Intradermal Inoculation of Inactivated Foot-and-Mouth Disease Vaccine Induced Effective Immune Responses Comparable to Conventional Intramuscular Injection in Pigs

All pigs in the Republic of Korea are given the foot-and-mouth disease virus (FMDV) vaccine intramuscularly (IM) as part of the country's vaccination policy. However, the IM administration of the FMDV vaccine to pig results in residual vaccine components in the muscle and undesirable changes in muscle and soft tissues, causing economic losses in swine production. In this study, we evaluated whether intradermal (ID) vaccination could be proposed as an alternative to IM administration. ID vaccination (0.2 mL on each side of the neck muscle) and IM vaccination (2 mL on each side of the neck muscle) were performed twice, separated by 14 days, using a commercial FMD vaccine in specific-pathogen-free pigs. We observed growth performance, gross and microscopic lesions at the inoculation site, FMDV-specific antibodies, and neutralizing antibodies for 35 days after vaccination. Side effects on the skin grossly appeared following ID administration, but most were reduced within two weeks. All ID-vaccinated pigs showed inflammatory lesions limited to the dermis, but IM-vaccinated pigs had abnormal undesirable changes and pus in the muscle. ID-vaccinated pigs performed comparably to IM-vaccinated pigs in terms of growth, FMD virus-specific antibodies, protection capability against FMDV, and T-cell induction. This study demonstrated that the ID inoculation of the inactivated FMD vaccine induced immune responses comparable to an IM injection at 1/10 of the inoculation dose and that the inoculation lesion was limited to the dermis, effectively protecting against the formation of abnormal undesirable changes in muscle and soft tissues.

Creating resistance to avian influenza infection through genome editing of the ANP32 gene family

Chickens genetically resistant to avian influenza could prevent future outbreaks. In chickens, influenza A virus (IAV) relies on host protein ANP32A. Here we use CRISPR/Cas9 to generate homozygous gene edited (GE) chickens containing two ANP32A amino acid substitutions that prevent viral polymerase interaction. After IAV challenge, 9/10 edited chickens remain uninfected. Challenge with a higher dose, however, led to breakthrough infections. Breakthrough IAV virus contained IAV polymerase gene mutations that conferred adaptation to the edited chicken ANP32A. Unexpectedly, this virus also replicated in chicken embryos edited to remove the entire ANP32A gene and instead co-opted alternative ANP32 protein family members, chicken ANP32B and ANP32E. Additional genome editing for removal of ANP32B and ANP32E eliminated all viral growth in chicken cells. Our data illustrate a first proof of concept step to generate IAV-resistant chickens and show that multiple genetic modifications will be required to curtail viral escape.

CD4+TGFβ+ cells infiltrated the bursa of Fabricius following IBDV infection, and correlated with a delayed viral clearance, but did not correlate with disease severity, or immunosuppression

Introduction

Infectious Bursal Disease Virus (IBDV) causes immunosuppression in chickens. While B-cell destruction is the main cause of humoral immunosuppression, bursal T cells from IBDV-infected birds have been reported to inhibit the mitogenic response of splenocytes, indicating that some T cell subsets in the infected bursa have immunomodulatory activities. CD4+CD25+TGFβ+ cells have been recently described in chickens that have immunoregulatory properties and play a role in the pathogenesis of Marek's Disease Virus.

Methods

To evaluate if CD4+CD25+TGFβ+ cells infiltrated the bursa of Fabricius (BF) following IBDV infection, and influenced the outcome of infection, birds were inoculated at either 2 days or 2 weeks of age with vaccine strain (228E), classic field strain (F52/70), or PBS (mock), and bursal cell populations were quantified by flow cytometry.

Results

Both 228E and F52/70 led to atrophy of the BF, a significant reduction of Bu1+-B cells, and a significant increase in CD4+ and CD8α+ T cells in the BF, but only F52/70 caused suppression of immune responses to a test antigen in younger birds, and clinical signs in older birds. Virus was cleared from the BF more rapidly in younger birds than older birds. An infiltration of CD4+CD25+T cells into the BF, and elevated expression of bursal TGFβ-1+ mRNA was observed at all time points following infection, irrespective of the strain or age of the birds, but CD4+TGFβ+cells and CD4+CD25+TGFβ+ cells only appeared in the BF at 28 dpi in younger birds. In older birds, CD4+TGFβ+ cells and CD4+CD25+TGFβ+ cells were present at earlier time points, from 7dpi following 228E infection, and from 14 and 28 dpi following F52/70 infection, respectively.

