Immune response to chemically modified flagellin. I. Induction of antibody tolerance to flagellin by acetoacetylated derivatives of the protein

Pathogen Dose in Animal Models of Hemorrhagic Fever Virus Infections and the Potential Impact on Studies of the Immune Response

Viral hemorrhagic fever viruses come from a wide range of virus families and are a significant cause of morbidity and mortality worldwide each year. Animal models of infection with a number of these viruses have contributed to our knowledge of their pathogenesis and have been crucial for the development of therapeutics and vaccines that have been approved for human use. Most of these models use artificially high doses of virus, ensuring lethality in pre-clinical drug development studies. However, this can have a significant effect on the immune response generated. Here I discuss how the dose of antigen or pathogen is a critical determinant of immune responses and suggest that the current study of viruses in animal models should take this into account when developing and studying animal models of disease. This can have implications for determination of immune correlates of protection against disease as well as informing relevant vaccination and therapeutic strategies.

Physical Extraction and Fast Protein Liquid Chromatography for Purifying Flagella Filament From Uropathogenic Escherichia coli for Immune Assay

Flagella are expressed on the surface of a wide range of bacteria, conferring motility and contributing to virulence and innate immune stimulation. Host-pathogen interaction studies of the roles of flagella in infection, including due to uropathogenic Escherichia coli (UPEC), have used various methods to purify and examine the biology of the major flagella subunit protein, FliC. These studies have offered insight into the ways in which flagella proteins interact with host cells. However, previous methods used to extract and purify FliC, such as mechanical shearing, ultracentrifugation, heterologous expression in laboratory E. coli strains, and precipitation-inducing chemical treatments have various limitations; as a result, there are few observations based on highly purified, non-denatured FliC in the literature. This is especially relevant to host-pathogen interaction studies such as immune assays that are designed to parallel, as closely as possible, naturally-occurring interactions between host cells and flagella. In this study, we sought to establish a new, carefully optimized method to extract and purify non-denatured, native FliC from the reference UPEC strain CFT073 to be suitable for immune assays. To achieve purification of FliC to homogeneity, we used a mutant CFT073 strain containing deletions in four major chaperone-usher fimbriae operons (type 1, F1C and two P fimbrial gene clusters; CFT073Δ4). A sequential flagella extraction method based on mechanical shearing, ultracentrifugation, size exclusion chromatography, protein concentration and endotoxin removal was applied to CFT073Δ4. Protein purity and integrity was assessed using SDS-PAGE, Western blots with anti-flagellin antisera, and native-PAGE. We also generated a fliC-deficient strain, CFT073Δ4ΔfliC, to enable the concurrent preparation of a suitable carrier control to be applied in downstream assays. Innate immune stimulation was examined by exposing J774A.1 macrophages to 0.05-1 μg of purified FliC for 5 h; the supernatants were analyzed for cytokines known to be induced by flagella, including TNF-α, IL-6, and IL-12; the results were assessed in the context of prior literature. Macrophage responses to purified FliC encompassed significant levels of several cytokines consistent with prior literature reports. The purification method described here establishes a new approach to examine highly purified FliC in the context of host-pathogen interaction model systems.

Immunity to intestinal pathogens: lessons learned from Salmonella

Salmonella are a common source of food- or water-borne infection and cause a wide range of clinical disease in human and animal hosts. Salmonella are relatively easy to culture and manipulate in a laboratory setting, and the infection of laboratory animals induces robust innate and adaptive immune responses. Thus, immunologists have frequently turned to Salmonella infection models to expand understanding of host immunity to intestinal pathogens. In this review, I summarize current knowledge of innate and adaptive immunity to Salmonella and highlight features of this response that have emerged from recent studies. These include the heterogeneity of the antigen-specific T-cell response to intestinal infection, the prominence of microbial mechanisms to impede T- and B-cell responses, and the contribution of non-cognate pathways for elicitation of T-cell effector functions. Together, these different issues challenge an overly simplistic view of host-pathogen interaction during mucosal infection, but also allow deeper insight into the real-world dynamic of protective immunity to intestinal pathogens.

