Characterization of the first Bartonella henselae strain isolated from a cat in Italy

Bartonella henselae has been identified and characterized for the first time in Italy. A strain, designed Pavia-1, was isolated from the blood of a cat whose owner developed cat scratch disease (CSD). Pavia-1 and two American B. henselae strains (Houston-1, ATCC 49882, type I and strain 269608, UC Davis, type II) were compared by whole-cell fatty analysis (CFA), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) for protein profiles, Western immunoblotting (WB) for reactivity with polyclonal antibodies, polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), type-specific 16S rRNA PCRs, and pulsed-field gel electrophoresis (PFGE). Bartonella clarridgeiae (ATCC 51734) was also included for comparison. Pavia-1 was identified as a B. henselae type I. PFGE allowed differentiation between B. clarridgeiae and B. henselae and furthermore, between all the B. henselae strains. The fingerprints of PFGE observed for Pavia-1 were distinct from those of B. henselae type II and also of Houston-1, suggesting that the two type I strains derived from two different clones. These results show the capability of B. henselae to develop genotypic variability between genetically related strains.     

Immune responses of immunocompetent and immunocompromised mice experimentally infected with Bartonella henselae

The aim of this study is to understand host immune responses in immunocompetent and immunocompromised mice against Bartonella henselae infection. BALB/c and nude (BALB/c nu/nu) mice were inoculated intraperitoneally with 10(8) colony forming units of B. henselae (Houston-1 strain). Blood, brain, liver, spleen, kidney and bone marrow samples were collected 0, 3, 7, 14, 21 and 28 days after infection and submitted to bacteriological, serological and genetical examinations. B. henselae was isolated only from the liver 3 days after infection. DNA of the inoculums was detected by polymerase chain reaction from blood, liver, and spleen samples collected from BALB/c and blood from nude mice 3 and 7 days after infection. No bacterial DNA was detected from both BALB/c and nude mice thereafter during 4 weeks observation periods. These results indicate that the T-cell may not participate in the effective elimination of the organisms from mice. In addition, western blot analysis revealed that the antigens of 27.3- and 31.5-kDa reacted with IgM antibodies from the blood of BALB/c and nude mice after 3 days of infection, suggesting that these antigens were recognized by thymus-independent mechanism. Furthermore the antigens were detected from the culture-supernatants of B. henselae, indicating that these antigens were secreted from the organisms.     

Isolation of Bartonella henselae from a serologically negative cat in Bloemfontein, South Africa

Sera collected from apparently healthy 6-12-month-old cats (n = 31) presented to the Society for the Prevention of Cruelty to Animals Veterinary Clinic in Bloemfontein for neutering were tested for antibodies reactive to Bartonella henselae (Houston-1 strain) by indirect fluorescent antibody testing. Whole blood collected from the cats was used in isolation experiments and subsequent identification of Bartonella species was based on comparison of the nucleotide base sequence of polymerase chain reaction-amplified citrate synthase gene fragments. While none of the cats had antibodies reactive with B. henselae at titres > or =1/64, an organism with a partial citrate synthase gene sequence identical to that of B. henselae (Houston-1) was isolated from 1 cat.     

Characterization of Th1 activation by Bartonella henselae stimulation in BALB/c mice: Inhibitory activities of interleukin-10 for the production of interferon-gamma in spleen cells

This study was conducted to analyze cytokine production mechanisms in mice after Bartonella henselae stimulation. BALB/c mice were inoculated intraperitoneally with 3 x 10(6) colony forming units of B. henselae (Houston-1 strain) twice at 10-day interval. Spleen cells were harvested from the mice and stimulated with the organisms. Following the stimulation, interferon-gamma (IFN-gamma) and interleukin-4 (IL-4), IL-10, IL-12 and tumor necrosis factor-alpha (TNF-alpha) were measured in the culture supernatants of the spleen cells by ELISA. The spleen cells specifically secreted IFN-gamma, but not IL-4, indicating that T helper 1 (Th1) cells were activated following B. henselae stimulation. In addition, IL-10 and TNF-alpha productions were also detected in the culture supernatants of spleen cells. Neutralization of IL-10 in the culture supernatants significantly enhanced the production of IFN-gamma from the spleen cells stimulated with B. henselae. These results indicate that B. henselae predominantly stimulated Th1 cells and resulted in secreting IFN-gamma, however the production was partially inhibited by IL-10, which was produced simultaneously.     

