Mucosal immune responses and protective efficacy in yellow catfish after immersion vaccination with bivalent inactivated Aeromonas veronii and Edwardsiella ictaluri vaccine

Mucosal vaccination,which has the potential to induce both mucosal and systemic immune responses,is considered the most suitable method of preventing infectious diseases in farmed fish.Aeromonas veronii and Edwardsiella ictaluri are two pathogenic bacteria found in yellow catfish and often infect the fish through mucosal surfaces.Delivery of a bivalent inactivated vaccine by injection has been shown to induce a strong systemic immune response against both bacterial infections.However,mucosal immune responses and protective efficiency induced by this inactivated vaccine administrated via immersion are yet to be investigated.We developed a bivalent vaccine containing formalin-inactivated A.veronii and E.ictaluri and evaluated the immune response in yellow catfish after immersion vaccination using body fluids biochemistry indices,agglutinating antibody titers,and the expression level of immune-related genes in the skin,gills,spleen,and head kidney.The activities of innate immune-related enzymes and specific agglutination antibody titers in body fluids,as well as the expression of innate and adaptive immune-related genes in both the mucosal and systemic tissues of vaccinated fish,were significantly higher than that in control fish.Next,we assessed the protective efficacy by a challenge model of virulent strains of E.ictaluri and A.veronii.The relative survival percent of vaccinated fish was 80%and 87%after challenging fish with E.ictaluri and A.veronii,respectively,which was higher than unvaccinated control fish(43%and 57%).These results confirm that the bivalent inactivated vaccine administered via immersion induces a strong mucosal immune response and confers good protection against both E.ictaluri and A.veronii.Our results also reinforce the notion that immersion vaccination could stimulate both mucosal and systemic immunity contributing to protection against pathogens.

Innate and adaptive immune responses in male and female reproductive tracts in homeostasis and following HIV infection

The male and female reproductive tracts are complex microenvironments that have diverse functional demands. The immune system in the reproductive tract has the demanding task of providing a protective environment for a fetal allograft while simultaneously conferring protection against potential pathogens. As such, it has evolved a unique set of adaptations, primarily under the influence of sex hormones, which make it distinct from other mucosal sites. Here, we discuss the various components of the immune system that are present in both the male and female reproductive tracts, including innate soluble factors and cells and humoral and cell-mediated adaptive immunity under homeostatic conditions. We review the evidence showing unique phenotypic and functional characteristics of immune cells and responses in the male and female reproductive tracts that exhibit compartmentalization from systemic immunity and discuss how these features are influenced by sex hormones. We also examine the interactions among the reproductive tract, sex hormones and immune responses following HIV-1 infection. An improved understanding of the unique characteristics of the male and female reproductive tracts will provide insights into improving clinical treatments of the immunological causes of infertility and the design of prophylactic interventions for the prevention of sexually transmitted infections.

Mucosal vaccine delivery:A focus on the breakthrough of specific barriers

Mucosal vaccines can effectively induce an immune response at the mucosal site and form the first line of defense against microbial invasion.The induced mucosal immunity includes the proliferation of effector T cells and the production of IgG and IgA antibodies,thereby effectively blocking microbial infection and transmis sion.However,after a long period of development,the transformation of mucosal vaccines into clinical use is still relatively slow.To date,fewer than ten mucosal vaccines have been approved.Only seven mucosal vaccines against coronavirus disease 2019(COVID-19) are under investigation in clinical trials.A representative vaccine is the adenovirus type-5 vectored COVID-19 vaccine(Ad5-nCoV) developed by Chen and coworkers,which is currently in phase Ⅲ clinical trials.The reason for the limited progress of mucosal vaccines may be the complicated mucosal barriers.Therefore,this review summarizes the characteristics of mucosal barriers and highlights strategies to overcome these barriers for effective mucosal vaccine delivery.