Anatomical description and morphometry of the skeleton of the common marmoset (Callithrix jacchus).

Callithrix jacchus (common marmoset) is regularly used in biomedical research, including for studies involving the skeleton. To support these studies, skeletons of healthy animals that had been euthanized for reasons not interfering with skeletal anatomy were prepared. The marmoset dental formula 2I-1C-3P-2M of each oral quadrant is atypical for New World monkeys which commonly possess a third molar. Seven cervical, 12-13 thoracic, 7-6 lumbar, 2-3 sacral and 26-29 caudal vertebrae are present, the thoracolumbar region always comprising 19 vertebrae. A sigmoid clavicle connects the scapula with the manubrium of the sternum. Depending on the number of thoracic vertebrae, 4-5 sternebrae are located between the manubrium and xiphoid process. Wide interosseous spaces separate the radius from the ulna, and the tibia from the fibula. A small sesamoid bone is inserted in the m. abductor digiti primi longus at the medial border of the carpus, a pair of ovoid sesamoid bones is located at the palmar/plantar sides of the trochleae of each metapodial bone, and round fabellae articulate with the proximal surfaces of the femoral condyles. Male marmosets possess a small penile bone. Both the front and hind feet have five digits. The hallux possesses a flat nail, whereas all other digits present curved claws. Interestingly, a central bone is present in both the carpus and tarsus. This study provides a description and detailed illustrations of the skeleton of the common marmoset as an anatomical guide for further biomedical research.

Single subcutaneous dosing of cefovecin in rhesus monkeys (Macaca mulatta): a pharmacokinetic study.

Cefovecin is a third-generation cephalosporin approved for antibacterial treatment with a 14-day dosing interval in dogs and cats. This antibiotic may also be useful for zoo and wildlife veterinary medicine, because of its broad spectrum and long duration of activity. The aim of the study was to determine whether cefovecin is a suitable antibiotic to prevent skin wound infection in rhesus monkeys. Therefore, the pharmacokinetics (PK) of cefovecin after a single subcutaneous injection at 8 mg/kg bodyweight in four rhesus monkeys (Macaca mulatta) and sensitivity of bacterial isolates from fresh skin wounds were determined. After administration, blood, urine, and feces were collected, and concentrations of cefovecin were determined. Further, the minimum inhibitory concentrations (MIC) for bacteria isolated from fresh skin wounds of monkeys during a health control program were determined. The mean maximum plasma concentration (C(max) ) of cefovecin was 78 µg/mL and was achieved after 57 min. The mean apparent long elimination half-life (t½) was 6.6 h and excretion occurred mainly via urine. The MIC for the majority of the bacteria examined was >100 µg/mL. The PK of cefovecin in rhesus monkeys is substantially different than for dogs and cats. Cefovecin rapidly reached C(max) which however was lower than most of the MIC levels and with a very short t½. Therefore, cefovecin is not recommended for treating skin wounds in rhesus monkeys.

Immunogenicity in rhesus of the Plasmodium vivax mosquito stage antigen Pvs25H with Alhydrogel and Montanide ISA 720.

Pvs25 is an ookinete surface protein from Plasmodium vivax that is the target of transmission-blocking antibodies. Two immunogenicity trials in rhesus monkeys with a recombinant form of the protein, Pvs25H, were undertaken. Monkeys were vaccinated with Pvs25H adsorbed to Alhydrogel or emulsified in Montanide ISA 720 at 0, 4 and 27 weeks (study 1) or in Montanide ISA 720 at 0 and 18 weeks (study 2) with 1.5 or 15 microg Pvs25H in 0.1 or 0.5 mL of emulsion (four combinations). Immunogenicity was assessed by ELISA and by membrane-feeding experiments using P. vivax-infected blood from human volunteers (studies 1 and 2) or from chimpanzees (study 1). Both vaccine trials generated antibodies that blocked transmission of P. vivax to mosquitoes. Antibody titres and transmission blocking were higher with Montanide ISA 720 than with Alhydrogel in the first trial and with the 15 microg Pvs25H/0.5 mL ISA 720 combination in the second trial.

