Protection against experimental salmonellosis in mice and sheep by immunisation with aromatic-dependent Salmonella typhimurium

Mice immunised by the oral or intraperitoneal route with a live aromatic-dependent strain of Salmonella typhimurium exhibited significantly less protection against oral challenge with 50 LD50 of an ovine isolate of S. typhimurium (12313) than when a bovine isolate with the same O antigens and phage-type as strain 12313 was used as the challenge organism. When challenged with 10 LD50, however, protection against both strains was significantly better than that obtained when mice were vaccinated with killed vaccines (heat-killed, acetone-killed or irradiated) even when the antigenic mass of the killed vaccine was increased by up to 500-fold in an attempt to compensate for the expected limited multiplication of the mutant organism. Sheep immunised with the live mutant strain by either the intramuscular or oral route were protected against oral challenge with the virulent ovine isolate of S. typhimurium; unimmunised sheep died of acute enteritis within 7 days, although there was no evidence of systemic invasion by the challenge organism. After challenge, immunised animals ate more food than the unimmunised controls and suffered only transient, mild diarrhoea. Serum antibody titres against O and H antigens measured by direct or antiglobulin tests were significantly higher in sheep immunised by the intramuscular route than in those immunised orally. Sheep in both immunised groups developed skin swellings within 30 min after intradermal inoculation with purified homologous lipopolysaccharide indicating development of immediate-type hypersensitivity, but only those immunised by the intramuscular route showed significant indurated skin swellings characteristic of delayed-type hypersensitivity 48 and 72 h post-inoculation.(ABSTRACT TRUNCATED AT 250 WORDS)     

IgD antibodies to DNP are specifically induced in ascitic fluid after intraperitoneal immunization.

The induction characteristics of IgD in serum and other body fluids are poorly understood. Here we report that Freund's complete adjuvant (FCA), when used in intraperitoneal (i.p.) immunization, resulted in significantly higher levels of IgD and specific IgD antibodies in ascitic fluid than in the serum of the same animals. This was in sharp contrast to the distribution of IgM and kappa light chain-bearing immunoglobulins (kappa Ig) between these compartments. Female rats were immunized subcutaneously (s.c.) on Day 0 with 1:1 FCA mixed with either 2,4 dinitrophenyl group A streptococcal vaccine (DNP-GASV), 2,4 dinitrophenyl ovalbumin (DNP-OVA), or saline. A week later (and weekly thereafter) they were boosted i.p. with these antigens mixed with FCA 1:9. Eleven of sixteen rats produced some ascites by Day 21, and 15/16 by Day 28. Total immunoglobulin and specific antibodies for the heavy-chain isotypes IgD and IgM and for kappa Ig were measured by ELISA. Between immunization groups no significant differences were observed in total immunoglobulin levels. Subcutaneous immunization with 1:1 FCA caused a significant two- to six-fold increase in serum IgD by Day 7 (P less than 0.01), while no change occurred with serum IgM or kappa Ig. Ascitic fluid collected on Day 21 had significantly high levels of IgD than that of serum IgD (P less than 0.01), with a mean level nine times that of the serum. In contrast, levels of total IgM, kappa Ig and total protein were significantly lower in ascitic fluid than in serum (all P less than 0.05). The high levels of IgD in ascitic fluid disappeared in Day 28 ascitic fluid, while IgM and kappa Ig levels were relatively unchanged. The ratio of ascitic fluid to serum IgD anti-DNP was 9.8 for the DNP-GASV-immunized group on Day 21, and 23.9 for the DNP-OVA-immunized group on day 28. The same ratios for IgM anti-DNP and kappa Ig anti-DNP were much lower, ranging from 0.4 to 2.3 and 0.3 to 3.3, respectively.     