Discussion

Our data suggest that an earlier infiltration of CD4+TGFβ+ cells into the BF correlated with a delayed clearance of virus. However, the influx of CD4+TGFβ+ cells and CD4+CD25+TGFβ+ into the BF did not correlate with increased pathogenicity, or immunosuppression.

Genetic diversity, recombination and cross-species transmission of a waterbird gammacoronavirus in the wild

Viruses emerging from wildlife can cause outbreaks in humans and domesticated animals. Predicting the emergence of future pathogens and mitigating their impacts requires an understanding of what shapes virus diversity and dynamics in wildlife reservoirs. In order to better understand coronavirus ecology in wild species, we sampled birds within a coastal freshwater lagoon habitat across 5 years, focussing on a large population of mute swans (Cygnus olor) and the diverse species that they interact with. We discovered and characterised the full genome of a divergent gammacoronavirus belonging to the Goose coronavirus CB17 species. We investigated the genetic diversity and dynamics of this gammacoronavirus using untargeted metagenomic sequencing of 223 faecal samples from swans of known age and sex, and RT-PCR screening of 1632 additional bird samples. The virus circulated persistently within the bird community; virus prevalence in mute swans exhibited seasonal variations, but did not change with swan age-class or epidemiological year. One whole genome was fully characterised, and revealed that the virus originated from a recombination event involving an undescribed gammacoronavirus species. Multiple lineages of this gammacoronavirus co-circulated within our study population. Viruses from this species have recently been detected in aquatic birds from both the Anatidae and Rallidae families, implying that host species habitat sharing may be important in shaping virus host range. As the host range of the Goose coronavirus CB17 species is not limited to geese, we propose that this species name should be updated to 'Waterbird gammacoronavirus 1'. Non-invasive sampling of bird coronaviruses may provide a tractable model system for understanding the evolutionary and cross-species dynamics of coronaviruses.

A standardized method to study immune responses using porcine whole blood

BACKGROUND

Peripheral blood mononuclear cells (PBMCs) are commonly used to assess in vitro immune responses. However, PBMC isolation is a time-consuming procedure, introduces technical variability, and requires a relatively large volume of blood. By contrast, whole blood assay (WBA) is faster, cheaper, maintains more physiological conditions, and requires less sample volume, laboratory training, and equipment.

OBJECTIVES

Herein, this study aimed to develop a porcine WBA for in vitro evaluation of immune responses.

METHODS

Heparinized whole blood (WB) was diluted (non-diluted, 1/2, 1/8, and 1/16) in RPMI-1640 media, followed by phorbol myristate acetate and ionomycin. After 24 h, cells were stained for interferon (IFN)-γ secreting T-cells followed by flow cytometry, and the supernatant was analyzed for tumor necrosis factor (TNF)-α. In addition, diluted WB was stimulated by lipopolysaccharide (LPS) and polyinosinic:polycytidylic acid (poly I:C), reference strain KCTC3557 (RS), field isolate (FI), of heat-killed (HK) Streptococcus suis, and porcine reproductive and respiratory syndrome virus (PRRSV).

RESULTS

The frequency of IFN-γ⁺CD3⁺ T-cells and concentration of TNF-α in the supernatant of WB increased with increasing dilution factor and were optimal at 1/8. WB TNF-α and interleukin (IL)-10 cytokine levels increased significantly following stimulation with LPS or poly I:C. Further, FI and RS induced IL-10 production in WB. Additionally, PRRSV strains increased the frequency of IFN-γ⁺CD4^-CD8⁺ cells, and IFN-γ was non-significantly induced in the supernatant of re-stimulated samples.

CONCLUSIONS

We propose that the WBA is a rapid, reliable, and simple method to evaluate immune responses and WB should be diluted to trigger immune cells.

An Infectious Bursal Disease Virus (IBDV) Reverse Genetics Rescue System and Neutralization Assay in Chicken B Cells

Infectious bursal disease virus (IBDV) is a major threat to the productivity of the poultry industry due to morbidity, mortality, and immunosuppression that exacerbates secondary infections and reduces the efficacy of vaccination programs. Field strains of IBDV have a preferred tropism for chicken B cells, the majority of which reside in the bursa of Fabricius (BF). IBDV adaptation to adherent cell culture is associated with mutations altering amino acids in the hypervariable region (HVR) of the capsid protein, which affects immunogenicity and virulence. Until recently, this has limited both the application of reverse genetics systems for engineering molecular clones, and the use of in vitro neutralization assays, to cell-culture-adapted strains of IBDV. Here, we describe the rescue of molecular clones of IBDV containing the HVR from diverse field strains, along with a neutralization assay to quantify antibody responses against the rescued viruses, both using chicken B cells. These methods are readily adaptable to any laboratory with molecular biology expertise and negate the need to obtain wild-type strains. © 2023 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: A chicken B-cell rescue system for IBDV Basic Protocol 2: A chicken B-cell neutralization assay for IBDV.

