Microbes have been coevolving with their host for millions of years, exploiting host resources to their own benefit. We show that viral and bacterial pathogens convergently evolved to hijack cellular mitogen-activated protein kinase (MAPK) p90-ribosomal S6-kinases (RSKs). Theiler’s virus leader (L) protein binds RSKs and prevents their dephosphorylation, thus maintaining the kinases active. Recruitment of RSKs enables L-protein-mediated inhibition of eukaryotic translation initiation factor 2 alpha kinase 2 (EIF2AK2 or PKR) and stress granule formation. Strikingly, ORF45 protein of Kaposi’s sarcoma-associated herpesvirus (KSHV) and YopM protein of Yersinia use the same peptide motif as L to recruit and activate RSKs. All three proteins interact with a conserved surface-located loop of RSKs, likely acting as an allosteric regulation site. Some unrelated viruses and bacteria thus evolved to harness RSKs in a common fashion, yet to target distinct aspects of innate immunity. As documented for Varicella zoster virus ORF11, additional pathogens likely evolved to hijack RSKs, using a similar short linear motif. Significance Successful microbial infections typically involve the subversion of host immune pathways by pathogen-specific virulence factors. Here, we uncovered that viruses and bacteria independently evolved effectors targeting the same conserved loop of the mitogen-activated protein kinase (MAPK) p90-ribosomal S6-kinases (RSKs). Kinase usurpation relies on a previously unidentified short linear motif (SLiM) shared by these virulence factors. Mechanistically, RSK kinase binding prevents its dephosphorylation, thus promoting its phosphorylating activity. Remarkably, while viruses and bacteria evolved an identical mechanism of kinase activation, downstream effect diverged, effectively disarming different arms of the immune system according to their own need. This is a prominent illustration of trans-kingdom convergent evolution across microbial pathogens to usurp key signaling kinases.

Hepatitis E virus is a prominent cause of viral hepatitis worldwide. In Western countries, most infections are asymptomatic. However, acute self-limiting hepatitis and chronic cases in immunocompromised individuals can occur. Studying HEV is challenging due to its difficulty to grow in cell culture. Consequently, the detection of the virus mainly relies on RT-qPCR, which cannot differentiate between infectious and non-infectious particles. To overcome this problem, methods assessing viral integrity offer a possible solution to differentiate between intact and damaged viruses. This study aims at optimizing existing HEV cell culture models and RT-qPCR-based assays for selectively detecting intact virions to establish a reliable model for assessing HEV infectivity. In conclusion, these newly developed methods hold promise for enhancing food safety by identifying approaches for inactivating HEV in food processing, thereby increasing food safety measures.

Hepatitis E virus (HEV) is an emerging foodborne pathogen in Europe, primarily associated with the consumption of pork products. While conventional destructive TRIzol extraction methods followed by RT-qPCR can detect HEV RNA in processed meat, this approach fails to distinguish between infectious and inactivated virus, complicating risk assessment. Currently, no standardized method exists for extracting intact, infectious HEV from pork products, limiting our ability to evaluate viral infectivity post-processing. In this study, we developed and evaluated three extraction methods to recover intact, infectious HEV from pork meat products. Our optimized soft extraction method using TGBE buffer and stomacher-based homogenization allowed us to successfully isolate infectious HEV from pork liver pâté bought in a Belgian supermarket, confirming the presence of infectious HEV in a ready-to-eat pâté intended for direct consumer consumption. Furthermore, viral RNA was detected following extraction with this method at concentrations (copies/g) similar to those obtained with the TRIzol method, while preserving viral integrity, as confirmed by capsid integrity assays and cell culture infectivity models. As a critical tool for assessing the impact of food processing on viral infectivity, the method holds significant potential for advancing food safety research and improving risk evaluations related to HEV transmission through pork products.

Pneumococcal infections caused by Streptococcus pneumoniae remain a leading cause of vaccine-preventable morbidity and mortality worldwide, particularly among older adults and individuals with immu...