Rapid CD4+ T-cell responses to bacterial flagellin require dendritic cell expression of Syk and CARD9

Toll-like receptors (TLRs) can recognize microbial patterns and utilize adaptor molecules, such as-MyD88 or (TRIF TIR-domain-containing adapter-inducing interferon-β), to initiate downstream signaling that ultimately affects the initiation of adaptive immunity. In addition to this inflammatory role, TLR5 expression on dendritic cells can favor antigen presentation of flagellin peptides and thus increase the sensitivity of flagellin-specific T-cell responses in vitro and in vivo. Here, we examined the role of alternative signaling pathways that might regulate flagellin antigen presentation in addition to MyD88. These studies suggest a requirement for spleen tyrosine kinase, a noncanonical TLR-signaling adaptor molecule, and its downstream molecule CARD9 in regulating the sensitivity of flagellin-specific CD4(+) T-cell responses in vitro and in vivo. Thus, a previously unappreciated signaling pathway plays an important role in regulating the dominance of flagellin-specific T-cell responses.

CD103-CD11b+ dendritic cells regulate the sensitivity of CD4 T-cell responses to bacterial flagellin

Toll-like receptor 5 (TLR5) has been widely studied in an inflammatory context, but the effect of TLR5 on the adaptive response to bacterial flagellin has received considerably less attention. Here, we demonstrate that TLR5 expression by dendritic cells (DCs) allows a 1,000-fold enhancement of T-cell sensitivity to flagellin, and this enhancement did not require the expression of NLRC4 or Myd88. The effect of TLR5 on CD4 T-cell sensitivity was independent of the adjuvant effect of flagellin and TLR5 ligation did not alter the sensitivity of ovalbumin (OVA)-specific T cells to OVA. In the spleen, the exquisite T-cell sensitivity to flagellin was regulated by CD4-CD8α- DCs and was blocked by a monoclonal antibody to TLR5. In the mesenteric lymph nodes, flagellin-specific T-cell activation was regulated by a population of CD103-CD11b+ DCs. Thus, TLR5 expression by mucosal and systemic DC subsets controls the sensitivity of the adaptive immune response to flagellated pathogens.

NDV-3 protects mice from vulvovaginal candidiasis through T- and B-cell immune response

We have previously reported that vaccination with rAls3p-N protein of Candida albicans, formulated with alum adjuvant (also designated as NDV-3) protects immunocompetent mice from, lethal disseminated candidiasis and mucosal oropharyngeal candidiasis. NDV-3 vaccine was recently, tested in a Phase 1 clinical trial and found to be safe, well-tolerated, and induced robust humoral and, cellular immune responses with increased interferon (IFN)-gamma and interleukin (IL)-17 secretion. In preparation for a Phase 2 clinical trial against vulvovaginal candidiasis (VVC), we evaluated NDV-3, efficacy in a murine VVC model. Here, NDV-3 induced a strong immune response characterized by high, anti-rAls3p-N serum IgG and vaginal IgA titers. Furthermore, moderate doses of the vaccine (a range of 1-30μg given subcutaneously [SQ] or 0.3-10μg given intramuscularly [IM]) elicited a 10-1000 fold, decrease in vaginal fungal burden vs. control (mice injected with alum adjuvant alone) in both inbred, and outbred mice infected with different clinical C. albicans isolates. Additionally, NDV-3 required both, T and B lymphocytes for efficacy in reducing C. albicans tissue burden, which is followed by a reduction, in neutrophil influx to the affected site. Finally, anti-rAls3p-N antibodies enhanced the ex vivo killing, of C. albicans by neutrophils primed with IFN-gamma. These data indicate that NDV-3 protects mice, from VVC by a mechanism that involves the concerted priming of both humoral and adaptive immune, responses.

