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Zebra Alphaherpesviruses (EHV-1 and EHV-9): Genetic Diversity, Latency and Co-Infections

View Article: PubMed Central - PubMed

ABSTRACT

Alphaherpesviruses are highly prevalent in equine populations and co-infections with more than one of these viruses’ strains frequently diagnosed. Lytic replication and latency with subsequent reactivation, along with new episodes of disease, can be influenced by genetic diversity generated by spontaneous mutation and recombination. Latency enhances virus survival by providing an epidemiological strategy for long-term maintenance of divergent strains in animal populations. The alphaherpesviruses equine herpesvirus 1 (EHV-1) and 9 (EHV-9) have recently been shown to cross species barriers, including a recombinant EHV-1 observed in fatal infections of a polar bear and Asian rhinoceros. Little is known about the latency and genetic diversity of EHV-1 and EHV-9, especially among zoo and wild equids. Here, we report evidence of limited genetic diversity in EHV-9 in zebras, whereas there is substantial genetic variability in EHV-1. We demonstrate that zebras can be lytically and latently infected with both viruses concurrently. Such a co-occurrence of infection in zebras suggests that even relatively slow-evolving viruses such as equine herpesviruses have the potential to diversify rapidly by recombination. This has potential consequences for the diagnosis of these viruses and their management in wild and captive equid populations.

No MeSH data available.


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Phylogenetic trees inferred using maximum likelihood from nucleotide sequences of (a) gB and (b) Pol genes for the six zebras WP1, CG2, CG3 (Equine herpesvirus 9 (EHV-9) lytic infection), CP4 (Equine herpesvirus 1 (EHV-1) lytic and EHV-9 latent infection), CP5, and CG6 (EHV-1 and EHV-9 latent infection, respectively) and other equine herpesviruses. Reference sequences are indicated by GenBank accession number, species from which the sequence was isolated, and viral strain. The novel EHV-9 sequences are in red, the novel EHV-1-horse like zebra sequence is in blue, and the novel zebra-EHV-1 sequence is in green. The trees are shown with branches lengths scaled to nucleotide substitutions per site. Selected nodes are labeled with maximum-likelihood bootstrap support values and posterior probabilities, separated by a slash “/”.
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viruses-08-00262-f003: Phylogenetic trees inferred using maximum likelihood from nucleotide sequences of (a) gB and (b) Pol genes for the six zebras WP1, CG2, CG3 (Equine herpesvirus 9 (EHV-9) lytic infection), CP4 (Equine herpesvirus 1 (EHV-1) lytic and EHV-9 latent infection), CP5, and CG6 (EHV-1 and EHV-9 latent infection, respectively) and other equine herpesviruses. Reference sequences are indicated by GenBank accession number, species from which the sequence was isolated, and viral strain. The novel EHV-9 sequences are in red, the novel EHV-1-horse like zebra sequence is in blue, and the novel zebra-EHV-1 sequence is in green. The trees are shown with branches lengths scaled to nucleotide substitutions per site. Selected nodes are labeled with maximum-likelihood bootstrap support values and posterior probabilities, separated by a slash “/”.

Mentions: The phylogenetic relationships of the detected EHV-1 and EHV-9, of lytic and latent infections, were inferred from the sequences of the Pol and gB genes (Figure 3) as well as the UL49.5 gene (Figure S2). Virus sequences from lytic infection in WP1, CG2, and CG3, plus the latent infections in CP4 and CG6 exhibited 98%–99% similarity to EHV-9 reference sequences. The gB sequence of the detected EHV-9 either in captive or wild zebras clustered with a giraffe EHV-9 isolate, forming a sister clade to gazelle EHV-9 isolates (Figure 3a). The phylogenetic tree inferred from the Pol sequences showed that the CG2 lytic, WP1 lytic, CG3 lytic, CP4 latent, and CG6 latent sequences clustered with EHV-9 sequences from gazelle and giraffe (Figure 3b).


