Fusion of enveloped viruses with sperm cells: interaction of Sendai, influenza, and Semliki Forest viruses with bull spermatozoa

Sperm and oocyte as carriers for bovine viral diarrhoea virus biotypes during in vitro fertilization

Bovine viral diarrhoea virus (BVDV) is an important viral agent causing the reproductive failure in cattle. The objectives of the study were to assess the role of male and female gametes, as carriers of cytopathic (CP) and non-cytopathic (NCP) BVDV to embryonic cells during in vitro fertilization. In this respect, sperm and oocytes were separately exposed to concentrations of 104.5 or 105.5 TCID50 /mL CP and NCP BVDV, for 2 h before fertilization. After washing, the intact gametes with the infected gametes were inseminated. Seven days post-fertilization, the virus-exposed embryos were examined for presence of the viral genome by RT-PCR. One-way anova with post-hoc Tukey's HSD test and an independent samples t-test were used to compare within and between groups, respectively. The results presented a significant decrease in the blastocyst rates for CP-infected groups than NCP-infected groups (p ≤ .01). Compared to the controls and the infected oocyte groups, the cleavage rates of the infected sperm groups (NCP and CP BVDV) were significantly reduced both in low (104.5 TCID50 /mL) and high (105.5 TCID50 /mL) titres of the virus (p ≤ .01). The proportion of embryos which was developed to blastocyst stages was significantly lower for CP and NCP-infected groups than the control groups (p ≤ .001). According to the molecular results, all samples of the retarded/degenerated embryos (at least one blastocyst within each one) in CP and NCP groups, one sample (at least one blastocyst in that) within a CP-infected group, and six samples (at least one blastocyst in each one of those) of NCP-infected groups contained the viral nucleic acid. Likewise, the results of viral enrichment showed all reactions in which RT-PCR were positive induced CPEs in MDBK monolayers. In conclusion, it is clear that CP and NCP BVDV were able to traverse zona pellucida during fertilization, and they had also negative effects on embryo development.

Potential impacts of COVID-19 on reproductive health: Scientific findings and social dimension

COVID-19 virus is classified as a respiratory disease that can be mainly transmitted via respiratory droplets, however, there are recently published reports suggested its ability to transmit via sexual intercourse, assisted reproductive technology (ART) treatments, pregnancy, and nursing. Although SARS-CoV-2 mainly attacks respiratory systems, manifestations of multiple organs have been detected. A significant concern was raised about whether COVID-19 may affect female and male reproductive functions. These findings imposed more restrictions on social relationships between individuals even if inside the family, adding more physiologic load. In this context, there is a crucial need to identify the biological and behavioral reproductive risk factors associated with COVID-19 disease. Questions regarding the potential risks of sexual transmission during intercourse and/or application of ART, vertical transmission (throughout pregnancy, delivery, and breastfeeding), the health of pregnant and postpartum women, and fetal or postnatal health problems of neonates/children remain largely unanswered. The contribution of individuals to different social and economic activities depends on the maintenance of good quality life and health. The ongoing COVID-19 pandemic raised on the end of December 2019 has drastically affected different aspects of human wellbeing. The pandemic not only affected the health of individuals, but also negatively affected mental health and social interaction. This review illustrates: a) scientific findings related to the impact of the COVID-19 pandemic on the reproductive process, considering gender, hormonal balance, gonad functions, pregnancy, and ART, b) the sociosexual dimension of COVID-19 disease and precautions that should be taken to avoid infection via sexual transmission or vertical transmission, which may alleviate the fear associated with continuing normal social relationships and economic activities.

COVID-19 and human spermatozoa-Potential risks for infertility and sexual transmission?

As COVID‐19 infections wreak havoc across the globe, attention has rightly been focused on the vital organ systems (lung, kidney and heart) that are vulnerable to viral attack and contribute to the acute pathology associated with this disease. However, we should not lose sight of the fact that COVID‐19 will attack any cell type in the body expressing ACE2 ‐ including human spermatozoa. These cells possess the entire repertoire of receptors (AT1R, AT2R, MAS) and ligand processing enzymes (ACE1 and ACE2) needed to support the angiotensin signalling cascade. The latter not only provides COVID‐19 with a foothold on the sperm surface but may also promote integration, given the additional presence of a range of proteases (TMPRSS2, TMPRSS11B, TMPRSS12, furin) capable of promoting viral fusion. This article reviews the roles played by these various cellular constituents in maintaining the vitality of human spermatozoa and their competence for fertilization. The reproductive consequences of a viral attack on these systems, in terms of fertility and the risk of sexual transmission, are currently unknown. However, we should be alive to the possibility that there may be reproductive consequences of COVID‐19 infection in young males that go beyond their capacity to survive a viral attack.

