Mapping of on-field soil nutrient variabilities as a guiding force for smart farming: a case study from FarmerZone sentinel-1 from three potato agroecological zones of India.

Mapping of soil nutrient parameters using experimental measurements and geostatistical approaches to assist site-specific fertiliser advisories is anticipated to play a significant role in Smart Agriculture. FarmerZone is a cloud service envisioned by the Department of Biotechnology, Government of India, to provide advisories to assist smallholder farmers in India in enhancing their overall farm production. As a part of the project, we evaluated the soil spatial variability of three potato agroecological zones in India and provided soil health cards along with field-specific fertiliser recommendations for potato cultivation to farmers. Specifically, 705 surface samples were collected from three representative potato-growing districts of Indian states (Meerut, UP; Jalandhar, Punjab and Lahaul and Spiti, HP) and analysed for soil parameters such as organic carbon, macronutrients (NPK), micronutrients (Zn, Fe, Mn, and Cu), pH, and EC. The soil parameters were integrated into a geodatabase and subjected to kriging interpolation to create spatial soil maps of the targeted potato agroecological zones through best-fit experimental semivariograms. The spatial distribution showed a deficiency of soil organic carbon in two studied zones and available nitrogen among all studied zones. The available phosphorus and potassium varied among the agroecological zones. The micronutrient levels were largely sufficient in all the zones except at a few specific sites where nutrient advisories are recommended to replenish. The general management strategies were recommended based on the nutrient status in the studied area. This study clearly supports the significance of site-specific soil analytics and interpolated spatial soil mapping over any targeted agroecological zones as a promising strategy to deliver reliable advisories of fertiliser recommendations for smart farming.

Genotypic variations for tuber nutrient content, dry matter and agronomic traits in tetraploid potato germplasm.

Nutrient deficiencies lead to various health issues and are common worldwide. Potato germplasm is a rich source of natural variations and genetic variability present in it can be exploited for developing nutrient-rich high-yielding potato varieties. In this study, variations in the yield, dry matter (DM) and mineral nutrients concentrations were evaluated in both peeled and unpeeled tubers of 243 highly diverse tetraploid potato accessions. These were raised under field conditions for two consecutive years. The germplasm studied has a wider range of variations in peeled tubers DM (13.71-27.80%), Fe (17.08-71.03 mg/kg), Zn (9.55-34.78 mg/kg), Cu (2.13-13.25 mg/kg), Mn (7.04-25.15), Ca (117.4-922.5 mg/kg), Mg (656.6-1510.6 mg/kg), S (1121.3-3765.8 mg/kg), K (1.20-3.09%), P (0.21-0.50%) and Mo (53.6-1164.0 ppb) concentrations compared to popular Indian potato varieties. Higher nutrient concentrations in whole tubers compared to tuber flesh suggest that these are present in high concentration in the tuber peripheral layers and peeling off the tubers results in the loss of nutrients. Highest loss due to peeling off the tubers was observed in Fe (35.63%) followed by Cu (22.80%), Mn (21.69%), Ca (21.27%), Mg (12.89%), K (12.75%), Zn (10.13%), and Mo (9.87%). The GCV and PCV for all the traits in peeled tubers ranged from 9.67 to 29.91%, and 13.84 to 43.32%, respectively. Several significant positive correlations were observed among the parameters and the first two principal components accounted for 39.37% of total variations. The results of this study will pave a way for the development of nutrient-rich high-yielding potato varieties. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-022-01197-1.

Potato biofortification: an effective way to fight global hidden hunger.

