Mite faeces are a major source of house dust allergens

The association between house dust allergy and asthma has long been recognized, and it has been demonstrated that a major allergen in house dust is related to the presence of mites of the genus Dermatophagoides. Using extracts of mite culture for skin testing, as many as 10% of the population and up to 90% of allergic asthmatics give positive immediate reactions. Although mites may occasionally become airborne during bed-making, it has also been demonstrated that they 'secrete or excrete' some allergen. Recently, we have shown that up to three-quarters of the serum IgE antibodies to mites are directed against a major allergen-antigen P1 (molecular weight 24,000). Using a radioimmunoassay it is possible to measure the concentration of this glycoprotein in both dust samples and mite cultures. These measurements, which are reported here, show that more than 95% of the allergen accumulating in mite cultures is associated with faecal particles.

Experimental intra-abdominal abscesses in rats: development of an experimental model

An animal model has been developed to study the evolution of intra-abdominal abscesses. Gelatin capsules containing pooled colonic contents and barium sulfate were prepared in an anaerobic chamber and implanted into the pelvic region of Wistar rats. The natural course of the ensuing disease was studied in various groups according to the source of the inoculum and sex of the recipient. Colonic contents derived from rats fed a grain diet produced a highly lethal disease with an 80% mortality rate for males and 100% for females. Most deaths occurred within 3 days of implantation, and autopsies showed generalized peritonitis. The addition of blood to the inoculum caused a rapidly fatal peritonitis in all animals. With an inoculum derived from meat-fed rats implanted in male recipients, there was a biphasic disease. Initially, there was peritonitis associated with 43% mortality. All animals that survived this acute period developed discrete intra-abdominal abscesses by the seventh postoperative day. The latter stage was characterized by an indolent course and progressive enlargement of abscesses.

Solid-phase microtiter radioimmunoassay for detection of the Norwalk strain of acute nonbacterial, epidemic gastroenteritis virus and its antibodies

The development of microtiter solid-phase radioimmunoassays for the detection of Norwalk antigen and its antibody is described. The tests are simple to perform and are sensitive and specific. The test for antigen can be used on crude stool filtrates and suspensions. Both tests are at least as sensitive as immune electron microscopy and more sensitive than immune adherence assay.

Analysis of nonspecific reactions in enzyme-linked immunosorbent assay testing for human rotavirus

Solid-phase enzyme immunoassays can be utilized to detect antigens directly in clinical specimens. However, a small number of stools which we tested for human rotavirus by enzyme-linked immunosorbent assay (ELISA) were found to have nonspecific activity in the absence of rotaviral antigen. Similar nonspecific activity was found in eight of eight sera which contained rheumatoid factor. This nonspecific activity was markedly reduced by pretreatment of the specimens with reducing agents, normal goat serum, and anti-human immunoglobulin M (IgM). Thus, it is likely that these specimens contain an IgM antibody capable of reacting nonspecifically with the other components of the assay. Although pretreatment with the mild reducing agent N-acetylcysteine markedly reduced this nonspecific activity, such treatment did not reduce the specific ELISA activity due to rotavirus. Other treatments did produce a reduction in specific activity. Thus pretreatment with N-acetylcysteine offers a practical means to increase the specificity of ELISA systems without reducing their sensitivity.

Specific immunoglobulin-secreting human blood cells after peroral vaccination against Salmonella typhi

Studies on intestinal immunity in animals have suggested that lymphocytes, after sensitization in Peyer's patches and maturation in regional lymph nodes, home via the circulation to the intestinal wall, where they secrete antibodies into the lumen. To detect such homing cells in the blood of human volunteers given oral, attenuated Salmonella typhi vaccine, we used the solid-phase enzyme-linked immunospot assay for S. typhi-specific antibody-secreting cells (ASCs). ASCs were found in eight of 10 individuals after the third postvaccination day, peaked in level on day 7, and were undetectable on day 14. Of the cells secreting specific immunoglobulin, approximately 62% produced IgA, 32% IgM, and 6% IgG. Antibodies could not be demonstrated in serum, saliva, or feces. This technique might give an opportunity to follow the response to antigens entering the body via mucous membranes. It will be of interest to correlate these findings with protection against diseases after peroral vaccination.

