Immune response in mice infected by Encephalitozoon cuniculi and suppressed by dexamethasone

Several indicators of immune response were observed in immunocompetent mice of the ICR line and those suppressed by dexamethasone upon their experimental infection with the microsporidia of Encephalitozoon cuniculi. The mice were infected by one-shot intraperitoneal administration of 5 x 10(7) pathogenic spores. On Days 7, 14, 28 and 42 after infection, peripheral blood leukocyte phagocytic activity was determined and compared, including phagocytic index and the blastogenic response in spleen cells to mitogenic activation by concanavalin A and phytohaemagglutinin. The results point to the fact that E. cuniculi itself can cause a significant decrease in phagocytic activity of phagocytic leukocytes in the early stages of infection as well as a remarkable decrease in the proliferative response of spleen cells to T-cellular mitogens.     

Immune response to Encephalitozoon cuniculi infection in laboratory mice.

The study was performed to determine the immune response to Encephalitozoon cuniculi infection in immunocompetent mice during 120 days of experiment. Mice infected with E. cuniculi had an increased number of CD4+ T cells up to Day 20 post infection (p.i.), but counts of CD8+ T lymphocytes were significantly lower up to Day 90 p.i. in peripheral blood. Blood monocytes were significantly increased on the Day 60 and Day 120 of infection. A lack of significant decrease of CD4+ T cells may be considered as an important event in the immune response to E. cuniculi infection in immunocompetent mice.     

Humoral immune response in adult blue foxes (Alopex lagopus) after oral infection with Encephalitozoon cuniculi spores

Encephalitozoon cuniculi causes severe diseases in blue fox puppies. When pregnant vixens are infected, parasites are transmitted over the placenta to the unborn that subsequently develop encephalitozoonosis. Adult foxes themselves do not have signs of disease, but show antibody titres to E. cuniculi. The purpose of the present study was to gain information on the immune response in adult foxes after experimental infection. Sixteen foxes were infected orally with E. cuniculi spores, eight of them twice and 28 days apart. The two groups of animals showed elevated serological values in both the carbon immunoassay and in the ELISA. Elevated serological levels were recorded up to 1 year after the infection took place. The control group (n=8) remained serologically negative throughout the trial. The results of the study showed that blue foxes could be seropositive for at least a year after oral infection with E. cuniculi.     

Immune response in rams experimentally infected with Brucella ovis

Cellular as well as humoral immune responses were detected in six rams experimentally infected with Brucella ovis. Specific antibodies were detectable by enzyme-linked immunosorbent assay by day 11 after infection in all the rams. The levels of IgM antibodies and total antibodies in the serum rose until 33 and 41 days after infection respectively, then levelled off. Antigen-induced blastogenic responses by lymphocytes developed as early as five days after infection in all rams but had decreased to low levels by day 63 in most. Blastogenesis induced by phytohaemagglutinin and concanavalin A varied among infected rams and did not differ significantly (P greater than 0.05) from control rams. All rams had developed delayed-type skin hypersensitivity by day 63 after infection. One ram which did not become infected as a result of exposure had low levels of B ovis serum antibodies and a detectable antigen-induced lymphocyte blastogenic response before infection, suggesting the involvement of cell-mediated immunity in protection against B ovis.     

Cell-mediated immune response to rabies virus in dogs following vaccination and challenge

Peripheral blood lymphocytes (PBL) from non-vaccinated dogs and from dogs either vaccinated intramuscularly (IM) or subcutaneously (SC) with an inactivated rabies virus vaccine (Rabguard-TC, Norden Laboratories, Lincoln, NE) or intramuscularly with an attenuated rabies virus vaccine (Endurall-R, Norden Laboratories, Lincoln, NE) were exposed in vitro to rabies virus. Blastogenesis of PBL was measured by incorporation of 3H-thymidine into the DNA of proliferating cells in the presence of a suboptimal concentration of phytohemagglutinin (PHA). Following the first vaccination, there was no difference in the blastogenic response of lymphocytes from dogs vaccinated IM with either the inactivated or attenuated rabies virus vaccines. The inactivated rabies vaccine stimulated as great or greater blastogenic response when it was given SC. The PBL from non-vaccinated control dogs were not stimulated by rabies virus. Dogs vaccinated with the inactivated vaccine developed a lymphocyte blastogenic response to rabies virus following challenge with virulent street rabies virus. Nonvaccinated control dogs did not develop a lymphocyte blastogenic response to rabies virus following challenge with virulent street rabies virus.     

