Zika virus persistence in the male macaque reproductive tract

Abstract

Zika virus (ZIKV) is unique among mosquito-borne flaviviruses in that it is also vertically and sexually transmitted by humans. The male reproductive tract is thought to be a ZIKV reservoir; however, the reported magnitude and duration of viral persistence in male genital tissues vary widely in humans and non-human primate models. ZIKV tissue and cellular tropism and potential effects on male fertility also remain unclear. The objective of this study was to resolve these questions by analyzing archived genital tissues from 51 ZIKV-inoculated male macaques and correlating data on plasma viral kinetics, tissue tropism, and ZIKV-induced pathological changes in the reproductive tract. We hypothesized that ZIKV would persist in the male macaque genital tract for longer than there was detectable viremia, where it would localize to germ and epithelial cells and associate with lesions. We detected ZIKV RNA and infectious virus in testis, epididymis, seminal vesicle, and prostate gland. In contrast to prepubertal males, sexually mature macaques were significantly more likely to harbor persistent ZIKV RNA or infectious virus somewhere in the genital tract, with detection as late as 60 days post-inoculation. ZIKV RNA localized primarily to testicular stem cells/sperm precursors and epithelial cells, including Sertoli cells, epididymal duct epithelium, and glandular epithelia of the seminal vesicle and prostate gland. ZIKV infection was associated with microscopic evidence of inflammation in the epididymis and prostate gland of sexually mature males, pathologies that were absent in uninfected controls, which could have significant effects on male fertility. The findings from this study increase our understanding of persistent ZIKV infection which can inform risk of sexual transmission during assisted reproductive therapies as well as potential impacts on male fertility.

Zika Virus Infection Damages the Testes in Pubertal Common Squirrel Monkeys (Saimiri collinsi)

“…Due to their immaturity, the testes of young KO A129 mice showed greater tissue damage than those of adult animals [ 60 ], in which no atrophy, inflammation, or hemorrhage was observed. Similar findings were described in a study of 51 NHPs ( Macaca mulatta and Macaca fascicularis ) from a rather heterogeneous sample group, in which higher rates of ZIKV RNA detection and histopathological lesions were observed in mature primates than sexually immature primates; however, these findings were observed more in the epididymis, prostate, and seminal vesicles than the testes, which were not available or samples were excluded [ 14 ]. In contrast to the aforementioned research, in our study, it was possible to observe histopathological damage and to detect ZIKV RNA in pubertal animals.…”

“…An analysis of the kinetics of infection, with evidence of fever ( Figure 2 A), viremia ( Figure 2 B), and IgM antibody detection ( Figure 2 C). Thus, it was possible to delineate the acute phase of infection (between 1 and 10 dpi) and the onset of the convalescent phase (10 dpi to 21 dpi), periods that are similar to those in other research with NHPs as well as humans [ 14 , 78 ]. Interestingly, animal AT-005 showed a persistent febrile state between 3 and 10 dpi, which was observed to be consistent with the viremic period (3 to 10 dpi), and a higher O.D.…”

“…As pointed out by Ball et al (2022) [ 14 ], formalin fixation damages testicular tissue, making histological evaluation difficult. Consequently, we adopted Johnsen’s score to better evaluate the degree of spermatogenic cell differentiation.…”

“…Experiments in mice [ 7 , 8 , 9 , 11 , 12 , 13 ] and nonhuman primates [ 14 , 15 , 16 , 17 ], as well as ex vivo and in vitro human testicular cell investigations [ 13 , 18 , 19 , 20 , 21 ], have confirmed the ability of this virus to infect and cause the degeneration and necrosis of multiple testicular cell lines in the interstitium and within the seminiferous tubules, emphasizing the tropism of the virus and its ability to use the male reproductive tract as a reservoir [ 22 , 23 , 24 ]. Sexual transmission of the virus has also been described in humans [ 24 ].…”

CD8+T cell response promotes viral clearance and reduces chances of severe testicular damage in mouse models of long-term Zika virus infection of the testes

“…Using animal and cell culture models, components of the male reproductive tract shown to be a site of long-term replication and inflammation include the epididymides [14][15][16] , the prostate [17][18] , and the testes [19][20][21] , leading to reduced fertility in mouse models 21 . Studies using ZIKV-infected NHP 22 and mouse models [20][21] have also showed ZIKV infection can lead to histopathologic lesions in the testes, which is a health concern for infected men in addition to impacting fertility. The testes are the site of spermatogenesis and may play a key role in ZIKV-caused infertility as well as viral maintenance for sexual transmission.…”