Delayed-type hypersensitivity to rabies virus in mice: assay of active or passive sensitization by the footpad test

Effect of the bacillus of Calmette-Guérin, Propionibacter acnes and avridine as immunomodulators in antirabies vaccination of mice using the Fuenzalida-Palacios mouse brain vaccine

Using the laboratory mice, Fuenzalida-Palacios mouse brain human rabies vaccine was administered in groups of animals previously inoculated with rabies virus and then submitted to treatments with the immunomodulators onco-BCG, avridine and Propionibacterium acnes. Humoral and cellular immune responses were evaluated through the macrophage inhibition factor (MIF), intra-pad inoculation (IPI) and serum neutralization (SN) tests and by the detection of gamma-interferon (IFN-gamma). The IPI test was not effective in detecting the response of delayed-type hypersensitivity, contrary to MIF, which showed the immune cellular response. Higher levels of IFN-gamma were observed in the groups of mice vaccinated and treated with avridine and P. acnes. Although immunomodulating activities have been detected, the use of adjuvants with the Fuenzalida-Palacios type vaccine in mice did not reveal any encouraging results.

Effect of bacillus of Calmette-Guérin, avridine and Propionibacterium acnes as immunomodulators on rabies in mice

The cellular and humoral immune responses of mice inoculated with rabies virus and treated with the Bacillus of Calmette-Guérin, Avridine and Propionibacterium acnes were evaluated in this paper. There was a higher percentage of surviving mice in groups submitted to P. acnes treatment. Lower levels of interferon-gamma (IFN-gamma) were found in infected mice. The intra-pad inoculation test (IPI) was not effective to detect cellular immune response, contrary to the results found in MIF reaction. The survival of mice did not present correlation with the levels of antirabies serum neutralizing (SN) antibodies titers, IFN-gamma concentration and MIF response.

Effect of vaccination and the immunomodulators "bacillus of Calmette-Guérin, avridine and Propionibacterium acnes" on rabies in mice

Responses of vaccination and treatment to immunomodulators against rabies in mice were evaluated through macrophage inhibition factor (MIF), intra-pad inoculation (IPI) and serum neutralization (SN) tests and by the detection of gamma-interferon (IFN-gamma). Onco-BCG, Avridine and Propionibacterium acnes were administered to groups of mice. Higher survival rates were found in animals treated with P. acnes. Lower levels of IFN-gamma were observed in the groups of infected and vaccinated mice. The IPI was not effective on detecting the response of delayed-type hypersensitivity. Vaccine induced in the infected animals a more intense response to MIF reaction.

Delayed-type hypersensitivity response to high doses of adenoviral vectors

The present study evaluates the hypothesis that delayed-type hypersensitivity (DTH) contributes to the inflammatory reaction observed when high-dose adenoviral (Ad) vectors are administered to a previously immunized animal. Immunocompetent C57BL/6 mice immunized intraperitoneally with 10(9) pfu AdCMV.Null [an E1-, E3- Ad vector with a cytomegalovirus (CMV) promoter but no transgene] and challenged intradermally to the footpad with the same vector demonstrated significant footpad swelling 24 hr after challenge with 10(9) pfu, but not with a lower dose. Footpad histology revealed a mononuclear-granulocytic cellular infiltrate typical of that seen in DTH. Evaluation of the same doses of vector in immunodeficient mice nu/nu and RAG-2- on the C57BL/6 background, and nu/nu and severe combined immunodeficiency (SCID) on the BALB/c background demonstrated suppression of footpad swelling. However, the footpad response remained intact in beta 2-microglobulin deficient (beta 2-m-) mice, suggesting minimal or no role of major histocompatibility complex (MHC) class I-mediated mechanisms for the region of localized inflammation. Challenge with an Ad expressing the interleukin-2 cDNA to immunized C57BL/6 mice demonstrated augmented footpad swelling response. Finally, pretreatment with cyclosporin resulted in a 69% inhibition of the response compared to controls, whereas other immunosuppressants (cyclophosphamide, methotrexate, and hydrocortisone) had no inhibitory effect. These findings provide further insight into the dynamic interplay of immune processes ultimately leading to inflammation when high-dose Ad vectors are administered to a target organ.