Viruses in the reproductive tract: On their way to the germ line?

Studies of vertebrate genomes have indicated that all species contain in their chromosomes stretches of DNA with sequence similarity to viral genomes. How such 'endogenous' viral elements (EVEs) ended up in host genomes is usually explained in general terms such as 'they entered the germ line at some point during evolution'. This seems a correct statement, but is also rather imprecise. The vast number of endogenous viral sequences suggest that common routes to the 'germ line' may exist, as relying on chance alone may not easily explain the abundance of EVEs in modern mammalian genomes. An increasing number of virus types have been detected in human semen and a growing number of studies have reported on viral infections that cause male infertility or subfertility and on viral infections that threaten in vitro fertilisation practices. Thus, it is timely to survey the pathway(s) that viruses can use to gain access to the human germ line. Embryo transfer and semen quality studies in livestock form another source of relevant information because virus infection during reproduction is clearly unwanted, as is the case for the human situation. In this review, studies on viruses in the male and female reproductive tract and in the early embryo will be discussed to propose a plausible viral route to the mammalian germ line.

Effects of bovine Herpesvirus Type 5 on development of in vitro-produced bovine embryos

Bovine (Bos indicus) herpesviruses have been associated with reproductive disease. Type 1, the most studied species, is best known for its reproductive and respiratory effects. Type 5 (BoHV-5) has been detected in bull semen and aborted fetuses but not in oocytes and embryos. This study consisted of three experiments that evaluated (1) BoHV-5-infected oocytes matured in medium with fetal bovine serum (BoHV-FBS) or polyvinyl alcohol (BoHV-PVA) and fertilized by noninfected sperm; (2) noninfected oocytes fertilized by BoHV-5-infected sperm; and (3) infection of presumptive zygotes by BoHV-5. Each treatment involved nine drops of 15 to 20 oocytes. Infection with BoHV-5 was detected by polymerase chain reaction and in situ hybridization assay, and fertilization capacity and embryonic development were assessed using in vitro culture. Experimentally induced infection was obtained in all experiments, and vertical transmission of BoHV-5 by gametes was confirmed. The cleavage rate was reduced (P=0.0201) in BoHV-FBS (80.4+/-8.9%; mean+/-SD) compared with that of noninfected oocytes (89.9+/-6.5%); neither differed from BoHV-PVA (87.3+/-7.1%), and the resulting embryo production rate was not significantly different among groups. Rates of cleavage (87.5+/-7.5% vs. 92.2+/-5.5%, control vs. infected) and development of embryos (41.7+/-9.9% vs. 44.3+/-7.7% to morula/blastocyst/expanded blastocyst [M/B/EB] and 39.6+/-10.3% vs. 40.8+/-9.2% to blastocyst/expanded blastocyst/hatching blastocyst [B/EB/HB] stages) were not compromised by infected sperm (P=0.1462, P=0.5402, and P=0.8074, respectively). However, presumptive zygotes directly infected 1 d after fertilization produced a lower number (P=0.0140 to M/B/EB and P=0.002 to B/EB/HB stages) of in vitro-produced embryos (31.6+/-4.6 vs. 25.0+/-5.5 and 31.6+/-4.6 vs. 20.2+/-5.4; control vs. infected). In conclusion, BoHV-5 infected gametes and was transmissible to the embryo during in vitro development. As zygotes infected 1 d after fertilization had compromised development, BoHV-5 has the potential to be a pathogen with economic consequences.

Evaluation of risks of viral transmission to recipients of bovine embryos arising from fertilisation with virus-infected semen

