Duration of immunity in dogs after vaccination or naturally acquired infection.

This paper reviews current scientific information about the duration of immunity induced in dogs by infection or vaccination. It describes the shortcomings of the methods used to measure the immune responses of dogs, and explains the need for basic studies on the nature of protective humoral and cellular responses, and standardised assays for the long-term duration of immunity to pathogens other than rabies. The information is inadequate to warrant uniform recommendations on the ideal intervals for vaccination; each vaccine must be evaluated on the basis of its own merits and the characteristics of the disease it is intended to guard against.

Duration of immunity in cats after vaccination or naturally acquired infection.

The necessity for cats to be vaccinated annually against common pathogens has been questioned because sarcomas have infrequently been reported at the injection site. However, with few exceptions, the duration of immunity induced by vaccination or infection is uncertain, and there may therefore be a risk associated with a decision not to revaccinate. This article reviews the information available about the duration of immunity induced by vaccination or infection in cats, and reveals many shortcomings that make blanket recommendations impossible. Each vaccine must be considered individually.

Increased egg production in juvenile turkey hens after active immunization with vasoactive intestinal peptide.

Juvenile turkey hens were actively immunized against vasoactive intestinal peptide (VIP) prior to photostimulation to evaluate its effect on enhancing egg production. VIP antibody titers were generated in the VIP immunized hens and a greater rate of egg production per hen was observed compared to controls. In addition, the first egg laying cycle was extended for an additional 7 wk without a significant decline in egg production. Over a 27-wk period, 116 settable eggs per hen were produced from the VIP immunized hens as compared to 102 and 90 eggs for the keyhole limpet hemocyanin and saline control groups, respectively. Based on the increased egg production and the extension of the first egg laying cycle, this experiment demonstrates that VIP immunization of turkey hens is potentially economically relevant.

Canine parvovirus vaccine elicits protection from the inflammatory and clinical consequences of the disease.

Inflammatory changes following infection are central to the clinical manifestation of disease. However, information regarding such changes in animal disease is limited. In canine parvovirus infected puppies we measured the levels of acute phase proteins and changes in leukocyte phenotypes and cell trafficking by flow cytometry. These parameters correlated with conventional assessment of clinical disease in a vaccine efficacy study. Seropositive (CPV-2) 6-week-old puppies given three doses of a CPV-2 containing vaccine developed significant antibody titers and remained healthy after experimental infection with CPV-2b. Unvaccinated controls developed clinical signs and shed virus. Importantly, acute phase proteins became elevated, and lymphopenia, neutropenia and modulation of neutrophil-CD4 were detected in controls but not in vaccinates.

Hen egg-white lysozyme-specific T cells elicited in hen egg-white lysozyme-transgenic mice retain an imprint of self-tolerance.

The characteristics of T cell self-tolerance were examined in hen egg-white lysozyme (HEL)-transgenic (Tg) mice that were tolerant to a dose of HEL that was immunogenic in non-Tg littermates. HEL-specific T cells were identified in the periphery of the Tg mice after immunization with 100-times more HEL than was required to achieve a response in normal littermates. The Tg T cells were functional in vivo as they were capable of providing help to generate a HEL-specific antibody response. Selective deletion of T cells specific for the dominant T cell determinant of the native protein was not the primary mechanism of T cell tolerance in the HEL-Tg mice because, similar to non-Tg littermates, the majority of lymph node (LN) and T cell clones from HEL-Tg mice were specific for the dominant T cell determinant of HEL. Rather, our findings support the idea that the HEL-reactive T cells were anergic in vivo, but could be partially activated with a strong stimulus to the immune system (i.e., 20 nmol HEL and CFA). This conclusion is based on three observations: 1) proliferation in vitro to HEL by Tg LN T cells was subnormal (25% of control) and required 2 log more Ag to proliferate when compared with proliferation of LN from non-Tg littermates; 2) T cell clones isolated from HEL-Tg mice also proliferated poorly upon stimulation with HEL and Con A, although lymphokine production from the same stimuli was similar to that obtained from non-Tg clones; 3) invariably, upon repeated antigenic stimulation in vitro, the Tg T cell clones acquired full proliferative capacity to Ag and mitogens.

