Small Indian mongooses and masked palm civets serve as new reservoirs of Bartonella henselae and potential sources of infection for humans

The prevalence and genetic properties of Bartonella species were investigated in small Indian mongooses and masked palm civets in Japan. Bartonella henselae, the causative agent of cat-scratch disease (CSD) was isolated from 15.9% (10/63) of the mongooses and 2.0% (1/50) of the masked palm civets, respectively. The bacteraemic level ranged from 3.0 × 10¹ to 8.9 × 10³ CFU/mL in mongooses and was 7.0 × 10³ CFU/mL in the masked palm civet. Multispacer typing (MST) analysis based on nine intergenic spacers resulted in the detection of five MST genotypes (MSTs 8, 14, 37, 58 and 59) for the isolates, which grouped in lineage 1 with MST genotypes of isolates from all CSD patients and most of the cats in Japan. It was also found that MST14 from the mongoose strains was the predominant genotype of cat and human strains. This is the first report on the isolation of B. henselae from small Indian mongooses and masked palm civets. The data obtained in the present study suggest that these animals serve as new reservoirs for B. henselae, and may play a role as potential sources of human infection.

Prevalence of Bartonella species and 16s rRNA gene types of Bartonella henselae from domestic cats in Thailand

Prevalence of Bartonella infection among 275 cats in 9 sites from 4 geographical regions (northern area: Chiang Mai; central area: Kanchanaburi, Ratchaburi, and Bangkok; northeastern area: Khon Kaen, Roi Et, Ubon Ratcharthani, and Nakhonratchasima; southern area: Songkhla) of Thailand was investigated. Overall, Bartonella species were isolated from 27.6% (76 of 275) of the cats. The isolation rate varied from 12.8% (5 of 39) in Songkhla (southern area) to 50.0% (26 of 52) in Khon Kaen (northeastern area). Bartonella henselae and B. clarridgeiae were isolated from 82.9% (63 of 76) and 11.8% (9 of 76) of the Bartonella-positive cats, respectively. Coinfection with both species was found in 5.3% (4 of 76) of the bacteremic cats. Of the 67 bacteremic cats from which B. henselae was isolated, 48 (71.6%) and 13 (19.4%) were infected with only Type I and Type II, respectively. Coinfection with both types was observed in 9.0% (6 of 67) of the B. henselae-positive cats. To our knowledge, this is the first report on the presence of Bartonella infection in domestic cats from Thailand, which constitute a large reservoir of Bartonella infection in this country.

Tumor necrosis factor alpha and its receptors in experimentally bovine leukemia virus-infected sheep

To examine whether tumor necrosis factor alpha (TNF alpha) contributes to the pathogenesis of bovine leukemia virus (BLV) infection, the mRNA expression patterns of TNF alpha and its receptors, type 1 (TNF R1) and type 2 (TNF R2) were investigated. Sheep inoculated with BLV were divided into two groups; one was BLV-positive and the other BLV-negative based on the detection in peripheral blood mononuclear cells (PBMC). Expression of TNF R1 mRNA was down-regulated in PBMC from the BLV-positive compared to BLV-negative sheep. No difference was shown in the expression levels of TNF R2 mRNA between the two groups. Furthermore, proliferative responses of PBMC in the presence of TNF alpha were observed from the BLV-positive, but not BLV-negative sheep. Membrane-bound TNF alpha (mTNF alpha) is thought to be one of the ligands, inducing B-cell activation. Flow cytometric analysis demonstrated that the number of PBMC, that were positive for mTNF alpha expression, was increased in the BLV-positive sheep. Thus, the expression of TNF alpha and its receptors may be closely associated with lymphocytosis induced by BLV.

Host immune responses in the course of bovine leukemia virus infection

Bovine leukemia virus (BLV) is a type C retrovirus infecting bovine B cells and causing enzootic bovine leukosis. Since it takes long periods to develop the disease, it is believed that BLV and host immune responses are closely related. In this review, the accumulated data showing close relationship between BLV and host immune responses are summarized in 4 sections. First, we discuss the role of cell-mediated immunity in protecting hosts from BLV infection. Second, several reports showing the relationship between the disease progression and the change of cytokine profiles are summarized. In the third section, we have focused on tumor necrosis factor alpha (TNFalpha) and its two types of receptors, and the possible involvement of TNFalpha in the BLV-induced leukemogenesis is discussed. The expression of TNFalpha has been shown to be regulated by major histocompatibility complex (MHC) haplotype. The resistance to BLV infection is supposed to be established by some innate factors, which are closely related to MHC haplotype. Finally, we propose that a breeding strategy based on the MHC haplotype could be a good approach to control BLV infection. This review includes some recent data from us and other groups.

