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Objectives: The 2022 mpox epidemic reached a peak in Belgium and the rest of Europe in July 2022, after which it unexpectedly subsided. This study investigates epidemiological, behavioral, and immunological factors behind the waning of the epidemic in Belgium., Methods: We investigated temporal evolutions in the characteristics and behavior of mpox patients using national surveillance data and data from a prospective registry of mpox patients in the Institute of Tropical Medicine (Antwerp). We studied behavioral changes in the population at risk using a survey among HIV-preexposure prophylaxis (PrEP) users. We determined the seroprevalence of anti-orthopoxvirus antibodies among HIV-PrEP users across four-time points in 2022., Results: Mpox patients diagnosed at the end of the epidemic had less sexual risk behavior compared to those diagnosed earlier: they engaged less in sex at mass events, had fewer sexual partners, and were less likely to belong to the sexual network's central group. Among HIV-PrEP users there were no notable changes in sexual behavior. Anti-orthopoxvirus seroprevalence did not notably increase before the start of national vaccination campaigns., Conclusion: The observed changes in group immunity and behavior in the population at greater risk of exposure to mpox seem unable to explain the waning of the mpox epidemic. A change in the profile of mpox patients might have contributed to the decline in cases., Competing Interests: Declarations of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this article., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

The Omicron BA.1 (B.1.1.529) SARS-CoV-2 variant is characterized by a high number of mutations in the viral genome, associated with immune escape and increased viral spread. It remains unclear whether milder COVID-19 disease progression observed after infection with Omicron BA.1 in humans is due to reduced pathogenicity of the virus or due to pre-existing immunity from vaccination or previous infection. Here, we inoculated hamsters with Omicron BA.1 to evaluate pathogenicity and kinetics of viral shedding, compared to Delta (B.1.617.2) and to animals re-challenged with Omicron BA.1 after previous SARS-CoV-2 614G infection. Omicron BA.1 infected animals showed reduced clinical signs, pathological changes, and viral shedding, compared to Delta-infected animals, but still showed gross- and histopathological evidence of pneumonia. Pre-existing immunity reduced viral shedding and protected against pneumonia. Our data indicate that the observed decrease of disease severity is in part due to intrinsic properties of the Omicron BA.1 variant.

The ability of SARS-CoV-2 to evolve in response to selective pressures poses a challenge to vaccine and antiviral efficacy. The S1 subunit of the spike (S) protein contains the receptor-binding domain and is therefore under selective pressure to evade neutralizing antibodies elicited by vaccination or infection. In contrast, the S2 subunit of S is only transiently exposed after receptor binding, which makes it a less efficient target for antibodies. As a result, S2 has a lower mutational frequency than S1. We recently described monomeric and dimeric SARS-CoV-2 fusion-inhibitory lipopeptides that block viral infection by interfering with S2 conformational rearrangements during viral entry. Importantly, a dimeric lipopeptide was shown to block SARS-CoV-2 transmission between ferrets in vivo. Because the S2 subunit is relatively conserved in newly emerging SARS-CoV-2 variants of concern (VOCs), we hypothesize that fusion-inhibitory lipopeptides are cross-protective against infection with VOCs. Here, we directly compared the in vitro efficacies of two fusion-inhibitory lipopeptides against VOC, in comparison with a set of seven postvaccination sera (two doses) and a commercial monoclonal antibody preparation. For the beta, delta, and omicron VOCs, it has been reported that convalescent and postvaccination sera are less potent in virus neutralization assays. Both fusion-inhibitory lipopeptides were equally effective against all five VOCs compared to ancestral virus, whereas postvaccination sera and therapeutic monoclonal antibody lost potency to newer VOCs, in particular to omicron BA.1 and BA.2. The neutralizing activity of the lipopeptides is consistent, and they can be expected to neutralize future VOCs based on their mechanism of action. IMPORTANCE SARS-CoV-2, the causative agent of COVID-19, continues to spread globally, with waves resulting from new variants that evade immunity generated by vaccines and previous strains and escape available monoclonal antibody therapy. Fusion-inhibitory peptides may provide an intervention strategy that is not similarly affected by this viral evolution.

Context: The role of estrogens in ischemic heart disease (IHD) is uncertain. Evidence suggests that genetic variations in the estrogen receptor alpha (ESR1) gene may influence IHD risk, but the role of common sequence variations in the ESR1 gene is unclear., Objective: To determine whether the ESR1 haplotype created by the c.454-397T>C (PvuII) and c.454-351A>G (XbaI) polymorphisms is associated with myocardial infarction (MI) and IHD risk., Design, Setting, and Participants: In 2617 men and 3791 postmenopausal women from The Rotterdam Study (enrollment between 1989-1993 and follow-up to January 2000), a population-based, prospective cohort study of participants aged 55 years and older, ESR1 c.454-397T>C and c.454-351A>G haplotypes were determined. Detailed interviews and physical examinations were performed, blood samples were obtained, and cardiovascular risk factors were assessed., Main Outcome Measure: The primary outcome was MI and IHD defined as MIs, revascularization procedures, and IHD mortality., Results: Approximately 29% of women and 28.2% of men were homozygous carriers of the ESR1 haplotype 1 (-397 T and -351 A) allele, 49% of women and 50% of men were heterozygous carriers, and 22% of women and 21.4% of men were noncarriers. During a mean follow-up of 7.0 years, 285 participants (115 women; 170 men) had MI, and 440 (168 women; 272 men) had an IHD event, of which 97 were fatal. After adjustment for known cardiovascular risk factors, female heterozygous carriers of haplotype 1 had an increased risk of MI (event rate, 2.8%; relative risk [RR], 2.23; 95% confidence interval [CI], 1.13-4.43) compared with noncarriers (event rate, 1.3%), whereas homozygous carriers had an increased risk (event rate, 3.2%; RR, 2.48; 95% CI, 1.22-5.03). For IHD events, we observed a similar association. In women, the effect of haplotype 1 on fatal IHD was larger than on nonfatal IHD. In men, the ESR1 haplotypes were not associated with an increased risk of MI (event rate, 5.7%; RR, 0.93; 95% CI, 0.59-1.46 for heterozygous carriers; and event rate, 5.1%; RR, 0.82; 95% CI, 0.49-1.38 for homozygous carriers) compared with noncarriers (event rate, 5.8%) and were not associated with an increased risk of IHD., Conclusions: In this population-based, prospective cohort study, postmenopausal women who carry ESR1 haplotype 1 (c.454-397 T allele and c.454-351 A allele) have an increased risk of MI and IHD, independent of known cardiovascular risk factors. In men, no association was observed.