Necrotic enteritis in a commercial turkey flock coinfected with hemorrhagic enteritis virus.

Four turkeys from a commercial flock with acutely elevated mortality levels were submitted for postmortem examination and diagnostic workup. No clinical signs had been observed before death. On gross examination, hemorrhage and necrosis were present throughout the intestinal tracts, and the spleens were markedly enlarged and speckled. Microscopically, numerous, large basophilic-to-amphophilic intranuclear inclusion bodies were observed in mononuclear cells of the spleen and the lamina propria of the small intestine. In addition, there were lesions of diffuse villus blunting and necrosis of the small intestine, with large numbers of rod-shaped bacteria adhered to the epithelium and in the intestinal lumen. Hemorrhagic enteritis virus (HEV) infection was confirmed via PCR on the spleen. Clostridium perfringens was demonstrated in the small intestine by anaerobic culture and immunohistochemistry. The C. perfringens isolate was type F by PCR and, to our knowledge, necrotic enteritis in turkeys has not been described in association with C. perfringens type F infection.

Coinfection with porcine epidemic diarrhea virus and Clostridium perfringens type A enhances disease severity in weaned pigs.

Clostridium perfringens is a constituent of the normal gut microbiome in pigs; however, it can potentially cause pre- and post-weaning diarrhea. Nevertheless, the importance of this bacterium as a primary pathogen of diarrhea in piglets needs to be better understood, and the epidemiology of C. perfringens in Korean pig populations is unknown. To study the prevalence and typing of C. perfringens, 203 fecal samples were collected from diarrheal piglets on 61 swine farms during 2021-2022 and examined for the presence of C. perfringens and enteric viruses, including porcine epidemic diarrhea virus (PEDV). We determined that the most frequently identified type of C. perfringens was C. perfringens type A (CPA; 64/203, 31.5%). Among the CPA infections, single infections with CPA (30/64, 46.9%) and coinfections with CPA and PEDV (29/64, 45.3%) were the most common in diarrheal samples. Furthermore, we conducted animal experiments to investigate the clinical outcome of single infections and coinfections with highly pathogenic (HP)-PEDV and CPA in weaned piglets. The pigs infected with HP-PEDV or CPA alone showed mild or no diarrhea, and none of them died. However, animals that were co-inoculated with HP-PEDV and CPA showed more-severe diarrheal signs than those of the singly infected pigs. Additionally, CPA promoted PEDV replication in coinfected piglets, with high viral titers in the feces. A histopathological examination revealed more-severe villous atrophy in the small intestine of coinfected pigs than in singly infected pigs. This indicates a synergistic effect of PEDV and CPA coinfection on clinical disease in weaned piglets.

Novel intranasal vaccine targeting SARS-CoV-2 receptor binding domain to mucosal microfold cells and adjuvanted with TLR3 agonist Riboxxim™ elicits strong antibody and T-cell responses in mice.

SARS-CoV-2 continues to circulate in the human population necessitating regular booster immunization for its long-term control. Ideally, vaccines should ideally not only protect against symptomatic disease, but also prevent transmission via asymptomatic shedding and cover existing and future variants of the virus. This may ultimately only be possible through induction of potent and long-lasting immune responses in the nasopharyngeal tract, the initial entry site of SARS-CoV-2. To this end, we have designed a vaccine based on recombinantly expressed receptor binding domain (RBD) of SARS-CoV-2, fused to the C-terminus of C. perfringens enterotoxin, which is known to target Claudin-4, a matrix molecule highly expressed on mucosal microfold (M) cells of the nasal and bronchial-associated lymphoid tissues. To further enhance immune responses, the vaccine was adjuvanted with a novel toll-like receptor 3/RIG-I agonist (Riboxxim™), consisting of synthetic short double stranded RNA. Intranasal prime-boost immunization of mice induced robust mucosal and systemic anti-SARS-CoV-2 neutralizing antibody responses against SARS-CoV-2 strains Wuhan-Hu-1, and several variants (B.1.351/beta, B.1.1.7/alpha, B.1.617.2/delta), as well as systemic T-cell responses. A combination vaccine with M-cell targeted recombinant HA1 from an H1N1 G4 influenza strain also induced mucosal and systemic antibodies against influenza. Taken together, the data show that development of an intranasal SARS-CoV-2 vaccine based on recombinant RBD adjuvanted with a TLR3 agonist is feasible, also as a combination vaccine against influenza.