Outer membrane protein-specific monoclonal antibodies protect SCID mice from fatal infection by the obligate intracellular bacterial pathogen Ehrlichia chaffeensis

Previous studies of Ehrlichia chaffeensis infection in the mouse have demonstrated that passive transfer of polyclonal Abs from resistant immunocompetent mice to susceptible SCID mice ameliorated infection and disease, even when Abs were administered during established infection. To identify particular Abs that could mediate bacterial clearance in vivo, E. chaffeensis-specific mAbs were generated and administered to infected SCID mice. Bacterial infection in the livers was significantly lowered after administration of either of two Abs of different isotypes (IgG2a and IgG3). Moreover, repeated administration of one Ab (Ec56.5; IgG2a) rescued mice from an otherwise lethal infection for at least 5 wk. Both protective Abs recognized the E. chaffeensis major outer membrane protein (OMP)-1g. Further studies revealed that both Abs recognized closely related epitopes within the amino terminus of the first hypervariable region of OMP-1g. Analyses of human sera showed that E. chaffeensis-infected patients also generated serological responses to OMP-1g hypervariable region 1, indicating that humans and mice recognize identical or closely related epitopes. These studies demonstrate that OMP-specific mAbs can mediate bacterial elimination in SCID mice, and indicate that Abs, in the absence of cell-mediated immunity, can play a significant role in host defense during infection by this obligate intracellular bacterium.     

Suppression of murine lupus nephritis by administration of an anti-idiotypic antibody to anti-DNA

The suppression of pathogenic antibodies to DNA in NZB/NZW f1 female mice was achieved by repeated inoculation of the mice with a monoclonal anti-idiotypic antibody (anti-Id). The anti-Id, an IgG1, kappa, was directed against a major cross-reactive idiotype (Id) on NZB/NZW IgG antibodies to DNA. One hundred micrograms of the anti-Id were inoculated i.p. every 2 wk, beginning at 6 wk of age (nondiseased mice--no circulating anti-DNA or proteinuria) or 20 wk of age (diseased mice--all with circulating anti-DNA, one-third with proteinuria). As controls, littermates received an IgG, kappa non-DNA-binding myeloma or no treatment. In the young mice, nephritis and anti-DNA antibodies appeared at the same time in all groups, and their circulating antibodies to DNA did not bear the target Id. In the older (20-wk-old) mice, survival was significantly prolonged because of delay in the onset of nephritis; the total quantities of antibodies to DNA were diminished, and the target Id, initially present on circulating IgG, was deleted. These benefits were transient; the suppression of antibodies was followed by the appearance of large quantities of anti-DNA that did not bear the major Id. Therefore, although administration of anti-Id was effective in reducing an undesirable antibody response after the target Id was present on circulating antibodies, the benefits were limited, probably by Id "switch" or by increased synthesis of pathogenic antibodies bearing a minor Id.     

Neonatal injection of CD3 antibody into nonobese diabetic mice reduces the incidence of insulitis and diabetes

Over 80% of nonobese diabetic (NOD) mice develop lymphocytic infiltrates of their pancreatic islets (insulitis) by 6 wk of age and 50% of the females are diabetic by 6 mo of age. The incidence of insulitis in NOD mice injected once as neonates with 250 micrograms of the CD3 antibody, 145.2C11, was 8% at 10 wk of age, increasing to 25% at 32 wk of age. Fewer than 10% of these animals developed diabetes by 8 mo of age. Neonatal administration of 145.2C11 reduced the proliferative responses of spleen cells to mitogen stimulation 2 and 4 wk postinjection and expression of TCR was reduced 1 to 5 wk postinjection. The percentage of CD4 and CD8 cells in the spleen was transiently reduced after injection and the frequency of Pgp-1+-high cells (putative memory cells) was increased 2 to 4 wk postinjection, suggesting that in vivo administration of the antibody caused some T cells to divide as well as transiently reducing T cell numbers. IL-2R expression was not detected on spleen cells in the 4 wk after antibody injection. The phenotypic and functional changes after neonatal CD3 antibody injection resolved by 8 wk of age. The control and injected mice grew normally and made equivalent IgG antibody responses to injected human IgG. Neonatally injected 145.2C11 antibody was cleared from the circulation with a terminal half-life approximating to 21 days but greater than 90% of antigen binding activity was lost 6 days after injection. Protection from diabetes did not follow neonatal elimination of T cells with CD4 and CD8 antibodies, nor the injection of a TCR subset antibody, F23.1. Our data suggest that the neonatal T cell repertoire is open to modulation by a single injection of a CD3 antibody and they offer a new experimental approach to immunotherapy in an animal model of type 1 diabetes.     

