Enhancing epitope of PEDV spike protein

Porcine epidemic diarrhea virus (PEDV) is the causative agent of a highly contagious enteric disease of pigs characterized by diarrhea, vomiting, and severe dehydration. PEDV infects pigs of all ages, but neonatal pigs during the first week of life are highly susceptible; the mortality rates among newborn piglets may reach 80–100%. Thus, PEDV is regarded as one of the most devastating pig viruses that cause huge economic damage to pig industries worldwide. Vaccination of sows and gilts at the pre-fertilization or pre-farrowing stage is a good strategy for the protection of suckling piglets against PEDV through the acquisition of the lactating immunity. However, vaccination of the mother pigs for inducing a high level of virus-neutralizing antibodies is complicated with unstandardized immunization protocol and unreliable outcomes. Besides, the vaccine may also induce enhancing antibodies that promote virus entry and replication, so-called antibody-dependent enhancement (ADE), which aggravates the disease upon new virus exposure. Recognition of the virus epitope that induces the production of the enhancing antibodies is an existential necessity for safe and effective PEDV vaccine design. In this study, the enhancing epitope of the PEDV spike (S) protein was revealed for the first time, by using phage display technology and mouse monoclonal antibody (mAbG3) that bound to the PEDV S1 subunit of the S protein and enhanced PEDV entry into permissive Vero cells that lack Fc receptor. The phages displaying mAbG3-bound peptides derived from the phage library by panning with the mAbG3 matched with several regions in the S1-0 sub-domain of the PEDV S1 subunit, indicating that the epitope is discontinuous (conformational). The mAbG3-bound phage sequence also matched with a linear sequence of the S1-BCD sub-domains. Immunological assays verified the phage mimotope results. Although the molecular mechanism of ADE caused by the mAbG3 via binding to the newly identified S1 enhancing epitope awaits investigation, the data obtained from this study are helpful and useful in designing a safe and effective PEDV protein subunit/DNA vaccine devoid of the enhancing epitope.

Antimicrobial Resistance Phenotypes and Genotypes of Salmonella spp. Isolated from Commercial Duck Meat Production in Thailand and Their Minimal Inhibitory Concentration of Disinfectants

Salmonella is an important foodborne bacterium that has become increasingly resistant to critical antimicrobial and disinfectant agents. The aim of this study was to characterize antimicrobial and disinfectant resistance of Salmonella spp. isolated from ducks raised for meat in Nakhon Pathom province, Thailand. A total of 694 fecal samples from ducks were collected in 2018. Of which, 85 samples were positive for Salmonella (12.2%), and 12 Salmonella serovars were identified from 125 Salmonella isolates. The Altona serovar was the predominant serotype found in this study (36.5%). All isolates showed resistance to at least one class of antimicrobial, and 23.2% displayed multidrug resistance (MDR) phenotype. The bla_TEM, aadA2, strA, and dfrA12 genes were detected in antibiotic-resistant strains of Salmonella, whereas the genes within a plasmid-borne qnr family that presented in fluoroquinolone-susceptible Salmonella strains were qnrB (3.8%) and qnrS (1.5%). The minimum inhibitory concentrations of benzalkonium chloride (BKC), cetylpyridium chloride (CPC), and hexadecyltrimethyl ammonium bromide (CTAB) ranged between 128 and 512 μg/mL, while that of didecyldimethylammonium chloride (DDAC) was between 32 and 128 μg/mL. The presences of qacEΔ1, mdfA, sugE(c), sugE(p), and ydgE genes were less prevalent (0.8-1.6%). Taken together, our results indicate that duck is an important source of Salmonella with antimicrobial resistance in food-producing animals. Active surveillance programs for antimicrobial and disinfectant resistance in duck production are needed for an early detection of resistance strains of public health importance.

Detection of antibodies to duck tembusu virus in human population with or without the history of contact with ducks

Duck tembusu virus (DTMUV) is an emerging duck pathogen in China and other Asian countries. It is unclear whether this emerging zoonotic infection poses a threat to humans. A previous study in 2012 showed surprisingly high rates of seropositivity and positive viral detection by RT-PCR in duck farm workers in China. To understand the nature of the threat of this emerging virus, we studied the neutralizing antibody response to a local isolate of DTMUV in an at-risk population, who were workers in duck farms and residents around farming areas in Central Thailand where DTMUV had been previously detected, and in a not-at-risk population, who were people living in the same or neighbouring province, but at a distance from the farms and who had no contact with ducks. The sera from the at-risk population showed higher anti-DTMUV neutralizing antibody titres as compared with those of the not-at-risk population. However, within the at-risk population, workers with direct contact with ducks did not show higher neutralizing titres than those without direct contact. Interestingly, some people in the not-at-risk group also displayed high neutralizing antibody titres to DTMUV. These sera were tested against other endemic Flaviviruses and showed no or low cross-reactivity suggesting the specificity of the neutralizing activity against DTMUV. These data raise a possibility of DTMUV as a potential zoonotic pathogen but the mode of transmission of the virus from ducks or other possible hosts to humans should be explored further.

Pb, Cd, and Cu Play a Major Role in Health Risk from Contamination in Duck Meat and Offal for Food Production in Thailand

Zinc, Pb, Cd, Mn, Fe, Cr, and Cu levels in duck meat from large-scale farms have been found to be significantly higher than those from free-grazing duck farms. Zinc, Co, Mn, Cr, and Cu contamination levels in duck liver from large-scale farms were significantly higher than those from free-grazing farms; only Cd in duck liver from free-grazing farms was higher than in liver samples from large-scale farms at P < 0.05. Lead, Cd, Fe, and Cr levels in duck intestine samples from free-grazing farms were higher than large-scale farms at P < 0.001. Moreover, the average concentrations of Pb in duck meat and liver samples from large-scale farms and Cd levels in duck liver samples from free-grazing farm also exceeded the FAO/WHO and Codex Alimentarius limits by 100% (55/55), 100% (54/54), and 67.6% (23/34), respectively. PCA analysis showed a strong positive relationship between the eight metals in meat, liver, and intestine was > 0.69, > 0.69, and > 0.72, in order. The relationship of the liver combined with the intestine was > 0.65. This study indicated that consumers may incur health risks from long-term consumption of duck due to high Pb and Cd concentrations from both types of farms, particularly from large-scale duck farms.

Comparison of immunogenicity between intradermal and intramuscular injections of repeated annual identical influenza virus strains post-pandemic (2011-2012) in COPD patients

We compared the antibody responses and persistence of the reduced-dose, 9 µg hemagglutinin (HA)/strain intradermal (ID) injection via the Mantoux technique and the 15 μg HA/strain intramuscular (IM) injection of the repeated annual identical trivalent, inactivated, split-virion vaccine 2011-2012 in chronic obstructive pulmonary disease (COPD) patients. Eighty patients were randomized to ID (n = 41) and IM (n = 39) groups. Four weeks post-vaccination, the antibody responses of the two groups were similar; those for influenza A(H1N1)pdm09 and influenza A(H3N2)-but not influenza B-met the criteria of the Committee for Proprietary Medicinal Products (CPMP). The antibody responses for influenza A(H1N1)pdm09 rapidly declined in both groups, especially with the ID injection, whereas those for influenza A(H3N2) maintained above the CPMP criteria throughout 12 months post-vaccination. The geometric mean titres for influenza A(H1N1)pdm09 persisted above the protective threshold (≥ 40) until 6 months post-vaccination in both the ID and IM groups. The seroprotection rates of the ID and IM groups were above 60% until 3 months and 6 months post-vaccination, respectively. In conclusion, the 9 μg HA/strain ID injection of vaccine 2011-2012 elicited antibody responses similar to the standard dose of 15 μg of the HA/strain IM injection at 4 weeks post-vaccination. However, the antibody responses for influenza A(H1N1)pdm09 rapidly declined, especially in the case of the ID injection, whereas they were comparable for influenza A(H3N2). Additional strategies for increasing vaccine durability should be considered, especially for new pandemic strains affecting elderly COPD patients.

