Immunohistochemical evidence of canine morbillivirus (canine distemper) infection in coatis (Nasua nasua) from Southern Brazil

A Bacterium-like Particle Vaccine Displaying Envelope Proteins of Canine Distemper Virus Can Induce Immune Responses in Mice and Dogs

Canine distemper virus (CDV) can cause fatal infections in giant pandas. Vaccination is crucial to prevent CDV infection in giant pandas. In this study, two bacterium-like particle vaccines F3-GEM and H4-GEM displaying the trimeric F protein or tetrameric H protein of CDV were constructed based on the Gram-positive enhanced-matrix protein anchor (GEM-PA) surface display system. Electron microscopy and Western blot results revealed that the F or H protein was successfully anchored on the surface of GEM particles. Furthermore, one more bacterium-like particle vaccine F3 and H4-GEM was also designed, a mixture consisting of F3-GEM and H4-GEM at a ratio of 1:1. To evaluate the effect of the three vaccines, mice were immunized with F3-GEM, H4-GEM or F3 and H4-GEM. It was found that the level of IgG-specific antibodies and neutralizing antibodies in the F3 and H4-GEM group was higher than the other two groups. Additionally, F3 and H4-GEM also increased the secretion of Th1-related and Th2-related cytokines. Moreover, F3 and H4-GEM induce IgG and neutralizing antibodies' response in dogs. Conclusions: In summary, F3 and H4-GEM can provoke better immune responses to CDV in mice and dogs. The bacterium-like particle vaccine F3 and H4-GEM might be a potential vaccine candidate for giant pandas against CDV infection.

Canine distemper virus N protein induces autophagy to facilitate viral replication

BACKGROUND

Canine distemper virus (CDV) is one of the most contagious and lethal viruses known to the Canidae, with a very broad and expanding host range. Autophagy serves as a fundamental stabilizing response against pathogens, but some viruses have been able to evade or exploit it for their replication. However, the effect of autophagy mechanisms on CDV infection is still unclear.

RESULTS

In the present study, autophagy was induced in CDV-infected Vero cells as demonstrated by elevated LC3-II levels and aggregation of green fluorescent protein (GFP)-LC3 spots. Furthermore, CDV promoted the complete autophagic process, which could be determined by the degradation of p62, co-localization of LC3 with lysosomes, GFP degradation, and accumulation of LC3-II and p62 due to the lysosomal protease inhibitor E64d. In addition, the use of Rapamycin to promote autophagy promoted CDV replication, and the inhibition of autophagy by Wortmannin, Chloroquine and siRNA-ATG5 inhibited CDV replication, revealing that CDV-induced autophagy facilitated virus replication. We also found that UV-inactivated CDV still induced autophagy, and that nucleocapsid (N) protein was able to induce complete autophagy in an mTOR-dependent manner.

CONCLUSIONS

This study for the first time revealed that CDV N protein induced complete autophagy to facilitate viral replication.

Difference Analysis Between Canine Adenovirus Types 1 And 2

Canine adenoviruses (CAdVs) include type 1 (CAdV-1, virulent strain) and type 2 (CAdV-2, attenuated strain). In recent years, the incidences of CAdV infections are increasing. However, they are difficult to distinguish when the symptoms are untypical. It is pivotal to find the differences between the two virus types for scientific, epidemiological, and specific treatment. CAdV-1 (virulent strain) and CAdV-2 (attenuated strain) induced canine hepatitis (ICH) and tracheobronchitis (ITB), respectively, but the clinical symptom is not obvious. CAdV-1 and CAdV-2 have the same genome structure, diameter, morphological features, and cytopathic features, but the same character hinder the diagnose time of the serotypes. CAdV-1 and CAdV-2 have a difference in the genome sequence, coding proteins, viral activity, hemagglutination patterns. After infection, pathogenicity and transmission route are different between the two serotypes. Sequence alignment, PCR, Real time-PCR assay are useful methods to distinguish the two serotypes. The attenuated live CAdV-2 vaccine is currently used to protect against CAdV-1, but it also has a risk. The further research should focus on the pathogenicity mechanism and the useful vaccine for the two serotypes of canine adenovirus.

