Efficient Humoral and Cellular Immune Responses Induced by a Chimeric Virus-like Particle Displaying the Epitope of EV71 without Adjuvant

Objective To eliminate the side effects of aluminum adjuvant and His-tag,we constructed chimeric VLPs displaying the epitope of EV71（SP70） without His-tagged.Then evaluating whether the VLPs could efficiently evoke not only humoral but also cellular immune responses against EV71 without adjuvant.Methods The fusion protein was constructed by inserting SP70 into the MIR of truncated HBc Ag sequence,expressed in E.Coli,and purified through ion exchange chromatography and density gradient centrifugation.Mice were immunized with the VLPs and sera were collected afterwards.The specific antibody titers,Ig G subtypes and neutralizing efficacy were detected by ELISA,neutralization assay,and EV71 lethal challenge.IFN-γ and IL-4 secreted by splenocytes were tested by ELISPOT assay.Results HBc-SP70 proteins can self-assemble into empty VLPs.After immunization with HBc-SP70 VLPs,the detectable anti-EV71 antibodies were effective in neutralizing EV71 and protected newborn mice from EV71 lethal challenge.There was no significant difference for the immune efficacy whether the aluminum adjuvant was added or not.The specific Ig G subtypes were mainly IgG1 and IgG2 b and splenocytes from the mice immunized produced high levels of IFN-γ and IL-4.Conclusion The fusion proteins without His-tagged was expressed and purified as soluble chimeric HBc-SP70 VLPs without renaturation.In the absence of adjuvant,they were efficient to elicit high levels of Th1/Th2 mixed immune response as well as assisted by aluminum adjuvant.Furthermore,the chimeric VLPs have potential to prevent HBV and EV71 infection simultaneously.

DNA vaccine prime and replicating vaccinia vaccine boost induce robust humoral and cellular immune responses against MERS-CoV in mice

As of December 2022,2603 laboratory-identified Middle East respiratory syndrome coronavirus(MERS-CoV)infections and 935 associated deaths,with a mortality rate of 36%,had been reported to the World Health Organization(WHO).However,there are still no vaccines for MERS-CoV,which makes the prevention and control of MERS-CoV difficult.In this study,we generated two DNA vaccine candidates by integrating MERS-CoV Spike(S)gene into a replicating Vaccinia Tian Tan(VTT)vector.Compared to homologous immunization with either vaccine,mice immunized with DNA vaccine prime and VTT vaccine boost exhibited much stronger and durable humoral and cellular immune responses.The immunized mice produced robust binding antibodies and broad neutralizing antibodies against the EMC2012,England1 and KNIH strains of MERS-CoV.Prime-Boost immunization also induced strong MERS-S specific T cells responses,with high memory and poly-functional(CD107a-IFN-γ-TNF-α)effector CD8t T cells.In conclusion,the research demonstrated that DNA-Prime/VTT-Boost strategy could elicit robust and balanced humoral and cellular immune responses against MERS-CoV-S.This study not only provides a promising set of MERS-CoV vaccine candidates,but also proposes a heterologous sequential immunization strategy worthy of further development.

Functional identification of C-type lectin in the diamondback moth,Plutella xylostella(L.)innate immunity

C-type lectins(CTLs)are a superfamily of Ca^(2+)-dependent carbohydrate-recognition proteins,and an important pattern recognition receptor(PRR)in insect innate immunity which can mediate humoral and cellular immunity in insects.In this study,we report a novel dual carbohydrate-recognition domain(CRD)CTL from Plutella xylostella which we designate PxIML.PxIML is a protein with a 969 bp open reading frame(ORF)encoding 322 amino acids,containing a signal peptide and a dual-CRD with EPN(Glu_(124)-Pro_(125)-Asn_(126))and QPD(Gln_(274)-Pro_(275)-Asp_(276))motifs.The expression of PxIML mRNA in the fat body was significantly higher than in hemocytes and midgut.The relative expression levels of PxIML in the whole insect and the fat body were significantly inhibited after infection with Bacillus thuringiensis 8010(Bt8010)at 18 h,while they were significantly upregulated after infection with Serratia marcescens IAE6 or Pichia pastoris.The recombinant PxIML(rPxIML)protein could bind to the tested pathogen-associated molecular patterns(PAMPs),and the bacteria of Enterobacter sp.IAE5,S.marcescens IAE6,Staphylococcus aureus,Escherichia coli BL21,and Bt8010 in a Ca^(2+)-dependent manner,however,it showed limited binding to the fungus,P.pastoris.The rPxIML exhibited strong activity in the presence of Ca^(2+) to agglutinate Bt8010,Enterobacter sp.IAE5 and S.aureus,but it only weakly agglutinated with E.coli BL21,and could not agglutinate with S.marcescens IAE6 or P.pastoris.Furthermore,the rPxIML could bind to hemocytes,promote the adsorption of hemocytes to beads,and enhance the phenoloxidase(PO)activity and melanization of P.xylostella.Our results suggest that PxIML plays an important role in pathogen recognition and in mediating subsequent humoral and cellular immunity of P.xylostella.

Live and Inactivated Salmonella Enteritidis Vaccines:Immune Mechanisms in Broiler Breeders

Salmonella is a ubiquitous pathogen which, in addition to causing poultry diseases, has a growing zoonotic impact. It has demanded the implementation of diverse control strategies, in which vaccines play a major role. The understanding of the immune pathways elicited by the different vaccines is important, contributing for the establishment of strong immune correlates of protection, for instance. With the purpose of determining the dynamics of the humoral and cellular immune responses to vaccination, broiler breeders (Cobb Slow) were immunized with live or inactivated vaccines against Salmonella Enteritidis. Lymphocyte and macrophage subsets were analyzed in the peripheral blood by flow cytometry and antigen-specific circulating IgY and mucosal IgA were quantified. The markers analyzed by flow cytometry were CD8/CD28, CD4/TCRVβ1, Kul/ MHC II and Bu-1. Both live and inactivated vaccines induced an increase in the proportion of circulating monocytes (Kul+MHCII+) in some time points compared to non-vaccinated controls. However, whereas the live vaccine leads to an increase in CD8-CD28+ and Bu-1+ lymphocytescompared to the control group, the inactivated vaccine prompteda reduction in the percentage of severalleucocyte subsets (Kul-MHCII+, Bu-1+, CD8+CD28+, CD8-CD28+, CD4+TCRVβ1-, CD4+TCRVβ1+, CD4-TCRVβ1+) after the boost dose. Both vaccines induced specific serum IgY and mucosal IgA production;however, the inactivated vaccine stimulated higher titers in a shorter period. These results contribute to the understanding of mechanisms of action of live and inactivated Salmonella vaccines in chickens.