significantly reduced if you are treated immediately with antiviral drugs, which include acyclovir, valacyclovir, or famcyclovir.

  9. Herpes Simplex Viruses (Genus Simplexvirus) תעודת זהות • משפחת הרפסוירוס (Herpesvirus) • פוליהדרל וירוס • קופסית חלבונית • מעטפת • חודים (spikes) • דנ”א דו-גדילי

  10. Herpes Simplex Viruses (Genus Simplexvirus) תעודת זהות • דנ”א דו-גדילי ארוך • גליקו-חלבונים של מעטפת gB-gN • חודים (spikes)

  11. הרפס סימפלקס-1Herpes Simplex Virus 1 (HSV-1) • נגיף ההרפס מסוג 1 שייך לנגיפי העור • ההדבקות הראשונית בנגיף מתרחשת בד”כ בילדות במגע עורי • ב- %15 ממקרי ההדבקות מתפתחת מחלה הידועה כפצעי קור או אבעבועות חום • סימפטומים: הפצעים/אבעבועות מתפתחים בדר”כ בשפתיים ועוברים כאשר הזיהום עובר

  12. הרפס סימפלקס-1Herpes Simplex Virus 1 (HSV-1) • הנגיף נשאר רדום בתאי העצב המקשרים בין הפנים למערכת העצבים • הנגיף חוזר בעקבות חשיפה יתרה לקרני UVשל השמש, במצבי לחץ או בעקבות שינוי הורמונלי • סיבוכים:Herpetic Keraitis - הזדהמות של קרנית העין בנגיף. במקרים נדירים הוירוס מגיע למוח וגורם שם לדלקת Herpes Encephalitis

  13. הרפס סימפלקס-1Herpes Simplex Virus 1 (HSV-1)

  14. הרפס סימפלקס-2(Herpes Simplex Virus 2 (HSV-2 • נגיף ההרפס מסוג 2 שייך לנגיפי מערכת הרבייה • הנגיף מועבר לראשונה על יד מגע מיני • סימפטומים: תחושת צריבה באברי הרבייה, אחר”כ מתפתחות שלפוחיות וכאבים במתן שתן. השלפוחיות מתרפות תוך כמה שבועות • באופן כללי, המחלה חמורה יותר מזו שמתפתחת בעקבות HSV-1

  15. הרפס סימפלקס-2(Herpes Simplex Virus 2 (HSV-2 • הנגיף נשאר רדום בתאי העצב ליד עמוד השדרה • הנגיף חוזר בעקבות שינויים הורמונליים, מצבי לחץ, מחלה מלווה בחום • סיבוכים: במקרים נדירים הוירוס מגיע למוח וגורם שם לדלקת Herpes Encephalitis • מניעה: קונדום • תרופה: כימותרפיה, Acyclovir

  16. Life cycle of HSV-1(productive infection) • Entry by fusion • Immediate-early genes transcription • Early genes transcription • Late gene expression • Budding from nucleus • Exocytosis

  17. HSV latent infection • Initiation occurs as in steps 1-7 of the productive infection • Occurs primarily in neurons of sensory and autonomic ganglia • Transcription is severe restricted

  18. Latent vs lytic cycle • During symptomatic infection, infected cells transcribe lytic viral genes. • In some host cells, certain viral genes enable the virus to persist in the cell (and thus the host) indefinitely – latent state. • long-term latency is symptom-free. • During the activation of latent virus, transcription of viral genes switches to lytic genes that lead to enhanced replication and virus production. • Often, lytic activation leads to cell death.

  19. HSV produces latent infection • Over 40 million people in USA harbor latent HSV in their peripheral nervous system • These cells are excluded from some forms of immune surveillance. They neither replicate their DNA nor divide. • Sensory neurons are highly connected through synapses.

  20. HSV produces latent infection • The ability of the virus to establish a latent infection is an effective survival mechanisms, as neither vaccines nor antivirals can attack the virus in its latent form. • Once infected with HSV, the host is infected for life - latency is absolute persistence.

  21. Epstein Barr Virus(EBV) • is one of the most common viruses in humans. • binds to receptors present on the surface of B cells. • Following primary infection, the virus persists in a latent form in the B-lymphocytes of the host. • causes mononucleosis and is a contributing factor in the development of Burkitt's lymphoma, a cancer of B lymphocytes. • uses tricks to prevent apoptosis of the B cells (thus enabling a cancer cell to continue to proliferate). • Most people have antibodies by the time they reach adulthood. • It has been postulated to be a trigger for a subset of Chronic Fatigue Syndrome patients

  22. Infectious Mononucleosisמחלת הנשיקה • Illness results from primary infection with EBV. • Infectious mononucleosis is caused when a person is first exposed to the virus during or after adolescence.

