Treatment with anti-interleukin-10 monoclonal antibody enhances early resistance to but impairs complete clearance of Listeria monocytogenes infection in mice

Mice that received an anti-interleukin-10 (anti-IL-10) neutralizing monoclonal antibody (MAb) (SXC-1) prior to infection with Listeria monocytogenes initially demonstrated resistance to the infection, as indicated by reduced recovery of L. monocytogenes from their spleens and livers during the first 5 days after challenge. Anti-IL-10 MAb-treated mice then demonstrated reduced resistance during the later stage of infection, as indicated by persistent infection with L. monocytogenes in their livers 11 days after challenge. Aspartate aminotransferase (AST) levels (a measure of liver damage) in the sera of control mice increased between 1 and 5 days after challenge, while anti-IL-10 MAb-treated mice maintained lower AST levels. At 7 days after challenge, AST levels in the sera of control mice decreased as the numbers of organisms declined. In contrast, AST levels increased as the infections persisted in anti-IL-10 MAb-treated mice. The AST levels in serum reflected liver histopathology as anti-IL-10 MAb-treated mice exhibited fewer granulomatous lesions and less necrosis of liver tissue than the control mice during the first 5 days after challenge. Anti-IL-10 MAb treatment altered the expression of inflammatory cytokine mRNAs during L. monocytogenes infection. Control MAb-treated mice exhibited increased expression of tumor necrosis factor alpha and granulocyte-macrophage colony-stimulating factor mRNA in their lives during L. monocytogenes infection, but this increase did not occur in anti-IL-10 MAb-treated mice. Gamma interferon mRNA expression in the livers of the control MAb-treated mice was increased between 1 and 5 days after L. monocytogenes challenge and then decreased at 7 days after challenge. In contrast, gamma interferon mRNA expression in the livers of anti-IL-10 MAb-treated mice was not decreased until 7 days after challenge. These results indicate that endogenous IL-10 has both beneficial and detrimental effects on the host response to L. monocytogenes infection in mice.     

Roles for tumor necrosis factor and gamma interferon in resistance to enteric listeriosis

Listeria monocytogenes normally infects the host by translocating from the intestinal lumen. Experiments were carried out to determine if, when, and where tumor necrosis factor (TNF) and gamma interferon (IFN-gamma) function in antibacterial resistance during enteric listeriosis. Groups of normal mice and severe combined immunodeficient (SCID) mice were injected with neutralizing monoclonal antibodies (MAb) specific for each cytokine and then inoculated intragastrically with L. monocytogenes. The course of infection was monitored by enumerating listeriae in gut-associated lymphoid tissues, livers, and spleens. By the third day of infection, bacterial numbers in infected tissues and organs were greatly exacerbated in all mice treated with anti-TNF MAb, whereas bacterial numbers in the organs of mice treated with anti-IFN-gamma MAb did not differ from those present in the respective organs of control mice. However, by the fifth day of infection, bacterial numbers in the organs of anti-IFN-gamma MAb-treated normal mice and SCID mice were much greater than in the corresponding organs of control mice. Experiments with Listeria-immune mice revealed that TNF and IFN-gamma are involved in the expression of anti-Listeria memory immunity; however, it was also found that the anti-IFN-gamma MAb was relatively ineffective in inhibiting the expression of anti-Listeria immunity, whereas a polyclonal anti-IFN-gamma was quite effective.     

