Antibody Responses of Cattle Immunized with the Tf190 Adhesin of Tritrichomonas foetus

The antibody response patterns of cattle after subcutaneous and intranasal immunizations with adhesin Tf190 of Tritrichomonas foetus were investigated. Reactions of antibody from cattle parenterally immunized with Tf190 revealed antigen specificity and Tf190 sensitization in the majority of the animals, as determined by Western blotting. The results also demonstrated strong preimmune immunoglobulin G2 (IgG2) binding to T. foetus antigens not seen in IgG1 profiles. Subcutaneous injections of Tf190 resulted in significant (P < 0.05) increases in serum IgG1 and IgG2 titers over time, as determined by parasite specific enzyme-linked immunosorbent assay. Immune sera also significantly inhibited parasite adhesion to mammalian cell lines compared to the level of inhibition obtained with preimmune sera (P < 0.05). Intranasal immunization with Tf190 failed to produce measurable parasite-specific antibody in serum; however, this immunization route did result in significant (P < 0.05) increases in parasite-specific IgA titers in cervical mucus secretions from immunized animals that were more resistant to intravaginal challenge with T. foetus than controls. These results suggest that systemic immunization with Tf190 results in serum antibody production and antiparasitic adhesin antibodies. Additionally, the results of challenge experiments with intranasally immunized animals suggests that Tf190 primes protective immune responses that lead to lower rates of infection among these animals.     

Immunization of virgin cows with surface antigen TF1.17 of Tritrichomonas foetus.

Protection by surface antigen TF1.17 of Tritrichomonas foetus was investigated because it reacted with a monoclonal antibody which immobilized and mediated complement killing of the organism and prevented adherence to vaginal epithelial cells. This monoclonal antibody was used to demonstrate conservation of the antigen in most strains and to immunoaffinity purify the 50- to 70-kDa glycoprotein antigen. In preparation for immunization studies, the appropriate challenge dose of parasites was determined by intravaginal inoculation of 23 virgin cows (heifers) with 10(2), 10(4), or 10(6) live organisms at the time of estrus. More animals became infected and vaginal infection was maintained at a higher rate (P < 0.005) over 10 weeks for the group that received 10(6) organisms than in the other two groups. Therefore, this dose was used for challenge of immunized animals. Animals immunized with immunoaffinity-purified TF1.17 antigen in incomplete Freund's adjuvant or incomplete Freund's adjuvant plus dextran sulfate cleared the infection more quickly than adjuvant controls (P < 0.005). Isotype-specific enzyme-linked immunosorbent assay with T. foetus antigen showed that serum immunoglobulin G1 (IgG1) and IgG2 antibody responses as well as cervicovaginal mucus IgG1 and IgA antibodies peaked at about the time of clearance of infection in vaccinated animals. Controls developed later cervicovaginal mucus IgA antibody responses as would be expected in a primary local immune response to infection. These results indicate that vaccination with this immunoaffinity-purified surface antigen of T. foetus enhances antibody responses as well as clearance of the parasite from the female reproductive tract.     

Immune Response in the Bovine Mammary Gland After Intestinal, Local, and Systemic Immunization

The immune response in mammary glands of cattle was measured after intestinal, local, and systemic immunization with T4 bacteriophage. Nonlactating pregnant cows were immunized by infusions into the intestine or mammary gland and by subcutaneous injections in the region of the prescapular or external inguinal lymph nodes. Titers of antibodies of different isotypes were measured in serum and in lacteal secretions by enzyme-linked immunosorbent assay, and numbers of cells producing antibodies of each isotype were determined in lacteal secretions by the Jerne plaque assay. Substantial increases in immunoglobulin G subclass 1 (IgG1) and IgG2 antibody titers were detected in serum and lacteal secretions of animals immunized through an intestinal fistula. IgM and IgA antibody responses were low or undetectable. Low numbers of IgA and IgG1 plaque-forming cells were occasionally detected. It is proposed on the basis of these data that migration of antigen-stimulated IgG lymphoblasts, and perhaps of antigen, to spleen and peripheral lymph nodes may be dominant events after intestinal immunization of ruminants. This is consistent with the predominance of serum-derived IgG antibodies in colostrum and milk. Intramammary infusion of antigen gave rise to increases in antibody titers in all classes which were greater not only in lacteal secretions but also in blood serum than with either systemic route used. There was clear evidence from relative antibody titers for local synthesis of antibodies, principally IgA and IgG1, in the immunized glands. Comparison of IgA titers in secretions from the immunized glands with those in serum also suggested that locally synthesized IgA antibodies may have contributed in some measure to serum titers. Local synthesis in both immunized and nonimmunized glands was also reflected by the presence of increased numbers of IgA and IgG1 plaque-forming cells. It is hypothesized that antibody-forming cells responsible for local synthesis originated in lymphoid tissue within the mammary gland or from peripheral lymph nodes, depending upon the route of immunization.     