Carcinogenic and non-carcinogenic risk assessment of heavy metals contamination in duck eggs and meat as a warning scenario in Thailand

The aim of this study was to determine the levels of Pb, Cd, Co and Cr in duck eggs and duck meat and to assess the risk of carcinogenic and non-carcinogenic effects caused by the consumption of duck products collected in Thailand. The human health risk assessment refers to the formulation of the USEPA standard focused on Estimated Daily Intake (EDI), Incremental Lifetime Cancer Risk (ILCR), Target Hazard Quotient (THQ) and Total Target Hazard Quotient (TTHQ). Ninety-eight percent of duck egg samples in this study were contaminated with Pb, with the average level typically above the standard limit. The EDI evaluation of heavy metal in children was the highest for all metals in the eggs. The calculated ILCR levels of Pb, Cd and Cr in eggs and meat consumption were higher than 10^-4 in children, adults, males, and females. Children were at risk when consuming contaminated duck eggs and the risk was higher than in adults by 3.9 times for Pb, Cd and Cr. This finding suggests that there is a high probability of cancer risk, particularly for children, which is higher than adults by absorption of these carcinogenic heavy metals through eggs. The calculation of THQ if consuming heavy metals contaminated duck eggs and meat in human exposure (70years) could conclude that the THQ male was higher than the female for all metals. However, the calculations of TTHQ for Pb, Cd, Co and Cr contamination in a duck egg and meat scenario for adults, males and females were still below the standard limit of 1, which means there was no risk, although there could be adverse health effects. This study suggested that children should be the focus of long-term monitoring for evaluating the carcinogenicity of these metals, more specifically in males.

Heavy Metal (Cd and Pb) and Aflatoxin Contamination in Tissues and Eggs from Free Grazing Ducks and Their Environment in Central Thailand

The cross-sectional study of heavy metals and aflatoxins was conducted by studying duck egg, blood, liver, feed, and water samples from 11 free grazing farms. The duck feed, soil, and rice samples were lower than the standard limit for aflatoxins at 20 ng g^-1. The highest levels of aflatoxin were detected in the liver, intestine, and egg yolk; these were 3.04, 1.73, and 4.56 ng g^-1 respectively, while the average levels were 1.6 ± 0.73, 1.31 ± 0.23, and 1.87 ± 0.99 ng g^-1, respectively. Interestingly, aflatoxin was not detected in any of the egg white albumin samples (90/90 samples), whereas aflatoxin contamination was predominantly found in the yolk. Additionally, the means and standard deviations of Pb and Cd found in the duck eggs were 118.61 ± 22.25 and 13.84 ± 9.06 ng g^-1 respectively. The maximum levels of Pb and Cd in eggs were 134.34 and 29.72 ng g^-1, respectively. Moreover, Pb contamination occurred in the duck liver tissue in 93.61% (88/94) of the samples, whereas Cd contamination was found in 100% (100/100). The maximum levels of Pb and Cd in the duck liver tissues were 606.16 and 22,946.20 ng g^-1, which was higher than those in the eggs. Pb contamination in the water from rice paddy fields after grazing was significantly higher than that in water samples taken before grazing. This is the first report of Pb and Cd contamination in blood, egg, and liver samples of free grazing ducks in Thailand.

Comparison of zinc, lead, cadmium, cobalt, manganese, iron, chromium and copper in duck eggs from three duck farm systems in Central and Western, Thailand

This was a comparative study of the heavy metal levels (Zn, Pb, Cd, Co, Mn, Fe, Cr and Cu) in eggs from free grazing duck, small-scale, and large-scale farms in central and western regions of Thailand. A questionnaire was used to gather demographic data for the analysis of heavy metal contamination in feed, drinking water and wastewater. The correlation between the amounts of heavy metal contamination in eggs was studied against the heavy metals found in feed, drinking water and wastewater. The levels of Pb, Cd, Cr and Cu in eggs from large-scale farms were significantly higher than small farms and free grazing farms at P < 0.001. Zn in eggs from free grazing farms was higher than in the small farms and large-scale farms sampled. The contamination of Pb in eggs from all types of farms exceeded the standard limits of ACFS 6703-2005. The average levels of Pb in the eggs from small-scale farms correlated significantly with the level of Pb found in the feed at P < 0.05, while the average levels of Pb in eggs from free grazing duck farms correlated significantly with the levels of Pb found in the drinking water at P < 0.05. Additionally, the average level of Cu in duck egg from large-scale farms correlated significantly with the level of Cu found in the feeds at P < 0.001. Furthermore, from a calculation of the provisional tolerable daily intake (WHO-FAO) of heavy metals in this study, it was concluded that consumers face health risks from Cd contamination. Thus, heavy metal contamination, especially Pb and Cd in duck egg, must be of concern due to the health risks and the route of crucial heavy metals contamination should be elucidated and long - term monitoring of heavy metals posing health effects in farm systems should be carried out.

Health Risk Contamination of Heavy Metals in Yolk and Albumen of Duck Eggs Collected in Central and Western Thailand

Two hundred duck egg samples were collected from 20 farms in Central and Western Thailand. The levels of Zn, Co, Mn, Fe, and Cr in yolks were found significantly higher than in albumen, whereas the levels of Cd and Cu contaminations in egg albumen were significantly higher than in yolks. The mean level of Pb contamination in whole eggs was 4.06 ± 2.70 mg kg^-1 dry weight. This level was higher than the Thai agricultural standard no. 6703-2005 for duck eggs set at 0.1 ppm for the magnitude of 40.6 times. In addition, 98% (196/200) of duck egg samples had Pb levels higher than the standard limit. However, the calculation of daily intakes of Pb, Cd, and Cu contamination in the current study of duck eggs shows that these metals were lower than the World Health Organization and the Food and Agriculture Organization provisional tolerated daily intake. These levels may, however, present a health risk resulting from a long-term exposure. It can be concluded that consumers may be at risk of Pb, Cd, and Cu contamination if they consume contaminated duck eggs. In addition, long-term monitoring of the health risks of heavy metals contamination should be conducted concerning the duck egg production system in Thailand.