Normal macrophage functions, but impaired induction of gamma delta T cells, at the site of bacterial infection in CD45 exon 6-deficient mice

We investigated the protective functions of macrophages and gamma delta T cells in adult CD45 exon 6-deficient (CD45 -/-) mice against an intraperitoneal (i.p.) infection with Listeria monocytogenes. gamma delta T cells are preferentially localized in the spleen, liver, and intraperitoneal cavity of the adult CD45-/- mice. Increased numbers of gamma delta T cells were observed after i.p. infection with L. monocytogenes in the peritoneal cavity of C57BL/6 (CD45 +/+) mice but not in CD45 -/- mice. The gamma delta T cells showed predominant usage of V delta 5 and V delta 6 rearranged to J delta 1 in the infected CD45 -/- mice which are the same as those used by resident gamma delta T cells of noninfected CD45 +/+ and CD45 -/- mice. Furthermore, we analyzed the protective abilities of the CD45 -/-, CD45 +/+, and gamma delta T cell-depleted mice at the early stage of the listerial infection. The numbers of bacteria in the spleens and livers of the CD45 -/- mice 5 days after the listerial infection were almost ten times larger than those in the CD45 -/- and gamma delta T cell-depleted CD45 +/+ mice. Macrophages showed normal antigen presentation, nitric oxide production and bactericidal activity for L. monocytogenes despite their lacking CD45 surface expression, suggesting that CD45-negative macrophages have a minimal influence on the increased bacterial multiplication in the CD45-/- mice. These results suggest that the gamma delta T cells are induced by the bacterial infection in a CD45-dependent manner, and that unresponsiveness of the gamma delta T cells results in only weak protection against L. monocytogenes in CD45 -/- mice.     

Apolipoprotein E-deficient mice have impaired innate immune responses to Listeria monocytogenes in vivo

Apolipoprotein E (apoE) influences both innate and acquired immunity in cultured cells. To determine whether apoE affects the immune system in vivo, Listeria monocytogenes (LM) was administered intraperitoneally (10(4) c.f.u.) to congenic C57BL/6 apoE-/- and +/+ mice (n = 12 in each group). Survival was assessed daily for 5 days. Deficiency of apoE significantly increased death by day 5 (P = 0.03). The majority of deaths occurred at day 4. Extent of infection after LM administration was assessed at day 3 by determining colony counts in hepatic and splenic extracts. ApoE+/+ mice had very low colony counts in both spleen and liver [mean +/- SE: 2.0 +/- 0.5 and 0.7 +/- 0.2 (x 10(4)), respectively, n = 8 in each group]; while apoE-/- mice had significantly increased counts in both spleen and liver [64 +/- 51 and 98 +/- 93 (x 10(4)), P = 0.05 and 0.03]. Serum concentrations of TNF-alpha were significantly increased in apoE-/- mice at day 3 compared to apoE+/+ mice (127 +/- 43 pg/ml versus 20 +/- 17, P = 0.003). LM induced more hepatic damage in apoE-/- mice compared to apoE+/+ mice as judged by increased serum concentrations of alanine aminotransferase at day 1 (apoE-/- 301 +/- 45 U/ml, apoE+/+ 101 +/- 9 U/ml, P = 0.01). The increased proliferation and mortality from LM in apoE-/- mice occurred prior to the initiation of acquired immune responses. Therefore, apoE-deficient mice have an impaired innate response to infection by LM.     

Correlation between production of listeriolysin O by variants of Listeria monocytogenes and their virulence for rabbits

L. monocytogenes serovar 1/2a NCTC 7973 was passaged through rabbits and the severity of infection at each passage was determined by counting viable bacteria from infested organs and recording the time of death. A comparative evaluation of the levels of hemolysin produced in vitro by the original and six variant cultures (V1-V6) was done by determination of hemolytic units (CHU). While virulence of the cultures enhanced at each passage (2.2 x 10(9) CFU/g of the spleen for V6 as compared to 5.0 x 10(6) CFU/g spleen for the parent culture), the CHU decreased considerably, 3 CHU for the V6 as compared to 40 CHU for the parent strain. The results suggest that the level of in vitro production of listeriolysin may not parallel the pathogenicity of L. monocytogenes for rabbits.     