Enzyme-linked immunosorbent assay for detection of hepatitis A antigen in stool and antibody to hepatitis A antigen in sera: comparison with solid-phase radioimmunoassay, immune electron microscopy, and immune adherence hemagglutination assay

Previously described techniques for detection of hepatitis A antigen (HA Ag) and antibody (anti-HA) have required purified HA Ag and expensive equipment. Herein is described an enzyme-linked immunosorbent assay (ELISA) for specific detection of HA Ag in human stool filtrates and of anti-HA in sera by using selected HA Ag-containing human stool filtrates as the antigen source. Because human stools often react nonspecifically in serological tests for HA Ag, blocking with preexposure and hyperimmune anti-HA sera from a chimpanzee inoculated with hepatitis A virus was used to confirm specific detection of HA Ag. The sensitivity of ELISA was found to be comparable to that of solid-phase radioimmunoassay (SPRIA) and immune electron microscopy (IEM). Of 37 acute-phase stools collected from nine patients, 16 were positive for HA Ag by ELISA. In 13 of these, HA Ag particles were found by IEM, and an additional 3 stools negative by ELISA contained HA Ag particles by IEM. Eight control stools were negative by both ELISA and IEM. Anti-HA was measured in sera by demonstrating its ability to block binding of the enzyme conjugate to HA Ag in a stool without detectable nonspecificity. This test (blocking ELISA) was as sensitive and specific as blocking SPIRA, IEM, and immune adherence hemagglutination and, like SPRIA and IEM, detected early-developing antibody. The ELISA is simple to perform and requires only a minimum of equipment. It is useful for screening stools for HA Ag and for monitoring HA Ag during purification, as well as for detecting early and late anti-HA in sera.

Immunochemical study of the malabsorption syndrome with cow's milk intolerance

The effect of cow's milk provocation on the immunoglobulins in the intestinal mucosa, intestinal juice, stool extracts, as well as on the levels of antibodies to cow's milk and beta-1C/A in serum, was studied in 18 infants with the malabsorption syndrome. The infants improved on breast milk and were therefore suspected to be intolerant to cow's milk and challenged with it. At the time of clinical relapse a marked and uniform increase in the numbers of IgA- and IgM-containing cells, 2.4 times as many on the average as before challenge, was observed in the jejunal mucosa of eight reacting patients at nine provocations with cow's milk. There was no abnormality in the immunoglobulin-containing cells before challenge or in biopsy specimens taken shortly after the resumption of the elimination diet (breast milk). The clinical reaction was preceded by a pronounced rise in the IgA and IgM contents of stool extracts, and a rise in the titre of haemagglutinating antibodies and serum IgA, changes which subsided rapidly after withdrawal of cow's milk. There was no evidence that the reaction was IgE-mediated or complement-consuming. In some of the 10 patients who tolerated cow's milk challenge clinically there was an increase in both IgA- and IgM-containing cells suggestive of a local immunological reaction although no clinical intolerance was provoked and other immunological signs were weak or absent. In other non-reacting patients no immunological reaction was noted. Therefore it is evident that cow's milk is the agent responsible for the strong local intestinal reaction coinciding with the clinical symptoms.

Hepatitis A antigen particles in liver, bile, and stool of chimpanzees

Virus-like hepatitis A antigen (HA Ag) particles, presumably hepatitis A virus, were isolated from the liver, bile, and stool of three chimpanzees that had been infected with stool filtrates containing HA Ag particles. Specimens of serum, stool, liver biopsy material, and bile were obtained at selected intervals during the experiment. The animals developed mild hepatitis 19-21 days after inoculation, and antibody to HA Ag appeared de novo in their convalescent-phase serum. During acute illness, virus-like particles similar to the HA Ag particle were seen in liver cell cytoplasm by electron microscopy. HA Ag particles were detected by immune electron microscopy and a new radioimmunoassay in isopycnically banded samples of liver, bile, and stool. HA Ag particles were found at densities of 1.29-1.39 g/cm3, but the major peak density for antigen particles in samples of liver, bile, and stool was approximately 1.34 g/cm3. The fact that HA Ag particles can be recovered from chimpanzee liver, bile, and stool makes these potentially important sources of infectious and antigenic materials.

