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Why the MMR Vaccine must be a live attenuated vaccine?

  • a- Killed version will result in short term immunity
  • b- Measles, mumps, and rubella cause syncytia formation
  • c- TH2 response is needed
  • d- Antibodies won't recognize surface proteins
  • e- To prevent contamination of the vaccine with other viruses
I have no answer or explanation for that
Please help
 

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  • A killed vaccine may not necessarily give short term immunity. For example Polio (Salk) is a killed vaccine and gives long term immunity. So choice A is incorrect.
  • TH1 (cell mediated) response rather than TH2 (antibody mediated) response is elicited by live viral vaccines. So choice C is incorrect.
  • Antibodies do recognize surface proteins. For example hepatitis B immunoglobulins given to neonates of HBsAg +ve mothers. So choice D is incorrect.
  • Live virus vaccines are more likely to be contaminated with other viruses as opposed to killed vaccines. So choice E is incorrect.

You are left with Choice B.
Mumps, Measles, Rubella, Respiratory Syncytial Virus, Parainfluenza, and Human Metapneumovirus they are all members of the paramyxoviridae family and they are capable of syncytia formation. This means they can jump from one cell to another without being extruded to the extracellular space. Antibodies are found in the extracellular space only. So these viruses evade the humoral immunity. Therefore the only way to kill them is via intacellular mechanisms i.e. cell mediated immunity. That's why your MMR vaccine must be live-attenuated.
 

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Awesome explanation indeed Steptaker! I was wondering why you need cell-mediated immunity, but it makes sense that since these viruses form syncytia, you would need a means to kill them intracellularly.
 

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Wow steptaker, I love how you narrowed it down to the answer with reasoning. Need to practice this tactic for the real deal.
 

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Oh My God !!
I never thought this thread still exist! that was long long time ago :rolleyes:
Haha, I actually found this thread via google...was looking up how MMR works and why you need cell-mediated immunity- perfect explanation in a nutshell :) I noticed it was an old thread, but the principles still apply!
 

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  • A killed vaccine may not necessarily give short term immunity. For example Polio (Salk) is a killed vaccine and gives long term immunity. So choice A is incorrect.
  • TH1 (cell mediated) response rather than TH2 (antibody mediated) response is elicited by live viral vaccines. So choice C is incorrect.
  • Antibodies do recognize surface proteins. For example hepatitis B immunoglobulins given to neonates of HBsAg +ve mothers. So choice D is incorrect.
  • Live virus vaccines are more likely to be contaminated with other viruses as opposed to killed vaccines. So choice E is incorrect.

You are left with Choice B.
Mumps, Measles, Rubella, Respiratory Syncytial Virus, Parainfluenza, and Human Metapneumovirus they are all members of the paramyxoviridae family and they are capable of syncytia formation. This means they can jump from one cell to another without being extruded to the extracellular space. Antibodies are found in the extracellular space only. So these viruses evade the humoral immunity. Therefore the only way to kill them is via intacellular mechanisms i.e. cell mediated immunity. That's why your MMR vaccine must be live-attenuated.
awesome explanation!
 

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  • A killed vaccine may not necessarily give short term immunity. For example Polio (Salk) is a killed vaccine and gives long term immunity. So choice A is incorrect.
  • TH1 (cell mediated) response rather than TH2 (antibody mediated) response is elicited by live viral vaccines. So choice C is incorrect.
  • Antibodies do recognize surface proteins. For example hepatitis B immunoglobulins given to neonates of HBsAg +ve mothers. So choice D is incorrect.
  • Live virus vaccines are more likely to be contaminated with other viruses as opposed to killed vaccines. So choice E is incorrect.

You are left with Choice B.
Mumps, Measles, Rubella, Respiratory Syncytial Virus, Parainfluenza, and Human Metapneumovirus they are all members of the paramyxoviridae family and they are capable of syncytia formation. This means they can jump from one cell to another without being extruded to the extracellular space. Antibodies are found in the extracellular space only. So these viruses evade the humoral immunity. Therefore the only way to kill them is via intacellular mechanisms i.e. cell mediated immunity. That's why your MMR vaccine must be live-attenuated.
StepTaker correct me if im wrong but isnt rubella part of Togaviridae? which does NOT make syncitia formation? (only paramyxovirus, herpesviridae, and retrovirus have this unique characteristic)
:confused:
 
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