Citric Acid Promotes Immune Function by Modulating the Intestinal Barrier.

Amidst increasing concern about antibiotic resistance resulting from the overuse of antibiotics, there is a growing interest in exploring alternative agents. One such agent is citric acid, an organic compound commonly used for various applications. Our research findings indicate that the inclusion of citric acid can have several beneficial effects on the tight junctions found in the mouse intestine. Firstly, the study suggests that citric acid may contribute to weight gain by stimulating the growth of intestinal epithelial cells (IE-6). Citric acid enhances the small intestinal villus-crypt ratio in mice, thereby promoting intestinal structural morphology. Additionally, citric acid has been found to increase the population of beneficial intestinal microorganisms, including Bifidobacterium and Lactobacillus. It also promotes the expression of important protein genes such as occludin, ZO-1, and claudin-1, which play crucial roles in maintaining the integrity of the tight junction barrier in the intestines. Furthermore, in infected IEC-6 cells with H9N2 avian influenza virus, citric acid augmented the expression of genes closely associated with the influenza virus infection. Moreover, it reduces the inflammatory response caused by the viral infection and thwarted influenza virus replication. These findings suggest that citric acid fortifies the intestinal tight junction barrier, inhibits the replication of influenza viruses targeting the intestinal tract, and boosts intestinal immune function.

Pathogenicity, transmissibility, and immunogenicity of recombinant H9N2 avian influenza viruses based on representative viruses of Southeast China.

H9N2 is currently the main subtype of avian influenza in China. In order to use reverse genetics to rapid preparation of seed strains for vaccine production, and intend to prevent and control the H9N2 subtype epidemic strains of avian influenza virus (AIV). In this study, we successfully rescued 2 H9N2 recombinant viruses based on the representative viruses of Southeast China and confirmed by RT-PCR and sequencing. Genetic stability, pathogenicity, transmissibility, and antigenicity of 2 recombinant viruses were evaluated. Compared to the FZ1, the growth kinetics of H9N2(HA+NA)/PR8 showed no significant difference, H9N2(HA+NA+M+PB1)/PR8 was slightly lower. Our study also confirmed 2 recombinant viruses had good genetic stability after 10 passages but possessed lower pathogenicity than FZ1. Although both recombinant viruses led to seroconversion in all inoculated birds on 14 dpi, they complete loss of viral transmission of the virus to contact birds. In addition, birds were immunized via hypodermic route by inactivated vaccines of H9N2(HA+NA)/PR8, H9N2(HA+NA+M+PB1)/PR8 and wild-type virus with a single dose, and the results showed that the hemagglutination inhibition titers on 21 dpv were 10.5, 9.6, and 10.5 log2, respectively. And recombinant viruses both provided a certain protection against wild-type virus challenge. In conclusion, these data indicated that 2 recombinant viruses will be expected to be used as inactivated vaccines to controlling the spread of H9N2 subtype AIV even have potential application for attenuated viral vaccines, which provides a reference for the prevention and control of influenza virus pandemics.

An investigation of the perceptions of laboratory animal welfare issues among undergraduate and graduate veterinary students in southeastern China.

Animal experiments have played a significant role in advancing scientific knowledge and enhancing people's quality of life. In order to better understand the opinions and knowledge of veterinary students in the domain of laboratory animal welfare and to explore and advance the teaching methods used in animal ethics education, a questionnaire was designed and used to conduct a survey among undergraduate and postgraduate students majoring in veterinary medicine. The survey encompassed various topics, such as students' level of knowledge about animal welfare, their perspectives on laboratory animals, their proficiency with animal experiments, and their opinions on teaching methods and content. The respondents were a total of 150 undergraduate students and 148 graduate students. The survey results indicated that most students expressed a strong sense of responsibility for the safeguarding of the welfare of experimental animals. However, there were a few students who lacked compassion for animals. Additionally, there was a general lack of basic theoretical knowledge of animal ethics and an inadequate grasp of experimental techniques among current students. Furthermore, most of the participants expressed a strong sense of responsibility to advocate for animal welfare. Although a substantial number of students were unaware of the existence of agencies for the supervision of work involving laboratory animals, they supported teaching and supervision in the domain of animal welfare and were open to various teaching methods and topics of content. In conclusion, targeted training and education regarding laboratory animal welfare and ethics should be conducted in the future to address the specific needs of students. This study provides a foundation for future animal welfare education and will help to improve the professional skills and humanistic qualities of veterinary students.