Hidden hunger is leading to extensive health problems in the developing world. Several strategies could be used to reduce the micronutrient deficiencies by increasing the dietary uptake of essential micronutrients. These include diet diversification, pharmaceutical supplementation, food fortification and crop biofortification. Among all, crop biofortification is the most sustainable and acceptable strategy to overcome the global issue of hidden hunger. Since most of the people suffering from micronutrient deficiencies, have monetary issues and are dependent on staple crops to fulfil their recommended daily requirements of various essential micronutrients. Therefore, increasing the micronutrient concentrations in cost effective staple crops seems to be an effective solution. Potato being the world's most consumed non-grain staple crop with enormous industrial demand appears to be an ideal candidate for biofortification. It can be grown in different climatic conditions, provide high yield, nutrition and dry matter in lesser time. In addition, huge potato germplasm have natural variations related to micronutrient concentrations, which can be utilized for its biofortification. This review discuss the current scenario of micronutrient malnutrition and various strategies that could be used to overcome it. The review also shed a light on the genetic variations present in potato germplasm and suggest effective ways to incorporate them into modern high yielding potato varieties.

Identification, management and pecuniary impact of major carbon footprint contributor in potato production system of north-west India.

Assessment of carbon footprint of a crop is an important component of sustainable crop production, as it helps in framing effectual and viable crop management strategies to minimize ecosystem tampering. Thus, in present investigation carbon footprint of potato production system in different agro-climatic zones viz. undulating plain zone, central plain zone and western plain zone of North-west India were estimated, and compared with the recommended practices of these zones. The carbon footprint was higher in undulating plain zone followed by central plain zone and western plain zone with values being 343, 296 and 220 kg CO2 eq./t tuber yield (TY), sequentially, whereas same were 198 kg CO2 eq./t tuber yield (TY) in case of recommended practices. The social cost of carbon (SCC), that represents economic damage from the CO2 emissions, was also estimated. The integrated net economic balance (net return from yield - SCC) was also better in case of recommended practices. The major sources of emission from potato production system were fertilizer (NPK) application (42 %), irrigation (20 %), seed (14 %), fertilizer production (13 %) and energy use (excluding Irrigation) (5 %). Top most in the list of carbon footprint contributors was fertilizer application which was due to imbalanced application of these, and for getting the clear picture of this imbalance as well as its impact, a new and exclusive index- Relative Imbalance Fertilization Index (RIFIcf) was developed and tested. Carbon footprints were also related to tuber yield and an empirical model was developed that can be used to predict tuber yield on the basis of carbon footprint of potato production system. An increase in tuber yield with increasing carbon footprint was noticed, which became somewhat static at higher emissions. The findings of this investigation provide a clear picture of quantitative GHG emissions due to imbalanced inputs that can be plummeted to some extent if already existing recommendations are followed.

Atmospheric deposition studies of heavy metals in Arctic by comparative analysis of lichens and cryoconite.

Lichens and cryoconite (rounded or granular, brownish-black debris occurring in holes on the glacier surface) from Ny-Ålesund were used for understanding the elemental deposition pattern in the area. Lichen samples collected from low-lying coastal region and cryoconite samples from high altitudinal glacier area were processed and analysed for elements such as aluminium (Al), arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), cesium (Cs), copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), lead (Pb), vanadium (V) and zinc (Zn) through inductively coupled plasma mass spectrometry. Results showed that heavy metals, Al and Fe, are present in high concentration in the cryoconite samples. Al was also present in high amounts in seven of the eight lichen samples studied. The general scheme of elements in the decreasing order of their concentrations for most of the cryoconite samples was Al > Fe > Mn > Zn > V > Pb > Cr > Ni > Cu > Co > As > Cs > Cd while that for the lichen samples was Al > Fe > Zn > Mn > Pb > Cu > Cs > Cr > Ni > V > Co > As > Cd. Similarity in trends in the two sample types confirms that the environment indeed contains these elements in that order of concentration which overtime got accumulated in the samples. Overall comparison showed most elements to be present in high concentrations in the cryoconite samples as compared to the lichen samples. Within the lichens, elemental accumulation data suggests that the low-lying site (L-2) from where Cladonia mediterranea sample was collected was the most polluted accumulating a number of elements at high concentrations. The probable reasons for such deposition patterns in the region could be natural (crustal contribution and sea salt spray) and anthropogenic (local and long-distance transmission of dust particles). In the future, this data can form a baseline for monitoring quantum of atmospheric heavy metal deposition in lichens and cryoconite of Svalbard, Arctic.

