Ubiquitin-specific protease 18 in mallard (Anas platyrhynchos) interferes with type I interferon-mediated inhibition of high pathogenicity avian influenza virus replication.

Ubiquitin-specific protease 18 (USP18) is a well-established innate immune factor in vertebrates. Although Anatidae birds rarely exhibit distinctive clinical signs during high pathogenicity avian influenza virus (HPAIV) infections, some virus strains cause deadly diseases. Here, we investigated the association between USP18 expression and pathogenicity during HPAIV infections in the Anatidae mallard Anas platyrhynchos. First, mallard USP18 gene (duUSP18) was cloned, and its transcriptional variants, with three different open reading frames, were characterized. Experimental infections with two different pathogenic strains, Miyazaki and Takeo, demonstrated an early induction of duUSP18 mRNA upon HPAIV infection in a bird's whole body in vivo and in primary duck cells in vitro, which was positively associated with pathogenicity in mallards. In addition, duUSP18 knockdown under interferon-ß stimulation attenuated viral replication, regardless of pathogenicity. These results indicate a role for duUSP18 in favoring viral replication and virus resistance to type I interferon immunity in mallards.

Comparative susceptibility of mallard (Anas platyrhynchos) to infection with high pathogenicity avian influenza virus strains (Gs/Gd lineage) isolated in Japan in 2004-2017.

The Goose/Guangdong-lineage (Gs/Gd) H5 high pathogenicity avian influenza viruses (HPAIVs) spread among poultry and wild birds worldwide; an association has been identified between the migration of wild birds and spread of HPAIVs. Every autumn-spring season, the mallard (Anas platyrhynchos) migrates to Japan in substantial numbers for overwintering; however, to the best of our knowledge, no virological studies have focused on mallards' susceptibility to the HPAIVs in Japan. To evaluate the susceptibility of mallards to infection with Gs/Gd H5 HPAIVs isolated during previous outbreaks in Japan, we experimentally infected the birds with various virus strains: A/chicken/Yamaguchi/7/2004 (H5N1) (clade 2.5), A/chicken/Miyazaki/K11/2007 (H5N1) (clade 2.2), A/whooper swan/Akita/1/2008 (H5N1) (clade 2.3.2), A/mandarin duck/Miyazaki/22M-765/2011 (H5N1) (clade 2.3.2.1c), A/duck/Chiba/26-372-48/2014 (H5N8) (clade 2.3.4.4c), A/duck/Hyogo/1/2016 (H5N6) (clade 2.3.4.4e) and A/mute swan/Shimane/3211A002/2017 (H5N6) (clade 2.3.4.4b). The birds exhibited high tracheal shedding for a prolonged period, particularly those infected with A/duck/Hyogo/1/2016 (H5N6). Various clinical manifestations ranging from asymptomatic to mild (corneal opacity) infections to neurological disorders accompanied by mortality were noted depending on the virus strain. Furthermore, virus-infected mallards contaminated both cohoused mallards and water in their surroundings. Thus, mallards may disseminate viruses in the environment, thereby influencing HPAI outbreaks in Japan. Therefore, mallards represent an important migratory bird species that spread HPAIVs in Japan.

Thrombopoietin (TPO) induces thrombocytic colony formation of kidney cells synergistically with kit ligand A and a non-secretory TPO variant exists in common carp.

The development of mammalian megakaryocytes and platelets is regulated by numerous cytokine signals, primarily through the thrombopoietin (TPO)/c-MPL axis. Although non-mammalian vertebrates are known to possess nucleated thrombocytes functionally equivalent to mammalian platelets, the dynamics of the thrombocyte development remains unclear. Here we identified TPO and a splice variant (TPO-v) caused by the intron retention in common carp (Cyprinus carpio). Both the tpo and its variant transcripts were highly expressed in heart and liver. Recombinant carp TPO (rcTPO) was produced and purified in HEK293T cells stably expressing tpo, but TPO-v was shown not to be secreted from the transfectants. rcTPO induced the formation of colony-forming unit-thrombocyte (CFU-T) colonies which were recognized by a monoclonal antibody against carp thrombocytes expressing c-mpl and cd41, in a dose-dependent manner. The combination of rcTPO and recombinant carp Kit ligand A (rcKITLA) exerted a significant synergistic effect on three types of colony formation: thrombocytic colonies, thrombocytic burst colonies and thrombocytic/erythroid colonies. Utilizing this colony assay to examine the distribution of thrombocytic progenitor cells in carp, we demonstrated that carp head and trunk kidney play a primary role in thrombopoiesis, while the spleen does not. Our results indicate that carp possess mechanisms of TPO- and KITLA-dependent thrombopoiesis similar to those in other vertebrates and the sites of thrombopoiesis are restricted to the kidney, the primary hematopoietic organ in the teleost fish.

Effects of supplemental ß-carotene on colostral immunoglobulin and plasma ß-carotene and immunoglobulin in Japanese Black cows.

Data from 26 Japanese Black cows were collected to clarify the effects of supplemental ß-carotene on colostral immunoglobulin (Ig) and plasma ß-carotene and Ig in the cows. Cows were assigned to control or ß-carotene groups from 21 days before the expected calving date to 60 days after parturition. Supplemental ß-carotene was provided at 500 mg/day in the ß-carotene group. Supplemental ß-carotene drastically increased plasma ß-carotene concentrations in the cows from parturition to 60 days after parturition, and plasma ß-carotene concentrations in the control and ß-carotene groups at parturition were 202 and 452 µg/dl, respectively. Supplemental ß-carotene had no effects on plasma IgG1 , IgA or IgM concentrations at parturition. Supplemental ß-carotene increased colostral IgG1 concentrations in the cows, but colostral ß-carotene, IgA and IgM concentrations were not affected by supplemental ß-carotene. These results indicate that supplemental ß-carotene is effective to enhance colostral IgG1 concentrations and plasma ß-carotene concentrations in Japanese Black cows.