Negative Immunomodulatory Effects of Type 2 Porcine Reproductive and Respiratory Syndrome Virus-Induced Interleukin-1 Receptor Antagonist on Porcine Innate and Adaptive Immune Functions

Impaired innate and adaptive immune responses are evidenced throughout the course of PRRSV infection. We previously reported that interleukin-1 receptor antagonist (IL-1Ra) was involved in PRRSV-induced immunosuppression during an early phase of infection. However, the exact mechanism associated with PRRSV-induced IL-1Ra immunomodulation remains unknown. To explore the immunomodulatory properties of PRRSV-induced IL-1Ra on porcine immune functions, monocyte-derived dendritic cells (MoDC) and leukocytes were cultured with type 2 PRRSV, and the immunological role of IL-1Ra was assessed by addition of anti-porcine IL-1Ra Ab. The results demonstrated that PRRSV-induced IL-1Ra reduced phagocytosis, surface expression of MHC II (SLA-DR) and CD86, as well as downregulation of IFNA and IL1 gene expression in the MoDC culture system. Interestingly, IL-1Ra secreted by the PRRSV-infected MoDC also inhibited T lymphocyte differentiation and proliferation, but not IFN-γ production. Although PRRSV-induced IL-1Ra was not directly linked to IL-10 production, it contributed to the differentiation of regulatory T lymphocytes (Treg) within the culture system. Taken together, our results demonstrated that PRRSV-induced IL-1Ra downregulates innate immune functions, T lymphocyte differentiation and proliferation, and influences collectively with IL-10 in the Treg induction. The immunomodulatory roles of IL-1Ra elucidated in this study increase our understanding of the immunobiology of PRRSV

Comparative analysis of complete nucleotide sequence of porcine reproductive and respiratory syndrome virus (PRRSV) isolates in Thailand (US and EU genotypes)

<p>Abstract</p> <p>Background</p> <p>Porcine reproductive and respiratory syndrome virus (PRRSV) is a causative agent of Porcine Reproductive and Respiratory Syndrome (PRRS). In this study, the complete nucleotide sequences of the selected two Thai PRRSV isolates, EU (01CB1) and US (01NP1) genotypes were determined since both isolates are the Thai prototypes.</p> <p>Results</p> <p>01CB1 and 01NP1 contain 14,943 and 15,412 nucleotides, respectively. The viruses compose 2 untranslated regions (5' UTR and 3' UTR) and 8 open reading frames (ORFs) designated as ORF1a, ORF1b and ORF2-7. Phylogenetic analysis of full length of the viruses also showed that the 01CB1 and 01NP1 were grouped into the EU and US genotype, respectively. In order to determine the genetic variation and genetic relatedness among PRRSV isolates, the complete nucleotide sequences of PRRSV isolated in Thailand, 01CB1 and 01NP1 were compared with those of 2 EU strains (Lelystad, and EuroPRRSV), 6 US strains (MLV, VR2332, PA8, 16244B, SP and HUN4). Our results showed that the 01CB1 genome shares approximately 99.2% (Lelystad) and 95.2% (EuroPRRSV) nucleotide identity with EU field strains. While, the 01NP1 genome has 99.9% nucleotide identity with a live vaccine strain (MLV) and 99.5% and 98.5% nucleotide identity with 2 other US isolates, VR2332 and 16244B, respectively. In addition, ORF5 nucleotide sequences of 9 PRRS viruses recovered in Thailand during 2002-2008 were also included in this study. Phylogenetic analysis of ORF5 showed high similarity among EU and US genotypes of the recent Thai PRRS viruses (2007-2008 viruses) with 01CB1 and 01NP1.</p> <p>Conclusion</p> <p>Overall, the results suggested that the Thai EU isolate (01CB1) may evolve from the EU prototype, Lelystad virus, whereas the Thai US isolate (01NP1) may originate and evolve from the vaccine virus or its derivatives. Interestingly, the US-MLV vaccine was not available in the Thai market in 2001. The Vaccine-like virus might have persisted in the imported pigs or semen and later spread in the Thai swine industry. This report is the first report of complete nucleotide sequences of the Thai PRRS viruses both EU and US genotypes.</p

Influenza Virus (H5N1) in Live Bird Markets and Food Markets, Thailand

A surveillance program for influenza A viruses (H5N1) was conducted in live bird and food markets in central Thailand during July 2006–August 2007. Twelve subtype H5N1 viruses were isolated. The subtype H5N1 viruses circulating in the markets were genetically related to those that circulated in Thailand during 2004–2005

Pandemic (H1N1) 2009 Virus on Commercial Swine Farm, Thailand

A swine influenza outbreak occurred on a commercial pig farm in Thailand. Outbreak investigation indicated that pigs were co-infected with pandemic (H1N1) 2009 virus and seasonal influenza (H1N1) viruses. No evidence of gene reassortment or pig-to-human transmission of pandemic (H1N1) 2009 virus was found during the outbreak