Enzyme-linked immunosorbent assay for determination of major excrement allergens of house dust mite species D. pteronyssinus, D. farinae and D. microceras

Species-specific enzyme-linked immunosorbent assays (ELISA) for major excrement allergens (Dp42, Df6 and Dm6) of D. pteronyssinus, D. farinae and D. microceras in house dust were established, using immunoabsorbed, monospecific rabbit antibodies, coupled to horse radish peroxidase. The limit of detection was 13, 4 and 38 ng/ml, respectively. The coefficient of variation for the entire procedure, including dust sieving (212 micron) and extraction was 5-16% for allergen levels above 1000 ng/g dust. Allergen concentration by ELISA correlated well with the number of mite bodies identified and counted by microscopy in 31 dusts (r = 0.88, 0.86 and 0.82 for combined Dermatophagoides sp., D. pteronyssinus and D. farinae group, resp.) Dermatophagoides allergen was recorded in 21/22 mattress dusts (median: 26,000 ng/g; maximum: 290,000 ng/g). D. pteronyssinus allergen occurred in largest amounts (median 7,500 ng/g) followed by D. microceras (median 650 ng/g) and D. farinae (median 240 ng/g).

Epidemic non-A, non-B hepatitis in Nepal. Recovery of a possible etiologic agent and transmission studies in marmosets

An epidemic of non-A, non-B hepatitis occurred in Kathmandu Valley, Nepal, during 1981-1982, with approximately 7.6% of households and 1.4% of individuals affected. Cases occurred preponderantly in the 15- to 34-year-old age group (70%), with most cases (75%) occurring in males. A high mortality rate (21%) occurred in pregnant women admitted to the hospital. No single water source was implicated, but epidemic peaks occurred during monsoon rains, and multiple opportunities for enteric transmission existed. One of eight patient stools examined by immune electron microscopy revealed aggregated, antibody-coated, 27-nm viruslike particles when convalescent serum samples were used as sources of antibody. Inoculation of two chimpanzees and four marmosets with a suspension of this stool resulted in elevated liver enzyme activity in three marmosets. Fecal excretion of 27-nm particles during the acute phase of disease (with temporally coincident antigen activity by radioimmunoassay) was observed in one marmoset, which also developed convalescent antibody against the particles in the original inoculum.

Seroepidemiological investigation of patients and family contacts in an epidemic of hepatitis A

Serial blood and faecal samples were collected from patients and family contacts during an outbreak of hepatitis A in a village and tested by a solid-phase competitive type radioimmunoassay for hepatitis A antigen and hepatitis A antibody. The amount and duration of excretion of hepatitis A antigen was correlated with the severity of the illness. In 2 severe clinical cases, hepatitis A antigen was demonstrated in faecal extracts 11 days before the onset of jaundice and continuing for 10 days thereafter, with maximum shedding during the late incubation period. Faecal antigen was demonstrated in low concentrations for only 2 days in a patient with mild disease and in a person with subclinical infection. There was an inverse correlation between the incidence of infection and prevalence of hepatitis A antibody and age. Of 24 infections, 19 (79%) occurred in persons in the age group 0 to 20 years, a group in which only 6% of individuals had pre-existing antibody. Hepatitis A antibody was present in the serum of 3 persons in low titres of 1:20 to 1:40 on the day jaundice developed. The antibody titres increased very rapidly during the following 2 weeks of illness and slowly during the following months, reaching titres of 1:900 to 1:3500. In a separate study, a mean antibody titre of 1:591 was found in 13 patients, 12 years after clinical hepatitis A with jaundice.

