Preventive disease specialists working in a developing country are investigating vaccination options to limit the spread of poliomyelitis. As part of the study, 2 patients are vaccinated against poliomyelitis. One patient receives an intramuscular inactivated vaccine and the other patient receives a live attenuated oral vaccine. One month after vaccination, the levels of which of the following poliovirus antibodies will differ the most between these 2 patients?
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Secretory IgA is the major antibody associated with mucosal immunity. Upon intestinal exposure to a novel antigen, B cells found in mesenteric lymph nodes and Peyer's patches become activated and preferentially migrate to the lamina propria underlying the intestinal mucosa. There, they become fully differentiated plasma cells that begin to synthesize IgA dimers (linked by J chain). These IgA dimers then bind to the polymeric immunoglobulin receptor (pIgR) found on the basolateral surface of intestinal epithelial cells and undergo transcytosis. As the linked IgA dimer is released into the intestinal lumen, a portion of pIgR remains attached to the antibody (secretory component), forming the complete secretory IgA molecule.
Stimulation of local secretory IgA production is best promoted when the corresponding mucosal surfaces are directly stimulated by the antigen. In addition, live attenuated vaccines generally produce stronger immune responses than killed vaccines by acting as a persistent stimulus that better activates helper and cytotoxic T cells. As a result, the live attenuated oral (Sabin) poliovirus vaccine generates a much more robust oropharyngeal and intestinal mucosal IgA response than the inactivated poliovirus (Salk) vaccine.
(Choice A) Cerebrospinal fluid IgG antibody levels can increase due to a rise in local production (eg, multiple sclerosis, viral CNS infections) or inflammation of the blood-brain barrier (eg, trauma, meningitis), leading to excessive leakage of plasma proteins.
(Choices C, D, and E) Serum IgA (mainly monomeric), IgG, and IgM increase with both forms of the polio vaccine and are protective against viral dissemination. Serum IgG and IgM can also be secreted by the mucosa although to a lesser extent than secretory IgA (explaining why most patients with selective IgA deficiency are asymptomatic).
Educational objective:
The live attenuated oral (Sabin) poliovirus vaccine produces a stronger mucosal secretory IgA immune response than does the inactivated poliovirus (Salk) vaccine. This increase in mucosal IgA offers immune protection at the site of viral entry by inhibiting attachment to intestinal epithelial cells.