Clade IIb Mpox virus (MPXV) vertical transmission and fetal demise in a pregnant rhesus macaque model

RESEARCH ARTICLE Clade IIb Mpox virus (MPXV) vertical transmission and fetal demise in a pregnant rhesus macaque model Nicholas P. Krabbe 1☯, Ann M. Mitzey2☯, Saswati Bhattacharya1, Elaina R. Razo1, Xiankun Zeng3, Nell Bekiares4, Amy Moy4, Amy Kamholz4, Julie A. Karl5, Gregory Daggett4, Grace VanSleet6, Terry Morgan7, Saverio V. Capuano4, Heather A. Simmons 4, Puja Basu4, Andrea M. Weiler4, David H. O’Connor4,5, Thomas C. Friedrich4,6, Thaddeus G. Golos2,4,8, Emma L. Mohr 1,9* 1 Department of Pediatrics, University of Wisconsin-Madison, Madison, Wisconsin, United States of America, 2 Department of Comparative Biosciences, University of Wisconsin-Madison, Madison, Wisconsin, United States of America, 3 United States of America Army Medical Research Institute of Infectious Diseases, Fort Detrick, Fredrick, Maryland, United States of America, 4 Wisconsin National Primate Research Center, University of Wisconsin-Madison, Madison, Wisconsin, United States of America, 5 Department of Pathology and Laboratory Medicine, University of Wisconsin-Madison, Madison, Wisconsin, United States of America, 6 Department of Pathobiological Sciences, University of WisconsinMadison, Madison, Wisconsin, United States of America, 7 Department of Obstetrics and Gynecology, Oregon Health and Science University, Portland, Oregon, United States of America, 8 Department of Obstetrics and Gynecology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America, 9 Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America OPEN ACCESS Citation: Krabbe NP, Mitzey AM, Bhattacharya S, Razo ER, Zeng X, Bekiares N, et al. (2025) Clade IIb Mpox virus (MPXV) vertical transmission and fetal demise in a pregnant rhesus macaque model. PLoS ONE 20(4): e0320671. https://doi.org/10.1371/ journal.pone.0320671 Editor: Dhammika Leshan Wannigama, Yamagata University Faculty of Medicine: Yamagata Daigaku Igakubu Daigakuin Igakukei Kenkyuka, JAPAN Received: November 7, 2024 Accepted: February 22, 2025 Published: April 1, 2025 Copyright: This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication. Data availability statement: All raw data and code used for data analysis and Fig making in this article can be found at: https://go.wisc.edu/ xw4o53. ☯ These authors contributed equally to this work. * Abstract Infection with clade I Mpox virus (MPXV) results in adverse pregnancy outcomes, yet the potential for vertical transmission resulting in fetal harm with clade IIb MPXV, the clade that is currently circulating in the Western Hemisphere, remains unknown. We sought to establish a pregnant rhesus macaque model of clade IIb MPXV infection with early gestation inoculation to understand if infection results in vertical transmission and adverse pregnancy outcomes. Three pregnant rhesus macaques were inoculated intradermally with 1.5 x 105 plaque forming units (PFU) of clade IIb MPXV near gestational day (GD) 30 and animals were monitored for viremia and maternal and fetal well-being. Animals were euthanized to collect tissues at 5, 14, or 25 days post-inoculation (dpi). Tissues were evaluated for viral DNA (vDNA) loads, infectious virus titers, histopathology, MPXV mRNA and protein localization, as well as MPXV protein co-localization with placental cells including, Hofbauer cells, mesenchymal stromal cells, endothelial cells, and trophoblasts. vDNA was detected in maternal blood and skin lesions by 5 dpi. Lack of fetal heartbeat was observed at 14 or 25 dpi for two dams indicating fetal demise; the third dam developed significant vaginal bleeding at 5 dpi and was deemed an impending miscarriage. vDNA was detected in placental and fetal tissue in both fetal demise cases. MPXV localized to placental villi by ISH and IHC. Clade IIb MPXV infection in pregnant rhesus macaques results in vertical transmission to the fetus and adverse pregnancy outcomes, like clade I MPXV. This suggests that clade IIb MPXV infection in human pregnancy poses a danger to maternal and PLOS ONE | https://doi.org/10.1371/journal.pone.0320671 April 1, 2025 1 / 18 PLOS ONE Funding: This work was supported by the National Institutes of Health grant R01AI182082 (ELM); National Institutes of Health grant P01AI132132 (DHO); and the National Institutes of Health grant 2R24OD017850 (DHO). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: The authors have declared that no conflict of interest exists. Mpox virus (MPXV) vertical transmission and fetal demise in a pregnant rhesus macaque model fetal health as well. Further studies are needed to determine whether antiviral therapy with tecovirimat will prevent vertical transmission and improve pregnancy outcomes. Introduction Mpox (formerly monkeypox) virus (MPXV), an Orthopoxvirus, is a serious health concern that recently spread around the world, resulting in over 100,000 infections globally [1]. Some MPXV infections cause fetal demise, particularly with clade I MPXV, which is endemic in Central Africa (reviewed in [2]). It is unclear whether clade IIb MPXV, which is circulating worldwide including the United States, is also vertically transmitted and causes adverse pregnancy outcomes. In 2022, an outbreak of mpox, resulting from infection with clade IIb MPXV, spread rapidly across Europe, the Americas, and a total of 110 countries worldwide. MPXV infections have historically been reported in West as well as East and Central Africa [3], with clade I MPXV reported in Central and East Africa and clade II in West Africa [4] although there is concurrent circulation of both clades in some countries [5]. Since January 1, 2022, more than 102,000 clade II mpox cases have been reported worldwide, with 9000 cases in 2024 so far [6]. Although the number of cases peaked in 2022 and numbers have decreased since then, new cases are reported every week within the United States [7]. This highlights the unpredictability of MPXV infection, and the need to better define disease outcomes in vulnerable populations. Fetal death has been reported in mpox cases from countries in Africa where clade I MPXV is endemic, but there are fewer reports of infections during pregnancy in regions where clade IIb MPXV is circulating [8,9]. Clade I MPXV infection is more virulent, leading to a case fatality ratio of 10%, and is associated with high (up to 75%) rates of fetal demise [9,10]. Fetal demise may be due to vertical transmission because fetuses developed diffuse cutaneous maculopapular lesions, hepatomegaly, and hydrops fetalis. Additionally, MPXV DNA was identified in the placenta and viral proteins were identified in the chorionic villi (specif (...truncated)