Human Staphylococcus aureus (SA) nasal carriage provides a reservoir for the dissemination of infectious strains; however, factors regulating the establishment and persistence of nasal colonization are mostly unknown. We measured carriage duration and nasal fluid inflammatory markers after nasally inoculating healthy participants with their previously isolated SA strains. Ten out of 15 studies resulted in rapid clearance (9±6 days) that corresponded with upregulated chemokines, growth factors, and predominantly Th1-type cytokines, but not IL-17. Nasal SA persistence corresponded with elevated baseline levels of MIP-1β, IL-1β, and IL-6, no induction of inflammatory factors post-inoculation, and decreased IL-1RA:IL-1β ratio. SA-expressed staphylococcal protein A (SpA) levels correlated positively with carriage duration. Competitive inoculation studies revealed that isogenic SpA knockout (ΔSpA) strains were cleared faster than wild-type only in participants with upregulated inflammatory markers post-inoculation. The remaining participants did not mount an inflammatory response and did not clear either strain. ΔSpA strains demonstrated lower growth rates in carrier nasal fluids and lower survival rates when incubated with neutrophils. Collectively, the presented studies identify innate immune effectors that cooperatively modulate nasal carriage duration, and confirm SpA as a bacterial co-determinant of SA nasal carriage.

Transmission-blocking vaccines are urgently needed to reduce transmission of SARS-CoV 2, the cause of the COVID-19 pandemic. The upper respiratory tract is an initial site of SARS-CoV-2 infection and, for many individuals, remains the primary site of virus replication. An ideal COVID-19 vaccine should reduce upper respiratory tract virus replication and block transmission as well as protect against severe disease. Here, we optimized a vaccine candidate, parainfluenza virus 5 (PIV5) expressing the SARS-CoV-2 S protein (CVXGA1), and then demonstrated that a single-dose intranasal immunization with CVXGA1 protects against lethal infection of K18-hACE2 mice, a severe disease model. CVXGA1 immunization also prevented virus infection of ferrets and blocked contact transmission. This mucosal vaccine strategy inhibited SARS-CoV-2 replication in the upper respiratory tract, thus preventing disease progression to the lower respiratory tract. A PIV5-based mucosal vaccine provides a strategy to induce protective innate and cellular immune responses and reduce SARS-CoV-2 infection and transmission in populations.

nasal carriage is transient in most humans and usually benign, but dissemination of to extranasal sites causes the majority of clinical infections, and is a major cause of serious infections in the United States. A better understanding of innate nasal decolonization mechanisms is urgently needed, as are relevant models for studying clearance. Here, we screened a population of healthy smokers for nasal carriage and compared the participants' abilities to clear experimentally applied nasal before and after completion of a smoking cessation program. We determined that cigarette smoking increases the mean nasal load (2.6 × 10 CFU/swab) compared to the load observed in healthy nonsmokers (1.7 × 10 CFU/swab) and might increase the rate of nasal carriage in otherwise-healthy adults: 22 of 99 smokers carried at the screening visit, while only 4 of 30 nonsmokers screened positive during the same time period. Only 6 of 19 experimental inoculation studies in active smokers resulted in clearance within the month of follow-up, while in the cessation group, 6 of 9 subjects cleared nasal and carriage duration averaged 21 ± 4 days. Smoking cessation associated with enhanced expression of -associated interleukin-1β (IL-1β) and granulocyte colony-stimulating factor (G-CSF) in nasal fluids. Participants who failed to clear exhibited a higher nasal load and elevated nasal interleukin-1 receptor antagonist (IL-1RA) expression at the preexperiment study visits. We conclude that smokers exhibit higher loads than nonsmokers and that innate immune pathways, including G-CSF expression and signaling through the IL-1 axis, are important mediators of nasal clearance.

The search for a preventive vaccine against HIV infection remains an ongoing challenge, indicating the need for novel approaches. Parainfluenza virus 5 (PIV5) is a paramyxovirus replicating in the upper airways that is not associated with any animal or human pathology. In animal models, PIV5-vectored vaccines have shown protection against influenza, RSV, and other human pathogens. Here, we generated PIV5 vaccines expressing HIV envelope (Env) and SIV Gag and administered them intranasally to macaques, followed by boosting with virus-like particles (VLPs) containing trimeric HIV Env. Moreover, we compared the immune responses generated by PIV5-SHIV prime/VLPs boost regimen in naïve vs a control group in which pre-existing immunity to the PIV5 vector was established. We demonstrate for the first time that intranasal administration of PIV5-based HIV vaccines is safe, well-tolerated and immunogenic, and that boosting with adjuvanted trimeric Env VLPs enhances humoral and cellular immune responses. The PIV5 prime/VLPs boost regimen induced robust and durable systemic and mucosal Env-specific antibody titers with functional activities including ADCC and neutralization. This regimen also induced highly polyfunctional antigen-specific T cell responses. Importantly, we show that diminished responses due to PIV5 pre-existing immunity can be overcome in part with VLP protein boosts. Overall, these results establish that PIV5-based HIV vaccine candidates are promising and warrant further investigation including moving on to primate challenge studies.

nasal carriage is a common condition affecting both healthy and immunocompromised populations and provides a reservoir for dissemination of potentially infectious strains by casual contact. The factors regulating the onset and duration of nasal colonization are mostly unknown, and a human-relevant animal model is needed. Here, we screened 17 pig-tailed macaques () for carriage, and 14 of 17 animals tested positive in the nose at one or both screening sessions (8 weeks apart), while the other 3 animals were negative in the nose but positive in the pharynx at least once. As in humans, colonization was densest in the nose, and treatment of the nostrils with mupirocin ointment effectively cleared the nostrils and 6 extranasal body sites. Experimental nasal colonization was established with 10 CFU/nostril, and both autologous and nonautologous strains survived over 40 days without any apparent adverse effects. A human nasal isolate (strain D579, sequence type 398) was carried in 4 of 6 animals for over 3 weeks. Nostrils that did eradicate experimentally applied exhibited neutrophilic innate immunity marked by elevated nasal interleukin-1β (IL-1β), IL-8, and monocyte chemotactic protein 1 levels and a 10-fold decreased IL-1 receptor antagonist/IL-1β ratio within 7 days postinoculation, analogous to the human condition. Taken together, pig-tailed macaques represent a physiological model of human nasal carriage that may be utilized for testing natural colonization and decolonization mechanisms as well as novel classes of anti- therapeutics.