Safety and immunogenicity of different booster vaccination schemes for COVID-19 used in El Salvador

Purpose

The effectiveness of coronavirus disease 2019 (COVID-19) vaccination schemes and the combination of vaccines of various platforms for administering booster doses is still being studied since it will depend on the population's response to vaccines. We aimed to evaluate the safety, protection, and immunogenicity of the Salvadorean population's third dose booster COVID-19 vaccine and the potential benefit of homologous vs. heterologous regimens.

Materials and Methods

This is an analytical observational cohort study in a population aged 18 to 65 years that was primarily vaccinated with AstraZeneca, Sinovac, or Pfizer/BioNTech. Volunteers were recruited (n=223) and followed up for 3 months after receiving the 3rd vaccine (BNT162b2) as a booster. Adverse reactions were monitored, serum anti-spike immunoglobulin G (IgG) was assessed by chemiluminescence, and a polymerase chain reaction was carried out when subjects developed clinical signs.

Results

The cohorts finally included 199 participants, and we observed only mild adverse effects in all cohorts. A significant increase in specific IgG levels was found after the booster dose in all cohorts. The heterologous scheme with Sinovac showed the greatest increase in antibody titer, and a decrease was observed in all participants after 3 months. During the follow-up period, 30 participants showed symptomatology compatible with COVID-19, but only four were laboratory-confirmed and they showed mild clinical signs.

Conclusion

These findings indicate that the booster doses used were safe and promoted an immediate increase in immunogenicity, which decreased over time. The heterologous regimen showed stronger immunogenicity compared to the messenger RNA-based homologous scheme.

Food-sensitized pediatric patients show colonic cow's milk protein-specific Th2 cells

Food allergies have become a health concern worldwide. Around 6% to 10% of children are allergic to cow's milk proteins. We have previously characterized colorectal polyps in patients sensitized to food allergens. These polyps are classified as inflammatory and present a type 2 environment, with elevated interleukin (IL)-13 and IL-4, and are a site of immunoglobulin E synthesis. In this study, we characterized and isolated cow's milk protein-specific T cell lines and T cell clones from the lamina propria of polyps from patients sensitized to these proteins. Isolated T cells responded to cow's milk proteins similarly to peripheral blood T cells, showing antigen-specific cell proliferation and Th2 cytokines release in vitro. T cell clones obtained were all CD4+ T cells and expressed the membrane TCRαβ receptor and secreted higher IL-4, IL-5, and IL-13 amounts than unstimulated cells, whereas interferon γ secretion remained unchanged. Remarkably, the gut homing chemokine receptor CCR9 was augmented in cow's milk-specific peripheral and lamina propria T cells, and CCL25 was found to be expressed in the inflammatory polyp tissue and not in the adjacent mucosa. In conclusion, we isolated and characterized cow's milk-specific lamina propria CD4+ Th2 cells from colonic inflammatory polyps. CCR9 expression on these cells, along with increase secretion of CCL25 in the polyp, favors recruitment and cow's milk-specific allergic response within the inflammatory polyp tissue. Our findings may be critical to understand the underlying mechanism that promotes immunoglobulin E synthesis in the colon of cow's milk proteins allergic patients, contributing to the development of novel T cell-targeted immunotherapies.

Case report: De novo SAMD9L truncation causes neonatal-onset autoinflammatory syndrome which was successfully treated with hematopoietic stem cell transplantation

During recent years, the identification of monogenic mutations that cause sterile inflammation has expanded the spectrum of autoinflammatory diseases, clinical disorders characterized by uncontrolled systemic and organ-specific inflammation that, in some cases, can mirror infectious conditions. Early studies support the concept of innate immune dysregulation with a predominance of myeloid effector cell dysregulation, particularly neutrophils and macrophages, in causing tissue inflammation. However, recent discoveries have shown a complex overlap of features of autoinflammation and/or immunodeficiency contributing to severe disease phenotypes. Here, we describe the first Argentine patient with a newly described frameshift mutation in SAMD9L c.2666delT/p.F889Sfs*2 presenting with a complex phenotypic overlap of CANDLE-like features and severe infection-induced cytopenia and immunodeficiency. The patient underwent a fully matched unrelated HSCT and has since been in inflammatory remission 5 years post-HSCT.