Modeling Infectious Bursal Disease Virus (IBDV) Antigenic Drift In Vitro

Infectious bursal disease virus (IBDV) vaccines do not induce sterilizing immunity, and vaccinated birds can become infected with field strains. Vaccine-induced immune selection pressure drives the evolution of antigenic drift variants that accumulate amino acid changes in the hypervariable region (HVR) of the VP2 capsid, which may lead to vaccine failures. However, there is a lack of information regarding how quickly mutations arise, and the relative contribution different residues make to immune escape. To model IBDV antigenic drift in vitro, we serially passaged a classical field strain belonging to genogroup A1 (F52/70) ten times, in triplicate, in the immortalized chicken B cell line, DT40, in the presence of sub-neutralizing concentrations of sera from birds inoculated with IBDV vaccine strain 2512, to generate escape mutants. This assay simulated a situation where classical strains may infect birds that have suboptimal vaccine-induced antibody responses. We then sequenced the HVR of the VP2 capsid at passage (P) 5 and 10 and compared the sequences to the parental virus (P0), and to the virus passaged in the presence of negative control chicken serum that lacked IBDV antibodies. Two escape mutants at P10 had the same mutations, D279Y and G281R, and a third had mutations S251I and D279N. Furthermore, at P5, the D279Y mutation was detectable, but the G281R mutation was not, indicating the mutations arose with different kinetics.

Comparison of the pathogenicity of porcine reproductive and respiratory syndrome virus (PRRSV)-1 and PRRSV-2 in pregnant sows

To date, few studies related to the evaluation of the pathogenicity of different PRRSV isolates using a reproductive model have been undertaken, and the main focus has remained on respiratory models using young pigs. This study aimed to evaluate the pathogenicity of two PRRSV-1 isolates (D40 and CBNU0495) and two PRRSV-2 isolates (K07-2273 and K08-1054) in a reproductive model. Pregnant sows were experimentally infected with PRRSV at gestational day 93 or used as an uninfected negative control. Sera were collected at 0, 3, 7, 14, and 19 days post-challenge (dpc) for virological and serological assays. At 19 dpc, all sows were euthanized, and their fetuses were recovered by performing cesarean section and immediately euthanized for sample collection. Here, compared to the other isolates, the CBNU0495 isolate replicated most efficiently in the pregnant sows, and K07-2273 produced the highest rate of reproductive failure even though it did not replicate as efficiently as the other isolates in sows and fetuses, indicating that vertical transmission and reproductive failure due to PRRSV infection do not have any significant correlation with the viral loads in samples from sows and fetuses. Similarly, the viral loads and the histopathological lesions did not show any correlation with each other, as the PRRSV-2-infected groups displayed more prominent and frequent histopathological lesions with lower viral loads than the PRRSV-1-infected groups. However, viral loads in the myometrium/endometrium might be related to the spreading of PRRSV in the fetuses, which affected the birth weight of live fetuses. This study contributes to a better understanding of the pathogenicity of the most prevalent Korean PRRSVs in a reproductive model.

Evaluation of the Cross-Protective Efficacy of a Chimeric PRRSV Vaccine against Two Genetically Diverse PRRSV2 Field Strains in a Reproductive Model

