The detection of protective antigen (PA) associated with spores of Bacillus anthracis and the effects of anti-PA antibodies on spore germination and macrophage interactions.

The protective antigen (PA) component of the anthrax toxins is an essential virulence factor of Bacillus anthracis and is the major protective immunogen. The kinetics of PA production during growth of B. anthracis, and the roles of anti-PA antibody in host immunity are not clearly defined. Production of PA by the vegetative organisms peaks during the shift from exponential to stationary phase of growth. Recently, PA was also found to be associated with spores. In our study, PA-specific mRNA was detected in spores by RT-PCR within 15-min of exposure to germinant. PA protein was detected by immunomagnetic electrochemiluminescence (ECL) on spores within 1 h of exposure to a germination medium and was rapidly released into the supernatant. PA was not demonstrated on ungerminated spores by RNA analysis, ECL, or spore-based anti-PA ELISA; however, it was detected on ungerminated spores by immunoelectron microscopy (immunoem). In rabbits, PA induces polyclonal antibodies (Abs) that, in addition to their anti-toxin neutralizing activities, exhibit anti-spore activities. In this study, the anti-spore effects of a human monoclonal Ab specific for PA (AVP-hPA mAb, Avanir Pharmaceuticals) were characterized. AVP-hPA mAb retarded germination in vitro, and enhanced the phagocytic and sporicidal activities of macrophages. The activities were comparable to those of the polyclonal rabbit anti-rPA Ab. Assays to detect germination inhibitory activity (GIA) in serum from vaccinated mice and guinea pigs suggested a possible role for anti-PA Abs in protection. Thus, anti-PA Ab-mediated, anti-spore activities may play a role in protection during the early stages of an anthrax infection.

Clinical efficacy of topical docosanol 10% cream for herpes simplex labialis: A multicenter, randomized, placebo-controlled trial.

BACKGROUND: Recurrent herpes simplex labialis (HSL) occurs in 20% to 40% of the US population. Although the disease is self-limiting in persons with a healthy immune response, patients seek treatment because of the discomfort and visibility of a recurrent lesion. OBJECTIVE: Our purpose was to determine whether docosanol 10% cream (docosanol) is efficacious compared with placebo for the topical treatment of episodes of acute HSL. METHODS: Two identical double-blind, placebo-controlled studies were conducted at a total of 21 sites. Otherwise healthy adults, with documented histories of HSL, were randomized to receive either docosanol or polyethylene glycol placebo and initiated therapy in the prodrome or erythema stage of an episode. Treatment was administered 5 times daily until healing occurred (ie, the crust fell off spontaneously or there was no longer evidence of an active lesion) with twice-daily visits. RESULTS: The median time to healing in the 370 docosanol-treated patients was 4.1 days, 18 hours shorter than observed in the 367 placebo-treated patients (P =.008; 95% confidence interval [CI]: 2, 22). The docosanol group also exhibited reduced times from treatment initiation to (1) cessation of pain and all other symptoms (itching, burning, and/or tingling; P =.002; 95% CI: 3, 16.5); (2) complete healing of classic lesions (P =.023; 95% CI: 1, 24.5); and (3) cessation of the ulcer or soft crust stage of classic lesions (P <.001; 95% CI: 8, 25). Aborted episodes were experienced by 40% of the docosanol recipients versus 34% of placebo recipients (P =.109; 95% CI for odds ratio: 0.95, 1.73). Adverse experiences with docosanol were mild and similar to those with placebo. CONCLUSION: Docosanol applied 5 times daily is safe and effective in the treatment of recurrent HSL. Differences in healing time compared favorably with those reported for the only treatment of HSL that has been approved by the Food and Drug Administration.

Antigen-specific IgG responses from naive human splenocytes: in vitro priming followed by antigen boost in the SCID mouse.

High titers of Ag-specific human IgG were consistently achieved in SCID mice reconstituted with human splenocytes that had been primed with Ag in vitro and then boosted with Ag after engraftment into SCID mice. Specific human IgG titers in the hu-SPL-SCID mice reached approximately 1:4 x 10(5) when the mice were immunized with a neo-antigen, whereas titers reached 1:2 x 10(6) when recall responses were induced. Booster immunizations with Ag 21 days after the initial in vivo boost further enhanced this response, and specific human IgG titers of 1:17 x 10(6) were achieved. This represented an essentially monospecific IgG population. These responses were CD4+ T cell dependent. In addition, affinity maturation of the human Ab responses was observed. Spleens of hu-SPL-SCID mice with Ag-specific titers < or = 1:1 x 10(6) were often significantly enlarged and often displayed visible tumors. Fourteen of sixteen B cell tumors removed from spleens of five such hu-SPL-SCID mice, produced Abs that were specific for the immunizing Ags. From such tumor, cloned cell lines were established. One such mAb, MLN-7 (gamma1, kappa), was raised to tetanus toxoid and had no identified cross-reactivity.

