Elicitation Of Humoral Immune Responses Research Articles

Chemical cross-linking of HIV-1 Env for direct TLR7/8 ligand conjugation compromises recognition of conserved antigenic determinants

Covalent conjugation of immune-stimulatory compounds to protein antigens is a potential means to self-adjuvant non-replicating subunit vaccines. Previously, it was demonstrated that covalent coupling of a Toll-like receptor (TLR) ligand to the exterior HIV-1 envelope glycoprotein, gp120, enhanced its immunogenicity. However, the consequences of chemical conjugation to gp120 on broadly neutralizing antibody (bNAb) epitopes were so far not examined. Here, we conjugated a TLR7/8 ligand to lysine residues on gp120 using NHS-PEO8-maleimide linkers and investigated if this affected Ab recognition of the CD4 binding site (CD4bs), a highly conserved target for bNAbs. We demonstrate that the recognition of the CD4bs was reduced following coupling, especially at a higher coupling ratio. These results have implications for the coupling of ligands to vaccine antigens where elicitation of humoral immune responses to specific neutralizing determinants is desired.

Experimental Infection of Laying Hens with Salmonella enteritidis Strains that Express Different Types of Fimbriae

A study was conducted to compare the pathogenicity of three Salmonella enteritidis phage type 8 strains (9, 21, and 30) in 30-wk-old laying hens. Strain 9 expressed two types of fimbriae of 14 and 21 kDa. Strain 30 expressed a single fimbrial type (21 kDa). Strain 21 did not express any fimbrial protein. Laying hens were divided into three groups of 35 each and each group was orally inoculated with a single S. enteritidis strain (1 × 108 cfu per bird). Significantly less intensive cecal colonization and fecal shedding of the organism were observed in hens that were inoculated with the strain that did not express fimbriae than in birds inoculated with other two strains (P < 0.05). Isolation of S. enteritidis from liver, spleen, reproductive organs, and egg contents did not differ between groups. Mean serum S. enteritidis lipopolysaccharide-specific antibody titers of birds inoculated with strain 21 were lower than titers of hens that were inoculated with the other two strains from the 5th wk through the end of the trial. Immunoblot of the bacterial outer membrane structures revealed the presence of serum antibodies against lipopolysaccharide, membrane-associated proteins, and purified 14 kDa fimbrial protein in birds inoculated with strain 9 as late as 9 wk postinoculation. Results of this study are consistent with a role for fimbrial proteins in the cecal colonization by S. enteritidis. In addition, cecal colonization mediated by fimbrial proteins may enhance the elicitation of humoral immune response against S. enteritidis.

Examination of parameters affecting the elicitation of humoral immune responses by particle bombardment-mediated genetic immunization.

A human growth hormone expression construct was delivered intracellularly into the abdominal skin of mice by particle bombardment-mediated gene transfer. Using this technology, the in vivo delivery of antigen-encoding expression vectors affixed to gold microprojectiles results in de novo antigen production in target skin and development of specific antibody responses. In this study, we examined the contribution of various delivery parameters to the resultant protein expression and related antibody responses. The highest levels of both protein expression and antibody production were correlated with particle delivery to the epidermis while deliveries extending into the dermis resulted in decreased protein and antibody production. Optimal immune responses were also shown to be dependent upon the delivery of a sufficient number of DNA-coated gold particles, indicating that a dose-response relationship exists between the number of particles delivered and the resultant protein expression and antibody production. Further, maximal protein expression and associated antibody titers were elicited with surprisingly small amounts of DNA. The practicality of targeting skin and the use of three to four orders of magnitude less DNA than is typically required in direct DNA inoculation studies demonstrates the potential utility of this emerging technology for the rapid production of antibodies in laboratory animals, and in the development of a new class of human clinical vaccines based upon direct, intracellular DNA delivery.