Interacting impact of maternal inflammatory response and stress on the amygdala transcriptome of pigs

Changes at the molecular level capacitate the plasticity displayed by the brain in response to stress stimuli. Weaning stress can trigger molecular changes that influence the physiology of the offspring. Likewise, maternal immune activation (MIA) during gestation has been associated with behavior disorders and molecular changes in the amygdala of the offspring. This study advances the understanding of the effects of pre- and postnatal stressors in amygdala gene networks. The amygdala transcriptome was profiled on female and male pigs that were either exposed to viral-elicited MIA or not and were weaned or nursed. Overall, 111 genes presented interacting or independent effects of weaning, MIA, or sex (FDR-adjusted P-value <0.05). PIGY upstream reading frame and orthodenticle homeobox 2 are genes associated with MIA-related neurological disorders, and presented significant under-expression in weaned relative to nursed pigs exposed to MIA, with a moderate pattern observed in non-MIA pigs. Enriched among the genes presenting highly over- or under-expression profiles were 24 Kyoto Encyclopedia of Genes and Genomes pathways including inflammation, and neurological disorders. Our results indicate that MIA and sex can modulate the effect of weaning stress on the molecular mechanisms in the developing brain. Our findings can help identify molecular targets to ameliorate the effects of pre- and postnatal stressors on behaviors regulated by the amygdala such as aggression and feeding.

PSV-6 Detection of sex-by-maternal immune activation effects on the molecular pathways of the pig amygdala

The prolonged and sex-dependent impact of maternal immune activation (MIA) on the molecular pathways of the amygdala, a brain region that influences social, cognitive, and sexually dimorphic behaviors, is only partially understood. To address this gap, the effect of MIA elicited by porcine reproductive and respiratory syndrome virus (PRRSV) infection during gestation on the amygdala transcriptome of pigs was studied. Gene expression levels were measured using RNA-Seq on the amygdala for 3-week-old female and male offspring from MIA and control groups. Among the 328 genes that exhibited an MIA-by-sex effect, the majority annotated to functional categories relevant to behavioral abnormalities, including neuroactive ligand-receptor pathways, glutamatergic functions, and neuropeptide systems. Genes in these categories included corticotropin releasing hormone receptor 2, glutamate metabotropic receptor 4, glycoprotein hormones, alpha polypeptide, parathyroid hormone 1 receptor, vasointestinal peptide receptor 2, neurotensin, proenkephalin, and gastrin releasing peptide. These genes and functional categories have been associated with MIA-related schizophrenia and autism spectrum behavior disorders. The transcript and network dysregulation uncovered in this study advances the understanding necessary to develop treatments that ameliorate the effects of neurodevelopmental disorders caused by gestational MIA exposure. This study is supported by USDA NIFA AFRI, grant number 2018-67015-27413.

PSVIII-1 A transcriptomic study of the effect of PRRSV infection during gestation on the piglet amygdala

Porcine reproductive and respiratory syndrome virus (PRRSV) is an economic burden on the swine industry, resulting in losses not only related to animal death but also to reduced offspring productivity. Understanding the underlying molecular pathways that contribute to decreased feed efficiency and behaviors that result in poorer performance is important for the implementation of management practices that aim to mitigate the effects of PRRSV. To uncover the long-term effects of PRRSV infection during gestation, a transcriptome analysis of the amygdala of 22-day-old piglet offspring from maternal PRRSV activated and control gilts was undertaken. Overall, 161 genes were differentially expressed between the PRRSV and control piglet offspring. Many of the genes were over-expressed in pigs from PRRSV compared to control gilts, such as interferon induced transmembrane protein 3 and neuron derived neurotrophic factor. Few genes were under-expressed, including insulin-like growth factor 2 and aldehyde dehydrogenase 1 family member A1. The detection of these dysregulated genes and the directionality of their differential expression yielded insights into the effects that maternal PRRSV infection has on the neural pathways of the offspring amygdala. This furthers our understanding of molecular processes underlying pathological behaviors that may be exhibited by these pigs, affecting management and production. This study is supported by USDA NIFA AFRI, grant number 2018-67015-27413.

PSVIII-19 PRRSV infection during gestation eliciting changes in piglet sickness behaviors following an immune challenge

