Recent insights into humoral and cellular immune responses against malaria

Effective immunity to malaria has been clearly demonstrated among individuals naturally exposed to malaria, and can be induced by experimental infections in animals and humans. The large number of malaria antigens has presented a major challenge to identifying protective responses and their targets, and it is likely that robust immunity is mediated by responses to multiple antigens. These include merozoite surface antigens and invasion ligands, variant antigens on the surface of parasitized red blood cells, in addition to sporozoite and liver-stage antigens. Immunity seems to require humoral and cellular immune components, probably in co-operation, although the relative importance of each remains unclear. This review summarizes recent progress towards understanding the targets and mechanisms that are important for mediating immunity to malaria.     

Effect of ivermectin on the cellular and humoral immune responses of rabbits

The objective of this paper is to determine the effect of ivermectin administration on cell mediated (CMI) and humoral immunity (HI) of rabbits. CMI against dinitrochlorobenzene (DNCB) and sheep red blood cells (SRBC) in rabbits was determined by delayed-type hypersensitivity and macrophage engulfment assay (MEA), respectively; whereas, HI to Pasteurella multocida B2 vaccine and SRBC was determined by indirect haemagglutination assay (IHA) and Jerne hemolytic plaque formation assay (JHPFA), respectively. The rabbits were divided into four major groups (A through D) each subdivided into four sub-groups (1 through 4). Rabbits of group A served as vehicle control while those of groups B, C and D were treated with ivermectin at the dose rates of 200 microg/kg, 400 microg/kg and 600 microg/kg b.w., respectively. Cellular immunity was determined in sub-groups 1 and 2 through DNCB and MEA, respectively while HI was determined in sub-groups 3 and 4 through IHA and JHPFA, respectively. The skin sensitivity to DNCB at 24 and 48 h and macrophage engulfment of SRBC were highest (P>0.05) in rabbits administered with 600 microg/kg b.w. The highest geometric mean titers (14.00+/-0.31) and number of plaque forming units (1860+/-0.75) were found in rabbits that received ivermectin at a dose of 600 microg/kg b.w. followed, in order by the groups that received 400 microg/kg, 200 microg/kg b.w. and controls. Leukocyte counts were significantly higher in ivermectin-treated groups (C and D) than group A (vehicle control) and B (ivermectin at the rate of 200 microg/kg). A graded dose immune response suggested an immunopotentiating effect of ivermectin at higher doses.     

The enhancement of humoral and cellular immune responses by dimethyldioctadecylammonium bromide

Dimethyldioctadecylammonium bromide (DDA) produced marked enhancement of both cellular and humoral immune responses to SRBC when administered to mice intraperitoneally, or of cellular immunity when given subcutaneously. Stimulated cellular responses were seen as increased footpad swelling as a measure of delayed hypersensitivity and increased antigen-induced blastogenesis. Elevation of humoral response was reflected in increased numbers of splenic plaque-forming cells (PFC) and in circulating anti-SRBC antibody. Adjuvancy did not depend on addition of the lipid of DDA to antigen, as both humoral and cellular responses were enhanced whether DDA and SRBC were admixed or injected separately 4 hr apart intraperitoneally. DDA also enhanced the PFC response to the T-cell independent antigen TNP-LPS. The DDA effects are accompanied by macrophage activation, which may mediate at least in part the observed responses. DDA-activated macrophages exhibit fast spreading, are highly phagocytic, and elaborate significantly greater amounts of thymocyte mitogenic factor(s) than do normal resident peritoneal macrophages. This activation may effect the stimulation of antigen-specific primary lymphocyte responses by adjuvant and expansion of memory-cell populations which lead to the observed enhancement of secondary responses.     

Bacteria-derived human leukocyte interferons alter in vitro humoral and cellular immune responses

Cultures of gradient-purified human peripheral blood mononuclear cells (PBMC) have been employed to examine the effects of three bacteria-derived human leukocyte interferon subtypes on certain aspects of in vitro immune responses. The addition of highly purified IFN-alpha 1, -alpha 2, -alpha 2/alpha 1 to PMBC cultures stimulated with phytohemagglutinin (PHA) or pokeweed mitogen resulted in a significant suppression of the mitogenic response. This suppression required the presence of interferon in the cultures because pretreatment of cells and removal of interferon had no effect on their response to PHA. The presence of these interferons at 200 U/ml also caused a substantial reduction of human mixed-lymphocyte reactions (MLR) as measured by [3H]thymidine incorporation by responder cells. Interestingly, pretreatment of stimulator cells was sufficient for this reduction to occur whereas pretreatment of responder cells had no effect on their ability to respond to allogenic stimulation. In contrast to these suppressive effects, the three interferons enhanced human in vitro primary immune response to sheep red blood cells (SRBC). These data demonstrate that both purified interferon subtypes and genetic hybrids of human interferons produced by recombinant DNA technology have effects on in vitro immune responses.     