Hepatic FGF21 mediates sex differences in high-fat high-fructose diet-induced fatty liver

The role of gender in the progression of fatty liver due to chronic high-fat high-fructose diet (HFFD) has not been studied. The present investigation assessed whether HFFD induced hepatic perturbations differently between the sexes and examined the potential mechanisms. Male, female, and ovariectomized (OVX) Sprague-Dawley rats were fed either a control diet or HFFD for 12 wk. Indexes of liver damage and hepatic steatosis were analyzed biochemically and histologically together with monitoring changes in hepatic gene and protein expression. HFFD induced a higher degree of hepatic steatosis in females, with significant increases in proteins involved in hepatic lipogenesis, whereas HFFD significantly induced liver injury, inflammation, and oxidative stress only in males. Interestingly, a significant increase in hepatic fibroblast growth factor 21 (FGF21) protein expression was observed in HFFD-fed males but not in HFFD-fed females. Ovarian hormone deprivation by itself led to a significant reduction in FGF21 with hepatic steatosis, and HFFD further aggravated hepatic fat accumulation in OVX rats. Importantly, estrogen replacement restored hepatic FGF21 levels and reduced hepatic steatosis in HFFD-fed OVX rats. Collectively, our results indicate that male rats are more susceptible to HFFD-induced hepatic inflammation and that the mechanism underlying this sex dimorphism is mediated through hepatic FGF21 expression. Our findings reveal sex differences in the development of HFFD-induced fatty liver and indicate the protective role of estrogen against HFFD-induced hepatic steatosis.

The immunogenicity of the intradermal injection of seasonal trivalent influenza vaccine containing influenza A(H1N1)pdm09 in COPD patients soon after a pandemic

The antibody responses of a reduced-dose intradermal seasonal influenza vaccination have never been studied in COPD patients soon after a pandemic. A total of 149 COPD patients (60 y of age or older) were randomized to receive trivalent influenza vaccine (Sanofi-Pasteur, France) either 9 µg of hemagglutinin (HA) per strain split into 2-site intradermal (ID) injections via the Mantoux technique or one intramuscular (IM) injection of 15 µg of HA per strain. The geometric mean titers, seroconversion factors, seroconversion rates and seroprotection rates for influenza A(H3N2) and B administered through the ID injection (n = 75) were similar to those obtained with the IM injection (n = 74) 4 weeks post-vaccination. The antibody responses for influenza A(H1N1)pdm09 administered through the ID injection were lower than those obtained with the IM injection, but all of these responses met the 3 criteria proposed by the Committee for Proprietary Medicinal Products (CPMP) for annual re-licensure. The seroprotection rates 4 weeks post-vaccination for influenza A(H1N1)pdm09 were 64.0% (95%CI 52.7-74.0%) in the ID group vs. 78.4% (95% CI 67.6-86.3%) in the IM group (p = 0.053). Influenza-related acute respiratory illness (ARI), diagnosed as a 4-fold rise in HI titers with a convalescent titer > 1:40, and/or the RT-PCR between the ID group (5.3%) and the IM group (8.1%) were not significantly different. The reduced-dose intradermal influenza vaccine may expand vaccine coverage in cases of vaccine shortage.

Developing an indirect ELISA based on recombinant hexon protein for serological detection of inclusion body hepatitis in chickens

Fowl adenovirus (FAdv) serotype 2 causes inclusion body hepatitis (IBH) disease which adversely affects the broiler industry in Thailand. We developed an indirect ELISA based on the recombinant hexon protein produced by E. coli. The recombinant hexon protein was tested with sera, in both infected and noninfected chickens. The recombinant hexon protein was standardized with an antigen concentration of 3.75 µg/ml and test sera. The intra- and inter-assays were repeatable. The cutoff value from TG-ROC curve analysis was 0.106. The specificity and sensitivity were 80 and 80%, respectively. The correlation coefficient (r) of absorbance values from this ELISA compared with the serum neutralization test was 0.76. This ELISA might be helpful for IBH diagnosis and surveillance.

Human monoclonal ScFv that bind to different functional domains of M2 and inhibit H5N1 influenza virus replication

Background

Novel effective anti-influenza agent that tolerates influenza virus antigenic variation is needed. Highly conserved influenza virus M2 protein has multiple pivotal functions including ion channel activity for vRNP uncoating, anti-autophagy and virus assembly, morphogenesis and release. Thus, M2 is an attractive target of anti-influenza agents including small molecular drugs and specific antibodies.

Methods

Fully human monoclonal single chain antibodies (HuScFv) specific to recombinant and native M2 proteins of A/H5N1 virus were produced from huscfv-phagemid transformed E. coli clones selected from a HuScFv phage display library using recombinant M2 of clade 1 A/H5N1 as panning antigen. The HuScFv were tested for their ability to inhibit replication of A/H5N1 of both homologous and heterologous clades. M2 domains bound by HuScFv of individual E. coli clones were identified by phage mimotope searching and computerized molecular docking.

Results

HuScFv derived from four huscfv-phagemid transformed E. coli clones (no. 2, 19, 23 and 27) showed different amino acid sequences particularly at the CDRs. Cells infected with A/H5N1 influenza viruses (both adamantane sensitive and resistant) that had been exposed to the HuScFv had reduced virus release and intracellular virus. Phage peptide mimotope search and multiple alignments revealed that conformational epitopes of HuScFv2 located at the residues important for ion channel activity, anti-autophagy and M1 binding; epitopic residues of HuScFv19 located at the M2 amphipathic helix and cytoplasmic tail important for anti-autophagy, virus assembly, morphogenesis and release; epitope of HuScFv23 involved residues important for the M2 activities similar to HuScFv2 and also amphipathic helix residues for viral budding and release while HuScFv27 epitope spanned ectodomain, ion channel and anti-autophagy residues. Results of computerized homology modelling and molecular docking conformed to the epitope identification by phages.

Conclusions

HuScFv that bound to highly conserved epitopes across influenza A subtypes and human pathogenic H5N1clades located on different functional domains of M2 were produced. The HuScFv reduced viral release and intracellular virus of infected cells. While the molecular mechanisms of the HuScFv await experimental validation, the small human antibody fragments have high potential for developing further as a safe, novel and mutation tolerable anti-influenza agent especially against drug resistant variants.

Erythrocyte binding preference of human pandemic influenza virus a and its effect on antibody response detection

BACKGROUND

Validation of hemagglutination inhibition (HI) assays is important for evaluating antibody responses to influenza virus, and selection of erythrocytes for use in these assays is important. This study aimed to determine the correlation between receptor binding specificity and effectiveness of the HI assay for detecting antibody response to pandemic influenza H1N1 (pH1N1) virus.

METHODS

Hemagglutination (HA) tests were performed using erythrocytes from 6 species. Subsequently, 8 hemagglutinating units of pH1N1 from each species were titrated by real-time reverse transcription-PCR. To investigate the effect of erythrocyte binding preference on HI antibody titers, comparisons of HI with microneutralization (MN) assays were performed.

RESULTS

Goose erythrocytes showed most specific binding with pH1N1, while HA titers using human erythrocytes were comparable to those using turkey erythrocytes. The erythrocyte binding efficiency was shown to have an impact on antibody detection. Comparing MN titers, HI titers using turkey erythrocytes yielded the most accurate results, while those using goose erythrocytes produced the highest geometric mean titer. Human blood group O erythrocytes lacking a specific antibody yielded results most comparable to those obtained using turkey erythrocytes. Further, pre-existing antibody to pH1N1 and different erythrocyte species can distort HI assay results.

CONCLUSIONS

HI assay, using turkey and human erythrocytes, yielded the most comparable and applicable results for pH1N1 than those by MN assay, and using goose erythrocytes may lead to overestimated titers. Selection of appropriate erythrocyte species for HI assay allows construction of a more reliable database, which is essential for further investigations and control of virus epidemics.