Enhanced Field-Based Detection of Potato Blight in Complex Backgrounds Using Deep Learning.

Rapid and automated identification of blight disease in potato will help farmers to apply timely remedies to protect their produce. Manual detection of blight disease can be cumbersome and may require trained experts. To overcome these issues, we present an automated system using the Mask Region-based convolutional neural network (Mask R-CNN) architecture, with residual network as the backbone network for detecting blight disease patches on potato leaves in field conditions. The approach uses transfer learning, which can generate good results even with small datasets. The model was trained on a dataset of 1423 images of potato leaves obtained from fields in different geographical locations and at different times of the day. The images were manually annotated to create over 6200 labeled patches covering diseased and healthy portions of the leaf. The Mask R-CNN model was able to correctly differentiate between the diseased patch on the potato leaf and the similar-looking background soil patches, which can confound the outcome of binary classification. To improve the detection performance, the original RGB dataset was then converted to HSL, HSV, LAB, XYZ, and YCrCb color spaces. A separate model was created for each color space and tested on 417 field-based test images. This yielded 81.4% mean average precision on the LAB model and 56.9% mean average recall on the HSL model, slightly outperforming the original RGB color space model. Manual analysis of the detection performance indicates an overall precision of 98% on leaf images in a field environment containing complex backgrounds.

Response of embryonic chicken lymphoid cells to infectious bursal disease virus.

We exposed chicken embryos at embryonation day 18 (ED18) to a classical virulent infectious bursal disease virus (IBDV; cIBDV) and an attenuated strain of IBDV (aIBDV) and examined the response of embryonic lymphoid cells to these viruses. Embryos responded much more vigorously to cIBDV than to aIBDV. Following cIBDV exposure, embryonic thymus and bursa showed cellular destruction, enhanced rate of apoptosis and presence of viral proteins detectable by immunohistochemistry. At ED21, thymocytes from cIBDV-exposed embryos were severely deficient (P<0.05) in responding to stimulation in vitro with mitogens containing mouse anti-chicken CD28 mAb, PMA and ionomycin. Because purified CD3(+) T cells were also refractory to the mitogens, the mitogenic inhibition of embryonic thymocytes was not attributed to the presence of non-T cell suppressors. Cell suspensions prepared from embryonic thymus and spleen had upregulated gene expression of IFN-gamma and IL-6 cytokines and of chemokine IL-8. In sharp contrast to cIBDV, embryos exposed to aIBDV had minimal detectable changes in the thymus and bursa, although the rate of apoptosis was enhanced in the thymus. Viral antigen was not detectable in the bursa until after hatch. Thymocytes from these embryos responded vigorously to the mitogens, similar to the response of thymocytes from unexposed control embryos. In addition, aIBDV induced a modest gene upregulation of IFN-gamma, IL-6 and IL-8 in thymus and spleen. Relatively modest response of the embryo to aIBDV is significant because in ovo vaccination with aIBDV-type viruses and several other non-pathogenic viruses result in protective immunity that is well pronounced at hatch.

Replication of infectious bursal disease virus in macrophages and altered tropism of progeny virus.

