Association of humoral response to classical swine fever vaccination with single nucleotide polymorphisms of swine leukocyte antigens

Elucidation of novel SNPs affecting immune response to classical swine fever vaccination in pigs using immunogenomics approach

The host genetic makeup plays a significant role in causing the within-breed variation among individuals after vaccination. The present study was undertaken to elucidate the genetic basis of differential immune response between high and low responder Landlly (Landrace X Ghurrah) piglets vis-à-vis CSF vaccination. For the purpose, E2 antibody response against CSF vaccination was estimated in sampled animals on the day of vaccination and 21-day post-vaccination as a measure of humoral immune response. Double-digestion restriction associated DNA (ddRAD) sequencing was undertaken on 96 randomly chosen Landlly piglets using Illumina HiSeq platform. SNP markers were called using standard methodology. Genome-wide association study (GWAS) was undertaken in PLINK program to identify the informative SNP markers significantly associated with differential immune response. The results revealed significant SNPs associated with E2 antibody response against CSF vaccination. The genome-wide informative SNPs for the humoral immune response against CSF vaccination were located on SSC10, SSC17, SSC9, SSC2, SSC3 and SSC6. The overlapping and flanking genes (500Kb upstream and downstream) of significant SNPs were CYB5R1, PCMTD2, WT1, IL9R, CD101, TMEM64, TLR6, PIGG, ADIPOR1, PRSS37, EIF3M, and DNAJC24. Functional enrichment and annotation analysis were undertaken for these genes in order to gain maximum insights into the association of these genes with immune system functionality in pigs. The genetic makeup was associated with differential immune response against CSF vaccination in Landlly piglets while the identified informative SNPs may be used as suitable markers for determining variation in host immune response against CSF vaccination in pigs.

Genome-wide transcriptome profiling of CSF virus challenged monocyte-derived macrophages provides distinct insights into immune response of Landrace and indigenous Ghurrah pigs

The present study was undertaken to characterize the distinct immune response in indigenous Ghurrah and exotic Landrace pigs by challenging monocyte-derived macrophages (MDMs) with CSF virus under in-vitro conditions and assessing the variations in the transcriptome profile at 48 h post-infection (hpi). RNA-sequencing was carried out in infected and non-infected MDMs of Ghurrah (n = 3) and Landrace (n = 3) piglets prior- as well as post-stimulation. MDMs of Ghurrah showed greater immune regulation in response to CSF infection with 518 significantly differentially expressed genes (DEG) in infected versus non-infected MDMs, as compared to only 31 DEGs in Landrace MDMs. In Landrace, the principal regulators of inflammation (IL1α, IL1β and TNF) were upregulated in infected cells while in Ghurrah, these were downregulated. Overall, macrophages from indigenous Ghurrah showed more immunological dysregulation in response to virulent CSF virus infection as compared to the exotic Landrace pigs.

Characterisation and comparison of immune response mechanisms in an indigenous and a commercial pig breed after classical swine fever vaccination

The live attenuated classical swine fever (CSF) vaccine has been successfully used to prevent and control CSF outbreaks for 6 decades. However, the immune response mechanisms against the vaccine remain poorly understood. Moreover, very few reports exist regarding the breed differences in the response to CSF vaccine. In this study, we generated the peripheral blood mononuclear cell transcriptomes of indigenous Ghurrah and commercial Landrace pig breeds, before and 7 days after CSF vaccination. Subsequently, between and within-breed differential gene expression analyses were carried out. Results revealed large differences in pre-vaccination peripheral blood mononuclear cell transcriptome profiles of the two breeds, which were homogenised 7 days after vaccination. Before vaccination, gene set enrichment analysis showed that pathways related to antigen sensing and innate immune response were enriched in Ghurrah, while pathways related to adaptive immunity were enriched in Landrace. Ghurrah exhibited greater immunomodulation compared to Landrace following the vaccination. In Ghurrah, cell-cycle processes and T-cell response pathways were upregulated after vaccination. However, no pathways were upregulated in Landrace after vaccination. Pathways related to inflammation were downregulated in both the breeds after vaccination. Key regulators of inflammation such as IL1A, IL1B, NFKBIA and TNF genes were strongly downregulated in both the breeds after vaccination. Overall, our results have elucidated the mechanisms of host immune response against CSF vaccination in two distinct breeds and revealed common key genes instrumental in the global immune response to the vaccine.

