The use of convalescent sera in immune-electron microscopy to detect non-suspected/new viral agents.

Antonio Lavazza,Monica Cerioli,Cristiana Tittarelli

doi:10.3390/v7052683

Abstract

Negative staining electron microscopy methods can be employed for the diagnosis of viral particles in animal samples. In fact, negative staining electron microscopy methods are used to identify viruses, especially in minor species and wild animals, when no other methods are available and in cases of rare, emerging or re-emerging infections. In particular, immune-electron-microscopy with convalescent sera is employed to detect etiological agents when there are undiagnosed clinical outbreaks, when alternative diagnostic methods fail due to the lack of immunological reagents and primers, and when there is no indicative clinical suspect. An overview of immune-electron-microscopy with convalescent sera’s use in the diagnosis of new and unsuspected viruses in animals of domestic and wild species is provided through the descriptions of the following four diagnostic veterinary cases: (I) enteric viruses of pigs: Porcine Rotavirus, Porcine Epidemic Diarrhea Virus, Porcine Circovirus and Porcine Torovirus; (II) Rotavirus and astrovirus in young turkeys with enteritis; (III) Parvovirus-like particles in pheasants; and (IV) Lagoviruses: Rabbit Hemorrhagic Disease Virus and European Brown Hare Syndrome Virus.

Highlights

In the last thirty years, the use of negative staining electron microscopy methods, and immune-electron microscopy (IEM), has permitted the detection and identification of different viral particles in samples from several animal species
Some field cases of diagnosing animal diseases are representative of the results obtained by immuno-aggregation electron microscopy (IAEM) using convalescent sera to detect “new” and emerging viruses, and mixed viral infections and non-cultivable viruses
In the subsequent paragraphs we describe the detection of viruses in clinical outbreaks pertaining to different species: enteritis in pigs and turkeys, and hepatitis in pheasant, rabbits and hares

Summary

Introduction

In the last thirty years, the use of negative staining electron microscopy methods (ns-EM), and immune-electron microscopy (IEM), has permitted the detection and identification of different viral particles in samples from several animal species. In addition to the primary serum’s induction of aggregates and clumps of virions, a secondary step to improve the detection of virus-antibody complexes may be added. The combined techniques, commonly defined as IEM-gold methods, may employ as the “detector” either Protein A or G-gold conjugates that can bind the antibody heavy chains of several species or even secondary anti-species antibodies to which colloidal gold particles have been electrostatically adsorbed [5,6]

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Conclusion