High Levels Of Protective Immunity Research Articles

Protective immunity to Schistosoma mansoni induced in the olive baboon Papio anubis by the irradiated cercaria vaccine.

The radiation-attenuated schistosome vaccine induces a high level of protective immunity in rodents. In order to assess its potential relevance to man, we have tested its efficacy in the non-human primate Papio anubis. A vaccination regime consisting of 3 exposures of approximately 9000 cercariae irradiated with 30 or 60 krad. of gamma radiation induced > 50% protection to a challenge with normal larvae. A lower attenuating dose of 20 krad., optimal for vaccination of mice, was less effective. All vaccination regimes elicited a population of PBMC which proliferated in vitro in response to antigen. These responses peaked after the third exposure but were significantly lower after challenge. They revealed relatively little cross-reactivity with adult Schistosoma haematobium antigens and provided some evidence for stage-specific antigens. Circulating IgM reactive with adult S. mansoni antigen was detected after the second vaccination but levels remained low throughout. In contrast, IgG levels were boosted by successive vaccinations, although they showed a tendency to decline from 14 days after each exposure. There also appeared to be a lag of about 14 days after challenge before levels began to rise. Thus, both proliferation and antibody data suggest a lower responsiveness after challenge which may reflect either the reduced antigenic load or immunogenicity of normal, compared to vaccinating larvae. The data indicate that the attenuated schistosome vaccine is capable of inducing protection in a highly permissive primate host, with the implication that the mechanisms involved may also be relevant to man.

Phenotypes of Heligmosomoides polygyrus Selected to Survive Protective Immunity in Quackenbush Mice

The survival of Heligmosomoides polygyrus phenotypes passaged selectively through naive (Hpn) and immune (Hpa) outbred Quackenbush (Q) mice was compared in Q mice immunized passively with normal (NMS) and immune mouse serum (IMS). IMS raised against Hpn(Q) worms (IMS-N) was 93% and 92% protective against Hpn(Q) and Hpa(Q) phenotypes, respectively; IMS against Hpa(Q) (IMS-A) conferred 93% protection against the Hpn(Q) phenotype but gave only 45% protection against the adapted Hpa(Q) parasites (P < 0.01). IMS-A had less anti-parasite IgG reactivity than did IMS-N (P < 0.05). A 34-kDa antigen from male Hpn(Q), but not Hpa(Q) worms, and an antigen at 56 kDa in male Hpa(Q), but not Hpn(Q) parasites, reacted on immunoblots with both sets of IMS. Thus, it appeared that Hpa(Q) worms endured higher levels of protective immunity than did Hpn(Q) worms and that Hpa(Q) and Hpn(Q) phenotypes had different antigens, which, however, did not lead to phenotype-specific immunity. This reflects the complexity of host-parasite interactions.

Pasteurella haemolytica Vaccines and Their Effectiveness

Pasteurella haemolytica biotype A, serotype 1 (Ph1) bacterins and bacterin-toxoids formulated in oil adjuvants induce protective immune responses approaching those induced by virulent Ph1. In comparison, aluminum hydroxide based adjuvants induce lower protective and serological immune responses. Bacterin-toxoid vaccines formulated in water-in-oil adjuvants induced high levels of protective immunity against transthoracic and field challenge. Bacterin-toxoid with oil-in-water adjuvant induced high protective immunity against transthoracic challenge and was superior to Ph1 bacterin-toxoid withAI(OH)3 adjuvant. Reactions at the point of inoculation vary with formulations, are usually inapparent if intramuscular, manageable if subcutaneous and disappear with time.

The effects of gamma radiation on the development of Heligmosomoides polygyrus bakeri in mice

The development of a Heligmosomoides polygyrus bakeri ( H. polygyrus) primary infection in its definitive host was severely effected by a wide range of gamma radiation doses (10–400 Gy). Male worms were more susceptible to gamma radiation than female worms. A dose of 400 Gy prevented the development of L3 larvae to mature female worms and 200 Gy abrogated the maturation of males. At 300 Gy, a dose known to stimulate high levels of protective immunity, male worms were unable to moult to the L4 stage and females failed to develop into morphologically normal adults. An experiment to select for a radiation resistant parasite line provided data on the cumulative effects of gamma rays on successive parasite generations. Parasite fitness data demonotrated that worm development, at the level of embryogenesis, was for more sensitive to radiation damage than either post embryonic development or adult worm fecundity. The parasite line died out on the 14 th generation of selection after receiving an accumulated dose of 420 Gy. It is concluded that gamma radiation profoundly alters the developmental biology of H. polygyrus in a dose-dependent manner, with maximal sensitivity exhibited during embryogenesis.

