Bacteria and bacterial envelope components enhance mammalian reovirus thermostability

Abstract

Enteric viruses encounter diverse environments as they migrate through the gastrointestinal tract to infect their hosts. The interaction of eukaryotic viruses with members of the host microbiota can greatly impact various aspects of virus biology, including the efficiency with which viruses can infect their hosts. Mammalian orthoreovirus, a human enteric virus that infects most humans during childhood, is negatively affected by antibiotic treatment prior to infection. However, it is not known how components of the host microbiota affect reovirus infectivity. In this study, we show that reovirus virions directly interact with Gram positive and Gram negative bacteria. Reovirus interaction with bacterial cells conveys enhanced virion thermostability that translates into enhanced attachment and infection of cells following an environmental insult. Enhanced virion thermostability was also conveyed by bacterial envelope components lipopolysaccharide (LPS) and peptidoglycan (PG). Lipoteichoic acid and N-acetylglucosamine-containing polysaccharides enhanced virion stability in a serotype-dependent manner. LPS and PG also enhanced the thermostability of an intermediate reovirus particle (ISVP) that is associated with primary infection in the gut. Although LPS and PG alter reovirus thermostability, these bacterial envelope components did not affect reovirus utilization of its proteinaceous cellular receptor junctional adhesion molecule-A or cell entry kinetics. LPS and PG also did not affect the overall number of reovirus capsid proteins σ1 and σ3, suggesting their effect on virion thermostability is not mediated through altering the overall number of major capsid proteins on the virus. Incubation of reovirus with LPS and PG did not significantly affect the neutralizing efficiency of reovirus-specific antibodies. These data suggest that bacteria enhance reovirus infection of the intestinal tract by enhancing the thermal stability of the reovirus particle at a variety of temperatures through interactions between the viral particle and bacterial envelope components.

Enhanced Killing of Triple-Negative Breast Cancer Cells by Reassortant Reovirus and Topoisomerase Inhibitors

“…Reovirus infectivity was assessed by indirect immunofluorescence (90). MDA-MB-231 and L929 cells were adsorbed with reovirus at a range of MOIs for 1 h at room temperature, washed with PBS, and incubated in media for 16-24 h at 37°C.…”

Virus interactions with bacteria: Partners in the infectious dance

“…It is not known if the same binding site is used by poliovirus to bind LPS and PG. Reovirus virions and cell entry intermediates (infectious subvirion particles [ISVPs]) are stabilized by LPS and PG, suggesting the virus binds LPS and PG through the viral attachment fiber σ1 [9]. In contrast to poliovirus VP1, which intimately interacts with other capsid proteins [19], reovirus σ1 is a fibrous protein that protrudes up to 40 nm from the virion surface [20].…”

“…Enteric viruses use components of the bacterial envelope to enhance virion stability. Direct binding to gram-positive and gram-negative bacteria enhances the thermostability of poliovirus [10], Coxsackievirus B3 [5], HNoV [7,8], and reovirus [9], whereas the thermostability of Mengo and Aichi picornaviruses is strengthened by gram-positive and gram-negative bacteria, respectively [5]. Interestingly, both gram-positive and gram-negative bacteria also provide protection from bleach treatment to Aichi, Mengo, and poliovirus [5].…”

“…In the case of reovirus, the attachment fiber σ1 undergoes conformational changes following binding to sialic acid [25]. Although bacteria or bacterial components do not impact reovirus attachment to cells [9], the interaction with bacteria or envelope components may promote a more thermostable σ1 conformation.…”

The reovirus μ1 protein contributes to the environmental stability of virions

“…During cell entry, virions are proteolytically disassembled to generate a metastable intermediate, called infectious subviral particle (ISVP) (17, 26–33). The viral and environmental factors that influence ISVP stability have been thoroughly investigated (38, 41, 47–52, 54–67). Notably, heat induces loss of infectivity, which is accompanied by a conformational change within the μ1 outer capsid protein (48).…”