Experimental immunization with Pseudomonas aeruginosa alginate induces IgA and IgG antibody responses.

We tried experimentally to induce a specific antibody response against Pseudomonas aeruginosa locally in the airways and systemically in rats by three different routes of immunization; intragastric feeding, intratracheal inoculation or subcutaneous vaccination. Three groups of rats were immunized with live mucoid P. aeruginosa PAO 579 by intragastric feeding or with killed PAO 579 intratracheally or subcutaneously. Three other groups were immunized with purified P. aeruginosa alginate either by intragastric feeding, intratracheally or subcutaneously. At weekly intervals for four weeks animals were sacrificed and serum and bronchial fluid were obtained. The specific IgA and IgG antibody response in lavage fluid and serum was measured. Only traces of antibodies could be detected in the bronchial lavage fluids. Anti-alginate IgA and IgG antibodies developed in all rats immunized with alginate but no antibodies against other P. aeruginosa antigens were detected. The highest IgA and IgG titer against alginate was induced by the subcutaneous immunization. IgA and IgG antibodies against other P. aeruginosa antigens developed in rats immunized with liver and sonicated bacteria. The highest IgA and IgG titers were obtained after intratracheal and subcutaneous immunization with sonicated bacteria. The present work has shown that IgA and IgG antibodies develop with high specificity after immunization. The different titers obtained do not necessarily reflect different degrees of protection.     

Protection against malaria in Aotus monkeys immunized with a recombinant blood-stage antigen fused to a universal T-cell epitope: correlation of serum gamma interferon levels with protection.

The major surface antigen p190 of the human malaria parasite Plasmodium falciparum contains nonpolymorphic, immunogenic stretches of amino acids which are attractive components for a subunit vaccine against malaria. One such polypeptide, termed 190L, is contained in the 80-kDa processing product of p190, which constitutes the major coat component of mature merozoites. We report here that immunization of Aotus monkeys with 190L gives only poor protection against P. falciparum challenge. However, addition by genetic engineering of a universal T-cell epitope (CS.T3) to 190L improved immunity, and as a result three of four monkeys were protected following challenge infection with blood-stage parasites. Neither antibody against the immunizing antigens or against blood-stage parasites nor the capacity of the monkeys' sera to inhibit in vitro parasite invasion correlated with protection. However, in contrast to sera from nonprotected monkeys, sera from protected animals contained elevated levels of gamma interferon. These results suggest that gamma interferon is directly or indirectly involved in the process of asexual parasite control in vivo.     

西尼罗病毒与乙脑病毒免疫交叉反应的实验研究

为明确西尼罗病毒(WNV)与乙型脑炎病毒(JEV)的免疫交叉反应,本文分别用WNV全抗原与JE减毒活疫苗免疫小鼠,采用间接免疫荧光试验检测血清中2种病毒IgG抗体水平及其交叉反应情况。结果表明:WNV组在第4次免疫后的14天和35天出现2个高峰,平均效价分别为6088和4305;JEV组第4次免疫后,小鼠血清JEV抗体呈现缓慢上升的趋势。无论是在WNV全抗原免疫小鼠血清中还是在JE减毒活疫苗免疫小鼠血清中,同一血清对WNV抗原和JEV抗原均有反应,且抗体效价差异有显著性。在抗WNV抗体阳性血清中,两者交叉反应相对较强,在抗JEV抗体阳性血清中,两者交叉反应较弱。WNV与JEV存在一定交叉反应,但是否有交叉保护作用则需要中和试验等进一步证实。     

An anti-idiotype antibody which mimics the inner-core region of lipopolysaccharide protects mice against a lethal challenge with endotoxin.