Taenia ovis recombinant vaccine--'quo vadit'.

Several years have elapsed since the publication by Johnson et al. (1989) of the cloning of a recombinant antigen from the cestode parasite Taenia ovis which stimulated high levels of protective immunity in sheep. A great deal of subsequent research and development was necessary to bring the fledgling vaccine to the point of being a registered commercial product. The results of these subsequent studies are dealt with briefly in this paper, including the results of field trials. The T. ovis vaccine was registered by the New Zealand Animal Remedies Board in February 1994. Where then is the commercial product? This paper gives a background to market problems which have emerged through the politics (and realities) of the NZ T. ovis control campaign. It serves as notice that the best science dedicated to producing vaccines or products for parasitic, or other, diseases often faces significant hurdles in the real world of commerce and politics.

Major cytoplasmic membrane protein of Legionella pneumophila, a genus common antigen and member of the hsp 60 family of heat shock proteins, induces protective immunity in a guinea pig model of Legionnaires' disease.

We have examined the capacity of the major cytoplasmic membrane protein (MCMP) of Legionella pneumophila, a genus common antigen and member of the hsp 60 family of heat shock proteins, to induce protective immunity in a guinea pig model of Legionnaires' disease. We purified MCMP to homogeneity from L. pneumophila by buffer extraction, ion-exchange chromatography, and molecular sieve chromatography. Guinea pigs immunized with MCMP developed a strong cell-mediated immune response to the immunogen manifest by marked cutaneous delayed-type hypersensitivity. Guinea pigs immunized with MCMP and then challenged with a lethal aerosol dose of L. pneumophila exhibited a high level of protective immunity. Altogether, in four independent experiments, 55 of 64 (86%) animals immunized three times with 0.6-40 micrograms MCMP including 11 of 11 (100%) animals immunized three times with 40 micrograms MCMP survived aerosol challenge with L. pneumophila compared with 1 of 29 (3%) sham-immunized control animals (P < 0.0001, Cochran-Mantel-Haenszel X2 statistic for pooled data). To our knowledge, MCMP is the first member of the hsp 60 family of proteins shown to induce protective immunity to a microbial pathogen. MCMP has potential as a vaccine against Legionnaires' disease. Since MCMP is a genus common antigen, vaccination with a combination of MCMPs derived from different Legionella species has the potential of inducing protective immunity against all the major Legionella species causing human disease.

Experimental models of immunization against schistosomes: lessons for vaccine development.

Schistosomiasis is a debilitating, and sometimes deadly, parasitic infection that afflicts hundreds of millions of people living in developing countries. One of the best hopes for control of this disease is vaccine development. Studies on experimental models of attenuated vaccines have proven that high levels of protective immunity can be achieved. In these systems, resistance has been shown to be directed against the migrating larval stages of the parasite and to have both cellular and humoral components. Several candidate vaccine immunogens have been identified on the basis of antibody reactivity. However, the level of protection induced by immunization with nonliving vaccines has at yet not approached the level observed with attenuated infection. Current challenges to vaccine development include identification of protective T cell immunogens, determination of ways to strengthen the immunogenicity of isolated parasite antigens, and development of methodologies to selectively stimulate protective, as opposed to ineffective or even detrimental, immune responses.