More stories on Th17 cells

For more than two decades, immunologists have been using the so-called Th1/Th2 paradigm to explain most of the phenomena related to adaptive immunity. The Th1/Th2 paradigm implied the existence of two different, mutually regulated, CD4(+) T helper subsets: Th1 cells, driving cell-mediated immune responses involved in tissue damage and fighting infection against intracellular parasites; and Th2 cells that mediate IgE production and are particularly involved in eosinophilic inflammation, allergy and clearance of helminthic infections. A third member of the T helper set, IL-17-producing CD4(+) T cells, now called Th17 cells, was recently described as a distinct lineage that does not share developmental pathways with either Th1 or Th2 cells. The Th17 subset has been linked to autoimmune disorders, being able to produce IL-17, IL-17F and IL-21 among other inflammatory cytokines. Interestingly, it has been reported that there is not only a cross-regulation among Th1, Th2 and Th17 effector cells but there is also a dichotomy in the generation of Th17 and T regulatory cells. Therefore, Treg and Th17 effector cells arise in a mutually exclusive fashion, depending on whether they are activated in the presence of TGF-beta or TGF-beta plus inflammatory cytokines such as IL-6. This review will address the discovery of the Th17 cells, and recent progress on their development and regulation.

Vaccination with recombinant N-terminal domain of Als1p improves survival during murine disseminated candidiasis by enhancing cell-mediated, not humoral, immunity

Candida spp. are opportunistic fungal pathogens that are among the most common causes of nosocomial bloodstream infections. The mortality attributable to disseminated candidiasis is 40 to 50% despite antifungal therapy. Clearly, new strategies are needed to prevent this life-threatening infection. Because risk factors for disseminated candidiasis are well defined and frequently of limited duration, vaccination is an appealing prophylactic strategy. We have identified a cell surface protein, Als1p, that mediates adherence of Candida albicans to a variety of human substrates and plastic. Here we report that immunizing BALB/c mice with the recombinant N-terminal domain of Als1p (rAls1p-N) improved survival during a subsequent challenge with a lethal inoculum of C. albicans. The protective 20-mug dose of rAls1p-N significantly increased Candida stimulation of Th1 splenocytes and increased in vivo delayed-type hypersensitivity. In contrast, antibody titers did not correlate with protection. Finally, the vaccine was not protective in T-cell-deficient mice but was protective in B-cell-deficient mice. These data indicate that the mechanism of action of the rAls1p-N vaccine is stimulation of cell-mediated, rather than humoral, immunity against C. albicans. The majority of efforts to date have focused on the development of passive immunization strategies to prevent or treat disseminated candidiasis. In contrast, our results provide proof of principle for vaccination with an adhesin of C. albicans and emphasize the potential for cell-mediated immune modulation as a prophylactic or therapeutic strategy against disseminated candidiasis.

Parenchymal organ, and not splenic, immunity correlates with host survival during disseminated candidiasis

We examined the relationship between host survival and renal and splenic immune responses in a murine model of hematogenously disseminated candidiasis. Male BALB/c mice were infected via tail vein injection with wild-type C. albicans or with an isogenic, Deltaefg1/Deltaefg1 hypha-deficient mutant. Host survival, organ fungal burden, intracellular cytokine content of splenic and kidney lymphocytes, and whole-organ cytokine profiles were determined. Wild-type C. albicans induced type 2 splenocyte responses with both nonfatal and fatal inocula. In the kidney, conversely, wild-type inocula causing no or low mortality induced type 1 responses and 100% fatal inocula induced type 2 or interleukin-10 (IL-10)-dominant responses. Hypha-deficient mutant C. albicans caused no or low mortality while inducing type 1 responses in both the spleen and kidney. To our knowledge, this is the first demonstration that host survival during systemic infection correlates with the type of immune response engendered in a nonlymphoid, parenchymal organ and not with the response in the spleen. Furthermore, the results provide in vivo confirmation that hyphal formation by C. albicans induces type 2 or IL-10-dominant host responses in tissues.

