1. Vaccination& Viral Infections
L. Dalia Kamal Eldien
MSc in Microbiology
Lecture NO: 7

2. Question for revision Define the virus Identify the virus structure
Enumerate the virus transmission mode
Classify the virus according to the type of nucleic acid

3. Outlines Principles of antiviral therapy
Vaccination & types of vaccine
Common viral disease

4. Viral Infections

5. Principles of antiviral therapy
Compared with the number of drugs available to treat bacterial infections, the number of antiviral drugs is very small
Antiviral chemotherapy typically involves a delicate interplay between host cellular functions and viral targets of action.
Many antiviral agents do significant host cellular toxicity, a limitation that has prevent antiviral drug development.
In spite of this limitation, a number of agents are licensed for use against viruses, particularly herpesviruses, respiratory viruses, and hepatitis viruses.

6. Examples to some antiviral drugs
Amantadine: This drug specifically inhibits influenza virus
Maraviroc: blocks the binding of HIV to CCR-5—an important co-receptor for those strains of HIV that use CCR-5 for entry into the cell
Interferon: is effective in the treatment of some patients with chronic hepatitis B and chronic hepatitis C infections

7. Antibiotics don't treat the viral infection
Note:-
Antibiotics don't treat the viral infection 

8. History of Vaccination
British physician, Edward Jenner, noticed that milkmaids were protected from smallpox if they had been first infected with cowpox 
Jenner's work led him to the conclusion, that inoculation with cowpox could confer immunity to smallpox. 
Thus, the concept of vaccination was initiated.

9. Edward Jenner

10. Vaccination
A vaccine is a biological preparation that enhances immunity to a particular disease.
The vaccine stimulates the body's immune system to produce specific antibodies or a cellular immune response that destroys or neutralizes the microorganism or its toxins.

11. Viral vaccination Prevention of viral diseases can be achieved by:
Vaccines that induce active immunity or
Vaccines of preformed antibody that provides passive immunity

12. Vaccines that induce active immunity

13. Types of vaccine
There are three types of vaccines that induce active immunity:
Vaccine contain live virus whose their pathogenicity has been attenuated
Vaccine contain killed virus.
Subunit vaccines, some vaccines, such as the hepatitis B vaccine, contain purified viral proteins

14. Question
Which is the more effective vaccine& why? A- Vaccine contain live virus B- Vaccine contain killed virus

15. Answer
Live vaccines are preferred to vaccines containing killed virus because of: Greater protection and longer-lasting.
Live vaccines initiate an infection without causing any injury or disease.
Killed vaccines are less immunogenic than live vaccines, and protection lasts for a short period.
Therefore, to be given repeatedly; generally at least two doses are required.
The first dose is called primary dose and the subsequent doses as booster doses.

16. Some examples to live, attenuated vaccine:-
Measles mumps, rubella (MMR combined vaccine)
Oral polio vaccine –Sabin-
Influenza
Rotavirus
Some examples to inactivated/Killed vaccine:-
Polio (IPV- Salk-)
Hepatitis A
Rabies

17. Vaccine contain preformed antibody that provides passive immunity

18. Artificial passive immunization is the resistance achieved by injecting a recipient with preformed immunoglobulins
Can be injected during the incubation period to limit viral multiplication or to neutralize the toxins
Because passive immunization does not activate the immune system, it generates no memory response.

19. Artificial passive immunity
The four most commonly used immunoglobulin preparations are as follows.
(i) Human Hepatitis B Immunoglobulin
(ii) Human Rabies Immunoglobulin
(iii) Human Varicella-Zoster Immunoglobulin  
(iv) Human Tetanus Immunoglobulin

20. Artificial passive immunity

22. Influenza Virus
Influenza viruses are common pathogens of the upper respiratory tract
Influenza viruses are classified as types A, B, and C, depending on proteins (M) and nucleoprotein (NP)
Only the type A viruses are broken down into subtypes.
Influenza virus A subtypes are designated by a nomenclature that is based on their surface glycoproteins—namely, Hemagglutinin (H) and Neuraminidase (N)

23. Influenza type A virus
The H antigen is used to bind to host cells, and N cleaves budding viruses from infected cells.
There are 16 H antigens (H1 through H16), although most human infections usually occur with H1, H2& H3
There are a total of 9 N antigens (N1 through N9); human infections usually occur with N1& N2.
The key to the persistence of the influenza virus is its antigenic variation.

24. Influenza virus structure

25. Influenza Virus
Typically human and avian influenza viruses are different and are not infectious for both species.
Emergence of new influenza strains in the human population occurs via transmission from other animal species, especially poultry.
Pigs have receptors for both avian and human influenza viruses, as well as swine influenza viruses, and can be co-infected with all three types of viruses.

26. Influenza Virus
A reassortment occurs when the genome of different influenza viruses becomes mixed, resulting in a new strain of virus.
Occasionally, direct avian–human transmission can occur, often with enhanced pathogenicity, as demonstrated by the emergence of the recent H5N1 avian influenza in many countries throughout Southeast Asia; human-to-human spread of H5N1 avian influenza has not been conclusively documented.

28. Viral hepatitis
Viral hepatitis is an infection of the liver caused by one of several viruses.
The most common types of viral hepatitis are:
Hepatitis A is caused by the Hepatitis A virus (HAV)
Hepatitis B is caused by the Hepatitis B virus (HBV)
Hepatitis C is caused by the Hepatitis C virus (HCV)
While all three types of hepatitis can cause similar symptoms, each virus is spread in different ways.