Comparison of protective immunity elicited by recombinant vaccinia viruses that synthesize E or NS1 of Japanese encephalitis virus

Immunization with recombinant vaccinia viruses that specified the synthesis of Japanese encephalitis virus (JEV) glycoproteins protected mice from a lethal intraperitoneal challenge with JEV. Recombinants which coexpressed the genes for the structural glycoproteins, prM and E, elicited high levels of neutralizing (NEUT) and hemagglutination inhibiting (HAI) antibodies in mice and protected mice from a lethal challenge by JEV. Recombinants expressing only the gene for the nonstructural glycoprotein, NS1, induced antibodies to NS1 but provided low levels of protection from a similar challenge dose of JEV. Antibodies to the NS3 protein in postchallenge sera, representing the degree of infection with challenge virus, were inversely correlated to NEUT and HAI titers and levels of protection. These results indicate that although vaccinia recombinants expressing NS1 can provide some protection from lethal JEV infection, recombinants expressing prM and E elicited higher levels of protective immunity.

Reinfection after treatment of schistosomiasis: environment or "predisposition"?

Although very efficient for the control of morbidity due to S. mansoni in individual patients, chemotherapy has not proven successful in the management of transmission within hyperendemic areas when used alone, even if repeated at short intervals. Consequently, a great deal of effort has been expended toward immunologic investigation and development of a specific vaccine. Based upon a study of a group of children (5-14 years) from the state of Alagoas, the author demonstrates that the outcome one year after chemotherapy depends essentially on the "risk rating" of the area of domicile. A regression analysis did not reveal significant correlation to neither age, sex or initial egg counts. Although the study was not designed to reveal individual variations in the immune status, it is postulated that putative differences in genetic make-up are irrelevant in terms of large-scale intervention. Since morbidity due to S. mansoni has substantially declined during the last two or three decades, a control policy based on vaccination can only be justified if high levels of protective immunity can be attained. At any rate, such a vaccine will have to be administered in early childhood (preferably below the age of three). It can also be demonstrated that immunization in adolescence or adulthood serves no purpose whatsoever. The author is convinced that environmental intervention, usually dismissed as unrealistic in terms of the developing countries, is not only feasible, if done on a selective basis, but prioritary.

Protective Immunity Induced by Porin in Experimental Mouse Salmonellosis

The induction of protective immunity to mouse salmonellosis by porin from Salmonella typhimurium LT2 was studied. The immunization with porin induced a high level of protective immunity to salmonellosis in BALB/c mice. Mice immunized with porin exhibited significant levels of delayed-type hypersensitivity response and interleukin-2 production, indicating that porin was capable of inducing cell-mediated immunity (CMI). Furthermore, we found that both T cells and sera taken from the porin-immunized mice could transfer the protection against salmonellosis into nonimmunized mice. These observations suggested that a high level of the protection to salmonellosis obtained by the porin immunization resulted from the induction of CMI in addition to humoral immunity.

Vaccination with the major secretory protein of Legionella pneumophila induces cell-mediated and protective immunity in a guinea pig model of Legionnaires' disease.

We have examined the capacity of the major secretory protein (MSP) of Legionella pneumophila to induce humoral, cell-mediated, and protective immunity in a guinea pig model of Legionnaires' disease. MSP was purified to homogeneity by ammonium sulfate precipitation, molecular sieve chromatography, and ion-exchange chromatography. The purified MSP was nonlethal and nontoxic to guinea pigs upon subcutaneous administration. Guinea pigs immunized with a sublethal dose of aerosolized L. pneumophila or a subcutaneous dose of MSP developed a strong cell-mediated immune response to MSP. Such guinea pigs exhibited marked splenic lymphocyte proliferation and cutaneous delayed-type hypersensitivity to MSP in comparison with control animals. Guinea pigs immunized with MSP also developed a strong humoral immune response to MSP, as assayed by an ELISA. The median reciprocal antibody titer was 362 (range 45 to greater than 2,048) for immunized animals compared with less than 8 for controls. In contrast, guinea pigs immunized with a sublethal dose of L. pneumophila failed to develop anti-MSP antibody. Guinea pigs immunized with MSP and then challenged with a lethal aerosol dose of L. pneumophila exhibited highly significant protective immunity in each of five consecutive experiments. MSP induced protective immunity in dose-dependent fashion (40 greater than 10 greater than 2.5 greater than 0.6 micrograms MSP); vaccination with two doses of as little as 2.5 micrograms MSP induced significant protective immunity (p = 0.01, Fisher's Exact Test, two-tailed). Altogether, 21 (81%) of 26 animals immunized with 40 micrograms MSP survived challenge compared with 0 (0%) of 26 sham-immunized control animals (p = 7 x 10(-10), Fisher's Exact Test, two-tailed). MSP-immunized but not control guinea pigs were able to limit L. pneumophila multiplication in their lungs. This study demonstrates that (a) guinea pigs sublethally infected with L. pneumophila develop a strong cell-mediated immune response to MSP; (b) guinea pigs immunized with MSP develop a strong humoral and cell-mediated immune response to MSP; (c) guinea pigs immunized with MSP develop a very high level of protective immunity to lethal aerosol challenge with L. pneumophila; and (d) MSP-immunized animals are able to limit L. pneumophila multiplication in their lungs. MSP, an extracellular protein of an intracellular pathogen, has potential as a vaccine for the prevention of Legionnaires' disease. Secretory molecules of other intracellular pathogens may also have vaccine potential.