Type-2 Cytokines Promote the Secretion of the Eosinophil–Attractant CCL26 by Intestinal Epithelial Cells in Food-Sensitized Patients

Several inflammatory processes of the bowel are characterized by an accumulation of eosinophils at inflammation sites. The mechanisms that govern mucosal infiltration with eosinophils are not fully understood. In this work, we studied the colorectal polyp-confined tissue containing eosinophils and we hypothesized that intestinal epithelial cells are the cell source of eotaxin-3 or CCL26, a potent chemoattractant for eosinophils. We analyzed colorectal polyps (n=50) from pediatric patients with rectal bleeding by H&E staining and eosin staining, and different pro-inflammatory cytokines were assessed by RT-qPCR and ELISA. IgE and CCL26 were investigated by RT-qPCR, ELISA and confocal microscopy. Finally, the intracellular signaling pathway that mediates the CCL26 production was analyzed using a kinase array and immunoblotting in human intestinal Caco-2 cell line. We found a dense cell agglomeration within the polyps, with a significantly higher frequency of eosinophils than in control adjacent tissue. IL-4 and IL-13 were significantly up-regulated in polyps and CCL26 was elevated in the epithelial compartment. Experiments with Caco-2 cells showed that the type-2 cytokine IL-13 increased STAT3 and STAT6 phosphorylation and eotaxin-3 secretion. The addition of the blocking antibody Dupilumab or the inhibitor Ruxolitinib to the cytokine-stimulated Caco-2 cells diminished the CCL26 secretion to basal levels in a dose-dependent manner. In conclusion, our findings demonstrate a high frequency of eosinophils, and elevated levels of type-2 cytokines and eotaxin-3 in the inflammatory stroma of colorectal polyps from pediatric patients. Polyp epithelial cells showed to be the main cell source of CCL26, and IL-13 was the main trigger of this chemokine through the activation of the STAT3/STAT6/JAK1-2 pathway. We suggest that the epithelial compartment actively participates in the recruitment of eosinophils to the colonic polyp-confined inflammatory environment.

Sublingual Omp16-driven redirection of the allergic intestinal response in a pre-clinical model of food allergy

BACKGROUND

IgE-mediated food allergy remains a significant and growing worldwide problem. Sublingual immunotherapy (SLIT) shows an excellent safety profile for food allergy, but the clinical efficacy needs to be improved. This study assessed the effects of the Toll-like receptor 4 agonist outer membrane protein (Omp) 16 from Brucella abortus combined with cow´s milk proteins (CMP) through the sublingual route to modulate cow's milk allergy in an experimental model.

METHODS

Mice sensitized with cholera toxin and CMP were orally challenged with the allergen to elicit hypersensitivity reactions. Then, mice were treated with a very low amount of CMP along with Omp16 as a mucosal adjuvant, and finally, animals were re-exposed to CMP. Systemic and mucosal immune parameters were assessed in vivo and in vitro.

RESULTS

We found that the sublingual administration of Omp16 + CMP induced a buccal Th1 immune response that modulated the intestinal allergic response with the suppression of symptoms, reduction of IgE and IL-5, and up-regulation of IgG2a and IFN-γ. The adoptive transfer of submandibular IFN-γ-producing α4β7⁺ CD4⁺ and CD8⁺ cells conferred protection against allergic sensitization. The use of Omp16 + CMP promoted enhanced protection compared to CMP alone.

CONCLUSION

In conclusion, Omp16 represents a promising mucosal adjuvant that can be used to improve the clinical and immune efficacy of SLIT for food allergy.

