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Many factors involved in heparan sulfate (HS) biosynthesis and metabolism have been reported to play roles in viral infection. However, the detailed mechanisms are still not fully understood. In this study, we report that exostosin glycosyltransferase 1 (EXT1), the HS polymerase, is a critical regulatory factor for Zika virus (ZIKV) infection. Knocking out EXT1 dramatically restricts ZIKV infection, which is not due to the inhibition of virus entry resulting from HS deficiency, but mediated by the downregulation of autophagy. Induction of autophagy promotes ZIKV infection, and attenuated autophagy is found in distinct EXT1 knockout (EXT1-KO) cell lines. Induction of autophagy by rapamycin can relieve the ZIKV production defect in EXT1-KO cells. While over-expressing EXT1 results in the reduction of ZIKV production by targeting the viral envelope (E) protein and non-structural protein NS3 in a proteasome-dependent degradation manner. The different roles of EXT1 in ZIKV infection are further confirmed by the data that knocking down EXT1 at the early stage of ZIKV infection represses viral infection, whereas the increase of ZIKV infection is observed when knocking down EXT1 at the late stage of viral infection. This study discovers previously unrecognized intricate roles of EXT1 in ZIKV infection.

Shrews are primary hosts for mammalian hantaviruses and are thus considered to be important reservoirs for viruses, similar to rodents and bats. To explore the diversity of hantaviruses in Swedish common shrews (Sorex araneus), we investigated lung tissue from shrews collected between 2015 and 2017. The collection took place at three separate locations in south-central Sweden. Screening for hantaviruses was performed using two different approaches. (i) A total of 113 common shrews were investigated for hantaviruses by a pan-hantavirus L-gene reverse transcriptase PCR, and Sanger sequencing was performed on the 13 positive samples. (ii) In addition, 88 RNA samples were pooled into eight libraries subjected to RNA sequencing. The RNA sequencing data analysis, which focused specifically on identifying hantaviruses, revealed two divergent hantaviruses: the complete genome of an Altai virus (ALTV) and the partial genome of the Seewis virus. Evolutionary analysis revealed that Swedish ALTVs are closely related to Russian ALTVs but distinct from Finnish strains. On the contrary, the Swedish Seewis virus shares closer ancestry with Finnish Seewis virus strains. Given that these viruses were identified in several pools, Seewis virus and ALTV are likely circulating in Swedish common shrews. Supported by earlier studies, common shrews are probably a natural host for at least these two distinct hantaviruses.

We report Sindbis virus circulation in the Netherlands based on serologic evidence found in 6 resident wild birds and 3 horses (2021–2022). Tested mosquitoes were molecularly negative, and humans were serologically negative. Veterinarians and health practitioners in the Netherlands should be aware of the importance of surveillance for Sindbis virus.

Background

Tick-borne encephalitis is a viral infection of the central nervous system that may cause severe illness and long-term sequelae, to which underlying mechanisms are not completely understood. Autoantibodies against the N-methyl-D-aspartate receptor (anti-NMDAR) may be triggered by immunologic events, occur sporadically, and can cause autoimmune encephalitis. Following herpes simplex encephalitis and Japanese encephalitis, anti-NMDAR autoantibodies may develop and have been associated with relapse or impaired cognitive recovery. Tick-borne encephalitis has been shown to trigger anti-NMDAR encephalitis in sporadic cases, but the frequency of autoimmunization is unknown.

Objectives

The objective of this study was to assess the frequency of intrathecal anti-NMDAR antibody development following tick-borne encephalitis and to explore whether such antibodies could be relevant to cognitive complaints.

Methods

Adult patients with tick-borne encephalitis were included retrospectively from one cohort and prospectively from another. A stored post-acute cerebrospinal fluid sample was required for anti-NMDAR analysis. Two commercial kits (Euroimmun AG, Lübeck, Germany) were used to detect anti-NMDAR IgG antibodies in cerebrospinal fluid.

Results

A total of 71 cerebrospinal fluid samples from 53 patients were analyzed for anti-NMDAR antibodies. Samples were obtained at a median of 91 days (range 21-471) after onset of central nervous system symptoms. Anti-NMDAR antibodies were detected in two samples from a single tick-borne encephalitis patient, corresponding to 1.9% of patients (95% CI: 0.05-10.1%).

