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Serological response to plasmid-encoded antigens in children and adults with shigellosis
P Echeverria1, S Hanchalay, D N Taylor
1Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand.
Insights
The study found that Thai children mounted a stronger antibody response to Shigella antigens than adults, despite adults having higher antibody titers. This suggests complex immune dynamics in Shigella infections.
Area of Science:
- Immunology
- Microbiology
- Infectious Diseases
Background:
- Shigella infections pose a significant public health challenge, particularly in developing countries.
- Understanding the host immune response is crucial for developing effective vaccines and treatments.
- Plasmid-encoded antigens are key virulence factors in Shigella pathogenesis.
Purpose of the Study:
- To investigate and compare the immunological response to plasmid-encoded Shigella antigens in Thai children and adults.
- To determine the role of antibody titers (IgG, IgA, IgM) in susceptibility to Shigella infections.
Main Methods:
- Immunoblot analysis and Enzyme-Linked Immunosorbent Assay (ELISA) were used to assess antibody responses.
- Paired acute and convalescent sera from Thai children and adults with shigellosis were analyzed.
- Antibody titers to water-extracted antigens of Shigella flexneri M90T were quantified.
Main Results:
- A significantly higher proportion of children (42%) showed a rise in IgG antibody titers compared to adults (4%) (p = 0.006).
- Adults exhibited higher reciprocal log2 geometric mean titers for IgG, IgM, and IgA antibodies in acute sera compared to children (p < 0.001).
- Immunoblot analysis detected additional antibody responses (IgA, IgM) not identified by ELISA in some patients.
Conclusions:
- Thai children mount a more robust antibody response to Shigella plasmid-encoded antigens during infection than adults.
- Despite high antibody titers in acute sera, Thai adults remain susceptible to Shigella infections, indicating limitations of antibody-mediated immunity alone.
- Further research is needed to elucidate the mechanisms underlying differential immune responses and susceptibility in various age groups.
Abstract:
The immunological response to plasmid-encoded antigens of virulent Shigella was determined in Thai children less than 4 yr of age and in Thai adults by immunoblot analysis and ELISA. Forty-two percent (8/19) of Thai children and 4% (1/22) of Thai adults with shigellosis developed a greater than or equal to 4-fold rise in IgG antibody titer to water-extracted antigens of Shigella flexneri M90T by ELISA (p = 0.006). Two children and one lactating mother with shigellosis developed a 4-fold rise in serum IgA antibody titers to water-extracted antigens of M90T. The results of the ELISA were confirmed by immunoblot analysis in all of the 41 paired sera examined. Five patients developed IgA, and four developed IgM, antibodies as detected by immunoblot analysis, that were not detected by ELISA. The reciprocal log2 geometric mean titers of antibodies to plasmid-encoded antigens in acute sera was higher in Thai adults than Thai children: IgG 7,265 versus 1,659; IgM 879 versus 480; and IgA 662 versus 60 (p less than 0.001). Thai adults had high titers of antibodies to plasmid-encoded antigens in their acute sera, but were susceptible to Shigella infections, although they were historically less susceptible than Thai children.