Pathogenicity and genome changes in QX-like infectious bronchitis virus during continuous passaging in embryonated chicken eggs.

Infectious bronchitis (IB) remains a major problem in the global poultry industry despite the many available vaccines. Live attenuated vaccines are the most effective means of preventing IB and are traditionally generated by serial passaging of a wild strain in embryonated chicken eggs. In this study, the SZ isolate of the QX-like infectious bronchitis virus (IBV) was continuously passaged in chicken embryos for 250 passages. We compared the pathogenicity of different passages (SZ50, SZ100, SZ150, SZ200 and SZ250) of strain SZ by clinical signs, gross lesions, viral load, tissue tropism, weight gain and tracheal ciliary activity. As the passaging increased in the chicken embryos, the strain lost its ability to infect many organs, and the viral pathogenicity gradually decreased. We also found 23 genomic variations of the QX-like strain SZ throughout the passaging process by further analyzing its complete genome sequence. This work offers valuable insight for IBV vaccine development and further research on the IBV attenuation mechanisms.

Molecular characteristics and pathogenicity analysis of QX-like avian infectious bronchitis virus isolated in China in 2017 and 2018.

Proportions of QX-like genotype infectious bronchitis virus (IBV) isolates have increased over time. Here, to better understand the epidemiology and pathogenicity of IBV in China and control the spread of infectious bronchitis (IB), we conducted sequence analyses and examined the pathogenicity of 5 field isolates from diseased flocks in 2017 and 2018. Sequence analyses revealed that all the 5 strains, as well as many recent field isolates from other researchers, belonged to the QX-like IBV genotype, which were distantly related to commercial vaccine strains. Viral pathogenicity experiments showed that the isolates caused high morbidity and severe ciliostasis in chickens, although they caused milder lethality. This provides further evidence that QX-like IBV emergence remains a major problem in the poultry industry, and information on IBV epidemiology and pathogenicity may help to control IB.

S gene and 5a accessory gene are responsible for the attenuation of virulent infectious bronchitis coronavirus.

To explore the critical genes associated with infectious bronchitis virus (IBV) virulence, we compared the genome sequences of virulent YN strain and its attenuated strain aYN. Accumulation of mutations in the S gene and the accessory gene 5a were observed, suggesting a potential role in the loss of viral pathogenicity. Two recombinant IBVs (rIBVs) with replacement of the S gene or 5a with corresponding regions from aYN were rescued to verify this speculation. Embryo mortality time/rate showed that rYN-S-aYN and rYN-5a-aYN had an attenuated phenotype in ovo. Replication assay in ovo and in vitro demonstrated the rIBVs had similar replication patterns with wild-type rIBV. Both rIBVs showed reduced mortality, tissue lesions and tissue virus titers in chicken. In conclusion, S gene and 5a accessory gene are responsible for the attenuation of virulent IBV. Insight into the genes responsible for virus attenuation will facilitate the development of future vaccines against IBV.

Pathogenicity differences between a newly emerged TW-like strain and a prevalent QX-like strain of infectious bronchitis virus.

TW-like IBV isolates have appeared frequently in recent years in mainland China. In this study, we compared the TW-like IBV GD strain and the predominant QX-like SD strain in terms of serology and pathogenicity to 3-week-old specific-pathogen-free chickens. Both strains could cause severe respiratory distress and renal lesions, with a mortality rate were approximately 20%. Virus were continuously shed via the respiratory tract and cloaca. However, the infection pattern of the two isolates were different. The GD strain persisted for a longer duration and caused extensive damages to the tracheas and lungs. Moreover, chickens infected with the GD strain showed inefficient recovery of damaged cilia after infection. Our findings suggested that the newly emerged TW-like IBV GD strain showed obvious differences in pathogenicity, tissue tropism and replication efficiency compared with the QX-like IBV SD strain, with the TW-like GD strain showing stronger tropism to the respiratory tract and a longer duration of clinical signs.

Attenuation, safety, and efficacy of a QX-like infectious bronchitis virus serotype vaccine.