T-Independent IgA Responses to Microbial Polysaccharides

There is accumulating evidence indicating the presence in vivo of T-independent routes of IgA response in addition to the conventional T-dependent IgA response. Factors influencing these alternative pathways of IgA responses may include the structural characteristics of a stimulating antigen, the nature of responding B cells, and the microenvironment. The structural complexity of polysaccharide antigens has made it difficult to summarize a general scheme for the antibody responses they induce. Instead, one may expect that each individual polysaccharide may be able to create a unique microenvironment by activation of specific cell populations in the repertoires of non-T cell types. A specific pattern of B cell response may thus be elicited by TI stimulation. Recognition of such a unique property of a TI antigens is necessary for us to better understand the T-independent IgA response. Information obtained may have an impact on the development of vaccination strategies directed at the mucosal immunity mediated by IgA antibodies.

Breast cancer immunotherapy: current status and future prospects

The development of an immunotherapeutic approach to cancer is the concern for many immunologists, but despite the impressive progress over the past decade, such as the identification of tumour antigens and antigenic peptides as potential targets, there are still many obstacles in eliciting an effective immune response to eradicate cancer. Mucins have attracted interest as potential targets for immunotherapy in the development of vaccines for cancers expressing Mucin1 (MUC1; e.g. breast, pancreas, ovary etc.). All of the identified targets for cancer, including MUC1, are normal proteins; however MUC1 expressed on tumours can be considered as tumour specific due to their overexpression, altered glycosylation and its ubiquitous distribution on the cell surface rather than at the secretory pole in adenocarcinomas. These observations have led to the development of several different approaches to immunize against breast cancer using synthetic carbohydrates or peptides conjugated to carriers and given together with a variety of adjuvants to elicit the appropriate immune response. Mannan, a polymannose carbohydrate isolated from the cell wall of yeast, is an appropriate and effective protein carrier for eliciting a cellular (T1-type) or humoral (T2-type) immune response depending on the mode of conjugation (oxidized or reduced). In addition, mannan holds promise and opens many avenues as a carrier for vaccine development for other antigens. Several clinical trials are in progress to evaluate the immunogenicity of MUC1 and its suitability as to use for immunotherapy/vaccine for breast cancer.

Immune deviation: a historical perspective

In this paper I have reviewed my early studies, between 1966 and 1976, on the phenomenon of immune deviation. Initially summarized are experiments with different forms of the flagellin antigen from Salmonella adelaide which established the inverse relationship between delayed-type hypersensitivity (DTH) and antibody formation. Based on the flagellin studies, many of the key factors which determine whether an antigen will induce either DTH or antibody formation were delineated. These factors are just as relevant today as they were 25 years ago. Subsequent analyses at the cellular level demonstrated that different T cell subsets mediate DTH and T cell help and maintain immune deviation by suppressor mechanisms. A number of fundamental questions raised by this early work remain unanswered and are discussed. These include the nature of the primary signalling events which initiate immune deviation, the role of B cells in the deviating process and the mechanism by which CD8+T cells suppress antibody production.

Priming for virus-specific CD8+ but not CD4+ cytotoxic T lymphocytes with synthetic lipopeptide is influenced by acylation units and liposome encapsulation

Synthetic peptides of the herpes simplex virus glycoprotein B synthesized either as a free form or derivatized with one (PAM1) or three palmitic acids (PAM3Cys) were used to assess the in vivo priming efficacy of high affinity virus-specific CTL induction. The peptide and its derivatives were delivered in vivo with or without liposome encapsulation. Neither the free peptide nor the PAM1 derivative primed for high affinity virus specific CD8+ CTL induction, whether delivered via liposomes or not. On the other hand, the PAM3Cys derivative was able to prime for low levels of high affinity virus specific CD8+ CTL induction in the absence of liposome encapsulation. However, the efficiency of virus-specific CD8+ CTL induction with PAM3Cys derivative was enhanced following encapsulation in the liposomes. In contrast, all forms of the peptides induced both CD4+ T cell proliferative response as well as high affinity virus-specific CD4+ CTL. In addition, the efficiency of the PAM3Cys derivative to prime for CD4+ or CD8+ CTL was found to be influenced by the liposome encapsulation. When delivered via liposomes, the PAM3Cys derivative effectively primed for CD8+ CTL. However, liposomal delivery was not necessary for efficient priming for CD4+ CTL induction. Thus, both the acylation units as well as liposomal delivery appear to influence the in vivo priming of CD4+ and CD8+ T cell responses with synthetic peptides.

