- Volume 106, Issue 10, 2025

A multivalent vaccine targeting high-consequence infectious diseases in Sub-Saharan Africa (SSA), which are linked to high mortality, morbidity and overlapping clinical manifestations, would significantly improve health security and economic stability in this region. Trivalent vector vaccines were devised to deliver digitally optimized versions of Orthoebolavirus, Orthomarburgvirus glycoproteins (GPs) and a Lassa mammarenavirus (LASV) nucleoprotein (NP) by a single Modified Vaccinia Ankara (MVA) known to protect against mpox virus (MPXV) along with a matched DNA vaccine. Three immunizations in mice and Hartley guinea pigs with MVA only or a DNA prime followed by two MVA administrations induced comparable levels of binding antibodies and LASV-specific T-cells, respectively. While DNA priming mitigated MVA-specific antibody responses, GP- and NP-specific antibodies developed already after a single MVA vaccination. Although a post-outbreak Ebola virus vaccine is available, outbreaks by other filoviruses, annual LASV epidemics and increased incidence of MPXV infections support the rationale for an MVA-based trivalent haemorrhagic fever vaccine for endemic and high-risk human populations in SSA.

A erratum of this article has been published full details can be found at https://doi.org/10.1099/jgv.0.002171.

Obesity is a growing global health concern with profound effects on immune function and vaccine efficacy. This study investigated the impact of obesity on immune responses to tick-borne encephalitis virus (TBEV) vaccination and infection using a mouse model. Mice on a high-fat diet (HFD) exhibited increased body weight, fat mass and a pre-diabetic state compared to standard chow diet (SCD) controls. After vaccination with the TBEV vaccine (Encepur), HFD mice showed significantly lower TBEV-specific IgG titres and neutralizing antibody levels compared to SCD mice. Splenocyte counts per organ mass were significantly higher in vaccinated SCD mice compared to their HFD counterparts, correlating with the elevated IgG titres observed in the SCD group. These results underscore the critical role of diet in shaping the immune response and vaccine efficacy. Following TBEV infection, HFD mice did not display increased disease severity or elevated viral titres in the serum, spleen or brain relative to SCD controls, indicating that obesity did not exacerbate viral replication or dissemination. However, a sex-dependent effect of obesity on the humoral immune response was observed. Male HFD mice produced antibody titres comparable to their SCD counterparts, suggesting minimal impact of obesity on their immune response. In contrast, female HFD mice exhibited significant impairments in TBEV-specific IgG and neutralizing antibody production compared to female SCD mice, as well as both male HFD and male SCD groups. These findings highlight a complex interplay between obesity, sex and immune function, with obesity disproportionately impairing the immune response after TBEV vaccination and infection.

Astroviruses are important aetiological agents of gastroenteritis. Recently, two novel human astrovirus (HAstV) clades, VA and MLB, have been identified. However, the replication cycle of these viruses remains poorly characterized. Among these, the novel astrovirus VA1 has been of particular interest due to its reported association with neurological disease in immunocompromised patients. Previous studies have demonstrated that a functional proteasome is essential for the efficient replication of classic HAstVs. In this study, we investigated the role of the proteasome in the replication of HAstV-VA1. We assessed the impact of two proteasome inhibitors, MG132 and bortezomib, on viral replication. Both inhibitors significantly reduced viral protein and infectious progeny production in a dose-dependent manner. Our findings indicate that the inhibitory effects of these compounds are mediated through a mechanism affecting virus entry and a post-entry step in the viral replication cycle during the virus replication cycle.

CM2 is a single-pass transmembrane protein located in the viral envelope and is essential for the growth of influenza C virus. We previously reported that CM2 is involved in viral genome packaging and uncoating. We also demonstrated that alanine substitutions at residues 47–48, 67–69, 73–75, 85–87 and 113–115 in the cytoplasmic domain of CM2 significantly reduced its expression levels. Herein, we analysed whether these mutations affected viral replication. The alanine-substituted recombinant viruses rCM2-Ala67–69, 73–75 and 85–87 exhibited significantly reduced replication compared with recombinant wild-type viruses (rWT), and the amount of CM2 protein in virions and infected cells was also reduced compared with that in rWT. In addition, the amount of viral RNA within the particles of these mutant viruses was significantly lower than that in rWT. Furthermore, the amount of viral RNA-NP complexes transported into the nucleus of infected cells was reduced in rCM2-Ala73–75 and 85–87 viruses. In contrast, recombinant viruses with mutations at positions 113–115 could not be rescued, and virus-like particles containing this mutation showed suppressed genome packaging and uncoating and reduced expression of the CM2 protein. These results suggested that the cytoplasmic region of CM2 contributes to efficient packaging and uncoating of the genome through its stable expression.