Role of CD4+ and CD8+ T cells in murine resistance to street rabies virus

Mice of the SJL/J and BALB/cByJ inbred strains are naturally resistant to street rabies virus (SRV) injected via the intraperitoneal route. To determine the cellular mechanism of resistance, monoclonal antibodies specific for CD4+ or CD8+ subsets of T cells were used to deplete the respective cell population in SRV-infected animals. Elimination of CD4+ T-helper cells abrogated the production of immunoglobulin G (IgG) neutralizing antibodies in response to rabies virus infection and reversed the resistant status of SJL/J and BALB/cByJ mice. In contrast, in vivo depletion of CD8+ cytotoxic T cells had no measurable effect on host resistance to SRV. These results indicate that serum neutralizing antibodies of the IgG class are a primary immunological mechanism of defense against rabies virus infection in this murine model of disease. CD8+ cytotoxic T lymphocytes, which have been shown to transfer protection in other rabies virus systems, appear to have no role in protecting mice against intraperitoneally injected SRV.

Cellular immunity in experimental Echinococcus multilocularis infection. I. Sequential and comparative study of specific in vivo delayed-type hypersensitivity against E. multilocularis antigens in resistant and sensitive mice

Species- or strain-related differences in receptivity of intermediate hosts to E. multilocularis larvae could be related to differences in specific cellular immune response of the host. In order to test this hypothesis, we assessed the delayed-type hypersensitivity (DTH) to E. multilocularis antigens (EmAg) in mice of three strains differing by their sensitivity (AKR and C57BL.6) or resistance (C57BL.10) to E. multilocularis infection. DTH was determined by measuring in vivo the foot-pad response 24 h after an EmAg antigenic challenge. The level of positive response was evaluated in immunized mice; however, a typical DTH response was only observed by immunizing mice with a strong adjuvant schedule. Course of DTH in the immunized mice was shown to be somewhat different in sensitive and resistant mice. The differences were much more marked in mice infected with proliferative E. multilocularis larvae. The levels of the footpad response was significantly higher in resistant mice, although the peak of the reaction was obtained later than in sensitive mice. DTH, expressed by the foot-pad response against EmAg, remained significant for the entire period of observation in sensitive as well as in resistant mice. There was no correlation between receptivity of the murine hosts and levels of specific antibodies against EmAg. These results suggest a relationship between resistance to E. multilocularis infection and intensity and/or course of DTH in mice. The resistance could be mediated by some particularities of the in situ cellular immune response in the periparasitic granuloma.

Studies on cell-mediated immune response to rabies virus immunization in dogs

Peripheral blood leucocytes (PBL) from unvaccinated dogs and dogs vaccinated subcutaneously with beta-propiolactone (BPL) inactivated sheep brain antirabies vaccine were exposed in vitro to rabies antigen. A direct leucocyte migration inhibition (LMI) assay in agarose was used to study the cell-mediated immune (CMI) response. The CMI response could be detected as early as 7 days postvaccination. It reached a peak by 14 days postvaccination followed by a decline. The PBL from unvaccinated control dogs were not stimulated by rabies virus antigen.

