Nucleotide sequence analysis of nucleocapsid protein gene of canine distemper virus isolates in Thailand

Phylogenetic analysis of canine distemper viruses isolated from vaccinated dogs in Wuhan

Canine distemper virus (CDV) is an infectious agent that can cause canine distemper (CD), a lethal disease. Immunization is an effective method to control the infection; however, some cases of failed immunization are observed in animal hospitals every year. Therefore, in this study, we conducted phylogenetic analysis of the H gene of isolated CDVs. We first constructed a modified MDCK cell line, which constitutively expressed signaling lymphocyte activation molecule (SLAM), a specific receptor for CDV. The modified cell line was more suitable for propagation of CDV than the original MDCK cell line. Next, 9 CDVs were successfully isolated from 20 dogs with suspected CD-associated diseases. Of these CDV isolates, three were from vaccinated dogs. The analysis indicated that the H gene sequences of these 9 viruses were highly similar. The present study further supported the finding that the majority of CDV in China belonged to the genotype Asia-1, which was different from vaccine strains (America-1 and America-2). Although the clinical application of the vaccine suggested that it is effective against CDV infection, it remains an open question whether a novel vaccine based on the genotype of the Asia-1 strain would be more suitable for protection of dogs against Asia-1 CDVs infection.

Identification of a novel linear B-cell epitope using a monoclonal antibody against the carboxy terminus of the canine distemper virus nucleoprotein and sequence analysis of the identified epitope in different CDV isolates

BACKGROUND

The Nucleoprotein (NP) is the most abundant and highly immunogenic protein in canine distemper virus (CDV), playing an important role in CDV viral replication and assembly.

RESULTS

In this study, a specific monoclonal antibody, named C8, was produced against the NP protein C terminal (amino acids 401-523). A linear N protein epitope was identified by subjecting a series of partially overlapping synthesized peptides to enzyme-linked immunosorbent assay (ELISA) analysis.The results indicated that ⁴⁴⁴GDKYPIHFNDER⁴⁵⁵ was the minimal linear epitope that could be recognized by mAb C8. Sequence alignments demonstrated that this linear epitope is less conserved among three CDV genotypes. We next analyzed the level of conservation of the defined epitope in19 Chinese CDV clinical isolates, and it has one site variation in amino acid among these CDV isolations. 2 isolates have the amino acid mutations F451L, while one has P448Ssubstitution.Phylogenetic analysis showed the two isolates with F451Lsubstitution had a closer relationship in a virulent strain ZJ-7, so the epitope may be a significant tag associated with virus virulence.

CONCLUSION

This collection of mAb along with defined linear epitope may provide useful reagents for investigations of NP protein function and the development of CDV specific diagnostics.

Structure and antigenicity analysis of the IgG gene for Nyctereutes procyonoides

Objective

Nyctereutes procyonoides immunoglobulin G (IgG) gene is partially cloned.

Material and methods

In order to obtain a certain length (966bp) of Nyctereutes procyonoides immunoglobulin G (IgG), two pairs of primers are designed according to the conserved nucleotide sequence of canine (GenBank:AF354265, AF354265, AF354266, AF354267) and mink (GenBank: L07789). Using Bioinformatics technology and Western-blot to analyze antigenicity of Nyctereutes procyonoides IgG-B gene.

Results

The homology for nucleotide sequence of IgG between Nyctereutes procyonoides and canine (IgG A, IgG B, IgG C, IgG D), mink, Homo sapiens, Oryctolagus cuniculus, Mus musculus, Anas platyrhynchos and gallus were respectively (88.1%, 93.6%, 85.4%, 87.2%), 83.7%, 74.8%, 71.8%, 69.2%, 51.6%, 48.4%. It can be seen that there was high homology of aminoacid sequence between IgG of Nyctereutes procyonoides and IgG (A, B, C, D) of canine. And the serum antibody of Nyctereutes procyonoides had obviously cross-reaction with HRP conjugated rabbit anti-dog IgG, compared with those of canine, oryctolagus cuniculus, mus musculus, mink, gallus.

Conclusions

We successfully got Nyctereutes procyonoides immuneglobulin G (IgG) gene (Gen- Bank: KM010191). There is the closest ties of consanguinity of IgG exist between Nyctereutes procyonoides and canine among the mammal through the genetic evolution. The detection and treament of canine distemper can be used on Nyctereutes procyonoides.

