Antibody response to glycoprotein E after bovine herpesvirus type 1 infection in passively immunised, glycoprotein E‐negative calves

et al. 2009

Phylogenetic studies of the emergence and spread of natural recombinants in herpesviruses infecting humans and animals have been reported recently. However, despite an ever-increasing amount of evidence of recombination in herpesvirus history, the recombination process and the consequences on the genetic diversity of the progeny remain poorly characterized. We addressed this issue by using multiple single-nucleotide polymorphisms (SNPs) differentiating the two subtypes of an alphaherpesvirus, bovine herpesvirus 1 (BoHV-1). Analysis of a large sample of progeny virions obtained in a single growth cycle of coinfected BoHV-1 strains provided a prospective investigation of the recombination dynamics by using SNPs as recombination markers. We found that the simultaneous infection with two closely related herpesviruses results in a highly diversified recombination mosaic. From the analysis of multiple recombinants arising in the progeny, we provide the first evidence of genetic interference influencing the recombination process in herpesviruses. In addition, we report striking differences in the levels of recombination frequency observed along the BoHV-1 genome. With particular emphasis on the genetic structure of a progeny virus population rising in vitro, our data show to which extent recombination participates to the genetic diversification of herpesviruses.Genetic variation within a species arises through the process of mutation. If the mutation is nonlethal and if the new variant is not lost, genetic, demographic, and evolutionary processes determine its population frequency and its nonrandom association (linkage disequilibrium) with adjacent sites along the DNA segment on which it arose. Recombination is the primary genetic process that influences linkage disequilibrium over time, enabling the creation of new combinations of genetic material through the pairing and shuffling of related DNA sequences (2). In contrast with most RNA viruses, DNA replication in herpesviruses leads to rare spontaneous mutations because of an efficient proofreading activity of the DNA polymerase (6,9,10,26). With regard to the low rate of nucleotide substitution, recombination can be seen as an evolutionary driving force increasing the probability of a rare nonsynonymous mutation spreading within a herpesvirus species (44,45). In accordance with this hypothesis, recently reported phylogenetic evidence demonstrated both the high degree of gene conservation in natural herpesvirus populations and the emergence and spread of several natural recombinants in herpesvirus species that infect humans (1,24,25,29,(33)(34)(35)37) and animals (8,18,36).

“…Four BoHV-1 strains were used in the present study. BoHV-1 strains Ciney (22) and Cooper (49) belong to BoHV-1.1, while strains K22 (49) and ST (23) belong to BoHV-1.2.…”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Coinfection with Two Closely Related Alphaherpesviruses Results in a Highly Diversified Recombination Mosaic Displaying Negative Genetic Interference

Muylkens

Farnir

et al. 2009

“…Monolayers were observed daily for 5 to 7 days to detect the cytopathic effect typical of BoHV-1. Nasal fluids found to be positive by this first method were further titrated by plaque assay in 24-and 96-well plates with 3 to 4 days of incubation at 37°C before they were stained with an aqueousalcoholic solution of crystal violet (25). The virus titer was expressed as PFU/100 mg of nasal secretion.…”

Section: Methodsmentioning

confidence: 99%

“…Viral stocks were produced by separate infections of confluent MDBK cells with either the Lam gC Ϫ mutant or the Lam gE Ϫ mutant at a low multiplicity of infection (MOI) of 0.1 in Earle's minimal essential medium supplemented with 2% PS and 2% heat-inactivated horse serum (Serolab; International Medical) (MEM-HS). When a 90% cytopathic effect occurred, the culture medium was harvested and clarified twice by centrifugation at 1,000 ϫ g. The resulting cell-free supernatant was divided into aliquots and frozen at Ϫ80°C (until used for inoculation) and titrated by plaque assay on MDBK cells as previously described (25). When indicated, embryonic bovine lung (DSMZ ACC 192) cells were used to produce BoHV-1 stocks according to the procedure described above for MDBK cells.…”

Section: Methodsmentioning

confidence: 99%

Rise and Survival of Bovine Herpesvirus 1 Recombinants after Primary Infection and Reactivation from Latency

