Serum antibodies to putative proteinase maturation protein A in children with acute otitis media

No serological evidence of influenza A H1N1pdm09 virus infection as a contributing factor in childhood narcolepsy after Pandemrix vaccination campaign in Finland

BACKGROUND

Narcolepsy cataplexy syndrome, characterised by excessive daytime sleepiness and cataplexy, is strongly associated with a genetic marker, human leukocyte antigen (HLA) DQB1*06:02. A sudden increase in the incidence of childhood narcolepsy was observed after vaccination with AS03-adjuvanted Pandemrix influenza vaccine in Finland at the beginning of 2010. Here, we analysed whether the coinciding influenza A H1N1pdm pandemic contributed, together with the Pandemrix vaccination, to the increased incidence of childhood narcolepsy in 2010. The analysis was based on the presence or absence of antibody response against non-structural protein 1 (NS1) from H1N1pdm09 virus, which was not a component of Pandemrix vaccine.

METHODS

Non-structural (NS) 1 proteins from recombinant influenza A/Udorn/72 (H3N2) and influenza A/Finland/554/09 (H1N1pdm09) viruses were purified and used in Western blot analysis to determine specific antibody responses in human sera. The sera were obtained from 45 patients who fell ill with narcolepsy after vaccination with AS03-adjuvanted Pandemrix at the end of 2009, and from controls.

FINDINGS

Based on quantitative Western blot analysis, only two of the 45 (4.4%) Pandemrix-vaccinated narcoleptic patients showed specific antibody response against the NS1 protein from the H1N1pdm09 virus, indicating past infection with the H1N1pdm09 virus. Instead, paired serum samples from patients, who suffered from a laboratory confirmed H1N1pdm09 infection, showed high levels or diagnostic rises (96%) in H1N1pdm virus NS1-specific antibodies and very high cross-reactivity to H3N2 subtype influenza A virus NS1 protein.

CONCLUSION

Based on our findings, it is unlikely that H1N1pdm09 virus infection contributed to a sudden increase in the incidence of childhood narcolepsy observed in Finland in 2010 after AS03-adjuvanted Pandemrix vaccination.

Identification of the targets of cross-reactive antibodies induced by Streptococcus pneumoniae colonization

Much of the efficacy of current pneumococcal conjugate vaccines lies in their ability to decrease carriage of vaccine serotypes in the population. Novel and more-broadly acting vaccines would also need to target carriage in order to be as effective. We have previously shown that model murine carriage of Streptococcus pneumoniae can elicit antibody-dependent immunity and can protect against a virulent heterologous challenge strain. This study set out to identify S. pneumoniae surface antigens that may elicit cross-reactive antibodies following colonization. Western blot analysis using sera from colonized mice identified the previously characterized immunogens pneumococcal surface protein A (PspA), putative proteinase maturation protein A (PpmA), and pneumococcal surface adhesin A (PsaA) as such antigens. Using flow cytometry, PspA was found to be the major target of surface-bound cross-reactive IgG in sera from TIGR4 Delta cps-colonized mice, with a modest contribution from PpmA and none from PsaA. In human sera, however, only mutants lacking PpmA were shown to have reduced binding of surface IgG compared to wild-type strains, suggesting that prior exposure to S. pneumoniae in humans may induce PpmA antibodies. We also investigated if cross-reactive antibodies induced by these antigens may be cross-protective against carriage. Despite the immunogenicity of PspA, PpmA, and PsaA, mice were still protected following colonization with mutants lacking these antigens, suggesting they are not necessary for cross-protection induced by carriage. Our findings suggest that a whole-organism approach may be needed to broadly diminish carriage.

Diagnostic detection of Streptococcus pneumoniae PpmA in urine

Streptococcus pneumoniae infections are often difficult to diagnose accurately, as it is not uncommon for clinical samples to be culture-negative, particularly after antibiotic administration. The rapid Binax NOW S. pneumoniae urinary antigen test lacks specificity in children, owing to pneumococcal antigen reactions in children who are nasopharyngeal carriers of S. pneumoniae. A western blot assay with a specific polyclonal antibody was developed for direct detection of the putative proteinase maturation protein A (PpmA) in urine samples from children with pneumococcal infections. The sensitivity and specificity of the assay were 66.7% and 100%, respectively. Previous antibiotic treatment or S. pneumoniae nasopharyngeal colonization did not affect PpmA antigenuria. Results also demonstrated the presence of PpmA cross-reactive epitopes in commensal bacteria that co-colonize the nasopharyngeal niche, although the non-pneumococcal cross-reactive protein(s) did not interfere with the detection assay. S. pneumoniae PpmA in the urine of children with pneumococcal infections may be a marker that has the potential to be used in the clinical diagnosis of pneumococcal infection.