Recently, we described the generation and characterization of an Armenian hamster Ab2 beta anti-idiotype monoclonal antibody (MAb4G2) specific for the binding site of a mouse monoclonal antibody, MAbY1-4A6, directed against the conserved 2-keto-3-deoxyoctulosonate (Kdo)-containing inner-core region of lipopolysaccharide (LPS) (S. K. Field, M. Pollack, and D. C. Morrison, Microb. Pathog. 15:103-120, 1993). In that study, mice and hamster immunized with MAb4G2 generated serum immunoglobulin G and M (IgG and IgM) antibodies which cross-react with Salmonella minnesota R595-chemotype rough mutant LPS (Re-LPS). In this report, we demonstrate that in C3Heb/FeJ mice, MAb4G2 elicits an immune response which is characterized by specific binding of antibody to Re-LPS, as assessed by enzyme-linked immunosorbent assay. The practical use of MAb4G2 as a potentially effective therapeutic agent against gram-negative bacterial sepsis is suggested by the demonstration that immunization of these mice with MAb4G2 results in significant protection of D-galactosamine-sensitized animals against an otherwise lethal dose of Re-LPS. Assessment of the temporal changes in Re-LPS-specific serum antibody titers from mice immunized with MAb4G2 or Re-LPS over a 40-day period indicates that immunization with Re-LPS elicits significantly higher titers of serum IgM antibodies compared with those in animals immunized with MAb4G2. Conversely, two immunizations with MAb4G2 result in an up to 10-fold increase in anti-Re-LPS-specific IgG serum antibody titers relative to those obtained in mice immunized with Re-LPS. Nineteen days after the secondary boost with MAb4G2, anti-Re-LPS-specific IgG serum antibody titers were significantly higher (three- to fourfold) compared with those in Re-LPS-treated animals. Initial immunization with the anti-idiotype antibody primes animals for enhanced secondary responses to Re-LPS, as assessed by the titers of anti-Re-LPS-specific IgG profiles. These data suggest the potential utility of MAb4G2 as a candidate vaccine against the lethal properties of gram-negative bacterial LPS.     

Antibody response in the parotid fluid and serum of Irus monkeys (Macaca fascicularis) after local immunization with Streptococcus mutans.

The antibody response of Macaca fascicularis in parotid saliva and serum to local immunization by two routes with Streptococcus mutans was studied and compared over 1 year. Antibodies were titrated and classified by indirect immunofluorescent staining using specific antiglobulin conjugates. Antiglucosyltransferase activity was assayed by an enzyme inhibition test. Animals were immunized first by injecting formalin-killed bacterial cells and cell products subcutaneously into the vicinity of the four major salivary glands. The monkeys were next immunized by retrograde instillation of antigen into the parotid duct. Extensive subcutaneous local immunization gave a serum response only. After parotid duct immunization, high titers of immunoglobulin A (IgA) antibody, along with traces of immunoglobulin G (IgG) immunoglobulin M (IgM) antibody, appeared in the parotid saliva, and in the serum high titers of IgG antibody were present along with lower titers of IgA and IgM. IgA antibodies in parotid fluid were shown by double immunofluorescent staining to be associated with antigenic determinants which cross-reacted with an antiserum directed to human secretory component. Titers in parotid fluids and sera fell sharply when immunization was stopped. This response pattern was reproducible. High concentrations of antibody capable of inhibiting glucosyltransferase prepared from S. mutans were found in the sera, but relatively little was detected in the parotid fluids. Extensive immunization via the parotid duct resulted in transient functional impairment of the gland, as evidenced by diminished salivary flow rates. We conclude that parotid ductal immunization can be an effective method for stimulating a salivary secretory IgA antibacterial antibody response.     

Redirecting the humoral immune response against Streptococcus mutans antigen P1 with monoclonal antibodies

