PRRSV-1 induced lung lesion is associated with an imbalance between costimulatory and coinhibitory immune checkpoints

Pig jejunal single-cell RNA landscapes revealing breed-specific immunology differentiation at various domestication stages

Background

Domestication of wild boars into local and intensive pig breeds has driven adaptive genomic changes, resulting in significant phenotypic differences in intestinal immune function. The intestine relies on diverse immune cells, but their evolutionary changes during domestication remain poorly understood at single-cell resolution.

Methods

We performed single-cell RNA sequencing (scRNA-seq) and marker gene analysis on jejunal tissues from wild boars, a Chinese local breed (Jinhua), and an intensive breed (Duroc). Then, we developed an immune cell evaluation system that includes immune scoring, gene identification, and cell communication analysis. Additionally, we mapped domestication-related clustering relationships, highlighting changes in gene expression and immune function.

Results

We generated a single-cell atlas of jejunal tissues, analyzing 26,246 cells and identifying 11 distinct cell lineages, including epithelial and plasma cells, and discovered shared and unique patterns in intestinal nutrition and immunity across breeds. Immune cell evaluation analysis confirmed the conservation and heterogeneity of immune cells, manifested by highly conserved functions of immune cell subgroups, but wild boars possess stronger immune capabilities than domesticated breeds. We also discovered four patterns of domestication-related breed-specific genes related to metabolism, immune surveillance, and cytotoxic functions. Lastly, we identified a unique population of plasma cells with distinctive antibody production in Jinhua pig population.

Conclusions

Our findings provide valuable single-cell insights into the cellular heterogeneity and immune function evolution in the jejunum during pig at various domestication stages. The single-cell atlas also serves as a resource for comparative studies and supports breeding programs aimed at enhancing immune traits in pigs.

Evaluation of the cross-protective effect of VR2332 modified live virus vaccine against a recombinant NADC34-like porcine reproductive and respiratory syndrome virus

In recent years, NADC34-like strains of porcine reproductive and respiratory syndrome virus have gradually emerged as mainstream strains on Chinese pig farms. These strains have high mutation rates and can recombine with local strains, representing great challenges to prevention and control efforts. Previously, a new recombinant NADC34-like subtype strain was isolated in our laboratory. Herein, we evaluated the cross-protective effect of the VR2332 modified live virus (MLV) against the novel NADC34-like recombinant strain using the immune challenge protection test in piglets and sows. The results revealed that immunization with the vaccine in piglets significantly reduced viremia, lung damage and stimulated the production of PRRSV-N antibodies. In the sow challenge experiment, one abortion and one death were recorded in the positive control group, and the survival rate of offspring was only 25%. However, there were no sow deaths or abortions in the immunization group during the experiment, and the average piglet survival rate was high at 76.5%. In general, the VR2332 MLV confers a certain extent of cross-protection against the NADC34-like recombinant strain, providing an effective reference and guidance for prevention and control efforts and clinical vaccine use.

Comparison of pathogenicity and host responses of emerging porcine reproductive and respiratory syndrome virus variants in piglets

Porcine reproductive and respiratory syndrome virus (PRRSV) is a highly variable virus with genetic diversity. This study comparatively examines the pathogenicity and immunological impact of two emergent PRRSV strains, SD53 and HuN4, in piglets. Our results indicate that SD53 strain induces milder clinical syndromes and less severe tissue damage than HuN4, despite similar replication rates. Hematological tests showed less perturbations in peripheral blood cell profiles after SD53 infection, suggesting a less systemic impact. The neutrophil-to-lymphocyte ratio was notably lower in SD53-infected piglets, suggesting a less intense inflammatory reaction. Moreover, SD53 infection led to lower levels of pro-inflammatory cytokines, further supporting a less pronounced inflammatory profile. Both strains induced the production of PRRSV-specific antibodies. However, transcriptomic analysis of lung and lymph node tissues from infected piglets disclosed a more moderate up-regulation of core genes, including ISGs, in the SD53 group. Further analysis indicated that SD53 primarily enhanced immune-related signaling, particularly in T cell response modules, while HuN4 caused a more robust pro-inflammatory reaction and a dampening of T cell functionality. Flow cytometry analyses confirmed these findings, showing higher CD4/CD8 ratios and increased CD4+ T cell percentages in SD53-infected piglets, implying a more robust T cell response. Collectively, these findings broaden our comprehension of PRRSV pathogenesis and may inform the development of future therapeutic or prophylactic strategies for controlling PRRSV infections more effectively.

