Angela L. Rasmussen

Mpox (formerly monkeypox) is caused by monkeypox virus (MPXV) and has prompted two recent global health emergencies. Clade IIb MPXV, a recently recognized subclade, has been associated with oral and genital lesions and transmission among men who have sex with men (MSM); however, mechanisms of genital pathogenesis and sexual transmission are not understood. We investigated several routes of MPXV Clade IIb virus infection (intranasal, oral, anal, and intraperitoneal) and found high and prolonged viral titres in the testes after IP inoculation still detectable at 21 days. The testes had significant changes to tissue architecture including loss of spermatogenesis, disorganization of spermatozoa, loss of Leydig cells, and breakdown of the seminiferous tubule membranes. Viral antigen positive cells were present in the interstitial spaces between the seminiferous tubules with macrophage infiltration also evident. This work provides insights into potential of sexual transmission for MPXV viruses as well as mechanisms of Mpox disease which may significantly impact long-term fertility or sex organ health of infected males. Author Summary: Mpox (formerly monkeypox) is a painful disease similar to smallpox caused by the monkeypox virus (MPXV) which is an emerging/re-emerging virus. Recently the WHO has declared two global health emergencies due to human-to-human transmission of MPXV. Clade IIb MPXV is a newly recognized subclade that has been associated with genital lesions and sexual transmission/contact; however, how the virus causes disease in sex-organs or how it is passed from person-to-person is not understood. We investigated several routes of MPXV Clade IIb inoculation and found IP inoculation in male mice led to high and prolonged viral titres in testes. Additionally, the testes were significantly affected having loss of sperm and cellular organization. Evidence of inflammatory cell infiltration, specifically, macrophages, are suspected to be the cause of testes specific disease. This work provides insights into potential of sexual transmission for MPXV viruses as well as mechanisms of Mpox disease.

Middle East respiratory syndrome coronavirus (MERS-CoV) causes a spectrum of disease outcomes in infected humans, ranging from asymptomatic or tolerant to lethal. While the virus itself contributes to pathogenesis, disease severity is primarily influenced by the host’s response to infection. One factor observed to impact the host response is sex, as epidemiological data indicates that male persons have a higher case fatality rate than females infected with MERS-CoV. However, the mechanism underlying this sex bias is unknown and disease course remains difficult to predict. This study investigates how male and female transgenic mice expressing humanized dipeptidyl peptidase-4 (hDPP4) respond to MERS-CoV infection following exposure to either a tolerance-inducing low dose or lethal high dose. We observed that female hDPP4 mice display dose-dependent tolerance to infection and males experienced uniformly lethal disease in both dosing groups. Longitudinal transcriptomic analysis revealed that males suppress innate and inflammatory responses early after infection, causing delayed induction of the host antiviral response. In contrast, high dose females mount an immediate and sustained interferon and inflammatory response, activating antiviral effectors and interferon-stimulated genes. Tolerant females displayed the greatest transcriptional control, showing no pathway enrichment and minimal changes in weight throughout infection. Our results suggest that the magnitude of the response is driven by dose while the nature of the response in shaped by sex. Females mount a more robust response to MERS-CoV infection, allowing females to tolerate low-dose infection but causing uncontrolled inflammation after high dose infection. In contrast, males experienced lethal outcomes regardless of dose. By examining the dynamics of sex-biased host transcriptional responses in determining disease severity, this study highlights the importance of sex as a biological variable in coronavirus pathogenesis research.

The H5N1 avian panzootic has resulted in cross-species transmission to birds and mammals, causing outbreaks in wildlife, poultry, and US dairy cattle with a range of host-dependent pathogenic outcomes. Although no human-to-human transmission has been observed, the rising number of zoonotic human cases creates opportunities for adaptive mutation or reassortment. This Gem explores the history, evolution, virology, and epidemiology of clade 2.3.4.4b H5N1 relative to its pandemic potential. Pandemic risk reduction measures are urgently required.

