Spontaneous cytokine gene expression in normal guinea pig blood and tissues

Molecular cloning and expression of the IL-10 gene from guinea pigs

The Guinea pig (Cavia porcellus) is one of the most relevant small animals for modeling human tuberculosis (TB) in terms of susceptibility to low dose aerosol infection, the organization of granulomas, extrapulmonary dissemination and vaccine-induced protection. It is also considered to be a gold standard for a number of other infectious and non-infectious diseases; however, this animal model has a major disadvantage due to the lack of readily available immunological reagents. In the present study, we successfully cloned a cDNA for the critical Th2 cytokine, interleukin-10 (IL-10), from inbred Strain 2 guinea pigs using the DNA sequence information provided by the genome project. The complete open reading frame (ORF) consists of 537 base pairs which encodes a protein of 179 amino acids. This cDNA sequence exhibited 87% homology with human IL-10. Surprisingly, it showed only 84% homology with the previously published IL-10 sequence from the C4-deficient (C4D) guinea pig, leading us to clone IL-10 cDNA from the Hartley strain of guinea pig. The IL-10 gene from the Hartley strain showed 100% homology with the IL-10 sequence of Strain 2 guinea pigs. In order to validate the only published IL-10 sequence existing in Genbank reported from C4D guinea pigs, genomic DNA was isolated from tissues of C4D guinea pigs. Amplification with various sets of primers showed that the IL-10 sequence reported from C4D guinea pigs contained numerous errors. Hence the IL-10 sequence that is being reported by us replaces the earlier sequence making our IL-10 sequence to be the first one accurate from guinea pig. Recombinant guinea pig IL-10 proteins were subsequently expressed in both prokaryotic and eukaryotic cells, purified and were confirmed by N-terminal sequencing. Polyclonal anti-IL-10 antibodies were generated in rabbits using the recombinant IL-10 protein expressed in this study. Taken together, our results indicate that the DNA sequence information provided by the genome project is useful to directly clone much needed cDNAs necessary to study TB in the guinea pig. The newly cloned guinea pig IL-10 cDNA and recombinant proteins will serve as valuable resources for immunological studies in the guinea pig model of TB and other diseases.

Cytokine patterns in a comparative model of arenavirus haemorrhagic fever in guinea pigs

Arenaviruses such as Lassa virus cause a spectrum of disease in humans ranging from mild febrile illness to lethal haemorrhagic fever. The contributions of innate immunity to protection or pathogenicity are unknown. We compared patterns of expression of cytokines of innate immunity in mild versus severe arenavirus disease using an established guinea pig model based on the macrophage-tropic arenavirus Pichinde virus (PICV). Cytokine transcripts were measured by using real-time RT-PCR in target organs and blood during mild infection (caused by PICV, P2 variant) and lethal haemorrhagic fever (caused by PICV, P18 variant). In the initial peritoneal target cells, virulent P18 infection was associated with significantly increased gamma interferon (IFN-gamma) and monocyte chemoattractant protein-1 (MCP-1, CCL2) mRNA levels relative to P2 infection. Peritoneal cells from P18-infected animals had decreased tumour necrosis factor alpha (TNF-alpha), interleukin (IL)-8 (CXCL-8) and IL-12p40 transcripts relative to mock-infected animals. Late in infection, P18-infected peripheral blood leukocytes (PBL) had decreased TNF-alpha, IFN-gamma, and regulated upon activation, normal T cell expressed and secreted (RANTES, CCL-5) cytokine transcripts relative to P2-infected PBL. We conclude that, in severe arenavirus disease, patterns of cytokine expression in the initially infected cells favour recruitment of additional target monocytes, while inhibiting some of their pro-inflammatory responses. Suppression rather than overexpression of pro-inflammatory cytokines accompanied the terminal shock in this model of arenavirus haemorrhagic fever.

Using guinea pigs in studies relevant to asthma and COPD

The guinea pig has been the most commonly used small animal species in preclinical studies related to asthma and COPD. The primary advantages of the guinea pig are the similar potencies and efficacies of agonists and antagonists in human and guinea pig airways and the many similarities in physiological processes, especially airway autonomic control and the response to allergen. The primary disadvantages to using guinea pigs are the lack of transgenic methods, limited numbers of guinea pig strains for comparative studies and a prominent axon reflex that is unlikely to be present in human airways. These attributes and various models developed in guinea pigs are discussed.

Monoclonal antibodies to guinea pig interferon-gamma: tools for cytokine detection and neutralization

We have generated polyclonal antisera and monoclonal antibodies against recombinant guinea pig IFN-gamma. These antibodies were used to inhibit the function of IFN-gamma in vitro and to establish a capture ELISA system for the detection and quantitation of this cytokine. Although recombinant protein expressed in E. coli was available in abundance, it was only of limited value to develop a capture ELISA which detects the native cytokine, since only a limited number of monoclonal antibodies reacted both with the recombinant and the native protein. Positive test results in an initial ELISA setup with recombinant IFN-gamma were not predictive for the detection of IFN-gamma from activated T-lymphocytes in the same assay. After evaluating several different combinations of rabbit antisera and monoclonal antibodies, an assay system was established which uses two mouse monoclonal antibodies as capture and detecting reagents. Three of the monoclonal antibodies and the rabbit antisera were able to block the function of guinea pig IFN-gamma when assayed in a luciferase reporter assay.