Plasma terminal complement complexes in acute poststreptococcal glomerulonephritis.

In most instances of acute poststreptococcal glomerulonephritis (APSGN), activation of the complement system occurs, as reflected by decreased levels of the complement proteins C3, C5, and properdin (P). Recent studies implicate terminal complement complexes (TCC) in the pathogenesis of glomerular injury. The fluid phase TCC, SC5b-9, reflects the formation of membrane-bound C5b-9 and has been used as a clinical marker in various diseases. Plasma concentrations of SC5b-9 were measured with an enzyme immunoassay using a monoclonal antibody to a neoantigen expressed on the SC5b-9 complex in 13 children who presented with clinical and pathologic features of APSGN. SC5b-9 was significantly elevated in all plasmas obtained within 30 days after onset of clinical glomerulonephritis. Concentrations of SC5b-9 in acute plasmas were significantly higher than those of paired convalescent samples. For individual patients, as SC5b-9 concentration returned to normal there was a coincident decrease in serum creatinine concentration and urinary protein excretion, signifying clinical improvement in glomerulonephritis. Thus, TCC generation commonly occurs in the early stages of APSGN and may be of importance in the pathogenesis of the condition.

Interleukin 2 regulates antigen-specific immunoglobulin response of naive murine B cells.

Activation of mouse B cells with lipopolysaccharide in conjunction with anti-immunoglobulin (Ig) antibodies results in interleukin 2 (IL2) receptor (IL2-R) expression and IL2 responsiveness. In most studies on the effect of IL2 on antibody production by B cells, polyclonally activated normal B cells or B cell lines established in vitro have been used as indicator cells, thus allowing no direct correlation between the experimental findings and the actual physiological mechanism of IL2 action in antigen-specific B cell response. We employed the splenic fragment culture technique, which measures antibody response on the clonal level, to analyze the effect of purified human recombinant IL2 (rIL2) on the primary antigen-specific Ig response of mouse B cells. Here we report that rIL2 increased the frequency of dinitrophenyl (DNP)-responsive splenic B cells and the amount of Ig secreted per clone. The anti-DNP antibody response was dependent upon interaction of naive B cells with carrier-primed T cells, which apparently provided the signal for IL2-R expression. Recombinant IL2 also facilitated Ig isotype switching by individual clones, suggesting a role for IL2 in activation, maturation, and differentiation of antigen-specific naive B cells in their response to T-dependent antigens.

Ba and Bb fragments of factor B activation: fragment production, biological activities, neoepitope expression and quantitation in clinical samples.

Factor B is a centrally important component of the alternative complement pathway. Alternative pathway activation results in factor B cleavage and production of the amino-terminal Ba and the carboxyl-terminal Bb fragments which have molecular weights of approximately 30,000 and 63,000 daltons, respectively. Both Ba and Bb fragments have been reported to express a variety of biological activities in vitro. Thus, binding of Ba and Bb fragments to specific B lymphocyte surface receptors modulates proliferation of prestimulated B cells. In addition, the enzymatically active Bb fragment induces activation and spreading of human and murine macrophages and monocytes as well as regulates C5a des Arg chemotactic activity. The fractional catabolic rate and metabolism of factor B in vivo is similar to that of C3, C4 and C5 complement proteins, which are among the most metabolically active plasma proteins in the circulatory system. Factor B hyperconsumption and increased catabolism, concomitant with factor B fragment production, occurs in a wide variety of diseases, including gram-negative sepsis, autoimmune diseases and burns. Measurement of alternative pathway activation in vivo has been attempted utilized a number of different techniques to quantitate factor B fragments in biological fluids. However, the recent development of enzyme immunoassays (EIA) employing monoclonal antibodies (MoAbs) reactive with factor B fragment neoepitopes provides the best approach currently available for the quantitation of factor B activation fragments. Results obtained using these new MoAb-based EIAs have indicated that factor B fragment concentrations were elevated, as compared with normal donor levels, in EDTA plasma samples obtained from patients with rheumatoid arthritis and systemic lupus erythematosus (SLE). Plasma concentrations of factor B fragments, especially Ba fragment levels, in these patients showed a positive correlation with disease activity scores. One of the highest disease activity correlations was obtained with Ba fragment measurements in SLE plasma samples. In fact, the results strongly suggested that quantitation of Ba fragment levels in SLE plasma samples more accurately reflected disease activity and was a more sensitive predictor of impending flare in these patients than any other test(s) currently available.

