Comparison of influenza A virus infection in high‐ and low‐birth‐weight pigs using morphometric analysis

Abstract

BackgroundEpigenetic studies have shown that low‐birth‐weight (LBW) and growth restriction has been associated with reduced immune function in humans and reduced passive immunity in pigs. To examine the immune responses of high‐birth‐weight (HBW) and LBW groups of pigs, influenza A virus infection was used as an exemplifier of neonatal respiratory disease.ObjectivesThe objectives of this study were (i) to compare clinical, immunological, and pathological outcome of influenza infection in HBW to LBW pigs and (ii) to establish standardized sampling sites, score each site independently with set criteria, and compare scores between sites.MethodsSixty‐eight 4‐week‐old pigs originating from either HBW or LBW litters were intratracheally inoculated with 106·3 TCID 50/ml of A/swine/Texas/4199‐2/1998 H3N2 and euthanized 48 hours later. Samples were collected 2·5 cm from the tip of both cranial and middle lung lobes. The formalin‐fixed paraffin‐embedded tissue sections were scored in a blinded manner by a single pathologist using established scoring criteria for routine and immunohistochemical stains. Clinical parameters, lung and nasal swab virus titers, and cytokine levels for interferon‐alpha and interleukin‐1‐beta, IL‐6, and IL‐8 were measured.Results and ConclusionsLung lesion severity and influenza staining intensity were significantly lower in LBW compared with HBW pigs (P < 0·05). Additionally, examining just the LBW group, the significant difference between lobes (P = 0·009) showed that the mean score for the right cranial lung lobe was higher compared with the other three lobes.

Birth Weight, Intrauterine Growth Retardation and Fetal Susceptibility to Porcine Reproductive and Respiratory Syndrome Virus

“…In a recent study, clinical signs, immune responses and pathologic lesions were compared between low and high BW piglets experimentally infected with influenza virus (A/swine/Texas/4199-2/98 H3N2). Although no significant differences could be detected in clinical signs, viral shedding or cytokine production, high BW piglets showed more severe lung lesions, which was contrary to the authors' overarching hypothesis that the severity of disease is greater in low BW animals [33] . Although in the present study high and low BW gilts did not differ in terms of clinical signs, viral load, cytokine responses and fetal outcome (percent dead per litter), high BW gilts did demonstrate a more severe drop in absolute numbers of γδ T cells after experimental infection with PRRSv.…”

Transcriptomic and Epigenetic Profiling of the Lung of Influenza-Infected Pigs: A Comparison of Different Birth Weight and Susceptibility Groups

“…Detailed phenotypic results were published previously [ 15 ], but pertinent details are presented herein to help visualize group differences in influenza severity. The birth weight of HBW and LBW groups were 1.61 ±0.07 kg and 1.29 ±0.17 kg respectively ( P <0.05), and corresponded to Z-scores of 1.0 and -1.9 respectively ( P <0.05).…”

“…A detailed description of the animal experiment from which lung tissue was obtained for the present study has been published previously [ 15 ]. Briefly, 17 high birth weight (HBW) and 17 low birth weight (LBW) litters from first and second parity dams were identified at birth based on the average weight of all live and stillborn piglets in the litter being ≥ 0.7 SD or ≤ -0.7 SD, respectively (Z-scores), from the farm’s historical mean litter birth weight for a given litter size and parity.…”

“…The main objective of this study was to use transcriptomic and epigenetic approaches to compare the responses in lung tissue following an influenza A virus challenge to piglets originating from either ‘high’ or ‘low’ birth weight litters. Phenotypic differences in the response to infection between these high and low birth weight pigs have previously been described [ 15 ]. The epigenetic modification of gene promoters, with its subsequent effect on transcription, is thought to be the molecular basis for initiating and maintaining programming effects, but very few studies have actually investigated programming effects at the molecular level.…”

Unravelling the genetic components involved in the immune response of pigs vaccinated against influenza virus

“…Detmer and colleagues (Detmer et al, 2013) have compared the effect of influenza infection in a group of piglets with high and low birth weight, and no statistical difference was observed between groups in total viral load and severity of lung lesions. In our study, the effect of body weight on the immune response to vaccination was also tested.…”