The adhesin P1 of Streptococcus mutans has been studied as an anticaries vaccine antigen. An anti-P1 monoclonal antibody (MAb) bound to S. mutans prior to mucosal immunization of mice was shown previously to alter the amount, specificity, isotype, and biological activity of anti-P1 antibodies. The present study was undertaken to screen this and four additional anti-P1 MAbs for immunomodulatory activity when complexed with S. mutans and administered by a systemic route and to evaluate sera from immunized mice for the ability to inhibit adherence of S. mutans to immobilized human salivary agglutinin. All five MAbs tested influenced murine anti-P1 serum antibody responses in terms of subclass distribution and/or specificity. The effects varied depending on which MAb was used and its coating concentration. Two MAbs promoted a more effective, and two others a less effective, adherence inhibition response. An inverse relationship was observed between the ability of the MAbs themselves to inhibit adherence and the ability of antibodies elicited following immunization with immune complexes to inhibit adherence. Statistically significant correlations were demonstrated between the levels of anti-P1 serum immunoglobulin G2a (IgG2a) and IgG2b, but not of IgG1 or IgG3, and the ability of sera from immunized animals to inhibit bacterial adherence. These results indicate that multiple anti-P1 MAbs can mediate changes in the immune response and that certain alterations are potentially more biologically relevant than others. Immunomodulation by anti-P1 MAbs represents a useful strategy to improve the beneficial immune response against S. mutans.     

柯萨奇病毒B3 VP1蛋白、rAd/VP1和pcDNA3/VP1的免疫效果比较

目的 观察柯萨奇病毒B3(Coxsackievirus B3,CVB3)衣壳蛋白VP1、表达VP1蛋白的重组腺病毒rAd/VP1和重组质粒pcDNA3/VP1的免疫效果.方法 用原核细胞表达VP1蛋白并纯化、扩增重组腺病毒rAd/VP1,扩增并提取真核表达质粒pcDNA3/VP1.BALB/c小鼠随机分为4组,每组18只,分别在股四头肌注射VP1蛋白、rAd/VP1、pcDNA3/VP1和PBS.VP1蛋白组和pcDNA3/VP1组免疫3次,间隔3周;rAd/VP1组免疫2次,间隔2周.VP1蛋白、pcDNA3/VP1和rAd/VP1每次每只注射剂量分别为50μg、100μg和1.2×107PFU.用ELISA法和微量中和试验法检测各次免疫后血清CVB3特异性IgG抗体和中和抗体滴度;末次免疫后3周,CCK-8法检测脾脏淋巴细胞的CTL杀伤活性;用致死量CVB3攻击小鼠后,检测血中病毒滴度并观察动物的存活情况.结果 VP1蛋白组血清特异性IgG抗体和中和抗体滴度明显高于其他实验组(P＜0.05),而脾脏淋巴细胞CTL杀伤活性低于rAd/VP1组(P＜0.05);致死量病毒攻击后,VP1蛋白组血中病毒滴度低于pcDNA3/VP1和rAd/VP1组(P＜0.05),生存率明显高于这两组(P＜0.05).结论 VP1蛋白疫苗能诱导较高水平的体液免疫应答,对动物有明显的免疫保护作用,免疫效果优于质粒pcDNA3/VP1和重组腺病毒rAd/VP1.

Abstract：

Objective To compare the immune effects of Coxsackievirus B3 (CVB3) capsid protein VP1 expressed bacterially, recombinant adenovirus rAd/VP1 and recombinant plasmid pcDNA3/VP1which express VP1 protein in mice. Methods After expressed in prokaryotic cells, VP1 protein was purified. Recombinant adenovirus rAd/VP1 and recombinant plasmid pcDNA3/VP1 were amplified and extracted. Six to 8-week-old, male BALB/c mice were divided into four groups randomly. Each group contained 18 mice. The mice of pcDNA3/VP1 group or VP1 protein group were immunized intramuscularly with three injections at three weeks apart, of recombinant plasmid pcDNA3/VP1 at a dose of 100 μg/mouse or recombinant protein VP1 at a dose of 50 μg/mouse. The mice of rAd/VP1 group were immunized intramuscularly twice at two weeks interval with rAd/VP1 at a dose of 1.2 × 107 PFU. The control group was mock-immunized with 100 μl of PBS intramuscularly. Mice were bled from the retroorbital sinus plexus every two weeks after each immunization. ELISA and micro-neutralization test were used to detect levels of CVB3-specific IgG antibody and neutralizing antibody titers in the sera of immunized mice. Three weeks after the last immunization, the cytotoxic T lymphocyte(CTL) killing activity of spleen lymphocytes was detected with CCK-8 assay. Subsequently, virus titers in the sera of immunized mice were determined by the 50% cell culture infective dose( CCID50 ) assay on HeLa cell monolayers and percentage of animals surviving were observed after lethal CVB3 attack over a period of 21 days. Results The titers of specific IgG antibody and neutralizing antibody in sera of VP1 protein immunized mice were higher than other groups( P ＜0.05 ). While CTL killing activity of spleen lymphocytes of VP1 protein immunized mice was lower than mice in rAd/VP1 group( P ＜0. 05). Virus titers in sera of VP1 protein immunized mice were lower than the mice in pcDNA3/VP1 or rAd/VP1 groups ( P ＜ 0.05 ), while survival rate was significantly higher than these two groups ( P ＜ 0.05 ).Conclusion VP1 protein induced higher level of humoral immune response and acquired obvious immune protection effects in mice. The immunizing potency of VP1 protein vaccine surpassed plasmid pcDNA3/VP1or recombinant adenovirus rAd/VP1. It appeared to be a promising candidate among the three different vaccines.     