Effects of ambient temperatures on clinical and immune responses of pigs infected with transmissible gastro-enteritis virus

Two- to three-months-old pigs infected with transmissible gastroenteritis (TGE) virus showed no clinical response when housed at 30°C, but comparable infected pigs exposed to temperature changes from 30°C to 4°C following infection showed typical signs of TGE. Development of TGE-specific immune responses, as measured by blastogenic response of tissue lymphocytes, occurred at 3 days post-inoculation (DPI) in pigs held at 30°C, but not until 7 DPI in infected pigs held under the adverse conditions.Immunosuppression with corticosteroids resulted in a fall in circulatory T cells, lowering of non-specific blastogenic response of circulatory lymphocytes, and clinical signs of disease when immunosuppressed pigs were infected with TGE virus and held at 30°C. It is suggested that clinical responses to TGE virus infection may be affected by the influence of ambient temperatures on the immune responses of pigs.     

Studies of encephalitozoonosis in vervet monkeys (Cercopithecus pygerythrus) orally inoculated with spores of Encephalitozoon cuniculi isolated from dogs (Canis familiaris)

Encephlitozoonosis was induced in 35 of 38 vervet monkeys (Cercopithecus pygerythrus). They were either directly (orally) inoculated with Encephlitozoon cuniculi or indirectly exposed to this protozoan parasite. Cell-culture-grown spores of E. cuniculi, isolated from the kidneys of dogs with natural, fatal disease, were administered orally to 29 of these monkeys. Another 5 were exposed in utero by orally infecting pregnant females, and 3 were exposed to horizontal infection by nursing infected infants. Only one was given an intravenous inoculation of spores. The disease was induced in non-gravid and late-pregnant adults, immunocompetent infants, and in infants that were immunologically compromised by parenteral steroid administration, as well as in one infant that was immunologically immature because of its premature birth. The effects of age, dosage, post-inoculation (PI) interval, passage level of the parasite in cell culture and immunological status of the host were correlated with macroscopical and microscopical lesions. The experimentally induced infection was confirmed either by reisolation of the parasite in cell culture or by observation of spores in tissue sections. Both confirmatory methods were supported by serological examination. Reisolation of the organism in primary cell culture prepared from kidneys usually resulted in more frequent isolates and larger yields of spores from infants than from adult vervets. Infection with E. cuniculi invariably induced subclinical disease. Based on histology, lesions were minimal to moderately severe, depending on age, PI interval, and immunological status of the host. Alimentary tract infections were seen histologically as early as three days PI. Subsequently, infections resulted in detectable lesions most consistently in the liver, kidneys and brain. Lesions in these organs were generally granulomatous and were similar to those found in canine encephalitozoonosis. In addition, multifocal interstitial pneumonitis and myocarditis as well as vasculitis and perivasculitis were seen in other tissues and organs. Infants had more severe and more widespread lesions than adults. Although lesions and spores were still present in the brain of one immunocompetent infant 36 weeks after initial infection, the disease in immunocompetent infants and adults is thought to be self-limiting. However, infection may persist. Immunological depression favoured increased growth and multiplication of the organism, and resulted in detection of more spores within inflammatory lesions as well as more intracellular colonies of the organism that were free of inflammatory reaction.(ABSTRACT TRUNCATED AT 400 WORDS)     

