Susceptibility of Sea Bream (Sparus aurata) to AIP56, an AB-Type Toxin Secreted by Photobacterium damselae subsp. piscicida

Photobacterium damselae subsp. piscicida (Phdp) is a Gram-negative bacterium that infects a large number of marine fish species in Europe, Asia, and America, both in aquacultures and in the natural environment. Among the affected hosts are economically important cultured fish, such as sea bream (Sparus aurata), sea bass (Dicentrarchus labrax), yellowtail (Seriola quinqueradiata), and cobia (Rachycentron canadum). The best characterized virulence factor of Phdp is the Apoptosis-Inducing Protein of 56 kDa (AIP56), a secreted AB-type toxin that has been shown to induce apoptosis of sea bass phagocytes during infection. AIP56 has an A subunit that displays metalloprotease activity against NF-kB p65 and a B subunit that mediates binding and internalization of the A subunit in susceptible cells. Despite the fact that the aip56 gene is highly prevalent in Phdp isolates from different fish species, the toxicity of AIP56 has only been studied in sea bass. In the present study, the toxicity of AIP56 for sea bream was evaluated. Ex vivo assays showed that sea bream phagocytes are resistant to AIP56 cytotoxicity and that resistance was associated with an inefficient internalization of the toxin by those cells. Accordingly, in vivo intoxication assays revealed that sea bream is much more resistant to AIP56-induced lethality than sea bass. These findings, showing that the effect of AIP56 is different in sea bass and sea bream, set the basis for future studies to characterize the effects of AIP56 and to fully elucidate its virulence role in different Phdp susceptible hosts.

A study of commercially available complementary foods for infants and young children under 36 months

Background

Commercially available complementary foods (CACFs) have been assuming an important proportion of infants and toddlers' diets in high-income countries, despite the concerns regarding their nutritional content and potential problematic marketing strategies used to promote these products. In 2016, the WHO guidance on ending the inappropriate promotion of foods for infants and young children (IYC) was approved (1) to support countries to take action on this issue. To implement this Guidance, a draft Nutrient Profile Model (NPM) (2) was developed to drive decisions regarding the identification of foods which are inappropriate for promotion.

Aim

To support the implementation of the NPM at National Level, studying the availability, composition, and marketing of CACFs for IYC in Portugal.

Methods

Three phases were considered: 1) collect data on CACFs products targeted at IYC (0-36 months); 2) compare composition of these products with WHO guidance; 3) compare methods used to promote these products with WHO Guidance.

Results

A total of 209 products were sampled. The most common products were soft-wet spoonable, ready-to-eat foods (n = 129), dry, powdered and instant cereal/starchy foods (n = 61) and dry finger foods and snacks (n = 16). Twenty-five products (11%) were marketed as being suitable for infants under the age of 6 months. For infants between 6-8 months 78% of the products were marketed as being suitable. For the age group 12 months and over, 11% of the products were marketed as being suitable.

Conclusions

This study provides valuable insights into the CACFs at the national level and reinforces that action is needed to improve the implementation and operationalization of WHO guidance on ending the inappropriate promotion of foods for IYC.

Key messages

NPM can support countries identifying products that can/cannot be promoted for IYC. It is a key opportunity to build policy measures, ensuring children healthy growth and development.

Trends in breastfeeding rates in Portugal: results from five National Health Interview Surveys

Background

The World Health Organization advice breast milk as the perfect food for the newborn starting immediately after birth and exclusively up to at least 6 months of age. However, there are considerable differences in breastfeeding rates between countries related to their policies on breastfeeding promotion and duration of maternity leave. This study aims to describe changes in breastfeeding rates over time in Portugal as a way to inform social policies and public health initiatives on breastfeeding.

Methods

To examine the breastfeeding rates evolution we used data from five National Health Surveys. Breastfeeding was assessed based on information provided by the mothers of children born between 1982 and 2014. Birth cohorts were grouped in block of 3-year period. We estimated 3 and 6-months exclusive breastfeeding rates and 95% confidence intervals. Trends in breastfeeding rates for each outcome were assessed by linear regression weighting each cohort-specific estimate by the inverse of variance in the logit scale.

