One world, one health, one virology of the mysterious coronavirus maze: the canine coronavirus case

Human coronaviruses (HCoV) often have animal origins and then adapt to humans by jumping directly or via an intermediate host. The emergence of SARS-CoV in 2003, MERS-CoV in 2012 and SARS-CoV-2 in late 2019 confirms that coronaviruses can cause serious to fatal illnesses and that bats are likely the source of these. viruses, emphasizing the role of animals as reservoirs.
1
  • Vlasova AN
  • Diaz A
  • Damtie D
  • et al.
Novel canine coronavirus isolated from a patient hospitalized with pneumonia, East Malaysia.

In 2017-2018, a closely related but distinct canine coronavirus (CCoV) was first identified in nasopharyngeal swabs from children with pneumonia in Malaysia.
1
  • Vlasova AN
  • Diaz A
  • Damtie D
  • et al.
Novel canine coronavirus isolated from a patient hospitalized with pneumonia, East Malaysia.

The virus, CCoV-HuPn-2018, grown in the canine A72 cell line, was characterized as a novel canine-feline recombinant virus with a very unique deletion in the nucleoprotein. This feature was similar to the deletion found in SARS-CoV and SARS-CoV-2 that occurred very soon after introduction into humans, suggesting the zoonotic origin of CCoV-HuPn-2018. Analysis of the virus’ genes highlights that CCoV-HuPn-2018 could have infected cats and pigs at one time, but it likely jumped directly from dogs to humans, as the majority of the genome was the same as the CCoV strains, TN-449 and HLJ-073.

1
  • Vlasova AN
  • Diaz A
  • Damtie D
  • et al.
Novel canine coronavirus isolated from a patient hospitalized with pneumonia, East Malaysia.

This finding draws attention to CCoVs and what these viruses have taught. Since the first report of CCoV in 1971, no special attention has been given to this pathogen as it was commonly associated with mild gastroenteritis in dogs. But in recent decades, the history of CCoV has been characterized by the emergence of new viruses, some with pronounced pathogenic potential, which have raised questions about their ability to undergo mutations and recombinations.
2
The evolutionary processes of canine coronaviruses.

The fascinating evolutionary history of CCoVs is intertwined with the history of porcine transmissible gastroenteritis virus (TGEV) and the two feline coronavirus genotypes, feline coronavirus-1 (FCoV-1) and feline coronavirus-2 (FCoV-2). CCoV gave rise to FCoV-2 by homologous RNA recombination with FCoV-1 between the S and M Genoa.
3
  • Herrewegh AAPM
  • I stink
  • Horzinek MC
  • Rottier pajamas
  • by Groot RJ
Feline coronavirus type II strains 79-1683 and 79-1146 arise from a double recombination between feline coronavirus type I and canine coronavirus.

Additionally, analysis of the accessory protein gene, ORF3pointed out that TGEV originated from CCoV through cross-species transmission.

4
  • Lorusso A
  • Decaro N
  • Schellen P
  • et al.
Gain, preservation and loss of a group 1a coronavirus accessory glycoprotein.

The data also suggested that there are two genotypes of CCoV (CCoV-1 and CCoV-2). Phylogenetic analyzes have shown that these viruses share up to 96% nucleotide identity in the genome but have S genes, and that CCoV-1 is more closely related to FCoV-1 than to CCoV-2;
5
  • Pratelli A.
  • Martella V
  • M-pistol
  • et al.
Identification of coronaviruses in dogs that segregate separately from the canine coronavirus genotype.

CCoV-2 has been well known since 1971 and is closely related to FCoV-2.

In 2005, a highly virulent pantropic CCoV-2 strain, CB/05, was detected in dogs with fatal systemic disease.
6
  • Buonavglia C
  • Decaro N
  • Martella V
  • et al.
Highly pathogenic canine coronavirus for dogs.

Sequence analysis of the 3′ end of the CB/05 genome showed that it had strong amino acid identity with CCoV-2, although protein S had the highest identity with CCoV-2. FCoV-2, strain 79-1683. The virus induces severe clinical signs, lymphopenia and lymphoid tissue infection, strongly suggesting that CCoVs can alter their tropism, gaining the ability to spread from the enteric tract to internal organs.

seven
  • Decaro N
  • Mary V
  • Elia G
  • et al.
Recombinant canine coronaviruses in dogs, Europe.