We serially passaged classical infectious bursal disease virus (cIBDV) and antigenic variant IBDV (vIBDV) in an avian macrophage cell line, NCSU cells, referred as mcIBDV and mvIBDV respectively and examined the in vitro and in vivo characteristics of the macrophage-adapted viruses. NCSU adapted viruses caused earlier destruction of NCSU cells than the unadapted viruses. Nitric oxide (NO) was detected earlier in cultures infected with mcIBDV and mvIBDV than in cultures infected with cIBDV and vIBDV. cIBDV and vIBDV were able to infect DF-1 cells, a chicken embryo fibroblast cell line, only after one replication cycle in NCSU cells. The genetic basis of altered tropism of progeny virus from NCSU cells infected cultures was not identified. No aa substitutions were observed in hypervariable region of VP2 of cIBDV and vIBDV passaged 1 time in NCSU cells whereas both mcIBDV and mvIBDV had multiple aa substitutions. To assess protective efficacy of mcIBDV and mvIBDV, embryonated chicken eggs were inoculated with mcIBDV and mvIBDV at embryonation day 18 (ED 18) and challenged with a virulent cIBDV at 3 weeks of age. mcIBDV and mvIBDV were immunogenic and generated antibody responses and provided 100% protection against cIBDV.

B-cell infiltration in the respiratory mucosa of turkeys exposed to subtype C avian metapneumovirus.

Turkeys exposed to avian metapneumovirus (aMPV) subtype C showed extensive lymphoid cell infiltrations in the nasal turbinates of the upper respiratory tract. The cellular infiltration occurred after the first virus exposure but not after re-exposure. Quantitation of the relative proportions of mucosal immunoglobulin (Ig)A+, IgG+, and IgM+ cells in controls and virus-exposed turkeys revealed that at 7 days after the first virus exposure, when mucosal infiltration was well pronounced, there was a significant increase (P < 0.05) in the numbers of infiltrating IgA+ but not of IgG+ and IgM+ cells. After the second virus exposure, although the overall numbers of mucosal lymphoid cells were similar in the virus-exposed and control turkeys, the relative proportions of IgA+ and IgG+ cells were significantly higher in the virus-exposed turkeys (P < 0.05) than in controls. Furthermore, elevated levels of aMPV-specific IgA were detected in the nasal secretions and the bile of virus-exposed birds after the second but not after the first virus exposure. These results suggest, for the first time, the possible involvement of local mucosal immunoglobulins in the pathogenesis of aMPV in turkeys.

Infectious bursal disease virus infection induces macrophage activation via p38 MAPK and NF-kappaB pathways.

In the present study, we show that infection with infectious bursal disease virus (IBDV) causes activation of macrophages, the key cells involved in inflammatory and immune-regulatory functions. Exposure of cultured spleen macrophages (SM) from SPF chickens to IBDV resulted in the production of nitric oxide (NO). In addition, there was upregulation of mRNA expression of inducible nitric oxide synthase (iNOS), IL-8 and cyclooxygenase-2 (COX-2). The signal transduction pathways involved in macrophage activation were examined. The role of mitogen-activated protein kinases (MAPKs) and nuclear factor-kappaB (NF-kappaB) was tested by using specific pharmacological inhibitors. Addition of p38 MAPK inhibitor, SB-203580 and NF-kappaB inhibitor Bay 11-7082, suppressed IBDV-induced NO production and mRNA expression of iNOS, IL-8 and COX-2. The results suggest that IBDV uses cellular signal transduction machinery, in particular the p38 MAPK and NF-kappaB pathways, to elicit macrophage activation. The increased production of NO, IL-8 and COX-2 by macrophages may contribute to bursa inflammatory responses commonly seen during the acute IBDV infection.

Transcriptional response of avian cells to infection with Newcastle disease virus.

Newcastle disease virus (NDV) causes widespread disease in poultry and wild-birds throughout the world. cDNA microarray analysis was used to examine the effect of NDV infection on host cell transcription. The results show that NDV infection causes an apparent suppression of the interferon response genes during the early stages of infection. In addition, the results reveal transcriptional silencing of cytoskeletal proteins such as the alpha, beta, and gamma types of actin, and a downregulation of the thioredoxin gene, a likely mediator of apoptosis with possible implications in NDV pathogenesis. Comparative analyses show that a majority of genes that were transcriptionally regulated during infection with another common respiratory pathogen of poultry, the avian pneumovirus, remained unaltered during NDV infection, suggesting that even phylogenetically related viruses elicit unique or "signature" patterns of host transcriptional profiles during infection of host cells.