Mechanism of antibody-mediated protection against herpes simplex virus infection in athymic nude mice: requirement of Fc portion of antibody

Experiments were performed to investigate the resistance of the host due to antibody-mediated mechanisms to herpes simplex virus (HSV) infection. Transfer of hyperimmune anti-HSV mouse serum inhibited the development of skin lesions and prolonged the survival of lethally HSV-infected nude mice. Relatively high concentrations of antibody were required to achieve this protection. Antisera prepared in heterologous animals were also effective, while administration of anti-cowpox virus serum or interferon provided no protection. This type of protection is therefore due to specific antibody and cannot be attributed to interferon. In order to delineate the requirement for antibody in antibody-mediated protection, human gamma globulin preparations were transferred to lethally HSV-infected nude mice. Transfer of intact human gamma globulin (GG) was effective in controlling infection. S-sulfonation of GG did not diminish the protective ability. However, purified F(ab')2 did not have any protective action even when it was administered frequently to maintain serum neutralizing antibody titer. GG was effective in C5-deficient mice lethally infected with HSV. These results indicate that in vivo antibody-mediated protection to HSV infection requires the Fc region of the intact IgG molecule and suggest that antibody-dependent cell-mediated cytotoxicity may be operative in vivo.     

Selective improvement of thymus and some T cell dysfunctions in NZB mice by in utero thymulin treatment

NZB mice were treated during gestation with thymulin, a thymus-secreted, zinc-associated nonapeptide. Control pregnant NZB mice received either zinc alone or saline alone. Offspring from all three groups of NZB mothers, and age-matched DBA/2 mice, were tested for the following immunologic parameters: thymulin serum levels at 2 and 5 wk of age; splenic anti-sheep red blood cell (anti-SRBC) plaque-forming cell (PFC) numbers after immunization at birth or at 2 wk of age; anti-human gamma-globulin (anti-HGG) antibody titers after immunization at 2 wk of age, with or without prior tolerance induction at birth with deaggregated HGG; spontaneous IgM serum levels at 2 and 5 wk of age; spontaneous splenic anti-trinitrophenyl (anti-TNP) PFC numbers at 2 wk of age. As compared with DBA/2 mice, young NZB mice exhibited low circulating thymulin titers, high antibody responses to SRBC and to HGG, resistance to tolerance induction by deaggregated HGG, increased spontaneous IgM serum levels, and increased spontaneous anti-TNP PFC numbers. However, marked reductions in anti-SRBC and anti-HGG antibody production, both thymus-dependent responses, were observed in the young NZB offspring of thymulin-treated mothers as compared with NZB controls born from zinc- or saline-treated mothers. A delay in the postnatal decrease of serum thymulin levels was also noted in the offspring of thymulin-treated mothers. Interestingly, these effects of in utero thymulin treatment tended to become more pronounced with advancing age during the postnatal period. Conversely, IgM serum levels, spontaneous anti-TNP PFC and sensitivity to tolerance induction were not affected by thymulin treatment during fetal life. Taken together, the data suggest that in utero exposure to pharmacologic concentrations of thymulin induces a persistent and selective improvement of some thymus and T cell dysfunctions but has no effect on intrinsic B cell abnormalities of NZB mice.     

Enhanced response to enzyme replacement therapy in Pompe disease after the induction of immune tolerance

