Bovine vaginal antibody responses to immunoaffinity-purified surface antigen of Tritrichomonas foetus

Bovine neutrophils kill the sexually-transmitted parasite Tritrichomonas foetus using trogocytosis

The protozoan parasite Tritrichomonas foetus (T. foetus) is the causative organism of bovine trichomonosis (also referred to as trichomoniasis), a sexually-transmitted infection that reduces fertility in cattle. Efforts to control trichomonosis on cattle farms are hindered by the discouragement of antibiotic use in agriculture, and the incomplete, short-lived protection conferred by the current vaccines. A more complete mechanistic understanding of what effective immunity to T. foetus entails could enable the development of more robust infection control strategies. While neutrophils, the primary responders to infection, are present in infected tissues and have been shown to kill the parasite in vitro, the mechanism they use for parasite killing has not been established. Here, we show that primary bovine neutrophils isolated from peripheral blood rapidly kill T. foetus in vitro in a dose-dependent manner, and that optimal parasite killing is reduced by inhibitors of trogocytosis. We also use imaging to show that bovine neutrophils surround T. foetus and trogocytose its membrane. These findings are consistent with killing via trogocytosis, a recently described novel neutrophil antimicrobial mechanism.

Proteomic analysis of proteins released by Tritrichomonas foetus: Identification of potential targets for the development of new diagnostic methods

Bovine trichomonosis (BT), a disease of the bovine urogenital tract, is caused by the protozoan Tritrichomonas foetus (Tf). Tf causes endometritis, infertility, and premature death of the embryo, which generates considerable economic losses. The proteins released can mediate fundamental interactions between the pathogen and the host, triggering factors associated with the symptomatology, immune evasion and pathogenesis characteristic of the species. However, little is known about the profile of the proteins released by Tf. In order to contribute to their knowledge, we performed an isolation protocol and a proteomic profiling of the supernatant (SN) content of six Tf isolates. A total of 662 proteins present in the SN of Tf were detected, out of which 121 were shared by the six isolates, while the remaining 541 were found in at least one of the isolates studied. The comparative analyses using the databases of Tf strain genome K revealed 32.9% of uncharacterized proteins. The bioinformatic analyses showed that the main molecular functions predicted were binding (47.9%) and catalytic activity (38.2%). Additionally, we performed immunodetection assays to evidence the antigenic potential of SN proteins. Interestingly, we observed great ability to detect SN proteins from all six isolates using serum from immunized mice and infected bulls. A complementary mass spectrometry assay allowed us to determine that the proteins that showed the strongest signal intensity in the immunoassays were Grp78 (A0A1J4IZS3) and Ap65 (A0A1J4JSR1). This work represents the first proteomic characterization of Tf SN proteins and their antigenic potential, which might be interesting for the future design of new diagnosis and treatment methods for BT.

Trichomonas

The most widely known trichomonad in veterinary medicine is Tritrichomonas foetus. It is the etiologic agent of bovine tritrichomonosis, a sexually transmitted disease in extensively managed herds throughout many geographic regions worldwide. The same trichomonad species is also regarded as the causative agent of chronic diarrhea in the domestic cat, although more recent studies observed molecular differences between bovine- and feline-derived T. foetus. Trichomonosis in cats has a worldwide distribution and is mainly present among cats from high-density housing environments. Other trichomonads are found as inhabitants of the gastrointestinal tract in birds, such as Trichomonas gallinae. Particularly, Columbiformes, Falconiformes, Strigiformes, and wild Passeriformes can be severely affected by avian trichomonads. Diagnosis of trichomonosis is often complicated by the fragility of the parasite. To ensure valid test results, it is essential to collect and handle specimens in the right way prior to analysis. Cultivation tests, the specific amplification of parasites, or a combination of both test methods is the most efficient and most commonly used way to diagnose trichomonosis in animals. Bovine tritrichomonosis is mainly controlled by the identification and withdrawal of infected animals from bovine herds. The control of feline and avian trichomonosis relies mainly on preventive measures.