Dominant antibody responses to Fucalpha1-3GalNAc and Fucalpha1-2Fucalpha1-3GlcNAc containing carbohydrate epitopes in Pan troglodytes vaccinated and infected with Schistosoma mansoni.

The development of the humoral anti-glycan immune response of chimpanzees, either or not vaccinated with radiation-attenuated Schistosoma mansoni cercariae, was followed during 1 year after infection with S. mansoni. During the acute phase of infection both the vaccinated and the control chimpanzees produce high levels of immunoglobulin G (IgG) antibodies against carbohydrate structures that are characteristic for schistosomes carrying the Fucalpha1-3GalNAc and Fucalpha1-2Fucalpha1-3GlcNAc motifs, but not to the more widespread occurring structures GalNAcbeta1-4GlcNAc, GalNAcbeta1-4(Fucalpha1-3)GlcNAc, and Galbeta1-4(Fucalpha1-3)GlcNAc (Lewis(x)). In addition, high levels of IgM antibodies were found against the trimeric Lewis(x) epitope. Apparently, the schistosome-characteristic carbohydrate structures are dominant epitopes in the anti-glycan humoral immune response of the chimpanzees. All chimpanzees showed an increase in the level of antibodies against most of the carbohydrate structures tested directly after vaccination, peaking at challenge time and during the acute phase of infection. With the exception of anti-F-LDN antibody responses, the anti-carbohydrate antibody responses upon schistosome infection of the vaccinated animals were muted in comparison to the control animals.

A prime-boost immunisation regimen using DNA followed by recombinant modified vaccinia virus Ankara induces strong cellular immune responses against the Plasmodium falciparum TRAP antigen in chimpanzees.

Two chimpanzees were vaccinated intramuscularly against malaria using plasmid DNA expressing the pre-erythrocytic antigens thrombospondin related adhesion protein (PfTRAP) and liver stage specific antigen-1 (PfLSA-1) of Plasmodium falciparum together with GM-CSF protein. A recombinant modified vaccinia virus Ankara (MVA) expressing PfTRAP was injected intramuscularly 6 weeks later to boost the immune response. This sequence of antigen delivery induced a specific and long-lasting T cell and antibody response to PfTRAP as detected by ELISPOT assay and ELISA. Antibody responses were detected after four DNA injections, and were boosted by injection of recombinant MVA expressing PfTRAP. Interferon-gamma secreting antigen-specific T cells were detected in both animals, but only after boosting with recombinant MVA. By screening a panel of PfTRAP-derived peptides, an epitope was identified that was recognized by cytotoxic T lymphocytes in one of the chimpanzees studied. T cells specific for this epitope were present in PBMCs and liver-infiltrating lymphocytes at a frequency of between 1 in 200 and 1 in 500. The high immunogenicity of this prime-boost regimen in chimpanzees supports further assessment of this delivery strategy for the induction of protection against P. falciparum malaria in humans.

Divergent effect of bacillus Calmette-Guérin (BCG) vaccination on Mycobacterium tuberculosis infection in highly related macaque species: implications for primate models in tuberculosis vaccine research.

