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Zika virus in rhesus macaque semen and reproductive tract tissues: a pilot study of acute infection† - PubMed

  • ️Wed Jan 01 2020

Zika virus in rhesus macaque semen and reproductive tract tissues: a pilot study of acute infection†

Jenna K Schmidt et al. Biol Reprod. 2020.

Abstract

Although sexual transmission of Zika virus (ZIKV) is well-documented, the viral reservoir(s) in the male reproductive tract remains uncertain in humans and immune-intact animal models. We evaluated the presence of ZIKV in a rhesus macaque pilot study to determine persistence in semen, assess the impact of infection on sperm functional characteristics, and define the viral reservoir in the male reproductive tract. Five adult male rhesus monkeys were inoculated with 105 PFU of Asian-lineage ZIKV isolate PRVABC59, and two males were inoculated with the same dose of African-lineage ZIKV DAKAR41524. Viremia and viral RNA (vRNA) shedding in semen were monitored, and a cohort of animals were necropsied for tissue collection to assess tissue vRNA burden and histopathology. All animals exhibited viremia for limited periods (1-11 days); duration of shedding did not differ significantly between viral isolates. There were sporadic low levels of vRNA in the semen from some, but not all animals. Viral RNA levels in reproductive tract tissues were also modest and present in the epididymis in three of five cases, one case in the vas deferens, but not detected in testis, seminal vesicles or prostate. ZIKV infection did not impact semen motility parameters as assessed by computer-assisted sperm analysis. Despite some evidence of prolonged ZIKV RNA shedding in human semen and high tropism of ZIKV for male reproductive tract tissues in mice deficient in Type 1 interferon signaling, in the rhesus macaques assessed in this pilot study, we did not consistently find ZIKV RNA in the male reproductive tract.

Keywords: Zika; epididymis; prostate; semen; testis.

© The Author(s) 2020. Published by Oxford University Press on behalf of Society for the Study of Reproduction. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

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Figures

Figure 1
Figure 1

Persistence of ZIKV RNA in fluids. (A) Viremia as determined by qRT-PCR assays of plasma following ZIKV-PR or ZIKV-DAK inoculation. Each line/color indicates an individual animal, and each point indicates the average ZIKV copies/ml across two qRT-PCR reactions. The day post-inoculation is referred to as dpi. (B) Evaluation of ZIKV RNA in blood, urine by qRT-PCR assays, where each sample was determined to be either positive, negative, or equivocal. Urine and semen were not collected from ZIKV-DAK-inoculated males. Equivocal refers to a sample in which amplification was observed in one of two technical qRT-PCR replicates. A failed semen collection attempt results in no sample obtained and is represented by a light gray box with a dash.

Figure 2
Figure 2

ZIKV RNA loads in male reproductive tract tissues. Tissue tropism evaluated by qRT-PCR assays, where positive tissues are denoted by a black box and negative samples by a dark gray box.

Figure 3
Figure 3

Detection of ZIKV by ISH. ZIKV positive tissues identified by qRT-PCR assays of PR inoculated males were evaluated for the presence of ZIKV by ISH. Minor signal was detected in the subscapular space of inguinal lymph nodes of PR-A (A) and a lymphoid nodule in PR-B (B), where tissue was collected at 9 and 21 dpi, respectively. Arrowheads denote an example of a positive signal in each image. (C) No ISH signal was observed in a lymph node from an uninfected control. Scale bars represent 50 μm.

Figure 4
Figure 4

Histopathology of testes following ZIKV inoculation. Hematoxylin and eosin-stained sections from ZIKV-inoculated male PR-A and representative control. (A) 40× images, arrowhead points to an example of a plasma cell among a population of leukocytes infiltrating the interstitium, outlined by the dashed line. (B) 10× images, arrowhead points to the enlarged inset tubule. The inset ZIKV tubule displays diminished germinal epithelium, while the control inset tubule is representative of abundant germinal epithelium layers. Scale bar for panel A is 100 μm and panel B is 200 μm.

Figure 5
Figure 5

Evaluation of semen quality parameters in individual males following inoculation with PR strain ZIKV. Ejaculates were evaluated from four males inoculated with PR strain collected from 0 to 63 dpi. Ejaculate volume and total sperm cells were measured for each ejaculate per time point. CASA was used to obtain the percentage of motile, progressive motile and viable cells for each ejaculate. Colored lines indicate individual ZIKV-inoculated males, whereas the gray lines indicate control males collected within the same time frame as the ZIKV-inoculated males.

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