Results

We analyzed data on 9172 children; sample size by birth cohort ranged from 213 in 2012/14 to 1651 in 1994/96. Proportion of infants ever breastfed during the study period varied between 71.7% and 86.7%. The 3 months exclusive breastfeeding rate increased by 9.5% (CI95%:7.8-11.3%) per 3-year period, from 41.3% (CI95%:38.7-43.9%) in 1982/84 to 62.4% (CI95%:55.7-68.7%) in 2012/14. The 6 months exclusive breastfeeding rate raised up from 23.5% (CI 95%:21.2-25.7%) in 1982/84 to 31.9% (CI95%:26.0-38.5%) in 2012/14, corresponding to 5.6% increase per 3-year period.

Conclusions

This study shows a positive evolution in breastfeeding practices, with an increased in the prevalence of women who reported exclusively breastfeeding until the 3rd and 6th month after birth. Our results may be explained by changes in maternity leave duration. Furthermore, the results emphasize the need for further investment in breastfeeding support services and professionalś training.

Key messages

Positive evolution in breastfeeding practices in Portugal. Maternity leave duration could have a positive role.

Health Literacy in Diabetes management: A priority in health care

Background

Glycemic control and self-management of diabetes are influenced by a range of factors, including health literacy - the ability to access, understand, appraise, and use health information. This study explored associations between domains of health literacy (HL), glycemic control and perceived general health in people with diabetes.

Methodology

Cross-sectional study, with 453 people with diabetes,attending the Portuguese Diabetes Association (APDP). We collected information on HL, demographics, glycemic control and self-perception of health. HL was assessed using the Health Literacy Questionnaire. Descriptive and correlational analysis were performed.

Results

85.4% consider Feeling understood and supported by healthcare providers but only 54.1% have the Ability to actively engage with healthcare providers and 27.8% feel the Ability to find good health information,66.5% consider Having sufficient information to manage my health but only 38.7% are Understanding health information well enough to know what to do and 28.5% refer the Ability to find good health information. Higher HL scores were associated with better glycemic control and more positive perception of general health(GH) across the following domains: Having sufficient information to manage my health, Appraisal of health information, Ability to find good health information, Actively managing my health and social support for health. The domains Ability to actively engage with healthcare providers and Navigating the healthcare system were also associated with more positive perception of GH. Associations achieved either p < 0.001 or p < 0.05. Considering HL levels, a statistically significant negative association was found with the levels of HbA1c and positive association with perceived general health, even for functional HL.

Conclusions

The results emphasize the importance of improving the level of HL of people with diabetes in order to improve glycemic control and the perceive General Health

Key messages

Health literacy is critical for diabetes self-management. People with diabetes need to understand and use health information to promote well-being and diabetes control.

Baby foods available in the Portuguese marketplace and the application of nutrient profile models

Background

An investment in nutrition at the earliest possible stage, providing appropriate complementary feeding, is critical to ensure proper growth and to prevent noncommunicable diseases (NCDs). Food and drinks high in fats, free sugars and salt are being marketed for consumption by young children and represent particular concern.

Aim

This study aims to determine the compliance of complementary foods (CACFs) for infants and young children sold in the Portuguese marketplace according to WHO draft Nutrient Profile model (NPM) for infants and young children between 6 and 36 months (1).

Methods

A sample of 128 CACFs was collected. Using nutritional food label information, products were divided into four food categories: dry, powdered and instant cereals; dry finger foods and snacks; meals with chunky pieces; and soft-wet spoonable, ready-to-eat foods. Packaging information was used to determine sodium, fat and sugar content per 100 g and percentage energy from total sugar by food category.

Results

Twenty-eight products (22%) comply with all the criteria established in the NPM. All the evaluated dry, powdered, and instant cereals, dry finger foods and snacks and meals with chunky pieces (n = 55) comply with recommendations proposed for total fat (≤4.5 g/100 kcal). Analysis of energy contribution from total sugars reveals 9 % (n = 5) of dry finger foods and snacks comply with the proposed criteria < 15% total energy from total sugars. The 73 soft-wet spoonable, ready-to-eat foods assessed, 74 % (n = 54) comply with the sodium thresholds of 50 mg/100 kcal, 64 % (n = 47) had a content ≥ 60 Kcal/100 g and 74 % (n = 54) contained over 20% of energy derived from sugar.

Conclusions

CACFs available in the Portuguese marketplace are characterised by products with high proportion of calories derived from sugar, promoting an environment that encourages development of sweet-taste preferences and adverse health outcomes resultant from the overconsumption of sugar in early life.