Recombinant avirulent Salmonella vaccine strains with stable maintenance and high level expression of cloned genes in vivo.

Salmonella typhimurium strains with deletion (delta) of the adenylate cyclase (cya) and cyclic AMP receptor protein (crp) genes are avirulent for mice and induce a high level of protective immunity to oral challenge with up to 10,000 times what would be a lethal dose of wild-type virulent S. typhimurium cells. This immunity begins as early as seven days after immunization and lasts for at least four months. S. typhimurium delta cya delta crp mutants stably maintain plasmids and give high-level expression of cloned gene products; in this they appear superior to other avirulent S. typhimurium strains. S. typhimurium delta cya delta crp strains with a delta asd mutation (abolishing production of aspartate beta-semialdehyde dehydrogenase), have an obligate requirement for diaminopimelic acid (DAP). This strain can be used in conjunction with plasmid vectors lacking antibiotic resistance markers but having the wild-type asd+ gene from Streptococcus mutans to complement the delta asd chromosomal mutation. The Asd+ plasmid vector can be used to express a diversity of colonization and virulence antigens from other pathogens. In the delta cya delta crp delta asd S. typhimurium vaccine strain, the plasmid is completely stable in the absence of any exogenous selective pressure either in vitro or in vivo.

Immunity and cross‐protection to nephritis produced by Australian infectious bronchitis viruses used as vaccines

Four series of viruses were generated by passage through eggs incubated at 31 degrees C. Initial evaluation of these viruses in SPF chickens showed that they had been successfully attenuated with regard to nephritis following between five and 25 egg passages. In addition, within each series viruses could be selected that minimised deaths from nephritis whilst optimising protective immunity against virulent challenge. Eight viruses were selected and used to vaccinate birds with maternal antibodies to IB. The viruses produced minimal mortalities and protected birds from subsequent challenge. Three viruses were selected from the latter trial and subjected to a cross protection experiment with three serologically distinct virulent challenge viruses: Ql/73, Nl/62 and N9/74. All the vaccine viruses protected birds from challenge while 2032/10 protected birds better than Vac 3/10 or Vac G/15. Finally, 2032/10 and Vac A3 were used in a similar experiment. Both proved to be mild, in terms of pathogenicity to the kidneys, and produced high levels of protective immunity against the three serologically distinct challenge viruses.

Fowl Cholera Vaccination of Growing Turkeys with CU Strain Via Routes Other Than Oral

Turkeys developed a high level of protective immunity and serum anti-Pasteurella multocida antibody when vaccinated with the Clemson University (CU) strain of P. multocida via the following routes: wing-web puncture with the recommended dosage or 1:10 dilution of this dosage, subcutaneous, crop injection, cloacal perfusion of the bursa of Fabricius, and intratracheal. The development of immunity after vaccination via the wing-web puncture and subcutaneous routes was dose-dependent: the lower dosages induced less serum antibody and protective immunity. Immunity was greatest 3 weeks after vaccination via wing-web puncture, although immunity was evident as early as 4 days after vaccination. A high level of antibody and protective immunity with no adverse reactions was induced by vaccinating twice, either by the drinking water followed by a similar dosage parenterally or by a parenteral route followed by the drinking water; these regimens were similar to one vaccination in the drinking water. Vaccination via wing-web puncture and possibly subcutaneous injection and bursal perfusion could be used for flocks with a history of a high mortality after vaccination with the CU vaccine in the drinking water and suspected of being immunosuppressed.