Three cases of cat scratch disease diagnosed by indirect immunofluorescence antibody assay and/or polymerase chain reaction of 16S rRNA gene of Bartonella henselae

Three suspected cases of cat scratch disease were diagnosed by indirect immunofluorescence antibody assay and/or polymerase chain reaction. Patient 1 was a 10-year-old female who presented swelling of the right axillary [corrected] lymph nodes with pain and fever. She kept a kitten, and many scratches were observed on her both legs and dorsum manus. Antibody titers against Bartonella (B.) henselae were 1:32 for IgM 3 weeks after the onset of the symptoms and 1:64 for IgG 8 weeks after the onset. The DNA for 16S rRNA type I of B. henselae was detected from the blood sample obtained 3 weeks after the onset of symptoms by polymerase chain reaction for the first time in Japan. Patient 2 was a 22-year-old female veterinary student with a cat scratch at the bottom of her neck by a male kitten. She developed a papule at the scratch, slight fever, and neck pain. Although both Bartonella-specific IgG and IgM antibodies were negative before the scratch, the IgG antibody titer rose to 1:512 14 weeks after the onset. B. henselae was isolated from the kitten and its DNA found to be for 16S rRNA type I by PCR. Patient 3 was a 23-year-old female veterinary student with a cat scratch on her left forearm. A small reddish papule developed on the scratch, and she experienced swelling of the left axillary [corrected] lymph node and pain. Both the IgG and IgM antibodies against B. henselae were negative before the cat scratch, and the IgG titer rose significantly to 1:128 and 1:1,024 in 2 and 5 weeks, respectively, after the onset of the symptoms.

Seroprevalence of Bartonella henselae and Toxoplasma gondii among healthy individuals in Thailand

The seroprevalence of Bartonella henselae and Toxoplasma gondii among apparently healthy individuals, mainly blood donors, in Thailand was investigated by an indirect fluorescent antibody technique and by a latex agglutination test, respectively. Of 163 serum samples examined, 9 (5.5%) were found to be positive for B. henselae-IgG, 2 (1.2%) for B. henselae-IgM, and 5 (3.1%) for the T. gondii antibody. No significant difference was observed between male and female samples in the serological test with either B. henselae or T. gondii. The age of individuals with B. henselae-IgG was distributed from the 20s to the 70s, and B. henselae-IgM was found in the individuals of the 30s and 60s. The age of T. gondii positive samples ranged from the 20s to the 60s. In this study, the prevalence of B. henselae infection among healthy individuals in Thailand was serologically demonstrated for the first time.

Prevalence of Bartonella henselae, Bartonella clarridgeiae and the 16S rRNA gene types of Bartonella henselae among pet cats in Japan

The authors investigated bacteriologically the prevalence of Bartonella infection among 690 pet cats derived from 10 private animal hospitals in six cities (Sapporo, Hokkaido Prefecture; Sendai, Miyagi Prefecture; Joetsu, Niigata Prefecture; Fujisawa, Kanagawa Prefecutre; Kyoto, Kyoto Prefecture; Sanda, Hyogo Prefecutre) and 4 counties (Mishima, Osaka Prefecture; Hikawa, Shimane Prefecture; Aira, Kagoshima Prefecture; Shimajiri, Okinawa Prefecture) located from the north to the south of Japan. Bartonella species were isolated from 7.2% (50/690) of all the cats examined. No Bartonella species were isolated from the cats in Sapporo or Sendai. The isolation rate varied from 2% in Joetsu and Sanda to 20% in Shimajiri. Bartonella clarridgeiae was isolated from two of 50 cats in Kyoto, three of 50 in Mishima and one of 50 in Shimajiri, but not in cats from the other cities or counties. Though the cats of Joetsu, Fujisawa, Kyoto, Sanda, Aira and Shimajiri were infected with either B. henselae or B. clarridgeiae, one of eight infected cats in Mishima was harboring both Bartonella species. Type I of 16S rRNA gene was the predominant type among the isolates of B. henselae, but only one isolate derived from Shimajiri was found to be of type II. Prevalence of B. clarridgeiae and the 16S rRNA gene type of B. henselae among cats in Japan was demonstrated for the first time in this investigation.