Contribution of Non-immune Cells to Activation and Modulation of the Intestinal Inflammation

The mucosal immune system constitutes a physical and dynamic barrier against foreign antigens and pathogens and exerts control mechanisms to maintain intestinal tolerance to the microbiota and food antigens. Chronic alterations of the intestinal homeostasis predispose to inflammatory diseases of the gastrointestinal tract, such as Inflammatory Bowel Diseases (IBD). There is growing evidence that the frequency and severity of these diseases are increasing worldwide, which may be probably due to changes in environmental factors. Several stromal and immune cells are involved in this delicate equilibrium that dictates homeostasis. In this review we aimed to summarize the role of epithelial cells and fibroblasts in the induction of mucosal inflammation in the context of IBD. It has been extensively described that environmental factors are key players in this process, and the microbiome of the gastrointestinal tract is currently being intensively investigated due to its profound impact the immune response. Recent findings have demonstrated the interplay between dietary and environmental components, the gut microbiome, and immune cells. "Western" dietary patterns, such as high caloric diets, and pollution can induce alterations in the gut microbiome that in turn affect the intestinal and systemic homeostasis. Here we summarize current knowledge on the influence of dietary components and air particulate matters on gut microbiome composition, and the impact on stromal and immune cells, with a particular focus on promoting local inflammation.

Identification of cross-reactive B-cell epitopes between Bos d 9.0101(Bos Taurus) and Gly m 5.0101 (Glycine max) by epitope mapping MALDI-TOF MS

Exposure to cow's milk constitutes one of the most common causes of food allergy. In addition, exposure to soy proteins has become relevant in a restricted proportion of milk allergic pediatric patients treated with soy formulae as a dairy substitute, because of the cross-allergenicity described between soy and milk proteins. We have previously identified several cross-reactive allergens between milk and soy that may explain this intolerance. The purpose of the present work was to identify epitopes in the purified αS1-casein and the recombinant soy allergen Gly m 5.0101 (Gly m 5) using an α-casein-specific monoclonal antibody (1D5 mAb) through two different approaches for epitope mapping, to understand cross-reactivity between milk and soy. The 1D5 mAb was immobilized onto magnetic beads, incubated with the peptide mixture previously obtained by enzymatic digestion of the allergens, and the captured peptides were identified by MALDI-TOF MS analysis. On a second approach, the peptide mixture was resolved by RP-HPLC and immunodominant peptides were identified by dot blot with the mAb. Finally, recognized peptides were sequenced by MALDI-TOF MS. This novel MS based approach led us to identify and characterize four peptides on α-casein and three peptides on Gly m 5 with a common core motif. Information obtained from these cross-reactive epitopes allows us to gain valuable insight into the molecular mechanisms of cross-reactivity, to further develop new and more effective vaccines for food allergy.

The Major Soybean Allergen Gly m Bd 28K Induces Hypersensitivity Reactions in Mice Sensitized to Cow's Milk Proteins

Reactions to soy have been reported in a proportion of patients with IgE-mediated cow's milk allergy (CMA). In this work, we analyzed if Gly m Bd 28K/P28, one of the major soybean allergens, is a cross-reactive allergen with cow milk proteins (CMP). We showed that P28 was recognized by IgE sera from CMA patients and activated human peripheral basophils degranulation. Moreover, IgE sera of mice exclusively sensitized to CMP recognized P28. Splenocytes from sensitized animals secreted IL-5 and IL-13 when incubated with CMP or soy proteins, but only IL-13 when treated with P28. In addition, a skin test was strongly positive for CMP and weakly positive for P28. Remarkably, milk-sensitized mice showed hypersensitivity symptoms following sublingual challenge with P28 or CMP. With the use of bioinformatics' tools seven putative cross-reactive epitopes were identified. In conclusion, using in vitro and in vivo tests we demonstrated that P28 is a novel cross-reactive allergen with CMP.