A 1.6 Mb region on SSC2 is associated with antibody response to classical swine fever vaccination in a mixed pig population

Classical Swine Fever (CSF) is a contagious viral disease of pigs which is endemic in several parts of the world, including India. Prophylactic vaccination using live attenuated vaccine is the preferred method of control. However, there is significant inter-individual variation in the antibody response to vaccination. In this study, we measured the E2 antibody blocking percentage after 21 days of CSF vaccination in a mixed pig population consisting of Landrace, indigenous Ghurrah pigs, and their crossbreds. A Genome Wide Association Study (GWAS) carried out using single-SNP and haplotype based methods detected a 1.6 Mb region on SSC2 (28.92-30.52 Mb) as significantly associated with antibody response to CSF vaccination. The significant region and 1 Mb flanking sequences encompass 3 genes - EIF3M, DNAJC24 and ARL14EP, which code for proteins involved in Pestivirus replication and host immune response system. Our results combined with previous studies on immune response of pigs present this region as a suitable candidate for future functional investigations.

Selection and validation of differentially expressed metabolic and immune genes in weaned Ghurrah versus crossbred piglets

In the present investigation, differentially expressed genes (DEGs) were studied using RNA sequencing (RNA-seq) technique in porcine peripheral blood mononuclear cells (PBMC) of weaned Ghurrah and crossbred piglets at 3-month age. Transcriptomic analysis was done using three different packages, namely, EBSeq, DESeq2, and edgeR, to identify the DEGs between Ghurrah and crossbred piglets. Total 7717 DEGs were commonly identified by all three packages, out of which 4151 genes found to be up-regulated, and 3566 genes were down-regulated. Functional annotation of these DEGs indicated metabolism as the most commonly enriched category followed by the immune response. Genes related to metabolism and growth were up-regulated in crossbred piglets as compared with Ghurrah piglets, whereas immunity-related genes were up-regulated in Ghurrah piglets elucidating the disease resistance nature of this indigenous breed over crossbred counterparts. Further, eight DEGs, namely, LRP-1, ADCY4, ERRFI1, LDHD, ARG1, OASL, MGARP, and S100A8, were validated by qRT-PCR in a separate set of biological samples and found to be in concordance with RNA-seq results. Finding in the present study provides insight into genes and their molecular mechanisms governing difference in growth performance between Ghurrah and crossbred pigs.

Signature of genome wide gene expression in classical swine fever virus infected macrophages and PBMCs of indigenous vis-a-vis crossbred pigs

The genetic basis of differential host immune response vis-à-vis transcriptome profile was explored in PBMCs of indigenous (Ghurrah) and crossbred pigs after classical swine fever vaccination and in monocyte derived macrophages (MDMs) challenged with virulent classical swine fever (CSF) virus. The humoral immune response (E2 antibody) was higher (74.87%) in crossbred than indigenous pigs (58.20%) at 21st days post vaccination (21dpv). The rate of reduction of ratio of CD4⁺/CD8⁺ was higher in crossbred pigs than indigenous pigs at 7th days post vaccination (7dpv). The immune genes IFIT1, IFIT5, RELA, NFKB2, TNF and LAT2 were up regulated at 7dpv in RNA seq data set and was in concordance during qRT-PCR validation. The Laminin Subunit Beta 1 (LAMB1) was significantly (p ≤ 0.05) down-regulated in MDMs of indigenous pigs and consequently a significantly (p ≤ 0.01) higher copy number of virulent CSF virus was evidenced in macrophages of crossbred pigs than indigenous pigs. Activation of LXR:RXR pathway at 60 h post infection (60hpi) in MDMs of indigenous versus crossbred pigs inhibited nuclear translocation of NF-κB, resulted into transrepression of proinflammatory genes. But it helped in maintenance of HDL level by lowering down cholesterol/LDL level in MDMs of indigenous pigs. The key immune genes (TLR2, TLR4, IL10, IL8, CD86, CD54, CASP1) of TREM1 signaling pathway were upregulated at 7dpv in PBMCs but those genes were downregulated at 60hpi in MDMs indigenous pigs. Using qRT-PCR, the validation of differentially expressed, immunologically important genes (LAMB1, OAS1, TLR 4, TLR8 and CD86) in MDMs revealed that expression of these genes were in concordance with RNA-seq data.