Despite the widespread use of bacillus Calmette-Guérin vaccination, Mycobacterium tuberculosis infection remains globally the leading cause of death from a single infectious disease. The complicated and often protracted dynamics of infection and disease make clinical trials to test new tuberculosis vaccines extremely complex. Preclinical selection of only the most promising candidates is therefore essential. Because macaque monkeys develop a disease very similar to humans, they have potential to provide important information in addition to small animal models. To assess the relative merits of rhesus and cynomolgus monkeys as screens for tuberculosis vaccines, we compared the efficacy of bacillus Calmette-Guérin vaccination and the course of infection in both species. Unvaccinated rhesus and cynomolgus monkeys both developed progressive disease with high levels of C-reactive protein, M. tuberculosis-specific IgG, and extensive pathology including cavitation and caseous necrosis. Bacillus Calmette-Guérin vaccination protected cynomolgus almost completely toward the development of pathology, reflected in a striking 2-log reduction in viable bacteria in the lungs compared with nonvaccinated animals. Rhesus, on the other hand, were not protected efficiently by the bacillus Calmette-Guérin. The vaccinated animals developed substantial pathology and had negligible reductions of colony-forming units in the lungs. Comparative studies in these closely related species are likely to provide insight into mechanisms involved in protection against tuberculosis.

Cellular and humoral immune responses and protection against schistosomes induced by a radiation-attenuated vaccine in chimpanzees.

The radiation-attenuated Schistosoma mansoni vaccine is highly effective in rodents and primates but has never been tested in humans, primarily for safety reasons. To strengthen its status as a paradigm for a human recombinant antigen vaccine, we have undertaken a small-scale vaccination and challenge experiment in chimpanzees (Pan troglodytes). Immunological, clinical, and parasitological parameters were measured in three animals after multiple vaccinations, together with three controls, during the acute and chronic stages of challenge infection up to chemotherapeutic cure. Vaccination induced a strong in vitro proliferative response and early gamma interferon production, but type 2 cytokines were dominant by the time of challenge. The controls showed little response to challenge infection before the acute stage of the disease, initiated by egg deposition. In contrast, the responses of vaccinated animals were muted throughout the challenge period. Vaccination also induced parasite-specific immunoglobulin M (IgM) and IgG, which reached high levels at the time of challenge, while in control animals levels did not rise markedly before egg deposition. The protective effects of vaccination were manifested as an amelioration of acute disease and overall morbidity, revealed by differences in gamma-glutamyl transferase level, leukocytosis, eosinophilia, and hematocrit. Moreover, vaccinated chimpanzees had a 46% lower level of circulating cathodic antigen and a 38% reduction in fecal egg output, compared to controls, during the chronic phase of infection.

Interleukin-10 regulates the tissue factor activity of monocytes in an in vitro model of bacterial endocarditis.

Monocytes are important effector cells in the pathogenesis of bacterial endocarditis since they provide the tissue factor that activates the coagulation system and maintains established vegetations. Monocytes secrete cytokines that can modulate monocyte tissue factor activity (TFA), thereby affecting the formation and maintenance of vegetations. In this study, we show that monocytes cultured for 4 h on a Streptococcus sanguis-infected fibrin matrix mimicking the in vivo vegetational surface express high levels of TFA. This was accompanied by secretion of the proinflammatory cytokines tumor necrosis factor alpha (TNF-alpha), interleukin-1 alpha (IL-1 alpha), and IL-1 beta. After a 24-h incubation period the anti-inflammatory cytokine IL-10 could also be detected. Our data show that, whereas TNF-alpha and IL-1 have a minor role in the induction of TFA by monocytes cultured on a fibrin matrix, TNF-alpha but not IL-1 plays an important role in the induction of IL-10 by these cells. In turn, our data show that IL-10 is an important factor in the downregulation of monocyte TFA. In summary, we conclude that IL-10 is an important factor in the control of monocyte TFA in endocardial vegetations.

Transforming growth factor-beta suppresses interferon-gamma-induced toxoplasmastatic activity in murine macrophages by inhibition of tumour necrosis factor-alpha production.