Development of a bead-agglutination assay for rapid detection of Tritrichomonas foetus

Tritrichomonas foetus is a flagellated protozoan parasite that causes inflammation of the reproductive tract leading to early embryonic death and abortion in cattle, thereby resulting in significant economic losses. Testing and culling infected bulls is an important strategy for parasite control. Routine testing is mainly limited to bulls that are traveling across state lines or within states that have specific control programs. Both culture and PCR detection methods are available, but they are not typically conducted as part of a yearly breeding soundness program and are not easily conducted in the field. In the present study, we developed a bead agglutination assay for detection of T. foetus antigens. Our experiments revealed that latex beads conjugated to T. foetus lipophosphoglycan-binding antibodies visibly clump in the presence of T. foetus. The detection limit of the assay, determined using both field and laboratory isolates of the parasite, was 0.25μg/mL and 1.0μg/mL total T. foetus antigen, respectively. Our results indicate that an antigen detection test could offer a tool for screening bulls under field conditions.

Uterine Mast Cells and Immunoglobulin-E Antibody Responses During Clearance of Tritrichomonas foetus

We showed earlier that Tritrichomonas foetus-specific bovine immunoglobulin (Ig)G1 and IgA antibodies in uterine and vaginal secretions are correlated with clearance of this sexually transmitted infection. Eosinophils have been noted in previous studies of bovine trichomoniasis but the role of mast cells and IgE responses have not been reported. The hypothesis that IgE and mast cell degranulation play a role in clearance was tested in 25 virgin heifers inseminated experimentally and infected intravaginally with T. foetus strain D1 at estrus and cultured weekly. Groups were euthanatized at 3, 6, 9, or 12 weeks, when tissues were fixed and secretions were collected for culture and antibody analysis. Immunohistochemistry using a monoclonal antibody to a soluble lipophosphoglycan (LPG)-containing surface antigen (TF1.17) demonstrated antigen uptake by uterine epithelial cells. Lymphoid nodules were detected below antigen-positive epithelium. Little IgG2 antibody was detected but IgG1, IgA, IgM, and IgE T. foetus-specific antibodies increased in uterine secretions at weeks 6 and 9 after infection. This was inversely proportional to subepithelial mast cells numbers and most animals cleared the infection by the sampling time after the lowest mast cell count. Furthermore, soluble antigen was found in uterine epithelium above inductive sites (lymphoid nodules). Cross-linking of IgE on mast cells by antigen and perhaps LPG triggering appears to have resulted in degranulation. Released cytokines may account for production of predominantly Th2 (IgG1 and IgE) and IgA antibody responses, which are related to clearance of the infection.

A review of sexually transmitted bovine trichomoniasis and campylobacteriosis affecting cattle reproductive health

The objective is to discuss sexually transmitted diseases caused by Tritrichomonas foetus (T foetus) and Campylobacter fetus (C fetus) subsp. venerealis, with a focus on prevalence, pathogenesis, and diagnosis in cows and bulls. Diagnosis and control are problematic because these diseases cause severe reproductive losses in cows, but in bulls are clinically asymptomatic, which allows the disease to flourish, especially in the absence of legislated control programs. We review research regarding prophylactic systemic immunization of bulls and cows with antigens of T foetus and C fetus venerealis and their efficacy in preventing or clearing preexisting infections in the genital tract. Current diagnostic methods of C fetus venerealis and T foetus (microbial culture and PCR) should be improved. Review of the latest advances in bovine trichomoniasis and campylobacteriosis should promote knowledge and provide an impetus to pursue further efforts to control bovine sexually transmitted diseases.

Antibodies to Trichomonas vaginalis surface glycolipid

BACKGROUND

Human trichomoniasis is the most common non-viral sexually transmitted disease, yet immune responses are not well studied.

METHODS

Since the Trichomonas vaginalis lipophosphoglycan (TvLPG) is an important virulence factor, a bank of eight monoclonal antibodies was generated to define the antigen in clinical isolates. The TvLPG-specific antibody response of women who were culture positive (n=33) or negative (n=33) for T vaginalis infection was determined by isotype-specific ELISA.

RESULTS

The bank of monoclonal antibodies reacted with conserved surface TvLPG epitopes in 27 isolates from pregnant women at their first prenatal visit. Conserved TvLPG epitopes were shown to be surface exposed by immunofluorescence. Sera collected from the same patients at the same time were assayed for specific antibodies. Serum and vaginal secretions from 33 T vaginalis-positive women had statistically higher IgG anti-TvLPG levels than age-matched and race-matched negative controls in the same clinical study (p<0.01). Vaginal IgA anti-TvLPG levels of the women with trichomoniasis were almost significantly higher than controls (p=0.055). Infected women with normal pregnancies had significantly higher vaginal IgG anti-TvLPG values than infected women with adverse outcomes of pregnancy.