Extent of T cell receptor ligation can determine the functional differentiation of naive CD4+ T cells

Naive CD4+ T cells can differentiate into cells predominantly involved in humoral immunity, known as T helper type 2 cells (Th2), or cells involved in cell-mediated immunity, known as Th1 cells. In this report, we show that priming of CD4+ T cells bearing a transgene-encoded T cell receptor can lead to differentiation into Th1-like cells producing abundant interferon gamma when the cells are exposed to high antigen doses, while low doses of the same peptide induce cells with the same T cell receptor to differentiate into Th2-like cells producing abundant interleukin 4. Thus antigen dose is one factor that can control the differentiation fate of a naive CD4+ T cell.

Oxidative/reductive conjugation of mannan to antigen selects for T1 or T2 immune responses

The induction of CD8+ cytotoxic T lymphocytes (CTLs) is desirable for immunization against many diseases, and recombinant-synthetic peptide antigens are now favored agents to use. However, a major problem is how to induce CTLs, which requires a T1-type response to such synthetic antigens. We report that T1-type (generating high CTL, low antibody) or T2-type (the reciprocal) responses can be induced by conjugation of the antigen to the carbohydrate polymer mannan: T1 responses are selected by using oxidizing conditions; T2 responses are selected by using reducing conditions for the conjugation. Using human MUC1 as a model antigen in mice, immunization with oxidized mannan-MUC1 fusion protein (ox-M-FP) led to complete tumor protection (challenge up to 5 x 10(7) MUC1+ tumor cells), CTLs, and a high CTL precursor (CTLp) frequency (1/6900), whereas immunization with reduced mannan-MUC1 FP (red-M-FP) led to poor protection after challenge with only 10(6) MUC1+ tumor cells, no CTLs, and a low CTLp frequency (1/87,800). Ox-M-FP selects for a T1 response (mediated here by CD8+ cells) with high interferon gamma (IFN-gamma) secretion, no interleukin 4 (IL-4), and a predominant IgG2a antibody response; red-M-FP selects for a T2-type response with IL-4 production and a high predominant IgG1 antibody response but no IFN-gamma.

Delivery of protein antigen to the major histocompatibility complex class I-restricted antigen presentation pathway

Major histocompatibility complex (MHC) class I-restricted antigen presentation normally requires a protein antigen to be synthesized in the cytosol of the antigen presenting cell (APC). Exogenous protein antigen could gain access to the class I presentation pathway if the protein is introduced into the cytosolic compartment of the APC. Approaches which release the protein antigen from endocytic vesicles have been employed to deliver protein antigen for the recognition by class I-restricted cytotoxic T lymphocytes (CTL). These include osmotic shock, electroporation, cationic and pH-sensitive liposomes. An alternative approach is to deliver a gene that encodes the protein antigen. In this case, the APC is transfected with a gene which synthesizes the "exogenous protein" in the cytosol. Delivery of protein antigen targeted for CTL induction in vivo follows a different strategy and generally requires an antigen carrier of lipidic/membranous nature, such as liposomes, immunostimulating complexes, and/or lipid conjugates. Macrophages that are responsible for scavenging the antigen play an important role in CTL induction. An optimal CTL inductive vaccine must contain other immuno-modulatory activities in addition to its activity in delivering antigen to the class I pathway. Attempts to attenuate viral infection and to improve anti-tumor immunity have been successful by delivering the exogenous antigen entrapped in liposomes. These animal model studies should be of great value in the development of potential vaccine formulation.

