RESUMEN
H6 avian influenza viruses (AIVs) have a worldwide distribution, and they pose a potential concern for public health. In Taiwan, H6 AIVs have circulated in domestic chickens for more than 40 years, and certain strains have crossed the species barrier to infect mammals. With the goal of containing the disease, there is a pressing need to develop a safe and effective vaccine for pandemic preparedness. In this study, we prepared a virus-like particle (VLP) that consisted of the hemagglutinin (HA) and matrix protein 1 (M1) derived from a H6 AIV as a vaccine antigen, and we examined the immunogenicity and protective efficacy when combined with an adjuvant in a chicken model. Full-length HA and M1 protein genes were cloned and expressed using a baculovirus expression system, and VLPs were purified from the supernatant of insect cell cultures. We performed nanoparticle-tracking analysis and transmission electron microscopy to validate that the particle structure and properties resembled the native virions. In animal experiments, specific-pathogen-free chickens that received the H6 VLPs in combination with an adjuvant showed superior H6N1 virus-specific serum IgG and hemagglutination-inhibition antibody responses, which lasted more than 112 days. Following the H6N1 viral challenge, the vaccinated chickens showed reduced viral replication in the lungs, kidneys and conjunctival/cloacal shedding. The antibodies induced in the chickens by the vaccine were able to cross-react with the H6N1 human isolate and drifted avian H6N1 isolates. In summary, the H6 VLP vaccine elicited superb immunogenicity in vivo, and the use of an adjuvant further enhanced the antiviral protective efficacy. This vaccine formulation could potentially be used to manage H6 influenza virus infections in chickens.
RESUMEN
Porcine deltacoronavirus (PDCoV) was initially documented in Hong Kong and later in the United States, South Korea, and Thailand. To investigate if PDCoV is also present in Taiwan, three swine coronaviruses-PDCoV, porcine epidemic diarrhea virus (PEDV), and transmissible gastroenteritis coronavirus (TGEV)-were tested using real-time reverse transcription polymerase chain reaction (rRT-PCR) in 172 rectal swab samples from piglets exhibiting diarrhea between January 2016 and May 2017 on 68 pig farms in Taiwan. The rRT-PCR results were positive for PDCoV (29/172, 16.9%), PEDV (36/172, 20.9%), TGEV (2/172, 1.2%), and coinfections (16/172, 9.3%). After cloning and sequencing, PDCoV nucleocapsid genes were analyzed. Phylogeny results indicated that the nucleotide sequences of all isolates were like those reported in other countries. To further trace PDCoV in the period of 2011 to 2015, an enzyme-linked immunosorbent assay (ELISA) was used to detect antibodies against PDCoV. The results showed that 279 of 1,039 (26.9%) sera were positive for the PDCoV nucleocapsid protein, implying that PDCoV might have existed in Taiwan before 2011.
