Vulnerability of placental antibody transfer and fetal complement synthesis to disturbance of the pregnant monkey

Transplacental Zika virus transmission in ex vivo perfused human placentas

A Zika virus (ZIKV) infection during pregnancy can result in severe birth defects such as microcephaly. To date, it is incompletely understood how ZIKV can cross the human placenta. Furthermore, results from studies in pregnant mice and non-human primates are conflicting regarding the role of cross-reactive dengue virus (DENV) antibodies on transplacental ZIKV transmission. Elucidating how ZIKV can cross the placenta and which risk factors contribute to this is important for risk assessment and for potential intervention strategies for transplacental ZIKV transmission. In this study we use an ex vivo human placental perfusion model to study transplacental ZIKV transmission and the effect that cross-reactive DENV antibodies have on this transmission. By using this model, we demonstrate that DENV antibodies significantly increase ZIKV uptake in perfused human placentas and that this increased uptake is neonatal Fc-receptor-dependent. Furthermore, we show that cross-reactive DENV antibodies enhance ZIKV infection in term human placental explants and in primary fetal macrophages but not in primary trophoblasts. Our data supports the hypothesis that presence of cross-reactive DENV antibodies could be an important risk factor for transplacental ZIKV transmission. Furthermore, we demonstrate that the ex vivo placental perfusion model is a relevant and animal friendly model to study transplacental pathogen transmission.

Zika virus is a mosquito-transmitted virus that can cause severe birth defects such as microcephaly when the infection occurs during pregnancy. Understanding how Zika virus crosses the placenta during pregnancy is important for future prevention strategies for vertical Zika virus transmission. Despite significant efforts to study this, to date it remains incompletely understood how Zika virus can cross the placenta and which risk factors contribute to this form of transmission. In this study we use an ex vivo placental perfusion model to study transplacental Zika virus transmission. The ex vivo placental perfusion model is a highly physiological and animal friendly model that mimics the in vivo conditions during pregnancy. We found that antibodies against the closely related dengue virus can significantly enhance placental uptake of Zika virus and Zika virus infection of human placental explants and fetal macrophages. These findings indicate that presence of cross-reactive dengue virus antibodies could contribute to transplacental Zika virus transmission.

The Potential Role of Nonhuman Primate Models to Better Comprehend Early Life Immunity and Maternal Antibody Transfer

Early life immunity is a complex field of research and there are still gaps in knowledge regarding the detailed mechanism of maternal antibody transfer, the impact of maternal antibodies on infant vaccine responses and the ontogeny of human early life immunity. A comprehensive understanding is necessary to identify requirements for early life vaccines and to improve early childhood immunization. New immunological methods have facilitated performing research in the youngest, however, some questions can only be addressed in animal models. To date, mostly murine models are used to study neonatal and infant immunity since they are well-described, easy to use and cost effective. Given their limitations especially in the transfer biology of maternal antibodies and the lack of infectivity of numerous human pathogens, this opinion piece discusses the potential and prerequisites of the nonhuman primate model in studying early life immunity and maternal antibody transfer.

Morphologic, stereologic, and morphometric evaluation of the nervous system in young cynomolgus monkeys (Macaca fascicularis) following maternal administration of tanezumab, a monoclonal antibody to nerve growth factor

Tanezumab, an antibody to nerve growth factor, was administered to pregnant cynomolgus monkeys at 0, 0.5, 4, and 30 mg/kg weekly, beginning gestation day (GD) 20 through parturition (∼GD165). Maternal tanezumab administration appeared to increase stillbirths and infant mortality, but no consistent pattern of gross and/or microscopic change was detected to explain the mortality. Offspring exposed in utero were evaluated at 12 months of age using light microscopy (all tissues), stereology (basal forebrain cholinergic and dorsal root ganglia neurons), and morphometry (sural nerve). Light microscopy revealed decreased number of neurons in sympathetic ganglia (superior mesenteric, cervicothoracic, and ganglia in the thoracic sympathetic trunk). Stereologic assessment indicated an overall decrease in dorsal root ganglion (thoracic) volume and number of neurons in animals exposed to tanezumab 4 mg/kg (n = 9) and 30 mg/kg (n = 1). At all tanezumab doses, the sural nerve was small due to decreases in myelinated and unmyelinated axons. Existing axons/myelin sheaths appeared normal when viewed with light and transmission electron microscopy. There was no indication of tanezumab-related, active neuron/nerve fiber degeneration/necrosis in any tissue, indicating decreased sensory/sympathetic neurons and axonal changes were due to hypoplasia or atrophy. These changes in the sensory and sympathetic portions of the peripheral nervous system suggest some degree of developmental neurotoxicity, although what effect, if any, the changes had on normal function and survival was not apparent. Overall, these changes were consistent with published data from rodent studies.