Up-regulation of tumor necrosis factor alpha mRNA is associated with bovine-leukemia virus (BLV) elimination in the early phase of infection

Protective immune responses were analyzed in eight sheep vaccinated with BLV envelope peptides and experimentally infected with bovine-leukemia virus (BLV). Five of eight peptide-immunized sheep showed a high T-cell proliferative response to the BLV peptides and all of these were protected from the infection. The other three peptide-immunized sheep showed no T-cell proliferative responses to any BLV antigens similar to control sheep, though they also exhibited resistance to BLV challenge. To investigate other mechanisms which suppress BLV expansion in these non-responding sheep, we measured the levels of the cytokine expressions before, and after, BLV challenge using competitive reverse-transcriptase polymerase chain-reaction systems. It was revealed that the expression of tumor necrosis factor alpha (TNFalpha) was higher in BLV-resistant sheep than in BLV-susceptible sheep. Thus, TNFalpha expression rather than specific T-cell activity may play an important role in the protective mechanism against BLV infection, at least during the primary viremia phase.

Characterization of immune responses caused by bovine leukemia virus envelope peptides in sheep

To study the immunomodulative activity caused by bovine leukemia virus envelope (BLV Env) peptide, sheep were immunized with two kinds of Th-epitope peptides, peptide 98 (BLV Env 98-117), and 61 (BLV Env 61-78). Four of eight immunized sheep showed specific proliferative responses against both of the peptide stimulations. To characterize the cells responding to the peptides, peptide-specific cells were established from the responding sheep by the continuous stimulation of peripheral blood mononuclear cells (PBMCs) with either peptide 98 or 61 in vitro. The peptide 98-specific cells consisted of CD4-positive cells, whereas the peptide 61-specific cells consisted of CD8-positive cells and MHC class II-positive cells. In addition, cytokine profile analysis indicated that the peptide 98-stimulated cells expressed IFN-gamma but not IL-10, although the peptide 61-stimulated cells expressed IL-10 but not IFN-gamma. These results show that BLV envelope peptides 98 and 61 can modulate immune responses of sheep lymphocytes in different ways and may contribute to the pathogenesis of BLV infection.

Bovine leukaemia virus envelope peptides cause immunomodulation in BALB/c mice

Immunomodulatory activity of two bovine leukaemia virus envelope (BLVEnv) derived peptides were examined in BALB/c mice. One is peptide homologous to CKS-17 which is known as a 17-amino acid peptide derived from p15E of feline leukaemia virus (CKS-17/BLV), and the other is an 18-amino acid synthetic peptide of BLV Env 61-78 (pep61). Priming with CKS-17/BLV in vitro, as well as CKS-17, significantly suppressed the mitogen-induced proliferative responses of spleen cells in naive BALB/c mice. In addition, priming of spleen cells with pep61 in vitro and in vivo resulted in suppression of lipopolysaccaride-induced B-cell proliferative response. This suppression was partially due to the basic amino acid sequence in the peptide because if the pep61-derived peptide lacking Arg was used, this inhibitory activity was partially restored. In contrast, pep61 enhanced both concanavalin A-stimulated proliferative response and IL-2 production. These findings showed that pep61 may contribute to the modification of the host immune responses in the course of BLV infection.

Ovine MHC class II DRB1 alleles associated with resistance or susceptibility to development of bovine leukemia virus-induced ovine lymphoma

For the further characterization of bovine leukemia virus (BLV)-induced leukemogenesis, we investigated the association between polymorphism of ovine leukocyte antigen (OLA)-DRB1 gene and tumor development after infection of sheep with BLV. We infected 28 sheep with BLV and cloned exon 2 of the OLA-DRB1 gene from asymptomatic animals and from animals with lymphoma Sequence analysis revealed that, among 12 healthy sheep without any evidence of tumor, ten (83.3%) carried DRB1 alleles encoding Arg-Lys (RK) at positions beta70/71 as compared with only 6 (37.5%) of the 16 sheep with lymphoma, which suggested that alleles encoding the RK motif might protect against development of tumors after infection by BLV. By contrast, alleles encoding Ser-Arg (SR) at positions beta70/71 were present at a significantly elevated frequency in sheep with lymphoma as compared with the healthy carriers, which indicated that OLA-DRB1 alleles encoding the SR motif might be positively related to susceptibility to tumor development. The two amino acids in these motifs line a pocket that accommodates the side chain of a bound peptide according to a model of the crystal structure of human leukocyte antigen (HLA)-DR1. To analyze immunoreactions of sheep with alleles that encoded RK or SR at beta70/71, we selected sheep with either the RK/SR genotypes or the SR/SR genotypes and immunized them with a mixture of multiple synthetic antigenic peptides that corresponded to T-helper, T-cytotoxic, and B-cell epitopes of the BLV envelope glycoprotein gp51. Two weeks after the last immunization, all of the sheep were challenged with BLV. Sheep with the RK/SR genotype produced neutralizing antibodies against BLV; they eliminated BLV completely within 28 weeks of the BLV challenge, and they gave strong lymphocyte-proliferative responses to the peptides used for immunization. Moreover, such animals did not develop lymphoma. By contrast, sheep with the SR/SR genotype continued to produce BLV throughout the experimental period and developed terminal disease. Our results indicate that the differences in immunoresponse were due to differences in major histocompatibility complex class II alleles and reflected the risk of BLV-induced leukemogenesis. In addition, it appears that susceptibility to tumor development may be determined to some extent by polymorphic residues binding to antigenic peptides directly within the binding cleft of the OLA-DR molecule.