Key messages

There is an urgent need for updated regulations to support and guide product reformulation. A nutrient profile model for CACFs will establishes compositional thresholds and provides guidance on product-labelling and promotions.

Potential Drug Targets in the Pentose Phosphate Pathway of Trypanosomatids

The trypanosomatids, Trypanosoma brucei, Trypanosoma cruzi and Leishmania spp, are causative agents of important human diseases such as African sleeping sickness, Chagas' disease and Leishmaniasis, respectively. The high impact of these diseases on human health and economy worldwide, the unsatisfactory available chemotherapeutic options and the absence of human effective vaccines, strongly justifies the search for new drugs. The pentose phosphate pathway has been proposed to be a viable strategy to defeat several infectious diseases, including those from trypanosomatids, as it includes an oxidative branch, important in the maintenance of cell redox homeostasis, and a non-oxidative branch in which ribose 5-phosphate and erythrose 4-phosphate, precursors of nucleic acids and aromatic amino acids, are produced. This review provides an overview of the available chemotherapeutic options against these diseases and discusses the potential of genetically validated enzymes from the pentose phosphate pathway of trypanosomatids to be explored as potential drug targets.

TRSP is dispensable for the Plasmodium pre-erythrocytic phase

Plasmodium sporozoites deposited in the skin following a mosquito bite must migrate and invade blood vessels to complete their development in the liver. Once in the bloodstream, sporozoites arrest in the liver sinusoids, but the molecular determinants that mediate this specific homing are not yet genetically defined. Here we investigate the involvement of the thrombospondin-related sporozoite protein (TRSP) in this process using knockout Plasmodium berghei parasites and in vivo bioluminescence imaging in mice. Resorting to a homing assay, trsp knockout sporozoites were found to arrest in the liver similar to control parasites. Moreover, we found no defects in the establishment of infection in mice following inoculation of trsp knockout sporozoites via intravenous and cutaneous injection or mosquito bite. Accordingly, mutant sporozoites were also able to successfully invade hepatocytes in vitro. Altogether, these results suggest TRSP may have a redundant role in the completion of the pre-erythrocytic phase of the malaria parasite. Nonetheless, identifying molecules with paramount roles in this phase could aid in the search for new antigens needed for the design of a protective vaccine against malaria.

Activity of Bisnaphthalimidopropyl Derivatives against Trypanosoma brucei

Current treatments for African trypanosomiasis are either toxic, costly, difficult to administer, or prone to elicit resistance. This study evaluated the activity of bisnaphthalimidopropyl (BNIP) derivatives againstTrypanosoma brucei BNIPDiaminobutane (BNIPDabut), the most active of these compounds, showedin vitroinhibition in the single-unit nanomolar range, similar to the activity in the reference drug pentamidine, and presented low toxicity and adequate metabolic stability. Additionally, using a murine model of acute infection and live imaging, a significant decrease in parasite load in BNIPDabut-treated mice was observed. However, cure was not achieved. BNIPDabut constitutes a new scaffold for antitrypanosomal drugs that deserves further consideration.

Leishmania infantum Asparagine Synthetase A Is Dispensable for Parasites Survival and Infectivity

A growing interest in asparagine (Asn) metabolism has currently been observed in cancer and infection fields. Asparagine synthetase (AS) is responsible for the conversion of aspartate into Asn in an ATP-dependent manner, using ammonia or glutamine as a nitrogen source. There are two structurally distinct AS: the strictly ammonia dependent, type A, and the type B, which preferably uses glutamine. Absent in humans and present in trypanosomatids, AS-A was worthy of exploring as a potential drug target candidate. Appealingly, it was reported that AS-A was essential in Leishmania donovani, making it a promising drug target. In the work herein we demonstrate that Leishmania infantum AS-A, similarly to Trypanosoma spp. and L. donovani, is able to use both ammonia and glutamine as nitrogen donors. Moreover, we have successfully generated LiASA null mutants by targeted gene replacement in L. infantum, and these parasites do not display any significant growth or infectivity defect. Indeed, a severe impairment of in vitro growth was only observed when null mutants were cultured in asparagine limiting conditions. Altogether our results demonstrate that despite being important under asparagine limitation, LiAS-A is not essential for parasite survival, growth or infectivity in normal in vitro and in vivo conditions. Therefore we exclude AS-A as a suitable drug target against L. infantum parasites.

