Normal calves produced after transfer of in vitro fertilized embryos cultured with an antiviral compound

The mammalian preimplantation embryo: Its role in the environmental programming of postnatal health and performance

During formation of the preimplantation embryo several cellular and molecular milestones take place, making the few cells forming the early embryo vulnerable to environmental stressors than can impair epigenetic reprogramming and controls of gene expression. Although these molecular alterations can result in embryonic death, a significant developmental plasticity is present in the preimplantation embryo that promotes full-term pregnancy. Prenatal epigenetic modifications are inherited during mitosis and can perpetuate specific phenotypes during early postnatal development and adulthood. As such, the preimplantation phase is a developmental window where developmental programming can take place in response to the embryonic microenvironment present in vivo or in vitro. In this review, the relevance of the preimplantation embryo as a developmental stage where offspring health and performance can be programmed is discussed, with emphasis on malnutrition and assisted reproductive technologies; two major environmental insults with important implications for livestock production and human reproductive medicine.

Offspring physiology following the use of IVM, IVF and ICSI: a systematic review and meta-analysis of animal studies

BACKGROUND

Since the birth of the first baby using IVF technology in 1978, over 10 million children have been conceived via ART. Although most aspects of ARTs were developed in animal models, the introduction of these technologies into clinical practice was performed without comprehensive assessment of their long-term safety. The monitoring of these technologies over time has revealed differences in the physiology of babies produced using ARTs, yet due to the pathology of those presenting for treatment, it is challenging to separate the cause of infertility from the effect of treatments offered. The use of systematic review and meta-analysis to investigate the impacts of the predominant ART interventions used clinically in human populations on animals produced in healthy fertile populations offers an alternative approach to understanding the long-term safety of reproductive technologies.

OBJECTIVE AND RATIONALE

This systematic review and meta-analysis aimed to examine the evidence available from animal studies on physiological outcomes in the offspring conceived after IVF, IVM or ICSI, compared to in vivo fertilization, and to provide an overview on the landscape of research in this area.

SEARCH METHODS

PubMed, Embase and Commonwealth Agricultural Bureaux (CAB) Abstracts were searched for relevant studies published until 27 August 2021. Search terms relating to assisted reproductive technology, postnatal outcomes and mammalian animal models were used. Studies that compared postnatal outcomes between in vitro-conceived (IVF, ICSI or IVM) and in vivo-conceived mammalian animal models were included. In vivo conception included mating, artificial insemination, or either of these followed by embryo transfer to a recipient animal with or without in vitro culture. Outcomes included birth weight, gestation length, cardiovascular, metabolic and behavioural characteristics and lifespan.

OUTCOMES

A total of 61 studies in five different species (bovine, equine, murine, ovine and non-human primate) met the inclusion criteria. The bovine model was the most frequently used in IVM studies (32/40), while the murine model was mostly used in IVF (17/20) and ICSI (6/8) investigations. Despite considerable heterogeneity, these studies suggest that the use of IVF or maturation results in offspring with higher birthweights and a longer length of gestation, with most of this evidence coming from studies in cattle. These techniques may also impair glucose and lipid metabolism in male mice. The findings on cardiovascular outcomes and behaviour outcomes were inconsistent across studies.

WIDER IMPLICATIONS

Conception via in vitro or in vivo means appears to have an influence on measurable outcomes of offspring physiology, manifesting differently across the species studied. Importantly, it can be noted that these measurable differences are noticeable in healthy, fertile animal populations. Thus, common ART interventions may have long-term consequences for those conceived through these techniques, regardless of the pathology underpinning diagnosed infertility. However, due to heterogeneous methods, results and measured outcomes, highlighted in this review, it is difficult to draw firm conclusions. Optimizing animal and human studies that investigate the safety of new reproductive technologies will provide insight into safeguarding the introduction of novel interventions into the clinical setting. Cautiously prescribing the use of ARTs clinically may also be considered to reduce the chance of promoting adverse outcomes in children conceived before long-term safety is confidently documented.