Experimental infection of chimpanzees with the Norwalk agent of epidemic viral gastroenteritis

A fecal filtrate of human origin containing the Norwalk agent of epidemic viral gastroenteritis was administered by stomach tube to chimpanzees in an attempt to induce diarrheal disease. Significant postchallenge serum antibody rises against Norwalk viral antigens were demonstrated in all animals using the techniques of immune electron microscopy and radioimmunoassay. In addition, viral antigens were detected in feces from five of nine animals using radioimmunoassay. Clinical illness characterized by diarrhea and/or vomiting did not occur. Infection was transmitted subsequently by feeding four additional chimpanzees a fecal filtrate prepared from one of the previously infected animals. Development of an antibody response in four animals and detection of viral antigen in two animals that received this passage filtrate indicated that viral replication had occurred in the absence of clinical illness. The availability of the chimpanzee as an experimental animal host susceptible to infection with the Norwalk agent should facilitate the study of epidemic viral gastroenteritis.

Absorption of colostral immunoglobulin G in the newborn dairy calf

Five groups of eight newborn calves were used to study absorption of colostral immunoglobulin G. One feeding of 2 liters of pooled colostrum was given at one of 6, 12, 24, 36, or 48 h after birth. Concentrations of immunoglobulin G in blood plasma and feces were measured by an immunodiffusion technique. Plasma volume and fecal excretion also were measured. When colostrum was given 6 h after birth, 65.8% of the ingested immunoglobulin G appeared in the plasma. This percentage declined rapidly to reach 46.9%, 11.5%, 6.7%, and 6.0% when colostrum was given at the ages of 12, 24, 36, and 48 h. Total fecal immunoglobulin G increased linearly with age. The quantities not recovered from plasma and feces reached a maximum when colostrum was given at 24 or 36 h after birth. Immunoglobulin G can be "lost" to a great extent via routes other than plasma and feces during this time. Quantities of immunoglobulin G measured in plasma represent apparent rather than true absorption.

Isolation and identification of a Giardia lamblia-specific stool antigen (GSA 65) useful in coprodiagnosis of giardiasis

A Giardia lamblia-specific antigen (GSA 65) was isolated from stools of G. lamblia-positive patients by crossed- and line-immunoelectrophoresis and counterimmunoelectrophoresis (CIE) in agarose by using rabbit antiserum prepared against G. lamblia cysts. CIE with rabbit anti-GSA 65 monospecific antiserum revealed that GSA 65 was present in aqueous stool eluates of giardiasis patients and in cysts and trophozoites of the parasite. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of immunoaffinity-purified antigen followed by Western blotting showed that the molecular weight of this molecule was about 65,000. GSA 65 was detectable by CIE in stool eluates of 36 of 40 giardiasis patients but not in eluates of 10 G. lamblia-negative asymptomatic controls. GSA 65 was detected in stool eluates of 2 of 18 individuals with chronic diarrhea who were negative for parasites by microscopic examination. Cross-specificity studies with other genera of parasitic protozoa performed by using CIE and immunofluorescence indicated that GSA 65 was present only in strains of G. lamblia. Based on these findings, GSA 65 may prove to have an important application in the design of sensitive diagnostic tests for giardiasis.

Quantification of specific antibody response to Cryptosporidium antigens by laser densitometry

Cryptosporidium spp. is a protozoan parasite with worldwide distribution associated with diarrhea in immunocompromised patients (particularly those with acquired immunodeficiency syndrome [AIDS]) and in immunocompetent humans. Immunoglobulin M (IgM) and IgG antibody responses are readily detected by an enzyme-linked immunosorbent assay. To determine which Cryptosporidium antigens invoke antibody responses in humans, we performed polyacrylamide gel electrophoresis using purified oocysts, followed by Western blots with human sera from various populations. Of 40 sera from persons with cryptosporidiosis (24 AIDS and 16 non-AIDS patients), in 37 (93%) a 23,000-dalton antigen measured quantitatively by laser densitometry was recognized. Of 63 sera from IgM- or IgG-positive individuals, as determined by enzyme-linked immunosorbent assay, in 58 (92%) this same antigen was recognized. Up to three additional bands between 125,000 and 175,000 daltons were identified by some of these sera. These results suggest that most persons infected with Cryptosporidium spp. produce antibodies which recognize at least one common low-molecular-weight antigen. Isolation of this antigen will be useful in development of diagnostic tests and may be important in the study of immunity.