Palmitic acid conjugation of a protein antigen enhances major histocompatibility complex class II-restricted presentation to T cells

The effect on antigenicity of covalent attachment of lipid groups to a protein antigen was investigated. Coupling of palmitic acid to ovalbumin (OVA) enhanced major histocompatibility complex (MHC) class II-restricted presentation to most OVA-specific murine T-cell clones in vitro. The enhanced antigenicity of palmitoylated antigen was localized to the level of presentation of the synthetic peptide epitope, OVA 323-339. T-cell responses to palmitoylated antigen were more difficult to block with anti-MHC class II antibodies than responses to native antigen. However, T-cell proliferation to palmitoyl (p)-OVA and native (n)-OVA were blocked equally by anti-CD4 antibodies. Taken together, the results suggest that lipid conjugation of a protein antigen leads to the formation of a lipopeptide T-cell epitope with increased affinity of binding to MHC class II and/or T-cell receptor (TcR). These results have implications for the design of synthetic peptide vaccines.

Chemical modification and immunogenicity of membrane fractions from mouse tumour cells

A crude membrane fraction isolated from mouse tumour cells was treated with various chemicals. The effects on the immunogenicity of the membrane sample were tested in syngeneic mice for tumour protection, using a challenge dose of 10(5) viable tumour cells. Best protection was obtained after immunization of mice with a membrane sample modified with dimethylsulphate. Up to 60% of the animals remained tumour free, and the tumour-bearing animals showed a greatly increased mean survival time. The post-challenge sera contained no detectable amounts of cytotoxic antibodies. The membrane sample isolated from tumour cells which had been modified with dimethylsulphate showed less immunogenicity than the modified cells or the membrane fraction from unmodified cells.

Localization of antigenic activity and immunogenic capacity in different conformational domains of procollagen peptide

The antibody response to the amino-terminal CNBr peptide of sheep procollagen which consists of a globular and a collagenous segment, was studied in inbred strains of mice. The determinants reacting with antibody could be localized in the globular domain and were lost by reduction of disulfide bridges. The ability to induce an antibody response required the collagen-like sequences and was independent of the triple-helical conformation of this segment. The data were interpreted as indicating a different conformation dependence of hapten and carrier determinants.

Dimethyl diotadecyl ammonium bromide as adjuvant for delayed hypersensitivity in mice

Immunization of mice with antigen mixed with cationic surface active lipid dimethyl dioctadecyl ammonium bromide (DDA) produced delayed type hypersensitivity (DH), measured as a footpad swelling. The DH to sheep red blood cells or dinitrophenyl conjugated with bovine serum albumin (DNP28-BSA) in DDA exceeded the response of the same antigens in Freund's Complete Adjuvant (FCA) significantly. Treatment of mice with CY 8 hr prior to the injection of antigen in FCA or DDA resulted in delay of the onset of footpad swelling past day 5 and in elimination of the differences in the response due to the adjuvants. Immunization with carrier or hapten-carrier complexes with different epitope density in DDA and elicitation with the homologous and heterologous antigens revealed that the DH was DNP-specific. In vivo priming with DNP28-BSA in DDA and in vitro stimulation with the same antigen resulted in peak responses which were twice as high and were reached almost twice as fast as the earlier found response following immunization in FCA. The advantages of DDA as adjuvant over covalently linked fatty acid chains and over FCA are discussed.

The immune response to oxidized ferredoxin. II. Cross reactivity of cells and antisera to modified ferredoxins and the nature of the cells responding in vitro

The cross reactivity of sera from rabbits sensitized to performic acid oxidized ferredoxin (O-Fd) and of spleen cells from mice sensitized to O-Fd was analysed using several chemically modified forms of ferredoxin in the complement fixation test and the in vitro lymphocyte stimulation assay. Only O-Fd and native ferredoxin (native-Fd) gave positive responses in both assays. Dinitrophenylated-O-Fd (DNP-O-Fd) and acid precipitated ferredoxin (TCA-Fd) were able to fix complement (C') but did not simulate DNA synthesis in vitro. Ferredoxin alkylated with N-ethylmaleimioxin (CM-Fd) was unable to stimulate DNA synthesis and was marginally able to fix C'. Methylated-O-Fd (meth-O-Fd) was not recognized in either assay. The various ferredoxin preparations were tested for their ability to sensitize mice for use in the in vitro lymphocyte stimulation assay. Only O-Fd, NEM-Fd and native-Fd were capable of sensitizing lymphocytes for a proliferative response in vitro to the test antigens. This correlates with the observation that only these antigens were able to induce DNA synthesis in O-Fd-sensitized lymphocytes. The nature of the cells responding in vitro was examined by treating the cells with rabbit anti-mouse immunoglobulin and C' or rabbit anti-mouse brain associated theta and C'. The 24-hr response was found to be sensitive to both sera while the 120-hr response was sensitive only to the anti-theta sera.