Despite the routine use of porcine reproductive and respiratory syndrome (PRRS)-modified live vaccines, serious concerns are currently being raised due to their quick reversion to virulence and limited cross-protection against divergent PRRS virus (PRRSV) strains circulating in the field. Therefore, a PRRS chimeric vaccine (JB1) was produced using a DNA-launched infectious clone by replacing open reading frames (ORFs) 3–6 with those from a mixture of two genetically different PRRSV2 strains (K07–2273 and K08–1054) and ORF1a with that from a mutation-resistant PRRSV strain (RVRp22) exhibiting an attenuated phenotype. To evaluate the safety and cross-protective efficacy of JB1 in a reproductive model, eight PRRS-negative pregnant sows were purchased and divided into four groups. Four sows in two of the groups were vaccinated with JB1, and the other 4 sows were untreated at gestational day 60. At gestational day 93, one vaccinated group and one nonvaccinated group each were challenged with either K07–2273 or K08–1054. All of the sows aborted or delivered until gestation day 115 (24 days post challenge), and the newborn piglets were observed up to the 28th day after birth, which was the end of the experiment. Overall, pregnant sows of the JB1-vaccinated groups showed no meaningful viremia after vaccination and significant reductions in viremia with K07–2273 and K08–1054, exhibiting significantly higher levels of serum virus-neutralizing antibodies than non-vaccinated sows. Moreover, the JB1-vaccinated groups did not exhibit any abortion due to vaccination and showed improved piglet viability and birth weight. The piglets from JB1-vaccinated sows displayed lower viral concentrations in serum and fewer lung lesions compared with those of the piglets from the nonvaccinated sows. Therefore, JB1 is a safe and effective vaccine candidate that confers simultaneous protection against two genetically different PRRSV strains.

Protective immunity induced by concurrent intradermal injection of porcine circovirus type 2 and Mycoplasma hyopneumoniae inactivated vaccines in pigs

Vaccines against porcine circovirus type 2 (PCV2) and Mycoplasma hyopneumoniae (Mhp) are routinely used by intramuscular injection. However, since intramuscular vaccination causes stress and increases the risk of cross-contamination among pigs, research on intradermal vaccination is currently being actively conducted. This study was designed to evaluate the efficacy of intradermally administered inactivated vaccines against PCV2 and Mhp in pigs. Three-week-old specific pathogen-free pigs were divided into three groups (5 pigs per group). Pigs in the two groups were intradermally vaccinated with the PCV2 or Mhp vaccine using a needle-free injector. Pigs in the third group were kept as nonvaccinated controls. At 21 days post-vaccination, pigs in one of these vaccinated groups and the nonvaccinated group were intranasally challenged with PCV2b and Mhp, while the other vaccinated group pigs were maintained as vaccine controls. Vaccine efficacy was evaluated by observing weight gain, pathogen load, pathological changes, and humoral or cellular immune responses. As a result, vaccinated pigs revealed significantly higher body weight gain, with lower clinical scores. Vaccinated pigs also showed higher antibody responses but lower PCV2b or Mhp loads in sera, nasal swabs, or lungs than nonvaccinated pigs. Intriguingly, vaccinated pigs upregulated cytotoxic T cells (CTLs), helper T type 1 cells (Th1 cells), and helper T type 17 cells (Th17 cells) after immunization and showed significantly higher levels of CTLs, Th1 and Th17 cells at 14 days post-challenge than nonvaccinated and challenged pigs. This study demonstrated that protective immune responses against PCV2 and Mhp could be efficiently induced in pigs using a relatively small volume of intradermal vaccines, probably due to effective antigen delivery to antigen-presenting cells in the dermis.

Transcriptomic Analysis of Inbred Chicken Lines Reveals Infectious Bursal Disease Severity Is Associated with Greater Bursal Inflammation In Vivo and More Rapid Induction of Pro-Inflammatory Responses in Primary Bursal Cells Stimulated Ex Vivo

In order to better understand differences in the outcome of infectious bursal disease virus (IBDV) infection, we inoculated a very virulent (vv) strain into White Leghorn chickens of inbred line W that was previously reported to experience over 24% flock mortality, and three inbred lines (15I, C.B4 and 0) that were previously reported to display no mortality. Within each experimental group, some individuals experienced more severe disease than others but line 15I birds experienced milder disease based on average clinical scores, percentage of birds with gross pathology, average bursal lesion scores and average peak bursal virus titre. RNA-Seq analysis revealed that more severe disease in line W was associated with significant up-regulation of pathways involved in inflammation, cytoskeletal regulation by Rho GTPases, nicotinic acetylcholine receptor signaling, and Wnt signaling in the bursa compared to line 15I. Primary bursal cell populations isolated from uninfected line W birds contained a significantly greater percentage of KUL01+ macrophages than cells isolated from line 15I birds (p < 0.01) and, when stimulated ex vivo with LPS, showed more rapid up-regulation of pro-inflammatory gene expression than those from line 15I birds. We hypothesize that a more rapid induction of pro-inflammatory cytokine responses in bursal cells following IBDV infection leads to more severe disease in line W birds than in line 15I.