Cross antigenic and allergenic properties of the house dust mite Dermatophagoides farinae and the storage mite Tyrophagus putrescentiae

The crossed antigenicity and allergenicity of the storage mite Tyrophagus putrescentiae (TP) and the house dust mite Dermatophagoides farinae (DF) were characterized by means of crossed immunoelectrophoresis and crossed radioimmunoelectrophoresis. DF extracts exhibited 32 antigens and as many as eight were demonstrated to be allergens. DF feces exhibited 20 antigens and six of these were allergens. Twenty antigens and two allergens were demonstrated for TP. Two antigenic and allergenic determinants were shared by DF and TP, and two determinants were also shared by DF feces and TP feces. TP feces and DF shared two antigenic and allergenic determinants. Our results demonstrated that the two mites and their feces extracts contain multiple antigens and allergens.

Parameters affecting the association of vibrios with the intestinal surface in experimental cholera

Intestinal antibody (coproantibody) significantly reduced the adsorption of heat-killed Vibrio cholerae to the mucosa of in vivo isolated ileal loops of adult rabbits. This suggests a direct effect of coproantibody on adsorption, which appears to function in addition to the antibacterial mechanism described earlier. When antivibrio serum was administered passively into intestinal loops, it showed a predilection for the intestinal mucosa. In vivo adsorption of vibrios appeared to parallel their viability, i.e., vibrios killed by heat or in the presence of neomycin adsorbed significantly less than live vibrios. In contrast, in vivo adsorption was only slightly affected in the presence of bacteriostatic concentrations of tetracycline. Adsorption of Salmonella senftenberg and V. cholerae to slices of rabbit ileum in Krebs-Ringer solution appeared to involve different mechanisms, in that the former was strongly removed from the intestinal tissues by sodium lauryl sulfate, whereas vibrios were not affected by this agent. Triton X-100 increased the adsorption of vibrios, whereas rabbit bile and changes in pH had no effect.

Enzyme-linked immunosorbent assay for diagnosis of rotavirus infections in calves

An enzyme-linked immunosorbent assay for the diagnosis of rotavirus infection in calves is described. The assay was more efficient for the detection of rotavirus antigens in calf feces than were electron microscopy and immunoelectroosmorphoresis.

A method of obtaining, processing, and analyzing human intestinal secretions for antibody content

Human intestinal secretions can be readily obtained using a commercially available intestinal lavage solution. Although such secretions contained abundant protease activity, significant loss of immunoglobulins was prevented by the addition of a mixture of protease inhibitors. The total content of IgA, IgM, and IgG antibody in secretions was measured using sandwich ELISA. In the secretions of ten normal volunteers IgA was most abundant (197 micrograms/ml +/- 103 SD) followed by IgM (12.5 micrograms/ml +/- 6.8 SD) and IgG (0.24 micrograms/ml +/- 0.04 SD). The IgA in secretions was predominantly secretory IgA as shown by sucrose density centrifugation. The effect of intestinal secretions on the sensitivity of the antigen-specific ELISA was tested by adding murine myeloma IgA anti-TNP added to samples of human secretions. IgA anti-TNP activity could be detected as low as 1 ng/ml, and there was no evidence of interference with the ELISA by other constituents in the secretions. Using these methods an antigen-specific secretory IgA anti-cholera toxin B subunit response in the secretions of volunteers given an oral B subunit vaccine was readily demonstrated.

Chronic shedding of bovine enteric coronavirus antigen-antibody complexes by clinically normal cows

Using an ELISA for the detection of virus-specific immune complexes, ten cows were found to be shedding bovine enteric coronavirus. The shedding patterns from five of these animals were followed for a period of 12 weeks, and all were found to be chronically shedding virus. Despite the presence of both faecal and serum antibody the infection was not cleared; therefore, the role of cell-mediated immunity (CMI) was investigated by immunosuppressing the chronically shedding cows with dexamethasone. No major role for CMI in maintaining the chronic infection could be determined, although immunosuppression did result in a temporary reduction in the shedding of virus-specific immune complexes.