Ribose 5-phosphate isomerase B knockdown compromises Trypanosoma brucei bloodstream form infectivity

Ribose 5-phosphate isomerase is an enzyme involved in the non-oxidative branch of the pentose phosphate pathway, and catalyzes the inter-conversion of D-ribose 5-phosphate and D-ribulose 5-phosphate. Trypanosomatids, including the agent of African sleeping sickness namely Trypanosoma brucei, have a type B ribose-5-phosphate isomerase. This enzyme is absent from humans, which have a structurally unrelated ribose 5-phosphate isomerase type A, and therefore has been proposed as an attractive drug target waiting further characterization. In this study, Trypanosoma brucei ribose 5-phosphate isomerase B showed in vitro isomerase activity. RNAi against this enzyme reduced parasites' in vitro growth, and more importantly, bloodstream forms infectivity. Mice infected with induced RNAi clones exhibited lower parasitaemia and a prolonged survival compared to control mice. Phenotypic reversion was achieved by complementing induced RNAi clones with an ectopic copy of Trypanosoma cruzi gene. Our results present the first functional characterization of Trypanosoma brucei ribose 5-phosphate isomerase B, and show the relevance of an enzyme belonging to the non-oxidative branch of the pentose phosphate pathway in the context of Trypanosoma brucei infection.

Within the non-oxidative branch of the pentose phosphate pathway, ribose 5-phosphate isomerase catalyzes the inter-conversion of ribose 5-phosphate and ribulose 5-phosphate. There are two types of ribose 5-phosphate isomerase, namely A and B. The presence of type B in Trypanosoma brucei, and its absence in humans, make this protein a promising drug target. African sleeping sickness is a serious parasitic disease that relies on limited chemotherapeutic options for control. In our study, a functional characterization of Trypanosoma brucei ribose 5-phosphate isomerase B is reported. Biochemical studies confirmed enzyme isomerase activity and its downregulation by RNAi affected mainly parasites infectivity in vivo. Overall this study shows that ribose 5-phosphate isomerase depletion is detrimental for parasites infectivity under host pressure.

Knockdown of asparagine synthetase A renders Trypanosoma brucei auxotrophic to asparagine

Asparagine synthetase (AS) catalyzes the ATP-dependent conversion of aspartate into asparagine using ammonia or glutamine as nitrogen source. There are two distinct types of AS, asparagine synthetase A (AS-A), known as strictly ammonia-dependent, and asparagine synthetase B (AS-B), which can use either ammonia or glutamine. The absence of AS-A in humans, and its presence in trypanosomes, suggested AS-A as a potential drug target that deserved further investigation. We report the presence of functional AS-A in Trypanosoma cruzi (TcAS-A) and Trypanosoma brucei (TbAS-A): the purified enzymes convert L-aspartate into L-asparagine in the presence of ATP, ammonia and Mg²⁺. TcAS-A and TbAS-A use preferentially ammonia as a nitrogen donor, but surprisingly, can also use glutamine, a characteristic so far never described for any AS-A. TbAS-A knockdown by RNAi didn't affect in vitro growth of bloodstream forms of the parasite. However, growth was significantly impaired when TbAS-A knockdown parasites were cultured in medium with reduced levels of asparagine. As expected, mice infections with induced and non-induced T. brucei RNAi clones were similar to those from wild-type parasites. However, when induced T. brucei RNAi clones were injected in mice undergoing asparaginase treatment, which depletes blood asparagine, the mice exhibited lower parasitemia and a prolonged survival in comparison to similarly-treated mice infected with control parasites. Our results show that TbAS-A can be important under in vivo conditions when asparagine is limiting, but is unlikely to be suitable as a drug target.

The amino acid asparagine is important not only for protein biosynthesis, but also for nitrogen homeostasis. Asparagine synthetase catalyzes the synthesis of this amino acid. There are two forms of asparagine synthetase, A and B. The presence of type A in trypanosomes, and its absence in humans, makes this protein a potential drug target. Trypanosomes are responsible for serious parasitic diseases that rely on limited drug therapeutic options for control. In our study we present a functional characterization of trypanosomes asparagine synthetase A. We describe that Trypanosoma brucei and Trypanosoma cruzi type A enzymes are able to use either ammonia or glutamine as a nitrogen donor, within the conversion of aspartate into asparagine. Furthermore, we show that asparagine synthetase A knockdown renders Trypanosoma brucei auxotrophic to asparagine. Overall, this study demonstrates that interfering with asparagine metabolism represents a way to control parasite growth and infectivity.