Pompe disease, which results from mutations in the gene encoding the glycogen-degrading lysosomal enzyme acid alpha -glucosidase (GAA) (also called "acid maltase"), causes death in early childhood related to glycogen accumulation in striated muscle and an accompanying infantile-onset cardiomyopathy. The efficacy of enzyme replacement therapy (ERT) with recombinant human GAA was demonstrated during clinical trials that prolonged subjects' overall survival, prolonged ventilator-free survival, and also improved cardiomyopathy, which led to broad-label approval by the U.S. Food and Drug Administration. Patients who lack any residual GAA expression and are deemed negative for cross-reacting immunologic material (CRIM) have a poor response to ERT. We previously showed that gene therapy with an adeno-associated virus (AAV) vector containing a liver-specific promoter elevated the GAA activity in plasma and prevented anti-GAA antibody formation in immunocompetent GAA-knockout mice for 18 wk, predicting that liver-specific expression of human GAA with the AAV vector would induce immune tolerance and enhance the efficacy of ERT. In this study, a very low number of AAV vector particles was administered before initiation of ERT, to prevent the antibody response in GAA-knockout mice. A robust antibody response was provoked in naive GAA-knockout mice by 6 wk after a challenge with human GAA and Freund's adjuvant; in contrast, administration of the AAV vector before the GAA challenge prevented the antibody response. Most compellingly, the antibody response was prevented by AAV vector administration during the 12 wk of ERT, and the efficacy of ERT was thereby enhanced. Thus, AAV vector-mediated gene therapy induced a tolerance to introduced GAA, and this strategy could enhance the efficacy of ERT in CRIM-negative patients with Pompe disease and in patients with other lysosomal storage diseases.     

Cholera toxin modulates the systemic immune responses against Vibrio cholerae surface antigens after repeated inoculations

The immunomodulating properties of a low cholera toxin (CT) dose over the systemic antibody response against Vibrio cholerae antigens after a comparatively extensive period of time were evaluated. Groups of 10 mice were injected intraperitoneally three times at 0, 30 and 86 days with 500 microl of buffer or 10(8) viable recombinant V. cholerae bacteria (lacking cholera toxin A subunit) with or without 100 ng of CT. Sera were obtained from inoculated mice at 0, 14, 28, 37, 58, 80, 93, 114, 236 and 356 days after the first injection. Vibriocidal activity and IgM and IgG anti-lipopolysaccharide (LPS) or outer membrane protein (OMP) antibodies levels were estimated by ELISA in sera of inoculated mice. Anti-LPS IgG subclasses were measured 2 weeks after each immunization by ELISA. Treatment of mice with CT markedly influenced the immune response to LPS but not against OMP of V. cholerae. Simultaneous intraperitoneal administration of CT with V. cholerae resulted in marked enhancement of both IgM anti-LPS and vibriocidal titers which subsisted for a relatively extensive period of time after repeated antigen administration. No differences were observed in IgM and IgG anti-OMP titers after extended periods of time between CT and control treatments. A similar pattern of IgG anti-LPS subclasses was observed in the serum samples analyzed. These results suggest that long term CT administration modulates the IgM anti-V. cholerae LPS response and the serum vibriocidal activity.     

Suppression of growth of a mouse plasmacytoma by the IgG2 fraction of syngeneic antitumor globulin

Summary The effects of syngeneic antitumor antibody on transplanted plasmacytoma cells have been examined. Globulin was prepared from ascites fluids produced in Balb/c mice injected with MOPC 315 tumor cells and bearing the solid tumor. Normal Balb/c mice were given inoculations of tumor cells that had been incubated with the antitumor globulin obtained at various intervals after immunization, or with portions of such globulins. These materials were prepared to express the IgG2 class antibody by three procedures: precipitation with heterologous anti-mouse IgG1, passage through columns of Sepharose anti-IgG1, or adsorption to and elution from heat- and formalin-killed protein A-bearing staphylococci. The original antitumor globulins showed differences with time relative to the second injection of the immunizing tumor, in that a number of the earlier pools led to some suppression of tumor growth, and a number of the later pools led to some enhancement. Of the globulins obtained later, preparations expressing the IgG2 class of antibody by precipitation with anti-IgG1 serum caused some suppression of tumor growth. Pronounced suppression of growth was consistently obtained with anti-MOPC 315 globulin freed of IgG1 by passing it through an anti-IgG1 immunoadsorbent, and with IgG2a preparations obtained by elution from the protein A-bearing staphylococci. Of the anti-IgG1 column-treated preparations, the suppressive effect was maximal in globulin obtained 15–26 days after the second immunization. The suppressive effect of these preparations could be removed by absorption with MOPC 315 cells, but not by cells of another Balb/c tumor nor by two other plasmacytomas.     

