Methods for studying antiviral functions of macrophages and mononuclear phagocytes

Current status and evolving approaches to African swine fever vaccine development

African swine fever (ASF) is a highly lethal haemorrhagic disease of swine caused by African swine fever virus (ASFV), a unique and genetically complex virus. The disease continues to be a huge burden to the pig industry in Africa, Europe and recently in Asia, especially China. The purpose of this review was to recapitulate the current scenarios and evolving trends in ASF vaccine development. The unavailability of an applicable ASF vaccine is partly due to the complex nature of the virus, which encodes various proteins associated with immune evasion. Moreover, the incomplete understanding of immune protection determinants of ASFV hampers the rational vaccine design. Developing an effective ASF vaccine continues to be a challenging task due to many undefined features of ASFV immunobiology. Recent attempts on DNA and live attenuated ASF vaccines have been reported with promising efficacy, and especially live attenuated vaccines have been proved to provide complete homologous protection. Single-cycle viral vaccines have been developed for various diseases such as Rift Valley fever and bluetongue, and the rational extension of these strategies could be helpful for developing single-cycle ASF vaccines. Therefore, live attenuated vaccines in short term and single-cycle vaccines in long term would be the next generation of ASF vaccines.

Bacillus alcalophilus peptidoglycan induces IFN-alpha-mediated inhibition of vaccinia virus replication

Bacterial products such as cell walls (CW) and peptidoglycan (PGN) are known to activate macrophages and NK cells during microbial infections. In this report, we demonstrated that whole CW and PGN of four Gram-positive bacteria are capable of enhancing the anti-poxviral activity of murine macrophage RAW 264.7 cells. Among the major Bacillus alcalophilus CW components, PGN contributes the most to antiviral activity and induces remarkably higher levels of IFN-alpha. Anti-IFN-alpha/beta antibody, but not anti-IFN-gamma, anti-IFN-gamma receptor, or anti-IL-12, reversed the PGN-induced inhibition of vaccinia virus replication and reduced nitric oxide (NO) production. Our data thus suggest that PGN induce antiviral activity through IFN-alpha and to a lesser extent, through NO production.

Bovine respiratory syncytial virus replicates minimally in bovine alveolar macrophages

The interaction between two different bovine respiratory syncytial virus (BRSV) strains and bovine alveolar macrophages (BAMs) was studied in vitro. Bovine respiratory syncytial virus replicated minimally in BAMs and most of the virus produced remained cell-associated. Approximately 1 out of 1,000 BAMs produced infectious virus, a number that further declined during the 7 days of culture. In contrast, BAMs exposed to bovine parainfluenza 3 virus (PI3V) produced high amounts of infectious virus. The number of BAMs that contained BRSV antigen depended on the antigen load of the inoculum and not on the infectivity of the virus. Antibody mediated enhancement of infection was not detected. It is concluded that bovine alveolar macrophages exhibit a high intrinsic resistance to BRSV, but not to PI3V.