Human nasal challenge with Streptococcus pneumoniae is immunising in the absence of carriage.

Infectious challenge of the human nasal mucosa elicits immune responses that determine the fate of the host-bacterial interaction; leading either to clearance, colonisation and/or disease. Persistent antigenic exposure from pneumococcal colonisation can induce both humoral and cellular defences that are protective against carriage and disease. We challenged healthy adults intra-nasally with live 23F or 6B Streptococcus pneumoniae in two sequential cohorts and collected nasal wash, bronchoalveolar lavage (BAL) and blood before and 6 weeks after challenge. We hypothesised that both cohorts would successfully become colonised but this did not occur except for one volunteer. The effect of bacterial challenge without colonisation in healthy adults has not been previously assessed. We measured the antigen-specific humoral and cellular immune responses in challenged but not colonised volunteers by ELISA and Flow Cytometry. Antigen-specific responses were seen in each compartment both before and after bacterial challenge for both cohorts. Antigen-specific IgG and IgA levels were significantly elevated in nasal wash 6 weeks after challenge compared to baseline. Immunoglobulin responses to pneumococci were directed towards various protein targets but not capsular polysaccharide. 23F but not 6B challenge elevated IgG anti-PspA in BAL. Serum immunoglobulins did not increase in response to challenge. In neither challenge cohort was there any alteration in the frequencies of TNF, IL-17 or IFNγ producing CD4 T cells before or after challenge in BAL or blood. We show that simple, low dose mucosal exposure with pneumococci may immunise mucosal surfaces by augmenting anti-protein immunoglobulin responses; but not capsular or cellular responses. We hypothesise that mucosal exposure alone may not replicate the systemic immunising effect of experimental or natural carriage in humans.

Comparison between nasopharyngeal swab and nasal wash, using culture and PCR, in the detection of potential respiratory pathogens.

BACKGROUND: Nasopharyngeal carriage of potential pathogens is important as it is both the major source of transmission and the prerequisite of invasive disease. New methods for detecting carriage could improve comfort, accuracy and laboratory utility. The aims of this study were to compare the sensitivities of a nasopharyngeal swab (NPS) and a nasal wash (NW) in detecting potential respiratory pathogens in healthy adults using microbiological culture and PCR. RESULTS: Healthy volunteers attended for nasal washing and brushing of the posterior nasopharynx. Conventional and real-time PCR were used to detect pneumococcus and meningococcus. Statistical differences between the two nasal sampling methods were determined using a nonparametric Mann-Whitney U test; differences between culture and PCR methods were determined using the McNemar test.Nasal washing was more comfortable for volunteers than swabbing (n = 24). In detection by culture, the NW was significantly more likely to detect pathogens than the NPS (p < 0.00001). Overall, there was a low carriage rate of pathogens in this sample; no significant difference was seen in the detection of bacteria between culture and PCR methods. CONCLUSIONS: Nasal washing and PCR may provide effective alternatives to nasopharyngeal swabbing and classical microbiology, respectively.

rhIL-12 as adjuvant augments lung cell cytokine responses to pneumococcal whole cell antigen.

Conjugate pneumococcal vaccines offer suboptimal protection against mucosal infections and are restricted in serotype and geographical coverage. New protein-based vaccines using conserved pneumococcal antigens and better mucosal adjuvant technology are urgently needed. Interleukin-12 (IL-12) has shown efficacy as a pneumococcal protein vaccine adjuvant in murine models of pneumococcal infection. Systemic administration of recombinant human (rh) IL-12 to humans, however, has been associated with adverse clinical and laboratory side effects. Inhaled forms of IL-12 have improved the safety profiles in humans, as suggested by animal models. Here we evaluated rhIL-12 as an adjuvant on ex vivo human BAL cells when stimulated with pneumococcal whole cells. We show that co-incubation of ex vivo human BAL cells with pneumococcal whole cell antigen (WCA) and a low dose of rhIL-12 (2 ng) can elevate TNF production compared to treatment with WCA (p=0.06) or rhIL-12 (p=0.03) alone. The production of IFNγ was also increased but not in an antigen specific manner, suggesting perhaps a predominant Th(1) response. Our data suggest that 100-200-fold lower doses of inhaled rhIL-12 than those previously tested for systemic use may be adequate in a phase 1 study and commend further evaluation of rhIL-12 as a potential mucosal adjuvant in human vaccine studies.