Chronic Giardia muris infection in anti-IgM-treated mice. I. Analysis of immunoglobulin and parasite-specific antibody in normal and immunoglobulin-deficient animals

To investigate the role of B cells and antibody in the immune response of mice to the murine intestinal parasite Giardia muris, we used mice treated from birth with rabbit anti-IgM antisera (aIgM). Such mice developed in serum and in gut secretions extreme Ig deficiency (IgM, IgA, and IgG) relative to control animals. The aIgM-treated mice showed no anti-G. muris antibody in serum or in gut wash material. Infections of G. muris in these mice were chronic, with a high load of parasite present in the small bowel, as reflected by prolonged cyst excretion (greater than 11 wk) and high trophozoite counts. In contrast, normal, untreated mice or NRS-treated animals developed anti-parasite IgA and IgG antibody in serum, demonstrated IgA antibody against the parasite in gut washings, and expelled the parasite within 9 wk. These effects of aIgM treatment on the murine response to primary infection with G. muris were demonstrated in two strains of mice: BALB/c and (C57BL/6 X C3H/He) F1. It was also observed that the response to G. muris infection in untreated animals was characterized by higher than normal total secretion of IgA into the gut and a concomitant increase in the serum polymeric IgA level. Mice treated with aIgM had a marked decrease of both monomeric and polymeric IgA in serum, and little detectable IgA in the intestinal lumen. These experiments provide the first demonstration that anti-IgM treatment suppresses a specific intestinal antibody response to antigen, and provide evidence that B cells and antibody play a role in the development of an effective response to a primary infection with G. muris in mice.     

Anti-interleukin 6 (IL-6) receptor antibody suppresses Castleman's disease like symptoms emerged in IL-6 transgenic mice

Transgenic mice carrying human IL-6 cDNA fused with a murine major histocompatibility class-I promoter (H-2L(d)) were serially administered with anti-interleukin-6 receptor (IL-6R) monoclonal antibody (mAb), MR16-1, from the age of 4 weeks to estimate its efficacy on a variety of disorders developed in these mice, most of which are similar to the disorders associated with Castleman's disease. In the control mice treated with isotype-matched mAb, a massive and multiple IgG1 plasmacytosis, mesangial proliferative glomerulonephritis, leukocytosis, thrombocytosis, anemia and abnormalities of blood chemical parameters have developed in accordance with the elevation of serum IL-6, and 50% of mice have died of renal failure by 18 weeks of age. In contrast, the treatment with MR16-1 prevented all these symptoms and prolonged the lifetime of the majority of the mice. Thus, the constitutive overexpression of IL-6 caused various disorders, and the treatment with anti-IL-6R mAb completely prevented from these symptoms. These results clearly confirm that IL-6 indeed plays an essential role in the pathogenesis of a variety of disorders. Furthermore, anti-IL-6R mAb could provide novel therapy for Castleman's disease and MR16-1 should be a useful tool to estimate therapeutic potential of IL-6 antagonists in a variety of murine models for human disease.     

The Effects of Interleukin‐6 Signal Blockade on Immune System,Reproductive and Skeletal Development in Juvenile Mice

Interleukin‐6 (IL‐6) is involved in the pathogenesis of multiple disorders, including juvenile autoimmune diseases. IL‐6 participates in a broad spectrum of physiological events, and the IL‐6 receptor (IL‐6R) is widely distributed across multiple organs. The interrelationship of development phases in juveniles together with organs involved in IL‐6 signaling called for evaluations of anti–IL‐6R antibody induced effects in a juvenile mouse model to assess the safety of such an approach in human juvenile arthritis. Here we show that naive mice in which IL‐6 signals have been transiently blocked during the juvenile period develop normally. The fatal immunogenic reactions recorded earlier by repeated administration of the chosen rat anti‐mouse IL‐6R antibody, MR16‐1, to mice were avoided successfully by application of a high loading dose followed by lower maintenance doses, with the support of modeling data. The high loading‐dose regimen enabled us to conduct assessments without any major interference due to immunogenicity. Transient and complete inhibition of IL‐6 signals from postnatal days 22 to 79 in mice exhibited no biologically important changes in sexual maturation or development of immune and skeletal systems. Although tendencies toward reductions of peripheral blood T‐cell counts were observed, normal levels of antigen‐specific IgG/IgM antibody productions indicating sufficient immunological functions were confirmed. Our results demonstrate that blockage of IL‐6R by the neutralizing antibody does not affect juvenile development. This may be in part due to the generation or existence of compensatory pathways in the whole body system.     