Avian and human influenza A virus receptors in trachea and lung of animals

BACKGROUND

Influenza A viruses are capable of crossing the specific barrier between human beings and animals resulting in interspecies transmission. The important factor of potential infectivity of influenza A viruses is the suitability of the receptor binding site of the host and viruses. The affinities of avian and human influenza virus to bind with the receptors and the distributions of receptors in animals are different.

OBJECTIVE

This study aims to investigate the anatomical distribution of avian and human influenza virus receptors using the double staining lectin histochemistry method.

METHODS

Double staining of lectin histochemistry was performed to identify both SA alpha2,3 Gal and SA alpha2,6 Gal receptors in trachea and lung tissue of dogs, cats, tigers, ferret, pigs, ducks and chickens.

RESULTS

We have demonstrated that avian and human influenza virus receptors were abundantly present in trachea, bronchus and bronchiole, but in alveoli of dogs, cats and tigers showed SA alpha2,6 Gal only. Furthermore, endothelial cells in lung tissues showed presence of SA alpha2,3 Gal.

CONCLUSION

The positive sites of both receptors in respiratory tract, especially in the trachea, suggest that all mammalian species studied can be infected with avian influenza virus. These findings suggested that dogs and cats in close contact with humans should be of greater concern as an intermediate host for avian influenza A in which there is the potential for viral adaptation and reassortment.

A human single chain transbody specific to matrix protein (M1) interferes with the replication of influenza A virus

A cell penetrating format of human single chain antibody (HuScFv) specific to matrix protein (M1) of influenza A virus was produced by molecular linking of the gene sequence encoding the HuScFv (huscfv) to a protein transduction domain, i.e., penetratin (PEN) of the Drosophila homeodomain. DNA of a recombinant phagemid vector carrying the huscfv was used as a platform template in a three-step PCR for generating a nucleotide sequence encoding a 16 amino acid PEN peptide. The PEN-HuScFv had negligible cytotoxicity on living MDCK cells. They were readily translocated across the cell membrane and bound to native M1 in the A/H5N1-infected cells as revealed by immunofluorescent confocal microscopy. The PEN-HuScFv, when used to treat the influenza virus infected cells, reduced the number of viruses released from the cells. In conclusion, the cell penetrating M1-specific HuScFv, a transbody, produced in this study affected the influenza A virus life cycle in living mammalian cells. While the molecular mechanisms of the PEN-HuScFv need more investigation, the reagent warrants further testing in animals before developing it into a human immunotherapeutic anti-influenza formula.

Heterosubtypic immunity to influenza mediated by liposome adjuvanted H5N1 recombinant protein vaccines

A non-egg, non-culture based influenza vaccine that intervenes large influenza outbreaks and protects against heterosubtypic infections is needed. Candidates of such vaccine are likely to be conserved influenza virus proteins or their coding DNA. The vaccine must be conveniently produced at reasonable cost, safe, highly immunogenic and should be able to recall rapidly the immunological memory upon the antigenic re-exposure. In this study vaccines made of full length recombinant NP and M2 of the H5N1 influenza A virus were entrapped either alone or together into liposome (L) made of phosphatidylcholine and cholesterol. The vaccines (L-NP, L-M2 or L-NP+M2) and mocks (L or PBS) were safe without causing any adverse reaction in the intramuscularly injected mice. They were readily immunogenic at a single dose and a recalled response could be detected within one day post booster. Cytokine and antibody data indicated that the vaccines induced a Th1 bias immune response. NP containing vaccines stimulated a marked increase of cytotoxic lymphocytes, i.e., CD8(+), intracellular IFNγ(+) cells, while M2 containing vaccines elicited good antibody response which neutralized infectivity of heterologous influenza viruses. Although the three vaccines elicited different immunological defense factors; nevertheless, they similarly and readily abrogated lung histopathology mediated by viruses belonging to different H5N1 clade/subclade and heterosubtypes including swine H1N1 and human H1N1/2009 viruses. They protected the vaccinated mice against lethal challenges with mouse adapted avian H5N1 virus. The liposome adjuvanted vaccines which demonstrated high protective efficacy in mice warrant testing further in a non-rodent model as well as in humans.

Ecologic risk factor investigation of clusters of avian influenza A (H5N1) virus infection in Thailand

This study was conducted to investigate space and time clusters of highly pathogenic avian influenza A (H5N1) virus infection and to determine risk factors at the subdistrict level in Thailand. Highly pathogenic avian influenza A (H5N1) was diagnosed in 1890 poultry flocks located in 953 subdistricts during 2004-2007. The ecologic risk for H5N1 virus infection was assessed on the basis of a spatial-based case-control study involving 824 case subdistricts and 3296 control subdistricts from 6 study periods. Risk factors investigated in clustered areas of H5N1 included human and animal demographic characteristics, poultry production systems, and wild birds and their habitats. Six variables remained statistically significant in the final model: flock density of backyard chickens (odds ratio [OR], 0.98), flock density of fighting cocks (OR, 1.02), low and high human density (OR, 0.60), presence of quail flocks (OR, 1.21), free-grazing duck flocks (OR, 2.17), and a poultry slaughterhouse (OR, 1.33). We observed a strong association between subdistricts with H5N1 virus-infected poultry flocks and evidence of prior and concomitant H5N1 infection in wild birds in the same subdistrict.

Human single chain monoclonal antibody that recognizes matrix protein of heterologous influenza A virus subtypes

Matrix protein (M1) is predominant and has pivotal role in the influenza A virus replication and assembly. It is therefore an attractive target for antiviral drugs, siRNA studies, and therapeutic antibodies. Nevertheless, therapeutic antibody that interferes with the M1 multiplex function has never been developed. In this study, human single monoclonal antibody fragments (HuScFvs) to M1 were generated. Full length recombinant M1 (rM1) was produced from cDNA prepared from genome of highly pathogenic avian influenza virus, A/H5N1. The rM1 was used as an antigen in phage bio-panning to select phage clones displaying HuScFv from a human antibody phage display library. Several phage clones displaying HuScFv bound to the rM1 and harboring the respective huscfv gene inserts were isolated. RFLP experiments revealed multiple DNA banding patterns which indicated epitope/affinity diversity of the HuScFv. The HuScFv were tested for their binding to native M1 of homologous and heterologous influenza A viruses using ELISA as well as incorporating immunostaining and immunofluorescence studies with infected MDCK cells. One such protein produced from a selected phage clone blocked binding of M1 to viral RNA. The HuScFv in their in vivo functional format, e.g. cell-penetrating molecules, should be developed and tested as a broad spectrum anti-A/influenza.

Humanized-monoclonal antibody against heterologous Leptospira infection

Patients with leptospirosis are commonly treated with antibiotics. Jarisch-Herxheimer reaction caused by toxic bacterial substances massively released as a result of the antibiotic mediated-bacterial lysis occurs in some patients which may aggravate the existing severe clinical manifestations. In this study, a humanized-murine single-chain monoclonal antibody (HuScFv) was produced and tested as an alternative of antibiotics for treatment of leptospirosis. Complementary DNA was prepared from total RNA of a murine hybridoma clone secreting monoclonal antibody (MAb) specific to LipL32 of pathogenic Leptospira spp. The MAb had therapeutic efficacy in Leptospira challenged hamsters. The VH and VL coding sequences were amplified using the cDNA as a template. The sequences were linked to form a single-chain variable murine DNA fragment (muscFv). CDR sequences of the muscFv were grafted onto the best matching human VH and VL immunoglobulin frameworks. After cloning of the humanized murine DNA sequences (huscFv) into a phagemid vector and the vector was introduced into competent Escherichia coli, the HuScFv was produced. On the same weight basis, the HuScFv possessed equal neutralizing activities to the murine ScFv counterpart against heterologous Leptospira-mediated hemolysis in vitro and rescued hamsters from a heterologous Leptospira lethal challenge. The HuScFv antibody has high therapeutic potential as an alternative to antibiotics for human leptospirosis, especially for drug hypersensitive patients.