Serum protein response and renal failure in canine Babesia annae infection

Babesia annae piroplasms have recently been recognised as a cause of infection and disease among dogs in Europe. The pathogenesis and clinical implications of this emerging disease remain poorly understood. We conducted this study to describe the electrophoretic profiles associated with the infection and to determine if B. annae associated azotaemia is caused by renal failure. We examined by microscopy 2,979 canine blood samples submitted to a diagnostic laboratory in NW Spain between September 2001 and April 2002. Small ring-shaped piroplasms were detected in blood smears of 87 samples and the identity of 58 of these presumptive cases were confirmed by PCR. This group of 58 infected dogs and a reference group of 15 healthy non-infected dogs were our study population. For all the dogs, serum protein response to -albumin, alpha-1 globulin, alpha-2 globulin, beta globulin and gamma globulin- was measured by capillary electrophoresis. The response of infected and non-infected dogs was compared and within infected dogs, the response of those with azotaemia (19) was compared with that of non-azotaemic dogs (39). Infected dogs presented a significant elevation of total proteins and all the different globulin fractions, and significantly lower levels of albumin compared to non-infected dogs. Among infected dogs, those presenting azotaemia had significantly lower concentrations of total proteins, albumin, beta and gamma globulins, and significantly higher values of alpha-2 globulin. Specific gravity was below the threshold of 1,025 for all dogs with azotaemia for which a urine sample was available (7) suggesting that azotaemia, in these dogs was of renal origin. Azotaemic dogs had higher concentrations of cholesterol and triglycerides, probably as a result of a liver compensatory response to the loss of proteins. We conclude that serum protein response in B. annae infected dogs corresponds to the pattern of a haemolytic syndrome with intense inflammatory reaction and that the azotaemia associated to the infection is very likely of renal origin.     

Haematological and biochemical changes in dogs naturally infected with Angiostrongylus vasorum before and after treatment

Haematological and biochemical parameters were studied prospectively in 48 dogs naturally infected with Angiostrongylus vasorum in a primary care setting. Samples for analysis were obtained when treatment was started and 42days afterwards. Prior to treatment, 21% of affected dogs exhibited eosinophilia, whereas increased total white blood cell (WBC) counts and neutrophilia were observed in only 4.2%. WBC counts and concentrations of neutrophils, eosinophils and monocytes decreased significantly from days 0 to 42, indicating that, even in dogs without elevated absolute blood values, a low grade inflammatory response may be present in dogs with A. vasorum infection. Biochemical changes (especially an increase in serum globulins and a decrease in serum fructosamine) were in agreement with the findings of other studies. The results show that the diagnosis of canine angiostrongylosis should not be excluded based on unremarkable haematological and blood biochemical parameters. They also support our recent finding that a low serum fructosamine concentration may be associated with infection with A. vasorum.     

Interaction of acute feline herpesvirus-1 and chronic feline immunodeficiency virus infections in experimentally infected specific pathogen free cats.

Cats with or without chronic feline immunodeficiency virus (FIV) infection were exposed to feline herpesvirus, type 1 (FHV-1). FIV infected cats became sicker than non-FIV infected cats and required more supportive treatment. However, there were no differences in the length of their illness or in the levels and duration of FHV-1 shedding. FHV-1 infection caused a transient neutrophilia at Day 7 with a rapid return to preinfection levels. The neutrophilia coincided with a transient lymphopenia that was accompanied by a decline in both CD4+ and CD8+ T-lymphocytes. A brief decrease in the CD4+/CD8+ T-lymphocyte ratio occurred at Day 14 in both FIV infected and non-infected cats. This decrease was mainly the result of an absolute and transient increase in CD8+ T-lymphocytes. CD4+ and CD8+ T-lymphocyte numbers and CD4+/CD8+ T-lymphocyte ratios returned to baseline within 4-8 weeks in both FIV infected and non-infected cats. FIV infected cats produced less FHV-1 neutralizing antibodies during the first 3 weeks of infection than non-FIV infected animals. The IgM FHV-1 antibody response was depressed in FIV infected cats whereas the IgG antibody response was unaffected. FHV-1 infection evoked a comparable transient loss of lymphocyte blastogenic responses to concanavalin A and pokeweed mitogen in both FIV infected and non-infected cats. However, response to pokeweed mitogen took longer to return to normal in FIV infected animals. Lymphocytes from FIV infected cats had a greater and more sustained proliferative response to FHV-1 antigen than non-FIV infected cats. The ongoing IgG antibody response to FIV was not affected by FHV-1 infection.     