Infection and activation of bursal macrophages by virulent infectious bursal disease virus.

In this study the effect of infectious bursal disease virus (IBDV) on bursal macrophages during the acute phase of the infection was examined. Specific-pathogen-free (SPF) chickens were exposed to virulent IBDV and bursal adherent cells were examined by immunohistochemisrty and RT-PCR for virus infection and by real-time quantitative RT-PCR (qRT-PCR) for mRNA transcripts of proinflammatory cytokines and iNOS. Viral genome was detected in bursal macrophages at 3, 5 and 7 days post-infection (dpi). Immuno-histochemical staining revealed double positive cells for KUL01 (macrophage marker) and intracellular viral proteins, showing viral replication in bursal macrophages of infected chickens. We noted a significant decrease in the total number of bursal macrophages in infected chickens, probably due to the lysis of infected cells. However, likely due to extensive necrosis of B cells, the relative proportion of bursal macrophages was significantly higher (P<0.05) in infected birds at 3 and 5 dpi than in controls. Among the cytokines examined, IL-6 showed the greatest upregulation (100-fold increase) at 3 dpi. Expression of IL-1beta was maximum at 3 dpi whereas IL-18 expression was highest at 1 dpi. Enhanced expression of iNOS mRNA was observed at 5 dpi. Increased expression of the proinflammatory cytokines and iNOS correlated well with the presence of the inflammatory response in the infected bursa. These data suggested that B cells may not be the sole targets for the virus; macrophages and possibly other cells may serve as host for IBDV.

Protection by recombinant viral proteins against a respiratory challenge with virulent avian metapneumovirus.

Protection by recombinant avian metapneumovirus (aMPV) N or M proteins against a respiratory challenge with virulent aMPV was examined. N, M or N+M proteins were administered intramuscularly (IM) with incomplete Freund's adjuvant (IFA) or by the oculonasal (ON) route with cholera toxin-B (CTB). Each turkey received 40 or 80 microg of each recombinant protein. Birds were considered protected against challenge if the challenge virus was not detectable in the choanal swabs by RT-PCR. At a dose of 40 microg/bird, N protein given with IFA by the IM route protected eight out of nine birds. M protein at the same dose protected three out of seven birds, while a combination of N+M proteins (40 microg each) protected three out of four birds. At a dose of 80 microg of each of N and M proteins per bird given with IFA by the IM route, 100% protection was achieved. ON immunization with a mixture of N and M proteins induced partial protection when the proteins were given with CTB; no detectable protection was noted without CTB. N and M proteins induced anti-aMPV antibodies, although protection against virulent virus challenge did not appear to be associated with the level or presence of antibodies.

Detection and localization of avian alphaherpesviruses in embryonic tissues following in ovo exposure.

We investigated whether chicken embryonic tissues are susceptible to infection with virulent Marek's disease virus (MDV). Groups of embryonic day (ED) 17 chicken embryos and 1-day-old chicks were compared for tissue sites of viral persistence of MDV and herpesvirus of turkeys (HVT) in lungs, thymuses, bursae of Fabricius and spleens. MDV DNA was detectable in the lungs and thymuses of embryos at 3 days post-inoculation (DPI) by in situ hybridization, while HVT DNA was only present in embryonic lungs. The target cells in lungs and thymuses appeared non-lymphoid and lymphoid, respectively. By 5 days post-inoculation, both viruses were detectable in all organs examined and persisted after hatch. Although MDV DNA was present in the embryo, there was little evidence of viral replication. These findings demonstrate the differences in pathogenesis of embryonic infection with MDV and HVT and provide evidence that the chicken embryo is susceptible to infection with a virulent avian herpesvirus.

Protective immunity against infectious bursal disease virus in chickens in the absence of virus-specific antibodies.