Organic acid dipping of catfish fillets: effect on color, microbial load, and Listeria monocytogenes

Microbiological and color changes of catfish fillets were determined following dip treatment in solutions at 4 degrees C of 2% acetic, citric, hydrochloric, lactic, malic, or tartaric acid. Fillets were inoculated with an eight-strain mixture of Listeria monocytogenes prior to dipping. L. monocytogenes, coliform, and aerobic plate counts and surface pH and Hunter color were measured at 0, 2, 5, and 8 days of storage at 4 degrees C. Acid dipping reduced surface pH and L. monocytogenes, coliform, and aerobic microbial loads. Little microbial proliferation was observed on acid-treated fillets, however, controls had a distinct foul odor and microbial loads in excess of 10(6) CFU/g by day 8. On untreated fillets, L. monocytogenes counts did not increase during storage, perhaps due to competitive inhibition by normal catfish microflora. Hunter color analysis revealed lighter and yellower acid-treated fillets than untreated controls, with malic acid producing the least bleaching. The shelf life of refrigerated fillets increased when fillets were acid dipped. It remains to be established if this enhanced microbial quality also parallels sensory acceptability.     

The role of polymorphonuclear leukocytes in the resistance to cutaneous Leishmaniasis

The massive infiltration by polymorphonuclear leukocytes (PMN) soon after skin infection with Leishmania major suggests that PMN could participate in reducing parasite load and controlling the spreading of leishmanial infection. Yet, direct evidence for the participation of PMN in host defense against L. major was lacking. We investigated L. major infection in susceptible and resistant mice treated with the monoclonal (mAb) antibody RB6-8C5 that depletes the population of mature neutrophils and eosinophils. Both BALB/c and C57BL/6 mice depleted of PMN show accelerated parasite spreading and more severe footpad swelling than similarly infected untreated mice. In addition, significant higher parasite numbers were found in the lesion draining lymph nodes from PMN-depleted C57BL/6 mice. Histopathological analysis of the paw confirmed neutrophils containing ingested parasites as the dominant cell type in the infiltrate of the first days after infection and the nearly absolute neutrophil depletion in mAb-treated mice. Our data show the importance of PMN in early control of parasite load and parasitism spreading in cutaneous leishmaniasis.     

Anti-idiotype monoclonal antibodies specific for the MOPC167 anti-phosphocholine transgene-encoded antibody

Four rat x mouse hybridomas secreting monoclonal anti-idiotypic (anti-Id) antibodies (MAb) specific for the transgene-encoded antibody of the 207-4 transgenic mouse line, which carries the VH1/V kappa 24 gene segments of the IgA, phosphocholine-(PC) specific MOPC167 myeloma, were developed from a fusion of Ag8-X63.653 mouse cells with spleen cells from a rat immunized with MOPC167 and HPCM27 anti-PC antibodies. The anti-Id MAb were shown by ELISA to be specific for PC-binding proteins of VH1/V kappa 24 H and L chains of various isotypes. They did not bind VH1/V kappa 22, VH1/V kappa 8, or VH1/V kappa 1 PC-binding proteins or other IgA or IgM myeloma proteins. Analysis by flow cytometry demonstrated that these MAb bind to the transgene-encoded membrane immunoglobulin (sIgM) as expressed on > 95% of the B220 positive 207-4 spleen cells. All four MAb were able to inhibit the binding of MOPC167 to PC conjugated to bovine serum albumin. Differences in fine specificity of binding were demonstrated by differential staining of spleen cells of the 216-7 mu kappa delta Mem MOPC167 transgenic mice. In these mice endogenous H chains associate with the transgene encoded L chain to form MOPC167 crossreactive idiotopes. Two of the MAb, 28-4-3 and 28-6-20, stained significant numbers of cells, while MAb 28-5-15 did not bind to 216-7 cells. Three of the MAb, 28-5-15, 28-6-20, and 28-4-3, when conjugated to Sepharose beads, were able to induce DNA synthesis in cultures of 207-4 transgenic spleen cells. None of the MAb were able to induce an antibody response in vivo. These MAb should prove useful in staining PC-transgenic B cells for flow cytometry studies and in defining early cellular events in the activation of idiotype positive B cells by anti-Id antibodies.     