Additional data emerged when CCoVs that had potential double-recombination origins, e.g. S gene exchange with TGEV, have been identified in dogs with gastroenteritis.
8
  • Decaro N
  • Mary V
  • Campolo M
  • et al.
Recombinant canine coronaviruses related to porcine transmissible gastroenteritis virus are circulating in dogs.

The analysis of a region of the genome (3′ end) of four recombinant viruses and the analysis of the almost complete genome of two of these four strains revealed the existence of recombinant CCoVs of the TGEV type. These events represent a kind of sliding door, in which the original CCoV gave rise to the TGEV and, subsequently, the TGEV gave rise to an outbreak of the TGEV-like CCoV. Considering the genetic and antigenic differences between the original and recombinant viruses, CCoV-2 has further been divided into two different subtypes, CCoV-2a and CCoV-2b, which include reference isolates and TGEV-like CCoV- 2.

8
  • Decaro N
  • Mary V
  • Campolo M
  • et al.
Recombinant canine coronaviruses related to porcine transmissible gastroenteritis virus are circulating in dogs.

To assess the distribution of TGEV-like CCoVs, an epidemiological survey was carried out in European canine populations. About 20% of the CCoV-positive samples were characterized as TGEV-like CCoVs, confirming that the new virus is indeed circulating in European countries.
seven
  • Decaro N
  • Mary V
  • Elia G
  • et al.
Recombinant canine coronaviruses in dogs, Europe.

These results underscore the ability of CoVs to undergo genetic recombination and evolution, and to easily cross interspecies barriers. This high potential for genetic recombination ensures the proliferation of new strains that could have selective advantages over their parental genomes.
9
Evolution of positive-strand RNA viruses.

The newly identified CCoV-Hupn-2018 should lead researchers to pay close attention to the mechanisms of recombination between coronaviruses, in addition to the appearance of variants as a result of mutations. The recombination observed in CCoVs could be a harbinger of the evolution of SARS-CoV-2 and continued monitoring of these viruses is needed.

We declare no competing interests.

The references

  1. 1.
    • Vlasova AN
    • Diaz A
    • Damtie D
    • et al.

    Novel canine coronavirus isolated from a patient hospitalized with pneumonia, East Malaysia.

    Clin Infect Dis. 2021; ()

  2. 2.

    The evolutionary processes of canine coronaviruses.

    Adv Virol. 2011; 2011562831

  3. 3.
    • Herrewegh AAPM
    • I stink
    • Horzinek MC
    • Rottier pajamas
    • by Groot RJ

    Feline coronavirus type II strains 79-1683 and 79-1146 arise from a double recombination between feline coronavirus type I and canine coronavirus.

    J Virol. 1998; 72: 4508-4514

  4. 4.
    • Lorusso A
    • Decaro N
    • Schellen P
    • et al.

    Gain, preservation and loss of a group 1a coronavirus accessory glycoprotein.

    J Virol. 2008; 82: 10312-10317

  5. 5.
    • Pratelli A.
    • Martella V
    • M-pistol
    • et al.

    Identification of coronaviruses in dogs that segregate separately from the canine coronavirus genotype.

    Methods Virol J. 2003; 107: 213-222

  6. 6.
    • Buonavglia C
    • Decaro N
    • Martella V
    • et al.

    Highly pathogenic canine coronavirus for dogs.

    Emergency Infect Dis. 2006; 12: 492-494

  7. seven.
    • Decaro N
    • Mary V
    • Elia G
    • et al.

    Recombinant canine coronaviruses in dogs, Europe.

    Emergency Infect Dis. 2010; 16: 41-47

  8. 8.
    • Decaro N
    • Mary V
    • Campolo M
    • et al.

    Recombinant canine coronaviruses related to porcine transmissible gastroenteritis virus are circulating in dogs.

    J Virol. 2009; 83: 1532-1537

  9. 9.

    Evolution of positive-strand RNA viruses.

    Semin Virol. 1992; 3: 315-326

Comments are closed.