A dominant V beta bias in the CTL response after HSV-1 infection is determined by peptide residues predicted to also interact with the TCR beta-chain CDR3

Immune Response Elicited by Recombinant Adenovirus-Delivered Glycoprotein B and Nucleocapsid Protein UL18 and UL25 of HSV-1 in Mice

Due to the complex pathogenic and immune escape mechanisms of herpes simplex virus type 1 (HSV-1), especially the failure of induced immune responses to block the initial cell-to-cell transmission of the virus from skin cells to neurons, the body struggles to establish effective prevention and control methods, resulting in the failure of currently developed vaccines. Previous studies have highlighted the crucial roles of surface glycoproteins and nucleocapsid proteins in activating the body's immune defense system against HSV-1 infection. In this study, recombinant adenoviruses were used as vectors to generate adenoviruses carrying the nucleocapsid protein genes UL18 and UL25, as well as the surface glycoprotein gene gB. This approach aimed to mimic the protein expression process that occurs following viral infection of the host and to investigate the immune response characteristics induced by UL18, UL25, and gB proteins. The findings revealed that UL18, UL25, and gB proteins could all trigger the expression of genes associated with innate immune responses; however, the specific genes induced varied in type and level. Furthermore, all three proteins were capable of promoting the proliferation of CD8+ T cells in the lymph nodes. Notably, only UL18 and gB could elicit a Th1 cell immune response. Interestingly, among these proteins, only UL18 could also induce a relatively higher IL-4 level, indicating a Th2 cell immune response. In addition to cellular immunity, all three proteins stimulated the production of specific IgG antibodies. Notably, UL18 induced higher and more sustained levels of specific IgG antibodies in mice. By contrast, only glycoprotein gB induced lower levels of neutralizing antibodies in mice. Moreover, when these mice were challenged with HSV-1, the co-immunization with UL18 and gB provided better protection than gB alone. In conclusion, HSV-1 surface glycoproteins and nucleocapsid proteins exhibit differences in their ability to induce innate and adaptive immunity in the body, suggesting potential avenues for vaccine design by leveraging their complementary advantages.

Expressing Redundancy among Linear-Epitope Sequence Data Based on Residue-Level Physicochemical Similarity in the Context of Antigenic Cross-Reaction

Epitope-based design of vaccines, immunotherapeutics, and immunodiagnostics is complicated by structural changes that radically alter immunological outcomes. This is obscured by expressing redundancy among linear-epitope data as fractional sequence-alignment identity, which fails to account for potentially drastic loss of binding affinity due to single-residue substitutions even where these might be considered conservative in the context of classical sequence analysis. From the perspective of immune function based on molecular recognition of epitopes, functional redundancy of epitope data (FRED) thus may be defined in a biologically more meaningful way based on residue-level physicochemical similarity in the context of antigenic cross-reaction, with functional similarity between epitopes expressed as the Shannon information entropy for differential epitope binding. Such similarity may be estimated in terms of structural differences between an immunogen epitope and an antigen epitope with reference to an idealized binding site of high complementarity to the immunogen epitope, by analogy between protein folding and ligand-receptor binding; but this underestimates potential for cross-reactivity, suggesting that epitope-binding site complementarity is typically suboptimal as regards immunologic specificity. The apparently suboptimal complementarity may reflect a tradeoff to attain optimal immune function that favors generation of immune-system components each having potential for cross-reactivity with a variety of epitopes.

Diversity of the CD8+ T cell repertoire elicited against an immunodominant epitope does not depend on the context of infection

The diversity of the pathogen-specific T cell repertoire is believed to be important in allowing recognition of different pathogen epitopes and their variants and thereby reducing the opportunities for mutation-driven pathogen escape. However, the extent to which the TCR repertoire can be manipulated by different vaccine strategies so as to obtain broad diversity and optimal protection is incompletely understood. We have investigated the influence of the infectious/inflammatory context on the TCR diversity of the CD8(+) T cell response specific for the immunodominant epitope in C57BL/6 mice, derived from glycoprotein B of HSV-1. To that effect, we compared TCR V segment utilization, CDR3 length, and sequence diversity of the response to natural HSV-1 infection with those elicited by either Listeria monocytogenes or vaccinia virus expressing the immunodominant epitope in C57BL/6 mice. We demonstrate that although the type of infection in which the epitope was encountered can influence the magnitude of the CD8(+) T cell responses, TCR beta-chain repertoires did not significantly differ among the three infections. These results suggest that widely different live vaccine vectors may have little impact upon the diversity of the induced CTL response, which has important implications for the design of live CTL vaccine strategies against acute and chronic infections.