Emerging diseases in international trade in embryos

A significant change in cattle production and germplasm exchange has occurred over the past 50 years. The growth of artificial reproductive technologies and their broad implementation has become commonplace. The production and subsequent import and export of semen and embryos throughout the world has increased significantly. The embryo transfer industry has reached a new record of growth, with approximately 1.5 million transferrable bovine embryos collected and/or produced in 2018. Over 1 million of these embryos were produced invitro . The increased production of invitro -produced embryos leads to greater opportunities involving international trade. However, further research concerning emerging pathogens is imperative to ensure the efficacy and safety of the embryo transfer industry. Appropriate biosecurity protocols, including reliable testing methodology and effective embryo processing procedures, are key in preventing disease due to emerging and re-emerging pathogens that can be transmitted via embryo transfer.

ANTIVIRAL COMPOUNDS AND PREPARATIONS EFFECTIVE AGAINST BOVINE VIRAL DIARRHEA

Bovine viral diarrhea virus (BVDV) belongs to the genus Pestivirus, family Flaviviridae. It causes various clinical forms of infection leading to significant economic losses in beef and dairy industry worldwide. Furthermore, the virus is a contaminant of biological preparations (bovine fetal serum, continuous cell cultures, vaccines for human and veterinary medicine, interferons, trypsin, biotechnological preparations, embryos, stem cells, etc.). It is used as a test object when developing methods of decontamination. In some countries, a tool for monitoring the infection caused by the virus is vaccination based on the use of live and inactivated vaccines with varying efficiency. The antiviral compounds are a potential means of control in case of insufficient efficacy of vaccines. Their advantage for BVDV control is the ability to provide immediate protection for animals at risk in the case of an outbreak of the disease. This review summarizes the current state of knowledge about antiviral compounds against BVDV. It was noted that due to the use of advanced biomedical technologies there is a tendency to search for drugs that might be effective for antiviral therapy of BVDV, as indicated by numerous studies of new compounds and the antiviral efficacy of known drugs used in medical practice. In addition to the well-known antiviral targets for the virus, such as the RdRp, IMPDH, NS3, new targets were discovered, such as protein p7. Its mechanism of action remains to be explored. It can be concluded that there is a great potential for BVDV control through the use of antiviral drugs which has not yet implemented. The biggest obstacle for commercial implementation of identified compounds is the lack of demonstration of their efficacy in vivo. Further studies should be performed to develop a method for administering effective drugs to groups of animals.

Potential applications for antiviral therapy and prophylaxis in bovine medicine

Viral disease is one of the major causes of financial loss and animal suffering in today's cattle industry. Increases in global commerce and average herd size, urbanization, vertical integration within the industry and alterations in global climate patterns have allowed the spread of pathogenic viruses, or the introduction of new viral species, into regions previously free of such pathogens, creating the potential for widespread morbidity and mortality in naïve cattle populations. Despite this, no antiviral products are currently commercially licensed for use in bovine medicine, although significant progress has been made in the development of antivirals for use against bovine viral diarrhea virus (BVDV), foot and mouth disease virus (FMDV) and bovine herpesvirus (BHV). BVDV is extensively studied as a model virus for human antiviral studies. Consequently, many compounds with efficacy have been identified and a few have been successfully used to prevent infection in vivo although commercial development is still lacking. FMDV is also the subject of extensive antiviral testing due to the importance of outbreak containment for maintenance of export markets. Thirdly, BHV presents an attractive target for antiviral development due to its worldwide presence. Antiviral studies for other bovine viral pathogens are largely limited to preliminary studies. This review summarizes the current state of knowledge of antiviral compounds against several key bovine pathogens and the potential for commercial antiviral applications in the prevention and control of several selected bovine diseases.

