Risk Factors for Persistent Ebola Virus Infection in Semen Among Survivors From Liberia

Background: Long-term persistence of Ebola virus (EBOV) in immunologically privileged sites has been implicated in recent outbreaks of Ebola Virus Disease (EVD) in Guinea and the Democratic Republic of Congo. This study was designed to better understand how the acute course of EVD, convalescence, and host immune and genetic factors may play a role in prolonged viral persistence in semen. Methods: In 2017, a cohort of 131 male survivors of the 2014-2016 outbreak of EVD in Liberia were recruited from a national semen testing program into this case-case study. “Early clearers” were defined as those with two consecutive negative EBOV semen tests by real-time reverse transcriptase polymerase chain reaction (rRT-PCR) at least two weeks apart within 1 year after discharge from the Ebola Treatment Unit (ETU). “Late clearers” had detectable EBOV RNA by rRT-PCR more than one year after ETU discharge. Retrospective histories of their EVD clinical course were collected by questionnaire, followed by complete physical exams and blood work including chemistries, blood counts, hemoglobinopathies, human leukocyte antigen typing, and immunologic/inflammatory markers. Findings: Among 131 participants, 30 demonstrated long-term detection of EBOV RNA in semen by rRT-PCR, up to 852 days after ETU discharge. Compared to early clearers, late clearers were more likely to be older (median 42.5 years, p=0.0001) and reported having experienced fewer severe clinical symptoms (median 2, p=0.006). Late clearers were found to more frequently have lens opacifications (OR 3.9, 95%CI 1.1-13.3, p=0.03), after accounting for age. Finally, late clearers also exhibited elevated total serum IgG3 titers (p=0.007) and increased expression of the HLA-C*03:04 allele (OR 0.14, 95% CI 0.02-0.70, p=0.007). Interpretation: Older age and decreased illness severity may play a significant role in determining the clearance of EBOV from the semen of survivors. Immune and host genetic factors including total serum IgG3 and HLA-C*03:04 may mediate that interaction. In addition, our finding that late clearers were more likely to have lens opacifications after accounting for age suggests that individuals with EBOV persistence in semen may also have EBOV persistence in other immunologically protected sites, such as the eye. Identifying risk factors for viral persistence in semen among male survivors is critical to inform screening efforts and prevent recurrent outbreaks of EBOV. Funding Information: This was work was supported by funds from the CDC Foundation and the Centers for Disease Control and Prevention. This project has also been funded in whole or in part with federal funds from the Frederick National Laboratory for Cancer Research, under Contract No. HHSN261200800001E. Declaration of Interests: The authors report no competing interests. Ethics Approval Statement: The study protocol was approved by the CDC and Liberia MoH Institutional Review Boards and Meharry Medical College (for hemoglobinopathy testing).