This scientific review was prompted by recent legislation to curtail the use of semen from potentially virus-infected bulls to produce embryos for import into the European Union. From studies in laboratory animals, humans and horses, it is apparent that viruses may sometimes attach to, or be integrated into, spermatozoa, although in domestic livestock, including cattle, this seems to be a rare phenomenon, and carriage of virus through the zona pellucida into the oocyte by fertilising sperm has never been described in these species. Four specific viruses; enzootic bovine leukosis (EBLV), bovine herpesvirus-1 (BoHV-1), bovine viral diarrhoea virus (BVDV) and bluetongue virus (BTV), all of which tend to cause subclinical infections in cattle, but which can occur in bovine semen, are examined with regard to the risks that use of infected semen might lead to production of infected embryos. With regard to in vivo-derived embryos, when internationally approved embryo processing protocols are used, the risks from EBLV- and BTV-infected semen are negligible, and the same is almost certainly true for semen infected with BoHV-1 if the embryos are also treated with trypsin. For BVDV, there is insufficient data on how the virus is carried in semen and how different BVDV strains can interact with sperm, oocytes and embryos. There is a potential, at least, that in vivo-derived embryos resulting from infected semen might carry BVDV, although field studies so far suggest that this is very unlikely. With regard to in vitro-produced embryos, use of semen infected with any of the four viruses, with the probable exception of EBLV, will often lead to contaminated embryos, and virus removal from these embryos is difficult even when the internationally approved embryo processing protocols are used. However, it has never been demonstrated that such embryos have resulted in transmission of infection to recipients or offspring.

Lipid composition of virosomes modulates their fusion efficiency with cryopreserved bull sperm cells

Virosomes derived from different fusogenic enveloped viruses have been generated for potential application in gene targeting to sperm cells. Comparative characterization of reconstitution products revealed that virosomes derived from influenza viruses are superior to those generated from Sendai viruses, with respect to the fusion rates with cryopreserved bull sperm cells and to sperm cell vitality after fusion. Modulation of the lipid composition during virosome reconstitution affects fusion sites on target sperms and allows optimization of the fusion rate and sperm cell vitality. A fluorescence-based microscopic fusion assay combined with a vital cell stain revealed that about 90% of sperm cells fused with influenza virosomes containing exogenous cholesterol, sphingomyelin, phosphatidylcholine, and phosphatidylethanolamine. About 85% of the fused sperm cells remained vital. Such optimized influenza-derived virosomes provide the basis for ongoing experiments, which aim at eventually generating biologically active transgenic sperms.

The effect of human papillomavirus infection on sperm cell motility

OBJECTIVE

To investigate the presence of human papillomavirus (HPV) in human sperm cells and to evaluate potential effects of HPV on the sperm functions.

DESIGN

A descriptive clinical study.

PATIENT(S)

Specimens of semen were collected from 24 randomly selected patients who attended the fertility clinics at Chang Gung Memorial Hospital.

MAIN OUTCOME MEASURE(S)

The presence of HPV DNA and RNA were examined by polymerase chain reaction. Semen quality and sperm cell function were analyzed by computer-aided autoanalyzer.

RESULT(S)

Human papillomavirus type 16 DNA and RNA were found in 6 (25%) and 2 (8%) of the sperm cells specimens, respectively. Human papillomavirus type 18 DNA and RNA were present in 11 (46%) and 5 (21%) of the same sperm cells specimens, respectively. Incidence of asthenozoospermia among patients infected with either HPV was significantly higher than in those without HPV in their sperm cells (75% versus 8%). Although performance of curvilinear velocity, straight-line velocity, and mean amplitude of lateral head displacement was significantly lower in HPV-infected specimens, the differences of linearity, beat cross frequency, and straightness were not statistically significant.

CONCLUSION(S)

These results suggest that human papillomavirus can be found in human sperm cells and that certain HPV-specific genes are actively transcribed. Sperm motility parameters seem to be affected by the presence of HPV in the sperm cells, and also the incidence of asthenozoospermia may be associated with HPV infection.

Interaction of reconstituted Sendai viral envelopes with sperm cells: reconstituted Sendai virus envelope-induced fusion-mediated introduction of foreign material into bull sperm cells

Reconstituted Sendai virus envelopes (RSVE), i.e. membrane vesicles bearing the viral envelope glycoproteins and phospholipids, are able to fuse with bull sperm cells. This was inferred from the increase in the degree of fluorescence dequenching (DQ) obtained following incubation of fluorescently labeled (R18 labeled) RSVE with bull sperm cells and from electron microscopy studies of RSVE-sperm interaction. Only a low degree of DQ was observed, under the same conditions, with non-fusogenic fluorescently labeled RSVE. This, and electron microscopy results, show that binding and membrane fusion events occur between RSVE and sperm cells. In addition, DQ was observed following incubation of RSVE that had been pre-loaded with the self-quenched fluorochrome Calcein, with bull sperm cells, indicating fusion-mediated injection of the dye from the RSVE space into the sperm cells.