Vital and vulnerable functions of the primate placenta critical for infant health and brain development

The placenta is essential to mammalian pregnancy with many roles beyond just nutrient supply, including both endocrine and immune functions. During the course of evolution, the placenta of higher primates has acquired some unique features, including the capacity to secrete corticotropin-releasing hormone (CRH). In addition, a placental receptor for IgG enables particularly high levels of protective maternal antibody to reach the fetus before birth. This paper reviews the placental biology of primates, and discusses its involvement in adrenocortical hormone activity during pregnancy, the transfer of maternal antibody, and finally the delivery of maternal iron to the fetus, which is needed for normal brain development. An understanding of these vital functions during a full-term, healthy pregnancy provides insights into the consequences of gestational disturbances, such as maternal stress, illness, and undernutrition, which have even larger ramifications if the infant is born premature.

Development in the cynomolgus macaque following administration of ustekinumab, a human anti-IL-12/23p40 monoclonal antibody, during pregnancy and lactation

BACKGROUND

Ustekinumab is a human monoclonal antibody that binds to the p40 subunit of interleukin (IL) 12 and IL-23 and inhibits their pharmacological activity. To evaluate potential effects of ustekinumab treatment during pregnancy, developmental studies were conducted in cynomolgus macaques.

METHODS

Ustekinumab was tested in two embryo/fetal development (EFD) studies and in a combined EFD/pre and postnatal development (PPND) study. In the EFD studies, pregnant macaques (12/group) were dosed with saline or ustekinumab (9 mg/kg IV, 22.5 mg/kg SC, or 45 mg/kg IV or SC during the period of major organogenesis, gestation day [GD] 20-50). Fetuses were harvested on GD100-102 and examined for any effects on development. In the EFD/PPND study, pregnant macaques were injected with saline or ustekinumab (22.5 or 45 mg/kg SC) from GD20 through lactation day 33. Infants were examined from birth through 6 months of age for morphological and functional development. Potential effects on the immune system were evaluated by immunophenotyping of peripheral blood lymphocytes and immunohistopathology of lymphoid tissues in fetuses and infants and by T-dependent antibody response (TDAR) to KLH and TTX and by DTH response in infants. Ustekinumab concentrations were measured in serum from dams, fetus, and infants and in breast milk.

RESULTS

Ustekinumab treatment produced no maternal toxicity and no toxicity in the fetuses or infants, including no effects on the TDAR or DTH responses. Ustekinumab was present in serum from GD100 fetuses and was present in infant serum through day 120 post-birth. Low levels of ustekinumab were present in breast milk.

CONCLUSIONS

Exposure of macaque fetuses and infants to ustekinumab had no adverse effects on pre- and postnatal development.

Developmental Toxicity Testing of Biopharmaceuticals in Nonhuman Primates

Developmental toxicity studies for pharmaceutical safety testing are designed to evaluate potential adverse effects of drug treatment on pregnancy and on the developing embryo/fetus. Biopharmaceuticals present specific challenges for developmental toxicity testing because the pharmacology of these molecules, which are frequently human-specific proteins, is often restricted to humans and nonhuman primates (NHPs). For those species-restricted molecules, the only option for the evaluation of potential effects on development of the human biopharmaceutical is to use NHPs. This article reviews each of the stages of development in cynomolgus macaques (the most frequently used NHP) and the potential exposure of the embryo, fetus, and infant following administration of a biopharmaceutical during pregnancy and lactation. Because the purpose of the NHP developmental studies is to identify potential human risks, a comparison between macaque and human development and potential exposure has been made when possible. Understanding the potential exposure of the conceptus relative to critical periods in development is essential to designing a scientifically based study that adequately addresses human risks. Some options for NHP study designs, including the option of combining end points into a single study, and the pros and cons of each of the study options have been reviewed. Developmental studies for biopharmaceuticals in NHPs need to be optimally designed on a case-by-case basis taking into consideration the pharmacology of the molecule, the type of molecule (antibody or non-antibody), the potential exposure relative to the development of potential target organs, the clinical use, and the ethical considerations associated with the use of NHPs.