Development of respiratory syncytial virus "bronchiolitis" in guinea pigs does not reflect an allergic predisposition in the host

BACKGROUND

Respiratory syncytial virus (RSV) infection causes bronchiolitis in a minority of children. Using a guinea pig model to determine if an allergic predisposition in the host increases permissiveness to RSV infection or severity of experimental "bronchiolitis," we compared the effects of RSV inoculation between strain 2 (allergy-resistant) and strain 13 (allergy-susceptible) inbred animals.

METHODS

One month-old, juvenile guinea pigs were classified into four groups (eight guinea pigs per group): (group 1) strain 2, uninfected; (group 2) strain 13, uninfected; (group 3) strain 2, RSV infected; and (group 4) strain 13, RSV infected. Seven days after inoculation, the animals were studied by the following: viral plaque assays for quantification of intrapulmonary RSV; immunohistochemical localization of RSV antigens in lung tissue sections; physiologic assessment of airway obstruction and nonspecific bronchial hyperresponsiveness; quantitative histology of airway T lymphocytes, neutrophils, and eosinophils; and semiquantitative reverse transcriptase-polymerase chain reaction for levels of messenger RNA expression of a panel of proinflammatory cytokines and chemokines.

RESULTS

Significantly higher titers of replicating RSV were isolated from the lungs of strain 13 vs strain 2 animals (p < or = 0.001). The two guinea pig strains showed similar cell types with positive viral immunostaining; RSV-associated changes in airway obstruction and nonspecific bronchial hyperresponsiveness; airway T cells, neutrophils, and eosinophils; and messenger RNA expression of cytokines and chemokines.

CONCLUSIONS

Strain 13 guinea pigs show increased pulmonary RSV replication than strain 2 animals, but this increased permissiveness to the virus is not reflected by more severe virus-induced changes in airway obstruction, nonspecific bronchial hyperresponsiveness, airway inflammation, or gene expression of proinflammatory cytokines and chemokines.

Combined intrarectal/intradermal inoculation of recombinant Mycobacterium bovis bacillus Calmette-Guérin (BCG) induces enhanced immune responses against the inserted HIV-1 V3 antigen

The development of a successful recombinant Mycobacterium bovis bacillus Calmette-Guérin (rBCG) vector-based vaccine for human immunodeficiency virus type 1 (HIV-1) requires the induction of high levels of HIV-1-specific immunity while at the same time maintaining immunity to tuberculosis. To examine a combined vaccination strategy for enhancement of immune responses specific for HIV-1, guinea pigs were inoculated with either a single or combination intradermal (i.d.), intrarectal (i.r.) and intranasal (i.n.) administration of rBCG-pSOV3J1 which secretes a chimeric protein of HIV-1 V3J1 peptide and alpha-antigen. Significant level of delayed-type hypersensitivity to both V3J1 peptide and tuberculin was induced in guinea pigs inoculated with human doses of rBCG-pSOV3J1 by a combination of intrarectal and intradermal routes. Guinea pigs inoculated by combined routes also had significantly higher titers of HIV-1-specific serum IgG and IgA compared with those animals immunized only intrarectally, which led to the enhanced neutralization activity against HIV-1(MN). In addition, the induction of high levels of IFNgamma and interleukin-2 (IL-2) mRNA in PBMC, splenocytes, and intraepithelial lymphocytes from the immunized animals was detected until at least 110 weeks post-inoculation. These results suggest that enhanced immune responses specific for HIV-1 are efficiently induced by combined intrarectal and intradermal immunization with rBCG-HIV, and antigen-specific Th1-type memory cells are maintained for more than 2 years in the immunized animals. Thus, inoculation with rBCG-HIV by combined routes represents an effective vaccination strategy to elicit high levels of HIV-1-specific immune responses.

Dynamics of gamma interferon, interleukin-12 (IL-12), IL-10, and transforming growth factor beta mRNA expression in primary Mycobacterium bovis BCG infection in guinea pigs measured by a real-time fluorogenic reverse transcription-PCR assay