Oral delivery of Brucella spp. recombinant protein U-Omp16 abrogates the IgE-mediated milk allergy

Food allergies are increasingly common disorders and no therapeutic strategies are yet approved. The unlipidated Omp16 (U-Omp16) is the outer membrane protein of 16 kDa from B. abortus and possesses a mucosal adjuvant property. In this study, we aimed to examine the U-Omp16 capacity to abrogate an allergen-specific Th2 immune response when it is administered as an oral adjuvant in a mouse model of food allergy.   Balb/c mice were sensitized with cholera toxin and cow's milk proteins (CMP) by gavage and simultaneously treated with U-Omp16 and CMP. Oral challenge with CMP was performed to evaluate the allergic status of mice. Symptoms, local (small bowel cytokine and transcription factor gene expression) and systemic (specific isotypes and spleen cell-secreted cytokines) parameters, and skin tests were done to evaluate the immune response. We found that the oral administration of U-Omp16 with CMP during sensitization dampened the allergic symptoms, with negativization of immediate skin test and increased skin DTH response. Serum specific IgE and IL-5 were inhibited and a Th1 response was promoted (specific IgG2a antibodies and CMP-induced IFN-γ secretion). We found at the mucosal site an inhibition of the gene expression corresponding to IL-13 and Gata-3, with an induction of IFN-γ and T-bet. These results indicated that the oral administration of U-Omp16 significantly controlled the allergic response in sensitized mice with a shift of the balance of Th1- and Th2-T cells toward Th1 predominance. These findings suggest that U-Omp16 may be useful as a Th1-directing adjuvant in an oral vaccine.

Orally-Induced Intestinal CD4+ CD25+ FoxP3+ Treg Controlled Undesired Responses towards Oral Antigens and Effectively Dampened Food Allergic Reactions

The induction of peripheral tolerance may constitute a disease-modifying treatment for allergic patients. We studied how oral immunotherapy (OIT) with milk proteins controlled allergy in sensitized mice (cholera toxin plus milk proteins) upon exposure to the allergen. Symptoms were alleviated, skin test was negativized, serum specific IgE and IgG1 were abrogated, a substantial reduction in the secretion of IL-5 and IL-13 by antigen-stimulated spleen cells was observed, while IL-13 gene expression in jejunum was down-regulated, and IL-10 and TGF-β were increased. In addition, we observed an induction of CD4⁺CD25⁺FoxP3⁺ cells and IL-10- and TGF-β-producing regulatory T cells in the lamina propria. Finally, transfer experiments confirmed the central role of these cells in tolerance induction. We demonstrated that the oral administration of milk proteins pre- or post-sensitization controlled the Th2-immune response through the elicitation of mucosal IL-10- and TGF-β-producing Tregs that inhibited hypersensitivity symptoms and the allergic response.

Cross-reactivity between the soybean protein p34 and bovine caseins

Purpose

Soy-based formulas are widely used as dairy substitutes to treat milk allergy patients. However, reactions to soy have been reported in a small proportion of patients with IgE-mediated milk allergies. The aim of this work was to explore whether P34, a mayor soybean allergen, is involved in this cross-reactivity.

Methods

In vitro recognition of P34 was evaluated by immunoblotting, competitive ELISA and basophil activation tests (BAT) using sera from allergic patients. In vivo cross-reactivity was examined using an IgE-mediated milk allergy mouse model.

Results

P34 was recognized by IgE antibodies from the sera of milk allergic patients, casein-specific monoclonal antibodies, and sera from milk-allergic mice. Spleen cells from sensitized mice incubated with milk, soy or P34 secreted IL-5 and IL-13, while IFN-γ remained unchanged. In addition, the cutaneous test was positive with cow's milk proteins (CMP) and P34 in the milk allergy mouse model. Moreover, milk-sensitized mice developed immediate symptoms following sublingual exposure to P34.

Conclusions

Our results demonstrate that P34 shares epitopes with bovine casein, which is responsible for inducing hypersensitivity symptoms in milk allergic mice. This is the first report of the in vivo cross-allergenicity of P34.