Platelet aggregation studies in dogs with acute Ehrlichia platys infection

Ten adult dogs (5 Beagles and 5 mixed-breed dogs) were inoculated IV with canine platelets containing Ehrlichia platys. Inclusions and morulae of E platys developed in platelets of infected dogs at 10 to 14 days after inoculation, followed by marked thrombocytopenia at 14 to 21 days. Parasitemia and marked thrombocytopenia recurred at 24 to 28 days after inoculation. Increased numbers of megakaryocytes were observed in marrow aspirate smears from infected dogs, indicative of regenerative thrombocytopenia. Prior to infection, platelet-rich plasma from these dogs was determined to have similar aggregatory response to arachidonate. After infection with E platys, the aggregatory response of platelet-rich plasma to collagen or 3 dilutions of adenosine diphosphate was evaluated. A statistically significant (P less than 0.05) inhibition of platelet aggregatory response to the lowest dilution of adenosine diphosphate was detected for mixed-breed dogs, whereas aggregation responses were unchanged in Beagles. Results indicate that platelet activation may occur in dogs with acute ehrlichial infection.     

Peripheral lymphocyte function in dogs with Brucella canis infection

Peripheral lymphocyte function in dogs with Brucella canis infection was evaluated using in vitro lymphocyte stimulation with the mitogens PHA, Con A and PWM, and killed Brucella canis organisms. Bitches with naturally occurring Brucella canis infection were compared to negative controls. There was no difference in the response to Con A and PWM between these two groups. Lymphocytes from infected dogs were less responsive (p less than .05) to PHA than were lymphocytes from controls. There was a significant (p less than .005) difference in response to Brucella canis antigen between the two groups. Lymphocytes from infected dogs were stimulated by Brucella canis antigen, whereas those from controls did not respond.     

Prevalence of antibodies to Encephalitozoon cuniculi in stray dogs as determined by an ELISA

An ELISA, using Encephalitozoon cuniculi spores as antigen, was used to determine the prevalence of specific anti-E cuniculi IgG in a group of stray dogs. In a preliminary survey 51 of 248 sera were classified as positive with titres of 1:400 to 1:3200. The 18 sera with titres of 1:400 were reclassified as negative when no IgG binding to the spores could be detected by comparison with a standard curve of anti-E cuniculi IgG. The remaining 33 sera (13.3 per cent) were classified as low, moderate or strong positives. Comparison of total IgG and specific IgG showed that specific IgG was greatly increased in the moderately and strongly positive sera. E cuniculi may be of importance as one cause of fading puppy syndrome when transmitted transplacentally, and as a complicating infection in human immunodeficiency diseases.     

Ascaris suum infection in pigs sensitizes lymphocytes but suppresses their responsiveness to phytomitogens

The effect of Ascaris suum infection and treatment with fenbendazole on the blastogenic response of peripheral blood lymphocytes to A. suum antigens and to three phytomitogens was assayed by the lymphocyte transformation technique. Repeated infections with A. suum led to the development of sensitized lymphocytes primarily responding to egg hatching fluid antigen. Treatment with fenbendazole decreased the number of specific sensitized lymphocytes, but favorably increased the resistance of pigs to reinfection. Immunity to reinfection did not correlate with the strength of the blastogenic response to A. suum antigens. Repeated infection with A. suum negatively affected the development of the blastogenic response to phytomitogens in the pigs, leading to a partial depression of the responsiveness of lymphocytes and to the partial suppression by serum. Responses to pokeweed mitogen were affected more than the responses to concanavalin A and phytohemagglutinin.     

