Longitudinal human serum antibody responses to outer membrane antigens of Actinobacillus actinomycetemcomitans

We hypothesize that serum antibody responses to antigens of a periodontopat hogen would vary temporally and that the specificity of these host antibodi es would relate to infection and disease activity. To test the hypothesis, we obtained between 6 and 13 serum samples from Actinobacillus actinomycete mcomitans (Aa)-positive (serological and microbiological) periodontitis pat ients at time points between 18 and 42 months into the study, and evaluated specific antibody responses to outer membrane antigens (OMA) of Aa strain Y4. Sera from these patients detected 22 different OMA. Early-onset (EOP; n =7) and adult (AP; n=11) periodontitis patients responded to 35% and 41% of the OMA, respectively. 2 of 9 sera from healthy subjects detected no antig ens and 7/9 sera detected 7% of the OMA (p<0.0001 versus EOP and AP). The f requency of antibody responses to the 17 kDa antigen mere similar between d iseased, infected patients and the uninfected, normal subjects, suggesting that it may be stimulated as a cross-reactive antigen. Antibody to the 28, 38, and 90 kDa antigens were significantly more common in diseased patients (>90%) versus normal subjects (p<0.01, p<0.002, and p<0.002, respectively) and were unique among diseased, infected patients, which may be indicative of infections with Aa. A 65 kDa antigen showed an increased frequency of r eaction in the AP versus the EOP (p=0.01) patients, which exemplified a pot ential distinction in response to A(Aa between adult and early-onset diseas e classifications. Seventeen of 22 OMA could be detected in every sample fr om at least one patient. Longitudinal samples from seropositive EOP and AP reacted 80-100% of the time with the 17, 28, and 100 kDa antigens. Finally, five antigens of 15, 38, 58, 65, and 79 kDa were detected in 33-83% of the seropositive patients; however, antibody to these OMA reacted variably at different sampling points, suggesting some antigenic response diversity ove r time.