Erythrocyte immunity and regulating factors in mice infected with Plasmodium berghei ANKA strain

After seventy-two ICR mice were inoculated with Plasmodium berghei ANKA strain, parasitaemia was revealed in all animals inoculated in two to seven days. During the course the number of malaria parasites increased rapidly from 2.3 +/- 1.3 x 10(3) on d2 to 93.7 +/- 1.8 x 10(3) on d7, the number of erythrocytes increased from 8.2 +/- 0.9 x 10(12)/L on d0 to 11.1 +/- 1.0 x 10(12)/L on d2 and then decreased gradually, reaching 1.9 +/- 0.4 x 10(12)/L on d7, and the number of white blood cells appeared to be fluctuated. Additionally, the rosette rate of erythrocyte=C3b receptor and the rosette rate of erythrocyte-immunocomplex increased on d2 and then decreased gradually to a very low level, suggesting that the erythrocyte immune function reduced in malaria. It is assumed that the reduction in erythrocyte immune function in malaria is attributed to the damage of the erythrocyte membrane in addition to the changes in the function of the erythrocyte immunoregulating factors.     

Exacerbation of toxoplasmosis in neutrophil-depleted mice

Studies were performed to determine whether resistance to Toxoplasma gondii infection in mice depends on a mechanism involving neutrophils. Immunocompetent C57BL/6 and C.B-17 mice infected with T. gondii by gavage had an increased percentage of neutrophils in their peripheral blood. C57BL/6 mice selectively depleted of neutrophils by injections of RB6-8C5 monoclonal antibody died during the acute phase of the disease. Depletion of neutrophils had no effect on interferon gamma production, but had a profound effect on the total numbers of peripheral blood CD4+ and CD8+ T cells. Neutrophil-depleted C.B-17 mice survived longer than neutrophil-depleted C57BL/6 mice when infected with T. gondii, however they became much sicker, and were less able to survive long-term than infected, control mAb-treated mice as indicated by severe sustained weight loss. This study shows that neutrophils play an important role in resistance to acute primary T. gondii infection and that depletion of neutrophils reduces the numbers of CD4+ and CD8+ lymphocytes recoverable from peripheral blood of infected but not uninfected mice. This effect on lymphocytes may contribute to the reduced long-term survival of neutrophil-depleted mice.     

Plasmid-mediated resistance to antimicrobial agents among listeriae

The resistance to 14 antiseptic-disinfectant and dye compounds of 208 strains of Listeria (132 L. monocytogenes, 63 L. innocua, 8 L. seeligeri, 1 L. ivanovii, 1 L. welshimeri, and 3 Listeria spp.) was tested by the agar-dilution procedure. The Listeria strains were isolated from different varieties of foods, environments of cheese dairies, humans, and wild birds. A total of 14 (6.7%) Listeria strains (12 L. monocytogenes and 2 L. innocua) were resistant to benzalkonium chloride, hexamidine diisethionate, and ethidium bromide. This multiple resistance was observed more frequently from strains of Listeria spp. detected on carcasses of poultry (47%) than strains isolated from human listeriosis cases or carriers (11.5%), red meats (10%), cheeses (5.4%), wild birds (0.9%), and environments of cheese dairies (0%). Among resistant strains, 10 groups of strains (71.5%) were differentiated by serogroup, phage typing, and sensitivity or resistance to cadmium. Extrachromosomal DNA was found in all resistant strains and was transferred at a high frequency among Listeria spp. (8.7 x 10(-6) to 1 x 10(-3) transconjugant CFUs per one donor CFU). These resistances were also transferable between L. monocytogenes and Staphylococcus aureus with similar transfer frequencies (7.8 x 10(-6) to 1 x 10(-4) and between strains of Staphylococcus aureus with similar transfer frequencies from 8 x 10(-7) to 3.3 x 10(-6). These results suggest that emergence of this multiple resistance in Listeria spp. could be due to acquisition of a replicon originating in staphylocci.     

