Pox Virus

 Edward Jenner

REF: Jawetz’s 24^th ed chapter 34

Edward Jenner introduced vaccination for small pox with live cowpox virus in 1798.

Cross-immunity with animal pox virus [Ref Park 21/e p132,133 (20/e p131, 132)] 203

Among the various animal pox viruses the two animal pox viruses – the monkey pox and the tanapox viruses are potentially capable of infecting humans.

Small pox vaccination protects from monkey pox but not from tanapox. Monkey pox came to notice after small pox was eradicated and is a rare disease and so cross-immunity with monkey pox cannot render any contribution to small pox eradication.

Rather with elimination of vaccination and waning immunity against small pox, an increase in human monkey pox cases may occur.

Small pox eradication:

• Small pox was declared eradicated on 8^th May 1980.
• The epidemiological factors which led to small pox eradication are as follows:
• Highly effective, heat stable and easily administrable vaccine that confers long-term protection.
• Life long immunity after recovery from the disease.
• Persons with sub-clinical infection did not transmit the disease.
• No known animal reservoir
• No long term carrier of the virus.
• Easily detectable clinical cases
• International cooperation

Ans. is ‘a’ i.e., Antigenic cross reactivity

Antigenic specificity ‑

–   Antibodies are able to differentiate slight chemical differences between molecules, demonstrating that each antigen possesses specificity.

Antigenic cross reactivity ‑

–   antigenic specificity is not absolute.

–    sometimes single antigen stimulates production of variety of antibodies that more or less resemble the correct fit for the antigen. Each of these antibodies may attack different antigens that more or less resemble one another This is known as antigenic cross reactivity..

• Now, the antigenic properties of Poxvirus ‑

– Large number of antigens are present.

– Some of them are common within each subgroup and so serologic cross reactions and cross resistance between individual viruses have been observed.

– All pox virus share a common antigen nucleoprotein (NP), which is responsible for neutralization of infectivity and acquired immunity.

–  So this antigens is used to prepare vaccines which can be used both in small pox and cow pox.

Ans. is ‘b’ i.e., Vaccinia; ‘c’ i.e., Adenovirus 

“Vaccinia virus is being employed as a vector for the development of recombinant vaccine.” -Ananthnarayan – 7^th 469 “Recombinant poxviruses, influenza virus and adenoviruses are also being used experimentally as vaccine vectors.”

– Harrison Remember

.   Retroviruses integrate into cell genome and have been used in patients with severe combined immunodeficiency (SCID) to replace abnormal gene in T cells.

.  Recombinant adenovirus, AAV and retroviruses are used in diseases due to single gene defects, such as cystic fibrosis and hemophilia.

Ans. is ‘b’ i.e., Rabies 

.     Vaccines prepared in embrvonated Hen’s ettg :

–     Influenza (grown in allantoic cavity)      – Rabies

–     Yellow fever                                        – Mumps

.     Vaccines from Duck eeg

–     Non neural rabies vaccine

Ans. is ‘a’ i.e., Guarnieri bodies 

Eosinophilic inclusion bodies – Guarnieri bodies – can be demonstrated in stained preparation of variola and vaccinia viruses.

Ans. is ‘c’ i.e., Molluscum contagiosum 

• Humans are the only susceptible host and therefore molluscum contagiosum virus cannot be grown in eggs, tissue cultures or animals.

Ans. is ‘d’ i.e., Molluscum 

• Humans are the only susceptible hosts for molluscum contagiosum virus. The virus cannot be grown in eggs, tissue cultures or animals.
• Vaccinia virus may be grown in wide range of animals.
• Variola can be grown in monkey.
• Cowpox virus, as the name suggests, infects cow; and also humans.

Ans. is `a’ i.e., 1 

• There are four types of molluscum contagiosum virus, MCV-1 to MCV-4.
• MCV-1 is the most prevalent.
• MCV-2 is seen usually in adults and often sexually transmitted.

Ans. is ‘a’ i.e., Poxviruses