Shaping the norms that regulate international commerce of embryos

As various embryo technologies in livestock were developed and evolved to a state of usefulness over the past 40 years, scientists with a specific interest in infectious diseases sought to determine the epidemiologic consequences of movement, especially international movement, of increasing numbers of embryos. Many of the foundational studies in this area were reported in Theriogenology, beginning in the 1970s and especially throughout the 1980s and 1990s. Unquestionably, Theriogenology has been a widely used venue for dissemination of basic information on this subject, which ultimately led to the development of the now universally accepted techniques for certification of embryo health. Today it is well-recognized that movement in commerce of embryos, especially in vivo-derived embryos, is a very low-risk method for exchange of animal germ plasm. This paper chronicles the evolution of strategies for health certification of embryos. An overview is provided of the calculated efforts of practitioners, scientists, and regulators to organize, forge necessary partnerships, stimulate needed research, provide purposeful analysis of the results, and, through these processes, guarantee the universal acceptance of efficient protocols for certifying the health of embryos intended for movement in international commerce.

Evaluation of the effectiveness of semen processing techniques to remove bovine viral diarrhea virus from experimentally contaminated semen samples

The aim of this study was to evaluate the capacity of three semen processing techniques, Percoll gradient centrifugation, Swim-up and a combination of Swim-up and Percoll gradient centrifugation, to reduce the viral load of bovine viral diarrhea virus (BVDV) in experimentally infected semen samples. The evaluation was performed using two approaches: first, searching for the presence of virus in the processed samples (via virus titration and RT-PCR) and second, ascertaining the possible interference on in vitro embryo production. The sperm count and DNA integrity (Comet assay) of the processed samples were analyzed (Experiment 1). The amount of virus in the processed samples was determined by titration in cell culture (Experiment 2). The samples processed by Swim up/Percoll gradient centrifugation were utilized for in vitro embryo production, and the embryos produced were tested for BVDV by RT-PCR (Experiment 3). Sperm concentration, Comet assay and embryo production were analyzed by chi-squared tests (P<0.05). There was a significant difference between sperm separation techniques when the sperm count and Comet assay were analyzed. The sperm count obtained from the Swim up/Percoll gradient centrifugation group was lower than that obtained in either of the two other groups (Swim up and Percoll gradient centrifugation), and the Comet assay showed that the combination of the two semen processing techniques (Swim up/Percoll gradient) produced a 1.1% prevalence of Comet level 2, which was not observed in the other groups. The BVDV titer (10(6.68)TCID(50)/mL) added to experimentally infected semen samples decreased after Percoll gradient centrifugation to 10(2.3)-10(1)TCID(50)/mL; for the Swim up group, the titer range was 10(3.3)-10(1.87)TCID(50)/mL, and in the Swim up/Percoll gradient centrifugation group, BVDV was undetectable. The decreases in titer varied from 99.9% in the Swim up-processed group to 100% in the Swim up/Percoll gradient centrifugation group. In vitro embryo production displayed similar blastocyst development rates among all groups, and RT-PCR was negative for the produced embryos. The data showed that the combination of Swim up/Percoll gradient centrifugation promoted the elimination of BVDV from the semen samples without damaging spermatozoa cells and also allowed successful in vitro embryo production free of BVDV. Hence, the risk of BVDV contamination is negligible for the embryo recipient.

Antiviral treatment of calves persistently infected with bovine viral diarrhoea virus

BACKGROUND

Animals persistently infected (PI) with bovine viral diarrhoea virus (BVDV) are a key source of viral propagation within and among herds. Currently, no specific therapy exists to treat PI animals. The purpose of this research was to initiate evaluation of the pharmacokinetic and safety data of a novel antiviral agent in BVDV-free calves and to assess the antiviral efficacy of the same agent in PI calves.

METHODS

One BVDV-free calf was treated with 2-(2-benzimidazolyl)-5-[4-(2-imidazolino)phenyl]furan dihydrochloride (DB772) once at a dose of 1.6 mg/kg intravenously and one BVDV-free calf was treated three times a day for 6 days at 9.5 mg/kg intravenously. Subsequently, four PI calves were treated intravenously with 12 mg/kg DB772 three times a day for 6 days and two PI control calves were treated with an equivalent volume of diluent only.