The role of staphylococcal polysaccharide microcapsule expression in septicemia and septic arthritis

Staphylococcus aureus arthritis is a rapidly progressive and highly erosive disease of the joints in which both host and bacterial factors are of pathogenic importance. One potential bacterial virulence factor is the ability to express a polysaccharide capsule (CP). Among 11 reported capsular serotypes, CP type 5 (CP5) and CP8 comprise 80 to 85% of all clinical blood isolates. The aim of this study was to assess the role of CP5 as a virulence factor in staphylococcal septicemia and septic arthritis with a recently established murine model of hematogenously spread S. aureus arthritis. NMRI mice were inoculated intravenously with S. aureus strains isogenic for expression of CP5, and clinical, bacteriological, serological, and histopathological progression of disease was studied. Inoculation of 7 x 10(6) CFU of S. aureus per mouse induced 55% mortality in the group inoculated with the CP-expressing bacteria, compared to 18% in the group inoculated with CP- mutants. A lower dose of inoculum (3 x 10[6] per mouse) did not give rise to mortality in mice inoculated with CP mutant strains, whereas 18% of the mice inoculated with the CP5-expressing S. aureus died. Importantly, mice inoculated with S. aureus expressing CP5 had a significantly higher frequency of arthritis and a more severe form of the disease. In vitro assays suggested that macrophages were not able to phagocytize CP5+ staphylococci as efficiently as they were CP5- strains. In addition, once phagocytized, CP5+ bacteria were less efficiently killed than CP- mutants. In summary, CP5 leads to a higher frequency of arthritis and a more severe course of the disease. This seems to be related to the effects of the downregulatory properties of CP on the ingestion and intracellular killing capacity of phagocytes. Our results clearly indicate that the expression of CP5 is a determinant of the virulence of S. aureus in arthritis and septicemia.     

Mycobacterium avium complex infection in mice: lack of exacerbation after LP-BM5 murine leukemia virus infection

The murine leukemia virus LP-BM5 has been used to reproduce the model of murine AIDS in order to evaluate the course of infection with the MO-1 strain of Mycobacterium avium complex (MAC). LP-BM5 was inoculated in C57BL/6 mice by intravenous (i.v.) injection either 8 weeks before an i.v. challenge with 10(3) or 10(6) CFU of MAC (coinfection 1) or 10 days after an i.v. challenge with 10(3) CFU of MAC (coinfection 2). During coinfection 2 experiments, the phenotypic alterations in blood lymphocyte subsets were analyzed. During coinfection 1, LP-BM5 infection tended to decrease the mycobacterial growth, with the difference reaching statistical significance for the lower inoculum (10(3) CFU of MAC) (P<0.001). During coinfection 2, LP-BM5 did not exacerbate MAC infection except in the spleen, at day 90 after LP-BM5 challenge (P<0.001). LP-BM5 infection and the LP-BM5-MAC coinfection increased the numbers of activated CD4+ lymphocytes (CD4+ Ly6AE+) (P<0.001), activated CD8+ lymphocytes (CD8+ Ly6AE+) (P<0.001), and activated B lymphocytes (Ly5+ Ly6AE+) (P<0.001). This activation of T lymphocytes could explain the lack of exacerbation of MAC infection and even the trend to a lower level of MAC infection. Thus, this model of retroviral infection of mice does not seem to be a reliable model of immunodepression for the study of MAC infection and its treatments.     