Experimental infection of specific pathogen free (SPF) cats with two different strains of bartonella henselae type I: a comparative study

Domestic cats are the reservoir of Bartonella henselae, the main causative agent of cat scratch disease. We compared B. henselae type I infection characteristics in 6 SPF cats infected with a feline strain (4.8 x 10(7) colony-forming units (CFU)/mL) and in 6 SPF cats infected with the reference Houston I strain (6.6 x 10(6) CFU/mL to 9.6 x 10(7) /mL). All the cats inoculated with the feline strain, but none of the cats inoculated with B. henselae Houston I, developed a fever within 2-12 days (mean: 5.8 days) post inoculation (PI), which lasted for 1-2 weeks. However, all 12 cats became bacteremic. The duration of bacteremia was significantly longer in the cats inoculated with the feline strain (mean: 237 days) than in the cats inoculated with Houston I strain (mean: 60 days) (p < 0.01). Five (83%) cats inoculated with the feline strain and none of the six cats inoculated with B. henselae Houston I had relapsing bacteremia (p = 0.02). IgG antibodies were detected by IFA within 1-2 weeks for both strains, but peaked later (week 10 versus week 3 PI) for the feline strain. By ELISA, using antigens of each B. henselae strain, all 12 cats developed Bartonella specific IgM and IgG antibodies, but the cats infected with B. henselae Houston I antigen yielded significantly lower optical density values (p < 0.05). By SDS-PAGE, PFGE and Western blotting, protein profile differences (84 to 89% homology) were observed between the two strains. If a feline vaccine is to be developed in order to prevent human infection, the choice of the vaccine strain will be critical, since major differences were identified even between strains belonging to the same sero/genotype.     

Evaluation and use of a nested polymerase chain reaction assay in cats experimentally infected with Bartonella henselae genotype I and Bartonella henselae genotype II.

Cats have been shown to be infected with Bartonella henselae genotype I, B. henselae genotype II, and B. clarridgeiae. Feline bartonellosis infections and the strains involved in these infections are important in both veterinary and human medicine. Nucleic acid amplification methods such as polymerase chain reaction (PCR) are being used in both research and diagnostics as tools for understanding many infectious diseases. Bartonella bacteremia in cats is detected by blood culture; however, because of the limitations of culture (delayed turnaround time and sensitivity limits), PCR may be a more efficient method for identifying infected cats. Three distinct PCR assays that could differentiate among B. henselae genotype I, B. henselae genotype II. and B. clarridgeiae were developed and used to detect as few as 3.2 organisms. Fourteen cats experimentally infected with B. henselae genotype I and B. henselae genotype II were followed by bacterial culture and PCR through the course of infection, including periods of primary and relapsing bacteremia. The PCR assay was positive in 11 of the 14 cats for periods of 1-9 weeks after culture became negative. Of the 223 blood specimens that were culture negative, the PCR assay was positive in 38 (17%) of the specimens. Two of the 14 cats developed relapsing bacteremia. The 2 B. henselae genotypes were amplified in the cats and the bacteremic phase of these infections as determined by PCR lasted for a longer period than previously determined by culture. Using laboratory assays such as PCR to understand the strains involved in feline bartonellosis and the course of the infection is important in the understanding of these zoonotic agents.     