Immunostimulant adjuvant patch enhances humoral and cellular immune responses to DNA immunization

The focus of this report is on the development of an improved DNA immunization protocol, which takes advantage of the strengths of DNA immunization, as well as those associated with adjuvant delivered by transcutaneous immunostimulatory (IS) patches. Because transcutaneous delivery of adjuvants to the skin at the vaccination site has been shown to amplify the immune response to protein antigens, we hypothesized that the same IS patch when placed on the skin at the site of DNA injection could further enhance the immune response to a DNA influenza vaccine. We have combined an influenza DNA vaccine, hemagglutinin fused with three copies of complement C3d, to enhance uptake and antigen presentation, with an IS patch containing heat-labile enterotoxin from Escherichia coli. Coadministration of a potent adjuvant in IS patches placed on the skin at the site of DNA vaccination dramatically amplifies anti-influenza antibody immune response. Supplementing DNA vaccines with IS patches may be a particularly valuable strategy because DNA vaccines can be rapidly modified in response to mutations in pathogens, and individuals with compromised immune systems such as transplant patients and the elderly will benefit from the enhanced antibody response induced by the IS patches.     

Liposome encapsulated tumor-associated antigens elicited humoral and cellular immune responses in mice bearing tumor

Chemically induced tumors in mice provide a system to investigate tumor-associated antigens (TAA). The cell surface glycoprotein antigens on such tumor cells have been identified as suitable targets for immune attack. The induction of immune responses against (TAA) in N-nitrosodiethylamine (DEN) exposed mice has been examined. In order to present antigens to the immune system, the liposome was used as vehicle to deliver the TAA. Liposomal-TAA formulation, elicited both humoral and the cellular immune responses, when administered intramuscularly in DEN-exposed mice. Presence of circulatory antibodies against TAA and the induction of cellular responses in immunized mice were monitored using ELISA and in vitro cell proliferation assay of lymphocytes respectively. Specificity of antibody against TAA in immune sera was analysed using immunoblotting technique. Based on these results, it is proposed that the liposome encapsulated TAA may successfully be used to induce humoral and cellular immune responses against tumor.     

Trehalose-6-phosphate Phosphatase from Mycobacterium tuberculosis induces humoral and cellular immune responses

Trehalose-6-phosphate phosphatase is an enzyme strictly essential for the growth of mycobacteria. Subcellular fractionation of Mycobacterium tuberculosis and M. bovis bacillus Calmette-Guérin (BCG) located the trehalose-6-phosphate phosphatase in the cell wall and membrane fractions. Trehalose-6-phosphate phosphatase induced an increased Th1-type immune response in mice, characterized by an elevated level of interferon-gamma in antigen-stimulated splenocyte culture and a strong IgG2a antibody response. The trehalose-6-phosphate phosphatase was recognized by the sera of tuberculosis patients and BCG-vaccinated donors. The mycobacterial trehalose-6-phosphate phosphatase is an immunodominant antigen, and it may be a candidate for vaccine development for the control of tuberculosis.     

Leptin signaling deficiency impairs humoral and cellular immune responses and attenuates experimental arthritis.

Leptin is produced almost exclusively by adipocytes and regulates body weight at the hypothalamic level. In addition, recent studies showed that leptin plays an important role in T lymphocyte responses. To examine the role of leptin in Ag-induced arthritis, the development of joint inflammation was assessed in immunized leptin-deficient mice (ob/ob), +/?, and wild-type mice (+/+) following the administration of methylated BSA into the knees. The results showed that ob/ob mice developed less severe arthritis compared with control mice. The levels of IL-1beta and TNF-alpha mRNA in the synovium of arthritic knees were lower in ob/ob than in +/? mice. In vitro Ag-specific T cell proliferative responses were significantly decreased in ob/ob mice with lower IFN-gamma and higher IL-10 production, suggesting a shift toward a Th2-type response in ob/ob mice. The serum levels of anti-methylated BSA Abs of any isotype were significantly decreased in arthritic ob/ob mice compared with controls. Essentially identical results were obtained in db/db mice, which lack the expression of the long isoform of leptin receptor. By RT-PCR, we observed that B lymphocytes express leptin receptor mRNA, indicating that in addition to its effect on the cellular response, leptin may exert a direct effect on B cell function. In conclusion, leptin contributes to the mechanisms of joint inflammation in Ag-induced arthritis by regulating both humoral and cell-mediated immune responses.     

