Identification of equine herpesvirus-1 antigens recognized by cytotoxic T lymphocytes.

This research investigates equine herpesvirus-1 (EHV-1) antigens that can be recognized by cytotoxic T lymphocytes (CTLs), with the goal of potentially developing a multi-epitope EHV-1 vaccine.

Introduction

• Equine herpesvirus-1 (EHV-1) is a serious disease affecting horses all over the world, even in cases where vaccines have been frequently used.
• It has been hypothesized that cytotoxic T lymphocytes (CTLs), a type of immune cell, are key to protecting against initial and recurring latent EHV-1 infections.
• However, the antigen-specificity, or the ability of these CTLs to recognize and bind to specific antigens of EHV-1, is currently unknown.
• The objective of the research was to identify EHV-1 genes encoding proteins that contain CTL epitopes (regions of a protein that antibodies recognize and to which they bind), and to determine the genes’ Major Histocompatibility Complex class I (MHC I) restriction. In horses, this is known as ELA-A.

Methodology

• Researchers used equine dendritic cells, which were transfected (genetically modified) with various EHV-1 genes.
• These cells were used to stimulate CTL precursor populations derived from horses previously infected with EHV-1.
• They then measured cytotoxicity (cell-killing capacity) against EHV-1 infected PWM lymphoblast targets. Lymphoblasts are immature cells that can develop into lymphocytes.
• Positive controls were dendritic cells infected with EHV-1. A range of genes encoding different EHV-1 proteins were transfected into dendritic cells using the PowderJect XR-1 research device.

Results

• Dendritic cells transfected with the immediate-early (IE) gene induced CTL responses in four out of six ponies tested.
• All four of these ponies had a shared ELA-A3.1 haplotype, which is a set of genes within an organism that were inherited together from a single parent.
• Dendritic cells transfected with gC, gD, gI and gL glycoproteins also induced CTLs in individual ponies.
• The cytotoxic activity was ELA-A-restricted, meaning it was specific to the haplotype. Heterologous targets from ELA-A mismatched ponies were not killed and an MHC I blocking antibody reduced EHV-1-specific killing.
• This research marks the first identification of an EHV-1 protein containing ELA-A-restricted CTL epitopes.

Conclusion

• These findings can now be used to study CTL specificity for EHV-1 proteins in horses with a broad range of ELA-A haplotypes.
• Overall, the aim is to apply these understandings in the development of a multi-epitope EHV-1 vaccine that could potentially offer a stronger and more targeted protection against this serious equine disease.