Immunological status of isolated lymphoid follicles after intestinal transplantation

Intestinal transplantation (ITx) faces the challenge of grafting a high immunogenic organ, which is certainly one of the major obstacles for intestinal allograft acceptance. The allograft has to guarantee the proper functioning of the mucosal immune machinery under immunosuppressive conditions. Recently, it has been elucidated that isolated lymphoid follicles (ILFs) are an indispensable part of mucosal immunity to maintain IgA synthesis and consequently to control commensal microflora. No data about these follicular structures in the setting of ITx are available so far. Therefore, we addressed the question whether constitution, integrity and function of allograft ILFs are disturbed by immunosuppressive regimen. We compared allograft ILFs from terminal ileum of transplant patients with ILFs from nontransplant patients via flow cytometry, quantitative real-time polymerase chain reaction and immunohistochemistry. We found that host leukocytes rapidly repopulate allograft ILFs and that maintenance immunosuppressive regimen, tacrolimus and corticosteroids, does not affect their cellular integrity and function. However, allograft ILFs revealed a higher maturation state than control samples and IgA positive plasma cells were increased in number in allograft mucosa. Our results open the path for a better understanding of allograft mucosal immunity.

Duodenal intraepithelial lymphocytes of children with cow milk allergy preferentially bind the glycan-binding protein galectin-3

A breakdown in intestinal homeostasis results in inflammatory bowel diseases including coeliac disease and allergy. Galectins, evolutionarily conserved beta-galactoside-binding proteins, can modulate immune-epithelial cell interactions by influencing immune cell fate and cytokine secretion. In this study we investigated the glycosylation signature, as well as the regulated expression of galectin-1 and -3 in human duodenal samples of allergic and non-allergic children. Whereas galectin-1 was predominantly localized in the epithelial compartment (epithelial cells and intraepithelial lymphocytes) and the underlying lamina propria (T cells, macrophages and plasma cells), galectin-3 was mainly expressed by crypt epithelial cells and macrophages in the lamina propria. Remarkably, expression of these galectins was not significantly altered in allergic versus non-allergic patients. Investigation of the glycophenotype of the duodenal inflammatory microenvironment revealed substantial alpha2-6-linked sialic acid bound to galactose in lamina propria plasma cells, macrophages and intraepithelial lymphocytes and significant levels of asialo core 1 O-glycans in CD68+ macrophages and enterocytes. Galectin-1 preferentially bound to neutrophils, plasma cells and enterocytes, while galectin-3 binding sites were mainly distributed on macrophages and intraepithelial lymphocytes. Notably, galectin-3, but not galectin-1 binding, was substantially increased in intraepithelial gut lymphocytes of allergic patients compared to non-allergic subjects, suggesting a potential role of galectin-3-glycan interactions in shaping epithelial-immune cell connections during allergic inflammatory processes.

Immunochemical characterization of Glycine max L. Merr. var Raiden, as a possible hypoallergenic substitute for cow's milk-allergic patients

BACKGROUND

Cows' milk allergy (CMA) is the most common cause of food allergy in infancy. The only proven treatment is the complete elimination of cows' milk proteins (CMPs) from the diet by means of hypoallergenic formulas. Soybean-based formulae are widely used although intolerance to soy has been reported to occur in 15-40% of infants with CMA.

OBJECTIVE

The aim of this work was to analyse the in vitro reactivity of the soybean cultivar Raiden, which naturally lacks glycinin A(4)A(5)B(3), to evaluate whether this genotype could be a safe CMP substitute for CMA patients.

METHODS

The reactivity of conventional soybean (CS) and Raiden soybean (RS) genotypes and also recombinant glycinin A(4)A(5)B(3) and alphabeta-conglycinin with casein-specific monoclonal antibodies and CMP-specific polyclonal serum was evaluated by immunoblotting and ELISA. A sequential competitive ELISA with the polyclonal antiserum and different soluble inhibitors was performed. In addition, an indirect ELISA with sera of atopic children with CMA was carried out to analyse the IgE-binding capacity of the different soybean components.

RESULTS

We have shown that CS contains four components that cross-react with CMP, while RS has only one. The remaining cross-reactive component in RS was identified as alpha-subunit beta-conglycinin. By means of inhibitory ELISA, we demonstrated that CS, RS and the alpha-subunit beta-conglycinin extracts inhibited the binding of CMP-specific antibodies to the CMP-coated solid phase. Finally, we showed that CS, RS and the recombinant proteins were recognized by human CMP-specific IgE antibodies.