  23. מהו מונונוקלאוזיס זוהי מחלה זיהומית הנגרמת בכ-95% של המקרים על ידי נגיף האפשטין-בר ועל ידי הנגיף ציטומגלווירוס. שניהם חברים במשפחת נגיפי ההרפס. ההדבקה נעשית מאדם לאדם דרך נוזלי הפה ומגיעה לכלי הדם. היא תוקפת את המערכת החיסונית, מערכת העצבים ולעיתים את הטחול והכבד

  24. סימפטומים עיקריים • חום • גרון צורב שקדים מוגדלים ומוגלתיים • קשרי לימפה מוגדלים במיוחד בגרון • גושים בבית השחי • הרגשת עייפות וכאבי שרירים • איבוד תאבון • טחול ולפעמים גם כבד מוגדלים • סימפטומים נפוצים פחות: צהבת, כאב ראש,קשיחות של הצוואר, שיעול, קוצר נשימה, דופק מואץ או לא סדיר, דימום באף

  25. מהלך המחלה • פרט לסימפטומים הנ"ל, אבחנת המחלה דורשת ביצוע ספירת דם לבדיקת מספר הלימפוציטים (אשר גדל ב-10% במהלך המחלה) ונוגדנים ספציפיים לאפשטין-בר וירוס.בנוסף יש לשלול מחלות בעלות סימפטומיםדומים הנגרמות על ידיCYTOMEGALOVIRUS או ADENOVIRUS • המחלה נפוצה ביותר בקרב תינוקות כאשרהחיסון הטבעי שהם מקבלים מהאם נעלם. • המחלה בגיל זה אינה ממושכת ונראית לעיתים כמו עוד מחלת תינוקות קצרה אחרת. • המחלה יכולה להתפתח בכל גיל אך מאובחנת בדרך כלל בין הגילאים 10 ל-35 ושיא התפוצה שלה מופיע בקרב גילאי 17-15.

  26. Why is It So Hard to Diagnose? • The diagnosis of mono is suggested on the basis of its symptoms • 2 laboratory tests are needed for confirmation: • A white blood cell count- EBV causes an increase in a specific type of white blood cell, the atypical lymphocyte. • the "mono spot" identifies an antibody that is present in mononucleosis. This test may not become positive until you have had symptoms from 5 days to several weeks and may remain positive for months to years.

  27. מהלך המחלה • הסימפטומים מופיעים לאחר תקופת דגירה של שבוע עד שישה שבועות. במהלך תקופה זו יכול הנשא להפיץ את הנגיף בקלות רבה יחסית (הנגיף מועבר ברוק). • טחול מוגדל יכול לגרום לכאבי בטן ובמקרים נדירים ישנה קריעה של הטחול. • וב-8% -10% מעורב גם הכבד ומתפתחת צהבת. • כמו כן יתכנו בעיות לב ובעיות במערכת העצבים. • רוב הסימפטומים נעלמים לאחר מספר שבועות אולםהחולה עלול לחוש חולשה וכאבי שרירים גם חודשים אחדים לאחר העלמות המחלה.

  28. סיום המחלה או איך נפתרים מזה • המחלה נעלמת אחרי שבועיים עד חודש. • אם המחלה אינה עוברת יש לפנות לרופא מחשש לסיבוכים של המחלה כגון זיהום חיידקי. • עם סיום המחלה נשארים נגיפי EBVברוק ובדם בצורה רדומה למשך כל ימי חייו של החולה. • הנגיף פורץ בתקופות מסוימות לעיתים כתוצאה ממצבים קיצוניים. • וההתפרצויות המחודשת של הנגיף יילוו בכל הסימפטומים שהצגנו.

  29. טיפול • הטיפול הוא ביסודו סימפטומטי. לדוגמה: על כאבי הראש והגרון ניתן להקל באמצעות משככי כאבים • מנוחה מוחלטת הכרחית בשלבים הראשונים של המחלה ובמקרים בהם יש פגיעה בכבד • יש להימנע מפעילות פיזית עד להעלמות המחלה • חשוב מאוד להימנע משתיית אלכוהול מחשש לגרימת נזק בלתי הפיך לכבד, • וממצבי לחץ העלולים לגרום להתפרצות מחודשת של המחלה.

  30. Mononucleosis • Coughing or other contact with infected saliva can also pass Epstein-Barr virus from one person to another. • The mono virus can stay active in a person weeks or months after all overt symptoms are gone, so close contact with someone who shows no sign of the disease can still put a person at risk. On the other hand, a healthy immune system may make it possible to fight off the infection successfully. • About 90% of people over 35 have been infected with it, probably during early childhood, and have antibodies to the virus in their blood.

  31. How Can I Prevent It? • Most people will come in contact with this virus in their lifetime, so there is no guaranteed way to prevent catching mononucleosis. One can play it safe by not sharing eating utensils, water bottles, or straws. • Keeping your immune system strong with proper rest, exercise, and diet could play a role in keeping you from becoming very ill from this illness.

  32. At the Minnesota Rennaissance Festival on 15 September 1990, Alfred Wolfram kissed 8001 people in 8 hours - over sixteen people a minute.