Defective vaccine-induced immunity to Schistosoma mansoni in P strain mice. I. Analysis of antibody responses

Inbred P4 strain mice have previously been shown to be uniquely defective in their resistance to challenge infection induced by irradiated cercariae of Schistosoma mansoni. To assess whether the low levels of resistance developed by vaccinated P mice could be due to a defective antibody response, we compared the anti-schistosomulum antibody responses in vaccinated P animals with those occurring in vaccinated C57BL/6J (B6) mice, a strain that consistently develops high levels of resistance to challenge infection. Our results indicate that vaccinated P mice develop levels of total anti-schistosomulum antibodies that are significantly lower than those occurring in B6 mice for at least 15 wk after immunization, with the exception of the fifth week, at which time the responses are indistinguishable. Further analysis revealed that the defect in P strain antibody response occurs specifically in the IgM isotype and that specific IgM levels in P mice are less than one-half the levels in B6 mice at every time point examined. In contrast, no differences in total IgM immunoglobulins were evident when sera from normal (nonvaccinated) P and B6 mice were compared. P mouse anti-schistosomulum IgG antibody responses reached the same levels as those observed in B6 mice by 5 wk after vaccination. However, a much faster decay in IgG antibody levels occurred after this time point in P animals. No differences were observed when the levels of anti-schistosomulum antibodies occurring in each of the major IgG isotypes (IgG1, IgG2a, IgG2b, IgG3) were compared in sera from P and B6 mice vaccinated 4 wk previously. Similarly, vaccinated P and B6 mice were found to mount indistinguishable IgG anamnestic responses after challenge infection. Finally, no differences between vaccinated P and B6 mice were observed when immediate (30 min) skin test and mast cell degranulation responses to a soluble schistosome antigenic preparation were compared. The above findings suggest that P strain mice have a specific defect in their ability to mount IgM antibody responses after immunization with irradiated cercariae. The possible contribution of this defect in IgM response to the decreased resistance of vaccinated P mice to challenge infection is discussed.     

Effect of breast feeding on the development of anti-idiotype antibody response to F glycoprotein of respiratory syncytial virus in infant mice after post-partum maternal immunization

Groups of lactating BALB/c mice were immunized in the immediate postpartum period with high doses of mAb (Ab-1) to the F-glycoprotein (F-gp) of respiratory syncytial virus (RSV). This antibody possessed neutralizing activity against the whole virus. The immune response to F-gp was studied in the breast feeding infant mice of such mothers at regular intervals before and after weaning. All infant mice exhibited anti-F-gp activity in serum, which was detected until 6 wk of age. Splenic cells of such breast feeding infant mice collected after weaning exhibited in vitro synthesis of antibody against Ab-1, the antibody previously used for maternal immunization. Subsequent immunization with homologous purified RSV F-gp resulted in a booster response for IgG, IgM, and plaque-neutralizing antibody to the immunizing RSV protein and to the whole virus in the infants primed via breast feeding. The enhanced antibody response was specific for the antigenic epitopes of the virus protein recognized by the monoclonal antibody used for maternal immunization. Similar booster effect was seen in control infants of nonimmunized mothers who were immunized with a polyclonal Ab-2 prepared by repeated immunization with Ab-1 in DBA/2 mice. These data demonstrate induction of RSV-specific anti-idiotype antibody in the neonates via the process of breast feeding, secondary to maternal immunization after the delivery of the neonate. Use of idiotypic vaccines in the mother and the transfer of RSV-specific idiotypes may offer an alternate approach to the development of effective immunoprophylaxis for RSV infection in early infancy.     

Serologic response of the opossum Didelphis virginiana to a temperature-sensitive mutant (ts-4) of Toxoplasma gondii.