Evaluation of a multiplex PCR method for the detection of porcine parvovirus types 1 through 7 using various field samples

Porcine parvoviruses (PPVs) are small, nonenveloped DNA viruses that are widespread in the global pig population. PPV type 1 (PPV1) is a major causative agent of reproductive failure and has been recognized since the 1960s. In recent decades, novel PPVs have been identified and designated as PPVs 2 through 7 (PPV2~PPV7). Although the epidemiological impacts of these newly recognized parvoviruses on pigs are largely unknown, continuous surveillance of these PPVs is needed. The aim of this study was to develop an improved and efficient detection tool for these PPVs and to assess the developed method with field samples. Using 7 sets of newly designed primers, a multiplex polymerase chain reaction (mPCR) protocol was developed for the simultaneous detection of the seven genotypes of PPV (PPV1~PPV7). The sensitivity of the mPCR assay was analyzed, and the detection limit was determined to be 3×10³ viral copies. The assay was highly specific in detecting one or more of the viruses in various combinations in specimens. The mPCR method was evaluated with 80 serum samples, 40 lung or lymph node samples and 40 intestine or fecal samples. When applied to these samples, the mPCR method could detect the 7 viruses simultaneously, providing rapid results regarding infection and coinfection status. In conclusion, the developed mPCR assay can be utilized as an effective and accurate diagnostic tool for rapid differential detection and epidemiological surveillance of various PPVs in numerous types of field samples.

Evaluation of local and systemic immune responses in pigs experimentally challenged with porcine reproductive and respiratory syndrome virus

The host-associated defence system responsible for the clearance of porcine reproductive and respiratory syndrome virus (PRRSV) from infected pigs is currently poorly understood. To better understand the dynamics of host–pathogen interactions, seventy-five of 100 pigs infected with PRRSV-JA142 and 25 control pigs were euthanized at 3, 10, 21, 28 and 35 days post-challenge (dpc). Blood, lung, bronchoalveolar lavage (BAL) and bronchial lymph node (BLN) samples were collected to evaluate the cellular immune responses. The humoral responses were evaluated by measuring the levels of anti-PRRSV IgG and serum virus-neutralizing (SVN) antibodies. Consequently, the highest viral loads in the sera and lungs of the infected pigs were detected between 3 and 10 dpc, and these resulted in moderate to mild interstitial pneumonia, which resolved accompanied by the clearance of most of the virus by 28 dpc. At peak viremia, the frequencies of alveolar macrophages in infected pigs were significantly decreased, whereas the monocyte-derived DC/macrophage and conventional DC frequencies were increased, and these effects coincided with the early induction of local T-cell responses and the presence of proinflammatory cytokines/chemokines in the lungs, BAL, and BLN as early as 10 dpc. Conversely, the systemic T-cell responses measured in the peripheral blood mononuclear cells were delayed and significantly induced only after the peak viremic stage between 3 and 10 dpc. Taken together, our results suggest that activation of immune responses in the lung could be the key elements for restraining PRRSV through the early induction of T-cell responses at the sites of virus replication.

Characterization of Clostridium novyi isolated from a sow in a sudden death case in Korea

Background

Multifocal spherical nonstaining cavities and gram-positive, rod-shaped, and endospore-forming bacteria were found in the liver of a sow that died suddenly. Clostridium novyi type B was identified and isolated from the sudden death case, and the isolate was characterized by molecular analyses and bioassays in the current study.

Results

C. novyi was isolated from the liver of a sow that died suddenly and was confirmed as C. novyi type B by differential PCR. The C. novyi isolate fermented glucose and maltose and demonstrated lecithinase activity, and the cell-free culture supernatant of the C. novyi isolate exhibited cytotoxicity toward Vero cells, demonstrating that the isolate produces toxins. In addition, whole-genome sequencing of the C. novyi isolate was performed, and the complete sequences of the chromosome (2.29 Mbp) and two plasmids (134 and 68 kbp) were identified for the first time. Based on genome annotation, 7 genes were identified as glycosyltransferases, which are known as alpha toxins; 23 genes were found to be related to sporulation; 12 genes were found to be related to germination; and 20 genes were found to be related to chemotaxis.

Conclusion

C. novyi type B was isolated from a sow in a sudden death case and confirmed by biochemical and molecular characterization. Various virulence-associated genes were identified for the first time based on whole-genome sequencing.