Human single-chain antibodies that neutralize homologous and heterologous strains and clades of influenza A virus subtype H5N1

BACKGROUND

Human antibodies that interfere with the biological activity of haemagglutinins (HAs) of influenza viruses have high potential as an antiviral agent.

METHODS

Human single-chain antibody fragments (HuScFv) to recombinant and native HAs of the influenza virus H5N1 subtype were produced using a human antibody phage display library with the intention to increase the therapeutic arsenal against this highly pathogenic virus.

RESULTS

The HuScFv inhibited HA activity and neutralized infectivity of both homologous and heterologous strains and clades of the H5N1 subtype in Madin-Darby canine kidney cell cultures. Intraperitoneally injected HuScFv also mediated immunotherapeutic protection in mice that were intranasally challenged with highly pathogenic H5N1 viruses belonging to different strains and clades.

CONCLUSIONS

Our data indicate that it might be worth pursuing these HuScFv further for future consideration as candidates for influenza intervention and treatment.

Vasoactive intestinal peptide and its role in continuous and seasonal reproduction in birds

Native Thai chicken, an equatorial species breeds throughout the year, whereas turkeys are seasonal temperate zone breeder whose reproductive cycle is terminated by the onset of photorefractoriness. This study investigated VIPergic activity throughout a reproductive cycle in both species, hypothesizing that the differential expression of vasoactive intestinal peptide (VIP) would provide an insight into the differing reproductive strategies of the two species. Distribution of VIP neurons in the native Thai chicken and a comparison of VIPergic activity in the nucleus inferioris hypothalami (IH) and nucleus infundibuli hypothalami (IN) were investigated. VIP immunoreactivity was found throughout the native Thai chicken brain, predominantly located within the IH-IN. The pattern of VIP distribution in the native Thai chicken supports the findings reported in temperate zone species. Unlike the turkey, where there is a dissociation between VIPergic activity and prolactin levels during photorefractoriness, in the native Thai chicken, which do not express photorefractoriness, changes in VIP immunoreactive (VIP-ir) neurons within the IH-IN were directly correlated with prolactin throughout the reproductive cycle. VIPergic activity reached its lowest level after hatching of the chicks in the native Thai chicken, while in the turkey VIPergic activity was lowest only after exposure to a short day photoperiod and the acquisition of photosensitivity. This suggests that VIP neurons in the IH-IN may play a pivotal role in regulating the reproductive cycle and its differential expression following hatching of the young may, in part, account for the difference in reproductive mode between equatorial, continually breeding, non-photoperiodic birds and seasonally breeding, photoperiodic birds.

The dopaminergic system in the brain of the native Thai chicken, Gallus domesticus: localization and differential expression across the reproductive cycle

Dopamine (DA) has a pivotal role in avian prolactin (PRL) secretion, acting centrally through D(1) DA receptors to stimulate PRL secretion by operating through vasoactive intestinal peptide (VIP). DA also inhibits PRL secretion by activating D(2) DA receptors at the pituitary level. This study was designed to investigate the distribution of DA neurons in the native Thai chicken, utilizing tyrosine hydroxylase (TH) as a marker for dopaminergic neurons. The differential expression of hypothalamic TH immunoreactive (TH-ir) neurons was also compared across the reproductive cycle. The results revealed that TH-ir neurons and fibers were found throughout the brain of the laying hen and were predominantly located within the diencephalon and mesencephalon. The observed distribution pattern of TH immunoreactivity was consistent with that reported previously in several avian species. However, changes in the number of TH-ir neurons in the nucleus intramedialis (nI) were observed across the reproductive cycle and correlated directly with variations in PRL levels. The population of TH-ir neurons in the nI increased significantly during the egg incubation period, where circulating PRL levels were the greatest. This study indicates, for the first time, that an association exists between DA neurons and the regulation of the reproductive system in the native Thai chicken. There is a paucity of information about the reproductive neuroendocrine regulation of tropical non-seasonally breeding avian species and it is suggested that the differential expression of DA neurons in the nI might play a role in the control of VIP secretion and subsequent PRL release in such birds.

Detection of influenza virus types A and B and type A subtypes (H1, H3, and H5) by multiplex polymerase chain reaction

Infections with influenza virus type A and B present serious public health problems on a global scale. However, only influenza A virus has been reported to cause fatal pandemic in many species. To provide suitable clinical management and prevent further virus transmission, efficient and effective clinical diagnosis is essential. Therefore, we developed multiplex PCR assays for detecting influenza types A and B and the subtypes of influenza A virus (H1, H3 and H5). Upon performing multiplex PCR assays with type-specific primer sets, the clearly distinguishable products representing influenza A and B virus were separated by agarose gel electrophoresis. In addition, the subtypes of influenza A virus (H1, H3 and H5), which are most common in humans, can be readily distinguished by PCR with subtype-specific primer sets, yielding PCR products of different sizes depending on which subtype has been amplified. This method was tested on 46 influenza virus positive specimens of avian and mammalian (dog and human) origins collected between 2006 and 2008. The sensitivity of this method, tested against known concentrations of each type and subtype specific plasmid, was established to detect 10(3) copies/microl. The method's specificity was determined by testing against other subtypes of influenza A virus (H2, H4 and H6-H15) and respiratory pathogens commonly found in humans. None of them could be amplified, thus excluding cross reactivity. In conclusion, the multiplex PCR assays developed are advantageous as to rapidity, specificity, and cost effectiveness.

Typing (A/B) and subtyping (H1/H3/H5) of influenza A viruses by multiplex real-time RT-PCR assays

In this study, a specific and sensitive one-step multiplex real-time RT-PCR was developed in two assays by using primers and a number of specific locked nucleic acid (LNA)-mediated TaqMan probes which increase the thermal stability of oligonucleotides. The first assay consisted of primers and probes specific to the matrix (M1) gene of influenza A virus, matrix (M1) gene of influenza B virus and GAPDH gene of host cells for typing of influenza virus and verification by an internal control, respectively. The other assay employed primers and probes specific to the hemagglutinin gene of H1, H3 and H5 subtypes in order to identify the three most prominent subtypes of influenza A capable of infecting humans. The specificity results did not produce any cross reactivity with other respiratory viruses or other subtypes of influenza A viruses (H2, H4 and H6-H15), indicating the high specificity of the primers and probes used. The sensitivity of the assays which depend on the type or subtype being detected was approximately 10 to 10(3)copies/microl that depended on the types or subtypes being detected. Furthermore, the assays demonstrated 100% concordance with 35 specimens infected with influenza A viruses and 34 specimens infected with other respiratory viruses, which were identified by direct nucleotide sequencing. In conclusion, the multiplex real-time RT-PCR assays have proven advantageous in terms of rapidity, specificity and sensitivity for human specimens and thus present a feasible and attractive method for large-scale detection aimed at controlling influenza outbreaks.

