Adenovirus infections

Previous authors: G R THOMSON

Current authors:
S K TIKOO - Professor and Research Fellow, School of Public Health\VIDO-InterVac, Director, Vaccinology & Immunotherapeutics Program, University of Saskatchewan, Saskatoon, SK, Canada
T A WOLDEMARIAM - PhD Candidate, Veterinary Microbiology, University of Saskatchewan, Saskatoon, SK, Canada
V K MANOHARAN - Post-doctoral Fellow, VIDO-INTERVAC, University of Saskatchewan, 120 Veterinary Road, Saskatchewan, Canada
S M P KULANAYAKE - PhD candidate, Vaccinology & Immunotherapeutics Program University of Saskatchewan, Saskatoon, SK, Canada

GENERAL INTRODUCTION: ADENOVIRIDAE

Introduction

Since the first isolation of adenovirus in humans by Enders et al (1956),⁴⁵ adenoviruses have been isolated from mammals, birds, reptiles including turtles, and fish,  which are mainly involved in mild clinical infections. Among the major domestic livestock species, adenovirus infections have been diagnosed in cattle, sheep, goats, pigs and horses.

It is probable that all vertebrates have one or more adenoviruses with which they co-evolved so only a few cause disease in their natural hosts. Most adenoviruses are associated with the upper respiratory or digestive tracts of their hosts and, in some cases infection may be prolonged, apparently as part of a transmission strategy. Well-known exceptions in respect of pathogenicity in domestic animals are the viruses that cause infectious canine hepatitis and contribute to the kennel cough syndrome.

Apart from equine mastadenovirus 1 and 2 infection of Arabian foals suffering from severe combined immune deficiency, no clearly defined disease syndrome of livestock, other than poultry, has been shown unequivocally to be caused by an adenovirus. Adenoviruses are, however, common in children and people suffering from immune deficiencies, such as those resulting from chemotherapy following organ transplantation or due to human immunodeficiency virus infection.

Adenoviruses have been used for many decades to research fundamental phenomena in the field of virology, i.e. for academic research. That, among other things, led to the discovery that adenoviruses are able to cause tumours in newborn rodents. However, this does not occur in natural hosts. More recently there has been research into use of adenoviruses to construct recombinant viruses for use as vaccines against other viral infections, e.g. foot and mouth disease.

Adeno-associated viruses (AAVs) are parvoviruses classified in the genus Dependovirus, dependent on co-infection of cells with an adenovirus in order to be able to replicate. These viruses have been identified in humans, cattle, sheep, horses, dogs and birds. However, no AVV has so far been associated with disease.

For more information on the classification and general characteristic on adenoviruses the General Introduction: Adenoviridae should be consulted.

Adenovirus infections of cattle

Introduction

Adenovirus infections of cattle probably occur universally and most infections are subclinical. Since its first isolation from faecal samples of a cow in USA,⁶³ bovine adenoviruses (BAdVs) have been isolated from healthy and sick calves suffering from diarrhoea and/or respiratory disease.¹²⁸ Depending on the serotype of the virus, it can cause a variety of clinical signs, including pneumonia, diarrhoea, conjunctivitis and polyarthritis in young animals. Though BAdV infections have been associated with a variety of respiratory and alimentary tract diseases, their role in the causation of these diseases remains uncertain. At present, 11 known BAdV serotypes are classified into two genera, namely Mastadenovirus (BAdV-1,2,3,9 and 10) and Atadenovirus (BAdV-4,5,6,7,8 and strain Rus).⁷⁵

Aetiology

For more information on the characteristics of adenoviruses the General Introduction: Adenoviridae should be consulted

The best characterized serotype is BAdV-3.³ The genome of BAdV-3 is divided into E, I and L regions. Structural proteins are encoded by E2 (terminal protein ), I (pIX, IVa2) and L (hexon, penton, fiber, IIIa, VI, VIII, IX, V, VII, Mu, TP,  protease) regions. The nonstructural proteins are encoded by E (E1, E3 and E4), E2 (DNA binding protein; RNA polymerase II) and L (52K, 100K, 33K, 22K) regions.^{3, 106}

Although intitial attachment of BAdV-3 to host cells involves interaction of the knob region of penton fibres with sialic acid attached to 97 kDa and 34 kDa cellular proteins,⁷⁹ the existence of secondary interaction of penton fibres with cellular receptors is not clear. Following internalization of virus capsid containing genome into endosomes, the infectious BAdV-3 are produced as described in the General Introduction: Adenoviridae.

Epidemiology

About  25 to 87 per cent of cattle sera are positive for BAdV  antibodies, indicating high prevalence rates of infection in different geographic locations and in various sex and age groups. It is therefore safe to presume that infections with adenoviruses are widespread in cattle populations.^{20, 22, 77, 117, 126} For example, 76 and 59 per cent of calf sera collected at two Austrian abattoirs had virus neutralizing antibodies against selected serotypes.^{20, 89} In a group of 29 heifers monitored serologically in Idaho, USA, from birth to 24 months of age, there were 28 BAdV- 3 and 33 BAdV- 7 infections, some of which occurred in the face of maternally-derived antibody.¹¹⁷ Asymptomatic cattle populations have...