Effect of hydroxyethyl starch (HES) in reducing parasite load in experimental visceral leishmaniasis

Leishmania donovani primarily infects phagocytic cells of the reticuloendothelial system. Hydroxyethyl starch (HES) has been shown to concentrate transiently in these organs. The effect of HES administration was assessed upon infection and also upon vaccination against this parasite. Animals received HES intraperitoneally thrice weekly, either alone (HES) or with a subcutaneous immunization protocol utilizing aluminum hydroxide and killed parasites (ALP-HES). Controls were untreated (NT) or received only the vaccination protocol (ALP). Results showed that animals treated with HES alone exhibited significantly fewer parasites as compared to untreated animals (p less than 0.001). The ALP animals also were protected against infection but demonstrated greater parasite burdens than HES animals. Immunized animals which also received HES demonstrated infection levels similar to those treated with HES alone, thus negating any synergistic effect. The reason for increased protection against L. donovani infection in animals treated with HES is not clear, but it may result from a transient increase in host resistance.     

Antigenic variation of Giardia lamblia in the feces of Mongolian gerbils.

Enzyme-linked immunoelectrotransfer blot was used to study variations in Giardia lamblia antigens in extracts of feces from infected Mongolian gerbils. A 65-kilodalton antigen was found in feces that contained strain WB (ATCC 30957) cysts and in axenic culture of strains WB and CDC:0284:1 that contained trophozoites. The 65-kilodalton antigen from trophozoites of both strains was membrane associated. A 70-kilodalton antigen was found in feces that contained strain CDC:0284:1 cysts. It was persistent in 16 fecal collections and may be strain specific. Similar variations in antigens may occur in human feces. Coproimmunodiagnostic assays that use monoclonal antibodies will have to include all varieties of G. lamblia antigens present in the feces of giardiasis patients.     

In Silico identification of M. TB proteins with diagnostic potential

The development of a new tuberculosis (TB) vaccine has become one of the main objectives of the scientific community. Protein antigens have been widely explored as subunit TB vaccines, however lipid antigens could be equally important to be used or included in such a vaccine. The aim of this study was to demonstrate the potential of a liposome formulation composed of an extract of lipids from Mycobacterium smegmatis (Ms) as a TB vaccine candidate. We evaluated the immunogenicity of this formulation as well as the cross reactive response against antigens from Mycobacterium tuberculosis (MTb) in BALB/c mice. We determined the anti-liposome IgG response in sera from TB patients and from healthy subjects who displayed a positive (PPD+) or negative (PPD-) tuberculin skin test. A significant increase in anti-liposome IgG (p<0.05) was detected in animals immunized with Bacille Calmette-Guérin (BCG) compared with all groups, and in the group immunized with liposomes from Ms (LMs) compared to animals immunized with either LMs adjuvanted with aluminium (LMs-A) or the negative control group (phosphate buffered saline, PBS) respectively. With respect to the cross reactive response against a cocktail of cell wall antigens (CWA) from MTb, significantly higher IgG levels were observed in animals immunized with BCG and LMs compared to negative controls and either, aluminium-adjuvanted liposomes (LMs-A) or montanide (LMs-M) (p<0.05). Furthermore, the anti-liposome IgG response was significantly superior in sera from pulmonary TB patients compared to PPD+ and PPD- healthy subjects (p<0.001) suggesting the expression of these antigens in vivo during active MTb infection. The results obtained provide some evidence for the potential use of liposomes containing total lipid extracts of Ms as a TB vaccine candidate.

     

Evaluation of specific humoral immune response and cross reactivity against <Emphasis Type="Italic">Mycobacterium tuberculosis</Emphasis> antigens induced in mice immunized with liposomes composed of total lipids extracted from <Emphasis Type="Italic">Mycobacterium smegmatis</Emphasis>