Reevaluating the CD8 T-cell response to herpes simplex virus type 1: involvement of CD8 T cells reactive to subdominant epitopes

In C57BL/6 (B6) mice, most herpes simplex virus (HSV)-specific CD8 T cells recognize a strongly immunodominant epitope on glycoprotein B (gB498) and can inhibit HSV type 1 (HSV-1) reactivation from latency in trigeminal ganglia (TG). However, half of the CD8 T cells retained in latently infected TG of B6 mice are not gB498 specific and have been largely ignored. The following observations from our current study indicate that these gB498-nonspecific CD8 T cells are HSV specific and may contribute to the control of HSV-1 latency. First, following corneal infection, OVA257-specific OT-1 CD8 T cells do not infiltrate the infected TG unless mice are simultaneously immunized with OVA257 peptide, and then they are not retained. Second, 30% of CD8 T cells in acutely infected TG that produce gamma interferon in response to HSV-1 stimulation directly ex vivo are gB498 nonspecific, and these cells maintain an activation phenotype during viral latency. Finally, gB498-nonspecific CD8 T cells are expanded in ex vivo cultures of latently infected TG and inhibit HSV-1 reactivation from latency in the absence of gB498-specific CD8 T cells. We conclude that many of the CD8 T cells that infiltrate and are retained in infected TG are HSV specific and potentially contribute to maintenance of HSV-1 latency. Identification of the viral proteins recognized by these cells will contribute to a better understanding of the dynamics of HSV-1 latency.

Diversity of escape variant mutations in Simian virus 40 large tumor antigen (SV40 Tag) epitopes selected by cytotoxic T lymphocyte (CTL) clones

To better understand the relationship between epitope variation and tumor escape from immune surveillance, SV40 T antigen-transformed B6/K-0 cells were subjected to selection with individual CTL clones specific for the SV40 T antigen H-2D(b)-restricted epitopes I or V. CTL-resistant populations were isolated from a majority of the selection cultures and substituted epitope sequences were identified within most of the resistant populations. Tag sequences deleted of all or portions of the selection-targeted epitope were identified, but in lower numbers compared to epitope sequences bearing single residue substitutions. Relatively few flanking residue substitutions were identified, and only in epitope I-targeted selections. The diversity (numbers and epitope residue locations) of substituted epitope residue positions varied between selections. These findings suggest that the scope of spontaneously occurring mutations that could allow for escape from individual CD8+ T cell clones is large.

Structural determinants of T-cell receptor bias in immunity

Antigen-specific T-cell responses induced by infection, transplantation, autoimmunity or hypersensitivity are characterized by cells expressing biased profiles of T-cell receptors (TCRs) that are selected from a diverse, naive repertoire. Here, we review the evidence for these TCR biases, focusing on crystallographic analysis of the structural constraints that determine the binding of a TCR to its ligand and the persistence of certain TCRs in an immune repertoire. We discuss the ways in which diversity in a selected TCR repertoire can contribute to protective immunity and the implications of this for vaccine design and immunotherapy.

The many important facets of T-cell repertoire diversity

In the thymus, a diverse and polymorphic T-cell repertoire is generated by random recombination of discrete T-cell receptor (TCR)-alphabeta gene segments. This repertoire is then shaped by intrathymic selection events to generate a peripheral T-cell pool of self-MHC restricted, non-autoaggressive T cells. It has long been postulated that some optimal level of TCR diversity allows efficient protection against pathogens. This article focuses on several recent advances that address the required diversity for the generation of an optimal immune response.

Direct link between mhc polymorphism, T cell avidity, and diversity in immune defense

Major histocompatibility complex (mhc)-encoded molecules govern immune responses by presenting antigenic peptides to T cells. The extensive polymorphism of genes encoding these molecules is believed to enhance immune defense by broadening the array of antigenic peptides available for T cell recognition, but direct evidence supporting the importance of this mechanism in combating pathogens is limited. Here we link mhc polymorphism-driven diversification of the cytotoxic T lymphocyte (CTL) repertoire to the generation of high-avidity, protective antiviral T cells and to superior antiviral defense. Thus, much of the beneficial effect of the mhc polymorphism in immune defense may be due to its critical influence on the properties of the selected CTL repertoire.