A study was designed to measure the Toxoplasma gondii-specific IgM and IgG antibody responses of opossums inoculated with tachyzoites of the temperature-sensitive mutant of T. gondii, ts-4, and to examine its persistence in the tissues. Four young opossums seronegative for anti-Toxoplasma gondii IgM and IgG antibodies immediately after capture and 4 wk later were injected subcutaneously with 1.8 x 10(6) ts-4 tachyzoites; a fifth opossum (also seronegative) received an injection of saline only. Serum was collected weekly and titered by modified direct agglutination for anti-Toxoplasma gondii IgM and IgG. IgM titers were detectable from week 1 to week 6 postinoculation (PI). IgG was measurable by week 3 and remained high for 30 wk PI when the opossums were killed and examined. The control opossum did not develop a specific antibody response. At necropsy major lesions were not found. No anti-Toxoplasma gondii IgG was detected in serum collected from mice injected with tissues prepared from the opossums at necropsy, and no T. gondii was found on impression smears made at necropsy from these mice. Modified direct agglutination performed with or without 0.2 M 2-mercaptoethanol worked well for measuring specific IgM and IgG antibodies in experimentally infected opossums.     

Evaluation of immunobiological activity of Francisella tularensis C-complex preparations as promising component of subunit vaccines

Data on influence of Francisella tularensis C-complex preparations on formation of immunity against tularemia are presented. Study of cellular immunity characteristics as well as dynamics of antibody response was carried out on white mice and guinea pigs models. Absence of toxicity, pyrogenicity, and negative effects on immunocompetent cells in combination with protective activity points to possibility of use the C-complex as a component of a subunit vaccine.     

Antibody mediated suppression of secondary IgM response in nude mice against vesicular stomatitis virus

Nude mice immunized with either of the two serotypes of vesicular stomatitis virus (VSV), VSV Indiana (VSV-Ind) or VSV-New Jersey (VSV-NJ), showed an early T cell independent immunoglobulin (Ig) M antibody response comparable with normal euthymic mice. Unlike euthymic mice, however, nude mice reinjected with the homologous serotype were unable to mount a second measurable serum neutralizing (SN) antibody response; a second injection with the heterologous serotype induced a normal primary type of SN antibody response. The serotype-specific refractoriness to a second challenge recovered at about 10 wk after primary infection. When antibody responses were assayed by enzyme-linked immunoabsorbent assay (ELISA), suppressive effects by previous immunization could be observed even after challenge with the heterologous serotypes; this finding probably reflects the known existence of common nonneutralizing determinants shared between the two serotypes. A weak 2-mercaptoethanol (2-ME)-resistant anti-VSV IgG SN antibody response was noticed during the primary response in nude mice and was also found in ELISA; after second infections, this 2-ME-resistant response did not develop. Serum transfer studies in nude and +/+ mice confirmed that the serotype-specific transitory refractoriness of a second response in nude mice was mediated through the anti-VSV-specific IgM antibodies.     

Long-term vaginal antibody delivery: delivery systems and biodistribution

Topical delivery systems can provide prolonged delivery of antibodies to the vaginal mucosal surface for long-term protection against infectious diseases. We examined the biodistribution of antibodies during 30 days of vaginal antibody delivery in mice. Different antibody preparations (including monoclonal IgG and IgM, as well as several different (125)I-labeled IgGs) were administered by polymer vaginal rings, which were designed to provide continuous antibody delivery. Antibody concentrations remained high in the vaginal secretions for up to 30 days after disk insertion; radiolabeled antibody was also found, at approximately 100 times lower concentration, in the blood and other tissues. The measured concentrations agreed reasonably well with a simple pharmacokinetic model, which was used to calculate mucosal and systemic concentrations as a function of antibody delivery and elimination rates. Results from the model were consistent with previously reported antibody pharmacokinetic measurements: the half-life for antibody elimination for the vagina was approximately 3 h; the half-life for IgG(1) clearance from the blood was >1 day; and the overall permeability constant for vaginal uptake of IgG was approximately 0.01 to 0.03 h(-1). These results provide important information for the design of controlled antibody delivery devices for vaginal use, and suggest that high-dose, long-term vaginal administration of antibodies may be a reasonable approach for achieving sustained mucosal and systemic antibody levels.     

