The pandemic spread of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the etiological agent of Coronavirus Disease 2019 (COVID-19), represents an ongoing international health crisis. A key symptom of SARS-CoV-2 infection is the onset of fever, with a hyperthermic temperature range of 38 to 41°C. Fever is an evolutionarily conserved host response to microbial infection that can influence the outcome of viral pathogenicity and regulation of host innate and adaptive immune responses. However, it remains to be determined what effect elevated temperature has on SARS-CoV-2 replication. Utilizing a three-dimensional (3D) air–liquid interface (ALI) model that closely mimics the natural tissue physiology of SARS-CoV-2 infection in the respiratory airway, we identify tissue temperature to play an important role in the regulation of SARS-CoV-2 infection. Respiratory tissue incubated at 40°C remained permissive to SARS-CoV-2 entry but refractory to viral transcription, leading to significantly reduced levels of viral RNA replication and apical shedding of infectious virus. We identify tissue temperature to play an important role in the differential regulation of epithelial host responses to SARS-CoV-2 infection that impact upon multiple pathways, including intracellular immune regulation, without disruption to general transcription or epithelium integrity. We present the first evidence that febrile temperatures associated with COVID-19 inhibit SARS-CoV-2 replication in respiratory epithelia. Our data identify an important role for tissue temperature in the epithelial restriction of SARS-CoV-2 independently of canonical interferon (IFN)-mediated antiviral immune defenses.

Two cats from different COVID-19-infected households in the UK were found to be infected with SARS-CoV-2 from humans, demonstrated by immunofluorescence, in situ hybridisation, reverse transcriptase quantitative PCR and viral genome sequencing. Lung tissue collected post-mortem from cat 1 displayed pathological and histological findings consistent with viral pneumonia and tested positive for SARS-CoV-2 antigens and RNA. SARS-CoV-2 RNA was detected in an oropharyngeal swab collected from cat 2 that presented with rhinitis and conjunctivitis. High throughput sequencing of the virus from cat 2 revealed that the feline viral genome contained five single nucleotide polymorphisms (SNPs) compared to the nearest UK human SARS-CoV-2 sequence. An analysis of cat 2’s viral genome together with nine other feline-derived SARS-CoV-2 sequences from around the world revealed no shared catspecific mutations. These findings indicate that human-to-cat transmission of SARS-CoV-2 occurred during the COVID-19 pandemic in the UK, with the infected cats developing mild or severe respiratory disease. Given the versatility of the new coronavirus, it will be important to monitor for human-to-cat, cat-to-cat and cat-to-human transmission.

The primary envelopment/de-envelopment of Herpes viruses during nuclear exit is poorly understood. In Herpes simplex virus type-1 (HSV-1), proteins pUL31 and pUL34 are critical, while pUS3 and some others contribute; however, efficient membrane fusion may require additional host proteins. We postulated that vesicle fusion proteins present in the nuclear envelope might facilitate primary envelopment and/or de-envelopment fusion with the outer nuclear membrane. Indeed, a subpopulation of vesicle-associated membrane protein-associated protein B (VAPB), a known vesicle trafficking protein, was present in the nuclear membrane co-locating with pUL34. VAPB knockdown significantly reduced both cell-associated and supernatant virus titers. Moreover, VAPB depletion reduced cytoplasmic accumulation of virus particles and increased levels of nuclear encapsidated viral DNA. These results suggest that VAPB is an important player in the exit of primary enveloped HSV-1 virions from the nucleus. Importantly, VAPB knockdown did not alter pUL34, calnexin or GM-130 localization during infection, arguing against an indirect effect of VAPB on cellular vesicles and trafficking. Immunogold-labelling electron microscopy confirmed VAPB presence in nuclear membranes and moreover associated with primary enveloped HSV-1 particles. These data suggest that VAPB could be a cellular component of a complex that facilitates UL31/UL34/US3-mediated HSV-1 nuclear egress.