Killing of Brucella abortus by bovine serum

Studies of the serum bactericidal system in bovine brucellosis were undertaken to investigate the role of the humoral immune response in protection of cattle against the facultative intracellular parasite Brucella abortus. Fresh sera from normal control cattle, infected cattle, and cattle immunized with B. abortus cell envelopes were collected before treatment and during the course of immunization or infection. Normal fresh bovine serum or fresh agammaglobulinemic serum from colostrum-deprived calves was effective in killing smooth virulent B. abortus 2308, but rough strains RB51 (a rough mutant of strain 2308) and 45/20 were much more sensitive to serum. The difference in susceptibility to serum was shown to be correlated with differences in lipopolysaccharide chemotype, with the more resistant strain 2308 having O polysaccharide and the more susceptible strains 45/20 and RB51 lacking O side chains. By treatment of fresh serum with MgCl2 and EGTA [ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid] killing was shown to occur via the classical pathway of complement activation. When antibody to B. abortus was present, killing of strain RB51 increased but killing of smooth strain 2308 decreased. The earliest antibody response in serum from infected animals did not interfere with killing. When affinity-purified bovine immunoglobulins specific for B. abortus smooth lipopolysaccharide were added to fresh normal bovine serum, immunoglobulin G1 (IgG1) and IgG2 isotypes blocked killing but IgM and IgA isotypes did not. Thus, it appears that serum from previously unexposed animals or animals early during infection can kill smooth B. abortus, an appropriate defense mechanism before the organism becomes intracellular. At later stages of infection, blocking antibodies predominate.     

Parasite strain specificity of precursor cytotoxic T cells in individual animals correlates with cross-protection in cattle challenged with Theileria parva.

Class I major histocompatibility complex-restricted parasite-specific cytotoxic T lymphocytes (CTL) are known to be a major component of the bovine immune response to the protozoan parasite Theileria parva, but formal proof for their role in protection of cattle against infection with T. parva has been lacking. Animals immunized with one stock of T. parva show variations in the degree of protection against heterologous challenge and also in the parasite strain specificity of their CTL responses. The present study investigated the relationship of strain specificity of CTL responses and cross-protection in an effort to verify the role of CTL in protection. The parasite strain specificity of the CTL responses generated in 23 cattle immunized with either of two immunologically distinct parasite populations was examined, and the susceptibility of individual cattle to challenge with the heterologous parasite population was determined. The frequency of stock-specific or cross-reactive CTL precursor cells (CTLp) in individual animals was measured by a limiting-dilution microassay. A proportion of animals immunized with either parasite exhibited cross-reactive CTLp, whereas CTLp detected in the remaining animals were specific for the homologous parasite. On challenge with the heterologous stock, those animals with cross-reactive CTLp were solidly protected while those with strain-specific CTLp showed moderate to severe reactions, although many of them recovered. The finding of a close association between strain specificity of the CTL response and protection against challenge provides strong evidence that CTL are important in mediating immunity.     