Activation of macrophages plays an important role in the host resistance against intracellular pathogens. Various mechanisms are employed to control the activation processes and limit tissue damage by factors produced by activated macrophages. One of these mechanisms is the production of macrophage-deactivating cytokines, such as tumour growth factor (TGF)-beta. The present study concerns the effects of TGF-beta on interferon (IFN)-gamma-induced activation of murine macrophages with respect to induction of toxoplasmastatic activity, and production of tumour necrosis factor (TNF)-alpha, prostaglandin E2 (PGE2) and reactive nitrogen intermediates (RNI). IFN-gamma activation of macrophages resulted in inhibition of T. gondii proliferation [mean fold increase (FI) = 1.8, control mean FI = 7.0]; polymyxin B had no effect on this activation. The IFN-gamma-induced toxoplasmastatic activity of macrophages was inhibited by TGF-beta (mean FI = 6.3), which was also found for the IFN-gamma-induced production of TNF-alpha, RNI and PGE2 by macrophages. We found that PGE2, which has macrophage deactivating properties, was not involved in the inhibition of macrophage activation by TGF-beta. The deactivating activities of TGF-beta on the IFN-gamma-induced toxoplasmastatic activity and production of RNI are mediated by inhibition of production of TNF-alpha. Addition of exogenous TNF-alpha during the incubation of macrophages with IFN-gamma and TGF-beta abrogated the deactivating activity of TGF-beta. In sum, the results demonstrate that inhibition of TNF-alpha production is a key factor in the TGF-beta-induced suppression of macrophage activation with respect to toxoplasmastatic activity and RNI production.

Antibodies to glycans dominate the host response to schistosome larvae and eggs: is their role protective or subversive?

Multiple exposures of chimpanzees to the radiation-attenuated schistosome vaccine provoked a strong parasite-specific cellular and humoral immune response. Specific IgM and IgG were directed mainly against glycans on antigens released by cercariae; these were also cross-reactive with soluble antigens from larvae, adult worms, and eggs. Egg deposition was the major antigenic stimulus after challenge of vaccinated and control chimpanzees with normal parasites, eliciting strong antiglycan responses to egg secretions. Glycan epitopes recognized included LacdiNAc, fucosylated LacdiNAc, Lewis(X) (weakly), and those on keyhole limpet hemocyanin. Antibodies to peptide epitopes became prominent only during the chronic phase of infection, as glycan-specific IgM and IgG decreased. Because of their intensity and cross-reactivity, the antiglycan responses resulting from infection could be a smoke screen to subvert the immune system away from more vulnerable larval peptide epitopes. Their occurrence in humans might explain the long time required for antischistosome immunity to build up after infection.

Protection against Plasmodium falciparum malaria in chimpanzees by immunization with the conserved pre-erythrocytic liver-stage antigen 3.

In humans, sterile immunity against malaria can be consistently induced through exposure to the bites of thousands of irradiated infected mosquitoes. The same level of protection has yet to be achieved using subunit vaccines. Recent studies have indicated an essential function for intrahepatic parasites, the stage after the mosquito bite, and thus for antigens expressed during this stage. We report here the identification of liver-stage antigen 3, which is expressed both in the mosquito and liver-stage parasites. This Plasmodium falciparum 200-kilodalton protein is highly conserved, and showed promising antigenic and immunogenic properties. In chimpanzees (Pan troglodytes), the primates most closely related to humans and that share a similar susceptibility to P. falciparum liver-stage infection, immunization with LSA-3 induced protection against successive heterologous challenges with large numbers of P. falciparum sporozoites.

Infection of a canine macrophage cell line with leishmania infantum: determination of nitric oxide production and anti-leishmanial activity.

We have previously shown that resistance to Leishmania infantum in dogs is associated with a Th1 type of immune response. In this study, we use a canine macrophage cell line (030-D) that can readily be infected with this protozoan parasite. Our aim is to further characterize the effector mechanisms involved in killing of Leishmania parasite in dogs. We observed that activation of 030-D cells by incubation with a supernatant derived from a Leishmania-specific T cell line containing IFN-gamma, TNF-alpha and interleukin-2 (IL-2) resulted in enhanced nitric oxide (NO) production by these cells. In addition, we observed enhanced anti-leishmanial activity of infected 030-cells after activation. Both, NO production and anti-leishmanial activity were abrogated by addition of L-N(G)-nitroargininemethyl ester (L-NAME), an analogue of L-arginine. Thus, NO play an important role in the anti-leishmanial activity of these canine macrophages. We propose the infection of the 030-D cell line as a good in vitro model to further investigate parasite-host cell interactions in dogs, a natural host of Leishmania parasites.