The development of a new tuberculosis (TB) vaccine has become one of the main objectives of the scientific community. Protein antigens have been widely explored as subunit TB vaccines, however lipid antigens could be equally important to be used or included in such a vaccine. The aim of this study was to demonstrate the potential of a liposome formulation composed of an extract of lipids from Mycobacterium smegmatis (Ms) as a TB vaccine candidate. We evaluated the immunogenicity of this formulation as well as the cross reactive response against antigens from Mycobacterium tuberculosis (MTb) in BALB/c mice. We determined the anti-liposome IgG response in sera from TB patients and from healthy subjects who displayed a positive (PPD+) or negative (PPD-) tuberculin skin test. A significant increase in anti-liposome IgG (p<0.05) was detected in animals immunized with Bacille Calmette-Guérin (BCG) compared with all groups, and in the group immunized with liposomes from Ms (LMs) compared to animals immunized with either LMs adjuvanted with aluminium (LMs-A) or the negative control group (phosphate buffered saline, PBS) respectively. With respect to the cross reactive response against a cocktail of cell wall antigens (CWA) from MTb, significantly higher IgG levels were observed in animals immunized with BCG and LMs compared to negative controls and either, aluminium-adjuvanted liposomes (LMs-A) or montanide (LMs-M) (p<0.05). Furthermore, the anti-liposome IgG response was significantly superior in sera from pulmonary TB patients compared to PPD+ and PPD- healthy subjects (p<0.001) suggesting the expression of these antigens in vivo during active MTb infection. The results obtained provide some evidence for the potential use of liposomes containing total lipid extracts of Ms as a TB vaccine candidate.     

Genetic manipulation of Salmonella serotype Bovismorbificans to aromatic-dependence and evaluation of its vaccine potential in mice

The generation of smooth aromatic-dependent Salmonella serotype Bovismorbificans (Group C2, O6, 8) from a smooth wild-type parent strain by transduction with phage P1, and conjugation with Salmonella serotype Typhimurium carrying F'-8gal is described. The smooth aromatic-dependent S. serotype Bovismorbificans was non-lethal for mice at an oral challenge dose of 2 x 10(9) cfu (equivalent to 200 LD50 of the parent, wild-type strain). The safety of the auxotrophic mutant was further substantiated by comparing its multiplication kinetics in vivo with that of its virulent parent organisms. Mice immunised with live, smooth aromatic-dependent S. serotype Bovismorbificans by either the oral or intraperitoneal (i.p.) route were protected against oral challenge with virulent S. serotype Bovismorbificans; the degree of protection was significantly better (p less than 0.05) at a challenge dose of 100 or 200 LD50 in mice receiving two rather than one vaccination. In contrast, mice immunised with three doses of the formalin-killed virulent, parent organisms by the i.p. route were not protected, in spite of high antibody titres. Only those mice immunised with the live, smooth aromatic-dependent S. serotype Bovismorbificans i.p. developed significant (p less than 0.01-0.05) delayed-type hypersensitivity.     

Failure of systemic N-acetyl cysteine to protect the rat lung against bleomycin toxicity

In order to see whether systemically administered N-acetyl cysteine (NAC) could protect the lung from bleomycin lung injury, 24 rats were given a constant subcutaneous infusion of NAC (mean 195 mg.kg-1.day-1) for 7 days while 23 rats were given a similar volume of saline. Two days after the start of infusion, half of each group received an endotracheal injection of bleomycin and the other half received a similar volume of saline. All animals were killed 7 days after intratracheal injection and their lungs were prepared for wet-weight to dry-weight ratio (W:D) and morphometric assessment of histological changes. In animals given intratracheal saline, NAC infusion had no effect on weight gain, W:D or morphometry compared to those animals given saline infusions. However, all bleomycin-treated animals had obvious evidence of lung damage. Compared to either group of animals treated with intratracheal saline, the bleomycin-treated groups gained less weight (p less than 0.001), had a higher W:D (p less than 0.001) and an increase in the volume densities of alveolar and duct walls (p less than 0.001), intra-alveolar cells (p less than 0.05) and consolidation (p less than 0.001). There were no significant differences between the two bleomycin-treated groups in any parameter measured. It is concluded that administration of NAC by a constant subcutaneous infusion was not protective against bleomycin lung injury.     

Liposome potentiation of humoral immune response to lipopolysaccharide and O-polysaccharide antigens of Brucella abortus.