Qualitative detection of avian influenza A (H5N1) viruses: a comparative evaluation of four real-time nucleic acid amplification methods

The aim of this study was to determine the performance of real-time amplification based methods - NASBA, TaqMan, RT-FRET, and RT-PCR LUXtrade mark formats - for the detection of influenza A (H5N1) virus RNA. In an analysis of 54 samples obtained from a range of animal species in Thailand during the period 2003-2006, results showed that the NASBA (H5=98.2%, N1=96.3%), TaqMan (H5=98.2%, N1=96.3%) and FRET (H5=98.2%, N1=96.3%) had significantly higher rates of positive detection than LUX (H5=94.4%, N1=50.0%; P<0.001) for influenza A, H5 and N1 isolates. There were no false-positive results from any methods used in the negative-control group of samples. The limits of analytical detection were at least 10copies/reaction in real-time NASBA and LUX assays, while FRET and TaqMan assay appeared to be less sensitive at > or =100copies/reaction. The assays were relatively specific without cross-reactivity to a number of other influenza strains or viral pathogens. In conclusion, our study demonstrated that real-time NASBA, TaqMan and FRET assays can be used to detect influenza A (H5N1) from a wide range of hosts, and be specific for H5N1 samples obtained during different outbreaks (2003-2006). All assays provided the benefit of rapid influenza H5N1 identification for early diagnosis, in the range of hours, and they are well suited to high throughput analyses.

Role of terrestrial wild birds in ecology of influenza A virus (H5N1)

Recent viruses are pathogenic for some small terrestrial bird species.

House sparrows, European starlings, and Carneux pigeons were inoculated with 4 influenza A (H5N1) viruses isolated from different avian species. We monitored viral replication, death after infection, and transmission to uninfected contact birds of the same species. Sparrows were susceptible to severe infection; 66%–100% of birds died within 4–7 days. High levels of virus were detected from oropharyngeal and cloacal swabs and in organs of deceased sparrows. Inoculation of starlings caused no deaths, despite high levels of virus shedding evident in oropharyngeal swabs. Least susceptible were pigeons, which had no deaths and very low levels of virus in oropharyngeal and cloacal swabs. Transmission to contact birds did not occur frequently: only A/common magpie/Hong Kong/645/2006 virus was shown to transmit to 1 starling. In summary, recent influenza (H5N1) viruses are pathogenic for small terrestrial bird species but the rate of intraspecies transmission in these hosts is very low.

Human monoclonal single chain antibodies (HuScFv) that bind to the polymerase proteins of influenza A virus

Current anti-influenza drugs target the viral neuraminidase or inhibit the function of the ion channel M2 protein. Not only is the supply of these drugs unlikely to meet the demand during a large influenza epidemic/ pandemic, but also has an emergence of drug resistant influenza virus variants been documented. Thus a new effective drug or antiviral alternative is required. The influenza virus RNA polymerase complex consists of nucleoproteins (NP) that bind to three polymerase subunits: two basic polymerases, PB1 and PB2, and an acidic polymerase (PA). These proteins play a pivotal role in the virus life cycle; thus they are potential targets for the development of new anti-influenza agents. In this study, we produced human monoclonal antibodies that bound to the influenza A polymerase proteins by using a human antibody phage display library. Complementary DNA was prepared from the total RNA of a highly pathogenic avian influenza (HPAI) virus: A/duck/Thailand/144/2005(H5N1). The cDNA synthesized from the total virus RNA was used as template for the amplification of the gene segments encoding the N-terminal halves of the PB1, PB2 and PA polymerase proteins which encompassed the biologically active portions of the respective proteins. The cDNA amplicons were individually cloned into appropriate vectors and the recombinant vectors were introduced into Escherichia coli bacteria. Transformed E. coli clones were selected, and induced to express the recombinant proteins. Individually purified proteins were used as antigens in bio-panning to select the phage clones displaying specific human monoclonal single chain variable fragments (HuScFv) from a human antibody phage display library constructed from Thai blood donors in our laboratory. The purified HuScFv that bound specifically to the recombinant polymerase proteins were prepared. The inhibitory effects on the biological functions of the respective polymerase proteins should be tested. We envisage the use of the HuScFv in their cell penetrating version (transbodies) as an alternative influenza therapeutic to current anti-virus drugs.

Human single-chain antibodies that neutralize homologous and heterologous strains and clades of influenza a virus subtype H5N1

Background

Human antibodies that interfere with the biological activity of haemagglutinins (HAs) of influenza viruses have high potential as an antiviral agent.

Methods

Human single-chain antibody fragments (HuScFv) to recombinant and native HAs of the influenza virus H5N1 subtype were produced using a human antibody phage display library with the intention to increase the therapeutic arsenal against this highly pathogenic virus.

Results

The HuScFv inhibited HA activity and neutralized infectivity of both homologous and heterologous strains and clades of the H5N1 subtype in Madin–Darby canine kidney cell cultures. Intraperitoneally injected HuScFv also mediated immunotherapeutic protection in mice that were intranasally challenged with highly pathogenic H5N1 viruses belonging to different strains and clades.

Conclusions

Our data indicate that it might be worth pursuing these HuScFv further for future consideration as candidates for influenza intervention and treatment.

Transmission of the highly pathogenic avian influenza virus H5N1 within flocks during the 2004 epidemic in Thailand

This present study is the first to quantify the transmission of avian influenza virus H5N1 within flocks during the 2004 epidemic in Thailand. It uses the flock-level mortality data to estimate the transmission-rate parameter ( beta ) and the basic reproduction number (R(0)). The point estimates of beta varied from 2.26/day (95% confidence interval [CI], 2.01-2.55) for a 1-day infectious period to 0.66/day (95% CI, 0.50-0.87) for a 4-day infectious period, whereas the accompanying R(0) varied from 2.26 (95% CI, 2.01-2.55) to 2.64 (95% CI, 2.02-3.47). Although the point estimates of beta of backyard chickens and fighting cocks raised together were lower than those of laying hens and broiler chickens, this difference was not statistically significant. These results will enable us to assess the control measures in simulation studies. They also indicate that, for the elimination of the virus, a critical proportion of the susceptible poultry population in a flock (i.e., 80% of the population) needs to be vaccinated.

Genetic analysis of influenza A virus (H5N1) derived from domestic cat and dog in Thailand

Complete genome sequences of H5N1 viruses derived from a domestic cat "A/Cat/Thailand/KU-02/04" and dog "A/Dog/Thailand/KU-08/04" were comprehensively analyzed and compared with H5N1 isolates obtained during the 2004 and 2005 outbreaks. Phylogenetic analysis of both cat and dog viruses revealed that they are closely related to the H5N1 viruses recovered from avian influenza outbreaks of the same period. Genetic analysis of 8 viral gene segments showed some evidence of virulence in mammalian species. In summary, the H5N1 viruses that infected a domestic cat and dog are highly pathogenic avian influenza viruses that are virulent in mammalian species, potentially indicating transmission of H5N1 viruses from domestic animals to humans.