Comparative incidence of the rearrangements of TEL/AML1 and ALL1 genes in pediatric precursor B acute lymphoblastic leukemias in India

We conducted an in vivo study with the mouse model of Vibrio vulnificus infection to evaluate the efficacies of therapy with minocycline or cefotaxime alone and in combination. V. vulnificus was introduced subcutaneously into the area over the right thigh. The inoculum size ranged from 1.0 x 10(3) to 1.2 x 10(8) CFU from experiment to experiment but was constant for all animals in the same experiment. Antibiotics were given intraperitoneally 2 h after the bacteria were inoculated. In experiments 1 to 4, the standard dose for humans was used to treat the infection, while in experiment 5, five times the standard dose for humans was used to treat the infection. In experiment 1, with a small inoculum of 5 x 10(3) CFU, all mice in the saline-treated control group and the cefotaxime-, minocycline-, and combined antibiotic-treated groups survived. In experiment 2, with a moderate inoculum of 1.2 x 10(5) CFU, all the mice in the three antibiotic-treated groups survived, while only two of nine mice in the control group survived. In experiment 3, with a large inoculum of 8.0 x 10(7) CFU, six of nine mice in the combined antibiotic-treated group survived, while only one of nine mice in the cefotaxime-treated group and none of the mice in the control and minocycline-treated groups survived. In experiment 4, with a large inoculum of 1.2 x 10(8) CFU, 8 of 20 mice in the combined antibiotic-treated group survived, while none of the 20 mice in the control group, the group treated with cefotaxime alone, and the group treated with minocycline alone survived. In experiment 5, in which mice were infected with a large inoculum of 6.6 x 10(7) CFU and treated with five times the standard human dose of antibiotics, 10 of 12 mice in the combined antibiotic-treated group survived, while only 4 of 12 mice in the minocycline-treated group, 1 of 12 mice in the cefotaxime-treated group, and none of the mice in the control group survived. In experiments 3 to 5, the difference in the survival rates between the combined antibiotic-treated and minocycline-treated groups was statistically significant (P < 0.05). These results indicate that combination therapy with cefotaxime and minocycline is distinctly more advantageous than therapy with the single antibiotic regimen for the treatment of severe experimental V. vulnificus infections.     

Unstable expression and thermal instability of a species-specific cell surface epitope associated with a 66-kilodalton antigen recognized by monoclonal antibody EM-7G1 within serotypes of Listeria monocytogenes grown in nonselective and selective broths

Conditions that resulted in unstable expression and heat instability of a cell surface epitope associated with a 66-kDa antigen in Listeria monocytogenes serotypes were identified with the probe monoclonal antibody (MAb) EM-7G1 in an enzyme-linked immunosorbent assay. This epitope appeared to be absent in three serotypes (serotypes 3b, 4a, and 4c), which did not react with MAb EM-7G1 irrespective of the enrichment broth tested. The remaining 10 serotypes were detected by MAb EM-7G1 only when cells were grown in nonselective brain heart infusion broth (BHI) or selective Listeria enrichment broth (LEB). When cells were grown in Listeria repair broth (LRB), only 6 of the 13 serotypes were detected by MAb EM-7G1, and recognition of serogroup 4 was completely lost. None of the 13 serotypes was detected by MAb EM-7G1 when cells were grown in two other commonly used Listeria-selective media, UVM1 broth and Fraser broth (FRB), indicating that possible loss of epitope expression occurred under these conditions. MAb EM-7G1 maintained species specificity without cross-reacting with live or heat-killed cells of six other Listeria spp. (Listeria ivanovii, Listeria innocua, Listeria seeligeri, Listeria welshimeri, Listeria grayi, and Listeria murrayi) irrespective of the enrichment conditions tested. Due to heat instability of the cell surface epitope when it was exposed to 80 or 100 degrees C for 20 min, MAb EM-7G1 is suitable for detection of live cells of L. monocytogenes in BHI or LEB but not in LRB, UVM1, or FRB enrichment medium.     