Association of lpr gene with graft-vs.-host disease-like syndrome.

Hemopoietic cells have been reciprocally transferred between two lines of mice (MRL lpr/lpr and MRL +/+) that are congenic, differing only at the lpr (lymphoproliferation) and possibly closely linked genes. The lpr strain develops a significantly more severe and fast-paced lupus-like syndrome than +/+ strain, along with a substantially larger lymphoid mass. The results showed that: (a) hemopoietic cells of such mice were sufficient to induce the respective disease phenotypes in lethally irradiated syngeneic recipients; (b) cells of MRL +/+ mice maturing in an MRL lpr/lpr environment essentially retained the disease-producing characteristics of the donor, i.e., they induced late-life lupus without lymphadenopathy; but (c) MRL lpr/lpr cells transferred into irradiated MRL +/+ recipients unexpectedly failed to induce the early-life severe lupus and lymphoid hyperplasia of the donor, instead they caused a severe wasting syndrome resembling, in many respects, graft-vs.-host disease (GVHD). This GVHD-like syndrome developed after transfer of MRL lpr/lpr fetal liver, bone marrow, or spleen cells, and was not abrogated by elimination of T cells from the inocula. Thymectomy of the MRL +/+ recipients retarded, but did not prevent, the wasting disease. The unidirectional nature of this disease suggests that the lpr mutation conferred either a structural or regulatory defect that interfered, blocked, or altered the expression or structure of certain lymphocyte antigen(s). As a result, the MRL +/+ cells that did express this antigen(s) were recognized as foreign, and stimulated a graft-vs.-host reaction. These findings may allow definition of a new kind of rejection phenomenon caused by non-H-2 products, and may extend our understanding of the means by which the lpr gene adversely affects lymphocyte regulation and homeostasis.

Tolerance and B cell repertoire establishment.

We have probed the mechanism by which immature B cells are uniquely susceptible to antigen-induced inactivation. Our studies have demonstrated that this tolerance trigger is an active process that requires both energy metabolism and the biosynthesis of various macromolecules, including protein, RNA, and DNA. However, the tolerance trigger is resistant to inhibitors of patching and capping, as well as an inhibitor of mitosis. The tolerance trigger requires a high-affinity interaction between a multivalent antigen and the cells' Ig receptor, but apparently does not require interactions with other cell surface molecules, or interactions with T cells or macrophages. Our efforts to demonstrate the physiological applicability of this tolerance trigger have concentrated on an attempt to demonstrate potentially self-reactive cells within the immature bone marrow population that do not appear in the mature splenic B cell population. To date we have identified prereceptor B cells of several specificities whose frequency is much lower in the spleen and whose elimination appears to involve tolerance rather than antiidiotypic regulation. However, the demonstration that such cells are eliminated by contact with self-antigens has not as yet been accomplished.

The idiotypic characterization of the immune response to a defined epitope of a protein antigen and the specific in vivo suppression of the immune response to this epitope by anti-idiotypic antibodies.

C10, a monoclonal antibody of C3H.SW (CSW) origin, binds a decapeptide epitope of the tobacco mosaic virus protein (TMVP) representing residues 103-112 of the protein. In vivo administration of syngeneic anti-idiotypic antibodies to C10 (anti-C10) prior to immunization with TMVP suppressed the expression of antibodies to this decapeptide determinant in CSW mice without a significant reduction of the total anti-TMVP titer. The suppression could not be overcome with repeated challenges by antigen even 6 months after administration of anti-C10. Analysis of anti-C10 showed that it contains antibodies to at least two idiotopes found on C10. One of these idiotopes, C10-Idm, is found on a very small fraction of CSW anti-TMVP antibodies capable of binding the decapeptide epitope. The other idiotope, C10-IdX, is found on most of the anti-TMVP antibodies which bind the decapeptide determinant. With synthetic analogues of the decapeptide determinant, a correlation was established between the presence of the C10-IdX and the fine specificity of the decapeptide-binding antibodies. The studies reported herein demonstrate that anti-idiotypic antibodies are potent modulators of the immune response and that the C10-IdX is important in the determination of the fine specificity of antibodies to this decapeptide epitope of TMVP.

Analysis of an evolutionarily conserved antigenic site on mammalian cytochrome c using synthetic peptides.

