Colonization of the upper respiratory tract by pneumococcus is important both as a determinant of disease and for transmission into the population. The immunological mechanisms that contain pneumococcus during colonization are well studied in mice but remain unclear in humans. Loss of this control of pneumococcus following infection with influenza virus is associated with secondary bacterial pneumonia. We used a human challenge model with type 6B pneumococcus to show that acquisition of pneumococcus induced early degranulation of resident neutrophils and recruitment of monocytes to the nose. Monocyte function was associated with the clearance of pneumococcus. Prior nasal infection with live attenuated influenza virus induced inflammation, impaired innate immune function and altered genome-wide nasal gene responses to the carriage of pneumococcus. Levels of the cytokine CXCL10, promoted by viral infection, at the time pneumococcus was encountered were positively associated with bacterial load.

Influenza virus infections affect millions of people annually, and current available vaccines provide varying rates of protection. However, the way in which the nasal microbiota, particularly established pneumococcal colonization, shape the response to influenza vaccination is not yet fully understood. In this study, we inoculated healthy adults with live Streptococcus pneumoniae and vaccinated them 3 days later with either tetravalent-inactivated influenza vaccine (TIV) or live attenuated influenza vaccine (LAIV). Vaccine-induced immune responses were assessed in nose, blood, and lung. Nasal pneumococcal colonization had no impact upon TIV-induced antibody responses to influenza, which manifested in all compartments. However, experimentally induced pneumococcal colonization dampened LAIV-mediated mucosal antibody responses, primarily IgA in the nose and IgG in the lung. Pulmonary influenza-specific cellular responses were more apparent in the LAIV group compared with either the TIV or an unvaccinated group. These results indicate that TIV and LAIV elicit differential immunity to adults and that LAIV immunogenicity is diminished by the nasal presence of S . pneumoniae . Therefore, nasopharyngeal pneumococcal colonization may affect LAIV efficacy.

Hematopoietic stem and progenitor cells (HSPCs) are predominantly quiescent in adults, but proliferate in response to bone marrow (BM) injury. Here, we show that deletion of Ca2+/calmodulin (CaM)-dependent protein kinase kinase 2 (CaMKK2) promotes HSPC regeneration and hematopoietic recovery following radiation injury. Using Camkk2-enhanced green fluorescent protein (EGFP) reporter mice, we found that Camkk2 expression is developmentally regulated in HSPC. Deletion of Camkk2 in HSPC results in a significant downregulation of genes affiliated with the quiescent signature. Accordingly, HSPC from Camkk2 null mice have a high proliferative capability when stimulated in vitro in the presence of BM-derived endothelial cells. In addition, Camkk2 null mice are more resistant to radiation injury and show accelerated hematopoietic recovery, enhanced HSPC regeneration and ultimately a prolonged survival following sublethal or lethal total body irradiation. Mechanistically, we propose that CaMKK2 regulates the HSPC response to hematopoietic damage by coupling radiation signaling to activation of the anti-proliferative AMP-activated protein kinase. Finally, we demonstrated that systemic administration of the small molecule CaMKK2 inhibitor, STO-609, to irradiated mice enhanced HSPC recovery and improved survival. These findings identify CaMKK2 as an important regulator of HSPC regeneration and demonstrate CaMKK2 inhibition is a novel approach to promoting hematopoietic recovery after BM injury.

Influenza virus infections affect millions of people annually. Current available vaccines provide varying rates of protection. There is a knowledge gap on how the nasal microbiota, particularly established pneumococcal colonization, shapes the response to influenza vaccination. In this study, we inoculated healthy adults with live S. pneumoniae and vaccinated them three days later with either TIV or LAIV. Vaccine-induced immune responses were assessed in nose, blood and lung. Nasal pneumococcal colonization had no impact upon TIV-induced antibody responses to influenza, which manifested in all compartments. However, pre-existing pneumococcal colonization dampened LAIV-mediated mucosal antibody responses, primarily IgA in the nose and IgG in the lung. Pulmonary influenza-specific cellular responses were more apparent in the LAIV group compared to either TIV or an unvaccinated group. These results indicate that TIV and LAIV elicit differential immunity to adults and that LAIV immunogenicity is diminished by the nasal presence of S. pneumoniae. This important confounder should be considered when assessing LAIV efficacy.

Secondary bacterial pneumonia following influenza infection is a significant cause of mortality worldwide. Upper respiratory tract pneumococcal carriage is important as both determinants of disease and population transmission. The immunological mechanisms that contain pneumococcal carriage are well-studied in mice but remain unclear in humans. Loss of this control of carriage following influenza infection is associated with secondary bacterial pneumonia during seasonal and pandemic outbreaks. We used a human type 6B pneumococcal challenge model to show that carriage acquisition induces early degranulation of resident neutrophils and recruitment of monocytes to the nose. Monocyte function associated with clearance of pneumococcal carriage. Prior nasal infection with live attenuated influenza virus induced inflammation, impaired innate function and altered genome-wide nasal gene responses to pneumococcal carriage. Levels of the cytokine IP-10 promoted by viral infection at the time of pneumococcal encounter was positively associated with bacterial density. These findings provide novel insights in nasal immunity to pneumococcus and viral-bacterial interactions during co-infection.