Cat-scratch disease in veterinary-associated populations and in its cat reservoir in Taiwan

In Taiwan, the first human case of cat-scratch disease (CSD) was diagnosed by a serologic test in 1998. Since then, no studies have been conducted to understand the epidemiology of the infection in Taiwan. Therefore, this study is the first epidemiologic survey of CSD in cats and humans in this country. Using veterinary-associated individuals as the study population, it was identified that 1.7% of them were seropositive for B. henselae, and residence was the only factor associated with seropositivity. Bartonella species were successfully isolated from 25 (19.1%) of the 131 cats tested. Only B. henselae and B. clarridgeiae were obtained from bacteremic cats. Furthermore, 9.2% of 131 cats were dually-infected with genotypes I and II of B. henselae. It is the highest prevalence of co-infection that has ever been reported worldwide. In cats, the seroprevalence was 23.7% by indirect immunofluorescence antibody assay with B. henselae Houston-1 (type I) as the antigen. When 12 bacteremic but seronegative cats were re-tested by IFA slides coated with B. henselae U-4 antigen (type II), 9 cats were identified to be seropositive. Our study further suggested that using only direct PCR of 16S-23S rRNA intergenic region or the combination of the PCR method and indirect immuno-fluorescence test will be useful to diagnose Bartonella-free cats.     

Experimental infection of domestic cats with passaged genotype I Bartonella henselae

The influence of in vitro passage on Bartonella henselae pathogenesis in cats has not been thoroughly evaluated. Our objective was to examine the bacterial kinetics and humoral immune responses in cats experimentally infected with three different in vitro passages of B. henselae F1, a genotype I strain of feline origin. The F1 strain was in vitro passaged 20 and 40 times, and each was inoculated into a group of 5 cats. The kinetics of bacteremia and the feline humoral immune response to bacterial antigens were compared to a previous study involving a group of six cats inoculated with the original F1 strain. Among the three groups of cats, the kinetics of bacteremia profiles and the humoral immune responses to B. henselae lysates were similar. The influence of passage on bacterial membrane proteins was examined. In vitro passage altered the expression of 4/17 (23.5%) bacterial membrane proteins and 6/15 (40%) bacterial membrane antigens. An association between poor seroreactivity to three lysate antigens (15-, 18- and 45kDa), prolonged bacteremia and decreased serum bactericidal activity was noted. Our data show that in vitro passage of B. henselae did not alter the kinetics of bacteremia, including the occurrence of relapsing bacteremia, in experimentally infected cats. This suggests that highly passaged strains may not be suitable for future vaccination studies. Furthermore, in vitro passage results in phenotypic and antigenic changes in the bacterial membrane protein profile, which warrants caution in the interpretation of studies involving passaged B. henselae strains.     

牛结节性皮肤病病毒感染MDBK细胞后转录组差异表达分析

旨在探索牛结节性皮肤病病毒（lumpy skin disease virus,LSDV）与宿主细胞的相互作用,采集了具有典型临床症状的牛皮肤病变组织,接种MDBK细胞进行病毒分离,采用透射电镜观察病变组织及病毒感染后的MDBK细胞,同时对感染后24 h的MDBK细胞进行转录组学分析,筛选差异表达基因并将其按功能分类,分析它们参与的细胞信号通路。结果显示,LSDV在电镜下呈椭圆形,病毒粒子大小约320 nm×260 nm。转录组分析发现,与未处理组相比,显著差异表达的基因共499个,其中,112个基因上调表达,387个基因下调表达。通过GO和KEGG分析得知,差异表达基因主要富集在从细胞表面传导信号至细胞核内部的MAPK信号通路,其中,参与天然免疫且涉及细胞凋亡的MAP3K1基因表达呈现显著下调,提示病毒感染会影响宿主细胞的迁移与凋亡等过程。显著变化基因包括HIF1A、RORA、LRRK2、AP3B1和ANO6等,分别涉及到调节血管内皮生长因子、炎症反应、细胞增殖分化以及信号转导等功能,除此之外,不饱和脂肪酸及胆汁分泌两个信号通路也发生了显著变化。本研究为进一步深入探究LSDV的致病机制奠定了基础。     