Maternal influenza infection during pregnancy impacts postnatal brain development in the rhesus monkey

BACKGROUND

Maternal infection with influenza and other pathogens during pregnancy has been associated with increased risk for schizophrenia and neurodevelopmental disorders. In rodent studies, maternal inflammatory responses to influenza affect fetal brain development. However, to verify the relevance of these findings to humans, research is needed in a primate species with more advanced prenatal corticogenesis.

METHODS

Twelve pregnant rhesus monkeys were infected with influenza, A/Sydney/5/97 (H3N2), 1 month before term (early third trimester) and compared with 7 control pregnancies. Nasal swabs and blood samples confirmed viral shedding and immune activation. Structural magnetic resonance imaging was conducted at 1 year; behavioral development and cortisol reactivity were also assessed.

RESULTS

Maternal infections were mild and self-limiting. At birth, maternally derived influenza-specific immunoglobulin G was present in the neonate, but there was no evidence of direct viral exposure. Birth weight and gestation length were not affected, nor were infant neuromotor, behavioral, and endocrine responses. However, magnetic resonance imaging analyses revealed significant reductions in cortical gray matter in flu-exposed animals. Regional analyses indicated the largest gray matter reductions occurred bilaterally in cingulate and parietal areas; white matter was also reduced significantly in the parietal lobe.

CONCLUSIONS

Influenza infection during pregnancy affects neural development in the monkey, reducing gray matter throughout most of the cortex and decreasing white matter in parietal cortex. These brain alterations are likely to be permanent, given that they were still present at the monkey-equivalent of older childhood and thus might increase the likelihood of later behavioral pathology.

The mind-body connection: not just a theory anymore

The field of psychoneuroimmunology has witnessed an explosion of empirical findings during the last two decades. Research has documented the mechanisms through which stressful emotions alter white blood cell function. Stress diminishes white blood cell response to viral infected cells and to cancer cells. Moreover, vaccination is less effective in those who are stressed and wounds heal less readily in those who are stressed. While stress decreases the activity of some white blood cells, stress does not compromise the function of all types of white blood cells. Indeed, some types of autoimmune disease, which involve particular subsets of white blood cells, are exacerbated by stress. The literature documents the efficacy of talk-therapy interventions in altering immune system parameters and enhancing the body's ability to combat disease. The literature also documents the impact of the chronic stress of poverty on immune system function.

Effects of an anti-TNF-alpha monoclonal antibody, administered throughout pregnancy and lactation, on the development of the macaque immune system

PROBLEM

The use of anti-TNF-alpha therapies during pregnancy and lactation on the development of the neonatal immune system has not been fully established. The purpose of this study was to evaluate whether treatment of macaques with an anti-TNF-alpha monoclonal antibody (golimumab) during pregnancy and lactation would result in defects in the developing immune system.

METHOD OF STUDY

Pregnant macaques were treated with golimumab during pregnancy and lactation. Immune system development was evaluated by histopathology, lymphocyte subset analysis and functional challenging of the infant immune system (humoral immune response to KLH and TTX, and DTH skin reaction).

RESULTS

In utero and postnatal exposure to golimumab had no effect on T and B cell populations in blood and lymphoid tissues and did not impair the ability of the infants to mount an immune response to antigen challenge.

CONCLUSION

Treatment of pregnant macaques with golimumab throughout pregnancy and lactation did not affect the development and maturation of the immune system in the offspring.

Nonhuman primate models of intrauterine cytomegalovirus infection

Congenital human cytomegalovirus (HCMV) infection has long been recognized as a threat to the developing fetus, even though studies have shown that only a subset of congenital infections results in clinical signs of disease. Among the estimated 8000 children who develop sequelae from congenital CMV infection each year in the United States alone, most suffer permanent developmental defects within the central nervous system. Because there is currently no approved vaccine for HCMV, and anti-HCMV drugs are not administered to gravid women with congenital infection because of potential toxicity to the fetus, there is a clear clinical need for effective strategies that minimize infection in the mother, transplacental transmission of the virus, and/or fetal disease. Animal models provide a method to understand the mechanisms of HCMV persistence and pathogenesis, and allow for testing of novel strategies that limit prenatal infection and disease. The rhesus macaque model is especially well suited for these tasks because monkeys and humans share strong developmental, immunological, anatomical, and biochemical similarities due to their close phylogenetic relationship. This nonhuman primate model provides an invaluable system to accelerate the clinical development of promising new therapies for the treatment of human disease. This review addresses salient findings with the macaque model as they relate to HCMV infection and potential avenues of discovery, including studies of intrauterine CMV infection. The complexity of the natural history of HCMV is discussed, along with the ethical and logistical issues associated with studies during pregnancy, the recent contributions of animal research in this field of study, and future prospects for increasing our understanding of immunity against HCMV disease.