Two synthetic peptides inclusive of the NH2-terminal N-acetyl-Gly-Asp-Val-Glu tetrapeptide of mammalian cytochrome c (cyt c) were used in this study to address the question of whether mammals can respond immunologically to an evolutionarily conserved region of a protein. These peptides were assessed for their capacity (i) to act as immunogens for the production of anti-self cyt c antisera and (ii) to bind rabbit anti-rodent cyt c antibody. The findings from these studies indicate the existence of an immunogenic determinant in an evolutionarily conserved region of cyt c that contains residues 1-4. This determinant can induce anti-self cyt c antibodies whether presented as a peptide on a carrier protein or in the context of the intact molecule as polymerized mammalian cyt c.

The antibody response to a single antigenic determinant of the tobacco mosaic virus protein: analysis using monoclonal antibodies, mutant proteins and synthetic peptides.

Three hybridomas were selected which secreted monoclonal antibodies specific to a decapeptide determinant representing residues 103-112 of the tobacco mosaic virus protein ( TMVP ). A series of proteins from several strains of TMV which differ in the amino acid sequence in this region of the protein were used as probes for specificity analysis. The fine-specificity analysis was extended by assessing the binding of the antibodies with a panel of synthetic peptide analogues of the native decapeptide with amino acid substitutions at different locations. The binding of each synthetic peptide with each of the monoclonal antibodies was determined by the ability of the radiolabeled peptide to bind with the antibody. The binding of the decapeptide with antibodies was determined by equilibrium dialysis; the relative binding affinity of each peptide of the panel was determined by the capacity of the peptide to inhibit the binding between the antibody and the radiolabeled native decapeptide. The results demonstrated that a panel of synthetic peptide analogues constitutes a powerful tool for discerning the fine specificity of antibodies directed to a given determinant of a protein antigen. The data indicated that, although all of the antibodies recognized the same nominal decapeptide determinant, their binding with the different mutant proteins or with the synthetic peptides of the panel differed greatly, indicating dramatic differences in their fine specificity. The existence of such differences should be taken into consideration when assessing residues of a protein antigen that are involved in antibody binding. The differences which were found in monoclonal antibodies produced following immunization with the whole TMVP reflect differences which occur in heterogeneous serum antibody populations and point out the complexity of antigenic recognition even of as small an epitope as a decapeptide.

Cellular aspects of genetic defects in Con A mitogenesis.

The cellular basis for genetically determined low Con A stimulation of peripheral blood lymphocytes from two inbred lines of chickens was investigated. A simple shift in the dose-response curve was not responsible for the low stimulation. In addition, proliferation was neither accelerated nor delayed. The results of mitogen and cell mixing experiments showed that the low Con A stimulation in both strains was not mediated by suppression. Furthermore, cocultures of lymphocytes from the two low Con A responder lines complemented to give high Con A stimulation. These results indicate that at least two distinct genes, apparently expressed in different cell populations, can confer low Con A responses in chickens.

The antibody response to a single antigenic determinant of the tobacco mosaic virus protein (TMVP): effects of allotype-linked genes and restricted heterogeneity of the response.

The antibody response to a decapeptide antigenic determinant representing residues 103 to 112 of the tobacco mosaic virus protein (TMVP) was studied with the synthetic decapeptide and a panel of its synthetic analogues. The anti-decapeptide response was found to be of restricted heterogeneity and was regulated by heavy chain allotype-linked (V region) genes on at least two levels. One level was whether or not a significant antibody response was made to the decapeptide determinant. Thus, strains with the Igh haplotypes j, o, e, and n were high responders, whereas strains with haplotype Ighb were low responders. The second level of V region gene control was with regard to the fine specificity of the anti-decapeptide antibodies produced. Using the peptide panel to analyze fine specificity, we define two new V region genetic markers, VH-TMVPj and VH-TMVPe.

Functional heterogeneity of memory B lymphocytes: in vivo analysis of TD-primed B cells responsive to secondary stimulation with TD and TI antigens.