Avian infectious bronchitis (IB) is a highly contagious disease caused by avian infectious bronchitis virus (IBV), which is a considerable economic threat to the poultry industry. QX-like IBV strains have increasingly emerged in China in recent years. Hence, development of a specific vaccine to guard against their potential threat is important. In this study, we sought to develop an attenuated vaccine strain. First, attenuated QX-like IBV strain SZ130 was created by continuous passage in chicken embryos for 130 generations, and then its safety was tested. We also evaluated the protective efficacy of different doses of SZ130 against challenge with QX-like IBV field strain SD in chickens. SZ130-infected birds did not experience IB-like signs and organ lesions. Additionally, an excellent protective effect of SZ130 vaccination was observed when vaccinated birds were challenged with SD, with no clinical signs or gross lesions, decreased target tissue replication rates, and lower ciliostasis scores in all immunized groups. These findings indicate that attenuated IBV strain SZ130 is highly safe in chicks and may serve as an effective vaccine against the threat posed by QX-like IBV strains.

Pathogenicity differences between QX-like and Mass-type infectious bronchitis viruses.

Infectious bronchitis is a highly contagious, acute viral respiratory disease of chickens, caused by infectious bronchitis virus (IBV). In recent years, the isolation rate of QX-like IBV has increased in the world. To clarify this phenomenon and better understand the pathogenicity of QX-like IBV, we examined differences in pathogenicity between two IBV strains, SD and M41, which belong to QX-like and Mass-type IBV, respectively. SD strain was more virulent in 3-week-old specific-pathogen-free chickens than M41 strain causing higher mortality with severe renal lesions. The tissue distribution of the two virus strains was tested by real-time RT-PCR. The results showed that the viral genome copy numbers in the tissues of chickens inoculated with SD strain were higher than those in chickens inoculated with M41 strain, with the exception of the trachea and lung. This study indicates that there are tremendous differences in pathogenicity and tissue tropism between the QX-like strain and Mass-type strain. These findings may benefit the prevention of infectious bronchitis in the poultry industry in China.

Analysis of antigenicity and pathogenicity reveals major differences among QX-like infectious bronchitis viruses and other serotypes.

Avian coronavirus infectious bronchitis virus (IBV) causes considerable damage to the poultry industry worldwide and the proportion of QX-like genotype isolates have increased over time. Here, to better understand the antigenicity and pathogenicity of this genotype, we conducted sequence analyses, cross neutralization tests, and also examined the pathogenicity of two strains, SD and SZ. Sequence analyses revealed that SD and SZ isolates belong to the QX-like IBV genotype and share high homology in their full-length genomes. Cross neutralization tests showed high cross neutralization between SD and SZ, but distant relationships with other representative strains of the classical IBV serotypes. Virus infection experiments showed that SD caused high mortality with strong respiratory and renal pathogenicity in chickens, whereas SZ caused milder lesions by comparison. This study highlights the big discrepancy in antigenicity that exists between QX-like strains and other serotypes. Collectively, these findings provide important information about the epidemiology and pathogenicity of IBV, which may benefit the control of IB in the poultry industry.

Pathogenicity of a TW-Like Strain of Infectious Bronchitis Virus and Evaluation of the Protection Induced against It by a QX-Like Strain.

Avian infectious bronchitis, a highly contagious disease caused by avian infectious bronchitis virus (IBV), is of considerable economic importance to the poultry industry. New IBV TW-like strains have increasingly emerged in China in recent years; hence, evaluating their pathogenicity and developing a specific vaccine to guard against their potential threat to the poultry industry is important. Here, we examined the pathogenicity of a TW-like IBV strain (GD), and evaluated the protective efficacy of the QX-like strain (JS) against GD in challenge infections in chickens. The results revealed that strain-GD-infected birds experienced severe respiratory signs, renal lesions, and 30-40% mortality. The GD virus had extensive tissue tropism, especially in the trachea, lungs, kidneys, and bursa of Fabricius, and was continuously shed via the respiratory tract and cloaca. The QX-like IBV strain JS is able to completely protect chickens from challenge with the TW-like IBV GD field strain, with no clinical signs or gross lesions, decreased tissue replication rates, lower ciliostasis score, and reduced virus shedding. These findings indicate that IBV GD is highly virulent, and that QX-like JS may serve as an effective vaccine against the threat posed by IBV TW-like viruses.