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Microbiology

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RNA Viruses

Question
29 out of 94
 

A 28-year-old woman presents with symptoms of jaundice, right upper quadrant pain, and vomiting. She also has elevated ALT. It is determined that she acquired hepatitis A from a church picnic where several other adults also became infected. What should be done to protect the family members? (AIPG 2010)



A One dose of HAV immunoglobulin should be administered intramuscularly.

B No treatment is necessary.

C A series of three vaccinations should be administered at 0, 1, and 6 months.

D Alpha interferon should be administered.

Ans. A One dose of HAV immunoglobulin should be administered intramuscularly.

a. HAV immunoglobulin should be given to household contacts in one IM dose. This must be done within 14 days of exposure to the index patient as prophylaxis against hepatitis A.

b. The series of three vaccinations at time 0, 1, and 6 months, refers to the immunization schedule for hepatitis B, not hepatitis A. This would not be protective for those exposed to HAV.

c. Alpha interferon is used to treat symptomatic patients with HBV and HCV, not prophylaxis of family members of patients with HAV.

Extra Edge:

HBV Vaccines

a. Plasma-derived hepatitis B vaccine: It consists of purified 22 nm particles of HBsAg, prepared from the plasma of symptomless carriers.

b. The particles are separated by ultracentrifugation and treated with proteinase, 8M urea and formaldehyde. The chemical treatment inactivates HBV, HIV and other contaminating viruses.

c. The product is immunogenic and safe. This vaccine is still being produced and used, particularly in developing countries where the need is greatest.

d. Recombinant yeast hepatitis B vaccine: It is produced by cloning the HBsAg gene in yeasts Saccharomyces cerevisae and the HBsAg particles produced are extracted and purified for use as vaccine.

e. This vaccine is safe, antigenic, free from side effects and as immunogenic as plasma-derived vaccine.

f. Both vaccines are adsorbed with aluminium hydroxide as adjuvant, stored in cold but not frozen and are injected intramuscularly into the deltoid region in a course of three doses given at 0, 1 and 6 months.

g. Care should be taken to avoid injection into fat as this may produce poorer seroconversion rates.

h. Recombinant chinese hamster ovary (CHO) cell hepatitis vaccine: Expression system of CHO cells has been successfully used and the product is commercially available. This is the first vaccine using mammalian cell expression system.

i. Synthetic peptide vaccines: As the name indicates these are chemically synthesized polypeptide vaccines. These are safe and cheap. These are still under experimental stage.

j. Hybrid virus vaccine: Potential live vaccines using recombinant vaccinia virus have been prepared for hepatitis B, influenza, rabies, Epstein-Barr and human immunodeficiency viruses.

k. Recombinant vaccines can be generated by incorporating foreign genes (HBsAg sequences in case of HBY) into vaccinia virus DNA. Animal cells are first infected with vaccinia virus.

l. Subsequently, a plasmid containing the foreign gene of interest and promoter and thymidine kinase sequences from vaccinia virus is introduced.

m. During replication of vaccinia virus DNA, the plasmid sequences are also replicated and chimeric viral DNA containing the foreign gene is produced.

n. Recombinant vaccinia virus expresses proteins (HBsAg in case of HBV) encoded by foreign gene.

o. The advantages of vaccinia virus recombinant vaccine include low cost, long shelf-life and possible use of polyvalent antigens.

RNA Viruses Flashcard List

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