Genome-wide integrated analysis of miRNA and mRNA expression profiles to identify differentially expressed miR-22-5p and miR-27b-5p in response to classical swine fever vaccine virus

The present study was conducted to identify the differentially expressed miRNAs (DE miRNAs) in the peripheral blood mononuclear cells of crossbred pigs in response to CSF vaccination on 7 and 21 days of post vaccination as compared to unvaccinated control (0 dpv). Simultaneously, set of miRNA was predicted using mRNA seq data at same time point. The proportion of CD4^-CD8⁺ and CD4⁺CD8⁺ increased after vaccination, and the mean percentage inhibition was 86.89% at 21 dpv. It was observed that 22 miRNAs were commonly expressed on both the time points. Out of predicted DE miRNAs, it was found that 40 and 35 DE miRNAs were common, obtained from miRNA seq analysis and predicted using mRNA seq data on 7 dpv versus 0 dpv and 21 dpv versus 0 dpv respectively. Two DE miRNAs, ssc-miR-22-5p and ssc-miR-27b-5p, were selected based on their log₂ fold change and functions of their target genes in immune process/pathway of viral infections. The validations of DE miRNAs using qRT-PCR were in concordance with miRNA seq analysis. Two set of target genes, CD40 and SWAP70 (target gene of ssc-miR-22-5p) and TLR4 and Lyn (target gene of ssc-miR-27b-5p), were validated and were in concordance with results of RNA seq analysis at a particular time point (except TLR4). The first report of genome-wide identification of differentially expressed miRNA in response to live attenuated vaccine virus of classical swine fever revealed miR-22-5p and miR-27b-5p were differentially expressed at 7 dpv and 21 dpv.

Exploration of genetic basis of differential immune response to CSF vaccination in desi (indigenous) piglets using RNA-Seq approach

In the present study, the transcriptome profiling of peripheral blood mononuclear cells (PBMCs) of indigenous piglets against classical swine fever (CSF) vaccination was performed for elucidating the genetic basis of their differential humoral immunity. Piglets were vaccinated with lapinised strain of CSF virus (CSFV) followed by measurement of humoral immune response using c-ELISA at 28th day post vaccination (28dpv). The RNA sequencing data was analysed using established pipeline to determine set of differentially expressed genes (DEGs) in high responder as compared to low responder piglet. The differentially expressed important immune molecules were involved in regulating important pathways including antigen processing and presentation, T cell receptor signalling, B cell development, activation and signaling genes. The genes with differential expression also included TLR 3, 6, 7, 8, 9, and antiviral molecules such as MX, and ISG (Interferon stimulated genes) family members. The proteinprotein interaction of the immune genes was extracted for network representation. Most of the immune genes involved showed upregulation except the genes for antigen processing and presentation and T cell receptor signaling that were downregulated in the high responder. The immunologically important genes namely IFIT1, IFIT5, TAPBP, and TLR7 were validated using qRT-PCT and were observed to be in concordance with the RNA Seq results.

Expression profiling of immune genes in classical swine fever vaccinated indigenous and crossbred piglets

Classical swine fever is a highly contagious disease of pigs which courses from life-threatening to asymptomatic, depending on the virulence of the virus strain and the immune-competence of the host. The present study was undertaken to investigate the expression of immunologically important genes, viz. IFNα, IFNβ, SLA, SLA-2, SLA-DR, Ii, SLA-DM, CSK and JUN and to ascertain genetic group differences on the basis of humoral immune response. Blood samples were collected from 5 indigenous and 6 crossbred piglets at pre-vaccination and after 28th day of classical swine fever (CSF) vaccination. On 28th day, the competitive Enzyme Linked Immunosorbent Assay (cELISA) revealed poor humoral immune response (E2 antibodies) in indigenous piglets (84.80%) as compared to crossbred piglets (98.33%) in response to CSF vaccination. The expression level of genes was analyzed in three ways, viz. indigenous 28th day post-vaccination (28dpv) versus pre-vaccination, crossbred 28th day post-vaccination versus pre-vaccination and crossbred 28th day post-vaccination versus indigenous 28th day post-vaccination. The study showed that IFNα, IFNβ, SLA, SLA-2, Ii, SLA-DM, CSK and JUN were significantly upregulated in crossbred piglets than indigenous piglets at 28th day post-vaccination. But the SLA-DR was significantly downregulated in CSF vaccinated crossbred over indigenous piglets.