Mechanism Of7-valent Pneumococcal Conjugate Vaccine Immunization On Experimental Allergic Asthma

Background and ObjectiveAsthma is the most common chronic airway inflammatory disease, themorbidity of it increase continuously. In present all the methods treatingasthma only control the symptoms, so people make effert to find an effectivemethod to treat and prevent asthma. Studies demonstrated CpG-ODNs andBCG can inhibit allergic airway disease (AAD) in mouse models. However,treatments with CpG-ODN may induce harmful side effects, while BCG hasno efficacy on allergic asthma in human. Pneumococci is a commonrespiratory pathogen, causing pneumonia, otitis media, meningitis andsepticaemia. Epidemiological studies demonstrated that7-valentpneumococcal conjugate vaccine (PCV7) immunization reduce theincidence of asthma and associated hospitalization in both children and theelderly. Study stated PCV7immunization in adulthood mice inhibit thehallmark features of AAD through promoting production of Tregs andsuppressing production of Th2cells. PCV7immunization is usually administered in infancy to prevent childhood pneumococci infection.Whether infant PCV7immunization can alter young adulthood CD4+T cellsubsets and inhibit experimental allergic asthma or not remains elusive.Dendritic cells (DCs) is one kind of professional antigen presentationcell and can activate CD4+T cells. DCs can induce immune tolerance andimmune response depending on the conditions. Regulation the function ofDCs can treat and prevent asthma. Bone marrow-derived dendritic cell(BMDC) develop into immature DCs cultured in interleukin (IL)-4andGM-CSF (granulocyte–macrophage colonystimulating factor), andimmature DCs can be activated into mature DCs by antigen. Mature DCsexpress more MHCⅡ and costimulatory molecules CD80、CD86、CD40.Study showed that BCG can suppress DCs immaturation to take part inimmune tolerance. Whether infant PCV7immunization can suppress DCsimmaturation or not is unclear. In this part we investigated the effects ofPCV7on DCs maturity in vivo and vitro so as to state the possiblemechanism of PCV7immunization inhibiting young adult experimentalallergic asthma.Part I Infant PCV7immunization alters young adulthoodairway inflammation and CD4+T cell subsets in experimentalallergic asthma mouse model Background Streptococcus pneumonia is the first bacterial pathogen ofcommunity acquired respiratory infection, PCV7is recommended in childento prevent Streptococcus pneumoniae disease, PCV7immunization canreduce the times and severity of asthma outbreak then prevent asthma. Thisvaccine in adulthood mice inhibit the hallmark features of AAD throughpromotion of Tregs and suppression of Th2cells. Furthermore, PCV7immunization is currently administered in infancy to prevent childhoodpneumococci infections. Whether infant PCV7immunization can alteryoung adulthood CD4+T cell subsets and inhibit experimental allergicasthma or not remains elusive. In this study we investigated the effects ofinfant PCV7on airway inflammation and CD4+T cell subsets in youngadulthood experimental allergic asthma mouse models and to lay the basisfor later studies.Objective To investigate the effects of infant PCV7immunization onairway inflammation and CD4+T cell subsets in young adulthoodexperimental allergic asthma mouse models.Methods Specific pathogen free(SPF) level3-week-old BALB/c micewere randomized divided into control group，PCV7immunization andexperimental allergic asthma group (PCV7+OVA group), experimentalallergic asthma (OVA group). PCV7+OVA group mice were administeredintranasally with PCV7, PCV7+OVA and OVA group mice were sensitized and then challenged with ovalbumin. The airway responsiveness andpulmonary tissue inflammation were detected after24hours later of the lastchallenge. The levels of INF-γ、IL-4、IL-5、IL-13、IL-17A、TGF-β、IL-10in BALF and the subsets of CD4+Th cells in mediastinal lymph node (MLN)were detected.Results The symptoms of PCV7+OVA group mice were