Liposomes were evaluated for their effectiveness as vaccine carriers in the potentiation of the mouse humoral response to the lipopolysaccharide (LPS) and O-polysaccharide (OPS) antigens of Brucella abortus. LPS and OPS were extracted from a pathogenic strain of B. abortus and were encapsulated within multilamellar vesicles. Groups of mice, immunized with liposome-encapsulated and free LPS or OPS, were bled weekly and the specific IgM and IgG levels in the sera were determined by an indirect fluorogenic enzyme-linked immunosorbent assay. Humoral response to these antigens were found to be dose-dependent. Mice immunized with LPS and OPS encapsulated within liposomes were found to have significantly higher IgG levels than mice immunized with free LPS and OPS. In addition, the antibody levels in mice that were immunized with liposome-encapsulated LPS and OPS were more sustained and remained at elevated levels--even after 5 weeks post immunization. As expected, OPS was found to be less immunogenic than LPS, but multiple injections of OPS encapsulated within liposomes greatly improved the immunogenicity. These results indicate that the humoral response to LPS and OPS of B. abortus can be enhanced when these antigens are encapsulated within liposomes.     

Potentiation of autoimmune response in rats infected with Toxoplasma gondii. Inhibition of suppressor system and impairment of thymic cellular populations

In the present work we studied the influence that an infection with Toxoplasma gondii in thymus proximity produces on the suppression of autoimmune response to autoantigen of rat male accessory glands (RAG). The suppression was achieved injecting syngeneic animals with low doses of autoantigen of RAG previous to the immunization with chemically modified rat male accessory glands (MRAG). Rats were infected in thymus proximity with 3 x 10(3) trophozoites of T. gondii before or after to be suppressed. Controls were rats only infected or only suppressed. The delayed hypersensitivity response against MRAG, (DTH test), was significantly potentiated in rats only infected and in the animals suppressed before the infection (p less than 0.001). The suppression was not inhibited in the animals suppressed after infection. The suppression of humoral response against MRAG studied by ELISA and passive hemagglutination test was prevented in rats infected before as well as in rats infected after the induction of suppression (p less than 0.001). Decrease of CD4+ CD8+ and Ox18+ (class I MHC antigen) and increase of CD4+ CD8- and CD4- CD8- thymocytes was observed in the rats where the DTH response was potentiated. These results indicate that the infection with T. gondii in thymus proximity was able to inhibit the suppression of response to autoantigen of RAG producing selective impairment in thymic suppressor influence.     

Entamoeba histolytica: changes in the zymodeme of cloned nonpathogenic trophozoites cultured under different conditions

In this paper we report the occurrence of changes in the migration of certain isoenzymes of a cloned strain (MAV-CINVESTAV) ofEntamoeba histolytica. This strain was isolated from an asymptomatic carrier and showed an initial nonpathogenic zymodeme I. The transfer of polyxenic trophozoites from Robinson's medium (7% serum) to Jones' medium (30% serum) provoked changes in isoenzyme expression, resulting in the conversion of zymodeme I to a zymodeme that was similar to the XVII zymodeme except for two slow-running bands and a single fast-running band that were detected for hexokinase (HK). This XVII-like zymodeme reverted to zymodeme I when trophozoites were cultured under monoxenic conditions in TY1-S-33 medium (10% serum). When we cultured cloned strain MAV-CINVESTAV under axenic conditions in TY1-S-33 medium, trophozoites expressed a pathogenic zymodeme with two fast-running HK bands and a betaphosphoglucomutase band. In addition, phagocytosis and the ability of the trophozoites to destroy cell-culture monolayers were expressed only in trophozoites cultured under axenic conditions. The axenization procedure required the presence of liveFusobacterium symbiosum and is also described herein.Abbreviations HK hexokinase - ME l-malate: NADP⁺ oxidoreductase - GPI glucose phosphate isomerase - PGM phosphoglucomutase - P pathogenic - NP nonpathogenic - px polyxenic - mx monoxenic - ax axenic     

Pasteurisation and Homogenisation of Milk Enhances the Immunogenicity of Milk Plasma Proteins in a Rat Model