Genetic characterization of 2008 reassortant influenza A virus (H5N1), Thailand

In January and November 2008, outbreaks of avian influenza have been reported in 4 provinces of Thailand. Eight Influenza A H5N1 viruses were recovered from these 2008 AI outbreaks and comprehensively characterized and analyzed for nucleotide identity, genetic relatedness, virulence determinants, and possible sites of reassortment. The results show that the 2008 H5N1 viruses displayed genetic drift characteristics (less than 3% genetic differences), as commonly found in influenza A viruses. Based on phylogenetic analysis, clade 1 viruses in Thailand were divided into 3 distinct branches (subclades 1, 1.1 and 1.2). Six out of 8 H5N1 isolates have been identified as reassorted H5N1 viruses, while other isolates belong to an original H5N1 clade. These viruses have undergone inter-lineage reassortment between subclades 1.1 and 1.2 and thus represent new reassorted 2008 H5N1 viruses. The reassorted viruses have acquired gene segments from H5N1, subclade 1.1 (PA, HA, NP and M) and subclade 1.2 (PB2, PB1, NA and NS) in Thailand. Bootscan analysis of concatenated whole genome sequences of the 2008 H5N1 viruses supported the reassortment sites between subclade 1.1 and 1.2 viruses. Based on estimating of the time of the most recent common ancestors of the 2008 H5N1 viruses, the potential point of genetic reassortment of the viruses could be traced back to 2006. Genetic analysis of the 2008 H5N1 viruses has shown that most virulence determinants in all 8 genes of the viruses have remained unchanged. In summary, two predominant H5N1 lineages were circulating in 2008. The original CUK2-like lineage mainly circulated in central Thailand and the reassorted lineage (subclades 1.1 and 1.2) predominantly circulated in lower-north Thailand. To prevent new reassortment, emphasis should be put on prevention of H5N1 viruses circulating in high risk areas. In addition, surveillance and whole genome sequencing of H5N1 viruses should be routinely performed for monitoring the genetic drift of the virus and new reassorted strains, especially in light of potential reassortment between avian and mammalian H5N1 viruses

Characterization of immune responses induced by plasmids encoding bovine rotavirus antigens in the Murine model

DNA immunization effectively induces humoral and cell-mediated immunity to numerous infectious diseases. To investigate the potential use of DNA-based vaccine for induction of bovine rotavirus (BRV) specific immune responses, I characterized the immune responses induced by plasmids encoding 2 important neutralizing antigens, VP4 and VP7, in a murine model. Immunization with plasmids encoding VP4 protein did not induced detectable BRV-specific antibody responses in mice. However, it induced BRV-specific cell-mediated immune responses characterized by an increased number of BRV-specific cytokine secreting cells in the spleens of immunized mice. In addition, the immunized animals were primed for both antibody and cellular immune responses following BRV boost. However, plasmids encoding VP4 did not boost the BRV-specific immune responses in the BRV-primed mice. The BRV-VP7 is also considered an important antigen for inducing protective immunity against rotaviruses. However, this study indicated that the VP7, either by itself or in the context of viral particle, was poorly immunogenic in mice. This project then explored several approaches to enhance the immunogenicity of the VP7 protein when expressed by the plasmid. These approaches included: (i) enhancing the level of gene expression by modifying the expression cassette of the plasmids; (ii) changing the cellular localization of the plasmid-expressed protein; (iii) co-administration of plasmids encoding VP4 and VP7; (iv) creating plasmids encoding a deletion mutant of VP7; and (v) construction of plasmids encoding chimeric proteins of VP7 and complement C3d or bovine herpes virus-1 glycoprotein D (BHV-1 gD). The results from these studies demonstrated that cellular localization and nature of the VP7 antigen could greatly influence the immunogenicity of the plasmid-expressed antigen and the pattern of immune responses in immunized mice. Plasmids encoding membrane-bound VP7 induced the best BRV-specific immune responses, following BRV boost or in BRV-primed mice, when compared with the authentic and the secretory versions. In addition, the plasmid encoding a deletion mutant VP7, induced predominantly BVR-specific IL-4 production. Strategies that had previously been shown to enhance the immunogenicity of protein antigens were also examined. However, different outcomes were observed when these strategies were applied to plasmid immunization. First, addition of the C3d gene into the expression cassette which encoded antigen-C3d chimeras inhibited the induction of both humoral and cell-mediated, antigen-specific immune responses. Secondly, co-expression of the gD molecule as a gD-VP7 chimera enhanced the level of BRV-specific antibody responses following viral boost or in the BRV-primed mice. These results with the gD protein suggested an alternative approach for improving the immunogenicity of poorly immunogenic antigens. None of the plasmids used in this study induced BRV-specific antibody responses following a primary immunization. However, immunological activity was evident following BRV administration, either prior to or following plasmid immunization. Each plasmid induced a distinct pattern of immune responses in both naive and BRV-primed mice. These investigations demonstrated specific ways that DNA immunization could be modified to modulate the outcome of BRV-specific immune responses. (Abstract shortened by UMI.