morealleviative than that in OVA group mice. The airway hyperresponsiveness ofPCV7+OVA group mice were significantly lower than that in OVA groupmice. Simultaneous, the airway inflammation in PCV7+OVA group micewere more alleviative than that in OVA group mice. The total inflammatorycells, eosinophils and neutrophils accumulation in BALF of PCV7+OVAgroup were significantly lower compared with those in BALF of OVA group.However, the production of IL-13and IL-17A was significantly lower butIFN-γ and IL-10was significantly higher in the infant PCV7immunizedgroup mice than those in the OVA group mice. The production ofFoxp3+Tregs and Th1cells increased but Th2and Th17cells decreased inPCV7+OVA group mice.Conclusion Infant PCV7immunization may serve as an effectivemeasure to prevent young adulthood mice allergic asthma. Part II Mechanism of PCV7Immunization on DCsInfant PCV7immunization may be an effective measure to preventyoung adulthood asthma through promoting Foxp3+Treg, Th1cells andinhibiting Th2and Th17cells, but the mechanism remains unclear. Dendriticcells (DCs) is a kind of professional antigen presentation cells and canactivate CD4+T cells. DCs can induce immune tolerance and immuneresponse depending on the conditions. Regulation the function of DCs cantreat and prevent asthma. Bone marrow-derived dendritic cell (BMDC)develop into immature DCs cultured in interleukin (IL)-4and GM-CSF(granulocyte–macrophage colonystimulating factor), immature DCs can beactivated into mature DCs by antigen，mature DC express more MHCⅡandcostimulatory molecules CD80、 CD86、 CD40. Whether infant PCV7immunization can suppress DCs maturation or not is unclear. In this part weinvestigated the effects of PCV7immunization on DCs maturity in vivo andvitro so as to state the possible mechanism of PCV7immunizationinhibiting experimental allergic asthma.Objective To investigate effect of PCV7immunization on DCsmaturity in vivo and vitro so as to state the possible mechanism of PCV7immunization inhibiting experimental allergic asthma.Methods Specific pathogen free level3-week-old BALB/c mice were randomized control group, PCV7immunization and experimental allergicasthma group (PCV7+OVA group), experimental allergic asthma group(OVA group). PCV7+OVA group mice were administered intranasally withPCV7, PCV7+OVA group and OVA group mice were sensitized and thenchallenged with ovalbumin. MHCⅡ, CD80, CD86, CD40in lung and MHCⅡ, CD80, CD86, CD40in MLN were detected by FCM. The levels ofINF-γ、IL-4、IL-5、IL-13、IL-17A、TGF-β and IL-10BALF were detectedby ELISA. Mononuclear cells were collected by density gradientcentrifugation from4-week-old mice bone marrow. Bone marrowmononuclear cells differentiated and proliferated into DC by supplementingwith low dose rmGM-CSF and rmIL-4. In the seventh day DC in negativecontrol group were added PBS, those in PCV7and positive control (OVA)group were added PCV7and OVA respectively. On the ninth day, DC wereidentified by morphology by light microscope, the surface makers by flowcytometry （FCM）, the cytokines in supernatant by Enzyme-linkedimmunoadsorbent assay (ELISA).Results MHCⅡ, CD86, CD40in lung and MHCⅡ, CD86, CD40，CD80in mediastinal lymph nodes of PCV7+OVA group mice were lowerthan those in OVA group mice. However, the production of IL-13andIL-17A was significantly lower but IFN-γ and IL-10was significantlyhigher in the infant PCV7immunized group mice than those in the OVA group mice. Immature DCs in PCV7group were significantly higher thanthose in OVA group, DCs in PCV7group showed significantly lower levelof MHCⅡ, CD86and CD40than those in OVA group. IL-12p70, IL-6inDCs supernatant of PCV7group were significantly lower than those in OVAgroup, but TGF-β in DCs supernatant of PCV7group were significantlyhigher than that in OVA group.Conclusion The mechanism of infant PCV7immunization preventingyoung adulthood asthma is possibly associated with PCV7suppressing DCsmaturation and promoting Foxp3+Tregs expressions.