The role of cell-mediated immunity (CMI) in pathogenesis of infectious bursal disease virus (IBDV) was investigated. One-day-old specific pathogen-free chickens were treated with 3mg of cyclophosphamide (Cy) per chicken for 4 consecutive days and, 3 weeks later, infected with the IBDV-IM strain. Chickens were examined for: (a) mitogenic response of splenocytes to ConA, as an indicator of T-cell functions in vitro, (b) antibody against IBDV by ELISA, (c) IBDV genome in various tissues by RT-PCR and (d) immunological memory. At the time of IBDV infection, Cy-treated chickens had depleted bursal tissue (an avian primary B-cell lymphoid organ), severely compromised antibody-producing ability, but normal T-cell response to ConA. In primary infection, no detectable antibody against IBDV antigen in Cy-treated, IBDV-infected chickens was observed up to 28 days post-infection (PI), while IBDV genome was detected by RT-PCR in spleen, thymus, liver and blood until 10 days PI. Like intact control chickens infected with IBDV, Cy-treated, IBDV-infected chickens suppressed splenocytes responses to ConA from 5 to 10 days PI, suggesting that intact control as well as Cy-treated chickens responded similarly to IBDV infection in the early phase. Following re-infection with IBDV, no detectable secondary antibody response to IBDV as well as IBDV genome in tissues were observed in Cy-treated chickens, while intact control chickens developed vigorous secondary antibody response. Similar to intact control chickens infected with IBDV, Cy-treated chickens after second infection with IBDV did not suppress splenocyte response to ConA. These results suggested that in the absence of detectable anti-IBDV antibodies, protection of Cy-treated chickens from IBDV infection may occur via immunological memory mediated by CMI. We concluded that under normal conditions, IBDV induces a protective antibody response, however, in the absence of antibody, CMI alone is adequate in protecting birds against virulent IBDV.

Reduced efficacy of hemorrhagic enteritis virus vaccine in turkeys exposed to avian pneumovirus.

Avian pneumovirus (APV) is an immunosuppressive respiratory pathogen of turkeys. We examined the effect of APV infection on the vaccine efficacy of hemorrhagic enteritis virus (HEV) vaccines. APV was inoculated in 2-wk-old turkeys. Two or four days later, an attenuated HEV vaccine (HEVp30) or marble spleen disease virus (MSDV) vaccine were administered. Virulent HEV challenge was given 19 days after HEV vaccination. APV exposure compromised the ability of HEVp30 and MSDV to protect turkeys against virulent HEV. The protective index values were as follows: MSDV (100%) versus APV + MSDV (0%) (P < 0.05); HEVp30 (60%) versus APV + HEVp30 (30%) (P < 0.05) (Experiment I) and HEVp30 (56%) versus APV + HEVp30 (20%) (P < 0.05) (Experiment II). These data indicated that APV reduced the efficacy of HEV vaccines in turkeys.

Pathogenic and immunosuppressive effects of avian pneumovirus in turkeys.

Avian pneumovirus (APV) causes a respiratory disease in turkeys. The virus has been associated with morbidity and mortality due to secondary infections. Our objective was to determine if APV caused immunosuppression in the T-cell or B-cell compartments and to study the pathogenesis of the disease in APV maternal antibody-lacking 2-wk-old commercial turkeys. APV was administered by the eyedrop/intranasal route. Observations were made for gross lesions, viral genome, and T-cell mitogenesis and cytokine secretion at 3, 5, 7, 14, and 21 days postinoculation (DPI). During the acute phase of the disease that lasted for about 1 wk, the turkeys exposed to APV showed clinical signs characterized by nasal discharge and sinus swelling. Virus genome was detected by in situ hybridization in cells of turbinates and trachea at 3 and 5 DPI. At 3 and 5 DPI, spleen cells of the birds infected with APV markedly decreased proliferative response to concanavalin A (Con A). Con A and lipopolysaccharide stimulation of spleen cells from virus-exposed turkeys resulted in accumulation of nitric oxide-inducing factors (NOIF) in the culture fluid. NOIF were not detected in culture fluids of Con A-stimulated spleen cells of virus-free turkeys. APV did not compromise the antibody-producing ability of turkeys against several extraneous antigens such as Brucella abortus and tetanus toxoid.