Laboratory of genetics and physiology 2 (LGP2, also known as DHX58) is unique among members of the RIG-I-like receptor (RLR) family as it lacks the caspase activation and recruitment domain. Although LGP2 per se cannot directly activate downstream antiviral signalling, it plays important regulatory roles, primarily by modulating innate immune responses mediated by RIG-I and MDA5. However, the detailed mechanisms by which LGP2 is induced in mammalian cells during viral infection remain incompletely understood. Herein, we show that LGP2 is strongly upregulated by dsRNA stimulation or virus infection in cultured human cell lines via TLR3 and RLRs, respectively, and that substantial induction of LGP2 remains when paracrine/autocrine signalling of IFNs and/or inflammatory cytokines is abrogated by genetic deletion or chemical inhibition. The latter observation is in stark contrast to the case of myxovirus resistance proteins, the induction of which is strictly IFN-dependent. Mechanistically, we found LGP2 expression to be upregulated by ectopic expression of IRF3-5D, a phospho-mimetic mutant of activated IRF3, or to a lesser extent, by overexpression of RELA, the p65 subunit of NFκB, in an IFN-independent fashion. Additionally, we demonstrated that this regulation operated transcriptionally at the LGP2 promoter level. Altogether, a fraction of LGP2 induction in viral infection is IFN- and cytokine-independent, highlighting exquisite gene expression control in antiviral innate immunity and representing an evolutionary advantage, which ensures uninterrupted supply of this RLR member protein in host responses to invading viruses in the event that IFN production and/or signalling is disabled by viral means.

Human cytomegalovirus (HCMV) is a ubiquitous human pathogen of high clinical relevance. In terms of pathogenic determination, the regulatory factors of HCMV–host interaction play a crucial role, and recently we reported on virus-supportive functions of the cellular peptidyl-prolyl cis/trans isomerase Pin1. Notably, Pin1 is able to recognize phosphorylated serine/threonine-proline motifs and regulate the structural conformation, stability and function of its substrate proteins. During HCMV replication, Pin1 facilitates viral nuclear egress by inducing site-specific rearrangements of the nuclear lamina through the cis/trans conversion of lamin type A/C. To this end, we developed readout systems to decipher details of HCMV–Pin1 regulatory interaction. Notably, together with primary human foreskin fibroblasts (HFFs) and recombinant lamin-modified cell populations, the molecular mechanisms of Pin1 interaction with both the nuclear lamina and viral proteins were illustrated. Our new results demonstrate the following: (i) currently available Pin1-inhibitory small molecules, similar to the antiviral drug maribavir (MBV), exert an antiviral activity against human and non-human primate cytomegaloviruses (CMVs); (ii) site-specific phosphorylation at serine 22, a Pin1 recognition motif within lamin A/C, is consistently mediated by the pUL97 kinase homologs of these viruses; (iii) the phosphorylation of serine 22 is sensitive to the virus-specific kinase inhibitor MBV; (iv) a doxycycline-inducible expression of autofluorescent lamin A/C-red fluorescent protein (RFP) fusion constructs in HFFs supports the productive HCMV replication; (v) these lamin A/C-RFP reporter cells indicated a virus-induced formation of lamina-depleted areas (LDAs), dependent on serine 22 but independent of the infecting CMV species; and (vi) treatment of CMV-infected cells with kinase or Pin1 inhibitors exerted distinct effects on the magnitude of LDA formation. Combined, the study is consistent with our concept that the mode of nuclear egress shows parallels between human and non-human primate CMVs. Thus, the role of Pin1 may play an important regulatory role in determining virus infection and replication efficiency.

The phosphoprotein 65 (pp65, pUL83) of human cytomegalovirus (HCMV) serves several functions during the viral life cycle. It is one of the most abundant constituents of the virion tegument and the major component of subviral particles termed Dense Bodies. It is also one of several tegument proteins that mediate the subversion of cellular antiviral defence functions like the induction of IFNs. It is also involved in the transcriptional activation of the major immediate early IE1/IE2 gene. Despite its strong nucleophilic nature, pp65 is found in the cytoplasm at late stages of infection. We have previously shown that the nuclear retention phenotype of a mutated pp65 is associated with a distinct deficit in viral productivity. In this study, we generated HCMV mutant viruses in which the nuclear localization signals (nls) of pp65 were mutated, thus preventing nuclear entry and pp65 shuttling. Since the genetic manipulation of UL83 led to the deregulation of the adjacent pp71 gene in initial experiments, we chose to express pp65 with mutated nls from a distant locus within the genome of a TB40/e strain derivative. This virus, termed v65stop-pp65nls, was significantly impaired in its capacity to produce infectious progeny. Using knockout fibroblast cells for the DNA sensors IFI16 or cGAS, no differences were seen when progeny production was compared between v65stop-pp65nls and a strain expressing wt pp65. Thus, differences in the known subversive effect on these DNA sensors could not account for the differences seen in productivity. Surprisingly, the upload of pp65 into virions and the synthesis of subviral Dense Bodies were abrogated by the mutation of its nls. Although an impairment of pp65 interaction with other proteins by the mutations cannot be excluded, the data suggest that the migration of pp65 through the nucleus was important for HCMV progeny production and packaging.