Characterization of a Novel Chimeric Theileria parva p67 Antigen Which Incorporates into Virus-like Particles and Is Highly Immunogenic in Mice.

Leah Whittle,Edward P Rybicki,Anna-Lise Williamson,Ros Chapman,Michiel Van Diepen

doi:10.3390/vaccines10020210

Abstract

The current method to protect cattle against East Coast Fever (ECF) involves the use of live Theileria parva sporozoites. Although this provides immunity, using live parasites has many disadvantages, such as contributing to the spread of ECF. Subunit vaccines based on the sporozoite surface protein p67 have been investigated as a replacement for the current method. In this study, two DNA vaccines expressing recombinant forms of p67 designed to display on retrovirus-like particles were constructed with the aim of improving immunogenicity. The native leader sequence was replaced with the human tissue plasminogen activator leader in both vaccines. The full-length p67 gene was included in the first DNA vaccine (p67); in the second, the transmembrane domain and cytoplasmic tail were replaced with those of an influenza A virus hemagglutinin 5 (p67HA). Immunofluorescent staining of fixed and live transfected mammalian cells showed that both p67 and p67HA were successfully expressed, and p67HA localised on the cell surface. Furthermore, p67HA was displayed on the surface of both bovine leukaemia virus (BLV) Gag and HIV-1 Gag virus-like particles (VLPs) made in the same cells. Mice vaccinated with DNA vaccines expressing p67 and p67HA alone, or p67HA with BLV or HIV-1 Gag, developed high titres of p67 and BLV Gag-binding antibodies. Here we show that it is possible to integrate a form of p67 containing all known antigenic domains into VLPs. This p67HA–VLP combination has the potential to be incorporated into a vaccine against ECF, as a DNA vaccine or as other vaccine platforms.

Highlights

Of all the tick-borne diseases affecting cattle in Africa, East Coast Fever (ECF) is considered one of the most concerning due to its severity and economic burden in the east and sub-Saharan regions
Except for a faint 110 kDa product, these larger proteins were absent for p67HA in the media, they were detected in the lysate
Our research aimed to improve the immunogenicity of p67 by displaying it on the surface of virus-like particles (VLPs). p67 was modified by replacing the transmembrane domain (TM) and cytoplasmic tails (CT) with the corresponding regions from the influenza H5N1 hemagglutinin A2 (HA2)

Summary

Introduction

Of all the tick-borne diseases affecting cattle in Africa, East Coast Fever (ECF) is considered one of the most concerning due to its severity and economic burden in the east and sub-Saharan regions. The disease affects 12 countries and can have high incidence and mortality rates; regions in Uganda have case fatality rates of up to 89.5% [1,2]. The venerable infection and treatment method (ITM) is the current vaccination regime against ECF: cattle are infected with live T. parva sporozoites and treated immediately afterwards with long-acting oxytetracycline [10]. This provides effective protection but has many disadvantages: these include the use of cattle, rabbits and ticks for the generation and extensive quality control of vaccine sporozoites; transport of live parasites in liquid nitrogen, which requires a cold chain, and the fact that the vaccine is lethal if the appropriate antibiotic dosage is not administered [2,11]. ITM-vaccinated cattle become T. parva carriers, which can spread the parasite to unvaccinated animals and introduce ECF into previously naïve regions [12,13]

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Results

Conclusion