The pork industry faces financial losses associated with outbreaks in porcine reproductive and respiratory virus (PRRSV). One type of loss stems from the effect of PRRSV-elicited maternal immune activation during gestation on the response of pigs to a second immune challenge later in life. The objective of this study was to assess the effects of PRRSV infection during gestation, a second immune challenge, and sex on pig behavior. Camborough gilts were inoculated with PRRSV or saline (Controls) during the last third of gestation. The piglets from these gilts were weaned at day 21, and were injected with Poly(I:C) to elicit a second immune challenge, similarly to a viral infection, or with Saline on day 60. Post injection, behaviors were recorded in 5-minute intervals for one hour by a trained experimenter. Recorded behaviors included laying, standing, and panting, and totaled 624 observations per behavior on 51 pigs from 10 gilts. The logistic generalized mixed effect model used to describe behavior included the effects of gilt and pig treatments, sex, and interactions, and accounted for the random effect of gilt, and repeated measurements within pig. Panting showed a significant gilt challenge-by-sex-by-pig treatment interaction effect (P &lt; 0.031). The Poly(I:C) challenge had a significant and positive effect on panting among male pigs from Control gilts (P &lt; 0.001), while this effect was not observed in pigs from PRRSV-treated gilts. Among female pigs challenged with Poly(I:C), PRRSV treatment has a significant effect on lateral laying (P &lt; 0.015) and standing (P &lt; 0.042). Pigs from PRRSV-treated gilts were less active than from Control gilts. Our results highlight that the effect on behaviors of immune challenge later in life depend on the exposure of pigs to PRRSV during gestation. This study is supported by USDA NIFA AFRI, grant number 2018-67015-27413.

Long-Lasting Impact of Maternal Immune Activation and Interaction With a Second Immune Challenge on Pig Behavior

The combined effects on pig behavior of maternal immune challenge during gestation followed by a second immune challenge later in life have not been studied. Porcine reproductive and respiratory syndrome virus (PRRSV) infection during gestation can elicit maternal immune activation (MIA) yet the interactions with the offspring response to a second immune challenge after birth remains unexplored. Knowledge on the response to viral challenges in rodents has been gained through the use of the viral mimetic polyinosinic-polycytidylic acid (Poly(I:C)), yet the effects of this immune stimulant on pig behavior have not been assessed. This study advances the understanding of the combined effect of MIA and a second immune challenge later in life on female and male pig behavior. Three complementary experiments enabled the development of an effective Poly(I:C) challenge in pigs, and testing the interaction between PRRSV-elicited MIA, Poly(I:C) challenge at 60 days of age, and sex on behaviors. Individual-level observations on sickness, locomotor, and social behaviors were measured 1-3 h after Poly(I:C) challenge. Vomiting, panting, lethargy, walking, laying, playing, and touching behaviors were analyzed using generalized linear mixed effect models. Results indicated that a Poly(I:C) dose of 1 mg/kg within 1 h after injection increased the incidence of laying and sickness behavior. The Poly(I:C) challenge decreased the incidence of locomotor behaviors and activity levels. Pigs exposed to MIA had lower rates of social behaviors such as playing. The combined effect of PRRSV-elicited MIA and Poly(I:C) immune challenge further sensitized the pigs to behavior disruption across sexes including changes in sternal and lateral laying, walking, lethargy, and touching incidence. Notably, the effects of Poly(I:C) immune challenge alone on behaviors tended to be more extreme in males, whereas the effects of Poly(I:C) following MIA tended to be more extreme in females. Our findings demonstrate that MIA and Poly(I:C) affected behaviors, and the viral mimetic effects shortly after injection can offer insights into the prolonged effect of postnatal viral infections on feeding, social interactions and health status. Management practices that reduce the likelihood of gestational diseases and accommodate for behavioral disruptions in the offspring can minimize the impact of MIA.

Lasting and Sex-Dependent Impact of Maternal Immune Activation on Molecular Pathways of the Amygdala

The prolonged and sex-dependent impact of maternal immune activation (MIA) during gestation on the molecular pathways of the amygdala, a brain region that influences social, emotional, and other behaviors, is only partially understood. To address this gap, we investigated the effects of viral-elicited MIA during gestation on the amygdala transcriptome of pigs, a species of high molecular and developmental homology to humans. Gene expression levels were measured using RNA-Seq on the amygdala for 3-week-old female and male offspring from MIA and control groups. Among the 403 genes that exhibited significant MIA effect, a prevalence of differentially expressed genes annotated to the neuroactive ligand-receptor pathway, glutamatergic functions, neuropeptide systems, and cilium morphogenesis were uncovered. Genes in these categories included corticotropin-releasing hormone receptor 2, glutamate metabotropic receptor 4, glycoprotein hormones, alpha polypeptide, parathyroid hormone 1 receptor, vasointestinal peptide receptor 2, neurotensin, proenkephalin, and gastrin-releasing peptide. These categories and genes have been associated with the MIA-related human neurodevelopmental disorders, including schizophrenia and autism spectrum disorders. Gene network reconstruction highlighted differential vulnerability to MIA effects between sexes. Our results advance the understanding necessary for the development of multifactorial therapies targeting immune modulation and neurochemical dysfunction that can ameliorate the effects of MIA on offspring behavior later in life.