Protective immunity to Ascaris suum: Analysis of swine peripheral blood cell subsets using monoclonal antibodies and flow cytometry

Outbred domestic swine or SLA inbred miniature swine were exposed to Ascaris suum either naturally on contaminated lots or by inoculation with UV-irradiated attenuated eggs. Both inbred and outbred swine developed virtually complete protection to a challenge of 10 000 eggs after natural exposure, but inbred swine were less resistant than outbred swine after UV-egg exposure. Flow cytometric analysis of peripheral blood mononuclear cells from these animals, performed to determine changes in cell subsets including helper T-cells, cytotoxic/suppressor T-cells, macrophages, and cells expressing class II major histocompatibility antigens, showed that both outbred and inbred swine had similar responses after parasite exposure. The levels of helper T-cells and cytotoxic/ suppressor T-cells did not change after parasite exposure, while there was an appreciable but transient increase in macrophages only in those swine naturally exposed to A. suum. Swine exposed to A. suum, both naturally and by inoculation with UV-eggs, showed an increase in the amount of class II antigens detectable per cell. In a second set of experiments, outbred swine were exposed to A. suum naturally or by repeated experimental inoculation with different doses of normal eggs, and protective immunity and changes in blood cell subsets were determined. The greatest change in blood cell subsets was found at 3 and 5 weeks after initial parasite exposure, when macrophages were elevated moderately in a group of pigs inoculated every other day with 1000 eggs and markedly in a group that was naturally exposed; class II antigen expression was also increased during this period. These increases preceded peak serum antibody responses, which were lower in the naturally-exposed group relative to the experimentally-inoculated group. Both groups had high levels of protective immunity. This suggests that natural exposure to A. suum may activate cells and enhance specific immune responses to give high levels of protection.

Immunogenicity of subcellular fractions from yeast cells of Histoplasma capsulatum.

We have previously demonstrated a high degree of protection in mice immunized with partially purified ribosomes and ribosomal protein from H. capsulatum. In order to define more precisely the nature of the protective antigen(s), we have further investigated the immunogenicity of different subcellular fractions from yeast cells of H. capsulatum. The ribosomes and a membrane-rich cytoplasmic fraction from Histoplasma protected 90-100% of the immunized mice against a lethal challenge with yeast cells of H. capsulatum. The ribosomes incorporated 14C-L-phenylalanine in a poly U directed cell-free protein synthesizing system and could be dissociated into 40 and 60S subunits. Significant but somewhat lower levels of protection were obtained with the mitochondrial fractions. In contrast, only 30-50% protection was observed with cell wall preparations and 20-40% protection with microsomal and ribosomal supernates. High levels of protective immunity were observed when mice were immunized with combination of suboptimal doses of ribosomes and cell walls. Immunization with ribosomes from Saccharomyces cerevisiae and Candida albicans in combination with Histoplasma cell walls did not elicit significant protection against H. capsulatum, indicating the specific nature of the immune response. These results demonstrate that ribosomes and membrane-rich cytoplasmic fractions are the major protective cellular constituents of Histoplasma. Furthermore, the combination of purified immunogenic subcellular constituents in the ritht proportion may provide a safe and effective veccine against histoplasmosis.

Effect of selenium and dimethyl dioctadecyl ammonium bromide on the vaccine-induced immunity of Swiss-Webster mice against malaria (Plasmodium berghei).

The results of the study described in this paper demonstrate that selenium, administered in drinking water, potentiates the protective effect of a killed Plasmodium berghei vaccine for Swiss-Webster mice. We also report that a vaccine consisting of P. berghei antigen combined with the adjuvant dimethyl dioctadecyl ammonium bromide conferred a significantly high level of protective immunity. An additive effect was shown in that the greatest degree of protection was afforded to the group of mice maintained on selenium and vaccinated with antigen-dimethyl dioctadecyl ammonium bromide. Almost all of the animals treated in this manner survived the challenging infection, the course of which was typically of a transitory parasitemia not exceeding 10% at the peak.