Geographic and Temporal Distribution of Highly Pathogenic Avian Influenza A Virus (H5N1) in Thailand, 2004–2005: An Overview

Outbreaks of H5N1 highly pathogenic avian influenza (HPAI) occurred in various types of domestic poultry in Thailand during 2004-05. H5N1 viruses were also detected in humans and other mammalian species. Infections were mainly detected in backyard chickens and domestic ducks. The geographic distribution of the 2004 outbreaks was widespread throughout Thailand; most outbreaks occurred in the Central Region, the southern part of the Northern Region, and the Eastern Region. In 2005, the H5N1 outbreaks continued and showed a clustered pattern in four provinces in the southern part of the Northern Region and in one province in the Central Region. H5N1 HPAI outbreaks caused serious socioeconomic consequences to the poultry industry, the social community, farmers' livelihood, and human health. After key measures were implemented, the incidence of the outbreaks declined remarkably in 2005.

OmpL1 DNA vaccine cross-protects against heterologous Leptospira spp. challenge

Available leptospirosis vaccines made up of inactivated bacteria or their membrane components elicit immunity which is serovar specific and unsatisfactory immunological memory. A vaccine that protects across Leptospira serogroups/serovars, i.e. broad spectrum, and induces long-lasting memory is needed for both human and veterinary uses. In this study, a plasmid DNA vaccine was constructed from cloning gene encoding a transmembrane porin protein, OmpL1, of pathogenic Leptospira interrogans, serogroup Icterohaemorrhagiae, serovar Copenhageni into a mammalian expression vector pcDNA3.1(+). The protective efficacy of the ompL1-pcDNA3.1(+) plasmid DNA vaccine was studied by immunizing hamsters intramuscularly with three doses of the vaccine (100 microg per dose) at two week intervals. The empty pcDNA3.1(+) and PBS were used as mock as negative vaccine controls, respectively. All animals were challenged with the heterologous Leptospira interrogans, serogroup Pomona, serovar Pomona (10 LD50), at one week after the last vaccine booster. The ompL1-pcDNA3.1(+) plasmid DNA vaccine rescued some vaccinated animals from the lethal challenge and delayed death time, reduced morbidity, e.g. fever, and/or the numbers of Leptospira in the tissues of the vaccinated animals. While the results are encouraging, further studies are needed to optimize the immunization schedule, vaccine dosage and formulation in order to maximize the efficacy of the vaccine.

Fatal avian influenza A H5N1 in a dog

Avian influenza H5N1 virus is known to cross the species barrier and infect humans and felines. We report a fatal H5N1 infection in a dog following ingestion of an H5N1-infected duck during an outbreak in Thailand in 2004. With new reports of H5N1 virus continuing across Asia, Europe, and Africa, this finding highlights the need for monitoring of domestic animals during outbreaks.

H5N1 Oseltamivir-resistance detection by real-time PCR using two high sensitivity labeled TaqMan probes

A single amino acid substitution, from histidine to tyrosine at position 274 of the neuraminidase gene has converted Oseltamivir sensitive H5N1 influenza A virus into a resistant strain. Currently, Oseltamivir is being stockpiled in many countries potentially affected by the influenza A virus subtype H5N1 epidemic. To identify this change in Oseltamivir-treated patients, a method based on real-time PCR using two labeled TaqMan probes was developed for its rapid detection. In order to validate the method, Oseltamivir specimen from treated (Oseltamivir-resistant strain from a Vietnamese patient, two Oseltamivir-treated tigers) and untreated subjects have been used for this study. The results thus obtained as well as those derived from clone selection and sequencing showed that TaqMan probes could clearly discriminate wild type H274 from the mutant 274Y variant. The sensitivity of this assay was as low as 10 copies/microl and allowed the detection of the mutation in a mixture of wild type and mutant. Overall, the assay based on real-time PCR with two labeled TaqMan probes described here should be useful for detecting Oseltamivir-resistant H274Y H5N1 influenza A virus in many species and various sources of specimens with high sensitivity and specificity. Such studies can address potential differences in the diagnostic outcomes between patients who develop detectable Oseltamivir resistance and those who retain only the wild type strain of H5N1.

Genetic characterization of influenza A viruses (H5N1) isolated from 3rd wave of Thailand AI outbreaks

Three major outbreaks of avian influenza (AI) occurred in Thailand. During the third episode in October 2005, we have isolated H5N1 viruses from one human case and three poultry cases. The whole genomes of AI viruses from human, chickens and quail from the outbreaks were characterized. Sequence analysis of eight gene segments revealed that the 2005 H5N1 viruses isolated in October 2005 were closely related to those recovered from chicken, tiger(s) and human(s) in January and July 2004. In addition, the genetic changes of the AI isolates at the HA cleavage site have been observed.

The immunogenicity and efficacy against H5N1 challenge of reverse genetics-derived H5N3 influenza vaccine in ducks and chickens

H5N1 avian influenza viruses are continuing to spread in waterfowl in Eurasia and to threaten the health of avian and mammalian species. The possibility that highly pathogenic (HP) H5N1 avian influenza is now endemic in both domestic and migratory birds in Eurasia makes it unlikely that culling alone will control H5N1 influenza. Because ducks are not uniformly killed by HP H5N1 viruses, they are considered a major contributor to virus spread. Here, we describe a reverse genetics-derived high-growth H5N3 strain containing the modified H5 of A/chicken/Vietnam/C58/04, the N3 of A/duck/Germany/1215/73, and the internal genes of A/PR/8/34. One or two doses of inactivated oil emulsion vaccine containing 0.015 to 1.2 microg of HA protein provide highly efficacious protection against lethal H5N1 challenge in ducks; only the two dose regimen has so far been tested in chickens with high protective efficacy.

Avian influenza H5N1 in naturally infected domestic cat

We report H5N1 virus infection in a domestic cat infected by eating a pigeon carcass. The virus isolated from the pigeon and the cat showed the same cluster as the viruses obtained during the outbreak in Thailand. Since cats are common house pets, concern regarding disease transmission to humans exists.

Domestic ducks and H5N1 influenza epidemic, Thailand

In addition to causing 12 human deaths and 17 cases of human infection, the 2004 outbreak of H5N1 influenza virus in Thailand resulted in the death or slaughter of 60 million domestic fowl and the disruption of poultry production and trade. After domestic ducks were recognized as silent carriers of H5N1 influenza virus, government teams went into every village to cull flocks in which virus was detected; these team efforts markedly reduced H5N1 infection. Here we examine the pathobiology and epidemiology of H5N1 influenza virus in the 4 systems of duck raising used in Thailand in 2004. No influenza viruses were detected in ducks raised in "closed" houses with high biosecurity. However, H5N1 influenza virus was prevalent among ducks raised in "open" houses, free-ranging (grazing) ducks, and backyard ducks.

Highly pathogenic avian influenza H5N1, Thailand, 2004

Early detection and control curtail outbreaks.

In January 2004, highly pathogenic avian influenza (HPAI) virus of the H5N1 subtype was first confirmed in poultry and humans in Thailand. Control measures, e.g., culling poultry flocks, restricting poultry movement, and improving hygiene, were implemented. Poultry populations in 1,417 villages in 60 of 76 provinces were affected in 2004. A total of 83% of infected flocks confirmed by laboratories were backyard chickens (56%) or ducks (27%). Outbreaks were concentrated in the Central, the southern part of the Northern, and Eastern Regions of Thailand, which are wetlands, water reservoirs, and dense poultry areas. More than 62 million birds were either killed by HPAI viruses or culled. H5N1 virus from poultry caused 17 human cases and 12 deaths in Thailand; a number of domestic cats, captive tigers, and leopards also died of the H5N1 virus. In 2005, the epidemic is ongoing in Thailand.