Effect of polymorphisms in porcine guanylate-binding proteins on host resistance to PRRSV infection in experimentally challenged pigs

Guanylate-binding proteins (GBP1 and GBP5) are known to be important for host resistance against porcine reproductive and respiratory syndrome virus (PRRSV) infection. In this study, the effects of polymorphisms in GBP1 (GBP1E2 and WUR) and GBP5 on host immune responses against PRRSV were investigated to elucidate the mechanisms governing increased resistance to this disease. Seventy-one pigs [pre-genotyped based on three SNP markers (GBP1E2, WUR, and GBP5)] were assigned to homozygous (n = 36) and heterozygous (n = 35) groups and challenged with the JA142 PRRSV strain. Another group of nineteen pigs was kept separately as a negative control group. Serum and peripheral blood mononuclear cells (PBMCs) were collected at 0, 3, 7, 14, 21 and 28 days post-challenge (dpc). Viremia and weight gain were measured in all pigs at each time point, and a flow cytometry analysis of PBMCs was performed to evaluate T cell activation. In addition, 15 pigs (5 pigs per homozygous, heterozygous and negative groups) were sacrificed at 3, 14 and 28 dpc, and the local T cell responses were evaluated in the lungs, bronchoalveolar lavage cells (BALc), lymph nodes and tonsils. The heterozygous pigs showed lower viral loads in the serum and lungs and higher weight gains than the homozygous pigs based on the area under the curve calculation. Consistently, compared with the homozygous pigs, the heterozygous pigs exhibited significantly higher levels of IFN-α in the serum, proliferation of various T cells (γδT, Th1, and Th17) in PBMCs and tissues, and cytotoxic T cells in the lungs and BALc. These results indicate that the higher resistance in the pigs heterozygous for the GBP1E2, WUR and GBP5 markers could be mediated by increased antiviral cytokine (IFN-α) production and T cell activation.

In vitro immune responses of porcine alveolar macrophages reflect host immune responses against porcine reproductive and respiratory syndrome viruses

BACKGROUND

Currently, an in vitro immunogenicity screening system for the immunological assessment of potential porcine reproductive and respiratory syndrome virus (PRRSV) vaccine candidates is highly desired. Thus, in the present study, two genetically divergent PRRSVs were characterized in vitro and in vivo to identify an in vitro system and immunological markers that predict the host immune response. Porcine alveolar macrophages (PAMs) and peripheral blood mononuclear cells (PBMCs) collected from PRRSV-negative pigs were used for in vitro immunological evaluation, and the response of these cells to VR2332c or JA142c were compared with those elicited in pigs challenged with the same viruses.

RESULTS

Compared with VR2332c or mock infection, JA142c induced increased levels of type I interferons and pro-inflammatory cytokines (TNF-α, IL-1α/β, IL-6, IL-8, and IL-12) in PAMs, and these elevated levels were comparable to the cytokine induction observed in PRRSV-challenged pigs. Furthermore, significantly greater numbers of activated CD4⁺ T cells, type I helper T cells, cytotoxic T cells and total IFN-γ⁺ cells were observed in JA142c-challenged pigs than in VR2332c- or mock-challenged pigs.

CONCLUSIONS

Based on these results, the innate immune response patterns (particularly IFN-α, TNF-α and IL-12) to specific PRRSV strains in PAMs might reflect those elicited by the same viruses in pigs.

The prevalence and genetic characteristics of porcine circovirus type 2 and 3 in Korea

BACKGROUND

Porcine circovirus-associated diseases (PCVAD), caused by porcine circovirus type 2 (PCV2), threaten the pig industry worldwide. Five genotypes of PCV2 were recently identified: PCV2a, PCV2b, PCV2c, PCV2d and PCV2e. In addition, a novel porcine circovirus from a case of a sow with dermatitis, nephropathy syndrome and reproductive failure has been identified based on metagenomic analysis and classified as porcine circovirus type 3 (PCV3). Therefore, the current study was conducted to determine the prevalence and genetic characteristics of PCV2 and PCV3 in clinical samples.