Effect of an immunomodulator on the efficacy of an attenuated vaccine against avian pneumovirus in turkeys.

Since 1997, avian pneumovirus (APV) has caused estimated annual losses of $15 million to the Minnesota turkey industry. In order to develop an attenuated live vaccine against APV, we serially passaged a Minnesota isolate of APV (APV/MN/turkey/1-a/97) in vitro in cell cultures for 41 passages. Laboratory experiments with this high-passage virus (P41) indicated that the attenuated virus provided immunogenic protection to turkeys against challenge with virulent APV, although some birds showed mild to moderate dinical signs after inoculation. To reduce the residual pathogenicity of P41, while maintaining its immunogenicity, we decided to vaccinate turkeys with P41 in the presence of an immunomodulator, S-28828 (1-n-butyl-2-ethoxymethyl-1H-imidazo[4,5-c]quinolin-4-amine-hydrochloride), which is a potent cytokine inducer. The combined inoculation of S-28828 (5 mg/kg body weight) and P41 resulted in a significant reduction in the incidence of virus-induced clinical signs in comparison with birds that received P41 without immunomodulator (P < 0.05). Only 17% of birds inoculated with S-28828 + APV P41 showed mild respiratory symptoms at 5 days postinoculation as compared with 46% of the vaccinated turkeys that did not receive S-28828. Vaccination with either P41 or with P41 + S-28828 protected turkeys against dinical signs and viral replication after challenge with virulent APV. These results indicate that immunomodulators, such as S-28828, may act as good vaccine adjuvants that can reduce the pathogenicity but maintain the immunogenicity of partially attenuated vaccines.

Protection against avian metapneumovirus subtype C in turkeys immunized via the respiratory tract with inactivated virus.

Avian metapneumovirus subtype C (aMPV/C) causes a severe upper respiratory tract (URT) infection in turkeys. Turkeys were inoculated oculonasally with inactivated aMPV/C adjuvanted with synthetic double-stranded RNA polyriboinosinic polyribocytidylic acid (Poly IC). Immunized turkeys had elevated numbers of mucosal IgA+ cells in the URT and increased levels of virus-specific IgG and IgA in the lachrymal fluid and IgG in the serum. After 7 or 21 days post immunization, turkeys were challenged oculonasally with pathogenic aMPV/C. Immunized groups were protected against respiratory lesions induced by the challenge virus. Further, the viral copy number of the challenge virus in the URT were significantly lower in the immunized turkeys than in the unimmunized turkeys (P<0.05). These results showed that inactivated aMPV/C administered by the respiratory route induced protective immunity against pathogenic virus challenge.

Pathogenic and immunogenic responses in turkeys following in ovo exposure to avian metapneumovirus subtype C.

Commercial turkey eggs, free of antibodies to avian metapneumovirus subtype C (aMPV/C), were inoculated with aMPV/C at embryonation day (ED) 24. There was no detectable effect of virus inoculation on the hatchability of eggs. At 4 days post inoculation (DPI) (the day of hatch (ED 28)) and 9 DPI (5 days after hatch), virus replication was detected by quantitative RT-PCR in the turbinate, trachea and lung but not in the thymus or spleen. Mild histological lesions characterized by lymphoid cell infiltration were evident in the turbinate mucosa. Virus exposure inhibited the mitogenic response of splenocytes and thymocytes and upregulated gene expression of IFN-γ and IL-10 in the turbinate tissue. Turkeys hatching from virus-exposed eggs had aMPV/C-specific IgG in the serum and the lachrymal fluid. At 3 week of age, in ovo immunized turkeys were protected against a challenge with pathogenic aMPV/C.