Cultured human ankle and knee cartilage differ in susceptibility to damage mediated by fibronectin fragments

A culture of the psychotrophic strain FloraCarn L-2 of Lactobacillus alimentarius was added to ground beef (pH 5.4) inoculated with two isolates of Listeria monocytogenes able to grow in refrigerated ground beef. The ground beef was vacuum-packaged and stored for 9 weeks at 4 degrees C. Populations of inoculated L. monocytogenes initially were 6.3 to 6.4 log10 CFU/g and increased to 7.4 log10 CFU/g in ground beef with no added lactobacilli. Addition of L. alimentarius L-2 or its antibiotic-resistant mutant SRL-2 reduced the final populations of L. monocytogenes to 4.3 or 4.1 log10 CFU/g, respectively. L. alimentarius L-2 did not produce bacteriocins or hydrogen peroxide in vitro. The antilisterial effect of L. alimentarius observed in laboratory media and ground beef is attributed to lactic acid (ca. 50 mM) produced by growing cultures.     

Reduced nociceptive behavior in islet amyloid polypeptide (amylin) knockout mice

Macrolide resistance is an emerging problem in AIDS patients who receive these agents for treatment or prophylaxis against Mycobacterium avium (MAC) infection. We compared the emergence of resistant MAC strains during therapy with clarithromycin (clarithromycin resistance was defined as MIC > or = 32 microg/ml) and azithromycin (azithromycin resistance was defined as MIC > or = 128 microg/ml) in C57BL/6 beige mice. Treatment with clarithromycin and azithromycin resulted in a decrease of 98.5% in the number of viable bacteria in spleens at week 8 and 99% at week 12 compared with the number of bacteria present in spleen before the initiation of therapy (P < 0.001). Splenic homogenates were also plated onto 7H11 agar plus clarithromycin at 32 microg/ml or azithromycin at 128 microg/ml. Resistance emerged significantly more often in mice treated with clarithromycin (100% of treated mice at both 8 and 12 weeks) than in those receiving azithromycin (0% at week 8 and 14% at week 12). The frequencies of resistance of the MAC population in the spleen to clarithromycin were 2.1 x 10(-3) at week 8 and 1.1 x 10(-2) at week 12, whereas resistance to azithromycin was absent at week 8 (all mice) and was approximately 3.5 x 10(-5) (mean for the three positive animals) at week 12. Clarithromycin was more effective in initial reduction of MAC burden in tissue after 8 and 12 weeks of treatment, but resistant strains emerged significantly more frequently after treatment with clarithromycin than after treatment with azithromycin.     

Immunological responses critical to the therapeutic effects of adriamycin plus interleukin 2 in C57BL/6 mice bearing syngeneic EL4 lymphoma

A safe and effective therapeutic combination of moderate doses of Adriamycin (doxorubicin, 4 mg/kg, IV, Days 1 and 8 or only Day 8) plus prolonged administration of moderate doses of interleukin 2 (2 micrograms, b.i.d., Days 9-40) was developed in the syngeneic EL4 (5 x 10(4) cells, IP, Day 0) lymphoma--C57B1/6 mouse model and has been reported in the companion paper. The studies described herein demonstrate that the effectiveness of this combination treatment against EL4 lymphoma growing intraperitoneally in C57B1/6 mice was dependent upon the presence of CD8+ cells. Thus, the induction of long-term survivors (60-80%) by Adriamycin plus interleukin 2 was completely ablated by pretreatment of mice with anti-CD8 monoclonal antibody (MAb), whereas pretreatment with anti-CD4 MAb only partially inhibited the therapeutic effects and anti-NK1.1 MAb had no effect. A close association between survival, an increase in phenotypically identified CD8+ cells, and an increase in specific anti-EL4 cytolytic activity was demonstrated with cells from the tumor site (peritoneum) but not consistently with cells from the spleen. No association was observed between survival and modulations in natural killer (NK), lymphokine-activated killer (LAK), or tumoricidal macrophage activity of spleen or peritoneal cells. Taken together the results indicate that, in this model, the most relevant correlate of a therapeutically effective host antitumor response is the level of specific EL4 tumor killing by cells present at the tumor site. Based on the findings reported herein, it can be predicted that weakly immunogenic tumors may be eradicated by immunologic mechanisms elicited in conjunction with properly designed therapeutic regimens.     