Comparison of solid phase test systems for demonstrating antibodies against hepatitis A virus (anti-Hav) of the IgM-class

Three methods were compared for determining anti-HAV of the IgM class. In the first method flat-bottomed microtiter plates coated consecutively with anti-HAV of the IgG class and HAAg were incubated with patient serum and, after washing, peroxidase conjugated anti-mu was added. After subsequent incubation with substrate the enzymatic reaction was stopped and the optical density was measured. In the second method the solid phase was coated first with antibodies to IgM and after incubation with patient serum and subsequent incubations with HAAg and 125I anti-HAV of the IgG class radioactivity was counted. These two methods were compared with reorienting sucrose gradient ultracentrifugation, an established method for demonstrating specific IgM antibodies. The persistence of IgM anti-HAV in 103 sera drawn at different times after onset of jaundice was evaluated. Sera drawn up to 30 days after onset of hepatitis A were IgM anti-HAV positive with both of the first two methods. Forty-one to 90 days after onset of illness IgM anti-HAV could be demonstrated with the first method in 47% of the patients, in 94% with the second method, and in 82% with gradient centrifugation. The second method was most sensitive and could be adjusted so that at a serum dilution of 1:10(4) anti-HAV IgM was detected only up to six months after infection. In contrast to the first method, nonspecific reactions caused by rheumatoid factor were not detected with the second method. During a one-year period about 15,000 sera of patients with clinical diagnoses of acute hepatitis were tested; the positive results correlated well with the clinical data, and there was no indication of nonspecific positive results.

Protection between different serotypes of bovine rotavirus in gnotobiotic calves: specificity of serum antibody and coproantibody responses

In a previous study, different U.S. isolates of bovine rotavirus were studied for their serotypes and cross-protective properties (G. N. Woode, N. E. Kelso, T. F. Simpson, S. K. Gaul, L. E. Evans, and L. Babiuk, J. Clin. Microbiol. 18:358-364, 1983). Three viruses belonging to two different serotype groups were used as vaccines in gnotobiotic calves, which were subsequently challenged with B641 or B223, representing the two bovine serotypes. In the present work, the experiments were repeated with more calves and the specificity of their antibody responses was measured and compared with the results of the protection studies. Protection between different serotypes occurred under both homologous and heterologous conditions but was not directly serotype dependent. B223 virus showed both homologous and heterologous protection against B223 and B641 challenge viruses. This was a one-way reaction, as B641 did not induce protection against B223. Neonatal calf diarrhea virus vaccine produced neither homologous (against B641) nor heterologous (against B223) protection. The plaque reduction neutralization titers of serum antibody and coproantibody did not predict a state of protection against the challenge virus. Calves vaccinated with neonatal calf diarrhea virus or B641 developed neutralizing antibodies to their respective heterologous challenge viruses but were not protected. After challenge, the boosted coproantibody plaque reduction neutralization response to the original vaccine virus was greater than that to the challenge virus.

Comparison of enzyme-immunoassay and radioimmunoassay for detection of human rotaviruses and adenoviruses from stool specimens

An enzyme-immunoassay (EIA) using polystyrene beads as the solid phase, guinea pig anti-rotavirus or anti-adenovirus immunoglobulin as primary antibody, rabbit anti-rotavirus or anti-adenovirus immunoglobulin as secondary antibody, and horseradish peroxidase-conjugated swine anti-rabbit immunoglobulin as indicator antibody, has been developed for the detection of human rotavirus and adenovirus antigens from stool specimens. A comparison of the developed EIA and radioimmunoassay (RIA) used previously in our laboratory was made with 250 stool specimens from children with acute gastroenteritis. Two specimens were found negative by both rotavirus and adenovirus EIAs but not by RIAs, but in each of these cases confirmatory EIA tests showed them to be false negatives. The confirmatory EIA tests were also necessary in several cases to prove the specificity of the binding or to eliminate non-specific reactions with specimens giving low positive reactions in EIA. The developed EIA was found to be as specific, sensitive and reliable as RIA in the routine diagnosis of rotavirus and adenovirus gastroenteritis provided that appropriate confirmatory tests were included.