Immunobiotic Lactobacillus administered post-exposure averts the lethal sequelae of respiratory virus infection

Abstract

We reported previously that priming of the respiratory tract with immunobiotic Lactobacillus prior to virus challenge protects mice against subsequent lethal infection with pneumonia virus of mice (PVM). We present here the results of gene microarray which document differential expression of proinflammatory mediators in response to PVM infection alone and those suppressed in response to Lactobacillus plantarum. We also demonstrate for the first time that intranasal inoculation with live or heat-inactivated L. plantarum or Lactobacillus reuteri promotes full survival from PVM infection when administered within 24 h after virus challenge. Survival in response to L. plantarum administered after virus challenge is associated with suppression of proinflammatory cytokines, limited virus recovery, and diminished neutrophil recruitment to lung tissue and airways. Utilizing this post-virus challenge protocol, we found that protective responses elicited by L. plantarum at the respiratory tract were distinct from those at the gastrointestinal mucosa, as mice devoid of the anti-inflammatory cytokine, interleukin (IL)-10, exhibit survival and inflammatory responses that are indistinguishable from those of their wild-type counterparts. Finally, although L. plantarum interacts specifically with pattern recognition receptors TLR2 and NOD2, the respective gene-deleted mice were fully protected against lethal PVM infection by L. plantarum, as are mice devoid of type I interferon receptors. Taken together, L. plantarum is a versatile and flexible agent that is capable of averting the lethal sequelae of severe respiratory infection both prior to and post-virus challenge via complex and potentially redundant mechanisms.

Immortalized MH-S cells lack defining features of primary alveolar macrophages and do not support mouse pneumovirus replication

“…Cytoplasmic NOD2 senses muramyl-dipeptide, a metabolite of extracellular bacterial peptidoglycan [41, 42], and can generate inflammatory responses that have been best characterized at the gastrointestinal mucosa [43]. We have also identified NOD2, along with TLR2, as the two principal receptors interacting with Lactobacillus at the respiratory mucosa [23; T. A. Rice, T. A. Brenner, et al , ms in preparation] suggesting that this PRR is of broad interest to the study of host-microbe interactions, including those mediated by AMs.…”

“…Using recombinant PVM (rK2-PVM) which incorporates the sequence encoding the far-red fluorescent protein, mKATE2, we have recently shown that AMs are a primary leukocyte target for this virus, and that AMs support both virus replication and productive infection in vivo [19]. Furthermore, application of immunobiotic Lactobacillus species to the respiratory tract, a regimen that results in robust and sustained survival in response to virus infection [20 – 23] limits PVM infection and virion release from AMs [19]. …”

Signaling via pattern recognition receptors NOD2 and TLR2 contributes to immunomodulatory control of lethal pneumovirus infection

“…However, and surprisingly, we found that Lp -mediated protection against lethal PVM infection was maintained in both TLR2 −/− and NOD2 −/− single gene-deleted mice (Percopo et al , 2015). Here, we utilize both NOD2 −/− TLR2 −/− double gene-deleted mice and a novel NOD2-TLR2 bifunctional ligand to demonstrate that the coordinate engagement of these PRRs contributes substantially to survival in response to an acute respiratory virus infection as well as to suppression of virus-induced inflammation.…”

“…Our group has shown that L. plantarum ( Lp ), both live and heat-inactivated (in the latter form as a paraprobiotic (Taverniti & Guglielmetti, 2011)), when administered directly to the respiratory tract, results in robust and sustained protection against the lethal sequelae of PVM infection. We have shown that Lp is not primarily an antiviral agent (Gabryszewski et al , 2011); the beneficial impact of Lp -administration is primarily via suppression of local inflammation (Gabryszewski et al , 2011; Garcia-Crespo et al , 2013; Percopo et al , 2014; Percopo et al , 2015). Lactobacillus -mediated protection against respiratory virus infection is a profound example of heterologous immunity (also known in other contexts as trained immunity or innate memory (Levy & Netea, 2014; Netea et al , 2011; Wissinger et al , 2009; Locati et al , 2013; van der Meer et al , 2015) a state in which a host’s interaction with a primary infectious or inflammatory stimulus alters the immune response to a distinct, or unrelated agent.…”

Priming of the Respiratory Tract with ImmunobioticLactobacillus plantarumLimits Infection of Alveolar Macrophages with Recombinant Pneumonia Virus of Mice (rK2-PVM)

“…Lactobacillus-mediated priming of the respiratory tract also results in the profound suppression of a specific subset of proinflammatory cytokines (20,68), which may alter the responses of AMs in vivo (and perhaps not ex vivo, as discussed further below).…”