Maternal Protection In Mice Against HPAIV And Its Interference On Active Immunization

This thesis consists of four parts.1)Brief introduction of influenza virus,influenza in pregnant women and infant;introduction of maternal antibody;2)Comparison of protection against H5N1 influenza virus in mouse offspring provided by maternal vaccination with HA DNA and inactivated vaccine;3)The study of mucosal immunization in the presence of maternal antibody in BALB/c mice;4)Vaccination with hemagglutinin DNA protects BALB/c mice against influenza virus infection in presence of maternal antibody.1)An overview of influenza A virus features and characteristics;the previous flu pandemic and seasonal epidemic in pregnant women,fetuses and infants;clinical vaccine application status in infant and pregnant women;protection principle and application of maternal antibody in infants and young children,the interference of maternal antibodies to active immune response in infants and interference principle;strategies overcoming the maternal antibody interference in some research.2)Compared with season influenza,people generally lack pre-existing immunity against H5N1 influenza virus.Pregnant women and infants both belong to the highrisk population,and maternal immunization with H5N1influenza vaccine is a very important way to protect mothers and newborns from H5N1 influenza infection.In clinical studies,when inactivated H5N1 influenza vaccines were tested,large doses or multiple immunizations were needed to induce sufficiently high antibody levels due tothe relatively low immunogenicity of the vaccines,so WHO encourage new type of vaccine.In this study,female mice were immunized with H5N1 HA DNA vaccine or whole-virion inactivated vaccine,and the protective abilities provided by maternal antibodies in their offspring against a lethal homologous influenza virus challenge were compared.The results showed that the maternal antibodies,whether induced by DNA vaccine or inactivated vaccine,could completely protect the offspring aged 1-4 weeks from a lethal influenza virus challenge.Breast-feeding was the major transfer passage for maternal antibodies.The milk-derived antibodies could effectively protect the offspring aged 1-4 weeks from the lethal influenza virus infection;whereas the maternal antibodies transferred through placenta only partially protected the offspring of 1-2 week age.The milk and placenta transferred IgG2a antibody levels in offspring from their mothers,whether vaccinated with DNA vaccine or inactivated vaccine,were relatively higher than IgGl levels.Our results indicated that,maternal vaccination with HA DNA,as well as with whole-virion inactivated vaccine,could offer effective protection to offspring against H5N1 influenza virus infection.3)This chapter focuses on different immune pathways in overcoming the maternal antibody interference effect.Using BALB/c mice as animal model,in the presence of high maternal antibody induced by H5N1 inactivated vaccine,the offspring were immunized with inactivated H5N1 vaccine through intramuscular,subcutaneous,intraperitoneal,mucosal immune route respectively;we found that mucosal immunity has a role in the resistance to maternal antibody interference,so we focus on the mucosal immune.The experimental results show that:when the mothers and offspring were vaccinated with inactivated vaccine through intraperitoneal injection route,active immune response were inhibited by maternal antibody,even if administration high dose(5 fig)vaccine,interference effects cannot be overcome;When offspring vaccinated with mucosal immune method,low dose(0.1?g)vaccine can not overcome the interference of maternal antibody,but the higher dose(1?g)vaccine can overcome the interferences.When both mother and the offspring were immunized with inactivated vaccine through mucosal inoculation,we also found that low dose(0.1?g)cannot overcome interference of maternal antibody,but higher dose(1 ?g)vaccine can overcome the interference;When the offspring were vaccinated by intraperitoneal way even if administration high dose(5 ?g)vaccine,antibody to the active immune response interference cannot be overcome.The above results show that regardless of the maternal immune mode selection,nasal mucosal immunity can overcome the maternal antibody interference effect on the active immune response.The experimental results provide experimental reference for the clinical and breeding progeny of timely vaccination against influenza virus infection.4)In this chapter,we focus on the effect of H5N1 HA DNA in the presence of maternal antibody.Compared with the traditional vaccine,DNA vaccine can in vivo expression for a long time,so the DNA might be an option to overcome maternal antibody interference effect,so in this experiment,we chose H5N1 HA DNA vaccine as research object.In this experiment,female BALB/c mice were immunized with 1 ?g and 0.10 ?g doses of H5N1 inactivated vaccine respectively,so the antibody titers are also different in their offspring,and then 30?g H5N1 HA DNA vaccine administration of offspring mice twice.Through detection the antibody titers after vaccination,the residual virus titer in lung,survival rate and other indicators after challenge to evaluate the immune effect of the vaccine.Experimental results show that:when the mother were inoculated with 0.10 ?g dose inactivated vaccine,the offspring inoculation of 30?g H5N1 HA DNA vaccine can overcome the interference of maternal antibody;when mother were inoculated 1?g of vaccine,offspring inoculated HA DNA vaccine does not overcome the interference of maternal antibodies.This results show that,HA DNA vaccines have a certain role in overcoming the interference of maternal antibody titers and the concentration of maternal antibody at the time of immunization are key factors to decide whether interference can happen.