RESULTS

A total of 471 samples (161 tissue samples of lungs and lymph nodes from 34 farms and 310 serum samples from 47 farms) were tested for PCV2. Among them, 171 samples from 59 farms that had been positive for PCV2 were genotyped. Another 690 samples (296 tissue samples of lungs and lymph nodes from 91 farms, 108 samples of aborted foetuses from 26 farms, and 286 serum samples from 47 farms) were tested for PCV3. Based on PCV2 genotyping results, PCV2d was the most prevalent genotype (107 of 171 samples), and co-infections with combinations of PCV2a, 2b and 2d were identified in 48 samples from 17 farms. A total of 14 samples from 11 farms were also positive for both PCV2 and PCV3. For PCV3, 57 samples (9.8%) from 32 farms (23.2%) were positive. Among the 108 aborted foetuses from 26 farms, only 2 samples were positive for PCV3. Based on sequence comparisons, PCV2d shares 89.6-91.0% and 93.2-94.3% homology with PCV2a and PCV2b, respectively; 98.6-100% homology is shared among PCV2d strains. The PCV3 strains identified in this study share 98.0-99.5% homology.

CONCLUSIONS

Our study concludes that PCV2d has become the most predominant genotype in Korea. PCV3 was also identified in clinical samples, though no significant association with clinical symptoms was observed in PCV3-positive cases.

Detection and phylogenetic analysis of Orf virus in Kashmir Himalayas

Orf virus (ORFV) is a zoonotic pathogen that primarily infects sheep and goats, and is responsible for significant economic losses. ORFV is endemic in all the major sheep and goat rearing areas of the world including Indian subcontinent. However, the nature of ORFV circulating among sheep and goat in Kashmir Himalayas has not yet been characterized. In the present study, we describe natural outbreaks of ORFV in sheep and goats of Kashmir Himalayas. We detected the presence of ORFV in the scab lesion by PCR amplification of the major envelope protein (B2L) gene. We sequenced the virus interferon resistance (VIR) gene and determined their phylogenetic relationship with that of the published reference sequences. Phylogenetic analysis based on VIR gene revealed that the ORFV isolates from Kashmir Himalayas separated into main two clusters. The sheep isolates showed genetic homology with the sheep strains reported from Greece and Italy, whereas the goat-specific strain show homology with the goat strains reported from China. This study demonstrates the presence of ORFV infection in sheep and goats, and report first phylogenetic analysis of the ORFV strains prevalent in the Kashmir Himalayas.

Plant synthetic GP4 and GP5 proteins from porcine reproductive and respiratory syndrome virus elicit immune responses in pigs

We demonstrated successful overexpression of porcine reproductive and respiratory syndrome virus (PRRSV)-derived GP4D and GP5D antigenic proteins in Arabidopsis. Pigs immunized with transgenic plants expressing GP4D and GP5D proteins generated both humoral and cellular immune responses to PRRSV. Porcine reproductive and respiratory syndrome virus (PRRSV) causes PRRS, the most economically significant disease affecting the swine industry worldwide. However, current commercial PRRSV vaccines (killed virus or modified live vaccines) show poor efficacy and safety due to concerns such as reversion of virus to wild type and lack of cross protection. To overcome these problems, plants are considered a promising alternative to conventional platforms and as a vehicle for large-scale production of recombinant proteins. Here, we demonstrate successful production of recombinant protein vaccine by expressing codon-optimized and transmembrane-deleted recombinant glycoproteins (GP4D and GP5D) from PRRSV in planta. We generated transgenic Arabidopsis plants expressing GP4D and GP5D proteins as candidate antigens. To examine immunogenicity, pigs were fed transgenic Arabidopsis leaves expressing the GP4D and GP5D antigens (three times at 2-week intervals) and then challenged with PRRSV at 6-week post-initial treatment. Immunized pigs showed significantly lower lung lesion scores and reduced viremia and viral loads in the lung than pigs fed Arabidopsis leaves expressing mYFP (control). Immunized pigs also had higher titers of PRRSV-specific antibodies and significantly higher levels of pro-inflammatory cytokines (TNF-α and IL-12). Furthermore, the numbers of IFN-γ⁺-producing cells were higher, and those of regulatory T cells were lower, in GP4D and GP5D immunized pigs than in control pigs. Thus, plant-derived GP4D and GP5D proteins provide an alternative platform for producing an effective subunit vaccine against PRRSV.

Isolation, molecular characterization and prevalence of Clostridium perfringens in sheep and goats of Kashmir Himalayas, India

Aim:

The study was conducted to report the occurrence of the Clostridium perfringens in sheep and goats of the Kashmir valley for the 1^st time and to characterize them molecularly with respect to toxin genes to determine the prevalence of the various toxinotypes.

