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Advances in Circoviruses

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A special issue of Pathogens (ISSN 2076-0817). This special issue belongs to the section "Viral Pathogens".

Deadline for manuscript submissions: closed (31 March 2022) | Viewed by 16556

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Special Issue Editors

Prof. Michele Drigo

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Guest Editor

Department Animal Medicine, Production and Health (MAPS), University of Padova, Padova, Italy
Interests: swine infectious diseases and epidemiology; viral pathogens; circoviruses
Special Issues, Collections and Topics in MDPI journals

Dr. Giovanni Franzo

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Guest Editor

Department of Animal Medicine, Production and Health (MAPS), University of Padua, 35020 Legnaro, Italy
Interests: avian viruses; molecular epidemiology; phylogenetics; phylodynamics; statistics; molecular diagnosis; vaccination
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Circoviruses are a heterogeneous viral group infecting several animals hosts. Currently, research has largely focused on a limited number of avian and porcine circoviruses species, porcine circovirus 2 (PCV-2) in particular, because of their clinical and economic relevance. The improvements in diagnostic techniques and sequencing technologies have led to the discovery of a multitude of other viral species in different hosts. However, the knowledge of the distribution, epidemiology, infectious cycle, and potential pathogenesis of these newly discovered viruses is essentially lacking. Although the clinical relevance seems negligible in most cases, the multifactorial nature of these infections cannot be overemphasized: nowadays, devastating circovirus diseases mostly emerge when changes in farming conditions allow them to evolve from subclinical infections to posing a significant threat to animal health and productivity. Therefore, other circoviruses may represent a menace to companion animal and livestock welfare and/or wildlife conservation, thus requiring more extensive and dedicated studies.

Several aspects regarding infection dynamics, pathogenesis, and immunity also remain elusive for economically relevant and widely studied species like PCV-2 and the recently discovered PCV-3, demonstrating the complexity of these only apparently simple viruses.

For these reasons, this Special Issue welcomes any study providing a substantial advancement in circovirus knowledge, with a particular focus on, but not limited to, new species discovery, genomics, epidemiology and ecologic implications, biological cycle, virus–host interactions, pathogenesis, immunity, and disease control.

Prof. Michele Drigo
Dr. Giovanni Franzo
Guest Editors

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Keywords

circoviruses
epidemiology
immunopathogenesis
vaccination

Published Papers (7 papers)

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Research

10 pages, 782 KiB

Open AccessArticle

Cross-Sectional Study on the Prevalence of PCV Types 2 and 3 DNA in Suckling Piglets Compared to Grow–Finish Pigs in Downstream Production

by Matthias Eddicks, Roland Maurer, Pauline Deffner, Lina Eddicks, Wolfgang Sipos, Sven Reese, Vojislav Cvjetković, Roman Krejci, Tanja Opriessnig, Mathias Ritzmann and Robert Fux

Pathogens 2022, 11(6), 671; https://doi.org/10.3390/pathogens11060671 - 10 Jun 2022

Cited by 3 | Viewed by 2025

Abstract

Vertical transmission is a consistently discussed pathway of porcine circovirus type 2 (PCV2) and porcine circovirus type 3 (PCV3) transmission in pigs. To evaluate the presence of PCV2 and PCV3 in piglets, we collected tissue samples from 185 piglets that were crushed within the first week of life from 16 farms located in Germany and Austria. Pooled samples consisting of thymus, inguinal lymph node, myocardium, lung and spleen were examined for PCV2 and PCV3 by qPCR. Furthermore, oral fluid samples (OFS) from grow–finish pigs were collected and examined the same way. In piglets, PCV2 was highly prevalent (litters: 69.4%; piglets: 61.6%), whereas PCV3 prevalence was low (litters: 13.4%; piglets: 13.0%). In total, 72.6% and 67.2% of all collected OFS were PCV2 or PCV3 positive, respectively. Sow vaccination against PCV2 was identified as a protective factor concerning PCV2 in piglets (OR: 0.279; CI: 0.134–0.578; p < 0.001), whereas the porcine reproductive and respiratory syndrome virus (PRRSV) vaccination of sows was identified as a protective factor concerning PCV3 in piglets (OR: 0.252 CI: 0.104–0.610; p = 0.002). Our results show that PCV2, but not PCV3, is ubiquitous in suckling piglets and that early PCV3 infections might be modulated by PRRSV–PCV3 interaction. However, the ubiquitous nature of both viruses in older pigs could be confirmed. Full article

(This article belongs to the Special Issue Advances in Circoviruses)

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15 pages, 3886 KiB

Open AccessArticle

Colorimetric Kit for Rapid Porcine Circovirus 2 (PCV-2) Diagnosis

by Caroline Rodrigues Basso, Ana Carolina Yamakawa, Taís Fukuta Cruz, Valber Albuquerque Pedrosa, Massimiliano Magro, Fabio Vianello and João Pessoa Araújo Júnior

Pathogens 2022, 11(5), 570; https://doi.org/10.3390/pathogens11050570 - 12 May 2022