Impact of continuous axenic cultivation in Leishmania infantum virulence

Experimental infections with visceral Leishmania spp. are frequently performed referring to stationary parasite cultures that are comprised of a mixture of metacyclic and non-metacyclic parasites often with little regard to time of culture and metacyclic purification. This may lead to misleading or irreproducible experimental data. It is known that the maintenance of Leishmania spp. in vitro results in a progressive loss of virulence that can be reverted by passage in a mammalian host. In the present study, we aimed to characterize the loss of virulence in culture comparing the in vitro and in vivo infection and immunological profile of L. infantum stationary promastigotes submitted to successive periods of in vitro cultivation. To evaluate the effect of axenic in vitro culture in parasite virulence, we submitted L. infantum promastigotes to 4, 21 or 31 successive in vitro passages. Our results demonstrated a rapid and significant loss of parasite virulence when parasites are sustained in axenic culture. Strikingly, the parasite capacity to modulate macrophage activation decreased significantly with the augmentation of the number of in vitro passages. We validated these in vitro observations using an experimental murine model of infection. A significant correlation was found between higher parasite burdens and lower number of in vitro passages in infected Balb/c mice. Furthermore, we have demonstrated that the virulence deficit caused by successive in vitro passages results from an inadequate capacity to differentiate into amastigote forms. In conclusion, our data demonstrated that the use of parasites with distinct periods of axenic in vitro culture induce distinct infection rates and immunological responses and correlated this phenotype with a rapid loss of promastigote differentiation capacity. These results highlight the need for a standard operating protocol (SOP) when studying Leishmania species.

Protozoan of the genus Leishmania undergo several developmental transitions during its life cycle. Leishmania alternates between two morphologically distinct forms, promastigotes (insect stage) and amastigotes (vertebrate stage). Most of the available information about Leishmania spp. has been obtained from studying in vitro cultured promastigotes, an excellent experimental model for the different developmental stages present in the insect vector. Although promastigotes are grown in a controlled environment, the maintenance of long term culture results in loss of virulence, which can lead to a misinterpretation and often contradictory experimental results. It is then of great interest to unravel the defects arising from sustained axenic parasite culture in laboratory settings. The authors demonstrate a correlation between the maintenance of parasite culture with a growing defect of the promastigote form to differentiate in the mammalian amastigote form. This research provides a biological explanation for the loss of virulence due to sustained parasite culture and discusses the impact for all experimental work done with visceral Leishmania species.

Activation of phosphatidylinositol 3-kinase/Akt and impairment of nuclear factor-kappaB: molecular mechanisms behind the arrested maturation/activation state of Leishmania infantum-infected dendritic cells

Understanding the complex interactions between Leishmania and dendritic cells (DCs) is central to the modulation of the outcome of this infection, given that an effective immune response against Leishmania is dependent on the successful activation and maturation of DCs. We report here that Leishmania infantum promastigotes successfully infect mouse bone marrow-derived DCs without triggering maturation, as shown by a failure in the up-regulation of CD40 and CD86 expression, and that parasites strongly counteract the lipopolysaccharide-triggered maturation of DCs. A small increase in interleukin (IL)-12 and IL-10 transcription and secretion and a decrease in IL-6 were observed in infected cells. This arrested DC maturation state is actively promoted by parasites because heat-killed or fixed parasites increased cytokine and costimulatory molecule expression. At a molecular level, L. infantum rapidly induced activation of phosphatidylinositol 3-kinase/Akt and extracellular signal-regulated kinase 1/2, whereas no effect was observed in the c-Jun N-terminal kinase and p38 mitogen-activated protein kinase proinflammatory pathways. Moreover, parasites actively promoted cleavage of the nuclear factor-κB p65(RelA) subunit, causing its impairment. The blockade of phosphatidylinositol 3-kinase/Akt by either treatment of bone marrow-derived DCs with wortmannin or transfection with an Akt dominant-negative mutant resulted in a strong decrease in infection rates, revealing for the first time a crucial role of this pathway on Leishmania engulfment by DCs. Overall, our data indicate that activation of Akt and impairment of nuclear factor-κB are responsible for immunogenicity subversion of L. infantum-infected DCs.

