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NBME2
Which of the following features of the inactivated poliovirus vaccine best explains why it prevents paralytic polio but does not prevent replication of the virulent poliovirus in the enteric tract?
1. It does not elicit cell-mediated immunity to viral capsid proteins
2. It does not elicit neutralizing antibody to virulent poliovirus
3. It elicits IgG but not secretory IgA
4. It only protects against one serotype of virulent poliovirus
anybody has a good explanation for this q???
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if that is in my exam.....i would say AAA
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quansar...pls put the nbme tag in the title itself....i will be great help for ppl like me who are planning to take the nbme for assessment.....thanks
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3333
The route of adminstration is IM. So doesnt illicite IgA production.
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The route of adminstration is IM??? AS far as I know, it is via oral
I picked AA too but I forgot why I picked A at the time
the given answer was 333
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Fido, sorry about that.
But u better be careful answering the qs on the forum then. I saw many qs on the forum posted from NBMEs these past couple weeks and most of them were without any NBME mark.
one advice for you, do not look at Jovana's qs.
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quansar, its opv which is given orally( not IPV)
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u r right, Getayakal. but still I found this piece of info. seems like both IPV and OPV induces IgA. It seems option 4 is the answer
Vaccination with either IPV or OPV is associated with the production high titers of serum or circulatory IgG antibody to poliovirus. Both vaccines induced neutralizing IgG antibody to the whole virus, IgG antibody to VP1 and VP3, and similar secretory IgA antibody to VP1 and VP2 in the nasopharyngeal secretions (NPS) without any VP3 response. Antibody response to VP2 and VP3 may be short lived. The peak concentrations are normally observed after four doses of vaccine. Both vaccines have been associated with effective serconversion rates and paralytic poliomyelitis prevention.
IPV primary route of action is through the activation of the immune system to produce serum or circulating IgG antibodies against poliovirus. Serum antibodies to poliovirus are unable to limit primary viral replication in the mucosal epithelium. However, they have been shown to prevent CNS invasion by poliovirus by neutralizing polioviruses that have entered the circulatory system, effectively protecting vacinees from poliomyelitis. IPV has also been known to induce specific IgA antibodies, conferring gastrointestinal immunity to a certain extent. However, E-IPV still allows higher levels of shedding in stool for longer periods than OPV when vacinees are challenged with live virus. Immunization with IPV has been shown to induce antibodies that begin to decline after vaccination but persist at low levels for a prolonged period. IgG antibody levels plateau relatively quickly and remain high years after immunization while IgA levels slowly increased. IgM displayed a drop in titer over time. OPV shows the same general trend in antibody proliferation over time with the exception of inducing higher IgA titers.Ã IPV has also been shown to confer herd immunity at a level equal to that of OPV. IPV immunization is associated with enhancement of secretory IgA response to poliovirus in nasopharynx that results in a marked reduction in viral nasopharyngeal excretion. Such a response may limit pharyngeal spread of poliovirus among community members. It has been suggested that pharyngeal shedding is a result of secondary viral localization from the blood. The fact that IPV is able to induce neutralizing serum antibodies would explain the prevention of pharyngeal shedding of poliovirus with IPV.
OPV is able to induce both a serum IgG and secretory IgA antibody response. The IgA response is much more pronounced after immunization with OPV than with IPV. The immune response to OPV resembles that of natural infection. Although OPV decreases fecal shedding of poliovirus, gastrointestinal immunity induced by OPV can be overcome by a sufficient dose of challenge virus. IgA induced after OPV may be directed against epitopes not available with IPV vaccine because of the proteolytic effects of intestinal enzymatic environment.
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getayalak,quansar or anyone
can u explain the mechanism of 2 form of polio vaccine
i am also confused.
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qansar, I dont think option 4 could be the answer. As to my knowledge IPV provides protection against three sero types.
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getayakal, I think you may be right.
rumi56, I do not know too much about MOA of the vaccine, but major difference is that they are administrated via different route thus may elicit different response.
It is inactivated or killed virus vaccine so you will get mainly humeral response, aka, antibody protection.
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