Intranasal Immunization with Pneumococcal Polysaccharide Conjugate Vaccines Protects Mice against Invasive Pneumococcal Infections

Host defenses against Streptococcus pneumoniae depend largely on opsonophagocytosis mediated by antibodies and complement. Since pneumococcus is a respiratory pathogen, mucosal immune responses may play a significant role in the defense against pneumococcal infections. Thus, mucosal vaccination may be an alternative approach to current immunization strategies, but effective adjuvants are required. Protein antigens induce significant mucosal immunoglobulin A (IgA) and systemic IgG responses when administered intranasally (i. n.) with the glyceride-polysorbate based adjuvant RhinoVax (RV) both in experimental animals and humans. The immunogenicity and efficacy of pneumococcal polysaccharide conjugate vaccines (PNC) of serotypes 1 and 3 was studied in mice after i.n. immunization with RV. Antibodies were measured in serum (IgM, IgG, and IgA) and saliva (IgA) and compared to antibody titers induced by parenteral immunization. The PNCs induced significant systemic IgG and IgA antibodies after i.n. immunization only when given with RV and, for serotype 1, serum IgG titers were comparable to titers induced by subcutaneous immunization. In addition, i.n. immunization with PNC-1 in RV elicited detectable mucosal IgA. These results demonstrate that RV is a potent mucosal adjuvant for polysaccharides conjugated to proteins. A majority of the PNC-1-immunized mice were protected against both bacteremia and pneumonia after i.n. challenge with a lethal dose of serotype 1 pneumococci, and protection correlated significantly with the serum IgG titers. Similarly, the survival of mice immunized i.n. with PNC-3 in RV was significantly prolonged. These results indicate that mucosal vaccination with PNC and adjuvants may be an alternative strategy for prevention against pneumococcal infections.     

Serum antibodies to Porphyromonas gingivalis block the prostaglandin E2 response to lipopolysaccharide by mononuclear cells.

The ability of rabbit and monkey immune sera to neutralize prostaglandin E2 (PGE2) production by human monocytes stimulated with lipopolysaccharide (LPS) was examined. CD14-dependent LPS activation of PGE2 was examined under assay conditions which allowed the comparison of preimmune and immune sera. Serum obtained from rabbits immunized with formalin-fixed Porphyromonas gingivalis cells dramatically reduced the amount of PGE2 produced in response to LPS obtained from three different strains of P. gingivalis but not that from Escherichia coli or Bacteroides fragilis. In addition, a significant reduction in the mean PGE2 level was observed in the presence of sera from immunized but not control monkeys employed in a vaccine trial. Immune serum samples from five of nine immunized monkeys were able to reduce LPS-induced production of PGE2 by greater than 50% compared to that in the corresponding preimmune sera. Immune monkey serum, similar to immune rabbit serum, blocked PGE2 production in response to P. gingivalis LPS but not E. coli LPS. These data demonstrate that immunization with P. gingivalis whole cells can elicit an antibody response that is able to block the PGE2 response to LPS. Neutralization of LPS-mediated inflammatory mediator production may account in part for the observed suppression of alveolar bone loss in immunized monkeys.     

Biolistic-mediated gene transfer using the bovine herpesvirus-1 glycoprotein D is an effective delivery system to induce neutralizing antibodies in its natural host

A genetic vaccine consisting of the bovine herpesvirus-1 (BHV-1) glycoprotein D (gD) gene was constructed and administered to cattle using the biolistic (gene-gun) process. Results were compared to standard intramuscular injection of an inactivated whole BHV-1 commercial vaccine. Cattle genetically immunized by the gene-gun-delivered gD subunit vaccine developed high titers of IgG antibodies specific to gD demonstrating that this immunization method is a potent humoral response inducer. Further, gene-gun vaccinated cattle produced high neutralizing antibody titers to BHV-1 similar to levels induced in the commercial vaccine immunized animals. Additionally, cellular immunity was measured by an increased level of IFN-gamma mRNA detected in PBMC of cattle immunized with the gD gene or with the commercial vaccine, whereas augmented levels of IL-4 were not detected following vaccination. Because of its simplicity and effectiveness in inducing an immune response in cattle similar to a commercial vaccine, gene-gun delivery of a subunit BHV-1 gD vaccine would be a viable alternative to current immunization protocols.     

Blocking ELISA for distinguishing infectious bovine rhinotracheitis virus (IBRV)-infected animals from those vaccinated with a gene-deleted marker vaccine.