Genetic characterization of H5N1 influenza A viruses isolated from zoo tigers in Thailand

The H5N1 avian influenza virus outbreak among zoo tigers in mid-October 2004, with 45 animals dead, indicated that the avian influenza virus could cause lethal infection in a large mammalian species apart from humans. In this outbreak investigation, six H5N1 isolates were identified and two isolates (A/Tiger/Thailand/CU-T3/04 and A/Tiger/Thailand/CU-T7/04) were selected for whole genome analysis. Phylogenetic analysis of the 8 gene segments showed that the viruses clustered within the lineage of H5N1 avian isolates from Thailand and Vietnam. The hemagglutinin (HA) gene of the viruses displayed polybasic amino acids at the cleavage site, identical to those of the 2004 H5N1 isolates, which by definition are highly pathogenic avian influenza (HPAI). In addition, sequence analyses revealed that the viruses isolated from tigers harbored few genetic changes compared with the viruses having infected chicken, humans, tigers and a leopard isolated from the early 2004 H5N1 outbreaks. Sequence analyses also showed that the tiger H5N1 isolated in October 2004 was more closely related to the chicken H5N1 isolated in July than that from January. Interestingly, all the 6 tiger H5N1 isolates contained a lysine substitution at position 627 of the PB2 protein similar to the human, but distinct from the original avian isolates.

Probable tiger-to-tiger transmission of avian influenza H5N1

During the second outbreak of avian influenza H5N1 in Thailand, probable horizontal transmission among tigers was demonstrated in the tiger zoo. Sequencing and phylogenetic analysis of those viruses showed no differences from the first isolate obtained in January 2004. This finding has implications for influenza virus epidemiology and pathogenicity in mammals.

Pasteurella multocida–Associated Sinusitis in Khaki Campbell Ducks (Anas platyrhynchos)

Pasteurella multocida group B, serotype 3, was isolated from sinusitis-affected khaki Campbell ducks. To study the role of P. multocida in sinusitis, commercial khaki Campbell ducks were experimentally infected with P. multocida alone or combined with Escherichia coli. In Expt. 1, experimental ducks were infected with P. multocida intranasally or ocularly. A comparison was done by intranasal inoculation with pooled nasal discharge from the affected ducks or phosphate-buffered saline. The ducks intranasally inoculated with the nasal discharge or P. multocida showed sinusitis. In Expt. 2, E. coli alone or a combination of P. multocida and E. coli was intranasally inoculated into experimental ducks. The ducks intranasally inoculated with the combination of P. multocida and E. coli had sinusitis, the same as found in the field but less severe than that of the field cases. Pasteurella multocida was already present in litter/floor of duck farms. We concluded that P. multocida played a role in induction of sinusitis. However, the sinusitis in ducks may be initiated by poor management, especially in the brooding period of ducks.

Enteropathogenicity of Dutch and German avian reoviruses in SPF white leghorn chickens and broilers

The enteropathogenicity of avian reoviruses (ARVs), isolated from chickens affected with malabsorption syndrome (MAS) from The Netherlands and Germany was studied. In the first trial seven different ARVs isolated from MAS cases were inoculated in 1-day-old specific pathogenic free (SPF) white leghorns. The pathogenicity was compared with 2 ARVs isolated from cases of tenosynovitis, namely reference strain S1133 and a Dutch strain. Although a difference in the severity of the clinical disease was observed, all reoviruses could induce vacuolar degeneration and sloughing of the epithelium of the small intestine at day 2 post inoculation (PI) till day 7 PI. Two Dutch and one German ARV derived from MAS causing the most severe intestinal lesions at day 2 PI, were further studied in the second trial using SPF broilers. These reoviruses did not cause weight gain depression in the broilers although lesions in the small intestine were present from day 1 up to day 4 PI and were more severe than in the white leghorn chickens. In one of the inoculated groups apical denuded villi were already present at day 1 PI. At day 7 PI the small intestine of the infected broilers appeared to be normal. Reovirus antigen was detected in the cytoplasm of the enterocytes at the tip and middle section of the affected villi both in layers and in broilers. To study the role of intestinal CD4+ and CD8+ T-cells and macrophages/monocytes in the pathogenesis of ARV, the numbers of these cells of the jejunal villi of one infected and the control broiler groups were compared. CD4+ T-cells were detected in low numbers and only in the infected broiler group at day 14 PI. The numbers of CD8+ T-cells and macrophages/monocytes were significantly higher in the infected broiler group than in the control broiler group at day 7 and 14 PI and at day 7 PI respectively. Our study indicates that the reovirus alone cannot induce intestinal lesions as found in MAS chickens. Moreover, CD8+ T-cells may play a major role in the pathogenesis and or reovirus clearance in the small intestine.

Development of organs and intestinal mucosa leukocytes in four broiler lines that differ in susceptibility to malabsorption syndrome

Growth retardation in young broiler chicks due to poor nutrient metabolism, commonly known as malabsorption syndrome (MAS), is a widespread problem caused by enteric infections with a combination of pathogens mainly viruses. Genetic lines of broiler chickens differ in susceptibility to the syndrome. A difference in growth retardation was observed among four broiler lines (BL) after oral inoculation at 1 d of age with intestinal homogenates obtained from MAS-affected birds. Two of the lines that are more susceptible to MAS had severe weight gain depression. To uncover the factors that play a role in the susceptibility to MAS, we analyzed the growth rate of the body and vital organs and the quantity of leukocytes in the peripheral blood and intestinal mucosa. The development of the intestine, liver, bursa of Fabricius, and spleen was similar among the BL. The resistant BL had higher numbers of peripheral blood leukocytes, especially lymphocytes, at 1 d of age. A significant difference was noted in the numbers of CD4+ T cells and CD8+ T cells in the intestinal villi. At the ages of 3 and 8 d, the susceptible BL had more CD8+ T cells in the villi, whereas the ratios of CD4+:CD8+ T cells were higher in the resistant BL. This difference in the number of T-cell subpopulations in the intestinal mucosa might be an important factor in the difference in susceptibility to the enteric infections associated with MAS.

A comparative study of the pathogenesis of malabsorption syndrome in broilers

Five malabsorption syndrome (MAS) homogenates from The Netherlands and Germany were used to reproduce MAS in broilers. We studied the histopathology after inoculation of 1-day-old broiler chicks and the agents that might be involved. Generally, the MAS homogenates induced signs that differed in severity and pathobiology. We could distinguish and classify the inoculated groups best by histopathology: proventriculitis, lesions in the small intestines in combination with proventriculitis, or lesions of the small intestines only. Lesions in the small intestine had more impact on weight gain depression than lesions in the proventriculus. In three out of five inoculated groups, microscopic lesions of the pancreas were found. Reovirus was detected in the inoculated groups by virus isolation and seroconversion, and reoviral antigen was detected by immunohistochemistry of the small intestine. Also, enteroviruslike particles were detected in three of the five inoculated groups, although not in the most affected group. Additionally, bacteriophages and bacteria (hemolytic Escherichia coli, Pasteurella hemolytica, and Enterococcus durans) were isolated from inoculated chicks. The role these agents play in pathogenesis of MAS is still unsolved.