Materials and Methods:

A total of 177 samples (152 from sheep and 25 from goats) collected from healthy, diarrheic animals, and morbid material of animals suspected to have died of enterotoxaemia were screened for C. perfringens toxinotypes. The presumptive positive isolates were confirmed using 16S rRNA gene-based polymerase chain reaction (PCR). All the confirmed isolates were screened for six toxin genes, namely; cpa, cpb, etx, cpi, cpb2, and cpe using a multiplex PCR.

Results:

The PCR amplification of 16S rRNA gene revealed that out of 177 samples collected, 125 (70.62%) were found positive for C. perfringens, of which 110 (72.36%) were from sheep and 15 (60%) were from goats. The highest prevalence of C. perfringens toxinotype D was observed in lambs (56.16%) and kids (46.16%) followed by 3.84% in adult sheep while it was absent in samples obtained from adult goats. The multiplex PCR revealed that 67 (60.90%) isolates from sheep and 8 (53.33%) isolates from goats belonged to toxinotype A, while 43 (39.09%) isolates from sheep and 7 (46.66%) isolates from goats were detected as toxinotype D. None of the isolates was found to be toxinotype B, C, or E. All the C. perfringens toxinotype A isolates from sheep were negative for both cpb2 and cpe genes, however, 27.90% toxinotype D isolates from sheep carried cpb2 gene, and 6.97% possessed cpe gene. In contrast, 12.50% C. perfringens toxinotype A isolates from goats harbored cpb2 and cpe genes while 14.28% isolates belonging to toxinotype D carried cpb2 and cpe genes, respectively.

Conclusion:

The high prevalence of C. perfringens was observed, even in day-old lambs. The toxinotypes A and D are prevalent in both sheep and goats. The severity of disease and mortality may be associated with the presence of minor toxins in both the detected toxinotypes.

Genotyping and phylogenetic analysis of infectious bronchitis virus isolated from broiler chickens in Kashmir

Infectious bronchitis virus (IBV) is responsible for significant economic losses to the poultry industry across the world. The enormous genetic diversity of IBV poses difficulty in diagnosing and controlling the virus. To understand the nature of IBV prevalent in the Kashmir Himalayas, we characterized two field strains, isolated from non-immunized broiler chickens, by sequence and phylogenetic analysis of S1 subunit of the spike glycoprotein. The analysis revealed both the isolates are identical to each other, with nucleotide and amino acid sequence identities of 99.4% and 98.4%, respectively. They exhibit variable sequence divergence in the S1 gene to that of the reference serotypes. Both are of “Massachusetts type” belonging to GI-1 lineage of the IBV génotype. The phylogenetic analysis revealed both of the isolates clustered into the same branch as that of many IBV strains recently reported from China and Iran. Likely, these regionally-related isolates represent revertant vaccine strains which may have been disseminated across the region by wild migratory birds. This study provides the first report of molecular evidence and phylogenetic characterization of the IBV from the Kashmir Himalayas and implicate the possible role of wild migratory birds in the spread of IBV in the region.

Phenotypic and genotypic characterization of methicillin-resistant Staphylococcus aureus from bovine mastitis

Aim:

This study was conducted to determine the occurrence of methicillin-sensitive and Staphylococcus aureus (MSSA) methicillin-resistant S. aureus (MRSA) from bovine mastitis and to characterize them with respect to antibiotic resistance gene mecA.

Materials and Methods:

A total of 160 mastitic milk samples were screened for the presence of S. aureus. The presumptive positive isolates were confirmed using nuc and 23S rRNA gene-based polymerase chain reaction. All the confirmed isolates were subjected to in vitro antibiogram using a number of antibiotics. Isolates which showed resistance against methicillin were characterized for the presence of mecA gene.

Results:

Out of the total 160 milk samples, 36 (22.5%) samples yielded S. aureus. The in vitro antibiogram revealed that 16.6% S. aureus isolates were resistant to all antibiotics screened for and 5.5% isolates were sensitive to all of them. Furthermore, the study found 94.4%, 83.3%, 77.7%, 66.6%, 50%, and 27.7% of S. aureus isolates resistant to penicillin, ampicillin, amoxicillin-sulbactam, enrofloxacin, ceftriaxone, and methicillin, respectively. Out of the 36 S. aureus isolates, only 6 (16.6%) isolates were confirmed as MRSA while rest were MSSA.

Conclusion:

The higher occurrence of S. aureus-mediated mastitis was concluded due to improper hygienic and poor farm management. The multiple drug resistance reveals the indiscriminate use of drugs and presence of methicillin resistance gene determinant is an alarming situation as such infections are difficult to treat.