Modulation of viral replication in macrophages persistently infected with the DA strain of Theiler's murine encephalomyelitis virus

Influenza virus replication in macrophages: balancing protection and pathogenesis

Macrophages are essential for protection against influenza A virus infection, but are also implicated in the morbidity and mortality associated with severe influenza disease, particularly during infection with highly pathogenic avian influenza (HPAI) H5N1 virus. While influenza virus infection of macrophages was once thought to be abortive, it is now clear that certain virus strains can replicate productively in macrophages. This may have important consequences for the antiviral functions of macrophages, the course of disease and the outcome of infection for the host. In this article, we review findings related to influenza virus replication in macrophages and the impact of productive replication on macrophage antiviral functions. A clear understanding of the interactions between influenza viruses and macrophages may lead to new antiviral therapies to relieve the burden of severe disease associated with influenza viruses.

Infectious bronchitis corona virus establishes productive infection in avian macrophages interfering with selected antimicrobial functions

Infectious bronchitis virus (IBV) causes respiratory disease leading to loss of egg and meat production in chickens. Although it is known that macrophage numbers are elevated in the respiratory tract of IBV infected chickens, the role played by macrophages in IBV infection, particularly as a target cell for viral replication, is unknown. In this study, first, we investigated the ability of IBV to establish productive replication in macrophages in lungs and trachea in vivo and in macrophage cell cultures in vitro using two pathogenic IBV strains. Using a double immunofluorescent technique, we observed that both IBV Massachusetts-type 41 (M41) and Connecticut A5968 (Conn A5968) strains replicate in avian macrophages at a low level in vivo. This in vivo observation was substantiated by demonstrating IBV antigens in macrophages following in vitro IBV infection. Further, IBV productive infection in macrophages was confirmed by demonstrating corona viral particles in macrophages and IBV ribonucleic acid (RNA) in culture supernatants. Evaluation of the functions of macrophages following infection of macrophages with IBV M41 and Conn A5968 strains revealed that the production of antimicrobial molecule, nitric oxide (NO) is inhibited. It was also noted that replication of IBV M41 and Conn A5968 strains in macrophages does not interfere with the induction of type 1 IFN activity by macrophages. In conclusion, both M41 and Con A5968 IBV strains infect macrophages in vivo and in vitro resulting productive replications. During the replication of IBV in macrophages, their ability to produce NO can be affected without affecting the ability to induce type 1 IFN activity. Further studies are warranted to uncover the significance of macrophage infection of IBV in the pathogenesis of IBV infection in chickens.

Phosphatidylinositol 4-kinases: hostages harnessed to build panviral replication platforms

Several RNA viruses have recently been shown to hijack members of the host phosphatidylinositol (PtdIns) 4-kinase (PI4K) family of enzymes. They use PI4K to generate membranes enriched in phosphatidylinositide 4-phosphate (PtdIns4P or PI4P) lipids, which can be used as replication platforms. Viral replication machinery is assembled on these platforms as a supramolecular complex and PtdIns4P lipids regulate viral RNA synthesis. This article highlights these recent studies on the regulation of viral RNA synthesis by PtdIns4P lipids. It explores the potential mechanisms by which PtdIns4P lipids can contribute to viral replication and discusses the therapeutic potential of developing antiviral molecules that target host PI4Ks as a form of panviral therapy.

Cytokine/chemokine profile in J774 macrophage cells persistently infected with DA strain of Theiler's murine encephalomyelitis virus (TMEV)

Theiler's murine encephalomyelitis virus (TMEV) is a picornavirus and persists in the spinal cords of mice, followed by inflammatory demyelinating disease. Viral persistence is a key determinant for the TMEV-induced demyelination. Macrophages are thought to serve as the site of TMEV persistence during the chronic demyelinating phase. We previously demonstrated that two nonstructural proteins of TMEV, L and L(*), were important for virus growth in J774.1 macrophage cells. However, the key factors of macrophage cells related to virus persistence and demyelination remain poorly understood. The inflammatory response is heavily dependent on cytokine and chemokine production by cell of both the immune system and the central nervous system (CNS). In this study, we established the macrophage cells persistently infected with DA strain, and then analyzed the cytokine expression pattern in those cells. The present results are the first to demonstrate the up-regulation of B-lymphocyte chemoattractant (BLC) and granulocyte colony-stimulating factor (G-CSF) in the macrophage cells persistently infected with DA strain. Furthermore, up-regulation of interleukin (IL)-10 and down-regulation of interferon (IFN)-alpha 4, IFN-beta, and IFN-gamma were shown in those cells. The data suggest that these cytokines/chemokines may contribute to the virus persistence and the acceleration of TMEV-induced demyelination.

Immune effects observed after the injection of plasmids coding for rainbow trout (Oncorhynchus mykiss) CK5B, CK6 and CK7A chemokines demonstrate their immunomodulatory capacity and reveal CK6 as a major interferon inducer

In the current study, we have determined the immune effects of the intramuscular injection of eukaryotic expression plasmids coding for rainbow trout (Oncorhynchus mykiss) CK5B, CK6 or CK7A CC chemokines (pCK5B, pCK6 and pCK7A) as a first step towards the establishment of their biological role. We have studied the levels of expression of several immune genes in the spleen and head kidney by real-time PCR in comparison to the levels observed in animals injected with the empty plasmid. Concerning the levels of expression of these CC chemokines and the CXC chemokine, interleukin 8 (IL-8), each plasmid induced up-regulation on expression levels of its coded chemokine in the head kidney and spleen, but also affected the expression of other chemokines. Both pCK6 and pCK7A induced the expression of the other two CC chemokines, while pCK5B induced CK7A but not CK6. Both pCK5B and pCK7A induced IL-8 as well. pCK6 was the only plasmid that induced IL-1beta in the head kidney, whereas in the spleen, this occurred only with pCK5B. Different effects on the head kidney and spleen were also visible for tumour necrosis factor alpha (TNF-alpha), since the three plasmids induced this cytokine in the head kidney, but only pCK5B and pCK6 in the spleen. Concerning the effects on type I interferon (IFN), again pCK6 induced the strongest enhancement in the head kidney, while in the spleen it was pCK5B. However, the levels of expression of the Mx gene, know to be induced by type I IFN correlated with the CK6-induced IFN levels in the head kidney, but not with the CK5B-induced IFN in head kidney or spleen, suggesting an inhibition of Mx mRNA levels independent of IFN due to CK5B. The clear effect of pCK6 on the levels of expression of IFN-gamma and its strong effects on type I IFN, in contrast with its recent adscription to the CCL17/22 group linked to Th2 responses, were verified by studying the in vitro effects of recombinant CK6 on head kidney leukocytes. Again in this case, recombinant CK6 strongly induced type I IFN, Mx and IFN-gamma to a lesser extent, revealing CK6 as a potent IFN inducer in contrast to its mammalian homologues. Finally, effects on major histocompatibility complex (MHC)-IIalpha, CD4 and CD8alpha expression demonstrate that the three chemokines are able to mobilize antigen-presenting cells, CD4(+) and CD8(+) lymphocytes.