Bovine Adenovirus-3 Tropism for Bovine Leukocyte Sub-Populations.

Sugandhika Khosa,Philip Griebel,Natasa Arsic,Maria Bravo Araya,Suresh K Tikoo

doi:10.3390/v12121431

Abstract

A number of characteristics including lack of virulence and the ability to grow to high titers, have made bovine adenovirus-3 (BAdV-3) a vector of choice for further development as a vaccine-delivery vehicle for cattle. Despite the importance of blood leukocytes, including dendritic cells (DC), in the induction of protective immune responses, little is known about the interaction between BAdV-3 and bovine blood leukocytes. Here, we demonstrate that compared to other leukocytes, bovine blood monocytes and neutrophils are significantly transduced by BAdV404a (BAdV-3, expressing enhanced yellow green fluorescent protein [EYFP]) at a MOI of 1–5 without a significant difference in the mean fluorescence of EYFP expression. Moreover, though expression of some BAdV-3-specific proteins was observed, no progeny virions were detected in the transduced monocytes or neutrophils. Interestingly, addition of the “RGD” motif at the C-terminus of BAdV-3 minor capsid protein pIX (BAV888) enhanced the ability of the virus to enter the monocytes without altering the tropism of BAdV-3. The increased uptake of BAV888 by monocytes was associated with a significant increase in viral genome copies and the abundance of EYFP and BAdV-3 19K transcripts compared to BAdV404a-transduced monocytes. Our results suggest that BAdV-3 efficiently transduces monocytes and neutrophils in the absence of viral replication. Moreover, RGD-modified capsid significantly increases vector uptake without affecting the initial interaction with monocytes.

Highlights

Adenoviruses are double-stranded DNA viruses, which offer several advantages as vaccine-delivery vectors in terms of efficacy, safety, and stability [1]
The percentage of virus-transduced peripheral blood mononuclear cells (PBMCs) was determined based on a detectable increase in mean fluorescence intensity (MFI) when comparing infected versus mock-infected cells
We investigated whether the addition of an “RGD” motif would alter the leukocyte tropism of BAV304a with plasmid pUC304a-CATRGD DNA produced cytopathic effect (CPE) in 15–20 days

Summary

Introduction

Adenoviruses are double-stranded DNA viruses, which offer several advantages as vaccine-delivery vectors in terms of efficacy, safety, and stability [1]. Adenoviruses have been used to deliver vaccine antigens to cattle [1], we have focused on developing species-specific adenoviruses as vaccine-delivery vehicles [3]. Molecular characterization of bovine adenovirus 3 (BAdV-3) [4] led to the development of BAdV-3 as a vaccine vector for immunizing cattle [5,6,7,8]. Two immunizations (prime and boost) with a BAdV-3-vectored vaccine induced protective immunity in calves [9], an ideal. BAdV-3-vectored vaccine would induce protection following a single immunization [6] to avoid vaccine interference by acquired immune responses to the vector.

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Results

Conclusion