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.     

Serologic and genetic characterization of North American H3N2 swine influenza A viruses

The H3N2 subtype of influenza A viruses isolated from pigs in the United States and Canada has shown both genetic and antigenic diversity. The objective of this study was to determine the serologic and genetic characteristics of contemporary strains of these viruses. Genetic analysis of 18 reference strains and 8 selected strains demonstrated differences in 1% to 9% of the nucleotides of the hemagglutinin (HA) gene. Phylogenetic analysis of the HA gene revealed 3 genetic clusters, as well as divergence of cluster III viruses from a cluster III prototype virus (A/Swine/Illinois/21587/99). By means of 1-way cross-hemagglutination inhibition with antiserum against 5 field isolates and 3 vaccine viruses, most of 97 isolates tested could be placed in 1 of 3 serogroups. The several isolates that did not react with any antiserum were in genetic cluster III, which suggests that continuous antigenic drift in cluster III may have resulted in virus variants. The efficacy of commercial vaccines against these virus variants should be evaluated with vaccination and challenge studies.     

Low stress mechanical properties of fabrics woven from bamboo viscose blended yarns

This paper presents the low stress mechanical properties of plain fabrics woven from cotton, bamboo viscose and cotton-bamboo viscose blended yarns. Three blends (100 % cotton, 50:50 cotton-bamboo and 100 % bamboo) were used to produce three yarn counts (20, 25 and 30 Ne). Each of these yarns was used to make fabrics with different pick densities (50, 60 and 70 picks per inch). It was found that bending rigidity, bending hysteresis, shear rigidity, shear hysteresis and compressibility is lower for bamboo fabrics as compared to those of 100 % cotton fabrics. On the other hand, extensibility, tensile energy and compressional resilience are higher for 100 % bamboo fabrics than 100 % cotton fabrics. Higher pick density increases linearity of load-elongation curve, bending rigidity, shear rigidity and compressional resilience. Shear and bending rigidities show very good correlation with the respective hysteresis values.     

Identification of the tet(B) resistance gene in Streptococcus suis

The tetracycline resistance gene, tet(B), has been described previously in Gram negative bacteria. In this study tet(B) was detected in plasmid extracts from 17/111 (15%) Streptococcus suis isolates from diseased pigs, representing the first report of this resistance gene in Gram positive bacteria.     

Susceptibility of various ceil culture systems to pseudorabies virus

A comparative study was carried out to determine the susceptibility of five different cell lines to pseudorabies virus (PRV), a herpes virus of pigs. The cell systems tested were swine testicle (ST), mink lung (ML), equine dermal (ED), porcine kidney (PK₁₅), and bovine turbinate (BT) cells. Virus titers obtained were 10^4.88, 10^4.38, 10^3.75, 10^2.63, and 10^0.25 for ML, ST, PK₁₅, BT and ED cells, respectively indicating that ML, ST, and PK₁₅ are optimal cell lines for the growth of PRV whereas BT and ED are not very sensitive.     

Isolation and characterization of porcine circovirus type-2 from sera of stillborn fetuses

In order to examine an association between porcine circovirus type-2 (PCV2) infection and reproductive failure in pigs, sera (n = 171) from stillborn fetuses were collected from 3 different farms with prolonged histories of reproductive problems. These sera were tested for the presence of antibodies to PCV2 using an immunoperoxidase monolayer assay. Of the 171 sera tested, 28 had PCV2 antibody titers of ≥ 1:16. When these 28 samples were tested by a polymerase chain reaction assay, 13 were found to contain PCV2 viral DNA. Of these 13 samples containing both PCV2 antibodies and viral DNA, 9 yielded PCV2 on virus isolation. Amino acid sequences comprising open reading frame 2 of PCV2 from 2 of these isolates were compared to PCV2 isolates from cases of post-weaning multi-systemic wasting syndrome (PMWS). The amino acid sequences of the 2 isolates from stillborn pigs were shown to be nearly identical to each other, as well as to other PCV2 isolates associated with reproductive failure. When compared with PMWS isolates, the isolates from the stillborn fetuses showed differences of at least 2 amino acids. These results confirm previous findings that transplacental infection of PCV2 occurs in the field and that stillbirths in pigs may be associated with PCV2 infections. At present, the significance of minor differences in amino acid sequences is not known.     