Response to Malassezia pachydermatis by peripheral blood mononuclear cells from clinically normal and atopic dogs

OBJECTIVE: To investigate the potential cell-mediated immune response of atopic dogs to the yeast Malassezia pachydermatis and to correlate it with the type-1 hypersensitivity (humoral) response of the same population of dogs. ANIMALS: 16 clinically normal dogs, 15 atopic dogs with Malassezia dermatitis, 5 atopic dogs with Malassezia otitis, and 7 atopic control (ie, without Malassezia dermatitis or otitis) dogs. PROCEDURE: A crude extract of M pachydermatis was extracted for use as an intradermal allergy testing reagent and for stimulation of isolated peripheral blood mononuclear cells in vitro. Flow cytometry was also used to assess cell surface antigenic determinants (CD3, CD4, CD8, CD14, CD21, CD45RA, surface immunoglobulin) on peripheral blood mononuclear cells. RESULTS: Atopic dogs with cytologic evidence of Malassezia dermatitis had an increased lymphocyte blastogenic response to crude M pachydermatis extract, compared with clinically normal dogs and dogs with Malassezia otitis. Atopic control dogs did not differ significantly in their responses from atopic dogs with Malassezia dermatitis or otitis. A significant correlation was not found between the lymphocyte blastogenic response and the type-1 hypersensitivity response to M pachydermatis within any of the groups. CONCLUSIONS AND CLINICAL RELEVANCE: Cell-mediated and humoral reactivities to M pachydermatis contribute to the pathogenesis of atopic dermatitis in dogs but are not directly correlated. Modification of the dysregulated immune response toward M pachydermatis may assist in the reduction of pathologic changes associated with an atopic dermatitis phenotype in dogs.     

Microsporidia in household dogs and cats in Iran; a zoonotic concern

Microsporidia in dogs and cats is primarily caused by the obligate, intracellular parasite Encephalitozoon cuniculi, which is a member of the phylum Microsporidia. The aim of the current study is the detection of this parasite in stool samples of small animals of Iran, by polymerase chain reaction. Microsporidia spp. was found in 31% (31/100) of dogs (E. cuniculi (18/100), Encephalitozoon bieneusi (8/100) and Encephalitozoon intestinalis (5/100)), and 7.5% (3/40) of the specimens obtained from cats were infected with E. bieneusi. Sequencing of PCR products confirmed these results. In conclusion, Microsporidia infection seems to be fairly common in pet animals of Iran, especially in dogs. This finding could indicate the importance of pet animals as zoonotic reservoirs of microsporidial human infections.     

Differential expression of inflammatory and immune response genes in sheep infected with Anaplasma phagocytophilum

Anaplasma phagocytophilum infects a wide variety of host species and causes the diseases tick-borne fever (TBF) in ruminants and granulocytic anaplasmosis in humans, horses and dogs. TBF in sheep has become one of the more prevalent tick-borne diseases in some regions of Europe. A. phagocytophilum infection modifies host gene expression and immune response. The objective of this research was to characterize differential gene expression in sheep experimentally and naturally infected with A. phagocytophilum by microarray hybridization and real-time RT-PCR. The results of these studies demonstrated in sheep the activation of inflammatory and innate immune pathways and the impairment of adaptive immunity during A. phagocytophilum infection. The characterization of the genes and their expression profiles in sheep in response to A. phagocytophilum infection advances our understanding of the molecular mechanisms of pathogen infection and the pathogenesis of TBF. Collectively, these results expand current information on the mammalian host response to A. phagocytophilum infection.     