Replication-defective adenovirus serotype 5 vectors elicit durable cellular and humoral immune responses in nonhuman primates

The magnitude and durability of immune responses induced by replication-defective adenovirus serotype 5 (ADV5) vector-based vaccines were evaluated in the simian-human immunodeficiency virus/rhesus monkey model. A single inoculation of recombinant ADV5 vector constructs induced cellular and humoral immunity, but the rapid generation of neutralizing anti-Ad5 antibodies limited the immunity induced by repeated vector administration. The magnitude and durability of the immune responses elicited by these vaccines were greater when they were delivered as boosting immunogens in plasmid DNA-primed monkeys than when they were used as single-modality immunogens. Therefore, administration of ADV5-based vectors in DNA-primed subjects may be a preferred use of this vaccine modality for generating long-term immune protection.     

Immunization with hepatitis C virus-like particles induces humoral and cellular immune responses in nonhuman primates

We have previously reported the production of hepatitis C virus-like particles (HCV-LP) using a recombinant baculovirus containing the cDNA of the HCV structural proteins (core, E1, and E2). These particles resemble the putative HCV virions and are capable of inducing strong and broad humoral and cellular immune responses in mice. Here we present evidence on the immunogenicity of HCV-LP and the effects of novel adjuvant systems in a nonhuman primate model, the baboon. Three groups of four baboons were immunized with HCV-LP, HCV-LP and adjuvant AS01B (monophosphoryl lipid A and QS21), or HCV-LP and the combination of AS01B and CpG oligodeoxynucleotides 10105. After four immunizations over an 8-month period, all animals developed HCV-specific humoral and cellular immune responses including antibodies to HCV structural proteins and gamma interferon(+) (IFN-gamma(+))CD4(+) and IFN-gamma(+)CD8(+) T-cell responses. The immunogenicity of HCV-LP was only marginally enhanced by the use of adjuvants. The overall HCV-specific immune responses were broad and long lasting. Our results suggest that HCV-LP is a potent immunogen to induce HCV-specific humoral and cellular immune responses in primates and may be a promising approach to develop novel preventive and therapeutic modalities.     

Peptides mimicking GD2 ganglioside elicit cellular, humoral and tumor-protective immune responses in mice

Introduction Because of its restricted distribution in normal tissues and its high expression on tumors of neuroectodermal origin, GD2 ganglioside is an excellent target for active specific immunotherapy. However, GD2 usually elicits low-titered IgM and no IgG or cellular immune responses, limiting its usefulness as a vaccine for cancer patients. We have previously shown that anti-idiotypic monoclonal antibody mimics of GD2 can induce antigen-specific humoral and cellular immunity in mice, but inhibition of tumor growth by the mimics could not be detected. Methods and results Here, we isolated two peptides from phage display peptide libraries by panning with GD2-specific mAb ME361. The peptides inhibited binding of the mAb to GD2. When coupled to keyhole limpet hemocyanin (KLH) or presented as multiantigenic peptides in QS21 adjuvant, the peptides induced in mice antibodies binding specifically to GD2 and delayed-type hypersensitive lymphocytes reactive specifically with GD2-positive D142.34 mouse melanoma cells. Induction of delayed-type hypersensitivity (DTH) reaction was dependent on CD4-positive lymphocytes. The immunity elicited by the peptides significantly inhibited growth of GD2-positive melanoma cells in mice. Conclusion Our study suggests that immunization with peptides mimicking GD2 ganglioside inhibits tumor growth through antibody and/or CD4-positive T cell-mediated mechanisms. Cytolytic T lymphocytes most likely do not play a role. Our results provide the basis for structural analysis of carbohydrate mimicry by peptides. A. Wondimu and T. Zhang contributed equally to this work.     

Benzylideneacetone suppresses both cellular and humoral immune responses of Spodoptera exigua and enhances fungal pathogenicity

An entomopathogenic fungus, Beauveria bassiana, had significant insecticidal activity against the beet armyworm, Spodoptera exigua. However, it took almost one week to cause significant mortality. This study used a mixture treatment with an immunosuppressant to enhance the fungal pathogenicity. A bacterial metabolite, benzylideneacetone (BZA), had a significant synergistic effect on the fungal pathogenicity against S. exigua, although it had little insecticidal activity by itself. The mixture treatment shortened median lethal time of B. bassiana by approximately 2 days. The synergistic activity of BZA on the pathogenicity of B. bassiana was induced by its immunosuppressive effects on both cellular and humoral antifungal responses of S. exigua. In response to B. bassiana, S. exigua larvae can form hemocytic nodules. Nodules were significantly suppressed by BZA treatment. Moreover, BZA inhibited expression of some antimicrobial peptide genes of S. exigua in response to fungal challenge. The immunosuppressive condition induced by BZA allowed B. bassiana to easily colonize and multiply in the hemocoel of treated larvae, which resulted in significant enhancement of the pathogenicity of B. bassiana.     