Developmental consequences of antenatal dexamethasone treatment in nonhuman primates

Research assessing fetal exposure to dexamethasone and betamethasone in animals has raised concerns about the potential for adverse side effects following antenatal treatments, not withstanding the beneficial and desired improvement in lung function. Some of the inhibitory effects on physical growth and the long-term alterations in endocrine, immune and neural physiology may reflect species differences in the fetal sensitivity of rodents and monkeys to corticosteroids or perhaps could be attributed to the higher drug doses often used in animal studies. However, since steroidal drugs can be administered for extended periods in clinical practice, and also are occasionally given in the range found to cause significant effects on the brain and immune responses of infant monkeys, the simian studies have important cautionary implications for obstetrical and pediatric practice.

Impact of maternal stress on the transmammary transfer and protective capacity of herpes simplex virus-specific immunity

In adults, psychological stress regulates immune responsiveness in part via the increased levels of corticosterone that are produced as a result of hypothalamic-pituitary-adrenal (HPA) axis activation. However, there is a lack of knowledge as to the role such regulation may play in the neonate. Neonates are severely compromised in their ability to generate an immune response to pathogens encountered after birth and therefore rely heavily on maternally derived antibody acquired postnatally through the milk. This passive transfer of antibody is critical for protection of the neonate from severe herpes simplex virus (HSV) infection and mortality. Using a well-established postnatal restraint/light stress model, we determined whether maternal stress and the associated increases in corticosterone would affect the transmammary transfer of antibody and subsequent neonate susceptibility to HSV-associated mortality. Serum corticosterone levels were markedly increased in lactating mice subjected to the restraint/light stress, and increased levels of corticosterone were transferred through the milk of these stressed mothers to their neonates. Despite these increases in corticosterone, the transmammary transfer and accumulation of total and HSV-specific IgG in neonate serum remained intact. This milk-derived, HSV-specific antibody alone protected the neonate from systemic viral spread. Interestingly, postnatal maternal stress significantly increased neonate survival after HSV-2 infection despite no apparent alteration in viral spread. These studies demonstrate that although the transmammary transfer of antibody is unaffected by maternal stress, stress may be enhancing components of antiviral immunity that are effective in protecting neonates from HSV-associated mortality.

Perinatal corticosteroids: A review of research. Part I: Antenatal administration

The premature infant may receive therapeutic glucocorticoid drugs while in utero or in the postnatal period. This article (part I of a two-part series) discusses the benefits and risks of in utero, or antenatal, corticosteroids (ACS) for the premature infant. Part II addresses the benefits and risks of postnatal corticosteroid (PCS) use. There are numerous clinical studies on the therapeutic use of these steroids for the prevention of respiratory distress syndrome and chronic lung disease in the premature infant, although research results on the efficacy of repeated steroid exposure among premature infants vary. Premature infants who are exposed to repeated courses of ACS and/or high-cumulative-dose PCS may show no neurologic side effects until later in life. Research in newborn animal models focused on the timing, duration, and amounts of ACS and PCS. Current clinical research includes examination of the neurodevelopment of infants who are therapeutically exposed to perinatal corticosteroids, to identify safer minimal dose protocols. Over the past 30 years, corticosteroids have been increasingly prescribed before and after birth. Understanding the potential treatment benefits and risks to human fetuses and neonates is vital to clinical practice. This review presents historic and pharmacokinetic information about prenatal use of corticosteroids. It also offers scientific evidence of the benefits and risks identified in animal models and clinical trials, to stimulate thought that gtiides neonatal clinical practice.

Postpartum maternal corticosterone decreases maternal and neonatal antibody levels and increases the susceptibility of newborn mice to herpes simplex virus-associated mortality

The effects of corticosterone on the transmammary transfer of herpes simplex virus (HSV)-specific antibody and the ability of the neonate to survive HSV-2 infection were assessed. Increased postpartum maternal corticosterone reduced the levels of total and HSV-specific IgG in the serum and milk of mothers. Neonates nursed by these mothers received increased levels of corticosterone and decreased levels of total and HSV-specific IgG. Accordingly, these neonates were more susceptible to HSV-2-associated mortality; however, survival was restored through passive immunization with HSV-specific antibody. These studies demonstrate that postpartum elevations in corticosterone compromise a mother's ability to provide protective antibody to their offspring.