Experimental autoimmune orchitis induced by testis and sperm antigen-specific T cell clones: an important pathogenic cytokine is tumor necrosis factor.

Testicular autoimmune disease (autoimmune orchitis) develops in mice immunized with testis antigen in adjuvant, occurs spontaneously in dogs, mink, and horses, and is a potential cause of human infertility. This is the first study to investigate autoimmune orchitis using monoclonal T cells. Despite the use of crude tissue antigens, 100% of the T cell lines/clones transferred autoimmune disease of the male gonad to normal syngeneic mice, with pathology that affected the testis, the epididymis and/or the vas deferens. Thus orchitogenic peptides are likely of restricted number and/or of dominant immunogenicity. Upon transfer to normal mice, the mildest and earliest pathology elicited by the cloned T cells invariably occurred in a specific region, the testicular straight tubules. Although testis antigen-derived T cell clones responded preferentially to testis antigen, and sperm antigen-derived clones responded more to sperm antigens, each of the 16 clones respond to both antigens. Thus common orchitogenic antigens exist in these germ cell populations though their quantity may differ in distribution. All orchitogenic T cell lines and clones expressed CD4 and the alpha beta T cell receptor; and when activated, they produced interleukin 2, interferon gamma, and tumor necrosis factor (TNF), but not interleukin 4. This cytokine profile characterizes the Th1 CD4+ T cell subset, known to be responsible for the delayed type immunological reaction. Importantly, since disease transfer was significantly and reproducibly attenuated when recipients were injected with neutralizing antibody to TNF, but not neutralizing antibody to interferon gamma, TNF has been defined as a cytokine important in the pathogenesis of this autoimmune disease.

Role of testicular autoantigens and influence of lymphokines in testicular autoimmune disease.

The present data on testicular autoimmune disease suggest that CD4+ helper type T cells are responsible for adoptive transfer of murine experimental autoimmune orchitis (EAO). In passive EAO, the earliest lymphoid cell infiltration is confined to terminal segments of seminiferous tubules. Both orchitis and vasitis develop. In active EAO, any location in the testis is affected, frequently involving subcapsular seminiferous tubules. The location of maximum histopathology in passive EAO coincides with the site in the normal testis that expresses maximal Ia. Demonstration of IgG in the testis after immunization with testicular antigens or after transfer of sera from orchiectomized mice immunized with testis shows that autoantigens are present on the germ cells outside the Sertoli cell barrier, suggesting the existence of dynamic protective mechanisms against immune responses to the non-sequestered autoimmunogenic germ cells in normal individuals.

Autoantigenic germ cells exist outside the blood testis barrier.

Preleptotene spermatocytes and spermatogonia are germ cells located outside the blood-testis barrier provided by the Sertoli cells. These cells have been found to express autoantigens accessible to circulating antibodies. Mice immunized with syngeneic testis with or without bacterial adjuvant had detectable IgG on cells at the periphery of seminiferous tubules. Sera from orchiectomized but not from testes-intact mice immunized with testis and adjuvants readily transferred similar IgG deposits to testes of normal recipients. When testis-specific antisera from orchiectomized mice and testis-intact mice were compared for their reactivity on prepuberal testicular cells, serum from orchiectomized donors had significantly higher reactivity. Ig was eluted from IgG-positive testes with acid buffer and was shown to be highly enriched in antibody to prepuberal testicular cells, confirming the Ag-specific nature of the IgG deposits. The testis IgG deposits reacted with antisera to IgG1 and IgG3 but not IgG2a or IgG2b. This finding can explain lack of association of C3 in the deposits. Only 30 to 40% of seminiferous tubules had IgG deposits and they coincided with stages 7 to 12 of the spermatogenic cycle. Thus, the expression of the autoantigens is stage specific. The in situ formation of immune complexes by circulating autoantibodies demonstrates conclusively that testis autoantigens are not completely sequestered, and the blood-testis barrier as an immunologic barrier is incomplete.

Evidence for active immunological regulation in prevention of testicular autoimmune disease independent of the blood-testis barrier.