Interleukin-10 has different effects on proliferation of Listeria monocytogenes in livers and spleens of mice.

The aim of this study was to investigate the effect of interleukin-10 (IL-10) on the course of Listeria monocytogenes infection in naive and immune mice. Treatment with IL-10 during the course of a primary infection significantly decreased the number of bacteria in the spleen and did not affect the number in the liver. During a secondary infection in immune mice treated with IL-10, the number of bacteria was significantly lower in the spleen but significantly higher in the liver in comparison to mock-treated immune mice. IL-10 treatment during a primary Listeria infection decreased the concentration of gamma interferon (IFN-gamma) in plasma and the toxoplasmastatic activity of macrophages, whereas it increased the percentage of mildly CD3-positive T cells in the spleen. During a secondary infection, the concentration of IFN-gamma in plasma was decreased on day 1 but remained unaffected during later days of infection. From these results, we conclude that IL-10 has different effects on the proliferation of L. monocytogenes in the spleen and liver during primary and secondary Listeria infections.

Expression of beta-defensin-1 in chimpanzee (Pan troglodytes) airways.

In human airways, beta-defensins function in the elimination of various pathogens. They have been identified in a wide range of species. Here we report the identification and expression of chimpanzee beta-defensin-1 (cBD1), which is a homolog of human beta-defensin-1, in chimpanzee airways and skin. The cBD1 cDNA sequence differs by only one synonymous nucleotide substitution compared to the human cDNA sequence. In situ hybridization revealed that in lung tissue beside alveolar macrophages also airway epithelial cells, endothelial cells and type II pneumocytes express cBD1 mRNA. In skin, cBD1 mRNA was expressed in keratinocytes and endothelial cells. Together, these results show similarity in structure and expression pattern and perhaps in function.

Reactivity of human T-lymphocyte-specific antibodies with peripheral blood mononuclear cells and spleen of Aotus azarae ssp. boliviensis (owl monkey).

Aotus monkeys offer one of the few models that can be used for the evaluation of the immunogenicity and efficacy of new vaccine candidates against the human malarias, Plasmodium falciparum and Plasmodium vivax. However, the tools available for evaluation of the immune responses in these New World primates are still limited. In the present study, a previously selected set of monoclonal antibodies that were raised against human T cell determinants and were reactive with at least one other primate species was investigated for its reactivity with Aotus lymphocytes using FACS analysis, indirect immunofluorescence (IFA) and immunohistochemistry. From a panel of 19 mAb, six were found to react consistently with Aotus lymphocytes using FACS analysis. Further evaluation of the mAb using IFA confirmed these findings. Analysis of the selected mAb on spleen sections of Aotus monkeys identified one anti-CD4 and one anti-CD8 mAb that can be used for immunohistochemical studies. The set of mAb identified in this study can be used for the detection of various T lymphocyte markers in peripheral blood and in tissues of Aotus monkeys. Together with data published by others, mAb are now identified for detection of six different markers of Aotus T lymphocytes. These mAb are very valuable for the characterisation of immune responses after vaccination and infection in the Aotus malaria models.

Different effect of granulocyte colony-stimulating factor or bacterial infection on bone-marrow cells of cyclophosphamide-treated or irradiated mice.