Groups of rats were immunised intraperitoneally with 0.5 ml of raw milk, skim milk, pasteurised milk or pasteurised/homogenised milk. On day 14, animals were boosted with identical preparations, and serum samples were collected on day 28 for the measurement of IgG antibodies directed against milk plasma proteins. Samples were assayed for antibodies to casein, beta-lactoglobulin, bovine gamma globulin and bovine serum albumin. Significantly higher concentrations of antibodies of all specificities were detected in the serum of animals immunised with pasteurised/homogenised milk compared with animals immunised with raw or skim milk. Higher concentrations of antibodies were also seen in the group immunised with pasteurised/homogenised milk than the group immunised with pasteurised milk, although significant differences were only seen in the response to casein (p < 0.01). Additional animals were twice immunised with either raw milk fortified with keyhole limpet hemocyanin (KLH), or pasteurised/homogenised milk which had been fortified with KLH prior to processing. Such treatment significantly enhanced the immunogenicity of the KLH (p < 0.05). These results raise the possibility that homogenisation may similarly effect the way in which the human immune system interacts with cows' milk proteins in the gastrointestinal tract, and suggest that milk processing may be an important variable to consider in studies of human allergy to cows' milk proteins.     

Phorbol esters specifically enhance the cytolytic activity of Entamoeba histolytica.

Entamoeba histolytica causes invasive amebiasis by lysis of host tissue and inflammatory cells. The in vitro cytolysis of target Chinese hamster ovary (CHO) cells by axenic E. histolytica trophozoites (strain HM1:IMSS) is a calcium- and phospholipase A-dependent event initiated by the binding to the target cell of the galactose-inhibitable surface lectin of the parasite. We utilized phorbol esters as a probe to determine whether an amebic protein kinase C has a role in the cytolytic event. The addition of phorbol 12-myristate 13-acetate (PMA) at 10(-6) or 10(-7) M resulted in a greater than twofold enhancement of amebic killing of target CHO cells over 30 min (P less than 0.01). Prior exposure of only the amebae, but not the CHO cells, to PMA produced a similar effect (P less than 0.01). The inactive analog 4-alpha-phorbol had no effect on amebic killing of CHO cells. The PMA-mediated enhancement of amebic cytolysis persisted for up to 60 min after a 5-min exposure; however, after a 30-min exposure to PMA (10(-6) M) there was no augmentation of amebic killing of CHO cells. PMA (10(-6) M) did not promote adherence of parasites to CHO cells but did enhance amebic cytolysis of previously adherent target cells (P less than 0.01). Sphingosine, a specific inhibitor of protein kinase C, abolished both the PMA-stimulated and the basal cytolytic activity of E. histolytica. PMA enhanced CHO cell cytolysis by the less virulent wild-type strain H-303:NIH (P less than or equal to 0.02) but did not augment the activity of the less virulent strain H-200:NIH or two avirulent clones of HM1 (L6 and C919). In summary, these experiments with the phorbol esters and sphingosine as probes to modulate the activity of protein kinase C indicate participation of a parasite protein kinase C in the cytolytic activity of virulent, axenic E. histolytica trophozoites and thus in the pathogenesis of amebiasis.     

Effect of cytochalasin D on the growth,encystation, and multinucleation of <Emphasis Type="Italic">Entamoeba invadens</Emphasis>

The effect of cytochalasin D, a specific inhibitor of microfilaments, on the growth, encystation, and multinucleation of Entamoeba invadens was examined. Cytochalasin D blocked the growth of axenic E. invadens strain IP-1 in a dose-dependent manner, which suggests that the drug is effective against this species of Entamoeba as well as against E. histolytica strain HM1: IMSS as previously demonstrated. Encystation of E. invadens as induced in vitro was also inhibited by cytochalasin D. This is the first evidence of the participation of microfilaments in the encystation process. Concentrations of cytochalasin D effective for the inhibition of encystation were lower than those effective for the inhibition of growth. Trophozoites grown with cytochalasin D became multinucleate; more than three nuclei per cell were observed in 71% of trophozoites grown in the presence of the drug as opposed to only 5% of those grown in the absence of the drug. Also, trophozoites grown with cytochalasin D produced multinucleate cysts following their transfer to encystation medium. Encystation with cytochalasin D was more strongly inhibited among trophozoites grown in the presence of the drug than among those grown in the absence of the drug. Also, encystation without cytochalasin D was less frequently observed among trophozoites grown in the presence of the drug than among those grown in the absence of the drug. Thus, the multinucleation of trophozoites induced by cytochalasin D had an inhibitory effect on their encystation. Received: 28 September 1999 / Accepted: 25 November 1999     