Highly pathogenic avian influenza (HPAI) H5N1 has caused the deaths of more than 100 million birds since 2021, and human cases since 1997 have been associated with significant morbidity and mortality. Given recent detections of HPAI H5N1 in dairy cattle and H5N1 RNA detections in pasteurized retail milk in the United States, we established the pan-Canadian Milk Network in April 2024. Through our network of collaborators from across Canada, retail milk was procured longitudinally, approximately every 2 weeks, and sent to a central laboratory to test for the presence of influenza A virus RNA. Between 29 April and 17 July 2024, we tested 109 retail milk samples from all 10 Canadian provinces (NL, NS, PEI, NB, QC, ON, MB, SK, AB, and BC). All samples tested negative for influenza A virus RNA. This nationwide initiative was established for rapid retail milk screening as per the earliest reports of similar undertakings in the United States. Our independent testing results have aligned with reporting from federal retail milk testing initiatives. Despite no known HPAI infections of dairy cattle in Canada to date, H5N1 poses a significant threat to the health of both humans and other animals. By performing routine surveillance of retail milk on a national scale, we have shown that academic networks and initiatives can rapidly establish nationwide emerging infectious disease surveillance that is cost-effective, standardized, scalable, and easily accessible. Our network can serve as an early detection system to help inform containment and mitigation activities if positive samples are identified and can be readily reactivated should HPAI H5N1 or other emerging zoonotic viruses be identified in agricultural or livestock settings, including Canadian dairy cattle.

Uncontrolled systemic inflammatory responses are a critical pathological feature of fatal Ebola virus (EBOV) infection. While some inflammatory responses may originate from mononuclear phagocytes (MNPs), non-immune cells vastly outnumber MNPs and may be an important source of inflammation. Here, we demonstrated that highly virulent EBOV induced a high and sustained pro-inflammatory response compared to less virulent ebolaviruses in non-MNPs through TLR4-independent NF-κB activation. We identified the EBOV matrix protein VP40 as a potent activator of NF-κB in non-MNPs, whose intrinsic inflammatory activation ability is higher than VP40 proteins from less virulent ebolaviruses. This suggests that VP40 is a novel virulence determinant inducing distinct degrees of pro-inflammatory responses among ebolaviruses. Mechanistically, VP40 activated the NF-κB signaling pathway, primarily via TNFR1 using a ligand-independent mechanism. These findings reveal mechanisms that may drive systemic inflammation and promote EBOV pathogenesis, suggesting potential therapeutic strategies to mitigate immune dysregulation in severe EBOV infections.

Science is humanity’s best insurance against threats from nature, but it is a fragile enterprise that must be nourished and protected. The preponderance of scientific evidence indicates a natural origin for SARS-CoV-2. Yet, the theory that SARS-CoV-2 was engineered in and escaped from a lab dominates media attention, even in the absence of strong evidence. We discuss how the resulting anti-science movement puts the research community, scientific research, and pandemic preparedness at risk.

Highly pathogenic avian influenza (HPAI) H5N1 has caused the deaths of more than 100 million birds since 2021, and human cases since 1997 have been associated with significant morbidity and mortality. Given the recent detection of HPAI H5N1 in dairy cattle and H5N1 RNA detections in pasteurized retail milk in the United States, we established the Pan-Canadian Milk (PCM) Network. Through our network of collaborators from across Canada, retail milk is being procured longitudinally and sent to a central laboratory for testing for the presence of influenza A virus RNA. To date (05 July 2024), we have tested 92 retail milk samples from all ten Canadian provinces (NL, NS, PEI, NB, QC, ON, MB, SK, AB, and BC) and all have tested negative for influenza A virus RNA. Testing is ongoing and these results will be updated on rolling basis as additional data becomes available. Despite no known HPAI infections of dairy cattle in Canada to date, H5N1 poses a significant threat to the health of both humans and other animals. Routine surveillance of retail milk on a national scale will allow for monitoring of infected dairy cattle on an ongoing basis in a cost-effective, standardized, scalable and easily accessible manner. Our network and testing will act as an early detection system to help inform containment and mitigation activities if positive samples are identified.

Volume 98, no. 1, e01791-23, 2024, https://doi.org/10.1128/jvi.01791-23. Page 3, line 7: “elevating SARS-CoV-1 to a select agent in 2009” should read “elevating SARS-CoV-1 to a select agent in 2012.”