Immunosuppression of lymphocyte blastogenesis in cattle infected with Ostertagia ostertagi and/or Trichostrongylus axei

Twenty 4-month-old calves were infected with O ostertagi and/or T axei and the responses to phytolectins were evaluated. Whole blood cultures were incubated with phytohemagglutinin (PHA), concanavalin A (Con A) and pokeweed mitogen (PWM). The blastogenic response was determined by tritiated thymidine uptake with results presented as counts per minute (cpm), stimulation indices (SI) and a mononuclear cell responsive index determined by dividing the phytomitogen induced cpm by the absolute mononuclear cell number per ul. The control group results were adjusted to 100 percent and changes in the percentage difference by the parasitized calves was determined. There was a decline in lymphocyte responsiveness to PHA beginning at the time of infection. Significant depression of responses to PHA was observed in all parasitized calves 8 weeks after infection although clinical signs of parasitism did not occur. Lymphocyte responses to PW, were not different in infected calves from the control, although the O ostertagi group had significantly higher PWM mean upon than the calves infected with T. axei. A slight depression in response to Con A was also observed at 8 weeks after infection followed by a significant increase after 10 weeks. The immunosuppression appeared to be a feature of gastrointestinal parasitism and related to infections with O. ostertagi and/or T. axei.     

Apoptosis, inflammatory response and parasite load in skin of Leishmania (Leishmania) chagasi naturally infected dogs: A histomorphometric analysis

The skin has an important role in infection by Leishmania chagasi. Apoptosis modulates the inflammatory response acting distinctively either on the progression or regression of the lesions. The parasites interact with multiple regulatory systems inducing apoptosis in host cells, during cell invasion, stabilization and multiplication of pathogens. In this context, the aim of this study was to evaluate cell death within the inflammatory infiltrates, and to correlate these results with parasite load and clinical features of dogs naturally infected with L. chagasi. Fragments of skin pinnas (8 symptomatic+8 asymptomatic+6 negative controls) were used to characterize and measure the inflammatory response, parasite load and apoptosis. Diagnosis of canine leishmaniasis was confirmed by the detection of anti-Leishmania antibodies by IFA and ELISA in serum, direct visualization of the parasite and culture in spleen, liver, pinna, bone marrow and lymph nodes, and PCR (pinna). Histomorphometry was performed with images obtained from 20 representative histological fields in a light microscope. Ultra-thin sections were mounted over a 300 mesh grids, contrasted with 2% uranyl acetate and lead citrate and examined under a Transmission Electronic Microscopy. Amastigotes were only found in the skin of symptomatic animals (31.94±18.81). The number of foci and cellularity of the inflammatory infiltrates in symptomatic dogs were higher than in other groups and in asymptomatics were higher than in controls (p<0.05; Tukey). The average area, perimeter and extreme diameters of the inflammatory infiltrates obtained in symptomatic dogs were higher than in controls (p<0.05; Tukey). The apoptotic index was higher in symptomatic than in other groups and there was no difference between asymptomatics and controls (p<0.05; Tukey). Ultrastructurally, apoptotic cells were shrunken, with condensed nuclear chromatin and cytoplasm. Condensed nuclei were frequently fragmented. Internucleosomal DNA fragmentation occurred only in symptomatic cases. Amastigotes were observed within neutrophils and macrophages. Apoptosis is directly related to parasite load, intensity of inflammatory response and clinical manifestations in L. chagasi naturally infected dogs.     

Altered mitogen response of peripheral blood lymphocytes in different stages of feline immunodeficiency virus infection

To elucidate relationship between disease progress and immunologic alteration in feline immunodeficiency virus (FIV) infection, we classified naturally infected cats into clinical stage groups using the working criteria modified from those for human immunodeficiency virus (HIV) infection. Among the five distinct stages described for HIV infection, the three phases; asymptomatic carrier (AC), AIDS related complex (ARC), and acquired immunodeficiency syndrome (AIDS), were evaluated for concanavalin A (Con A)-induced lymphocyte blastogenic activities by using glucose consumption assay. There was a significant decrease of lymphocyte response in AC phase. The loss of response became marked as the disease progressed to ARC and AIDS, with an almost complete loss of mitogen response in AIDS phase. In addition to the loss of a lymphocyte function, AIDS in FIV infection was characterized by marked emaciation, anemia or pancytopenia, and postmortem evidences of opportunistic infections and lymphoid depletion.