Bisnaphthalimidopropyl derivatives as inhibitors of Leishmania SIR2 related protein 1

The NAD(+)-dependent deacetylases, namely sirtuins, are involved in the regulation of a variety of biological processes such as gene silencing, DNA repair, longevity, metabolism, apoptosis, and development. An enzyme from the parasite Leishmania infantum that belongs to this family, LiSIR2RP1, is a NAD(+)-dependent tubulin deacetylase and an ADP-ribosyltransferase. This enzyme's involvement in L. infantum virulence and survival underscores its potential as a drug target. Our search for selective inhibitors of LiSIR2RP1 has led, for the first time, to the identification of the antiparasitic and anticancer bisnaphthalimidopropyl (BNIP) alkyl di- and triamines (IC(50) values in the single-digit micromolar range for the most potent compounds). Structure-activity studies were conducted with 12 BNIP derivatives that differ in the length of the central alkyl chain, which links the two naphthalimidopropyl moieties. The most active and selective compound is the BNIP diaminononane (BNIPDanon), with IC(50) values of 5.7 and 97.4 microM against the parasite and human forms (SIRT1) of the enzyme, respectively. Furthermore, this compound is an NAD(+)-competitive inhibitor that interacts differently with the parasite and human enzymes, as determined by docking analysis, which might explain its selectivity toward the parasitic enzyme.

Human colostrum contains IgA antibodies reactive to enteropathogenic Escherichia coli virulence-associated proteins: intimin, BfpA, EspA, and EspB

BACKGROUND

In Brazil, enteropathogenic Escherichia coli diarrhoea is endemic among infants born into low economic levels, and it is one of the main causes of morbidity and mortality in this group. Binding of enteropathogenic E. coli to the brush border mucosa triggers a cascade of transmembrane and intracellular signals, causing cytoskeletal reorganization and formation of a specific lesion, termed the attaching and effacing lesion. Several enteropathogenic E. coli gene products have been implicated in formation of attaching and effacing lesions. Evaluation of pathogen-specific protective factors shows that breast feeding is effective against enteropathogenic E. coli infection. To investigate the nature of the protection, defatted colostrum and secretory immunoglobulin A obtained from mothers living in Sao Paulo were investigated for the ability to recognise selected enteropathogenic E. coli-associated virulence factors.

METHODS

Western blot analysis was used to investigate the IgA repertoire in pooled colostrum that is reactive with specific enteropathogenic E. coli proteins. Whole enteropathogenic E. coli bacterial cell extracts, nonpathogenic E. coli strains overexpressing specific virulence factors, and purified polypeptides were used as antigen sources in this study.

RESULTS

Reaction of the colostrum samples in Western blots of whole bacterial cell extracts and selected purified enteropathogenic E. coli proteins showed that they contained a secretory immunoglobulin A reactive with all the virulence-associated proteins studied.

CONCLUSION

These results suggest that maternal antibodies may protect infants from enteropathogenic E. coli infection by interfering with adherence processes (anti-intimin and anti-bundle-forming pili antibodies) and cell signaling (anti-enteropathogenic Escherichia coli-secreted protein A and B antibodies.

Decrease in passive cutaneous anaphylaxis reactions in rats secondary to stress

Anaphylaxis was assayed by the passive cutaneous anaphylaxis (PCA) test in male Wistar rats (250 g body weight). Three experimental groups were used: animals restrained in an electric chamber and submitted to electric shock immediately after sensitization and 24 h before anaphylaxis (31 animals), animals restrained in the electric chamber for the same time but receiving no electric shock (23 animals), and non-manipulated, home-cage control animals (24 animals). The frequency of PCA reactions was decreased in the group of animals submitted to restraint when compared with the home-cage control group. However, the group of animals submitted to both restraint and electric shock showed no decrease in the frequency of PCA reactions. It is suggested that, in rats, stress induced by restraint decreases PCA reactions and that this decrease is counteracted by a simultaneous stress induced by electric shock.

Influence of stress on IgE production

Intense acute stress, consequent to restraint, leads to a diminished production of IgE antiovalbumin antibodies in mice. The IgE content of sera from experimental or control animals was assayed by the enzyme-linked immunosorbent assay (ELISA) at days 8, 16, and 20 after immunization. The statistics revealed significant differences in the IgE level of the animals submitted to acute stress and home cage control animals on days 16 and 20 after immunization, but not on day 8.