It has long been considered that autoimmune disease of the testis is prevented by sequestration of testis-specific autoantigens on germ cells behind the blood-testis (BT) barrier. However, we now have evidence that not all such antigens are sequestered. Some appear to reside on germ cells in the basal compartment of the seminiferous tubule where they are accessible to antibodies and to circulating activated T cells. Mice immunized with syngeneic testis homogenate are found to have immunoglobulin G (IgG) bound to cells in the basal compartment before onset of orchitis. This IgG is absorbed from circulation by the testis and, therefore, found only in the serum of mice orchiectomized before immunization. When the IgG is eluted from the testis, it is found to react preferentially with testicular cells enriched in preleptotene spermatocytes. T cells from mice immunized with testis can be transferred to naive syngeneic mice where they infiltrate the testis to cause orchitis. This implies that the BT barrier does not need to be breached directly for specific T cells to have access to testicular autoantigens on antigen presenting cells. Thus, active systemic and/or local immunoregulatory mechanisms must operate to prevent testicular autoimmune disease. These mechanisms may operate at the level of suppressor T cells, nonspecific suppression in the local environment of the testis, antigen presentation in the testis, or lymphocyte trafficking in the testis. These mechanisms probably operate only on the afferent limb of the immune response since they are overridden and orchitis occurs once testis-specific activated T cells are generated.

Adoptive transfer of murine autoimmune orchitis to naive recipients with immune lymphocytes.

A protocol was developed for reproducibly transferring experimental autoimmune orchitis (EAO) to naive recipient mice. Cell donors were (C57BL/6 x A/J)F1 mice immunized about 14 days earlier with mouse testicular homogenate with Freund's adjuvant and an extract of Bordetella pertussis. Lymphocytes from lymph nodes and spleens were equally capable of transferring disease. As few as 5 X 10(6) cells were able to transfer EAO, which began on Day 5-7 after transfer. Infiltrate of lymphocytes and macrophages in the region of the rete testis and straight tubules was the most reproducible early lesion, suggesting that this is the initial site of T cell-antigen interaction. It was not necessary to use both Mycobacteria and B. pertussis adjuvants in donor immunization to achieve transfer of EAO. Disease transfer was antigen specific since only cells from donors immunized with TH could transfer disease. In vitro stimulation of the cells with testicular antigens and/or concanavalin A was a prerequisite to successful transfer of EAO, which was dependent on the presence of L3T4+ T cells since depletion of these cells greatly diminished EAO in recipients and the lymphocyte proliferation response to testicular antigens. Disease did not depend on an antibody response by the recipients. The results imply that effector cells, once generated by immunization and fully activated or selected by in vitro stimulation, can home to specific locations in the testis, locate relevant autoantigens, and cause disease.

Distribution of histopathology and Ia positive cells in actively induced and passively transferred experimental autoimmune orchitis.

Histopathology in testes from mice with actively induced experimental orchitis (EAO) (active EAO) and those from recipients of testis-sensitized lymphocytes (passive EAO) had different distributions. In passive EAO, maximum orchitis existed in the straight tubules, rete testis, and ductus efferentes, obstruction of which led to extreme dilatation of seminiferous tubules. Unusual intralymphatic granulomata also resulted in dilated testicular lymphatics. In active EAO, maximum orchitis affected seminiferous tubules under the testicular capsule, away from the rete testes. Vasitis was common and occurred in both active and passive EAO. In normal testes, IA+ F4/80+ cells were sparse but formed a cuff around the straight tubules. After immunization with testis in adjuvant or with adjuvant alone, the number, size, and staining intensity of IA+ cells increased dramatically beginning on day 5, 7 days before disease onset. Simultaneously, epithelial cells confined to the ductus efferentes became Ia+. Although recipients of sensitized lymphocytes also developed epithelial Ia in the ductus efferentes, they did not show changes in testicular interstitial Ia+ cells. Our findings indicate that testicular autoantigens are not completely sequestered, but are accessible to and can react with passively transferred immune lymphocytes in well-defined regions of the germ cell compartment. These regions coincided to a large extent with maximum expression of periductal or epithelial Ia. Changes in Ia+ cells in the testis, which are inducible by adjuvants and precede orchitis, may account in part for the different distribution of histopathology of active EAO.