Genotypic lineages and restriction fragment length polymorphism of canine distemper virus isolates in Thailand

Canine distemper virus (CDV) is known to cause multisystemic disease in all families of terrestrial carnivores. Attenuated live vaccines have been used to control CDV in a variety of species for many decades, yet a number of CDV infections in vaccinated dogs are still observed. The aims of this study were to investigate the genetic diversity of CDV lineages based on phosphoprotein (P), hemagglutinin (H) and fusion protein (F) genes and to develop the restriction fragment length polymorphism (RFLP) technique for effective differentiation among individual wild-type and vaccine lineages in Thailand. Four commercial vaccine products, thirteen conjunctival swabs and various tissues from 9 necropsied dogs suspected of having CDV infections were included. Virus isolation was performed using Vero cell expressing canine signaling lymphocyte activation molecules (Vero-DST cells). Reverse-transcription polymerase chain reaction (RT-PCR) on 3 gene regions from the dog derived specimens and the vaccines were carried out, then RFLP analysis upon F-gene amplified fragments was developed. Nucleotide sequence and phylogenetic analysis were compared with other CDV lineages in Genbank. Phylogenetic relationships revealed that CDV field isolates were separated from the vaccine lineage and could be divided into two clusters; one of which belonged to the Asia-1 lineage and another, not related to any previous recognized lineages was proposed as 'Asia-4'. RFLP patterns demonstrating concordance with phylogenetic trees of the distemper virus allowed for differentiation between the Asia-1, Asia-4 and vaccine lineages. Thus, RFLP technique is able to effectively distinguish individual wild-type canine distemper virus from vaccine lineages in Thailand.

Evidence of two co-circulating genetic lineages of canine distemper virus in South America

Canine distemper virus (CDV) is the etiological agent of a multisystemic infection that affects different species of carnivores and is responsible for one of the main diseases suffered by dogs. Recent data have shown a worldwide increase in the incidence of the disease, including in vaccinated dog populations, which necessitates the analysis of circulating strains. The hemagglutinin (H) gene, which encodes the major antigenic viral protein, has been widely used to determine the degree of genetic variability and to associate CDVs in different worldwide circulating lineages. Here, we obtained the sequence of the first full-length H gene of field South American CDV strains and compared it with sequences of worldwide circulating field strains and vaccine viruses. In South America, we detect two co-circulating lineages with different prevalences: the Europe 1 lineage and a new South America 2 lineage. The Europe 1 lineage was the most prevalent in South America, and we suggest renaming it the Europe 1/South America 1 lineage. The South America 2 lineage was found only in Argentina and appears related to wild CDV strains. All South American CDV strains showed high amino-acid divergence from vaccine strains. This genetic variability may be a possible factor leading to the resurgence of distemper cases in vaccinated dog populations.

Identification of a new genotype of canine distemper virus circulating in America

Canine Distemper is a highly contagious viral systemic disease that affects a wide variety of terrestrial carnivores. Canine Distemper virus (CDV) appears genetically heterogeneous, markedly in the hemagglutinin protein (H), showing geographic patterns of diversification that are useful to monitor CDV molecular epidemiology. In Mexico the activity of canine distemper remains high in dogs, likely because vaccine prophylaxis coverage in canine population is under the levels required to control effectively the disease. By phylogenetic analysis based on the nucleoprotein (N) and on the H genes, Mexican CDV strains collected between 2007 and 2010 were distinguished into several genovariants, all which constituted a unique group, clearly distinct from field and vaccine strains circulating worldwide, but resembling a CDV strain, 19876, identified in Missouri, USA, 2004, that was genetically unrelated to other North-American CDV strains. Gathering information on the genetic heterogeneity of CDV on a global scale appears pivotal in order to investigate the origin and modalities of introduction of unusual/novel CDV strains, as well as to understand if vaccine breakthroughs or disease epidemics may be somewhat related to genetic/antigenic or biological differences between field and vaccine strains.

Lights and shades on an historical vaccine canine distemper virus, the Rockborn strain

Both egg- and cell-adapted canine distemper virus (CDV) vaccines are suspected to retain residual virulence, especially if administered to immuno-suppressed animals, very young pups or to highly susceptible animal species. In the early 1980s, post-vaccine encephalitis was reported in dogs from various parts of Britain after administration of a particular batch of combined CDV Rockborn strain/canine adenovirus type-1 vaccine, although incrimination of the Rockborn strain was subsequently retracted. Notwithstanding, this, and other reports, led to the view that the Rockborn strain is less attenuated and less safe than other CDV vaccines, and the Rockborn strain was officially withdrawn from the markets in the mid 1990s. By sequencing the H gene of the strain Rockborn from the 46th laboratory passage, and a commercial vaccine (Candur(®) SH+P, Hoechst Rousell Vet GmbH), the virus was found to differ from the commonly used vaccine strain, Onderstepoort (93.0% nt and 91.7% aa), and to resemble more closely (99.6% nt and 99.3% aa) a CDV strain detected in China from a Lesser Panda (Ailurus fulgens). An additional four CDV strains matching (>99% nt identity) the Rockborn virus were identified in the sequence databases. Also, Rockborn-like strains were identified in two vaccines currently in the market. These findings indicate that Rockborn-like viruses may be recovered from dogs or other carnivores with distemper, suggesting cases of residual virulence of vaccines, or circulation of vaccine-derived Rockborn-like viruses in the field.

