Leptospira interrogans serovar grippotyphosa infection in dogs.

Leptospirosis attributed to infection with serovar grippotyphosa was diagnosed in 11 dogs. In naturally and experimentally infected dogs, a stereotypic serologic response to infection with Leptospira serovar grippotyphosa was detected. Although the highest serum antibody titers developed against serovar grippotyphosa, most dogs also had lower titers against serovars bratislava and pomona. Acute renal failure was evident in 10 dogs. One dog died prior to initiation of treatment; the remaining 10 dogs were treated with antibiotics and fluids. Two dogs were euthanatized, 2 dogs recovered without clinical or biochemical evidence of residual renal dysfunction, and 6 dogs recovered but had varying degrees of renal insufficiency. Hepatic involvement appeared to be a minor component of the disease in these dogs. Our results indicate that Leptospira serovar grippotyphosa infection is an important problem in dogs and should be considered when evaluating a dog with renal failure.

An oligonucleotide probe that distinguishes isolates of low virulence from the more pathogenic strains of Newcastle disease virus.

A synthesized oligonucleotide, termed cleavage probe (NDV-CL), has been designed to complement the cleavage-activation site of the fusion gene of the Texas GB isolate of Newcastle disease virus (NDV). This oligonucleotide probe, 21 bases in length, bound with RNA from velogenic strains of NDV tested in a slot-blot hybridization assay. The probe also recognized RNA from the mesogenic strains used in this assay, although no signal was observed with RNA isolated from lentogenic NDVs or with that from other common avian viruses used as controls. This probe did not recognize RNA from isolates of other paramyxovirus serotypes (PMV-2 or PMV-3) included in this study. The ability of this probe to distinguish lentogenic NDVs, which cause little or no clinical disease, from those strains that may produce severe morbidity and/or mortality suggests a potential use for the probe in a molecular diagnostic assay.

A novel oligonucleotide probe for the detection of Newcastle disease virus.

An approach that possesses high specificity and broad applicability was used to obtain a DNA probe with potential diagnostic value. By utilizing synthesized oligonucleotide DNA, termed NDV probe, all 14 strains of NDV tested under high-stringency conditions were recognized in a slot-blot hybridization assay. The sequence of the NDV probe was generated from a highly conserved region of the NDV genome. No hybridization was observed with RNA isolated from other avian viruses, including avian influenza, infectious bursal disease, and infectious bronchitis. The specificity inherent in using an oligonucleotide probe offers advantages over probes obtained from cloned DNA fragments.

Antithymocyte serum suppression of immunity in mice immunized to Leishmania donovani.

Mice immunized with a glucan-killed parasite vaccine exhibited enhanced resistance to Leishmania donovani infection as evidenced by decreased hepatic parasite burdens when compared to unvaccinated controls. This resistance was not seen in mice immunized with killed parasites alone. Glucan vaccination resulted in increased resistance at day 6, but this effect was no longer present by day 20 of the experiment. Treatment of vaccinated and control mice with antithymocyte sera abrogated protection against infection, whether such resistance was vaccine induced or the result of acquired immunity.

Trichomonas vaginalis: preliminary characterization of a sperm motility inhibiting factor.

This study determined the effects of Trichomonas vaginalis trophozoites, subcellular fractions, and medium from axenic T. vaginalis cultures on human sperm motility and viability. Spent medium (pH 7.0) caused complete cessation of sperm motility after 15 minutes incubation. Trophozoite soluble fraction or formalin-killed trophozoites caused a 50 percent reduction in sperm motility, compared to 25 percent reduction caused by the trophozoite particulate fraction or the sterile medium and three percent by saline (control). Spent medium from T. vaginalis cultures reaching stationary growth phase produced the greatest reduction in sperm motility, suggesting that potency was related to time in culture and trophozoites per ml. The T. vaginalis spermicidal activity was heat-stable, trypsin-sensitive, and had a molecular weight of 12-15,000 by gel filtration. This proteinaceous substance was present in and secreted by T. vaginalis trophozoites during normal growth in axenic culture. Since this T. vaginalis byproduct rapidly killed sperm in vitro, its effects in humans may contribute to infertility in infected couples.

