Effect of cyclophosphamide on the growth of Rickettsia sennetsu in experimentally infected mice

Characterization of Ehrlichia species from Ixodes ovatus ticks at the foot of Mt. Fuji, Japan

A total of 390 adult ticks (288 Ixodes ovatus and 102 I. persulcatus ) collected at the foot of Mt. Fuji and two near cities in Shizuoka prefecture, Japan, were examined for Ehrlichia infection by isolation with laboratory mice from whole tick tissues. Ehrlichial DNAs were detected from the spleens of mice inoculated with tissues from I. ovatus, but not I. persulcatus. The prevalence of ehrlichiae in the ticks was estimated to be ca. 3%. The 16S rDNA analysis revealed that the sequences of 8 ehrlichial isolates (termed "Shizuoka" isolates) obtained were identical, and they were very similar, but not identical, to those of two Ehrlichia species strain variants recently isolated in Japan, followed by Ehrlichia chaffeensis in the US. Analysis of parts of the omp-1 multigene family specific for monocytic ehrlichiosis agents showed that the Shizuoka isolates were distinct from other ehrlichial organisms. The Shizuoka isolates caused death in immunocompetent laboratory mice, suggesting that they are highly pathogenic in mice. The data show that the Shizuoka isolates are likely to be a new strain variant of Ehrlichia species in Japan. Further characterization and surveillance will be required in Japan due to the presence of these human ehrlichiosis agent-like organisms.

Colitis: differential diagnosis and treatment

Equine colitis characterised by diarrhoea and/or pain may be caused by a wide variety of bacterial, viral, protozoal agents and toxins. The causative agent of Potomac horse fever, Ehrlichia risticii, is the most recently recognised cause of colitis. Salmonella, the agent typically associated with colitis, also causes abdominal pain (colic) of variable intensity. Acute colitis is also caused by colitis X, various antibiotics, endotoxic shock and peritonitis caused by arterial infarction. The principles of therapy for each of these, together with means of differential diagnosis, are presented.

Serodiagnosis of tsutsugamushi fever (scrub typhus) by the indirect immunoperoxidase technique

The indirect immunoperoxidase technique was assessed for the serodiagnosis of tsutsugamushi fever (scrub typhus). The antigens were peritoneal smears prepared from mice infected intraperitoneally with the Karp, Kato, and Gilliam strains of Rickettsia tsutsugamushi. Treatment of the mice with cyclophosphamide apparently increased the number of the rickettsiae, and it minimized the exudate that interfered with the specific staining. The rickettsiae were seen as clusters in the juxtanuclear region of the mesothelial cells and also as free particles outside of the cells. By the indirect immunoperoxidase technique, the sera from all of the patients (49 samples from 30 patients) were positive for the R. tsutsugamushi antibody. The antibody titers (immunoglobulin G [IgG] and IgM) determined by the indirect immunoperoxidase technique correlated with those determined by the indirect immunofluorescence technique. Thus, the indirect immunoperoxidase technique was useful for quantifying both IgG and IgM antibodies to the rickettsia.

Acute experimental canine ehrlichiosis. II. Sequential reaction of the hemic and lymphoreticular system of selectively immunosuppressed dogs

The lymphoreticular response of dogs to Ehrlichia canis infection was studied after immunosuppressive therapy with cyclophosphamide or antilymphocyte serum. Immunosuppression did not increase mortality, nor did it prevent or significantly modify the clinical manifestations of acute ehrlichiosis. The clinical, hematologic and serum biochemical characteristics of acute ehrlichiosis appeared seven or more days later in immunosuppressed than in immunologically intact infected dogs. Immunosuppressive therapy generally attenuated the lesions of acute ehrlichiosis. Lymphoreticular tissues were partially depleted of lymphocytes, as would be expected following cyclophosphamide therapy, but the hemopoietic tissue of cyclophosphamide-treated principals was much more cellular than that of the controls, perhaps demonstrating a direct stimulatory effect E. canis infection on bone marrow. Antilymphocyte serum therapy reduced cellularity of the thymic-dependent areas in both the spleen and lymph nodes, but B-cell areas were not affected. The B-cell areas did not increase in activity during infection in the antilymphocyte serum-treated dogs, suggesting the need for an intact T-cell compartment for the lymphocytic proliferation that occurs in nonsuppressed infected dogs. Renal vasculitis and lympho-plasmacytosis were absent and the pulmonary and hepatic lesions were not as pronounced in the dogs given antilymphocyte serum as in immunologically competent infected dogs.

Modulation of delayed-type hypersensitivity and cellular immunity to microbial vaccines: effects of cyclophosphamide on the immune response to tularemia vaccine

Treatment of guinea pigs with cyclophosphamide before immunization with killed tularemia vaccine in Freund incomplete adjuvant produced a prolongation and intensification of delayed-type hypersensitivity and in vitro lymphocyte transformation reactions to tularemia antigen. Such reactions resemble those ordinarily associated with the administration of live tularemia vaccine, killed vaccine in Freund complete adjuvant, or recovery from natural infection. The immunopotentiation lasted longer than that seen previously in other antigenic systems with this drug and was dependent on the dose of vaccine used. More intense delayed skin reactivity could be transferred into normal controls by cells from immunized donors pretreated with cyclophosphamide than by cells from immunized donors that were not pretreated.

Susceptibility of mice treated with cyclophosphamide to lethal infection with Leptospira interrogans Serovar pomona

Mice not normally susceptible to infection with Leptospira interrogans serovar pomona were rendered susceptible to lethal infections by treatment with a single dose of 300 mg of cyclophosphamide (Cy) per kg administered optimally from 4 days before to 1 day after infection. Cy-treated mice with either passively or actively acquired antibody were protected from death. Blood levels of leptospires in infected untreated and in Cy-treated mice remained similar until 2 days after infection, when untreated mice cleared the leptospires. Soon afterwards, opsonizing and agglutinating antibody appeared. Cy-treated mice given spleen cells from other normal or specifically immune mice were protected from infection. An important factor in the natural resistance of mice to leptospiral infection appears to be their capacity to produce circulating antibody within 48 to 72 h. Applications are suggested for this animal model in vaccination and protection studies.

Purification of complement-fixing antigens of Rickettsia sennetsu by ether treatment

Soluble and particulate complement-fixing antigens of Rickettsia sennetsu were prepared from spleen suspensions of mice infected with the rickettsia and treated with cyclophosphamide. The medium used during purification of antigens, a solution consisting of equal volumes of phosphate-glutamate-sucrose buffer and veronal-buffered saline, was suitable for obtaining antigens with high titers and no anti-complementary activity. By heat treatment, it was demonstrated that the soluble antigen was heat labile and the particulate antigen was heat stable. The soluble antigen was precipitated by 80% saturation with ammonium sulfate. Cross-complement fixation tests using both soluble and particulate antigens revealed that there was no antigenic difference among strains of R. Sennetsu. On the other hand, no cross-activity was observed between R. sennetsu and R. orientalis.