CONCLUSION

This work shows that although Raiden has fewer cross-reactive components than conventional soybean, it still has a residual cross-reactive component: the alpha-subunit beta-conglycinin. This reactivity might make this genotype unsuitable to treat CMA and also explains adverse reactions to soybean in CMA infants.

Serological prevalence of anti-latex IgE antibodies in unselected blood donors in Argentina

The prevalence of specific IgE to natural rubber latex proteins in the general population remains uncertain. The purpose of this study was to determine the prevalence of sera containing specific IgE antibodies to latex proteins using immunoenzymatic methods. A population of 500 unselected adult voluntary blood donors was the source of the sera used in this study. Two different immunoenzymatic methods (EAST and CARLA) were used to analyze the presence of specific IgE antibodies. Confirmation assay was carried out by inhibition ELISA and immunoblotting. Sera from healthy nonatopic individuals were also used as control. Two hundred and twenty five sera showed higher than normal total IgE levels. Of those, three presented latex specific IgE antibodies, which could be inhibited in a dose-response manner with the natural rubber latex and glove extracts. Several latex allergens were recognized by the IgE antibodies from these positive sera. This low seroprevalence (0.66%) indicates that latex hypersensitivity is not an important problem in the general population. We believe that prevention of latex exposure is only necessary in high risk groups of patients.

Detection and identification of a soy protein component that cross-reacts with caseins from cow's milk

Soy-based formulas are the most employed cow's milk substitutes in the treatment of cow's milk allergy in our country. Since adverse reactions have been reported in allergic patients as a consequence of exposure to soy proteins, we have investigated the possible cross-reactivity between components from soybean and cow's milk. A cow's milk specific polyclonal antiserum and casein specific monoclonal antibodies were used in immunoblotting and competitive ELISA studies to identify a 30-kD component from soybean that cross-reacts with cow's milk caseins. Its IgE binding capacity was tested by EAST, employing sera from cow's milk allergic patients, not previously exposed to soy proteins. The 30 kD protein was isolated and partially sequenced. It is constituted by two polypeptides (A5 and B3) linked by a disulphide bond. The protein's capacity to bind to the different antibodies relies on the B3 poly-peptide. These results indicate that soy-based formula, which contains the A5-B3 glycinin molecule, could be involved in allergic reactions observed in cow's milk allergic patients exposed to soy-containing foods.

Identification of allergenic proteins in condoms by immunoenzymatic methods

BACKGROUND

A large increase of allergy to latex proteins has been observed lately probably as a result of a great use of latex-containing goods. At present these untoward reactions have led to consideration of this problem as a health and occupational hazard. It is therefore, necessary to identify the allergens contained in latex-manufactured products and to develop effective diagnostic tools to detect sensitized individuals.

OBJECTIVE

The objective of this study is to identify antigenic and allergenic components in latex condoms by using chemical, immunochemical, and immunoenzymatic methods.

METHODS

The protein content of extracts obtained from several brands of condoms was determined and characterized by using a modified Lowry method, a quantitative ELISA assay and SDS-PAGE. The allergenic behavior of these proteins was studied by IgE immunoblotting, EAST and ELISA techniques, using sera from subjects allergic to latex products, particularly to latex condoms.

RESULTS

Wide variations in the protein content (38 to 740 microg/g product) and composition were observed. The SDS-PAGE protein profiles showed components ranging from 7 to 94 kD of relative molecular weights; most of them were also detected in natural rubber latex. The most prominent bands were revealed in the 14 and 30 kD zones. A strong band of 69 kD in the SDS-PAGE profiles would correspond to a neoantigen, since it was not observed in natural latex. The immunoblotting analysis employing sera from 5 patients allergic to latex condoms showed the presence of 4 components with IgE binding capacity (14, 30, 69, and 94 kD). The EAST and ELISA methods showed the presence of allergens in all the condom brands studied.

CONCLUSIONS

The presence of allergenic proteins in several condom brands was demonstrated by different immunoenzymatic methods.