Cited by 1 | Viewed by 1876

Abstract

The aim of the current study is to present a low-cost and easy-to-interpret colorimetric kit used to diagnose porcine circovirus 2 (PCV-2) to the naked eye, without any specific equipment. The aforementioned kit used as base hybrid nanoparticles resulting from the merge of surface active maghemite nanoparticles and gold nanoparticles, based on the deposition of specific PCV-2 antibodies on their surface through covalent bonds. In total, 10 negative and 40 positive samples (≥10² DNA copies/µL of serum) confirmed by qPCR technique were tested. PCV-1 virus, adenovirus, and parvovirus samples were tested as interferents to rule out likely false-positive results. Positive samples showed purple color when they were added to the complex, whereas negative samples showed red color; they were visible to the naked eye. The entire color-change process took place approximately 1 min after the analyzed samples were added to the complex. They were tested at different dilutions, namely pure, 1:10, 1:100, 1:1000, and 1:10,000. Localized surface plasmon resonance (LSPR) and transmission electron microscopy (TEM) images were generated to validate the experiment. This new real-time PCV-2 diagnostic methodology emerged as simple and economic alternative to traditional tests since the final price of the kit is USD 4.00. Full article

(This article belongs to the Special Issue Advances in Circoviruses)

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Graphical abstract

8 pages, 3117 KiB

Open AccessCommunication

Whole-Genome Analysis of Porcine Circovirus Type 2 in Russia

by Sergei Raev, Anton Yuzhakov and Taras Aliper

Pathogens 2021, 10(12), 1631; https://doi.org/10.3390/pathogens10121631 - 16 Dec 2021

Cited by 3 | Viewed by 2688

Abstract

Porcine circovirus type 2 (PCV2) is the causative agent of porcine circovirus-associated diseases (PCVAD) that bring about significant economic losses in the pig industry all over the world. The aim of this study was to investigate the genetic diversity of PCV2 in Russia and characterize the available complete genome sequences. PCV2 DNA was detected at all investigated farms located in different regions of Russia. Whole-genome analysis demonstrated that the majority of PCV2 strains belonged to genotype PCV2d (12 out of 14), while PCV2a and PCV2b were only detected at 2 farms (one at each). Further analysis revealed that all antibody recognition sites in Russian PCV2 strains were different from the corresponding epitopes in a PCV2a vaccine strain, suggesting that PCV2a-based vaccines may only provide limited protection against these strains. PCV2d strains could be grouped into 3 distinct lines which shared 98.7–100% identity within open reading frame 2 (ORF2). It is the first study reporting the genetic diversity of PCV2 strains in Russia. Our data indicated that, similarly to China, Europe, and USA, PCV2a and PCV2b have largely been replaced by PCV2d. Full article

(This article belongs to the Special Issue Advances in Circoviruses)

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15 pages, 1934 KiB

Open AccessArticle

Non-Assembled ORF2 Capsid Protein of Porcine Circovirus 2b Does Not Confer Protective Immunity

by Flavia Guarneri, Matteo Tonni, Giuseppe Sarli, Maria Beatrice Boniotti, Davide Lelli, Ilaria Barbieri, Giulia D’Annunzio, Giovanni Loris Alborali, Barbara Bacci and Massimo Amadori

Pathogens 2021, 10(9), 1161; https://doi.org/10.3390/pathogens10091161 - 9 Sep 2021

Cited by 3 | Viewed by 1935

Abstract

Porcine Circovirus 2 (PCV2) vaccines are based on either inactivated whole virion, or recombinant ORF2 capsid protein assembled into Virus-like Particles (VLPs). No data are available about the immunizing properties of free, non-assembled capsid protein. To investigate this issue, ORF2 of a reference PCV2b strain was expressed in a Baculovirus-based expression system without assembly into VLPs. The free purified protein was formulated into an oil vaccine at three distinct Ag payloads: 10.8/3.6/1.2 micrograms/dose. Each dose was injected intramuscularly into five, 37-day old piglets, carefully matched for maternally-derived antibody. Five control piglets were injected with sterile PBS in oil adjuvant. Twenty-eight days later, all the pigs were challenged intranasally with 10^5.3 TCID₅₀ of PCV2b strain DV6503. After challenge infection, all the pigs remained in good clinical conditions. The recombinant vaccine did not induce significant antibody and PCV2-specific IFN-γ responses. ELISPOT and lymphocyte proliferation data confirmed poor induction of cell-mediated immunity. In terms of PCV2 viremia, there was no significant difference between vaccinated and control animals. The histological data indicated the absence of a detectable viral load and of PCVAD lesions in both vaccinated and control animals, as well as of histiocytes and multi-nucleated giant cells. We conclude that free, non-assembled ORF2 capsid protein does not induce protective immunity. Full article

(This article belongs to the Special Issue Advances in Circoviruses)