Induction of delayed-type hypersensitivity to measles virus in mice

Intracutaneous injection of inactivated measles virus (MV) into hind footpads of BALB/c mice infected 5 to 11 days previously with MV produces a strong delayed-type hypersensitivity (DTH) response. Pretreatment of mice with cyclophosphamide (CP) results in a significantly stronger response. In CP-pretreated mice, the optimal infecting dose of live MV and the restimulating amount of inactivated MV are approximately 10(7) plaque-forming units and 2 micrograms/mouse, respectively. The optimal time after infection for measuring DTH to MV is 7 days, while the optimal CP-pretreatment concentration is 200 mg/kg. The DTH response generated by MV is specific and not caused by fetal calf serum or Vero cell antigens. MV DTH is transferable to uninfected mice with lymph node cells. Transfer of DTH is sensitive to treatment with anti-Thy 1.2 serum plus complement, indicating the response is T cell dependent. With this sensitive assay for measuring cell-mediated immunity to MV, it will now be possible to analyze T cell cross-reactivity among paramyxoviruses and assess viral cell-mediated immunity in mice infected with neuroadapted MV.

Specific cutaneous hypersensitivity responses in mice infected or immunized with Trypanosoma cruzi

The appearance and development of cutaneous hypersensitivity to epimastigote antigen was followed during the early phase of Trypanosoma cruzi infection in mice. The effect of living BCG on the kinetics of skin reactivity was studied in animals infected with T. cruzi blood trypomastigotes or artificially immunized with disrupted epimastigotes. BCG stimulated the immediate response in infected animals while preferentially stimulating delayed responses in immunized animals. Infection with living blood trypomastigotes depressed already existing delayed-type responses. The development of delayed-type responses was also impaired in animals immunized in the course of the infection.

Delayed-type hypersensitivity response in mice to Treponema pallidum

C3H/HeJ mice which had been primed with either virulent or killed T. pallidum were studied for in vivo delayed-type hypersensitivity (DTH) responses to T. pallidum following local footpad challenge. Mice sustaining a chronic infection of 5 months duration failed to develop a DTH to treponemal antigens, whereas priming by a single intravenous injection with killed organisms resulted in a significant DTH response in mice when challenged 5 days later. Treatment of mice prior to priming with a single sublethal dose of cyclophosphamide (100 mg/kg body weight) not only failed to potentiate T. pallidum-DTH, but abrogated the response observed in untreated primed animals.

Cytotoxicity reactions against target cells infected with rabies virus

Some aspects of the cytotoxicity reactions were studied in the rabies system. The antibody-dependent complement cytotoxicity (ADC), the cellular cytotoxicity (CC), and the antibody-dependent cellular cytotoxicity (ADCC) are shown, being the cytotoxic effect as evidenced by the 51Cr released from the cells infected with the Pasteur strain of rabies virus. Some parameters such as time of cellular infection, the amount of infected cells, the concentration of complement, and the incubation time of the ADC reaction, which help to increase the performance of this reaction, are discussed. The detection and the level of the cellular response against the Pasteur strain of rabies virus in immunized mice is shown. Evidence is presented that in the ADCC test, specific human antibodies and non-immune human lymphoid cells are able to mediate in vitro lysis of cells infected with rabies virus. A comparison of the ADCC test with serum neutralization and immunoenzymatic tests is shown.

Frequency analysis of cytolytic T cell precursors (CTL-P) generated in vivo during lethal rabies infection of mice. I. Distinction of CTL-P with different interleukin 2 sensitivity

The aim of this study was to determine the number and state of activity of cytolytic T lymphocytes (CTL) and their precursors (CTL-P) present in vivo during the early stages of viral infection. The local response to lethal infection with rabies virus was used as a model system that is not accessible to analysis by secondary activation in vitro. The local response to alloantigen served as a control. Experimental protocols were established that allow frequency estimates of in vivo antigen-triggered CTL-P. Data allow a distinction between CTL-P activated in vivo by alloantigen and viral antigen with respect to their different capacity to utilize T cell growth factors (interleukins). In vivo alloantigen-primed CTL-P generate, in vitro, an active effector progeny in the presence of interleukins of xenogeneic origin, whereas the majority of virus-specific CTL-P, in spite of considerable expansion in vivo, fail to generate CTL in vitro unless antigen is added.