A sensitive and specific blocking enzyme-linked immunosorbent assay (ELISA) was developed to distinguish infectious bovine rhinotracheitis virus (IBRV)-infected animals from those immunized with a glycoprotein gIII deletion mutant, IBRV(NG)dltkdlgIII. For this ELISA, undiluted test sera are used to block the binding of an anti-IBRV gIII monoclonal antibody (mAbgIII)-horseradish peroxidase (HRPO) conjugate to gIII antigen. TMB substrate is used for color development. Negative S/N values (defined as the absorbance at 650 nm of test sera/absorbance at 650 nm of negative control sera) of > 0.80 were obtained with immune sera from gnotobiotic cattle immunized with several bovine viruses, with bovine antisera to bovine herpesvirus-2, and vesicular stomatitis virus, with porcine antisera to pseudorabies virus and parvovirus, and with normal sera from heterologous species. Negative S/N values were also obtained with sera from rabbits twice vaccinated with IBRV(NG)dltkdlgIII. However, the S/N values became positive (S/N < 0.8) 10 to 17 days after the rabbits were challenge exposed to virulent IBRV(Cooper). Most of 116 sera (84%) from feedlot cattle with virus neutralization (VN) titers of < 1:2 or < 1:4 had negative S/N values > 0.8, but 18 sera with negative VN titers had positive S/N values, consistent with observations indicating that an IBRV outbreak was occurring in one of the feedlot herds. Thirty nine sera (98%) from feedlot cattle with VN titers of 1:2 to 1:128 had positive S/N values (< 0.8). One serum with a VN titer of 1:2 had a borderline (+/-) S/N value of 0.81. After immunization with a commercial gIII-positive IBRV vaccine, 115/116 sera with VN titers of 1:2 to 1:256 had positive S/N values (< 0.8). One serum with a VN titer of 1:2 had a negative S/N value of 0.83. Serum from one vaccinated animal that failed to seroconvert after vaccination (VN < 1:4) showed a strongly positive ELISA S/N of 0.48.     

Host responses to recombinant hemagglutinin B of Porphyromonas gingivalis in an experimental rat model.

Porphyromonas gingivalis, a gram-negative, black-pigmented anaerobe, is among the microorganisms implicated in the etiology of adult periodontal disease. This bacterium possesses a number of factors, including hemagglutinins, of potential importance in virulence. Several hemagglutinin genes have been identified, cloned, and expressed in Escherichia coli. The purpose of this study was to characterize host responses to purified recombinant hemagglutinin B (rHag B), using the conventional Fischer rat as the experimental animal model. The effectiveness of immunization with rHag B on protection against experimental periodontal bone loss following infection with P. gingivalis was also evaluated. Groups of rats were immunized by the subcutaneous route with rHag B in complete Freund's adjuvant, immunized with rHag B and orally infected with P. gingivalis, nonimmunized and noninfected, or orally infected with P. gingivalis only. Serum and saliva samples were collected throughout the experiment and evaluated for serum immunoglobulin G (IgG) and IgM and salivary IgA antibody activity by enzyme-linked immunosorbent assay. No salivary IgA anti-Hag B activity was detected in the various groups of rats. A slight serum IgM response similar to that seen in preimmune samples was observed. Serum IgG antibody activity to Hag B was detected only in samples from rats immunized with rHag B. This response was primarily of the IgG1 and IgG2a subclasses, followed by IgG2b and low levels of IgG2c. Supernatants from rHag B-stimulated splenic lymphoid cell cultures from immunized rats contained high levels of gamma interferon, followed by interleukin-2 (IL-2), IL-10, and then IL-4. These results are consistent with the induction of T helper type 1 (Th1)- and Th2-like responses. Western blot analysis of sera derived from rHag B-immunized rats reacted with trichloroacetic acid (TCA) precipitates of P. gingivalis 33277, 381, A7A1-28, and W50, revealing a 50-kDa band reflective of Hag B. However, sera derived from rats immunized with P. gingivalis whole cells or from rats infected with P. gingivalis only did not react with rHag B but did react with TCA precipitates of P. gingivalis strains. Finally, radiographic measurements of periodontal bone loss indicated that rats immunized with rHag B had less bone loss than those infected with P. gingivalis only. These results demonstrate the effectiveness of purified rHag B in inducing a protective immune response and support the potential usefulness of this component of P. gingivalis in the development of a vaccine against adult periodontitis.     