29. Hepatitis A
Hepatitis A virus is a small, icosahedral, naked ssRNA virus
Hepatitis A disease is an acute infectious disease of the liver
Mode of transmission: the disease is highly transmissible through the faecal-oral route, even in microscopic amounts
Hepatitis A is often asymptomatic or mild, particularly in children below five years of age, but the severity increases with age.

30. Hepatitis B Hepatitis B virus is an enveloped, partially dsDNA virus
Mode of transmission: spread through contact with infected body fluids or blood products, primarily through:
Birth to an infected mother
Sexual contact with an infected person
Blood transfusion
Sharing of contaminated needles, syringes, or other injection drug equipment or other sharp instrument .
The symptoms can vary greatly and many of those who get infected never develop any symptoms at all.

31. Hepatitis C HCV is an ssRNA virus
Hepatitis C is a liver disease caused by infection with the hepatitis C virus (HCV)
Mode of transmission: is mainly acquired by contact through broken skin with infectious blood.
Hepatitis C is most often passed on by people who inject drugs by sharing contaminated needles; transmission may also occur through tattooing, body piercing and acupuncture, if these are done in unsterile conditions.

32. Incubation period
Incubation Period for hepatitis A is: 15 to 50 days (average: 28 days)
Incubation Period for hepatitis B is: 45 to 160 days (average: 120 days)
Incubation Period for hepatitis C is:14 to 180 days (average: 45 days)

33. Sings& symptoms
Many people with viral hepatitis do not have symptoms and do not know they are infected.
For acute hepatitis, symptoms usually appear within several weeks to several months of exposure and can last up to 6 months.
Symptoms of chronic viral hepatitis can take decades to develop and people can live with an infection for years and not feel sick.

34. Sings& symptoms
Symptoms for both acute and chronic viral hepatitis can include:
Fever
Fatigue
loss of appetite& Nausea
Vomiting
Abdominal pain
Dark urine, grey-colored stools,
Jaundice.

35. Yellowing of skin& eyes

36. Treatment
For people with acute hepatitis, doctors usually recommend rest, adequate nutrition, fluids, and in certain situations, antiviral medication.
In some cases, people with acute hepatitis are hospitalized.
Several treatments are available that can significantly improve health and delay or reverse the effects of liver disease for those with Hepatitis B and new treatments are available for Hepatitis C that can get rid of or clear the virus.

37. Vaccination Recommendations
Hepatitis A: 2 doses given 6 months apart
Hepatitis B:
Infants and children: 3 to 4 doses given over a 6- to 18-month period depending on vaccine type and schedule
Adults: 3 doses given over a 6-month period
Hepatitis C: No vaccine available

39. HIV virus structure

40. Human Immunodeficiency Virus HIV
Human immunodeficiency virus (HIV) causes progressive impairment of the body’s cellular immune system, leading to increased susceptibility to infections and tumors, and the fatal condition AIDS (acquired immunodeficiency syndrome).
There are two main types of the virus, HIV-1 which causes most HIV infections worldwide and HIV-2 which is found mainly in West Africa.
HIV is an enveloped RNA virus

41. Mode of transmission
HIV is spread through contact with certain body fluids from a person infected with HIV.
HIV is present in semen, vaginal/cervical secretions and blood, and these are the main vehicles by which the virus is transmitted.
The virus may also be present in saliva, tears, urine, breast milk, cerebrospinal fluid and infected discharges
Once HIV enters the body, the primary target cells are the CD4+ T cells, monocytes, and macrophages, which are white blood cells that help the body fight infection and disease

42. Symptoms
Soon after infection with HIV, some people have flu-like symptoms, such as fever, headache, or rash.
The symptoms may come and go for a month .
After this earliest stage of HIV infection, HIV continues to multiply but at very low levels.
More severe symptoms of HIV infection, such as chronic diarrhea, rapid weight loss, and other signs of opportunistic infections, generally don’t appear for many years.

43. Diagnosis
The laboratory diagnosis of HIV infection is by detecting antibody to HIV (anti-HIV 1, anti-HIV 2) in a person’s serum
Anti-HIV is usually present within 3–6 weeks following infection.

44. Criteria used to follow up the patient
The following criteria used to determine if a person infected with HIV has AIDS:
The person’s immune system is severely damaged as indicated by a CD4 count of less than 200 cells/mm3
The CD4 count of a healthy person is just over 1,000 cells/mm3
When CD4 cells are depleted, immune defenses are weakened

45. Treatment
The use of HIV medicines to treat HIV infection is called antiretroviral therapy (ART).
ART involves taking a combination of HIV medicines (called an HIV regimen) every day. 
ART can’t cure HIV infection, but it can help people infected with HIV live longer, healthier lives.
HIV medicines can also reduce the risk of transmission of HIV.

46. By this lecture we finish the chapter of virus

47. Sources for more reading
Microbiology, Lippincott’s Illustrated Reviews. Cynthia Nau Cornelissen, Bruce D. Fisher, Richard A. Harvey. Third edition (chapter 5)
Textbook of Diagnostic Microbiology-Fifth edition- Connie R. Mahon, MS- Donald C. Lehman, EdD, MT(ASCP), SM(NRM) - George Manuselis, MA, MT(ASCP)- Elsevier (2015) (Part II –page 688)
Notes on Medical Virology, Author: Eman K. Aldigs, Published by OMICS Group eBooks 731 Gull Ave, Foster City. CA 94404, USA