Long-term antibody responses following human infection with Campylobacter jejuni

Abstract

Epidemiological evidence suggests prior infection of humans by Campylobacter jejuni leads to protection against disease following further exposure. It is known that infections elicit strong antibody responses following the onset of disease and that antibody levels are elevated in putatively immune populations. To determine if systemic and mucosal antibodies induced by a confirmed infection remain at elevated levels for prolonged periods, repeat serum, saliva and urine samples were taken from campylobacter patients from 1 week and up to a year postinfection. Antibodies were monitored by ELISAs using three different antigen preparations: acid-glycine extracts (AE) of C. jejuni strain 81116 and an aflagellate mutant (R2), and a whole-cell R2 sonicate, and by Western blotting. Levels of serum IgG antibodies against 81116AE and R2 sonicate, but not R2AE, remained significantly raised over time when compared to a comparison population. Serum anti-sonicate IgA antibody levels were initially significantly raised but decreased over time to levels similar to the comparison group. There were no significant differences in levels of salivary IgA against the AEs. Anti-sonicate salivary IgA and IgG levels were initially significantly higher than in the comparison group. Both declined over time but the IgG levels remained significantly higher. Significant correlations were seen between serum IgG levels and age and duration of illness. Serum antibodies against flagellin, 40 kDa and 29 kDa antigens were still detectable in most patients up to a year postinfection, as were salivary antibodies to flagellin, the major outer-membrane protein and a 40 kDa antigen.

Fig. 1

ELISA results (O.D.450) indicating levels of serum IgG and salivary IgA antibodies detectable against glycine/acid extracts (AE) of C. jejuni strains 81116 and its aflagellate mutant R2. Samples were taken from patients shortly after a diagnosed infection (first) and up to a year later (last) and from comparison groups. Significant differences between the first or last samples and the corresponding comparison group are indicated as follows (P-values): α < 0·001, β < 0·001, χ = 0·005. □, 81116 AE; R2 AE.

Fig. 2

ELISA results (O.D.450) indicating levels of serum and salivary IgG and IgA antibodies detectable against a whole-cell sonicate of C. jejuni strain R2. Significant differences between the first or last samples and corresponding comparison group are indicated as follows (P-values): α–δ < 0·001, ɛ = 0·029, φ = 0·002. □, IgG; ▪, IgA.

Fig. 3

Western blot showing patient antibody responses to C. jejuni strain 81116. Strips 1–5: IgG responses in the first serum samples from five patients; (6) rabbit antimajor outer-membrane protein; (7) IgA response in the first saliva sample from a patient. F indicates flagellin; M indicates the major outer-membrane protein.