Evaluation of transmission of swine influenza type A subtype H1N2 virus in seropositive pigs

OBJECTIVE: To examine clinical signs, virus infection and shedding, and transmission of swine influenza virus (SIV) subtype H1N2 among seropositive pigs. ANIMALS: Eighteen 3-week-old pigs with maternal antibodies against SIV subtypes H1N1, H3N2, and H1N2. PROCEDURE: Ten pigs (principal) were inoculated intranasally with subtype H1N2 and 2 groups of contact pigs (n = 4) each were mixed with principal pigs on day 7 (group 1) or 28 (group 2). Two principal pigs each were necropsied on days 4, 14, 21, 28, and 42 days after inoculation. Four pigs in each contact group were necropsied 35 and 14 days after contact. Virus excretion was evaluated after inoculation or contact. Lung lesions and the presence of SIV in various tissues were examined. RESULTS: Mild coughing and increased rectal temperature were observed in principal pigs but not in contact pigs. Nasal virus shedding was detected in all principal pigs from day 2 for 3 to 5 days, in group 1 pigs from day 2 for 4 to 9 days after contact, and in group 2 pigs from day 4 for 2 to 6 days after contact. Trachea, lung, and lymph node specimens from infected pigs contained virus. Antibody titers against all 3 subtypes in all pigs gradually decreased. CONCLUSIONS AND CLINICAL RELEVANCE: Protection from viral infection and shedding was not observed in pigs with maternal antibodies, but clinical disease did not develop. Vaccination programs and good management practices should be considered for control of SIV subtype H1N2 infection on swine farms.     

Serologic evidence of exposure of raptors to influenza A virus

Serum or plasma samples from raptors that prey or scavenge upon aquatic birds were tested by a commercially available blocking enzyme-linked immunosorbent assay for the evidence of antibodies to influenza A virus. Samples were taken from birds (n = 616) admitted to two rehabilitation centers in the United States. In addition, samples from 472 migrating peregrine falcons (Falco peregrinus) trapped on autumnal and vernal migrations for banding purposes were also tested. Only bald eagles were notably seropositive (22/406). One each of peregrine falcon, great horned owl (Bubo virginianus), and Cooper's hawk (Accipiter cooperi) from a total of 472, 81, and 100, respectively, were also positive. None of the turkey vultures (n = 21) or black vultures (n = 8) was positive. No clinical signs referable to avian influenza were seen in any bird at the time of capture. These data indicate that, among raptors, bald eagles do have exposure to influenza A viruses.     

Potato bacterial wilt in India caused by strains of phylotype I, II and IV of Ralstonia solanacearum

Bacterial wilt or brown rot is one of the most devastating diseases of potato caused by a bacterium Ralstonia solanacearum (Smith 1986) Yabuuchi et al. (Microbiol Immunol 39:897–904 1995). Traditionally, R. solanacearum is classified into five races (r) on the basis of differences in host range and six biovars (bvs) on the basis of biochemical properties. Recently using molecular methods, R.?solanacearum has been classified into phylotypes based on the intergenic transcribed sequence of the ribosomal RNA genes 16S and 23S and into sequevars based on the endoglucanase gene (egl) sequence. In the present study, 75 bacterial strains, isolated from wilt infected potatoes from various potato growing regions of India, were classified by traditional and molecular methods. The identity of all the strains was confirmed as R. solanacearum as expected single 280-bp fragment resulted in all the strains following PCR amplification using R. solanacearum specific universal primer pair 759/760. Biovar (bv) analysis, based on utilization of disaccharide sugars and hexose alcohols, categorised the 75 strains into bv2 (78.7 %), 2 T (5.3 %), 3 (5.3 %) and 4 (10.7 %). The phylotype specific multiplex PCR assigned 78.7 % strains to phylotype II, 16.0 % to phylotype I and 5.3 % to phylotype IV. Phylogenetic analysis of egl gene sequences clustered all fifty nine phylotype II (bv2) strains with reference strain IPO1609 (IIB-1), all four phylotype IV (bv2T) strains with reference strain MAFF301558 (IV-8), three phylotype I (bv3) strains with reference strain MAFF211479 (I-30) and all eight phylotype I (bv4) and one phylotype I (bv3) strain with reference strain CIP365 (I-45). The study concluded that the Indian potato strains of R. solanacearum belong to three out of four phylotypes namely: the Asian phylotype I, the American phylotype II, and the Indonesian phylotype IV. This is the first study to address the diversity of R. solanacearum from potato in India using phylotype and sequevar scheme. We also report here for the first time the occurrence of phylotype IV sequevar 8 (bv2T) strain of R. solanacearum causing potato bacterial wilt in mid hills of Meghalaya in India.