Modulation of host immune responses by protozoal DNA

The pathology caused by acute Babesia bovis infection is similar to that seen in severe human malaria caused by Plasmodium falciparum infection, which is related to dysregulated production of inflammatory cytokines and nitric oxide (NO). We have observed induction of NO, inducible nitric oxide synthase (iNOS) and inflammatory cytokines in macrophages by B. bovis. Furthermore, proliferation of lymphocytes from individuals never exposed to certain protozoal pathogens can be induced by crude protozoal parasite extracts. We have repeatedly observed stimulation of naive PBMC from cattle to antigenic extracts of Babesia bovis. Based on recent studies demonstrating the mitogenicity of bacterial and other non-vertebrate DNAs for murine B cells and macrophages, the mitogenic properties of B. bovis DNA were examined. B. bovis and E. coli DNAs induced proliferation of PBMC and purified B cells from non-exposed cattle. Stimulatory activity was reduced by DNase treatment and methylation with CpG methylase, indicating the presence of stimulatory non-methylated CpG motifs in the B. bovis genome. B. bovis and E. coli DNAs enhanced IgG secretion by cultured B cells, stimulating IgG1 and more strongly, IgG2. Several hexameric CpG immunostimulatory sequences (ISS) active for murine B cells were identified in an 11 kb fragment of B. bovis DNA. An oligodeoxyribonucleotide containing one of these (AACGTT), located in the rhoptry associated protein-1 (rap-1) open reading frame, stimulated B cell proliferation. These studies identify a potential mechanism by which protozoal parasites may modulate host immune responses, leading to consequences such as hypergammaglobulinemia and splenomegaly. These results also support the use of ISS as vaccine adjuvants to enhance Type 1 immune responses in cattle.     

Adherence of Streptococcus suis to porcine endothelial cells

Streptococcus suis can cause invasive diseases in pigs and humans, such as meningitis or arthritis. Adherence to and invasion of endothelial cells might represent important steps in survival and spread of S. suis within the host. We tested in vitro adherence and invasion of S. suis strains using a porcine brain microvascular and aortal endothelial cell line. Four S. suis strains were tested with and without prior treatment with porcine serum containing anti-S. suis antibodies. Strains included a capsular serotype 2 strain and its non-encapsulated isogenic mutant strain, as well as two non-typeable (NT) strains, which expressed no capsule under our experimental conditions. Strains adhered to both cell lines to different extents depending on encapsulation and pre-treatment with porcine immune serum. The serotype 2 strain showed almost no adherence, whereas the non-encapsulated mutant strain adhered strongly. Similarly, both NT strains adhered substantially better than the serotype 2 strain. Pre-treatment of bacteria with porcine serum increased adherence of the encapsulated serotype 2 strain and decreased adherence of the non-encapsulated strains. None of the strains was able to efficiently invade either of the two cell lines, except for one NT strain, which showed a very low extend of invasion. Our results suggest that S. suis can adhere to but not invade porcine endothelial cells, and that this interaction may involve different bacterial surface structures, such as capsular polysaccharides and/or binding sites for serum components.     

Phagolysosome maturation of macrophages was reduced by PE_PGRS 62 protein expressing in Mycobacterium smegmatis and induced in IFN-γ priming

Mycobacterium bovis parasitizes host macrophages and has developed strategies to survive within macrophages. Research on mycobacteria-specific PE_PGRS genes indicates that they code for cell surface proteins that may influence virulence. To further elucidate the molecular pathogenesis of tuberculosis and host response to M. bovis, we explored the mechanisms by which PE_PGRS62 protein increase persistence of mycobacterium within host macrophages. We found that the M. smegmatis strain expressing M. bovis PE_PGRS 62 protein reduced phagolysosome maturation in human macrophages, and significantly decreased the mRNA expression of IL-1β in a dose- and time-dependent. We identified that IFN-γ priming of macrophages immediately prior to infection with PE_PGRS62 expressing M. smegmantis, enhanced the maturation of phagolysosomes and induced IL-1β production both that the protein and mRNA levels and further activated the NF-κB pathway. Overall, we demonstrated that PE_PGRS62 protein altered the immune environment of the host cells, which suggested that the pathogenic PE_PGRS62 protein altering the immune mechanism might be involved in the pathogenesis of mycobacterial disease and hence influenced host cell responses to M. bovis infection.     