Transplacental transfer and subsequent neonate utilization of herpes simplex virus-specific immunity are resilient to acute maternal stress

Neonates are severely compromised in the ability to generate an immune response to pathogens and thus rely heavily on maternally derived immunity that is acquired by transplacental and transmammary means. The passive transfer of maternal herpes simplex virus (HSV)-specific antibody is critical in determining the outcome of neonatal HSV infection. In adults, psychological stress alters immune responsiveness via the increased level of corticosterone that is produced as a result of hypothalamic-pituitary-adrenal axis activation. Although the behavioral and neuroendocrine effects of pre- and postnatal stress-induced increases in corticosterone are well documented, the effects of maternal stress on the efficacy of prenatally transferred and neonatally developed viral immunity has yet to be addressed. By using a well-established prenatal restraint-and-light stress mouse model, we investigated the effects of increased maternal corticosterone on the passive transfer of total and HSV-specific immunoglobulin G (IgG) antibody and subsequent neonatal susceptibility to HSV infection. Serum corticosterone levels in pregnant mice were significantly increased in response to restraint-and-light stress, and fetuses derived from these stressed mice had significantly elevated levels of corticosterone. Despite the increases in corticosterone, the passive transfer of total and HSV-specific IgG antibody persisted and, in turn, protected the neonate from systemic viral spread. Therefore, prenatal stress did not increase the susceptibility of neonates to HSV type 2-associated mortality. These findings demonstrate the resiliency of the passive transfer of protective HSV-specific immunity under conditions of acute psychological stress.

Critical periods of special health relevance for psychoneuroimmunology

Although it is possible to demonstrate an influence of psychological factors on immune responses at any point in the life span, there are two periods when the effects may have greater implications for health. Our research with nonhuman primates indicates that the immaturity of a young infant's immune responses makes it more vulnerable, especially during the fetal and neonatal stages. Similarly, the natural, age-related process of immune senescence creates a second period of increased risk in elderly animals and people. This review summarizes findings from a 20-year research program, which support the conclusion that we should give special attention to the age of the host in psychoneuroimmunology studies.

Serum kappa and lambda light immunoglobulin chains in cynomolgus macaques (Macaca fascicularis) during the first twenty months of age

Growth is coupled to physiological modifications of the immune system which reaches the functional capabilities according to age-related milestones. Few data are available on the circulating immunoglobulin levels and no data exist on total immunoglobulin light chains in infant macaques. Therefore we studied by a nephelometric assay, the age-dependent variations of kappa and lambda serum light chains in the experimental animal model Macaca fascicularis during the first 20 months of age. Both kappa and lambda showed a marked increase in their concentrations during the first 7-8 months of life. Infants' light chain levels were anyhow significantly lower than those of the nursing dams and of the control group, never attaining, even at the 20th month, the same concentration as the adult, although the value of the kappa/lambda ratio was apparently the same.

Humoral immunity factors in cynomolgus macaques (Macaca fascicularis) serum: immunoglobulins and total light chains in nursing dams

This study was aimed at the identification of variations in humoral immunity parameters during the lactation period in macaque females, a recognized model in reproductive physiology and pathology. The importance of such evaluation is evidenced in particular by the central role played by the maternally transferred immunity to the progeny. The trends of serum immunoglobulins and light chains were characterized by immunonephelometry during the 6-months of lactation. The levels attained by nursing females were evaluated against a control group. The main modifications induced by lactation were in the IgM class, whose levels remained constantly lower than in the control group; the other Igs, even if showing different trends, returned to levels comparable to the control group by the end of the sixth month. Light chains quantification evidenced a significant decrease in Kappa levels; Lambda chains showed a similar trend. The variation of the Kappa/Lambda ratio was therefore minimal.

Prenatal stress alters immune function in the offspring of rats

Pregnant rats were either exposed to restraint under bright lights for 45 min three times daily (n = 7) or were left undisturbed (n = 8) during Days 14-21 of gestation. Offspring were tested for cellular immune responses as measured by Concanavalin A-stimulated proliferation and Natural Killer (NK) cytotoxicity of splenocytes as juveniles or adults, or were tested for specific humoral immune responses to in vivo challenge with the antigen Keyhole Limpet Hemocyanin (KLH) as adults. Results indicated that: (a) Proliferation did not vary as a function of sex or prenatal treatment in either juvenile or adult offspring; (b) in juveniles NK cytotoxicity was marginally lower in males as compared to females, and was also marginally reduced by prenatal stress in males but not females, whereas in adults, NK cytotoxicity was marginally enhanced by prenatal stress in both sexes; and (c) prenatally stressed offspring of both sexes had higher levels of anti-KLH antibodies as compared to controls.