First description of sarcoptic mange in a wild coati (Nasua narica), in Ecuador, and cooccurrence of canine distemper virus

We present a case of Sarcoptes and canine distemper virus (CDV) infection in a white-nosed coati (Nasua narica) that was trapped in the dry tropical forest of Cerro Blanco reserve, located in the coastal region of Ecuador. Sarcoptic mange is a highly contagious and zoonotic disease with worldwide distribution that causes epidemics. Mange is produced by Sarcoptes mites that causes severe epidermal damage. Secondary infections and physiological constrictions without treatment can lead to death of the host. In addition, cooccurrence of canine distemper virus was detected via iiRT-PCR from serum samples. Physical analyses showed that 90% of the skin was affected by severe alopecia due to the sarcoptic mange infection. The presence of mites and histopathological analyses confirmed the diagnosis of infection. This coati was taken to a veterinary clinic and was fed every day, but it died after four days. This is the first report of sarcoptic mange and the first report of CDV in white-nosed coatis in South America. Further studies are needed in this region, to seek out other suspected cases, given the high capacity for disease transmission. Preventive actions to avoid epidemic and zoonotic episodes are needed.

Canine distemper virus and canine adenovirus type-2 infections in neotropical otters (Lontra longicaudis) from Southern Brazil

All descriptions of infectious diseases affecting otters were published in the Northern Hemisphere, with no occurrence identified in neotropical otters (Lontra longicaudis). Consequently, a retrospective histopathological study using archival tissue samples from six free-living neotropical otters was done to investigate the possible occurrence of disease patterns associated with common viral infectious disease agents of the domestic dogs. Immunohistochemical (IHC) assays were designed to identify intralesional tissue antigens of canine distemper virus (CDV), and canine adenovirus-1 (CAdV-1) and canine adenovirus-2 (CAdV-2). The most frequent histopathological patterns diagnosed were interstitial pneumonia (83.33%; 6/5) and hepatocellular vacuolar degeneration (50%; 3/6). IHC identified intralesional intracytoplasmic immunoreactivity to CDV antigens in all otters evaluated, with positive immunolabeling occurring within epithelial cells of the lungs, stomach, kidneys, and liver, and skin. Intracytoplasmic CAdV-2 antigens were identified within epithelial cells of the peribronchial glands in four otters with interstitial pneumonia. These findings resulted in singular and simultaneous infections in these neotropical otters, represented the first report of concomitant infections by CDV and CAdV-2 in free-living neotropical otters from the Southern Hemisphere, and suggested that this mammalian species is susceptible to infections by viral disease agents common to the domestic dogs and may develop similar histopathologic disease patterns.

Apoptotic investigation of brain tissue cells in dogs naturally infected by canine distemper virus

Background

Canine distemper caused by canine distemper virus that belongs to the Morbillivirus genus of the Paramyxoviridae family is still a global epidemic significant infectious disease, especially in pet dogs in China and serious harm to the development of the dog industry. It has been known that apoptosis caused by the canine distemper virus can show in culture cells, lymphoid tissues, and the cerebellum. However, its occurrence in brain tissue cells remains unclear. To investigate the relationship among canine distemper infecting brain tissues, apoptosis in brain tissue cells, and demyelinating pathogenesis was investigated.

Methods

16 naturally infected dogs that exhibited clinical signs of CD and tested positive for the anti-CDV monoclonal antibody and six healthy dogs that served as the control, were used in the research. Brain specimens were divided into the cerebrum, brain stem, and cerebellum embedded in paraffin and made the sections respectively. Approximately 5 µm-thick sections were stained by hematoxylin–eosin, methyl green pyronin, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling technique, and immunohistochemistry. CDV nucleocapsid protein was detected by immune streptavidin-biotinylated peroxidase complex.

Results

Alterations in the brain tissues of CDV-infected dogs involved both various cells and nerve fibers. CDV had varying degrees of cytotropism to all brain tissue cells; apoptosis also occurred in all brain cells, especially in the endothelia of cerebral vessels, astrocytes, oligodendrocytes, and ependymal cells, the more serious infection, the more obvious apoptosis. Serious infections also involved the pyramidal and Purkinje cells. The nervous fibers exhibited demyelinating lesions (showed small multifocal vacuole), and some axonal neuron atrophy gradually disappeared (formed large vacuole).

Conclusions

Apoptosis in brain tissue cells was mainly related to the propagation path and cytotropism of CDV. The apoptosis of astrocytes, oligodendrocytes, and some neurons may play a significant role in the demyelinating pathogenesis in dogs with acute canine distemper. A lot of diverse nervous signs shown in the clinic may be related to different neuron apoptosis.