Factors involved in the early pathogenesis of bovine Staphylococcus aureus mastitis with emphasis on bacterial adhesion and invasion. A review

Staphylococcus aureus is the most important and prevalent contagious mammary pathogen; it causes clinical and subclinical intramammary infection with serious economic loss and herd management problems in dairy cows. In vitro studies have shown that Staphylococcus aureus adheres to mammary epithelial cells and extracellular matrix components and invades into mammary epithelial as well as other mammary cells. Staphylococcus aureus strains from intramammary infection produce several cell surface-associated and extracellular secretory products. The exact pathogenic roles of most of the products and their effects on adhesion and invasion are not well evaluated. It is also known that mammary epithelial cell-associated molecules and extracellular matrix components interact with S. aureus during the pathogenesis of mastitis, but their roles on adhesion and invasion have not been characterized. The adhesion of S. aureus to epithelial cells may involve non-specific physicochemical interactions and/or specific interactions between bacterial cell-associated ligands and host cell surface receptors. In vitro adhesion depends on the S. aureus strain, the growth phase of the bacteria, the growth medium and the origin of the epithelial cells. Adhesion is hypothesized to be a prerequisite and crucial early step for mammary gland infection. Staphylococcus aureus invades mammary epithelial cells. It also invades other cells such as endothelial cells and fibroblasts. Bacteria are found enclosed in membrane bound vacuoles in the cytoplasm of mammary epithelial cells. Recent observations indicate that S. aureus escapes from the phagosome into the cytoplasm and induces apoptosis. The invasion into mammary epithelial cells may occur through an endocytic process that requires involvement of elements of the cytoskeleton or by direct binding of bacteria to epithelial cells through a process mediated by specific receptors that needs de novo protein synthesis by both cells. Thus, the recurrent subclinical infection may result from this intracellular existence of bacteria that are protected from host defenses and effects of antibiotics. This review emphasizes on recent findings on S. aureus adhesion to mammary epithelial cells and extracellular matrix components and invasion into mammary epithelial cells.     

Differential detection of Bartonella species and strains in cat scratch disease diagnostics by polymerase chain reaction amplification of 16S ribosomal RNA gene.

Cat scratch disease (CSD) has been difficult to diagnose in animals because of the protracted clinical course of infection and the quiescent phases when the microbial culprit lies dormant. The causative agent in CSD appears to be multiple species and strains of Bartonella. Using polymerase chain reaction (PCR) techniques for amplification of highly variable regions of the 16S ribosomal RNA (rRNA) gene sequence, a very sensitive species- and strain-specific assay for CSD-causing Bartonella species was developed. PCR primers were designed to specifically amplify the 16S rRNA gene of Bartonella species but not of other microbial pathogens. This initial PCR was multiplexed with a universal primer set, based on conserved sequence regions in the 16S rRNA gene, that provides a 162-bp fragment in all species tested. Subsequently, 3 distinct nested PCR primer sets enabled the individual amplification and specific detection of Bartonella henselae type 1, B. henselae type II, and B. clarridgeae. Thus, this 2-step PCR procedure enabled the sensitive detection and identification of these species and the B. henselae genotype by exploiting minor sequences differences. Verification of these results were demonstrated with both sequencing and ligase chain reaction techniques. The diagnostic usefulness of this CSD test has been demonstrated by the analysis of specimens from control and infected cats. The diagnosis was confirmed and the specific B. henselae strain was correctly identified in peripheral blood specimens obtained from control and strain-specific CSD-infected cats. Such an accurate and sensitive diagnostic tool for the detection and identification of CSD causative agents should be a useful for the medical, veterinary, and scientific communities.     