The immune response to oxidized ferredoxin. I. Specificity of the response to the amino terminal determinant

Several synthetic peptide analogues of the amino terminal antigenic determinant (ala-tyr-lysile-ala-asp-ser) of oxidized ferredoxin (O-Fd) were tested for their ability to inhibit the complement fixation reaction between O-Fd and homologous rabbit antiserum, and to inhibit the migration of spleen cells from guinea-pigs immunized to O-Fd or to a conjugate of the amino terminal heptapeptide (N7) and bovine serum albumin (N7-BSA). The results of the migration inhibition assay suggest that the tetrapeptide and longer peptides of the native sequence were all recognized and stimulated the production of migration inhibition factor. Peptides modified at the aspartic residue were partially active while the serine modified peptide was not. Modification at the amino end of the heptapeptide had no effect on migration inhibition. As specificity controls, it was shown that the N7-BSA conjugate inhibited migration in O-Fd immunized animals, while O-Fd inhibited migration in N7-BSA immunized animals. The hexa-, hepta-, aspartic-deleted and serine-modified peptides were able to inhibit the complement fixation reaction with O-Fd and specific rabbit antiserum. Inhibition found with the serine-modified peptide and the lack of inhibition with the amino-modified peptide or the di-, tri-, tetra- and pentapeptides indicates the determinant recognized by the rabbit antibodies is either larger or is located nearer the middle of the heptapeptide than the determinant which induced the production of MIF.

Structure and immunogenic behaviour of methylated tobacco mosaic virus

Tobacco mosaic virus was methylated, using various concentrations of dimethylsulfate. The methylated virus sample with still intact particles was subjected to sequential analysis. The sites and the degree of methylation were determined in the tryptic peptides. Tyrosine 139 and cysteine 27 are more accessible to methylation than tyrosine 72, lysine 68 and tyrosine 2. A limited number of carboxyl groups was also methylated. The ability of methylated and original tobacco mosaic virus to initiate the formation of humoral antibodies and the capacity to induce a delayed-type hypersensitivity reaction were investigated in STU mice. Original tobacco mosaic virus could not induce a delayed-type hypersensitivity reaction but methylated tobacco mosaic virus induced a delayed-type reaction, not depending on whether the virus particles were intact or disintegrated. This phenomenon was strictly linked with the presence of methylester groups.

p-Azobenzenearsonate-L-tyrosine-mediated helper function in immune responses of guinea pigs and rats

A small bifunctional antigen (4-hydroxy-5-iodo-3-nitrophenyl)acetyl-epsilon-aminocaproyl-L-tyrosine-azobenzene-p-arsonate [NIP-cap-TYR(ABA)] was found to induce fair humoral antibody formation against NIP-cap but very little anti-ABA-TYR. This was observed in rats and guinea pigs. Prior immunization with ABA-TYR, either as such or coupled to dodecanoylated bovine serum albumin (lipid-BSA), primed rats for an enhanced anti-NIP response to NIP-cap-TYR(ABA). An attempt to encourage rats to produce anti-ABA-TYR in response to the bifunctional antigen by priming them with NIP-cap-lipid-BSA failed. Priming with ABA-TYR was dose-dependent. An injection of 1.5-15 nanomoles per rat primed for an increased production of anti-NIP while 150 nanomoles did not. Adult thymectomized x-irradiated rats had a poor anti-NIP response to the bifunctional antigen if they were reconstituted with T-enriched lymphoid cells from control mice, but a good response if reconstituted with similar cells from ABA-TYR-primed syngeneic rats.

