Induction of IL-6 and CCL5 (RANTES) in human respiratory epithelial (A549) cells by clinical isolates of respiratory syncytial virus is strain specific

Abstract

BackgroundRespiratory syncytial virus (RSV) is the major respiratory pathogen of infants and young children. During each seasonal epidemic, multiple strains of both subgroup A and B viruses circulate in the community. Like other RNA viruses, RSV genome replication is prone to errors that results in a heterogeneous population of viral strains some of which may possess differences in virulence. We sought to determine whether clinical isolates of RSV differ in their capacity to induce inflammatory cytokines IL-6 and CCL5 (previously known as RANTES [regulated upon activation, normal T-cell expressed and secreted protein]), which are known to be induced in vitro and in vivo in response to RSV, during infection of A549 cells.ResultsScreening of subgroup A and B isolates revealed heterogeneity among strains to induce IL-6 and CCL5. We chose two subgroup B strains, New Haven (NH)1067 and NH1125, for further analysis because of their marked differences in cytokine inducing properties and because subgroup B strains, in general, are less genetically heterogeneous as compared to subgroup A strains. At 12 and 24 hours post infection RSV strains, NH1067 and NH1125 differed in their capacity to induce IL-6 by an order of magnitude or more. The concentrations of IL-6 and CCL5 were dependent on the dose of infectious virus and the concentration of these cytokines induced by NH1125 was greater than that of those induced by NH1067 when the multiplicity of infection of NH1067 used was as much as 10-fold higher than that of NH1125. The induction of IL-6 was dependent on viable virus as infection with UV-inactivated virus did not induce IL-6. The difference in IL-6 induction most likely could not be explained by differences in viral replication kinetics. The intracellular level of RSV RNA, as determined by quantitative RT-PCR, was indistinguishable between the 2 strains though the titer of progeny virus produced by NH1125 was greater than that produced by NH1067 at 16, 24 and 36 hours but essentially equal at 48 and 72 hours. Full genome sequencing of the 2 strains revealed 193 polymorphisms and 4 insertions in NH1067when compared to NH1125 (2 single base insertions in non-coding regions and 2 duplications of 3 and 60 bases in the RSV G gene). Of the polymorphisms, 147 occurred in coding regions and only 30 resulted in amino acid changes in 7 of the RSV genes.ConclusionsThese data suggest that RSV strains may not be homogeneous with regard to pathogenesis or virulence. Identification of the genetic polymorphisms associated with variations in cytokine induction may lead to insights into RSV disease and to the development of effective antiviral agents and vaccines.

Increased expression of Interleukin-6 related to nephritis in chickens challenged with an Avian infectious bronchitis virus variant

“…This may be similar to what has been proposed for RSV, suggesting that the induction of pro-inflammatory cytokines relates to genetic polymorphisms of the virus (Levitz1 et al 2012). The IBV/Brazil/PR05 strain is a S1 variant IBV, and regarding the results presented herein, it's nephropathogenic and the induction of IL-6 may be related to genetic variation of the S1 gene and its consequent induction of proinflammatory cytokines, agreeing with other studies using models of RNA virus (Hornsleth et al 1998, Montassier et al 2008, Levitz et al 2012, Montassier et al 2012.…”

A systems-based approach to analyse the host response in murine lung macrophages challenged with respiratory syncytial virus

“…Although recent evidence suggests that circulating RSV strains exhibit slow rates of evolution [58], they may also differ in their capacity to induce pro-inflammatory cytokines [49]. Our analysis of the infected lung macrophage cells indicates a sustained pro-inflammatory cytokine response in the absence of productive infection.…”

“…Disease severity due to RSV infection is likely to be partly determined by a combination of the genetic characteristics of the host [48] and the capacity of different RSV strains to induce pro-inflammatory cytokines[49]. In addition RSV can cause a persistent infection in susceptible hosts correlating with prolonged disease symptoms [50].…”

Novel Atlantic bottlenose dolphin parainfluenza virus TtPIV-1 clusters with bovine PIV-3 genotype B strains

“…The L protein was aligned using ClustalW. Accession numbers for all isolates used can be found within the materials and methods section of the paper to elevated CXCL8 levels in PIV infection in vitro, which may explain the elevated CXCL8 levels across all three viruses we observed here [15,41]. It has been shown that in A549 cells, specifically, HPIV-3 induced high levels of CXCL8 [42].…”

“…In addition, IL-6 plays a pivotal role in bridging innate and acquired immune responses [11]. Since IL-1b, IL-6, and CXCL8 are secreted at high levels during respiratory viral infections, their induction likely contributes to the pathophysiology seen in patients [3,8,[12][13][14][15].…”