Detection of allergens in Aedes albifasciatus mosquito (Diptera: Culicidae) extracts by immunological methods

Aedes albifasciatus (Diptera: Culicidae) is the most common mosquito species in Argentina and it has been demonstrated to be the vector for some pathogens. The objective of this study was to describe the allergen composition of this mosquito species endemic to Argentina using SDS-PAGE and immunoblotting methods. Sera from mosquito-bite allergic subjects were employed. The protein extracts, obtained from thoraxes containing salivary glands, showed a protein pattern with components of apparent molecular weights ranging from 14 to over 94 kDa. Some of the components could bind IgE in the 16, 20, 30, 36 and 50-67 kDa-zones, whereas the 14 kDa fraction detectable by SDS-PAGE did not behave as an allergen with any positive serum. This protein extract was used to develop in vitro assays to detect the presence of serum-specific IgE against proteins from A. albifasciatus (RAST and ELISA). Thirty-five sera from patients showing local reactions after mosquito bites were tested. The 21 positive sera were from subjects with clinical histories of atopic signs. Through immunoblotting, these sera revealed IgE reactivity against several fractions, mainly in the 16, 20, 30, 36 and 50-67 kDa zones. Comparing the serum IgE reactivity pattern against A. albifasciatus and Aedes aegypti, we observed that the main difference was found in the 14 kDa region where a strong reactivity was seen. The immunoblotting inhibition results indicate that there might be species-unique and species-shared antigens between A. albifasciatus and A. aegypti.

Serological investigation of latex allergy in Argentina

Atopy to latex has been reported in different high-risk groups of subjects in whom it is mainly caused by proteins from natural latex that are responsible for eliciting a variety of clinical symptoms, some of them systemic. Thus, identification of subjects sensitized to latex proteins is of great health importance, because it would become possible to advise them to avoid contact with latex-containing products. Protein extracts from ammoniated latex were prepared by incubation with PBS buffer either with or without detergents, followed by ultracentrifugation. Three immunoenzymic methods were developed (EAST, ELISA, and immunoblotting) to detect the presence of specific IgE antibodies against latex proteins in sera of patients from different groups at risk. The protein content of the latex extracts ranged from 5.3 to 8.8 mg/mL. The prevalence of specific IgE against latex proteins was 9/28 (32.1%) in children with multiple surgeries, 17/98 (17.3%) in health care workers, and 23/123 (18.6%) in outpatients assisted at the Allergy Department. None of the sera belonging to the healthy control group showed the presence of specific IgE. Therefore, this protein extract from latex could be used to detect specific IgE antibodies in serum by immunoenzymic methods. Serologic results for latex-specific IgE found are in accordance with those reported in the literature of other countries.

Identification of casein as the major allergenic and antigenic protein of cow's milk

The objective of this study was to analyze both the allergenicity and immunogenicity of cow's milk proteins. To this end, 80 milk-atopic patients were selected on the basis of the presence of cow's milk-specific IgE antibodies in serum and compatible clinical history. Fifteen patients allergic to other allergens and 10 nonatopic subjects were studied as controls. The specificity of serum IgG and IgE antibodies was determined by immunoblotting, employing both cow's milk and milk components, i.e., alpha- and beta-casein, beta-lactoglobulin, and alpha-lactalbumin separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The experiments showed that casein-specific IgE antibodies were present in all (80/80) sera examined; 10/80 showed reactivity to beta-lactoglobulin, and 5/80 showed reactivity to alpha-lactalbumin. None of the 25 negative control sera analyzed showed the presence of specific IgE antibodies against milk proteins. These results were similar to those corresponding to the detection, by the radioallergosorbent test, of IgE antibodies against the milk components coupled to paper disks. All sera from milk-atopic patients also showed IgE reactivity against a high-molecular-mass fraction that hardly enters the gel. This fraction, after separation by gel filtration and treatment with beta-mercaptoethanol and urea, was shown by SDS-PAGE analysis to be formed by casein monomers. All sera analyzed by immunoblotting reacted against the components corresponding to casein monomers. Inhibition of immunoblotting by adsorption with different milk components confirmed that those high-molecular-mass aggregates are formed by casein components. The results presented here strongly suggest that casein is the major allergenic component of cow's milk.