Zebra Alphaherpesviruses (EHV-1 and EHV-9): Genetic Diversity, Latency and Co-Infections
Phylogenetic trees inferred using maximum likelihood from nucleotide sequences of (a) gB and (b) Pol genes for the six zebras WP1, CG2, CG3 (Equine herpesvirus 9 (EHV-9) lytic infection), CP4 (Equine herpesvirus 1 (EHV-1) lytic and EHV-9 latent infection), CP5, and CG6 (EHV-1 and EHV-9 latent infection, respectively) and other equine herpesviruses. Reference sequences are indicated by GenBank accession number, species from which the sequence was isolated, and viral strain. The novel EHV-9 sequences are in red, the novel EHV-1-horse like zebra sequence is in blue, and the novel zebra-EHV-1 sequence is in green. The trees are shown with branches lengths scaled to nucleotide substitutions per site. Selected nodes are labeled with maximum-likelihood bootstrap support values and posterior probabilities, separated by a slash “/”.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC5035975&req=5

viruses-08-00262-f003: Phylogenetic trees inferred using maximum likelihood from nucleotide sequences of (a) gB and (b) Pol genes for the six zebras WP1, CG2, CG3 (Equine herpesvirus 9 (EHV-9) lytic infection), CP4 (Equine herpesvirus 1 (EHV-1) lytic and EHV-9 latent infection), CP5, and CG6 (EHV-1 and EHV-9 latent infection, respectively) and other equine herpesviruses. Reference sequences are indicated by GenBank accession number, species from which the sequence was isolated, and viral strain. The novel EHV-9 sequences are in red, the novel EHV-1-horse like zebra sequence is in blue, and the novel zebra-EHV-1 sequence is in green. The trees are shown with branches lengths scaled to nucleotide substitutions per site. Selected nodes are labeled with maximum-likelihood bootstrap support values and posterior probabilities, separated by a slash “/”.
Mentions: The phylogenetic relationships of the detected EHV-1 and EHV-9, of lytic and latent infections, were inferred from the sequences of the Pol and gB genes (Figure 3) as well as the UL49.5 gene (Figure S2). Virus sequences from lytic infection in WP1, CG2, and CG3, plus the latent infections in CP4 and CG6 exhibited 98%–99% similarity to EHV-9 reference sequences. The gB sequence of the detected EHV-9 either in captive or wild zebras clustered with a giraffe EHV-9 isolate, forming a sister clade to gazelle EHV-9 isolates (Figure 3a). The phylogenetic tree inferred from the Pol sequences showed that the CG2 lytic, WP1 lytic, CG3 lytic, CP4 latent, and CG6 latent sequences clustered with EHV-9 sequences from gazelle and giraffe (Figure 3b).

View Article: PubMed Central - PubMed

ABSTRACT

Alphaherpesviruses are highly prevalent in equine populations and co-infections with more than one of these viruses’ strains frequently diagnosed. Lytic replication and latency with subsequent reactivation, along with new episodes of disease, can be influenced by genetic diversity generated by spontaneous mutation and recombination. Latency enhances virus survival by providing an epidemiological strategy for long-term maintenance of divergent strains in animal populations. The alphaherpesviruses equine herpesvirus 1 (EHV-1) and 9 (EHV-9) have recently been shown to cross species barriers, including a recombinant EHV-1 observed in fatal infections of a polar bear and Asian rhinoceros. Little is known about the latency and genetic diversity of EHV-1 and EHV-9, especially among zoo and wild equids. Here, we report evidence of limited genetic diversity in EHV-9 in zebras, whereas there is substantial genetic variability in EHV-1. We demonstrate that zebras can be lytically and latently infected with both viruses concurrently. Such a co-occurrence of infection in zebras suggests that even relatively slow-evolving viruses such as equine herpesviruses have the potential to diversify rapidly by recombination. This has potential consequences for the diagnosis of these viruses and their management in wild and captive equid populations.

No MeSH data available.


Related in: MedlinePlus