PSVI-29 Maternal immune activation alters inflammatory cytokine profiles in response to weaning

Maternal immune activation (MIA) during gestation can alter immune responses of offspring to many stressors including weaning. Interleukin (IL)-10 and IL-6 are anti- and pro-inflammatory cytokines, respectively, released during the immune response. This study assessed the effects of MIA on piglets’ serum cytokine concentrations in response to weaning. Camborough gilts were inseminated at approximately 235 days of age and were inoculated intranasally on gestational day 76 with porcine reproductive and respiratory syndrome virus (PRRSV) (n = 11) or saline (n = 7). On postnatal day (PD) 21 approximately half of the piglets remained with sows (suckled) while the rest were weaned. Blood was collected from piglets prior to weaning on PD21 and at PD22. Serum concentrations of IL-6 and IL-10 were measured by ELISA. Cytokine concentrations were tested for fixed effects of gilt treatment (PRRSV or Control), piglet sex (female or male), management (suckled or weaned), sampling day (PD21 or PD22), interactions, and Normality assumptions. IL-10 presented a significant interaction between sex, gilt treatment, and management at PD22 (P &lt; 0.05). Weaned males from PRRSV-treated gilts had higher IL-10 concentrations versus suckled males whereas females from PRRSV-treated gilts had comparable levels of IL-10 between management groups. Overall, IL-10 was higher in piglets from PRRSV-treated gilts relative to Control gilts and matching sex and management groups. Higher IL-6 concentrations were found in weaned males from PRRSV-treated gilts versus suckled males at PD22. This pattern between management groups was reversed in females from PRRSV-treated gilts. Among piglets from Control gilts, males possessed higher IL-6 concentrations versus females across management groups. These results suggest MIA can alter inflammatory cytokine concentrations differently between males and females in response to weaning. This altered response may reduce offspring resiliency to subsequent immune or management stressors. This study is supported by USDA NIFA AFRI, 2018-67015-27413.

PSVI-38 Impact of PRRSV infection during gestation on the protein levels in the blood of piglets

Costs and productivity losses associated with porcine reproductive and respiratory syndrome virus (PRRSV) outbreaks impact the swine industry. The objective of this study was to evaluate the effect of maternal immune activation (MIA) from a PRRSV challenge during gestation on the piglet serum concentrations of albumin and globulin, indicators of inflammation or organ damage. Eighteen pregnant Camborough gilts were inoculated with either PRRSV or saline on gestational day 76. After farrowing 106 piglets remained with the gilts until postnatal day (PD) 21. One group of piglets was weaned and group-housed while another group remained with the gilts until PD22. At PD 60, a group of weaned piglets was fasted for one day while the rest was fed to meet nutritional requirements. Serum concentrations of globulin and albumin were measured on PD 22 and 61 and were analyzed using a linear mixed model including the fixed effects of gilt challenge, piglet treatment and sex and the random effect of gilt. On PD 22, albumin was higher in weaned relative to suckled piglets from saline-treated gilts (P &lt; 0.0305). Globulin was higher in weaned relative to suckled piglets (P &lt; 0.0014) and in piglets from PRRSV-treated relative to saline-treated gilts (P &lt; 0.0201). The albumin/globulin ratio was higher in weaned piglets from saline relative to PRRSV-treated gilts (P &lt; 0.0367). On PD 61, albumin was higher in fasted relative to fed piglets (P &lt; 0.0072). Globulin was higher in males relative to females from PRRSV-treated gilts (P &lt; 0.0326), and the albumin/globulin ratio was higher in fasted relative to fed piglets (P &lt; 0.0043). Our results indicate a positive correlation between serum protein concentrations and MIA, weaning or fasting stress that may be indicative of inflammation, organ dysfunction or nutritional imbalance. This study is supported by USDA NIFA AFRI, grant number 2018-67015-27413.

PSIII-9 Effect of maternal immune activation during gestation on piglets’ cortisol response to stress

Maternal immune activation (MIA) during gestation can affect the ability of the offspring to cope with stress such as weaning. Cortisol, a glucocorticoid released in response to stress, is an established indicator of stress. The purpose of this study was to evaluate the cortisol response to weaning stress of offspring exposed to MIA during gestation. Camborough gilts were inseminated at approximately 235 days of age. On gestational day 76, gilts (n = 11) were inoculated with porcine reproductive and respiratory syndrome virus (PRRSV) intranasally whereas saline was intranasally administered to Control gilts (n = 7). On postnatal day (PD) 21 approximately half of the male and female piglets remained with sows (suckled) while the rest were weaned. Blood was collected from the piglets prior to weaning on PD21 and at PD22. ELISA was used to measure cortisol in the serum. The analysis of cortisol concentration tested for the fixed effects of gilt treatment (PRRSV or Control), piglet sex (female or male), management (suckled or weaned), day of sampling (PD21 or PD22), interactions, and for Normality assumptions. At PD22 female weaned piglets had a higher level of cortisol when compared to female suckled piglets in both Control (P &lt; 0.05) and PRRSV (P &lt; 0.05). Males exhibited a similar trend that did not reach significance. Cortisol concentrations were lower in male piglets from Control relative to PRRSV-treated gilts and the differences were more pronounced among the suckled group. The results suggest that MIA elevates basal serum cortisol in unstressed males. This study is supported by USDA NIFA AFRI, 2018-67015-27413.