The sulphated polysaccharides extract ulvans from Ulva armoricana limits Marek's disease virus dissemination in vitro and promotes viral reactivation in lymphoid cells

Immunopotentiating effect of lentinan on chicks and its inhibitory effect on Marek's disease virus infection

Marek's disease virus (MDV) is a significant tumorigenic virus that causes severe immunosuppression in chickens. Lentinan (LNT) is an immunomodulator containing β-glucans and is widely used in areas such as antiviral, anticancer, and immune regulation. To investigate the immunomodulatory effects of LNT on specific pathogen-free (SPF) chicks and its potential to inhibit MDV infection, we conducted an MDV challenge experiment and observed the immune-enhancing effect of LNT on SPF chicks. The results showed that LNT promoted the growth and development of SPF chicks and induced the upregulation of cytokines such as Mx protein, interferon-γ (INF-γ), tumor necrosis factor-α (TNF-α), and interleukin-2 (IL-2). The specific gravity of CD4+ T-lymphocytes and CD8+ T-lymphocytes and their ratios were also significantly upregulated. Prophylactic use of LNT inhibited MDV replication in lymphocytes, liver, and spleen. It also alleviated MDV-induced weight loss and hepatosplenomegaly in SPF chicks. The present study confirms that LNT can enhance the levels of innate and cellular immunity in SPF chicks and contributes to the inhibition of MDV replication in vivo and mitigation of immune organ damage in chicks due to MDV infection. This provides an adjunctive measure for better control of MDV infection.

Immune escape of avian oncogenic Marek's disease herpesvirus and antagonistic host immune responses

Marek's disease virus (MDV) is a highly pathogenic and oncogenic alpha herpesvirus that causes Marek's disease (MD), which is one of the most important immunosuppressive and rapid-onset neoplastic diseases in poultry. The onset of MD lymphomas and other clinical diseases can be efficiently prevented by vaccination; these vaccines are heralded as the first demonstration of a successful vaccination strategy against a cancer. However, the persistent evolution of epidemic MDV strains towards greater virulence has recently resulted in frequent outbreaks of MD in vaccinated chicken flocks worldwide. Herein, we provide an overall review focusing on the discovery and identification of the strategies by which MDV evades host immunity and attacks the immune system. We have also highlighted the decrease in the immune efficacy of current MD vaccines. The prospects, strategies and new techniques for the development of efficient MD vaccines, together with the possibilities of antiviral therapy in MD, are also discussed.

Marine-Sulfated Polysaccharides Extracts Exhibit Contrasted Time-Dependent Immunomodulatory and Antiviral Properties on Porcine Monocytes and Alveolar Macrophages

Simple Summary

Algal extracts have a real potential in terms of animal health, strengthening the interest in this natural resource. In pigs, respiratory complex syndrome significantly alters the wellbeing of the animals and threatens the economical sustainability of the sector. In the current study, we assessed various marine-sulfated polysaccharides (MSP^®) extracts on two relevant cell populations in pigs, i.e., porcine monocytes and alveolar macrophages. Then, we analyzed the impact of the extracts on the infections of the cells by two important viruses. A modulation of the inflammatory response as well as some inhibitions of viral replication were observed. The type of effect observed was dependent on the extract, the experiment set-up, and the virus. The results obtained prompt us to further decipher the effects of algal extracts on the porcine health and open the door to future experiments, particularly in vivo experiments.

Abstract

Porcine respiratory complex syndrome has a strong economic impact on the swine breeding sector, as well as a clear repercussion on the wellbeing of the animals, leading to overuse of antimicrobial molecules. Algal extracts used in short-term treatments are empirically recognized by farmers as having a positive effect on pigs’ health, however, their mechanisms of action are not well known and more research is needed. Herein we studied the short and median term impact of three algal extracts, in vitro, on the pro-inflammatory and antiviral responses of porcine primary blood monocytes and alveolar macrophages, as well as the susceptibility of the treated cells to infection by Porcine Respiratory and Reproductive Syndrome Virus (PRRSV) and the Aujeszky’s Disease Virus (ADV). All extracts presented a pro-inflammatory short-term effect, associated for two of them, with an inhibition of the PRRSV replication. Conversely, the three extracts presented an anti-inflammatory median term effect, with no impact on PRRSV replication. The observed immune modulation prompts us to test, in vivo, the anti-PRRSV action of algal extracts and strengthen the interest for this natural resource.