Resistance against Leishmania donovani induced with an aluminum hydroxide vaccine.

Mice immunized with a subcutaneous protocol combining killed parasites and aluminum hydroxide gel exhibited significant resistance against subsequent challenge with Leishmania donovani promastigotes. Protection was greatest using 25 mg of aluminum hydroxide per injection. Resistance elicited by this killed parasite and aluminum hydroxide protocol was as effective on day 14 as that provided by immunization with a glucan and killed parasite preparation, and more effective in hepatic amastigote reduction at day 28. The effectiveness of aluminum hydroxide as an adjuvant appears to result, at least in part, from its ability to activate macrophages, thus aiding in the elimination of this intracellular parasite.

Leishmania donovani: immunization against infection as a function of parasite growth phase.

C57BL/6 mice were immunized against Leishmania donovani infection with a subcutaneous vaccination protocol. Groups received 3 injections at 4-day intervals combining glucan and killed promastigotes harvested from either logarithmic or stationary phase cultures. Controls were immunized with glucan alone, stationary or log phase promastigotes alone, or were untreated. All groups were challenged intravenously with stationary phase promastigotes at day 45 post-immunization. Results revealed that animals immunized with the glucan-killed parasite vaccine, utilizing promastigotes derived from either log (GPL) or stationary phase cultures (GPS), demonstrated significant resistance against infection as compared to controls or untreated mice. Additionally, the reduction in hepatic amastigote proliferation in mice immunized with GPS was significantly greater than in mice immunized with GPL.

Effect of hydroxyethyl starch (HES) in reducing parasite load in experimental visceral leishmaniasis.

Leishmania donovani primarily infects phagocytic cells of the reticuloendothelial system. Hydroxyethyl starch (HES) has been shown to concentrate transiently in these organs. The effect of HES administration was assessed upon infection and also upon vaccination against this parasite. Animals received HES intraperitoneally thrice weekly, either alone (HES) or with a subcutaneous immunization protocol utilizing aluminum hydroxide and killed parasites (ALP-HES). Controls were untreated (NT) or received only the vaccination protocol (ALP). Results showed that animals treated with HES alone exhibited significantly fewer parasites as compared to untreated animals (p less than 0.001). The ALP animals also were protected against infection but demonstrated greater parasite burdens than HES animals. Immunized animals which also received HES demonstrated infection levels similar to those treated with HES alone, thus negating any synergistic effect. The reason for increased protection against L. donovani infection in animals treated with HES is not clear, but it may result from a transient increase in host resistance.

Adoptive transfer of vaccine-induced resistance to Leishmania donovani.

BALB/c mice were immunized with three subcutaneous injections combining killed parasites and glucan, or were untreated. Spleen cells were transferred to syngeneic recipients. Mice which received 5 X 10(8) spleen cells from vaccinated donors demonstrated significant protection against Leishmania donovani challenge as compared to untreated mice receiving immune sera, or mice which received untreated spleen cells.

The effect of BCG-vaccine upon experimental visceral leishmaniasis in hamsters.

Stimulation with Bacillus Calmette-Guerin (BCG) vaccine has been reported to enhance resistance of mice against Leishmania donovani infection. Such infection is usually lethal in hamsters, thus providing a more stringent animal model to assess the effect of BCG upon visceral leishmaniasis. Animals receive two IP injections (2-8 X 10(7) BCG) pre or post IC challenge with 4 X 10(6) amastigotes. Controls received BCG alone (with no infection) or were untreated (NT). Pretreated animals exhibited significantly fewer (P less than 0.05) hepatic or splenic amastigotes than NT animals at days 7, 14, and 28 post challenge, but most BCG treated hamsters died earlier than NT. Post treated hamsters showed no significant reduction in parasite burdens, or in median time to death as compared to NT group. Hamsters which received BCG but were not infected appeared healthy during the study. The reason for increased susceptibility of BCG-treated hamsters to disease is not clear, but observed pathologic complications of L. donovani infected hamsters appear to be exacerbated by BCG stimulation.