Hyperthermia is a well-accepted cancer therapy. Microwaves provide a very precise, targeted means of hyperthermia and are currently used to treat plantar warts caused by cutaneous-infective human papillomaviruses (HPVs). Other HPV genotypes infecting the anogenital mucosa cause genital warts or preneoplastic lesions or cervical cancer. Effective, non-ablative therapies for these morbid HPV-associated lesions are lacking. The molecular consequences of microwave treatment were investigated in in vitro cultured three-dimensional HPV-positive cervical tumour tissues, and tissues formed from HPV-infected normal immortalised keratinocytes. Microwave energy delivery to tissues was quantified. Quantitative reverse transcriptase PCR was used to quantify mRNA expression. Immunohistochemistry and fluorescence immunostaining was used to assess protein expression. Microwave energy deposition induced sustained, localised cell death at the treatment site. There was a downregulation in levels of HPV oncoproteins E6 and E7 alongside a reduction in cellular growth/proliferation and induction of apoptosis/autophagy. HSP70 expression confirmed hyperthermia, concomitant with induction of translational stress. The data suggest that microwave treatment inhibits tumour cell proliferation and allows the natural apoptosis of HPV-infected cells to resume. Precision microwave delivery presents a potential new treatment for treating HPV-positive anogenital precancerous lesions and cancers. Funding was through an Innovate UK Biomedical Catalyst grant (ID# 92138-556187), a Chief Scientist Office grant (TCS/19/11) and core support from Medical Research Council (MC_ UU_12014) core funding for the MRC-University of Glasgow Centre for Virus Research.

The pandemic spread of SARS-CoV-2, the etiological agent of COVID-19, represents a significant and ongoing international health crisis. A key symptom of SARS-CoV-2 infection is the onset of fever, with a hyperthermic temperature range of 38 to 41°C. Fever is an evolutionarily conserved host response to microbial infection and inflammation that can influence the outcome of viral pathogenicity and regulation of host innate and adaptive immune responses. However, it remains to be determined what effect elevated temperature has on SARS-CoV-2 tropism and replication. Utilizing a 3D air-liquid interface (ALI) model that closely mimics the natural tissue physiology and cellular tropism of SARS-CoV-2 infection in the respiratory airway, we identify tissue temperature to play an important role in the regulation of SARS-CoV-2 infection. We show that temperature elevation induces wide-spread transcriptome changes that impact upon the regulation of multiple pathways, including epigenetic regulation and lncRNA expression, without disruption of general cellular transcription or the induction of interferon (IFN)-mediated antiviral immune defences. Respiratory tissue incubated at temperatures >37°C remained permissive to SARS-CoV-2 infection but severely restricted the initiation of viral transcription, leading to significantly reduced levels of intraepithelial viral RNA accumulation and apical shedding of infectious virus. To our knowledge, we present the first evidence that febrile temperatures associated with COVID-19 inhibit SARS-CoV-2 replication. Our data identify an important role for temperature elevation in the epithelial restriction of SARS-CoV-2 that occurs independently of the induction of canonical IFN-mediated antiviral immune defences and interferon-stimulated gene (ISG) expression.

Fever is an evolutionary conserved host pro-inflammatory immune response that governs the regulation of multiple biological processes to control the outcome of infection. In January 2022, the World Health Organization (WHO) reported a global outbreak in mpox cases with a high incidence of human-to-human transmission. A frequent prodromal symptom of monkeypox virus (MPXV) infection is fever, with a febrile temperature range of 38.3 to 40.5 °C. However, the outcome of temperature elevation on MPXV infection remains poorly defined. Here, we isolated a circulating strain of MPXV from a patient who presented with fever (38.5 °C) and rash from the 2022 outbreak. Genomic sequencing identified this isolate to belong to the epidemic Clade IIb.B1. Transcriptomic analysis of infected cells demonstrated this virus to induce a strong IL6 pro-inflammatory immune response, consistent with a role for this pyrogen in the regulation of fever. We identify host-cell temperature at both physiological skin (33 °C) and clinical febrile temperatures (38.5 and 40 °C) to be a key determinant in the outcome of infection through the differential regulation of MPXV transcription and associated amplitude of host cytokine response to infection. Incubation of infected cells at 38.5 or 40 °C led to a restriction or ablation in MPXV replication, respectively. Importantly, this thermal inhibition was reversible upon temperature downshift to 37 °C without detriment to viral replication fitness. Co-stimulation of the type-I interferon (IFN) response led to a dose- and temperature-dependent inhibition in MPXV replication that restricted the re-establishment of infection upon temperature downshift and withdrawal of IFN as an immune stimulus. Our data identify febrile temperatures associated with mpox disease to be a critical component of the host pro-inflammatory immune response to infection which can synergise with the type-I IFN response to enhance the host-cell mediated restriction of MPXV.