CONCLUSIONS

These antibody responses show that infected women can respond to the conserved TvLPG antigen. Since antibodies to trichomonad surface LPG protect in a bovine model of trichomoniasis, the role of these antibodies in the human disease should be investigated.

Immunity to infections in the lower genital tract of bulls

The mucosa of the bovine prepuce has unique immunological characteristics critical to defense against sexually transmitted diseases. Tritrichomonas foetus and Campylobacter fetus subspecies venerealis persistently colonize the lower genital tract of bulls but usually do not cause either major clinical signs or inflammation. These microbes may be sexually transmitted to female cattle to cause reproductive failure. Although the male genital immune responses to T. foetus and C. fetus subspecies venerealis are inefficient in clearing infection, systemic immunization with T. foetus and C. fetus subspecies venerealis antigens does prevent or eliminate these infections with induction of IgG antibodies in genital secretions and serum.

Neutrophils and inducible nitric-oxide synthase are critical for early resistance to the establishment of Tritrichomonas foetus infection

Tritrichomonas foetus is the cause of trichomoniasis in cattle. Severe infection is often associated with heavy neutrophil and macrophage accumulation, although it is not known how this response protects during early parasite colonization. The goal of this study was to examine the effects of an early host response upon initial T. foetus colonization within the murine reproductive tract. Mice depleted of neutrophils before T. foetus infection had a significantly higher parasite burden within the reproductive tract compared with mock-depleted control mice. Additionally, gp91(phox-/-)/ iNOS(-/-), and iNOS(-/-) mice had substantially larger parasite burdens than C57BL/6 control mice, whereas gp91l(Phox-/-) mice had similar parasite burden to C57BL/6 control mice. Interestingly, phorbol 12-myristate 13-acetate-stimulated neutrophils and macrophages isolated from all groups of mice were unable to kill T. foetus in vitro. However, macrophages isolated from gp91l(phox-/-) and C57BL/6 mice stimulated with interferon-gamma and lipopolysaccharide were able to kill T. foetus in vitro, whereas macrophages isolated from gp91(phox(-/-)/ iNOS(-/-) and iNOS(-/-) mice were unable to kill T. foetus, suggesting the ability of macrophages to produce reactive nitrogen species but not reactive oxygen species (ROS) is critical for parasite killing during early infection in vivo and in vitro. Additionally, neutrophils seem to control early dissemination of T. foetus throughout the reproductive tract, although production of ROS is not critical for this process.

Uterine Response to Multiple Inoculations with Arcanobacterium pyogenes and Escherichia coli in Nulliparous Ewes

PROBLEM

Uterine infections seem more severe in nulliparous animals. Our objective was to determine whether intrauterine inoculation of nulliparous ewes with Arcanobacterium pyogenes and Escherichia coli would produce an antibody response and reduce the severity of subsequent infections.

METHOD OF STUDY

Nulliparous ewes (n = 9/treatment) received (i) 'primary intrauterine inoculation' with phosphate-buffered saline (PBS) and 'secondary intrauterine inoculation' with PBS; (ii) primary PBS-secondary 75 x 10(7) cfu of A. pyogenes and 35 x 10(7) cfu of E. coli (PBS-Bacteria); (iii) primary bacteria-secondary PBS; or (iv) primary bacteria-secondary bacteria (Bacteria-Bacteria).

RESULTS

Inoculations evoked an antibody response. Postmortem examinations 6 days after the secondary inoculation indicated that PBS-treated ewes did not develop uterine infections, but all bacteria-treated ewes did. Infections were either less severe or closer to resolution in Bacteria-Bacteria than they were in PBS-Bacteria ewes.

CONCLUSIONS

Intrauterine inoculation of nulliparous ewes with A. pyogenes and E. coli evokes an antibody response that may help the uterus reduce the severity of subsequent infections.