Schynts

Detry

et al. 2003

Recombination is thought to be an important source of genetic variation in herpesviruses. Several studies, performed in vitro or in vivo, detected recombinant viruses after the coinoculation of two distinguishable strains of the same herpesvirus species. However, none of these studies investigated the evolution of the relative proportions of parental versus recombinant progeny populations after coinoculation of the natural host, both during the excretion and the reexcretion period. In the present study, we address this by studying the infection of cattle with bovine herpesvirus 1 (BoHV-1). ؉ /gE ؊ mutants, when inoculated alone, were detected after reactivation treatment. In view of these data, the importance of gE in the biology of BoHV-1 infection and the role of recombination in herpesvirus evolution are discussed.The genomes of large DNA viruses have generally evolved by three mechanisms: mutation during viral DNA replication, acquisition of cellular genes, and recombination between strains of the same viral species. The Herpesviridae form an extensive family of large DNA viruses that appear to have acquired a diverse collection of genes from their hosts at different times in the past (37). The rate of synonymous nucleotide substitution per site per year has been analyzed for different herpesviruses and was estimated to be 20 to 30 times that of the host genome (12,19,29). This low rate of nucleotide substitution most probably reflects the efficient proofreading activity of the herpesvirus DNA polymerase (7) and/or the importance of periods of latency in their biology. Recombination is thought to be an important source of genetic variation in herpesviruses, allowing combination of genetic features shared by different strains. Recombination between herpesviruses was first demonstrated in 1955 when wild-type herpes simplex virus type 1 (HSV-1) was recovered from mixed inoculations between pairs of temperature-sensitive mutants (54). Since then, herpesvirus recombination has been studied both in vitro and/or in vivo between distinguishable strains of HSV-1 and/or 6,20,24,28,35,43,47,48), pseudorabies virus (PrV) (8,9,15,16,17,18,23), feline herpesvirus 1 (14), and varicella-zoster virus (11). From in vitro studies it has been concluded that recombination is a frequent event, leading to the creation of viruses harboring new genetic combinations. Careful analyses of these recombinants has allowed a better understanding of the molecular mechanisms underlying recombination (49). However, in vitro approaches do not reflect what happens in vivo. In vivo reports, carried out mainly using heterologous animal models, led to the important finding that two avirulent strains can recombine to produce virulent viruses which were demonstrated, in most cases, to be lethal for coinoculated animals (15,20,23,43).However, the methods used to study in vivo recombination in the reports referenced above precluded the investigation of some important features linked to recombination. Indeed, these studies detected recombination events...

“…When the cytopathic effect (CPE) reached 90%, the culture medium was removed and clarified by centrifugation (1,500 ϫ g) for 20 min. The supernatants were divided into aliquots, frozen at Ϫ80°C, and titrated by plaque assay on MDBK cells as previously described (31).…”

Section: Methodsmentioning

confidence: 99%

Interspecific Recombination between Two Ruminant Alphaherpesviruses, Bovine Herpesviruses 1 and 5

Keil

Muylkens

et al. 2004

Homologous recombination between different species of alphaherpesviruses has been described between herpes simplex viruses 1 and 2 but has not yet been observed between other alphaherpesviruses. In the present study we chose to assess to what extent in vitro recombination can occur between members of a well-defined group of closely related viruses such as ruminant alphaherpesviruses. At 24 h after infection of epithelial bovine kidney cells with a double-deleted mutant of bovine herpesvirus 1 (BoHV-1) (containing green fluorescent protein and red fluorescent protein genes) and different ruminant alphaherpesviruses, four types of progeny viruses were detected and distinguished according to their phenotype. Frequent recombination events between identical or different strains of BoHV-1 were observed (up to 30%), whereas only two BoHV-1/BoHV-5 recombinants were identified, and no recombinants between BoHV-1 and less closely related caprine and cervine herpesviruses were detected. Restriction analysis of the genomes of the two BoHV-1/BoHV-5 recombinants showed different genetic backgrounds. One possessed a restriction pattern close to BoHV-1, whereas the other one was close to BoHV-5. This exhaustive analysis of each combination of coinfection in a unique situation of five closely related alphaherpesviruses revealed the importance of a high degree of genetic relatedness and similar parental virus growth kinetics for successful interspecific recombination.