Zika RNA and Flavivirus-Like Antigens in the Sperm Cells of Symptomatic and Asymptomatic Subjects

Correlation between viral infections in male semen and infertility: a literature review

Infertility affects approximately one-sixth of couples globally, with the incidence of male infertility steadily increasing. However, our understanding of the impact of viral infections on fertility remains limited. This review consolidates findings from previous studies, outlining 40 viruses identified in human semen and summarizing their key characteristics, modes of transmission, and their effects on both the reproductive and endocrine systems. Furthermore, it elucidates potential pathogenic mechanisms and treatment prospects of viruses strongly associated with male infertility. This synthesis will enhance our comprehension of how viral infections influence male reproductive health, offering valuable insights for future research as well as the diagnosis and treatment of infectious infertility.

Infectious hepatitis E virus is associated with the mature sperm head

Hepatitis E virus (HEV) is the leading cause of acute viral hepatitis worldwide. HEV associated pregnancy mortality has been reported as up to 30% in humans. Recent findings suggest HEV may elicit effects directly in the reproductive system with HEV protein found in the testis, viral RNA in semen, and viral replication occurring in placental cell types. Using a natural host model for HEV infection, pigs, we demonstrate infectious HEV within the mature spermatozoa and altered sperm viability from HEV infected pigs. HEV isolated from sperm remained infectious suggesting a potential transmission route via sexual partners. Our findings suggest that HEV should be explored as a possible sexually transmittable disease. Our findings propose that infection routes outside of oral and intravenous infection need to be considered for their potential to contribute to higher mortality in HEV infections when pregnancy is involved and in HEV disease in general.

Update on known and emergent viruses affecting human male genital tract and fertility

Many viruses infect the male genital tract with harmful consequences at individual and population levels. In fact, viral infections may induce damage to different organs of the male genital tract (MGT), therefore compromising male fertility. The oxidative stress, induced during viral-mediated local and systemic inflammation, is responsible for testicular damage, compromising germinal and endocrine cell functions. A reduction in sperm count, motility, number of normal sperm and an increase in DNA fragmentation are all common findings in the course of viral infections that, however, generally regress after infection clearance. In some cases, however, viral shedding persists for a long time leading to unexpected sexual transmission, even after the disappearance of the viral load from the blood.The recent outbreak of Zika and Ebola Virus evidenced how the MGT could represent a reservoir of dangerous emergent viruses and how new modalities of surveillance of survivors are strongly needed to limit viral transmission among the general population.Here we reviewed the evidence concerning the presence of relevant viruses, including emergent and re-emergent, on the male genital tract, their route of entry, their adverse effects on male fertility and the pattern of viral shedding in the semen.We also described laboratory strategies to reduce the risk of horizontal or vertical cross-infection in serodiscordant couples undergoing assisted reproductive technologies.

Unraveling the Intricacies of the Seminal Microbiome and Its Impact on Human Fertility

Although the microbial communities from seminal fluid were an unexplored field some decades ago, their characteristics and potential roles are gradually coming to light. Therefore, a complex and specific microbiome population with commensal niches and fluctuating species has started to be revealed. In fact, certain clusters of bacteria have been associated with fertility and health, while the outgrowth of several species is potentially correlated with infertility indicators. This constitutes a compelling reason for outlining the external elements that may induce changes in the seminal microbiome composition, like lifestyle factors, gut microbiota, pathologies, prebiotics, and probiotics. In this review, we summarize the main findings about seminal microbiome, its origins and composition, its relationship with fertility, health, and influence factors, while reminding readers of the limitations and advantages introduced from technical variabilities during the experimental procedures.

Human seminal virome: a panel based on recent literature

Background

The seminal virome and its implications for fertility remain poorly understood. To date, there are no defined panels for the detection of viruses of clinical interest in seminal samples.

Results

In this study, we characterized the human seminal virome based on more than 1,000 studies published over the last five years.

Conclusions

The number of studies investigating viruses that occur in human semen has increased, and to date, these studies have been mostly prospective or related to specific clinical findings. Through the joint analysis of all these studies, we have listed the viruses related to the worsening of seminal parameters and propose a new panel with the main viruses already described that possibly affect male fertility and health. This panel can assist in evaluating semen quality and serve as a tool for investigation in cases of infertility.

Prolonged shedding of Zika virus in human semen is associated with male reproductive tract inflammation

Zika virus (ZIKV) is a mosquito-borne flavivirus that causes congenital defects. Sexual transmission of ZIKV was confirmed in a recent epidemic; however, mechanisms behind ZIKV infection and persistence in the male reproductive tract are unknown. Previously, we found that ∼33% of men with symptomatic ZIKV infections shed ZIKV RNA in semen, and some men shed ZIKV RNA for >3 months. Here, we evaluated the semen of 49 ZIKV-infected men to identify immune factors correlating with long-term ZIKV shedding in semen and ZIKV-infected cell types in semen. We found prolonged ZIKV RNA shedding in semen was associated with male reproductive tract inflammation, indicated by higher leukocyte counts and inflammatory cytokine concentrations in semen of long-term versus short-term shedders. Additionally, we found ZIKV RNA in seminal leukocytes and epithelial cells. This study of human semen from ZIKV-infected men provides critical insights into impacts of ZIKV on male reproductive tract health.