The guinea pig has been utilized as a model for studying infectious diseases because its reactions closely resemble those of humans biologically and immunologically. However, the cytokine responses in this animal remain to be studied. Initially, we established a quantitative assay using a real-time reverse transcription-PCR (RT-PCR) to measure guinea pig gamma interferon (IFN-gamma), interleukin-12 (IL-12), IL-10, and transforming growth factor beta (TGF-beta) mRNA. By preparing primer-fluorogenic probe sets for these cytokines and standard RNA templates corresponding to the target sequence of each cytokine, we obtained linear standard curves essential for quantitative determination. In guinea pigs immunized by intradermal (i.d.) vaccination with the Tokyo strain of Mycobacterium bovis BCG (0.1 mg) or else hyperimmunized with the same vaccine (10 mg) given intravenously (i.v.), peripheral blood mononuclear cells (PBMCs) at 4 weeks showed an increase in IFN-gamma mRNA expression in the latter but not the former animals. However, at week 10, IFN-gamma mRNA expression was markedly elevated in PBMCs, spleen cells, and cells in bronchoalveolar lavage fluid in both the i.d.- and the i.v.-immunized animals, the level of expression being 10 times higher in the latter. In contrast, the expression levels of IL-12 mRNA in PBMCs, spleen cells, and BAL cells were not enhanced in either group at 10 weeks postimmunization. The expression of IL-10 and TGF-beta increased slightly only in PBMCs. Regardless of differences in the levels of cytokine responses, the magnitudes of the purified protein derivative of tuberculin-specific delayed-type hypersensitivity (DTH) skin reactions for the two groups did not differ significantly at 8 weeks postvaccination. In this study, we quantitatively measured IL-10, IL-12, TGF-beta, and IFN-gamma mRNA in BCG-immunized guinea pigs and showed that the level of IFN-gamma mRNA expression does not necessarily reflect the magnitude of the DTH response, suggesting that there may be an intricate relationship between protective immunity, the level of IFN-gamma, and the DTH response. Thus, our quantitative assay would be of use for the development of vaccines using guinea pig models.

Molecular cloning and functional characterization of guinea pig IL-12

IL-12 is a heterodimeric cytokine that plays a central role in cell-mediated immunity. We cloned complete cDNAs of guinea pig homologues of IL-12 p35 and p40 subunits, and compared their functional properties with human IL-12. Both p35 and p40 mRNA were constitutively expressed in the testis and peritoneal macrophages. On immunoblotting, anti-guinea pig p40 antibody detected the constitutive expression of p40 protein in the testis, while in macrophages it was induced in response to lipopolysaccharide. An unidentified 200-kDa macromolecule was also expressed in the testis. All recombinant hybrid heterodimer p70 (guinea pig p70, human p70 and two interspecies heterodimers) exerted proliferative activity toward concanavalin A-primed guinea pig and human lymphoblasts in a dose-dependent manner. A similar tendency was observed in IFN-gamma production in IL-2-treated human lymphocytes. All hybrid heterodimers also induced IFN-gamma mRNA from IL-2-treated guinea pig splenocytes. Thus, unlike the current concept that the p35 subunit determines the species incompatibility of IL-12 in humans and mice, p35 has marginal ability to define its species-specific functional expression between humans and guinea pigs. In addition, constitutive expression of IL-12 or related molecules in the testis indicated a potential role of this molecule in regulation of physiological or pathophysiological conditions in the reproductive system.

Pathogenesis of maternal-fetal syphilis revisited

Although congenital syphilis has been recognized for several centuries and an efficient treatment with penicillin became available more than a half-century ago, the disease is still with us. Inability to culture in vitro the causative agent, Treponema pallidum, and the lack of an adequate animal model have prevented exploration of the various immunopathological events affecting the natural course of congenital infection. The purpose of this review is to analyze the disease in the context of recent knowledge acquired from human and experimental animals, particularly from the guinea pig model of congenital and neonatal syphilis, and to describe how the infection interacts with the maternal-fetal unit and how it is further modulated by the conceptus' ontogenic development. We also attempt to elucidate several old immunologic concepts and misconceptions that have remained unchallenged for too long.

Cytokine gene expression in skin of susceptible guinea-pig infected with Treponema pallidum

Using a semi-quantitative multiplex reverse transcription-polymerase chain reaction assay, we examined cytokine mRNA expression for interleukin-1alpha (IL-1alpha), IL-2, IL-10, IL-12p40, tumour necrosis factor-alpha (TNF-alpha) and transforming growth factor-beta (TGF-beta) in skin samples obtained from C4-deficient (C4D) guinea-pigs inoculated intradermally with virulent Treponema pallidum (VTP). Controls included unmanipulated animals, guinea-pigs injected with T. pallidum-free rabbit inflammatory testicular fluid (ITF) alone, or mixed with heat-killed organisms (HKTP). The expression of IL-1alpha, IL-12p40, and TNF-alpha mRNA [T helper type 1 (Th1)] remained within the normal range in both infected and control animals throughout the experimental period. However, a significant increase (P<0.05) in IL-10 mRNA (Th2) was found exclusively in the VTP-inoculated animals from 3 to 30 days post-infection. Another unique characteristic of the inflammatory response in infected guinea-pigs was the appearance, between 11 and 30 days post-inoculation, of a substantial number of eosinophils in addition to infiltrating mononuclear cells. The results showed a local Th2 response which is consistent with an inadequate immune response. This is reflected by the lengthy and incomplete clearance of the pathogen from the local site of entry and the chronic infection of distant organs.