Natural and immune antibodies for Vibrio fetus in serum and secretions of cattle

Naturally occurring antibodies for Vibrio fetus with whole-cell and O antigen specificities were detected in sera of mature cattle by means of the agglutination and indirect immunofluorescence reactions. O antibodies occurred in each of 21 sera examined, and whole-cell antibodies, in lower concentrations, occurred in 15 of the 21 sera. Natural antibodies were detected in the immunoglobulin G, M, and A (IgG, IgM, IgA) classes. Parenteral immunization with whole cells in Freund's complete adjuvant caused an increase in antibodies, predominantly IgG, with both whole-cell and O specificities; genital infection produced minimal alterations in levels of serum antibody. O antibodies, predominantly of the IgA class, occurred in nasal secretions of most of these animals but only infrequently in saliva or tears. Nasal secretion titers of O antibodies fluctuated widely from week to week but appeared to be unaffected by parenteral immunization or experimental infection. It is hypothesized that the nasal passages serve as a site of antigenic stimulation and synthesis of naturally occurring V. fetus antibodies.     

Local (Immunoglobulin A) Immune Response by the Intestine to Cholera Toxin and Its Partial Suppression with Combined Systemic and Intra-Intestinal Immunization

Chronically isolated Thiry-Vella (T-V) ileal loops in rabbits were used to study the local and systemic immune response to purified cholera toxin (CT). Immunization consisted of intraloop (i.l.), subcutaneous (s.c.), or combined i.l. and s.c. inoculation of CT. Fluid from the loops and sera were tested for neutralization of CT by the blueing test and for relative content of isotype-specific (immunoglobulins A [IgA] and G [IgG]) anti-CT. To demonstrate protection against CT, fluid production by the chronic T-V loops was measured after challenge with CT; an "acute" loop prepared from adjacent intestine at the time of challenge was also tested in some animals. The highest neutralizing titers in loop fluids were found in animals receiving i.l. or i.l. and s.c. inoculations, whereas titers in sera were highest in rabbits receiving s.c. or i.l. and s.c. inoculations. IgA anti-CT in fluids became greatest after i.l. inoculation alone and was lowest in s.c. animals. Combined s.c. and i.l. immunization was accompanied by reduced content of IgA anti-CT in fluids as compared with that obtained with i.l. inoculation alone. This finding strongly suggested a suppressive effect on local immunization by s.c. inoculation. While this suppression may have been due to a direct (toxigenic) effect of CT on lymphocytes, an immunogenic mechanism, probably mediated through suppressor T cells, is favored. Little IgG anti-CT was detected in any loop fluids, but high levels were found in sera after two s.c. inoculations or four i.l. inoculations. Neutralization titers for the fluid specimens showed much better correlation with IgA anti-CT values than with IgG anti-CT values. The chronic and acute T-V loops showed protection against fluid production after exposure to CT in systemically and locally immunized animals. However, IgG anti-CT usually appeared in both loops; leakage of serum antibodies because of surgical manipulation was felt, therefore, to invalidate these protection results as a demonstration of local immunity. In challenge studies in undisturbed chronic loops, only local immunization alone was found to result in definite protection.     

Protection of rat intestine against cholera toxin challenge by monoclonal anti-idiotypic antibody immunization via enteral and parenteral routes.

A mouse monoclonal anti-idiotypic (anti-id) immunoglobulin M (IgM) antibody, called MAb2, was raised against a mouse monoclonal anti-cholera toxin (anti-CT) antibody (MAb1). The MAb2 was shown, by competition with CT for MAb1, to bear the internal image of an epitope of CT. MAb2 immunization of rats was performed via the intraperitoneal, intragastric, and intrajejunal routes and compared with immunization of rats with either a control, isotype- and allotype-matched MAb or with CT via the same routes. Both serum IgG and bile IgA anti-CT Ab3's were detected by enzyme-linked immunosorbent assay in anti-id MAb2-immunized rats, although their titers were lower than those in CT-immunized rats. No anti-CT antibodies were detected in sera and bile of rats immunized with the control MAb. When tested for degree of gut protection against a CT challenge, rats immunized with MAb2 by the intrajejunal route showed a rather high degree of protection, which was only slightly lower than that of rats immunized with CT via the same route; all rats but one immunized with the control MAb were unprotected. There was, however, no correlation between serum or bile anti-CT titers and degree of gut protection in MAb2-immunized rats. Their serum anti-CT Ab3's were purified by adsorption and elution from a CT immunosorbent and resembled anti-CT MAb1 in their unique reactivity with MAb2. This constitutes to our knowledge the second report of protection against a pathogen by anti-id immunization via the enteric route.