Experimental immunisation of hamsters with lipopolysaccharide antigens of Leptospira interrogans

Hamsters were immunised with leptospiral lipopolysaccharide (LPS) or the polysaccharide (PS) fraction of LPS from Leptospira interrogans serovar copenhageni and the antibody responses were measured by agglutination tests. Maximum titres were observed approximately 6 weeks after immunisation and protection against lethal challenge with the homologous strain was afforded by immunisation with as little as 2.5 micrograms of LPS or PS. All animals produced IgM agglutinins but a higher proportion of-animals immunised with PS produced IgG agglutinins than did those immunised with LPS. Immunisation of guinea-pigs with autoclaved PS showed that the preparation retained some but not all of its immunogenic activity.     

Natural antibodies to treponemal antigens in four strains of guinea-pigs.

A total of 185 serum samples obtained from healthy male and female guinea-pigs of inbred strains 2 and 13 and outbred strains C4D and Hartley A were examined for natural antibodies to treponemal antigens by ELISA using Treponema pallidum (TP), T. phagedenis biotype Reiter (TR) and T. vincentii (TV) antigens and by the FTA test. The prevalence and titres of natural antibodies depended on the age and strain of guinea-pig and the treponemal antigen used. One- and 7-day-old guinea-pigs contained significantly (P less than 0.001) higher levels of natural antibodies than did animals 1 or 3-6 months old. The similar high levels of natural antibodies in newborn guinea-pigs and their mothers (12-30 months old) and the sharp drop observed at the age of 1 month suggested maternal transfer as the mechanism of acquisition. In young adults 3-6 months old, the age group most susceptible to TP infection, antibodies to TP and TR were at their lowest levels, but antibodies reacting to TV had already begun to rise. Natural antibodies were of the IgG1 and IgG2 but not of the IgM class. The highest levels of natural antibodies were in the C4D guinea-pigs; the lowest were in the Hartley A strain. Natural antibody activity was inhibited or adsorbed by TR antigens.     

Mapping of B-cell epitopes in rabbits immunised with various gag antigens for the production of HIV-1 gag capture ELISA reagents

An HIV-1 p24 capture enzyme linked immunosorbent assay (ELISA) was developed and used in a study of B-cell epitopes in rabbits immunised with different gag p24 antigens. Rabbits were immunised with virion HIV-1/Lai, baculovirus recombinant p24, Escherichia coli recombinant p24-15 and a mixture of synthetic peptides representing sequences of HIV-1 gag p24 protein, respectively. Five out of nine rabbits developed antibodies that could be used for an antigen capture ELISA. No significant differences in IgG titers to the whole gag protein were seen when comparing rabbits immunised with four different antigens. Three major common linear epitope regions were mapped in the rabbits immunised with virion HIV-1/Lai and baculovirus recombinant p24. The rabbit immunised with HIV-1 gag peptides had the broadest linear epitope reactive responses whereas animals immunised with E. coli recombinant antigen had the most restricted linear epitope response. The capture ELISA method thus developed using the different rabbit anti-p24 IgG preparations was shown to capture isolates from HIV-1 subtypes or clades A to G. Only rabbits immunised with virion HIV-1/Lai and baculovirus recombinant p24 developed IgG that was capable of efficiently capturing HIV-1 p24 in ELISA, indicating the importance of preparing antibodies able to recognise native or discontinuous and linear antigen configurations.     

Adjuvanticity and protective immunity elicited by Leishmania donovani antigens encapsulated in positively charged liposomes.