Immunological parameters in goats experimentally infected with SRLV genotype E, strain Roccaverano

Genotype E of small ruminant lentivirus has been recently described in goats from different breeds in Italy. Genotype E infection may differ from known genotypes since deletions of dUTPase and VPR proteins have been confirmed in different independent areas and goat breed, and play a key role on virus replication and pathogenesis. In particular, genotype E Roccaverano strain has been described as low pathogenic since does not lead to clinical symptoms in goats. In contrast, classical CAEV infected goats of the same area and breed presented arthritis. In this study, we have used intratracheal and intra-bone marrow routes to establish genotype E persistent infections. Humoral and cellular immune responses elicited in the host against genotype E and genotype B derived antigens were evaluated until 200 days post-inoculation. Compared to genotype B antigen, seroconversion against genotype E GAG P16-25 antigen was detected at 2-3 weeks after inoculation, significantly earlier and at higher titres. Interestingly, antibody avidity did not increase in the course of the experiment neither against P16-25 nor against SU5, both derived from genotype E. T cell proliferation against P25-GST fusion protein antigens derived from genotype E was firstly detected at 15 days post-inoculation and was maintained throughout time until week 20 post-infection, while T cell proliferation against the genotype B P25 was not produced by the end of the experiment at 20 weeks post-inoculation. The strength of reaction was also higher when using P25 E as stimulator antigen. In contrast with antibody and T cell proliferation, cytotoxic-T-lymphocyte (CTL) activity in the circulating lymphocytes (effector cells) using blood-derived macrophages (BDM) as target cells, was not strain specific being surprisingly higher against genotype B infected antigen presenting cells (APCs). This is the first study reporting experimentally induced immunological changes in SRLV genotype E infection and indicates that CTL activity may be the adaptive immune response able to induce protection against heterologous infection.     

IbeB is involved in the invasion and pathogenicity of avian pathogenic Escherichia coli

The ibeB gene in neonatal meningitis Escherichia coli (NMEC) contribute to the penetration of human brain microvascular endothelial cells (HBMECs). However, whether IbeB plays a role in avian pathogenic E. coli (APEC) infection remains unclear. Thus, this study was conducted to investigate the distribution of the ibeB gene in Chinese APEC strains and examine whether IbeB is involved in APEC pathogenicity. The ibeB gene was found in all 100 detected E. coli isolates with over 97% sequence homology. These results indicated that ibeB is a conserved E. coli gene irrelevant of pathotypes. To determine the role of ibeB in APEC pathogenicity, an ibeB mutant of strain DE205B was constructed and characterized. The inactivation of ibeB resulted in reduced invasion capacity towards DF-1 cells and defective virulence in animal models as compared to the wild-type strain. Animal infection experiments revealed that loss of ibeB decreased APEC colonization and invasion capacity in brains and lungs. These virulence-related phenotypes were partially recoverable by genetic complementation. Reduced expression levels of invasion- and adhesion-associated genes in ibeB mutant could be major reasons as evidenced by reduced ibeA and ompA expression. These results indicate that IbeB is involved in APEC invasion and pathogenicity.     

Clinical disease in kittens inoculated with a pathogenic strain of Bartonella henselae