Immunogenic properties of rat hepatoma subcellular fractions

Subcellular fractions from an aminoazo dye induced rat hepatoma (D23) were examined for their ability to evoke rejection responses in syngeneic hosts to transplanted tumour cells and to induce the production of humoral antibody. Membrane fractions isolated by zonal centrifugation and displaying an increased activity of tumour specific antigen (Price and Baldwin, 1974), as well as crude membrane fractions and purified tumour cell ghosts, all elicited tumour specific antibody demonstrable by membrane immunofluorescence staining of viable hepatoma D23 cells. Tumour cell nuclei or soluble cytoplasmic protein were, however, lacking in this capacity. Resistance to tumour cell challenge was not observed in rats treated with any of the hepatoma D23 subcellular fractions administered by various routes either alone or in admixture with bacterial adjuvants. These findings are relevant to current views that tumour immunity may be more optimally achieved by inoculation of intact (viable or attenuated) tumour cells.

The relationship of immune status to the efficacy of immunotherapy in preventing tumour recurrence in mice

The immunotherapeutic value of tumour extracts or B.C.G. in preventing either the occurrence of primary tumours or the recurrence of tumours in surgically resected animals has been examined. A transplantable methylcholanthrene induced tumour in DBA/2J mice was used. Neither tumour extract nor chemically modified extract was effective in preventing tumour growth in immunized animals, even though the mice demonstrated measurable levels of cell mediated tumour immunity at the time of tumour challenge. The frequency of tumour recurrence after resection of small tumours (about 1·0 g) was significantly lowered by treatment of the mice with a combination of B.C.G. and either modified or unmodified tumour extract. The frequency of recurrence after resection of large tumours (about 2·5 g) was not affected by any form of immunotherapy although the survival time of treated animals was significantly prolonged. The immunological status of animals with small and large tumours was examined and it was shown that mice with 1·0 g tumours have unimpaired mitogen responsiveness and measurable tumour specific immunity, whereas mice bearing large tumours (2·5 g) have a markedly impaired immune system.

Lack of a correlation between cell-mediated immunity to the carrier and the carrier-hapten helper effect

The relationship between cell-mediated immunity to the carrier and the carrier-hapten helper effect was studied in the rat by using three forms of the carrier which differed in their capacity to induce carrier-specific delayed-type hypersensitivity. The three carriers were polymerized flagellin (POL), flagellin (FIN), and acetoacetylated flagellin (AFIN), which induced FIN-specific delayed-type hypersensitivity in the order AFIN > FIN > POL. Helper cells for the anti-DNP antibody responses to a range of DNP-FIN conjugates appeared to be almost inversely related to cell-mediated immunity to the carrier, being in the order POL > FIN =/> AFIN. These differences occurred whether the carriers were injected in saline or FCA, but were less pronounced with the heavily DNP-conjugated flagellins.

A cellular basis for genetically controlled immunologic unresponsiveness in mice: tolerance induction in T-cells

H-2(q) mice (DBA/1) do not make an antibody response to a synthetic aminoacid polymer, (Glu, Ala,Tyr(10)), after an immunizing regimen that produces a good antibody response in mouse strains with other H-2 alleles. Their thymocytes, however, show evidence of recognizing this antigen since they synthesize DNA when they meet the antigen in the spleen. This recognition event does not lead to memory production, as it does in genetic responders, since the thymocytes fail to respond to a second immunization with (Glu,Ala,Tyr(10)). Nonresponder mice do make antibody to (Glu,Ala,Tyr(10)) when they are immunized with it complexed to an immunogenic carrier, but previous treatment with free polymer can temporarily abolish this response. Thus, we suggest that the basis for the unresponsiveness of these mice is that their T-cells (thymus-processed lymphocytes) have an inordinate propensity to become (or to induce other cells to become) immunologically tolerant.