Phylogenetic analysis of the haemagglutinin gene of canine distemper virus strains detected from breeding foxes, raccoon dogs and minks in China

Canine distemper virus (CDV) infects a variety of carnivores, including wild and domestic Canidae. Genetic/antigenic heterogeneity has been observed among the various CDV strains, notably in the haemagglutinin (H) gene, that appears as a good target to gather epidemiological information. Based on sequence analysis of the H gene, wild-type CDV strains cluster into distinct geographic lineages (genotypes), irrespective of the species of isolation. The sequence of the H gene of 28 CDV strains detected from both vaccinated and non-vaccinated breeding foxes, raccoon dogs and minks from different geographical areas of China during the years 2004-2008 was determined. All the CDV strains but two (strains HL and HLJ2) were characterized as Asia-1 genotype and were highly similar to each other (96.2-99.7% at the amino acid [aa] level) and to other Asia-1 strains (96.1-99.5% aa) previously detected in China. The CDV strains HL and HLJ2 were both collected from foxes in Heilongjiang province in 2005. Strain HL resembled CDVs of the Arctic genotype (GR88-like) and displayed high aa identity (98.0%) to the Chinese canine strain Liu. By converse, strain HLJ2 was barely related to CDVs of the Asia-2 genotype (88.7-90.3% aa identity), and could represent a novel CDV genotype, tentatively proposed as Asia-3. These results suggest that at least three different CDV genotypes, distantly related (81.8-91.6% aa identity) to the vaccine strains, Onderstepoort-like (America-1 genotype), are currently circulating in breeding foxes, raccoon dogs and minks in China, and that the genotype Asia-1 is predominant. Whether the diversity between wild-type CDVs and the vaccine strains may affect, to some extent, the efficacy of the vaccines deserves further investigations.

Comparison of molecular and growth properties for two different canine distemper virus clusters, Asia 1 and 2, in Japan

To compare the molecular and growth properties of two newly isolated canine distemper virus strains in the Asia 1 and 2 groups with clinico-pathological findings in dogs, nucleotide and predicted amino acid sequence comparisons of genes H and P were performed together with comparative growth profiling. The predicted amino acid sequences of the H gene contained 12 cysteine residues that were conserved among the examined Asia 1 and Asia 2 viruses. The hydrophobic region in the H gene of the Asia 2 isolates was one amino acid longer than that of the Asia 1 group. The H gene of the Asia 1 group had nine putative asparagine (N)-linked glycosylation sites, while there were eight sites in the Asia 2 group. The titers of the cell-associated viruses for the Asia 1 strains were higher than those of the released viruses and were opposite to those of the Asia 2 strains in a previous study. The molecular and growth properties of the Asia 1 and Asia 2 groups seem to vary, although no significant differences were observed in the clinical signs and pathological findings between the two groups.

Molecular analysis of the N gene of canine distemper virus in dogs in Brazil

Eleven central-nervous-system samples collected from stray dogs between 2000 and 2004 were found positive by RT-PCR, which amplified a 480bp fragment of the N gene of canine distemper virus (CDV). Phylogenetic analysis based on partial N-gene sequences showed four major clusters. All dog strains segregated into cluster I, with a mean nucleotide identity of 95.8% and 95.6% with the Onderstepoort and Lederle vaccine strains, respectively. Cluster II contained all the raccoon-related strains, cluster III Orient strains and Cluster IV the Onderstepoort and Lederle vaccine strains, with a mean nucleotide identity of 99.7% between them. This is the first report of phylogenetic analysis of CDV strains in Brazil.

Heterogeneity within the hemagglutinin genes of canine distemper virus (CDV) strains detected in Italy

Canine distemper virus (CDV) is a highly contagious viral pathogen causing lethal disease in dogs and other mammalians. A high degree of genetic variation is found between recent CDV strains and the old CDV isolates used in the vaccines and such genetic variation is regarded as a possible cause of the increasing number of CDV-related diseases in dogs. The H gene shows the greatest extent of genetic variation that allows for distinction of various lineages, according to a geographical pattern of distribution and irrespective of the species of identification. In the present study, hemagglutinin (H) genes obtained from field strains detected from clinical specimens of Italian dogs were analyzed genetically. Phylogenetic analysis revealed that a homogeneous group of CDV strains is widespread in Italian dogs, all which are included into the European lineage. Unexpectedly, strains 179/04 and 48/05 clustered along with CDVs of the Arctic lineage, the highest identity being to strain GR88 (98.0 and 98.4%aa, respectively). The full-length sequence of a red fox CDV strain, 207/00 was also determined and analyzed. The H protein of the fox CDV strain was unrelated to strains within the major European lineage. These results suggest that at least three different CDV lineages are present in Italy.