In the present study, the effect of treatment with granulocyte colony-stimulating factor (G-CSF) on cellular composition of the bone marrow and the number of circulating leucocytes of granulocytopenic mice, whether or not infected with Staphylococcus aureus, was assessed. With two monoclonal antibodies, six morphologically distinct cell populations in the bone marrow could be characterised and quantitated by two-dimensional flow cytometry. Granulocytopenia was induced by cyclophosphamide or sublethal irradiation. Cyclophosphamide predominantly affected the later stages of dividing cells in the bone marrow resulting in a decrease in number of granulocytic cells, monocytic cells, lymphoid cells and myeloid blasts. G-CSF administration to cyclophosphamide-treated mice increased the number of early blasts, myeloid blasts and granulocytic cells in the bone marrow, which indicates that this growth factor stimulates the proliferation of these cells in the bone marrow. During infection in cyclophosphamide-treated mice the number of myeloid blasts increased. However, when an infection was induced in cyclophosphamide and G-CSF-treated mice, the proliferation of bone-marrow cells was not changed compared to that in noninfected similarly treated mice. Sublethal irradiation affected all bone-marrow cell populations, including the early blasts. G-CSF-treatment of irradiated mice increased only the number of myeloid blasts slightly, whereas an infection in irradiated mice, whether or not treated with G-CSF, did not affect the number of bone-marrow cells. Together, these studies demonstrated that irradiation affects the early blasts and myeloid blasts in the bone marrow more severely than treatment with cyclophosphamide. Irradiation probably depletes the bone marrow from G-CSF-responsive cells, while cyclophosphamide spared G-CSF responsive cells, thus enabling the enhanced G-CSF-mediated recovery after cyclophosphamide treatment. Only in these mice, bone marrow recovery is followed by a strong mobilisation of mature granulocytes and their band forms from the bone marrow into the circulation during a bacterial infection.

Anti-CD14 monoclonal antibodies inhibit the production of tumor necrosis factor alpha and interleukin-10 by human monocytes stimulated with killed and live Haemophilus influenzae or Streptococcus pneumoniae organisms.

In previous studies, we have shown that intact, heat-killed, gram-negative bacteria (GNB) and gram-positive bacteria (GPB) can stimulate the production of various proinflammatory and anti-inflammatory cytokines. The objective of the present study was to investigate whether the production of tumor necrosis factor alpha (TNF) and interleukin-10 (IL-10) by human monocytes stimulated by intact heat-killed or live Haemophilus influenzae or Streptococcus pneumoniae is mediated by CD14. Two anti-CD14 monoclonal antibodies (MAbs) were used to study the interaction between human monocytes and bacteria; lipopolysaccharide (LPS) was used to validate the effect of anti-CD14 MAb. MAb 18E12 decreased significantly TNF and IL-10 production upon stimulation with LPS or heat-killed bacteria and TNF production during stimulation by live bacteria. MAb My-4 decreased production of TNF and IL-10 by monocytes stimulated with LPS, IL-10 but not TNF production upon stimulation with heat-killed H. influenzae, and production of neither TNF nor IL-10 upon stimulation with S. pneumoniae. Together, these results led to the conclusion that CD14 is involved in the recognition and stimulation of human monocytes by intact GNB and GPB. Consequentially, the option for adjunctive treatment of severe infections with anti-CD14 MAb is postulated.

High-level expression of Plasmodium vivax apical membrane antigen 1 (AMA-1) in Pichia pastoris: strong immunogenicity in Macaca mulatta immunized with P. vivax AMA-1 and adjuvant SBAS2.

The apical membrane antigen 1 (AMA-1) family is a promising family of malaria blood-stage vaccine candidates that have induced protection in rodent and nonhuman primate models of malaria. Correct conformation of the protein appears to be essential for the induction of parasite-inhibitory responses, and these responses appear to be primarily antibody mediated. Here we describe for the first time high-level secreted expression (over 50 mg/liter) of the Plasmodium vivax AMA-1 (PV66/AMA-1) ectodomain by using the methylotrophic yeast Pichia pastoris. To prevent nonnative glycosylation, a conservatively mutagenized PV66/AMA-1 gene (PV66Deltaglyc) lacking N-glycosylation sites was also developed. Expression of the PV66Deltaglyc ectodomain yielded similar levels of a homogeneous product that was nonglycosylated and was readily purified by ion-exchange and gel filtration chromatographies. Recombinant PV66Deltaglyc43-487 was reactive with conformation-dependent monoclonal antibodies. With the SBAS2 adjuvant, Pichia-expressed PV66Deltaglyc43-487 was highly immunogenic in five rhesus monkeys, inducing immunoglobulin G enzyme-linked immunosorbent assay titers in excess of 1:200,000. This group of monkeys had a weak trend showing lower cumulative parasite loads following a Plasmodium cynomolgi infection than in the control group.

