Priming Efficacy Research Articles

Differential sensitivities of primary and secondary T cell responses to antigen structure

Here we examined T cell responses to two analogs of a chimeric peptide encoding a known B and a known T cell epitope. In one of the analogs, the B cell epitope existed in a random conformation whereas it was restricted within a disulfide-bonded cyclic loop in the other. Immunization of these peptides in mice revealed that the latter peptide was significantly poorer at priming T cells and our preliminary results suggest this could be the result of differential processing of the two analogs. While primary T cell responses were sensitive to the influence of conformation, secondary responses were not discriminatory for the two antigens confirming the differences in activation requirements for primary and secondary T cell responses. Further, our studies also suggest that the priming efficacy of a T cell epitope is influenced by its structural environment.

Host Priming, Not Target Antigen Type, Decides Rejection Rate in Mice Primed with MHC II “Knockout” Cultured Keratinocytes

Background.Lack of skin for autograft continues to be problematic in patients with large burns. Allograft and xenograft have been used, but are prone to rapid rejection. Use of cultured keratinocytes (CK) and major histocompatibility complex (MHC) II “knockout” grafts leads to prolonged graft survival compared to allograft. Whether this prolongation is secondary to decreased priming efficacy or target recognition is unknown. Whether a combination of these techniques would generate a less immunogenic allograft remains to be determined.Methods.CBA mice (n= 100) were flank-grafted with full thickness C57BL/6 (B6 FT), B6 cultured keratinocytes (B6 CK), B6 major histocompatibility complex II “knockout” full thickness (KO II FT), B6 major histocompatibility complex II “knockout” cultured keratinocytes (KO II CK), or a full thickness autograft (Auto). Three weeks after priming flank grafting, B6, MHC I (KO I), and KO II full thickness tail grafts were placed on each mouse. Tail graft rejection was assessed daily by an observer blinded to flank and tailgraft type. A 4-point grading system for graft color, hair loss, and texture was used.Results.Animals primed with KO II CK flank grafts had increased survival of tail grafts over B6 FT flank grafted controls (12.3 ± 1.05 vs 10.1 ± 1.00,P< 0.05). Within flank graft groups, however, B6, KO I, and KO II tail graft survival was similar.Conclusions.KO II CK allografts decrease host priming compared to normal B6 FT allograft. MHC deletion (KO I or KO II) does not protect a target graft from rejection in a primed host. CK and KO techniques may offer a less immunogenic allograft and a readily available source of wound coverage in patients with extensive burns.

Priming for virus-specific CD8+ but not CD4+ cytotoxic T lymphocytes with synthetic lipopeptide is influenced by acylation units and liposome encapsulation

Synthetic peptides of the herpes simplex virus glycoprotein B synthesized either as a free form or derivatized with one (PAM1) or three palmitic acids (PAM3Cys) were used to assess the in vivo priming efficacy of high affinity virus-specific CTL induction. The peptide and its derivatives were delivered in vivo with or without liposome encapsulation. Neither the free peptide nor the PAM1 derivative primed for high affinity virus specific CD8+ CTL induction, whether delivered via liposomes or not. On the other hand, the PAM3Cys derivative was able to prime for low levels of high affinity virus specific CD8+ CTL induction in the absence of liposome encapsultion. However, the efficiency of virus-specific CD8+ CTL induction with PAM3Cys derivative was enhanced following encapsulation in the liposomes. In contrast, all forms of the peptides induced both CD4+ T cell proliferative response as well as high affinity virus-specific CD4+ CTL. In addition, the efficiency of the PAM3Cys derivative to prime for CD4+ or CD8+ CTL was found to be influenced by the liposome encapsulation. When delivered via liposomes, the PAM3Cys derivative effectively primed for CD8+ CTL. However, liposomal delivery was not necessary for efficient priming for CD4+ CTL induction. Thus, both the acylation units as well as liposomal delivery appear to influence the in vivo priming of CD4+ and CD8+ T cell responses with synthetic peptides.

Effect of growth factors on Escherichia coli alpha-hemolysin-induced mediator release from human inflammatory cells: involvement of the signal transduction pathway.

Previously, we have shown that Escherichia coli alpha-hemolysin represents a potent stimulus for inflammatory mediator release (O2- release, beta-glucuronidase release, and leukotriene generation) from human polymorphonuclear granulocytes (PMN) as well as for histamine release from a human lymphocyte-monocyte-basophil cell suspension (LMB). In contrast, the E. coli alpha-hemolysin leads to a downregulation of cytokine release (interleukin 6 [IL-6], tumor necrosis factor alpha, and IL-1 beta) from human LMB. This study was undertaken (i) to analyze the priming efficacy of growth factors (granulocyte-macrophage colony-stimulating factor [GM-CSF] and granulocyte CSF [G-CSF]) on inflammatory mediator release from human PMN and LMB challenged with hemolysin-producing E. coli bacteria as well as with cell-free E. coli alpha-hemolysin and (ii) to identify major components involved in GM-CSF and G-CSF priming. GM-CSF pretreatment led to an increased chemiluminescence response from human PMN by up to 100%, leukotriene B4 generation was enhanced up to fivefold, and histamine release from human LMB increased from 45% +/- 15% to 75% +/- 5% (mean +/- standard distribution) of the total histamine content. G-CSF priming induced an increase in the chemiluminescence response by up to 50% +/- 5% from human PMN and an increase in histamine release from human LMB by 20% +/- 5%. The growth factors, GM-CSF and G-CSF, modulated neither beta-glucuronidase release from human PMN nor IL-8 release from human PMN and LMB challenged with the E. coli alpha-hemolysin. GM-CSF and G-CSF pretreatment increased the fluoride (NaF)-induced chemiluminescence response by up to 10-fold; the serine/threonine phosphatase inhibitor okadaic acid inhibited GM-CSF- and G-CSF-induced priming. NaF-induced histamine release was enhanced up to 60 and 30% by GM-CSF and G-CSF priming, respectively. GM-CSF and G-CSF pretreatment did not modulate phorbol 12-myristate 13-acetate-induced chemiluminescence response or histamine release. GM-CSF by itself induced an increase in 5-lipoxygenase-specific mRNA expression within 5 min. Our results indicate that (i) GM-CSF and G-CSF interact with inflammatory cells via distinct cellular signalling, (ii) the signal transduction pathway is dependent on the cellular mediator, and (iii) the use of growth factors may be a potent tool to influence the clinical outcome in infectious diseases.

Selective breeding for acoustic priming

Data on eight generations of selective breeding for acoustic priming efficacy are reported. The realized heritability of this trait is approximately 0.2-0.3, indicating that the trait is determined in part by genetic factors. Animals selectively bred for acoustic priming do not differ in terms of first-trial (i.e., non-priming-induced) audiogenic seizures. These data suggest that acoustic priming and first-trial audiogenic seizures are controlled by different genetic mechanisms.