IMPORTANCE

The high mutation rate of porcine reproductive and respiratory syndrome virus (PRRSV) poses significant challenges to its accurate diagnosis and the implementation of effective control measures. This research explores the pathogenic profiles of two emerging PRRSV stains: the NADC30-like strain SD53 and the highly pathogenic strain HuN4. Our investigation reveals that SD53 initiates distinct immunopathological responses in vivo compared with those provoked by HuN4. By conducting a transcriptome analysis of differential gene expression in the lungs and lymph nodes of infected piglets, we unveil the intricate molecular mechanisms underlying the contrasting pathogenicity of these two strains. The comprehensive insights yielded by this study are instrumental in advancing our understanding of the dominant NADC30-like PRRSV strain, which has become increasingly prevalent in China's swine industry.

Infectious Agents Associated with Abortion Outbreaks in Italian Pig Farms from 2011 to 2021

The present study retrospectively analyzed the infectious agents associated with 829 abortion outbreaks occurring from 2011 to 2021 in northern Italy. Foetuses were subjected to necropsies, and organ samples were analyzed by direct PCR to screen for six swine pathogens. In 42.0% of the examined outbreaks, at least one infectious agent was found. Porcine reproductive and respiratory syndrome virus (PRRSV) (24.9%) and porcine circovirus-2 (PCV2) (11.5%) were the most frequently detected among the known abortion-inducing pathogens. Chlamydia spp. (5.6%), porcine parvovirus (PPV) (4.0%), and Leptospira spp. (2.6%) were less common. Although its role in swine reproductive disorders is still unclear, PCV3 was detected in 19.6% of the cases. Coinfections were detected in 25.0% of positive outbreaks, and the most frequent coinfection was represented by PRRSV and PCV2 (32.2%), followed by PRRSV and PCV3 (23%). PCV2 prevalence showed a slight but consistent reduction during the study period, while PCV3 increased in frequency. Our data suggest an overall reduction in abortion outbreaks during the study period. PRRSV was confirmed as the main abortion agent detected in the examined area, while PCV2 prevalence showed a decline. Conversely, PCV3 detection has been increasing, supporting its potential role as an abortion agent. Our results highlight the importance of implementing a consistent and standardized sampling procedure, as well as a thorough diagnostic protocol, to reduce the incidence of inconclusive diagnoses.

Monoclonal Antibody against Porcine LAG3 Inhibits Porcine Reproductive and Respiratory Syndrome Virus Infection

Lymphocyte activation gene 3 (LAG3) is an inhibitory receptor and the interaction between fibrinogen-like protein 1 and LAG3 can inhibit the anti-tumor effect of T cells both in vivo and in vitro, which was regarded as a new immune evasion mechanism. Porcine reproductive and respiratory syndrome (PRRS), caused by PRRSV, is an infectious disease characterized by reproductive disorders in pregnant sows and gilts and respiratory problems in pigs of all ages, seriously impacting the pig industry worldwide. In this study, monoclonal antibodies (mAbs) against porcine LAG3 (pLAG3) were developed, and one mAb (1C2) showed good reactivity with pLAG3 on PHA-activated porcine peripheral blood lymphocytes. Epitope mapping showed the epitope recognized by mAb 1C2 was located at amino acid residues 214-435 of pLAG3. LAG3 expression in the tissues of PRRSV-infected pigs was detected, using mAb 1C2 as the primary antibody, and the results revealed that PRRSV infection caused a marked increase in LAG3 expression compared to the control group. Interference of LAG3 expression on PHA-activated lymphocytes promoted PRRSV replication in the co-culture system of monocyte-derived dendritic cells and lymphocytes, whereas overexpression of LAG3 or blocking of the LAG3 signal with mAb 1C2 inhibited PRRSV replication, indicating that PRRSV infection activates the LAG3-signaling pathway, suggesting that this pathway plays an important role in PRRSV pathogenesis. The results obtained lay the foundation for subsequent research on the role of LAG3 in PRRS and other diseases with persistent infection characteristics.