The functional heterogeneity of memory B cells induced by a single determinant, consisting of a decapeptide representing amino acid residues 103-112 of tobacco mosaic virus protein (TMVP), was analyzed. Decapeptide specific antibodies were elicited in mice adoptively transferred with TMVP-immune spleen cells when challenged with TMVP, decapeptide conjugated to succinylated human gamma-globulin (SHGG), or decapeptide conjugated to Brucella abortus (BA). Whereas secondary stimulation by either TMVP or decapeptide-SHGG was dependent on appropriately primed T cells, stimulation by decapeptide-BA was independent of conventional T cell help. Furthermore, memory B cells responsive to TMVP (TD), decapeptide-SHGG (TD), or decapeptide-BA (TI. 1 prototype) were shown to consist of overlapping populations because adoptive recipients of TMVP-primed cells challenged simultaneously with TD and TI decapeptide antigens did not result in a higher antibody response than that elicited by one of the TD antigens injected alone. However, decapeptide-BA consistently induced a smaller antidecapeptide response than either TMVP or decapeptide-SHGG. This suggested that only a fraction of the memory B cell population which was activated by the original priming antigen (thymus-dependent) was also responsive to secondary in vivo stimulation by the priming hapten conjugated to Brucella abortus. Detailed analyses of the antibodies induced in the recipients of TMVP-immune spleen cells after secondary challenge with either TMVP, decapeptide-SHGG, or decapeptide-BA failed to distinguish between the responsive memory B cells; the antidecapeptide antibodies induced by all three immunogens shared the same fine specificities and immunoglobulin isotype composition. These data are viewed as further evidence that subsets of TD-primed B cells, which may display differential sensitivity to cross-stimulation with TD and TI forms of the antigen, represent distinct stages of memory B cell maturation within a common B cell lineage. In support of this conclusion, we establish a developmental relationship between TI and/or TD responsive decapeptide memory B cell in the following communication.

Two stages of b cell memory development expressing differential sensitivity to stimulation with thymus-dependent and thymus-independent antigenic forms.

We have shown that spleen cells specifically primed to the decapeptide determinant (a.a. 103-112) of the thymus-dependent (TD) antigen, tobacco mosaic virus protein (TMVP), can be secondarily stimulated to antibody synthesis by either TD or TI forms of the decapeptide. Further, TD- and TI-responsive memory B cells consisted of overlapping populations which were indistinguishable by the specificity and isotype composition of the antibodies which they synthesized. In the present study, two functionally distinct but developmentally related memory B cell subsets were identified by their differential sensitivity to repeated in vivo stimulation with various combinations of TD and TI decapeptide antigens. One subset of memory B cells responded only to TMVP or decapeptide conjugated to succinylated human gamma-globulin (SHGG) with a strict requirement for carrier-primed theta-positive cells. Secondary challenge with these two TD antigens elicited antidecapeptide antibodies and specific memory regeneration. This TD-responsive memory B cell subset contained the precursors of a second memory B cell subset which was activated by decapeptide-Brucella abortus (TI.1 prototype), as well as by TMVP or decapeptide-SHGG. Stimulation of the second memory B cell subpopulation by decapeptide-BA (previously shown not to be dependent on conventional T cell help) was typified by differentiation into antibody-forming cells without significant memory regeneration.

Genetic control of T-lymphocyte mitogenesis in chickens.

The in vitro mitogenic response to PHA and Con A was determined in three inbred lines of chickens. Lymphocytes from one line consistently showed a greater stimulation by PHA than the other two lines. Analysis of F1 crosses and backcrosses indicated that this quantitative difference was controlled by more than one gene. More substantial differences in Con-A stimulation were also observed between the three lines, and the data indicated that separate genetic systems were controlling the variation in PHA and Con-A stimulation. Analysis of F1 crosses, backcrosses and assortative matings between backcrosses revealed that the variation in Con-A stimulation was controlled by at least two major genes, one of which may be linked to the major histocompatibility complex. Surprisingly, one line appeared to be segregating for Con-A stimulation in spite of an inbreeding coefficient greater than 0.98.

Differential activation of primary and memory "B" lymphocytes.

Immunization of certain strains of mice with the tobacco mosaic virus protein (TMVP) elicits antibodies capable of binding with a decapeptide representing residues 103-112 of TMVP. However, immunization of mice with decapeptide conjugated to a variety of carriers failed to elicit antibodies to the decapeptide in spite of the fact that antibodies were induced to the carriers or to nonrelated peptides similarily conjugated to the carriers. In contrast to the conjugates inability to induce a primary anti-decapeptide response, the conjugates were able to elicit a secondary anti-decapeptide response. Thus, when irradiated mice were transplanted with syngeneic TMVP-primed B cells and carrier-primed T cells, secondary challenge with the decapeptide on the carrier elicited an excellent secondary anti-decapeptide response. Furthermore, the titer and specificity of the antibodies so induced were the same as that induced by secondary challenge with TMVP. These results suggest a difference between primary and memory B cells in their requirements for activation.