Seroprevalence and field isolation of bovine immunodeficiency virus

A seroprevalence study of bovine lentivirus, known as bovine immunodeficiency virus (BIV), was conducted in 12 different dairy herds in Hokkaido, where some herds were a high prevalence of bovine leukemia virus (BLV) infection. Amongst 611 cattle, 28.6% of cattle were BLV-seropositive, and 11.7% of cattle were seropositive for BIV, while 4.2% of cattle were seropositive for both BIV and BLV. For the isolation of BIV, 19 samples of peripheral blood mononuclear cells (PBMC) and one sample of milk-derived leukocytes were prepared from BIV-seropositive cows. These PBMC and leukocyte preparations were then co-cultivated with cc81 cells, a cat cell line transformed by mouse sarcoma virus. BIV was isolated from 17 PBMC and one milk-derived leukocyte samples. The isolated viruses showed slow replication and syncytia formation. Major core antigen, p26 from these isolates were reacted with anti-BIV (American isolate R-29) serum. In addition, proviral DNA was detected in blood and milk samples by nested polymerase chain reaction and subsequent Southern blot hybridization. Nucleotide sequence analysis of the amplified pol gene products showed its 99.0 to 99.7% homology to that of BIV R-29. These results indicate that the Japanese BIV isolates appear to be antigenically and genetically similar to the American R-29. Since BIV was isolated from milk samples, BIV could possibly be transmitted through milk. This is the first report of BIV isolation in Japan.

Epitope mapping of bovine leukemia virus transactivator protein Tax

The immunogenicity of the bovine leukemia virus (BLV) transactivator protein (tax) was studied by mapping its B-cell and T-cell epitopes. Peptides (18 to 20-mer) overlapping by 10 amino acids, spanning whole amino acid sequence of BLVtax were synthesized. Recombinant BLVtax protein was used to immunize two different strains of mice, C57BL/6 and BALB/c. B-cell and T-cell epitopes of recombinant BLVtax protein was determined by screening all the 30 synthetic peptides, against immune serum in ELISA for antibody reactivity, and against immune spleen cells in lymphocyte proliferation assay for T-cell stimulation. Peptides with amino acids at position 111-130 and 131-150 were T-cell epitopes for C57BL/6 and BALB/c mice immune cells, respectively. B-cell epitope was mapped to amino acid sequence at 261-280 in both strains of mice. These results imply that BLVtax protein contains some of BLV- immunodominant epitopes and this information may be applied for designing an effective peptide vaccine capable of inducing neutralizing antibodies as well as cellular immunity.

Control of Theileria sergenti infection by vaccination

Bovine piroplasmosis caused by Theileria sergenti is a major cause of economic loss in grazing cattle in Japan. Infected calves show chronic anaemia with intraerythrocytic piroplasms and occasionally die in severe cases. We found that parasite stocks and isolates consist of genetically and antigenically mixed populations. To differentiate parasite populations bearing 3 allelic forms of p32/34, an immunodominant piroplasm surface protein, 3 sets of oligonucleotide primers were designed to amplify either of 3 alleles by polymerase chain reaction (PCR). By using this allele-specific PCR, we found that the majority of T. sergenti-infected calves in Japan harbored mixed parasite populations bearing C and I type parasites. To control Theileria infection, we produced 2 vaccine candidates: recombinant baculovirus p32 and synthetic peptide containing Lys-Glu-Lys (KEK) motif. Immunization with either recombinant p32 or synthetic peptide containing KEK sequences with Freund's complete adjuvant resulted in low parasitemia and reduced the clinical symptoms compared to control calves. Interestingly, the parasite with the p32 allelic form corresponding to the one used as the immunogen was suppressed.