Comparative activity of Sant7 and anti-IL-6, IL-6R monoclonal antibodies in a murine model of B-cell lymphoma

Interleukin-6 (IL-6) plays a central role in the pathogenesis of several autoimmune and inflammatory diseases as well as B-cell lymphoproliferative disorders. This work describes the effects of the recombinant or adenovirally-delivered IL-6 superantagonist Sant7, anti-IL-6 and IL-6 receptor monoclonal antibodies in a severe murine model of human B-cell lymphoma induced in SCID mice by transplantation of an LCL-41 cell line variant (isotype-switched IgM>IgG). Survival of 60% of the animals treated with anti-gp130 was observed up to day 33, while about 20% of the animals survived with anti-gp80 and Sant7 treatment. No survival was observed with the anti-IL-6 monoclonal antibody treatment. No significant change in serum and peritoneal levels of human IL-6 (hIL-6) and soluble human IL-6 receptor (shIL-6R) was observed in the recombinant Sant7-treated group towards the control group. The anti-gp80 monoclonal antibody induced significant increase of both hIL-6R and hIL-6 in serum and peritoneum. The anti-gp130 monoclonal antibody treatment determined a reduction of the seric shIL-6R and a significant increase of the seric hIL-6. Anti-IL-6 monoclonal antibody administration resulted in a reduction of serum and in an increase of peritoneal hIL-6. Treatment with adenoviral Sant7 was associated with a reduction of circulating shIL-6R, hIgG and mSAP. However, only marginal anti-tumor efficacy of the adenoviral Sant7 was observed. Overall, the present data suggest a potential for anti-hIL-6 therapy in B-cell lymphomas. Less severe animal models might be useful to better evaluate Sant7 efficacy alone or in combination with other anti-IL-6 therapeutics.     

Immunoglobulin G is the main protective antibody in mouse vaginal secretions after vaginal immunization with attenuated herpes simplex virus type 2.

We investigated the protective role of antibodies in vaginal secretions of mice that were immune to vaginal challenge with herpes simplex virus type 2 (HSV-2). Unfractionated vaginal immunoglobulins from immune and nonimmune mice and affinity-purified immunoglobulin G (IgG) and secretory IgA (S-IgA) from immune secretions were adjusted to their concentrations in vivo. Wild-type HSV-2 was incubated in the immunoglobulin preparations for 15 min in vitro, followed by inoculation into vaginae of nonimmune mice. HSV-2 was neutralized by unfractionated antibody and purified IgG from immune secretions but not by unfractionated nonimmune antibody or by purified immune S-IgA. The protective effect of IgG in vivo was investigated by passively transferring purified serum IgG from immune and nonimmune donors to nonimmune recipients before vaginal challenge infection. Immune IgG significantly reduced the percentage of vaginal epithelium infected, concentrations of shed virus protein in the vaginal lumen, and illness scores, even though the viral antibody titers in serum and vaginal secretions of recipient mice at the time of challenge were only 29 and 8%, respectively, of those in actively immunized mice. Additionally, removal of vaginal secretions from immune mice 10 min before vaginal challenge with HSV-2 significantly increased the concentration of shed virus protein in the vaginal lumen after challenge. Collectively, the data indicate that IgG antibody in vaginal secretions of immune mice provides early protection against vaginal challenge infection, probably by neutralizing virus in the vaginal lumen. In contrast, S-IgA antibody contributed relatively little to immune protection of the vagina.     

The chemotherapeutic effect of praziquantel against Schistosoma mansoni is dependent on host antibody response

To assess the role of host humoral immune responses in the mechanism of action of praziquantel (PZQ) against Schistosoma mansoni, the efficacy of the drug was compared in infected B cell-depleted (mu-suppressed) vs immunologically intact C3H/HeN mice. We found that PZQ was on the average only 20% as effective in eliminating adult schistosomes from mu-suppressed as compared with control animals. Indeed, in three of four experiments performed, the drug failed to significantly reduce adult worm burdens in the mu-suppressed mice. These results were not due to a delay in parasite death in the infected B cell-depleted animals, because adult worms recovered from these mice as late as 7 wk after chemotherapy were indistinguishable in number and appearance from those recovered from non-drug-treated animals. The efficacy of PZQ against schistosomes in mu-suppressed mice was completely restored by passive transfer of immune serum from donor mice infected for 6 wk and partially restored with IgG purified from the same sera. Moreover, IgG as well as IgM antibodies were detected by immunofluorescence on the surface of adult worms recovered from intact mice as early as 1 hr after administration of the drug in vivo. The tubercles of the male worms appeared to be a major site for antibody binding. These results formally demonstrate that the mechanism of action of PZQ, the most important anti-schistosomal compound in current use, involves a synergy between the drug and the humoral immune response of the host, and suggest that the relevant effector antibodies act directly against parasite antigens which become exposed on the surface of the worms as a consequence of interaction with the drug.