In the search for a leishmaniasis vaccine, extensive studies of cutaneous leishmaniasis have been carried out. Investigations in this regard with the visceral form are limited. As an initial step in the identification of the protective molecules, leishmanial antigens extracted from the membranes of Leishmania donovani promastigotes, alone or in association with liposomes, were evaluated for their immunogenicity and ability to elicit a protective immune response against challenge infection. Intraperitoneal immunization of hamsters and BALB/c mice with the leishmanial antigens conferred protection against infection with the virulent promastigotes. Encapsulation in positively charged liposomes significantly enhanced the protective efficacy of these antigens. The splenic parasite burden of hamsters was reduced by 97% after 6 months of infection. BALB/c mice exhibited 87 and 81.3% protection in the liver and spleen, respectively, after 4 months of infection. These protected animals elicited profound delayed-type hypersensitivity and increased levels of Leishmania-specific immunoglobulin G (IgG) antibodies. Protection in mice also coincided with elevated levels of IgM and IgA antibodies, which decreased with disease progression in the control-infected animals. Although both IgG1 and IgG2a antibodies were present in the sera of infected mice, IgG1 appeared to be the predominant isotype, suggesting a preferential induction of the Th2 type of immune response over that of Th1. Effective stimulation of all the IgG isotypes, particularly IgG2a, after immunization with liposome encapsulated antigens seems to be responsible for the significant levels of resistance against the disease. Taken together, these data indicate a potential for the liposomal antigens as a vaccine which could trigger both humoral and cell-mediated immune responses.     

Ability of a new infant formula prepared from partially hydrolyzed bovine whey to induce anaphylactic sensitization: evaluation in a guinea pig model

In the present study we evaluated the allergenicity and immunogenicity of a whey partially hydrolysate formula (PHF) in a guinea pig model. Nine groups of 10 guinea pigs received either a conventional milk formula (CMF) or PHF for 37 days. After intravenous (i.v.) challenge with either α-lactoglobulin (β-L) or ultracentrifuged (u)CMF, animals fed CMF showed, respectively, 80% and 100®0 fatal reactions, whereas animals fed PHF showed no reactions when i.v. challenged both with (3-L and uPHF. Eighty percent fatal reactions, and 10%, respectively, of severe and mild reactions have been observed in the CMF-fed, casein-challenge group. In contrast, only one (10%) mild reaction occurred in the PHF-fed, casein-challenged group. When challenged with u-pasteurized cow's milk (uPCM), CMF-fed animals showed 86% fatal reactions and 14% mild reactions, whereas PHF-fed ones presented 70% no reactions, 20%, mild reactions, and one (10%) fatal reaction. Animals fed CMF showed a significantly higher level of specific IgG against cow's milk antigens than PHF-fed ones, which, however, presented higher levels of antibodies than a water-supplemented control group. The present results confirm that PHF is less sensitizing than CMF in a guinea pig model.     

The influence of lithium chloride on experimental autoimmune thyroid disease.

Lithium administration is known to be associated with the development of thyroid dysfunction; it also exerts an effect on the immune system. The effect of lithium on experimental autoimmune thyroid disease was studied in female August rats. Following immunization with rat thyroglobulin in Freund's complete adjuvant, lithium chloride was administered i.p. for 30 days to four groups at varying stages of the disease. Control animals received i.p. saline. Anti-thyroglobulin antibody levels (measured by ELISA) were significantly increased in rats given lithium immediately post-immunization (group B) compared to control animals (661 +/- 42 OD vs 448 +/- 68; mean +/- s.e., P less than 0.02). In contrast, animals which received lithium during the spontaneous resolution of the disease (group D) showed a significant fall in anti-TG antibody compared to controls (99 +/- 15 vs 27 +/- 15; P less than 0.001). Anti-TG antibody levels remained undetectable in animals which received lithium but were not immunized. The splenic T cell blastogenic response (as measured following phytohaemagglutinin stimulation) was significantly increased in rats receiving lithium prior to and during immunization (group A) (stimulation index 63.4 +/- 6.9 vs 10.2 +/- 2.4; P less than 0.001). Spontaneous cell proliferation of splenic lymphocytes was decreased in two lithium treated groups (group A P less than 0.005, group C P less than 0.05). There was no alteration in splenic weight or the degree of thyroid lymphocytic infiltration in any of the treated group. Lithium exerted both positive and negative influences on the immune system in rats immunized with thyroglobulin in adjuvant but did not induce autoantibody production in normal rats.