Delayed-type hypersensitivity and acquired resistance to plague in mice immunized with killed Yersinia pestis and immunoregulators

A simple reproducible footpad assay of delayed-type hypersensitivity (DTH) to Yersinia pestis was studied in mice immunized with 5 x 10(7) heat killed (HK) Y. pestis alone or in conjunction with Freund's complete adjuvant (FCA), cyclophosphamide (CY), BCG, or both CY and BCG. The footpad reaction elicited with 5 x 10(6) HK Y. pestis was shown to peak at 24 hr, was transferable with immune T lymphocytes but not with serum and had the classical DTH histology, The highest level of DTH occurred 6 or 8 days after immunization, according to the immunomodulator used, and immunized mice were therefore challenged with viable Y. pestis at this time. No correlation was found between DTH level and resistance of mice; only groups immunized under the potentiating effect of BCG used alone or with CY were significantly protected against Y. pestis. Control groups pretreated with BCG or BCG pretreated and immunized with a large dose of an unrelated gram negative bacterium were as susceptible to Y. pestis infection as normal mice. To promote this protective immunity, BCG and HK Y. pestis, must be injected in an area that drains to a common lymph node. No antibody to Y. pestis was found in immunized protected mice pretreated with BCG and CY and a very low antibody titre was found in immunized mice pretreated only with BCG. This serum was unable to confer resistance on recipient mice but immune cell transfer decreased the number of Y. pestis counted in the spleens of recipients 36 hr after challenge.

Essential Role of T cells in the postexposure prophylaxis of rabies in mice

Athymic nude mice injected intramuscularly with a street stain of rabies virus were not protected against rabies by postexposure administration of beta-propiolactone-inactivated rabies vaccine. In contrast, their normal littermates were completely protected from death by the same vaccination regimens. Nude mice did not produce IgG antibody as a result of the vaccine during the test period of 15 days, whereas normal littermates produced IgG antibody from day 5 after vaccination. However, passive immunization with antirabies hyperimmune mouse ascites showed that antibody was completely ineffective in protecting either nude mice or their normal littermates against rabies when given later than 2 days after infection. No significant difference in the induction of circulating interferon by the vaccination was noted in these mice. Passive transfer of immune spleen cells to nude mice immediately after infection resulted in 30 to 37.5% protection of the mice. Passively transferred spleen cells did not produce detectable amounts of neutralizing antibody in the recipient mice except on day 2 after the transfer, when a low level of antibody was detected. These observations demonstrate the essential role of T cells in the postexposure prophylaxis of rabies in mice. The mechanisms of the failure of postexposure vaccination in nude mice are discussed.

BCG modulation of delayed type hypersensitivity, humoral response and acquired resistance after rabies vaccination

The immunopotentiating action of BCG was evaluated in rabies. The maximum enhancing effect on delayed type hypersensitivity (DTH) was obtained 14 days after rabies immunization when different BCG vaccination schedules were tested in mice. A stable form of specific sensitization to rabies antigen under the modulation of BCG pretreatment was obtained. High concentrations of rabies antigen were found to be inhibitory for the DTH reaction. Levels of protection were evaluated in rabies vaccination after BCG modulation. One single injection of rabies vaccine in BCG pretreated mice was as effective as two injections of rabies vaccine in normal mice. However, in the latter, increase of protection was correlated with the levels of neutralizing antibody. On the other hand, the BCG pretreated mice, protection was not associated with a significant increase in antibody. Pretreatment with BCG alone influenced the outcome of fixed rabies as well as street rabies by enhancing the natural resistance to rabies infection.

Enhancement of delayed-type hypersensitivity to Trypanosoma cruzi in mice treated with Mycobacterium bovis BCG and cyclophosphamide

C57BL/10J mice treated with Mycobacterium bovis BCG and cyclophosphamide were immunized with disrupted epimastigotes or with living blood trypomastigotes from Trypanosoma cruzi and assayed for delayed hypersensitivity by footpad testing with epimastigote antigens. Enhanced and lasting reactions were observed in mice pretreated with BCG or cyclophosphamide or both and immunized with epimastigotes. Whereas BCG pretreatment clearly reduced the mortality rates of mice immunized with living blood forms, no enhancement of the delayed hypersensitivity responses was observed in animals treated with BCG or cyclophosphamide or both before infection. The production of high levels of delayed hypersensitivity in the absence of infection and its adoptive transfer with cells could help to evaluate the participation of cell-mediated immunity in the protection against T. cruzi.