Heifers immunized with whole-cell and membrane vaccines against Tritrichomonas foetus and naturally challenged with an infected bull

The performance of a whole-cell vaccine and the other vaccine with cellular membranes of Tritrichomonas foetus applied to heifers naturally challenged by mating with an infected bull was determined. Forty heifers were divided into three groups: a control group (n=16) without immunizing, another group (n=12) immunized with whole cells (10(8)/dose) and a third group (n=12) immunized with cellular membranes (300 micro g of membranes/dose protein). The females were subcutaneously vaccinated at 3-week on two occasions and received a third intravaginal booster dose. After 3 weeks of the last vaccinal doses, the heifers were served by a T. foetus infected bull over 90-day period. The mean duration of infection for membrane-vaccinated heifers was 60 days +/-25, compared with 63 days +/-35.8 of infection for whole-cell-vaccinated heifers and 79 days +/-41.3 for control heifers. Calving rates were 6/12 for membrane-vaccinated heifers, 3/12 for whole-cell-vaccinated animals, and 2/16 for control animals. Fetal mortality rates were 3/12 for membrane-vaccinated animals, 4/12 for those vaccinated with whole cells and 10/16 for control animals. These reproductive parameters were significantly different (P<0.05) between heifers vaccinated with membranes and control heifers. The hemolytic test and enzyme-linked immunoabsorbent assay (ELISA) with T. foetus antigen showed that serum immunoglobulins peaked before and during the breeding period. The heifers vaccinated with membranes developed an important response during the critical period of fetal loss, second and third month of the breeding time, and another month after the same period. The ELISA method was more sensitive and more reliable than the hemolytic test for the evaluation of the systemic immune response in females infected and/or vaccinated with T. foetus.

Antibodies as effectors

Antibodies are critical in protection against extracellular microbial pathogens. Although antibodies also play a role in transplant/tumor rejection and in autoimmune disease, this paper focuses on defense against bovine infections. Effector mechanisms of different bovine isotypes, subisotypes and allotypes are discussed. The importance of antigen specificity is also stressed.

Demonstration of Tritrichomonas foetus in the external genitalia and of specific antibodies in preputial secretions of naturally infected bulls

Portions of penis and prepuce were collected from 24 bulls with current or recent Tritrichomonas foetus infection. Epididymides were collected from seven of the bulls, and seminal vesicles and prostate were collected from four. Following immunohistochemical staining with two monoclonal antibodies (34.7C4.4 and TF1.15) prepared against T. foetus surface antigens, trichomonads were identified in sections from 15 of the bulls. Organisms were most often located in penile crypts in the midshaft and caudal regions and less often in preputial crypts. Trichomonads were not observed in sections from other genitalia or in subepithelial tissue. T. foetus antigen, however, was present in the cytoplasm of some epithelial cells and the cytoplasm of some mononuclear cells in subepithelial lymphoid aggregates and follicles. Preputial smegma was collected from 16 T. foetus-infected bulls and from 16 control bulls with negative T. foetus cultures. Preputial antibody levels to TF1.17, a surface antigen of T. foetus, were determined by an enzyme-linked immunosorbent assay. Preputial secretions from infected bulls contained specific antibody of each isotype and subisotype tested. IgG1 responses were the greatest, IgM and IgA responses were approximately equal, and IgG2 responses were low. Each isotype and subisotype response in infected bulls was significantly greater than that in the controls. These results confirm previous speculation concerning anatomical sites of infection and suggest that parasite antigen can be taken up and processed locally, resulting in deposition of specific IgG1, IgG2, IgA, and IgM antibodies in the preputial cavity.

Host-parasite interaction in bovine infection with Tritrichomonas foetus

Tritrichomonas foetus is a parasite of particular veterinary importance causing bovine tritrichomonosis, a sexually transmitted disease leading to infertility and abortion. The present review summarizes the current knowledge on potential mechanisms of pathogenicity of T. foetus, the immunology of host-parasite interaction in bovine tritrichomonosis, and the experimental model systems of this parasitic disease.

Female reproductive tract immunity in bovine trichomoniasis

PROBLEM

Mechanisms of protective immunity in the female reproductive tract are poorly understood. For sexually transmitted diseases, bovine trichomoniasis is a useful model because it resembles human trichomoniasis to some extent, and antibodies play an important role in protection against these extracellular parasites. Protective efficacy was compared in animals with genital responses of predominantly immunoglobulin G (IgG) or predominantly IgA antibodies to a purified surface antigen of Tritrichomonas foetus.