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9 pages, 2921 KiB

Open AccessArticle

Genotyping of Porcine Circovirus 2 (PCV-2) in Vaccinated Pigs Suffering from PCV-2-Systemic Disease between 2009 and 2020 in Spain

by Marina Sibila, Caterina Rocco, Giovanni Franzo, Eva Huerta, Mariano Domingo, José Ignacio Núñez and Joaquim Segalés

Pathogens 2021, 10(8), 1016; https://doi.org/10.3390/pathogens10081016 - 12 Aug 2021

Cited by 13 | Viewed by 2859

Abstract

Vaccination against porcine circovirus 2 (PCV-2) is a common practice all over the world. Vaccines can prevent PCV-2-systemic disease (PCV-2-SD) outbreaks but not PCV-2 infection, which can be detectable in a percentage of vaccinated animals. Occasionally, PCV-2-SD is diagnosed in vaccinated farms. The objective of this study was to genotype the PCV-2 strains detected in vaccinated animals diagnosed with PCV-2-SD. Additionally, the evolution of the frequency of PCV-2 genotype detection at Spanish, European, and world levels was assessed. Fifty cases diagnosed as PCV-2-SD between 2009 and 2020 were included in this study. PCV-2 genotype was determined by sequencing the Cap gene region. Among them, only PCV-2b (23/50, 46%) and PCV-2d (27/50, 54%) genotypes were detected. Although the frequency of detection of these two genotypes was similar, their temporal distribution was different. Whereas most PCV-2b sequences (17/23, 74%) were detected between 2009 and 2012, PCV-2d sequences were obtained from 2013 to 2020. Indeed, a predominance of the PCV-2d genotype was observed from 2013 onwards, a trend also noticed at European and world levels. The results suggest that detection of particular genotypes in vaccinated animals probably reflects the general prevalence of the genotypes over time rather than genotype-specific vaccine-immunity escaping. Full article

(This article belongs to the Special Issue Advances in Circoviruses)

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12 pages, 575 KiB

Open AccessArticle

Canine Circovirus in Foxes from Northern Italy: Where Did It All Begin?

by Giovanni Franzo, Maria Luisa Menandro, Claudia Maria Tucciarone, Giacomo Barbierato, Lorenzo Crovato, Alessandra Mondin, Martina Libanora, Federica Obber, Riccardo Orusa, Serena Robetto, Carlo Citterio and Laura Grassi

Pathogens 2021, 10(8), 1002; https://doi.org/10.3390/pathogens10081002 - 9 Aug 2021

Cited by 8 | Viewed by 2424

Abstract

Canine circovirus (CanineCV) is a recently identified virus affecting both domestic and wild carnivores, including foxes, sometimes in presence of severe clinical signs. Its circulation in wild animals can thus represent a potential threat for endangered species conservation and an infection source for dogs. Nevertheless, no data were available on its circulation in the Alps region of Northern Italy. In the present study, samples collected from 186 foxes in the period 2009–2020 from Valle d’Aosta and Veneto regions were tested using a real-time PCR assay, demonstrating a viral circulation of approximatively 2–5%, depending on the considered regions. Two complete or almost complete genome sequences were obtained, highlighting that the detected strains were part of a so defined “fox only” clade, which suggests that, despite common contact opportunities, Alps foxes are not involved in frequent transmission events to domestic dogs. Such genetic isolation could be at least partially attributed to some sort of independent evolution occurred in the foxes, leading to species barrier. Additionally, CanineCV strains in foxes from Italy were unexpectedly related to those previously identified in foxes from the United Kingdom and Scandinavian area. Combining the history of fox distribution in Europe since the last glacial maximum (LGM) with the viral history allowed us to speculate a long-standing coexistence between European canine circovirus and this host, justifying the peculiar geographic distribution and evolutionary paths of the fox infecting clade. Full article

(This article belongs to the Special Issue Advances in Circoviruses)

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5 pages, 442 KiB

Open AccessCommunication

Molecular Investigation of Porcine Circovirus Type 3 Infection in Pigs in Namibia

by Umberto Molini, Giuseppe Marruchella, Frieda Matheus, Yvonne Maria Hemberger, Bernard Chiwome, Siegfried Khaiseb, Giovanni Cattoli and Giovanni Franzo

Pathogens 2021, 10(5), 585; https://doi.org/10.3390/pathogens10050585 - 11 May 2021

Cited by 4 | Viewed by 1798

Abstract

Porcine circovirus type 3 (PCV-3) infection is widely distributed in domestic pig populations in America, Europe, and Asia. However, no data is currently available about its presence and distribution in Africa. This study investigated the presence of PCV-3 in pigs (n = 122) in Namibia, by means of biomolecular methods. The pig samples collected (n = 122) were representative of the swine industry in Namibia, covering the major pig production facilities in the country. All of the samples tested were negative for PCV-3, and this indicated that the virus was either not present in the country or was circulating at low levels. Further studies are needed to better understand the distribution, if any, of PCV-3 in Namibia. Full article

(This article belongs to the Special Issue Advances in Circoviruses)

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