analyzed data and wrote the manuscript. should be taken into consideration when developing vaccines against bacterial pathogens. is JNJ-28312141 also known to cause tracheobronchitis and pharyngitis, and a myriad of extrapulmonary conditions, including potentially lethal conditions affecting the cardiovascular and central nervous systems1. contamination has been recently found to be associated with chronic obstructive pulmonary disease and asthma exacerbation, as evidenced by studies indicating that 50% of patients with chronic asthma are PCR and/or culture positive for is usually spread person-to-person by aerosolized droplets that result from persistent coughing, and respiratory manifestations such as indolent tracheobronchitis and pharyngitis are thought to be major contributors to this spread6,7. Given that transmission is usually facilitated by close contact, outbreaks typically occur in crowded conditions such as day-care centers, hospitals, military barracks, and college dormitories, with the incidence of disease exceeding 70% among uncovered populations8C11. Many cases of go undiagnosed or misdiagnosed due to inadequate diagnostic assessments, often resulting in mistreatment, and potentially contributing to the rise of antibiotic resistant strains2,12C14. Atypical pneumonia due to contamination has also been a major cause of morbidity in, and thus affects readiness of, military populations; having caused 61% of prolonged, non-productive coughs in US soldiers deployed in South Korea, 42% of hospitalizations in US soldiers with pneumonia during the Vietnam War, and 22% of respiratory infections among all US military personnel during Operation Enduring Freedom15C17. Naturally acquired immunity from JNJ-28312141 previous infections tends to be short lived, and recurrent infections of an Rabbit Polyclonal to AQP12 individual can occur1,2. Taken together, the burden of on public health, along with limited preventative and therapeutic steps against vaccine, yet no vaccines are currently available in part due to Vaccine-Enhanced Disease (VED). VED was first reported in human volunteers in the 1960s when federal prisoners were vaccinated with a formalin-inactivated vaccine then challenged with a virulent strain. While protective effects were observed in some participants, 36% of vaccinated individuals exhibited more severe clinical symptoms upon challenge than those receiving a placebo18,19. This VED phenomenon has created a major roadblock to additional vaccine studies. Recent studies have recapitulated VED in a BALB/c mouse model of respiratory infection, utilizing live-attenuated vaccines or crude protein extract20C23. In this VED model, vaccinated mice exhibit more severe lung histopathology post-challenge than unvaccinated mice, and lesion severity is usually associated with elevated IL-17A20C24. Using the BALB/c model, we recently reported that vaccination with LAMPS caused VED that is dependent on the lipid moieties of lipoproteins; however, the immunological mechanisms behind this phenomenon remain poorly comprehended25. Understanding these mechanisms remains of utmost importance as it can serve to inform the design of a safe and efficacious vaccine candidate. Mycoplasma lipoproteins are known to drive immune responses upon binding to TLR-2 (in conjunction with TLR-1 for triacylated lipoproteins and TLR-6 for diacylated lipoproteins) expressed on many cell types, resulting in the production of inflammatory cytokines such as TNF- and IL-6 among others26. lipoproteins have also been shown to activate the NLRP3 inflammasome and induce the expression of IL-1 in a Gasdermin D and pyroptosis impartial manner27C29. TLR-2 stimulation by lipoproteins has furthermore been linked to the expression of IL-23 by activated macrophages, which itself induces production of IL-17A by CD4?+?T cells and subsequent IL-17A-driven neutrophil granulopoiesis, recruitment, and activation30C32. Neutrophils contribute to JNJ-28312141 lung lesions, lung injury, and overall disease severity during pulmonary mycoplasmoses in multiple natural hosts, have been correlated with VED in mouse models, and have been associated with more severe disease in humans20C24,33C47. We therefore hypothesized that vaccine candidates made up of lipoproteins activate IL-17A responses which trigger neutrophil recruitment JNJ-28312141 (likely through the induction of the human IL-8 homolog, KC). Given that is usually resistant to phagocytosis and killing by neutrophils, their activation likely contributes to the observed immunopathology in lipoprotein-induced VED48,49. Results Inflammatory cytokines are elevated in lipoprotein-induced Mp VED To assess immune responses in our lipoprotein-induced VED model, we vaccinated mice with saline as a placebo, lipid-associated membrane proteins (LAMPs, which contain lipoproteins and other transmembrane proteins) or with delipidated LAMPs (dLAMPs) produced via enzymatic de-acylation (Fig. ?(Fig.1A,1A, Supplementary Fig. 1). Mice were intranasally challenged with 108 CFU of strain PI1428 (day 42 post-vaccination), then humanely sacrificed (day 46) to assess cytokine concentrations in bronchoalveolar lavage fluids (BALFs) and for histopathologic assessment of.