A mouse model of the pathogenesis and postexposure prophylaxis of rabies

A mouse model for the study of postexposure prophylaxis of rabies was established. Mice injected intramuscularly with a street strain of rabies virus were significantly protected from death by five daily 0.2-ml doses of inactivated rabies vaccine of chick embryo cell culture origin initiated immediately or 3 hr after infection. In these mice, a large amount of circulating interferon was induced as early as 1 hr after the first dose of vaccine and lasted until at least 12 hr but no such amount of interferon was induced by additional doses of vaccine. Serum antibody was first detected in the mice on day 6. It was noted that some of the surviving mice manifested an ataxia or paralysis of the legs. Increasing mortality rates were shown in mice treated with decreasing doses of the vaccine. Passive protection tests using concentrated IgG and IgM antibodies with equivalent neutralization titers showed that IgG antibody gave total protection when given 24 hr before the infection, while it was almost totally ineffective in reducing the mortality when given 2 days or more after infection. IgM antibody did not protect the mice even when given 24 hr before infection. These results suggest that interferon production is more important than antibody production in the initial stages of protection by postexposure vaccination. However, the mechanisms of postexposure prophylaxis in this model could not be explained only by the interferon produced by the vaccine and the possible contributions of additional mechanisms were suggested.

Mechanisms of protective immunogenicity of microbial vaccines: effects of cyclophosphamide pretreatment in Venezuelan encephalitis, Q fever and tularaemia

Administration of high-dose (250 mg/kg) cyclophosphamide (CY) to guinea-pigs and mice 3 days prior to immunization with inactivated vaccine derived from Venezuelan encephalitis virus (VE), Coxiella burnetii and Francisella tularensis resulted in accentuated and prolonged delayed-type hypersensitivity (DTH) and in vitro cellular immunity (CMI) to specific antigen. Humoral antibody were either absent or significantly lower in CY-pretreated animals compared to immunized non-pretreated controls. CY pretreatments precluded protection in the VE virus model, suggesting that resistance is related to antibody. In the Q fever model, the protective immunogenicity of vaccine was preserved or increased by CY pretreatment suggesting that cell-mediated immunity is the important factor. In the tularaemia bacterial system, there was a complex effect of CY pretreatment on the low-grade protection afforded by killed vaccine against virulent infection. These findings suggest that the inability of killed vaccines to induce high-grade resistance against tularaemia and Q fever may be due in part to a suppressive B cell response which is eliminated by CY. These studies have given useful information on the relative significance of components of the specific immune response and may lead to an increased understanding of the mechanisms of action of vaccines and adjuvants.

Production of DTH in the mouse to influenza virus: comparison with conditions for stimulation of cytotoxic T cells

The kinetics of sensitization and elicitation of delayed-type hypersensitivity in mice to both infectious and non-infectious preparations of influenza virus was found to be similar to that of some protein antigens and to other viruses. Sensitization was achieved without added adjuvant. Maximum DTH was elicited in the footpad 6 days after sensitization. Adoptive transfer experiments showed that the effector cells were in the Ig-negative fraction of the spleen and were sensitive to anti-theta and complement. A comparison was made of conditions for the generation of DTH activity with cytotoxic T cells. The route of inoculation was important. With a high dose (10(3) HAU) of virus, subcutaneous inoculation was the most efficient and intravenous injection the least efficient for sensitizing for DTH, whereas the reverse was found for cytotoxic T-cell generation. Second, treatment of mice with cyclophosphamide (Cy) had differential effects. Preinjection of a large dose (200 mg/kg) into mice 2 days before sensitization with virus resulted in an increase in the DTH response and a 90% reduction in cytotoxic T-cell activity in the spleens of the treated mice. The Cy-injected mice had reduced (70%) anti-haemagglutinin levels compared with the controls. This may be the explanation for the enhanced DTH response, since transfer of specific antibody to sensitized mice before injection of the eliciting virus substantially reduced the DTH response. Pretreatment with Cy did not affect the generation of DTH effector cells, since spleen cells from these and control mice had similar levels of activity.