Conclusions

The development of intrathecal anti-NMDAR autoantibodies following tick-borne encephalitis is a rare event, and further studies are needed to clarify their potential relevance to cognitive outcomes in a minority of cases. Testing for anti-NMDAR antibodies in cerebrospinal fluid may be considered in patients who experience clinical deterioration following an initial recovery.

Studies on human respiratory viral infections and pathogenesis have historically been conducted using immortalized cells and animal models. However, these models are limited in their ability to recapitulate the complex structure of the human airway or the full spectrum of disease symptoms observed in humans. Recently, nose and lung organoids have revolutionized culture complexity in infection biology and have demonstrated potential for research on respiratory virus infections in humans. In this opinion, we review how advances in human nose and lung organoid models, which are able to express all cell types of the respiratory epithelia, i.e., Club, basal, goblet, and ciliated cells, have provided novel insight into the pathogenesis, age-dependent susceptibility, viral attenuation signature, and immune mechanisms of respiratory viruses such as SARS-CoV-2, respiratory syncytial virus, and influenza virus. The models have also demonstrated potential for studying hitherto uncultivable human viruses and to be useful for studies of zoonotic risk.

Background: Wildlife farming is a growing industry, but it poses substantial risks for zoonotic disease transmission, including infections caused by hantaviruses and hepatitis E virus (HEV). This study aimed to determine seroprevalences of these viruses among wildlife farmers and identify associated risk factors.

Methods: A cross-sectional study was conducted among 210 wildlife farmers in Lao Cai and Dong Nai provinces in Vietnam who raised bats, bamboo rats, civets, and wild boars. Of these, 207 provided serum samples for serological testing for hantavirus and HEV antibodies. Apparent (AP) and true (TP) prevalences were estimated, and multivariable logistic regression was performed to identify risk factors.

Results: The AP of hantavirus IgG was 8.7%, 95% confidence interval (CI): 5.4-13.6 (TP: 4.7%, 95% credible interval (CrI): 0.2-11.1). HEV IgG AP was 26.7%, 95%CI: 20.8-33.2 (TP: 27.1%, 95%CrI: 21.3-33.4). Hantavirus IgM testing was also performed due to higher IgG seroprevalence compared to earlier studies, detecting IgM antibodies in 1.9% of samples (95%CI: 0.6-5.2) (TP: 1.7%, 95%CrI: 0.1-4.7). Hantavirus seropositivity was significantly associated with engaging only in wildlife farming, and not participating in other activities such as hunting, trading, slaughtering, processing, guano collection, or consumption (OR = 2.7, 95% CI: 1.1-6.9). HEV seropositivity was significantly associated with men gender (OR = 3.1, 95%CI: 1.4-7.3), older age (OR = 1.03, 95%CI: 1.0-1.1), raw meat consumption (OR = 6.8, 95%CI: 1.6-31.8), residing at higher altitudes (OR = 31.6, 95%CI: 5.5-204.4), and reporting use of protective clothing (OR = 4.0, 95%CI: 1.4-11.2), although their proper use was not assessed.

Conclusions: This study highlights behavioural and environmental risk factors associated with wildlife farming and zoonotic pathogens exposure. Public health interventions should focus on biosecurity, proper hygiene practices, and risk communication to reduce the transmission in wildlife farming settings.

The COVID-19 pandemic has demonstrated the significance of the human-animal interface in the emergence of zoonotic diseases, with wildlife serving as an important source of infection. A better understanding of the specific pathogens and mechanisms involved is vital to prepare against future outbreaks, especially in Southeast Asia, a hotspot for zoonotic diseases. This paper reviews the published literature on wildlife zoonoses in this region from 2012 to 2022. The results show a diverse range of potential zoonotic pathogens and the widespread occurrence of zoonotic diseases from wildlife. Drivers of zoonotic pathogen spillover include (i) environmental factors (e.g. animal habitat disruption, environmental conditions, exposure to contaminated water/food/soil), (ii) animal factors (e.g. movement patterns, age-related susceptibility), (iii) human factors (e.g. lack of awareness, poor hygiene practices, age, gender and income) and (iv) human-animal-environmental interface factors (e.g. close contact between humans and animals, exposure through visiting animals and presence of vectors). The diverse drivers of zoonoses in Southeast Asia put its communities at risk for infection. To mitigate these risks, global health efforts should consider adopting a One Health approach to foster collaboration across human, animal, and wildlife health sectors. This could involve educating communities on safe animal interactions and improving disease surveillance.