METHOD OF STUDY

Immunization of mice by various routes with immunoaffinity-purified T. foetus surface antigen (TF1.17) or killed cells was used to define the best routes and antigen combinations to give predominantly IgG or IgA antibodies to TF1.17 antigens in genital secretions. Cattle were then immunized either subcutaneously (SC) two times with TF1.17 antigen and once SC with killed T. foetus or twice SC with TF1.17 antigen and once intravaginally with killed T. foetus. All immunizations were in Quil A adjuvant. Controls were not immunized. Animals were challenged intravaginally with 10(6) T. foetus 3 weeks after the third immunization. Vaginal mucus was collected weekly for culture and antibody assays. Serum was collected weekly, and uterine secretions were collected at 10 weeks post-challenge. Tissues were fixed at 10 weeks also.

RESULTS

Murine studies showed systemic priming with vaginal boosting gave the highest genital IgA responses. In cattle, systemic immunization (group S) induced high IgG1 antibody levels in vaginal secretions. Systemic priming with vaginal boosting (group S/V) primed for an anamnestic vaginal IgA response after challenge with T. foetus. Cattle with predominantly IgG or predominantly IgA responses in vaginal secretions either did not become infected or cleared infection faster than controls. Uterine IgA responses at 10 weeks were highest in the vaginally boosted group, but other responses were not different from the controls at this time point. Microscopic examination of genital tissues showed subepithelial infiltration of mononuclear cells in all groups. Lymphoid aggregates or nodules were detected in vaginal sections in cattle of groups S/V and C as well as in uterine sections of all animals in all three groups.

CONCLUSIONS

Both IgG and IgA antibodies to T. foetus superficial antigen were associated with protection. The timing of the response was related to the time of clearance. Lymphoid organization in the vagina and uterine tissues suggested development of mucosal inductive sites.

Pathogenesis, diagnosis, and management of trichomoniasis in cattle

Trichomoniasis is a disease of the pregnancy, but apparently not of either the cow or the bull, except in the case of postcoital pyometra. Its self-limiting nature in the cow and chronic nature in the bull mean that a positive diagnosis for the herd can more easily be obtained from bulls than from cows. Incubation of preputial scrapings or washings (or pyometritic fluid, if available) in a selective growth medium such as the InPouch system is the diagnostic method of choice. The diagnosis is based on identification of the morphology and characteristic rolling motility of the trichomonad. "High tech" molecular approaches may eventually offer greater diagnostic sensitivity than can culture methods, but currently they are no more accurate. In addition, serologic screening of the female herd (but interestingly, not the bulls) may become possible and may allow the practitioner to at least determine whether exposure has occurred in an unvaccinated herd. Control in an infected herd involves no pharmacologic treatment but rather culling of infected bulls, retention of younger, culture-negative bulls, and segregation of the female herd by reproductive status.

Serological response to in vitro-shed antigen(s) of Tritrichomonas foetus in cattle

We developed a serological assay for detection of (l) an erythrocyte-adhering molecule(s) shed by the bovine venereal pathogen Tritrichomonas foetus and (II) serum antibodies to this antigen(s) in exposed cattle. Sera from exposed and unexposed cattle were tested for their ability to induce complement-mediated lysis of bovine erythrocytes that had been previously incubated overnight at room temperature in pH-adjusted supernatants of T. foetus culture media. Eight of 180 serum specimens from six groups of presumably unexposed cows or heifers showed a positive (> or = 1:2) hemolytic titer (specificity = 95.6%). Thirteen of 14 females in two experimentally infected groups showed a positive hemolytic titer following infection (sensitivity = 94%). In experimentally infected heifers, there was little correlation (r2 = 0.33) between serum hemolytic titers with respect to shed antigen and titers obtained in serum enzyme-linked immunosorbent assays in which whole T. foetus served as the antigen. Serum hemolytic titers rose 3 to 4 weeks sooner than did previously described vaginal mucus immunoglobulin G1 or immunoglobulin A titers with respect to whole-cell antigen or TF1.17 subunit antigen, respectively. Among 14 chronically infected bulls, only 6 (43%) showed a positive hemolytic titer. This study is the first, to our knowledge, to show a specific serological response in the host to an in vitro-shed antigen(s) of T. foetus and suggests a useful diagnostic test for potentially exposed herds.