RESULTS

Prior to antiviral treatment, the virus isolated from each calf was susceptible to DB772 in vitro. The antiviral treatment effectively inhibited virus for 14 days in one calf and at least 3 days in three calves. Subsequent virus isolated from the three calves was resistant to DB772 in vitro. No adverse effects of DB772 administration were detected.

CONCLUSIONS

Results demonstrate that DB772 administration is safe and exhibits antiviral properties in PI calves while facilitating the rapid development of viral resistance to this novel therapeutic agent.

Normal reproductive capacity of heifers that originated from in vitro fertilized embryos cultured with an antiviral compound

Bovine viral diarrhea virus (BVDV) can associate with in vitro fertilized (IVF) bovine embryos despite washing and trypsin treatment. An antiviral compound, DB606 (2-(4-[2-imidazolinyl]phenyl)-5-(4-methoxyphenyl)furan), inhibits the replication of BVDV in bovine uterine tubal epithelial cells, Madin Darby bovine kidney cells, and fetal fibroblast cells. As well, DB606 in in vitro culture medium does not affect embryonic development. Antiviral-treated-IVF embryos placed into recipients developed into clinically normal calves. The objective of this project was to determine if these resultant heifer calves were capable of reproducing. Seven heifers from each of the treatment groups (natural breeding, IVF embryo, and IVF embryo cultured in DB606) of the previous study were used. At 20-27 months of age, the heifers were exposed to a fertile bull in a single pasture during a 63 d breeding season. Five of the seven heifers originating from natural breeding were pregnant 35 d after removal of the bull and calved. All of the heifers resulting from transfer of untreated IVF embryos were pregnant at 35 d; however, one aborted the fetus at 5-7 months of gestation. All of the heifers derived from transfer of IVF embryos cultured in DB606 were pregnant and calved. Offspring from dams of all treatment groups were clinically normal at birth. Adjusted 205 d weaning weights were not significantly different among the offspring of the treated and untreated dams. These results indicate that culture of bovine-IVF embryos in DB606 does not impair future reproductive capacity of resulting heifers.

Bovine viral diarrhea virus (BVDV): Epidemiologic concerns relative to semen and embryos

Artificial insemination and embryo transfer are used commonly in cattle production and exchange of germplasm between populations of cattle. If properly monitored, assisted reproductive techniques can be used to prevent the spread of infectious agents. However, these techniques potentially represent unnatural routes for transmission of diseases. Bovine viral diarrhea virus (BVDV) is broadly distributed among the world's populations of cattle. Fluids, gametes and somatic cells from infected animals are likely contaminated with the virus. Thus, use of semen or embryos from infected animals could result in spread of BVDV. This paper provides an overview of the risks of transmitting this virus by AI or production and transfer of embryos and summarizes the precautions needed to prevent such transmissions of disease from occurring.

Risk assessment of transmission of bovine viral diarrhea virus (BVDV) in abattoir-derived in vitro produced embryos