Dirofilaria immitis: Parasite-specific humoral and cellular immune responses in experimentally infected dogs

Humoral and cellular immune responses to adult antigens of Dirofilaria immitis were evaluated in experimentally infected dogs during the chronic phase of infection. All infected dogs had significantly elevated IgG (enzyme-linked immunosorbent assay) and IgE (passive cutaneous anaphylaxis) titers against D. immitis adult antigens. However, there was little difference between infected dogs and uninfected controls in cellular-immune responses to D. immitis adult antigen or phytohemagglutinin as assessed by the lymphocyte transformation assay. Although neither cellular nor humoral responses correlated with worm burdens, cellular responses among infected dogs correlated inversely with IgG titers to D. immitis adult antigen. These results are consistent with observations in other nematode and trematode systems which suggest that in chronic tissue helminth infections there is suppression of cellular immune responses to parasite antigens while humoral responses to the same antigens remain relatively preserved.     

Stimulatory effects of B7-related protein-1 on cellular and humoral immune responses in mice

Inducible costimulator (ICOS) and B7-related protein-1 (B7RP-1) constitute a receptor-ligand pair involved in T cell costimulation. In this study, the stimulatory effects of B7RP-1 on cellular and humoral immune responses were investigated giving mice a construct with the extracellular domain of murine B7RP-1 fused with human IgG1 Fc (B7RP-1-Fc). B7RP-1-Fc stimulated contact hypersensitivity (CH) given near either the time of sensitization or challenge with oxazolone. When given near challenge time, B7RP-1-Fc stimulated CH more than a construct containing the extracellular domain of murine B7.2 and Fc (B7.2-Fc). B7RP-1-Fc increased the number of cells in lymph nodes draining the skin sensitized with oxazolone, especially activated T cells. B7RP-1-Fc also increased the ability of the cells in these lymph nodes to induce CH when transfused into naive mice. B7RP-1-Fc stimulated the production of anti-keyhole limpet hemocyanin (KLH) Ab, increasing anti-KLH IgG, IgG2a, and IgE, whereas B7.2-Fc did not affect this production. B7RP-1-Fc also increased the number of cells in lymph nodes draining the skin immunized with KLH and their production of IFN-gamma, IL-4, and IL-10 in response to KLH. Finally, B7RP-1-Fc increased the presence of eosinophils in the bronchoalveolar lavage and lungs of mice sensitized and challenged with OVA so to mount an asthmatic reaction. B7RP-1-Fc stimulates both cellular and humoral immune responses in vivo by increasing number and function of T and B cells reacting to Ag exposure.     

Nasal-associated lymphoid tissue is a mucosal inductive site for virus-specific humoral and cellular immune responses

Peyer's patches are known as mucosal inductive sites for humoral and cellular immune responses in the gastrointestinal tract. In contrast, functionally equivalent structures in the respiratory tract remain elusive. It has been suggested that nasal-associated lymphoid tissue (NALT) might serve as a mucosal inductive site in the upper respiratory tract. However, typical signs of mucosal inductive sites like development of germinal center reactions after Ag stimulation and isotype switching of naive B cells to IgA production have not been directly demonstrated. Moreover, it is not known whether CTL can be generated in NALT. To address these issues, NALT was structurally and functionally analyzed using a model of intranasal infection of C3H mice with reovirus. FACS and histological analyses revealed development of germinal centers in NALT in parallel with generation and expansion of IgA(+) and IgG2a(+) B cells after intranasal reovirus infection. Reovirus-specific IgA was produced in both the upper respiratory and the gastrointestinal tract, whereas production of reovirus-specific IgG2a was restricted to NALT, submandibular, and mesenteric lymph nodes. Moreover, virus-specific CTL were detected in NALT. Limiting dilution analysis showed a 5- to 6-fold higher precursor CTL frequency in NALT compared with a cervical lymph node. Together these data provide direct evidence that NALT is a mucosal inductive site for humoral and cellular immune responses in the upper respiratory tract.