Specificity, Ly phenotype, and H-2 compatibility requirements of effector cells in delayed-type hypersensitivity responses to murine influenza virus infection

Delayed-type hypersensitivity (DTH) to infectious and to noninfectious (UV-irradiated) influenza A viral preparations was measured in mice by the increase in footpad swelling 24 h after injection of the eliciting virus. DTH mice sensitized with noninfectious virus was elicited only by virus that shared hemagglutinin specificity with the sensitizing virus, whereas footpad injection of a given A-strain virus (A/WSN) could elicit DTH in mice sensitized with a variety of infectious A-strain viruses, including some not sharing hemagglutinin or neuraminidase specificities. The effector T cells generated in mice sensitized with either form of virus were sensitive to anti-Ly 1.1 serum and complement, but not to anti-Ly 2.1 serum and complement. Adoptive transfer of DTH was H-2 restricted. With spleen cells from mice sensitized subcutaneously with either infectious or noninfectious virus, sharing of the IA region was both necessary and sufficient for successful transfer to occur. Cells recovered from infected mouse lungs, and secondary effector cells generated in vitro transferred DTH if injected into the footpad with the eliciting virus. The effector cells had the Ly 1 phenotype, and, in both cases, the cells were I restricted. These results contrast with earlier findings that transfer of DTH to lymphocytic choriomeningitis virus infection required K- or D-region sharing between donor and recipient. Thus, the earlier hypothesis that multiplying infectious agents such as viruses would "alter" K- or D-coded, rather than I-coded, structures is not generally correct.

Recovery of immune responsiveness to rabies vaccine after treatment of mice with cyclophosphamide

Mice treated with cyclophosphamide (Cy) recovered the ability to mount delayed type hypersensitivity reactions within 3 days. By contrast, antibody production to a T cell independent antigen (E. coli lipopolysaccharide) and to human diploid cell strain rabies vaccine did not occur unless the immunization of Cy-treated mice was delayed for 7-10 days. No significant resistance to rabies infection was recorded at 10 days but was demonstrable if 14 days had elapsed between Cy treatment and vaccination.

Kinetics of different specific immunological parameters after rabies vaccination in mice

A significant protection to an intracerebral challenge of 70 mean lethal doses of a standard live rabies virus strain was obtained in BCG-pretreated mice or in normal mice which had been immunized with a single subcutaneous injection of a beta-propiolactone-inactivated rabies vaccine. Concomitantly, levels of delayed-type hypersensitivity (measured in vivo by the footpad test) and serum-neutralizing activity were evaluated at various times after immunization. All immune criteria were significantly augmented in the BCG-pretreated, rabies-immune mice as compared to normal, rabies-immune mice. However, peak levels of protection, delayed-type hypersensitivity, and serum-neutralizing activity did not occur at the same times. For instance, in the BCG-pretreated, rabies-immune mice, delayed-type hypersensitivity peaked on day 7, protection peaked on day 21, and serum-neutralizing activity peaked on day 60. In BCG-pretreated mice, which did not receive the rabies vaccine, positive delayed-type hypersensitivity, some protection, and serum neutralizing activity were observed 4 to 5 weeks after BCG pretreatment. The possible relationships between specific and nonspecific immunity provoked by rabies virus antigens, tissue culture cell-associated antigens (derived from the bovine fetal kidney cells in which the rabies virus was grown, and BCG are discussed.