The high transmissibility and mutation ability of coronaviruses enable them to easily escape existing immune protection and also pose a challenge to existing antiviral drugs. Moreover, drugs only targeting viruses cannot always attenuate the “cytokine storm”. Herein, a synthetic heparan sulfate (HS) mimetic, HMSA-06 is reported, that exhibited antiviral activities against both the SARS-CoV-2 prototype and Omicron strains by targeting viral entry and replication. Of particular note, HMSA-06 demonstrated more potent anti-SARS-CoV-2 effects than PG545 and Roneparstat. SARS-CoV-2 is reported to hijack autophagy to facilitate its replication, therefore boosting autophagy can attenuate SARS-CoV-2 infection. It is revealed that HMSA-06, but not a similar HS mimetic that failed to inhibit SARS-CoV-2, can upregulate cellular autophagy flux. In addition, HMSA-06 was found to robustly block the NLRP3-mediated inflammatory reaction in SARS-CoV-2 infected THP-1 derived macrophages as evidenced by a reduction in inflammasome formation and the subsequent decreased secretion of mature caspase-1 and IL-1β. The HMSA-06's inflammation inhibitory function is further confirmed using a LPS/ATP-stimulated THP-1 macrophage model. Altogether, this study has identified a promising HS mimetic to combat SARS-CoV-2-associated diseases by inhibiting viral infection and attenuating viral-induced inflammatory reaction, providing insights into the development of novel anti-coronavirus drugs in the future.

Objectives

Borrelia burgdorferi sensu lato (Bbsl) and tick-borne encephalitis virus (TBEV) are tick-borne pathogens. This study aimed to investigate the seroprevalence of these pathogens in Danish blood donors.

Methods

A total of 1000 plasma samples equally distributed (n = 200) from all five Danish regions were analyzed. Commercially available enzyme-linked immunosorbent assays were used to screen the samples for immunoglobulin G antibodies against Bbsl and TBEV. The samples positive for antibodies against TBEV were further examined with a commercially available enzyme-linked immunosorbent assay and a Luminex-based TBEV suspension multiplex immunoassay for specific antibodies against non-structural protein 1 (NS1) antigen suggestive of previous infection.

Results

A total of 62 samples tested positive for immunoglobulin G antibodies against Bbsl. A total of 40 samples were positive or borderline for antibodies against TBEV, indicating potential infection or vaccination. Of these, one had antibodies against NS1, indicating past infection. The seroprevalence of Bbsl was 6.2% (95% confidence interval 4.8-7.8), with equal seroprevalence in all five regions. The seroprevalence of TBEV was 0.1% (95% confidence interval 0.01-0.62%).

Conclusions

The seroprevalence of Bbsl was similar throughout the country and corresponds well with previous studies. The seroprevalence of TBEV NS1 was low, which is in line with a low number of reported tick-borne encephalitis cases in Denmark. The NS1 positive sample was from the Capital Region, an endemic TBEV area.

Zoonotic coronaviruses can transmit over species barriers and infect humans. To understand the zoonotic potential of a betacoronavirus, Grimsö virus (GRIV), we investigated the geographic distribution and tissue tropism of GRIV in Swedish bank voles (Clethrionomys glareolus), and the antigenicity of the nucleocapsid (N) protein. We screened the lung tissues from animals collected in the southern Sweden by RT-PCR with primers targeting the spike gene. Seven out of 74 animals were found to be positive. They are genetically close to GRIV from Grimsö, central Sweden. Positive rodents were studied for the tissue distribution of GRIV and GRIV RNA was mainly found in the respiratory tract. After three attempts of virus isolation were failed, we successfully established a Vero E6 cell line that stably expressed GRIV N protein, which has no cross-reactivity with patient serum containing antibodies against SARS-CoV-2, or with MERS-CoV. However, a low level of cross-reactivity to common cold coronaviruses was found, likely HCoV-OC43 or HCoV-HKU1, probably due to shared linear epitopes. With the high prevalence and the suggested respiratory transmission route, GRIV may have a high potential for spillover and cross-species transmission, and future serological screening of GRIV infections in domestic animals or humans will be needed.