Bovine virus diarrhea virus (BVDV) is a pathogen of the bovine reproductive system causing reduced conception rates, abortions and persistently infected calves. Most if not all strains of BVDV are transmissible by natural mating and AI. For international trade, it is recommended that in vitro fertilized embryos be washed according to the IETS Manual. However, BVDV may not be entirely washed out, resulting in possible transmission risks to recipients. Donor cows, donor bulls and biological agents are all possible sources of contamination. The process for producing in vitro produced (IVP) embryos is complex and non-standard, and some procedures can contribute to spread of BVDV to uninfected embryos. The structure of the zone pellucida (ZP) of IVP embryos permits adherence of BVDV to the ZP. To estimate the risk of producing infected recipients and persistently infected calves from abattoir-derived IVP embryos, a quantitative risk assessment model using Microsoft Excel and Palisade @Risk was developed. Assumptions simplified some of the complexities of the IVP process. Uncertainties due to incomplete or variable data were addressed by incorporating probability distributions in the model. Model variables included: disease prevalence; the number of donor cows slaughtered for ovaries; the number of oocytes collected, selected and cultured; the BVDV status of ovaries, semen, biological compounds and its behavior in the IVP embryo process. The model used the Monte Carlo method to simulate the IVP process. When co-culture cells derived from donor cows of unknown health status were used for in vitro culture (IVC), the probability of a recipient cow at risk of infection to BVDV per oocyte selected for IVP processing averaged 0.0006. However, when co-culture free from BVDV was used, the probability was 1.2 x 10(-5). Thus, for safe international trade in bovine IVP embryos (i.e. negligible risks of transmission of BVDV), co-culture cells, if used during IVC for producing IVP embryos, should be disease-free.

Disinfection procedures for controlling microorganisms in the semen and embryos of humans and farm animals

Semen and embryos generated by assisted reproductive techniques (ARTs) may be contaminated with numerous microorganisms. Contamination may arise from systemic or local reproductive tract infections in donors or the inadvertent introduction of microorganisms during ARTs, and may lead to disease transmission. This review describes sanitary procedures which have been investigated to ascertain whether they are effective in rendering semen and embryos free of pathogenic microorganisms, including internationally adopted washing procedures, which can be supplemented by antibiotics and enzymatic treatments. Other methods include treatment with antibodies or ozone, photoinactivation, acidification, and the use of novel antiviral compounds. In conclusion, despite the wide range of antimicrobial procedures available, none can be recommended as a universal disinfection method for rendering semen and embryos free from all potentially pathogenic microorganisms. However, some procedures are unsuitable, as they can compromise the viability of semen or embryos. In humans, washing by the gradient centrifugation method appears to be effective for reducing the microbial population in semen and is harmless to the spermatozoa. A useful procedure for embryos involving multiple washes in sterile medium has much to commend it for the prevention of disease transmission; furthermore, it is recommended by the International Embryo Transfer Society (IETS).

Mammalian embryo co-culture: Trials and tribulations of a misunderstood method

Embryo-somatic cell co-culture was devised over 40 years ago in an attempt to improve the development and viability of mammalian preimplantation embryos generated and cultured in vitro. While initial endeavours were successful in this respect, other studies soon highlighted a number of significant long-term detrimental impacts of this approach. Surprisingly little is known about the mechanisms underlying the beneficial effects of co-culture, although the production of embryotrophic compounds, modulation of nutrient profile, protection against culture-induced stress and/or toxin clearance are all contenders. The extent to which the inadvertent exposure of embryos to serum accounts for many of these effects remains open to question. Although the popularity of somatic cell co-culture has recently declined in favour of the use of sequential media due to concerns associated with its risk of disease transmission and long-term sequelae, we argue that complete dismissal of this technique is ill advised, given that our limited understanding of basic somatic cell interactions has prevented us from fully exploiting its potential. In this respect, there is some merit in focussing future research strategies based on reconstructed maternal tract tissue. Although the use of co-culture in clinical practice is unacceptable and its implementation in domestic species for commercial purposes should be viewed with diffidence, this technique can still provide a wealth of information on the development of novel, more physiological embryo in vitro culture systems. The proviso for acquiring such information is to gain a fuller understanding of the culture requirements/biochemistry of somatic cells and their interaction with the early conceptus.

Sanitary control in bovine embryo transfer How far should we go? A review

Embryo transfer is a globally executed technique which, when properly done, has both economic and sanitary advantages. International guidelines are available to prevent infection of the embryo with pathogens, both originating from the donor animals as from the environment. This manuscript describes the bacteria, viruses, protozoa, fungi and prions that are of major concern in the context of embryo transfer in cattle. In addition, the actual scientific knowledge on these pathogens is evaluated in terms of the current international and national guidelines and legislation.