A scientist suspects a patient X has been previously exposed to Varicella-Zoster

Question

A scientist suspects a patient X has been previously exposed to Varicella-Zoster virus. To test her hypothesis, she designs an experiment using a Western Blot. For this experiment, she uses PAGE to resolve proteins prepared from purified Varicella-Zoster viruses. Blot I used the patient X serum and Blot II is her positive control (serum from patient Y that was KNOWN to be vaccinated against surface antigens of Varicella-Zoster virus before ever being exposed to the live virus). At the end of her experiment, she sees the following result shown below. She concludes that patient X was NOT exposed to Varicella-Zoster virus. Which of the following statements should be TRUE?

I II

Left: 1 Right: 1, 2, 3, 4, 5, 6, 7, 8 ,9

i) the primary antibody for blot I was the serum obtained from Y.

ii) the secondary antibody for both blots was obtained from patient Y.

iii) primary antibody for blot I was serum from patient X and primary antibody for blot II was from patient Y.

iv) for both blots she used secondary antibody that was serum from rabbits that were immunized with donkey IgG-Fc

v) for both blots she used secondary antibody that was serum from rabbits that were immunized with human IgG-Fc

vi) band 1 is a cross-reactive protein vii) bands 2-6 are Varicella-Zoster virus envelope proteins

viii) bands 2-6 are Varicella-Zoster virus proteins that are only expressed inside the host cell

A) i, iv, vi

B) ii, v, vi, vii

C) iii, v, vi, vii

D) iii, v, vii

E) none of the above

Explanation / Answer

The answer is iii,v,vi,vii

iii. The blot I should have used primary antibody as serum from patient X and blot II should have used serum as primary antibody from patient Y

v. As the primary antibodies are human serum, the secondary antibodies for both the blots should be raised in rabbit against the human IgG-Fc

vi. The band which appears in blot I is a cross reactive protein because it appears in blot II also. If that was against the varicella-zoster virus, blot should have more than one band.

vii. Bands 2-6 are varicella-zoater virus envelope proteins against which patient Y has been vaccinated.

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