Peptide-based bovine leukemia virus (BLV) vaccine that induces BLV-Env specific Th-1 type immunity

In controlling retrovirus infection and replication, cell-mediated immunity (CMI) is considered to be effective. To develop a synthetic peptide vaccine capable of inducing CMI, mannan-coated liposome encapsulating 20-mer synthetic peptide, spanning the 98-117 amino acids of bovine leukemia virus (BLV) envelope glycoprotein (Env) gp51 was constructed and inoculated to BALB/c mice. The liposome induced specific delayed-type hypersensitivity, lymphocyte proliferative responses, and a weak cytotoxic lymphocyte response. The spleen cells from the immunized mice produced a large amount of IFN-gamma and IL-2, whereas they released neither IL-4 or IL-10. Mannan-coated liposome containing two kinds of peptides (the 121-140 and 142-161 regions of BLV Env gp51) also induced peptide-specific lymphocyte proliferative response and IFN-g production in C57BL/6 mice. Thus, the synthetic T-cell epitope peptide-liposome system augmented a strong Th-1 type immunity in mice.

Immunomodulative effects of bovine immunodeficiency-like virus (BIV)-infection and mixed infection of BIV and bovine leukemia virus on sheep

Experimental bovine immunodeficiency-like virus (BIV)-infection and mixed infection of BIV and bovine leukemia virus (BLV) were performed on sheep. BIV proviral DNA and anti-BIV antibodies were persistently detected in all BIV-inoculated sheep. A slight increase in lymphocyte counts was observed in BIV-infected sheep, but the percentages of CD4+ and CD8+ cells in sheep peripheral blood mononuclear cells (PBMCs) were not significantly changed. A transient decrease in lymphocyte blastogenic response to concanavalin. A was observed in two of three BIV-infected sheep at 3-6 months after inoculation. From 6 months after BLV-inoculation to sheep which were previously infected with BIV, the numbers of lymphocytes expressing a tumor-associated antigen (TAA) of bovine leukosis were increased compared to those of a sheep inoculated with BLV alone. The BLV titers in PBMCs and the antibody titers against BLV from sheep infected with both BIV and BLV were higher than those of a sheep inoculated with BLV alone.

An effective peptide vaccine to eliminate bovine leukaemia virus (BLV) infected cells in carrier sheep

Protective effects of the gp51 of bovine leukaemia virus (BLV) expressed by a recombinant baculovirus (rgp51) and synthetic multiple antigenic peptides (MAP) of T-helper, T-cytotoxic, and B-cell epitopes of gp51 were investigated against BLV challenge. Two and three sheep were immunized with rgp51 and a mixture of peptides with Freund's complete adjuvant, respectively. BLV was detected from all the immunized sheep at 2 weeks and showed peak levels at 4 weeks after the challenge. However, in two sheep immunized with the mixed peptides, the titer of BLV gradually decreased and one sheep eliminated BLV completely at 28 weeks after the challenge. These two sheep showed higher lymphocyte proliferative responses against the immunized peptides than the other sheep. One of the sheep also showed the specific cytotoxic lymphocyte activity against the BLV gp51-expressing target in vitro. These results suggest the possibility of the peptide vaccine for elimination of BLV in carrier animals in vivo.

Induction of bovine leukaemia virus Env-specific Th-1 type immunity in mice by vaccination with short synthesized peptide-liposome

Cell-mediated immunity (CMI) is considered to be effective in controlling retrovirus infection and replication. To develop a peptide-based vaccine capable of inducing CMI, mannan-coated liposome encapsulating 20-mer synthetic peptide, spanning the 98-117 amino acids of bovine leukaemia virus (BLV) envelope glycoprotein (Env) gp51 was constructed. The liposome induced specific delayed-type hypersensitivity, lymphocyte proliferative responses and a weak cytotoxic lymphocyte response in mice. By stimulation with the peptide and BLV virion, the spleen cells from the immunized mice produced a large amount of IFN-gamma and IL-2, whereas they released neither IL-4 or IL-10. These results indicate the augmentation of Th-1 type immunity in mice by the T-cell epitope synthetic peptide-liposome.

Detection of antibodies against bovine immunodeficiency-like virus in daily cattle in Hokkaido

Serological survey of bovine immunodeficiency-like virus (BIV) infection was performed in cattle of 3 different farms in Hokkaido, where a relatively high seroprevalence was recorded for bovine leukemia virus (BLV). About a half of 120 cattle tested were seropositive for BLV, while 7.5% of the cattle were seropositive for BIV. Though increased numbers of leukocytes were frequently observed in BLV-seropositive cows, no such changes were observed in BIV-positive but BLV-negative cows. No correlation was demonstrated between BIV- and BLV-seroprevalence of the cattle.