Endogenous interleukin-4 does not suppress the resistance against a primary or a secondary Listeria monocytogenes infection in mice.

Interleukin-4 (IL-4), a cytokine produced by T-helper 2 (Th2) cells, can inhibit the development of T-helper 1 (Th1) cells, which results in a decreased release of cytokines by the latter. As interferon-gamma (IFN-gamma), produced by Th1 cells, is involved in the resistance against a Listeria monocytogenes infection, the role of endogenously formed IL-4 during a Listeria infection in mice was investigated. Neutralization of endogenously formed cytokines by subcutaneously injected alginate-encapsulated monoclonal antibody (MoAb)-forming cells results in high antibody titres in the circulation over a long time period. The aim of the present study was to reevaluate the effect of neutralization of IL-4 during a primary Listeria infection and to investigate the role of IL-4 during a secondary infection in mice using encapsulated MoAb-forming cells. During the course of a primary infection in mice given anti-IL-4 antibody-forming cells (anti-IL-4-FC), the number of Listeria found in the liver and spleen was comparable to that found in control mice given anti-beta-galactosidase antibody-forming cells (anti-beta-gal-FC). Activation of macrophages measured by inhibition of Toxoplasma gondii proliferation and the release of reactive nitrogen intermediates (RNI) was not affected by anti-IL-4-FC treatment during infection. Furthermore, during a secondary L. monocytogenes infection the number of bacteria in the liver and spleen of anti-IL-4-treated immune mice was comparable to anti-beta-gal-FC-treated, control, immune mice. The concentration of IFN-gamma in plasma of anti-IL-4-treated immune mice was similar to that of control immune mice. Taken together, these findings demonstrate that neutralization of endogenously formed IL-4 does not affect resistance to a primary or a secondary L. monocytogenes infection in mice.

Effect of granulocyte-macrophage colony-stimulating factor on the number of leucocytes and course of Listeria monocytogenes infection in naive and leucocytopenic mice.

This study concerns the effect of recombinant murine granulocyte-macrophage colony-stimulating factor (GM-CSF) on the number of circulating leucocytes, activation of peritoneal macrophages and proliferation of Listeria monocytogenes in various organs of naive and leucocytopenic mice. Mice were rendered leucocytopenic by sublethal total body irradiation or cyclophosphamide treatment. GM-CSF treatment enhanced the number of granulocytes and monocytes in peripheral blood during L. monocytogenes infection in naive mice, but not in irradiated or cyclophosphamide-treated mice. In naive mice, irradiated and cyclophosphamide-treated mice, GM-CSF did not affect the course of L. monocytogenes infection in thigh muscle, spleen and liver. However, GM-CSF treatment significantly increased the number of macrophages in the peritoneal cavity of naive mice during infection; these macrophages were more enlarged and showed a higher frequency of binucleated and multinucleated cells relative to non-GM-CSF-treated mice. Together, these results demonstrated that GM-CSF increased the number of circulating granulocytes and monocytes, and the number of peritoneal macrophages during infection with L. monocytogenes in naive mice, but did not affect the course of the infection in thigh muscle, spleen or liver of these mice. In leucocytopenic mice, however, GM-CSF did not affect the number of circulating phagocytes, which explains that this factor had no effect on the proliferation of the bacteria in the various organs.