OBJECTIVE: To evaluate disease in kittens inoculated with Bartonella henselae strain LSU16. ANIMALS: Eighteen 12-week-old specific-pathogen-free kittens. PROCEDURE: Kittens were inoculated with B henselae strain LSU16 or saline (0.9% NaCl) solution. Blood samples were collected from kittens on alternate weeks, and bacteremia, clinical signs, and antibody concentrations were monitored for 6 months after inoculation. RESULTS: Kittens developed raised, erythematous areas at the site of inoculation within 72 hours. Swelling peaked at 14 days and resolved by 28 days after inoculation. Fever had a biphasic pattern, with an episode of 1- to 3-days' duration beginning 6 to 7 days after inoculation followed by an episode of 3- to 8-days' duration beginning 11 to 13 days after inoculation. Kittens were bacteremic by day 14 with peak bacteremia at days 14 to 28. Strong antibody responses to B henselae were detected. Clinical disease resolved before bacteremia became undetectable, but signs of disease correlated with the highest degree of bacteremia. Regional lymphadenopathy also was evident. CONCLUSION AND CLINICAL RELEVANCE: Clinical disease in kittens was similar to that in adult cats infected with B henselae strain LSU16, except that lethargy and anorexia were less severe in kittens, and a biphasic pattern of fever was detected in kittens. Clinical disease after inoculation with B henselae may be strain-dependent. To limit transmission of Bartonella organisms, appropriate flea prevention should be instituted. IMPACT FOR HUMAN MEDICINE: Kittens that are febrile, anorectic, lethargic, and that have lymphadenopathy should be tested for Bartonella organisms, and contact with immunocompromised owners should be discouraged.     

Molecular and biological characterization of vascular endothelial growth factor of parapoxviruses isolated from wild Japanese serows (Capricornis crispus)

Contagious dermatitis in domestic and wild ruminants caused by parapoxvirus (PPV) occurs worldwide. Although PPV infections appear in cattle, sheep and goats, the papular, nodular, pustular and ulcerated skin lesions of wild Japanese serows (Capricornis crispus) are significantly more severe than those of other animals. To determine the factors involved in the severity of these skin lesions, we compared the molecular characteristics of 4 PPV isolates from Japanese serows and 2 isolates from sheep in Japan, and also investigated the biological properties of primary endothelial cells from different host species. All of the 6 Japanese isolates harbored a vascular endothelial growth factor (VEGF) gene, which is known as one of the virulence factors of PPVs. Three different amino acid sequences of viral VEGF were identified and the sequence was identical among the 4 isolates from the Japanese serows. The temporal expression pattern of viral VEGF mRNA was almost the same among 3 isolates encoding the 3 different VEGFs in infected cells from different host species. Recombinant forms of the 3 different VEGFs showed the ability to induce vascular permeability and endothelial cell proliferation. Primary endothelial cells from Japanese serows were most responsive to recombinant viral VEGF compared to cells from cattle, sheep, and goats. These results suggest that not only the biological activity of viral VEGF but also the high responsiveness to viral VEGF of endothelial cells might be involved in the severe proliferative skin lesions induced by PPV infection in Japanese serows.     

Differences in the tissue tropism to chicken oviduct epithelial cells between avian coronavirus IBV strains QX and B1648 are not related to the sialic acid binding properties of their spike proteins

The avian coronavirus (AvCoV) infectious bronchitis virus (IBV) is a major poultry pathogen. A characteristic feature of IBV is the occurrence of many different strains belonging to different serotypes, which makes a complete control of the disease by vaccinations a challenging task. Reasons for differences in the tissue tropism and pathogenicity between IBV strains, e.g. a predilection for the kidneys or the oviduct are still an open question. Strains of the QX genotype have been major pathogens in poultry flocks in Asia, Europe and other parts of the world. They are the cause of severe problems with kidney disease and reproductive tract disorders. We analysed infectivity and binding properties of the QX strain and compared them with those of the nephropathogenic strain B1648. As most IBV strains do not infect permanent cell lines and show infection only in primary chicken cells of the target organs, we developed a culture system for chicken oviduct explants. The epithelial cells of the oviduct showed a high susceptibility to infection by the QX strain and were almost resistant to infection by the nephropathogenic B1648 strain. Binding tests with isolated primary oviduct epithelial cells and soluble S1 proteins revealed that S1 proteins of two IBV strains bound with the same efficiency to oviduct epithelial cells. This attachment was sialic acid dependent, indicating that the sugar binding property of IBV spike proteins is not the limiting factor for differences in infection efficiency for the oviduct of the corresponding viruses.