  33. Burkitt’s Lymphoma (BL) • Burkitt's lymphoma (or "Burkitt's tumor") is a cancer of the lymphatic system (in particular, B lymphocytes). • It is associated with the Epstein-Barr virus • It is named after Denis Parsons Burkitt, a surgeon who first described the disease in 1956 while working in equatorial Africa. • Children affected with the disease often also had chronic malaria which is believed to have reduced resistance to the virus. • Disease characteristics include large tumors in the facial or abdominal regions.

  34. EBV • One molecule of linear double stranded DNA. • Total genome length is 170,000 nt • Like all herpesviruses is encased within an icosahedral capsid and enveloped.

  35. Epstein-Barr Virus Life Cycle • The EBV attaches to the outside of the cell, and is internalized by the cell. • Once inside the virus releases its DNA content, which enters the nucleus and integrates (?) into the hosts DNA. • The viral proteins will then be expressed, to begin the formation of new virus.

  36. EBV proteins in latent cycle • A very limited, distinct set of viral proteins are produced during latent cycle infection. • These include: • Epstein-Barr nuclear antigen (EBNA)-1, EBNA-2, EBNA-3A, EBNA-3B, EBNA-3C, EBNA-leader protein (EBNA-LP) • latent membrane proteins (LMP)-1, LMP-2A and LMP-2B • and the Epstein-Barr encoded RNAs (EBERs)

  37. Pathology • It is these proteins, which allow the immune system (T cells) to seek out EBV infected cells, and destroy them. • With EBV this process is not 100% effective, and a small population of EBV positive cells will remain. • This gives rise to life-long infection.

  38. Epstein-Barr virus-associated cancers: aetiology and treatment • Evidence implicates Epstein-Barr virus (EBV) in the pathogenesis of tumors arising in lymphoid or epithelial tissue. • EBV may adopt different forms of latent infection in different tumor types, reflecting the complex interplay between virus and host-cell environment. • Immune response is another important factor influencing EBV gene expression, and viral latent proteins to which immunodominant CTL responses are directed (namely the EBNA3 family), are downregulated in virus-associated tumours arising in overtly immunocompetent individuals.

  39. Human carcinogenicity • Since the large majority of the world's population is latently infected with EBV, the mere presence of the virus in tumor tissue is insufficient to establish the causality between the tumor and EBV. • Since B-lymphocytes are a normal reservoir for latent infection, the presence of EBV-infected lymphocytes in tumor tissue may be either incidental or an effect of the tumor rather than its cause.

  40. Human carcinogenicity • Therefore in order to establish the causality between the tumor and EBV other factors should be considered: • (1) the proportion of EBV-positive cases in a given tumor entity, • (2) the proportion of tumor cells that carry the virus in any given case, • (3) the monoclonality of EBV in the tumor (suggesting the presence of latent infection prior to expansion of the malignant clone); and, • (4) the expression of EBV proteins.

  41. Epidemiology • EBV infection is not uniform throughout the population. • Studies have been done on patients contracting Hodgkin’s disease (a type of cancer affecting cells of lymph nodes), and their levels of EBV infection. • This data has been plotted to see if there is a link between EBV, and class. • A social class does not influence EBV proportions in females, but is much more pronounced in males. Figure - Correlation between social index, and EBV infection.

  42. Drugs and Vaccines • Few drugs are available that prevent viral replication without significant toxicity. • Acyclovir and a number of related compounds have been used successfully to reduce viral replication but with no significant effect on persistent infection. • As with most viruses, the best chance of defense against Epstein-Barr is vaccination. Yet a vaccine has been elusive, partly because the virus is so good at hiding.

  43. The search for a vaccine • To prevent Burkitt’s lymphoma or nasopharyngeal carcinoma, a vaccine would need to provide 100% immunity or be capable of establishing a T-cell population that recognizes EBNA1. Both tasks are extremely difficult. It may be possible, though, to produce a vaccine against mononucleosis and post-transplant lymphoproliferative disease, since both produce antigens that are recognized by T-cells.

  44. The search for a vaccine • the first steps in the development of the vaccine was to define the antigens of the virus that stimulate the manufacture of T-cells, thus enabling the immune system to eliminate the infected cells. • The antibodies would neutralize the virus via virus surface glycoprotein gp350/220. • Artificially introduced live recombinant virus vectors, have been used to express the gp350/220 antigen. These elicited antibodies in EBV-negative Chinese infants. • then the immune system might be ‘tricked’ into producing T-cells that would recognize the real antigen should infection occur. • clinical trials of this candidate vaccine are under way.

  45. How would a vaccine help transplant patients? • A donor organ may harbour latent EBV. • The patient is given immunosuppressive drugs to prevent organ rejection -> immune system is supressed. • Cells chronically infected by EBV in the organ can become cancerous and form tumours. • The introduction of an EBV vaccine would allow transplant patients to be immunised before they receive an organ transplant. • the vaccine would activate a strong T-cell response to eliminate hidden EBV-infected cells. • Given the enormous investment in any individual transplant, this vaccine would potentially have a very wide market.

  46. Israeli Innovations in Biotechnology • Diagnostics, particularly monoclonal antibody-based test kits, were among Israel's first biotech successes.