Systemic cytokine immunotherapy for experimental cytomegalovirus retinitis in mice with retrovirus-induced immunodeficiency

PURPOSE: To evaluate and compare the in vivo administration of interleukin-2 (IL-2) or interleukin-12 (IL-12) in the immunotherapy of necrotizing retinitis caused by murine cytomegalovirus (MCMV) in mice with a retrovirus-induced immunodeficiency syndrome (MAIDS). METHODS: Adult C57BL/6 mice with MAIDS of 8 weeks' duration were treated with either a single intramuscular injection of polyethylene glycol-modified human recombinant IL-2 (PEG-IL-2) or multiple intramuscular injections of murine recombinant IL-12; untreated mice with MAIDS received phosphate-buffered saline. Two days later, the left eyes of all mice were inoculated with MCMV by subretinal injection and evaluated at day 6 for intraocular MCMV titers or at day 10 for frequency of necrotizing MCMV retinitis. RESULTS: Infectious MCMV was significantly reduced in whole eyes of PEG-IL-2-treated mice with MAIDS (2.8 log10), but not in whole eyes of IL-12-treated animals (4.4 log10) when compared with whole eyes of untreated animals with MAIDS (4.5 log10). Similarly, whereas eyes from approximately 80% of IL-12-treated and untreated mice with MAIDS showed histopathologic features consistent with classic necrotizing MCMV retinitis (full-thickness retinal necrosis associated with virus inclusions and cytomegalocytes), none (0%) of PEG-IL-2-treated animals with MAIDS showed classic MCMV retinitis. Instead, eyes from these animals showed either retinal folding or outer retinal atrophy, a pattern of histopathology similar to that observed in eyes from immunologically normal C57BL/6 mice inoculated subretinally with MCMV. CONCLUSIONS: These results provide proof-of-principle for the hypothesis that systemic cytokine immunotherapy will reduce the frequency of CMV retinitis in a setting of retrovirus-induced immunosuppression. Because of the striking differential effects of IL-2 and IL-12 on MCMV-retinitis in mice with MAIDS, the authors conclude that cytokine immunotherapy for cytomegalovirus-induced retinitis is cytokine-specific, even for such cytokines as IL-2 and IL-12 that have T cell regulation in common.     

Experimental mixed infection with Yersinia enterocolitica and Listeria monocytogenes in guinea pigs

The pathogenesis and the cell immune response (CIR) of guinea pigs after mixed infection with Y. enterocolitica and L. monocytogenes was investigated. The guinea pigs were infected per os with 1.1 x 10(9) CFU Y. enterocolitica 0:3, (pYV+) and four days later with 1.1 x 10(9) CFU L. monocytogenes 4B. Clinical, paraclinical and morphological findings attending the infectious process were followed in dynamics up to the 28th day post infection (p.i.) with L. monocytogenes. The phagocyting activity of alveolar macrophages (aMa) was suppressed against Y. enterocolitica, in contrast to peritoneal macrophages (pMa) engulfing yersiniae more actively at the end of the study. Moreover, the tendency of augmented entering in both phagocytes of L. monocytogenes cells was well demonstrated, starting at the earlier intervals of examination. Histopathological studies showed a purulent meningoencephalitis and a catarrhal pneumonie, non-reactive micronecroses in the spleen and lymphadenitis catarrhalis in the mesenteric lymph nodes. Analysis of the T-cell immune response (T-CIR) showed maximal values in the spleen lymphocytes after Y. enterocolitica and L. monocytogenes mixed infection. The B-CIR occurred early (at the 7th day p.i.) and was maximal at the 28th day p.i. in blood lymphocytes. The results obtained demonstrated that the mixed infection of guinea pigs with Y. enterocolitica and L. monocytogenes runs has a non lethal, generalized illness with a dominant role of L. monocytogenes cells.