The scene of lung pathology during PRRSV-1 infection

Porcine reproductive and respiratory syndrome (PRRS) is one of the most economically important infectious diseases for the pig industry worldwide. The disease was firstly reported in 1987 and became endemic in many countries. Since then, outbreaks caused by strains of high virulence have been reported several times in Asia, America and Europe. Interstitial pneumonia, microscopically characterised by thickened alveolar septa, is the hallmark lesion of PRRS. However, suppurative bronchopneumonia and proliferative and necrotising pneumonia are also observed, particularly when a virulent strain is involved. This raises the question of whether the infection by certain strains results in an overstimulation of the proinflammatory response and whether there is some degree of correlation between the strain involved and a particular pattern of lung injury. Thus, it is of interest to know how the inflammatory response is modulated in these cases due to the interplay between virus and host factors. This review provides an overview of the macroscopic, microscopic, and molecular pathology of PRRSV-1 strains in the lung, emphasising the differences between strains of different virulence.

Pathogenicity Studies of NADC34-like Porcine Reproductive and Respiratory Syndrome Virus LNSY-GY and NADC30-like Porcine Reproductive and Respiratory Syndrome Virus GXGG-8011 in Piglets

The porcine reproductive and respiratory syndrome virus (PRRSV) has caused significant economic losses to the swine industry. The U.S., China, and Peru have reported NADC30-like or NADC34-like PRRSV-infected piglets, which have been identified as the cause of a significant number of abortions in clinics. Although the pathogenicity of NADC30-like PRRSV and NADC34-like PRRSV in piglets exhibits significant variability globally, studies on their pathogenicity in China are limited. In this study, the animal experiments showed that within 8-14 days post-infection, both piglets infected with NADC30-like PRRSV GXGG-8011 and those infected with NADC34-like PRRSV LNSY-GY exhibited significant weight loss compared to the control piglets. Additionally, the viremia of the LNSY-GY persisted for 28 days, while the viremia of piglets infected with the GXGG-8011 lasted for 17 days. Similarly, the duration of viral shedding through the fecal-oral route after the LNSY-GY infection was longer than that observed after the GXGG-8011 infection. Furthermore, post-infection, both the LNSY-GY and GXGG-8011 led to pronounced histopathological lesions in the lungs of piglets, including interstitial pneumonia and notable viral colonization. However, the antibody production in the LNSY-GY-infected group occurred earlier than that in the GXGG-8011-infected group. Our research findings indicate that LNSY-GY is a mildly pathogenic strain in piglets, whereas we speculate that the GXGG-8011 might be a highly pathogenic strain.

The DC-T cell axis is an effective target for the treatment of non-small cell lung cancer

The dendritic cell (DC)-T cell axis is a bridge that connects innate and adaptive immunities. The initial immune response against tumors is mainly induced by mature antigen-presenting DCs. Enhancing the crosstalk between DCs and T cells may be an effective approach to improve the immune response to non-small cell lung cancer (NSCLC). In this article, a review was made of the interaction between DCs and T cells in the treatment of NSCLC and how this interaction affects the treatment outcome.

Integrative transcriptomic profiling of mRNA, miRNA, circRNA, and lncRNA in alveolar macrophages isolated from PRRSV-infected porcine

Introduction

The porcine reproductive and respiratory syndrome virus (PRRSV) continues to pose a significant threat to the global swine industry, attributed largely to its immunosuppressive properties and the chronic nature of its infection. The absence of effective vaccines and therapeutics amplifies the urgency to deepen our comprehension of PRRSV's intricate pathogenic mechanisms. Previous transcriptomic studies, although informative, are partially constrained by their predominant reliance on in vitro models or lack of long-term infections. Moreover, the role of circular RNAs (circRNAs) during PRRSV invasion is yet to be elucidated.

Methods

In this study, we employed an in vivo approach, exposing piglets to a PRRSV challenge over varied durations of 3, 7, or 21 days. Subsequently, porcine alveolar macrophages were isolated for a comprehensive transcriptomic investigation, examining the expression patterns of mRNAs, miRNAs, circRNAs, and long non-coding RNAs (lncRNAs).

Results

Differentially expressed RNAs from all four categories were identified, underscoring the dynamic interplay among these RNA species during PRRSV infection. Functional enrichment analyses indicate that these differentially expressed RNAs, as well as their target genes, play a pivotal role in immune related pathways. For the first time, we integrated circRNAs into the lncRNA-miRNA-mRNA relationship, constructing a competitive endogenous RNA (ceRNA) network. Our findings highlight the immune-related genes, CTLA4 and SAMHD1, as well as their associated miRNAs, lncRNAs, and circRNAs, suggesting potential therapeutic targets for PRRS. Importantly, we corroborated the expression patterns of selected RNAs through RT-qPCR, ensuring consistency with our transcriptomic sequencing data.

Discussion

This study sheds lights on the intricate RNA interplay during PRRSV infection and provides a solid foundation for future therapeutic strategizing.