Quantification of specific antibody response to Cryptosporidium antigens by laser densitometry

Cryptosporidiosis in HIV/AIDS patients in Kenya: clinical features, epidemiology, molecular characterization and antibody responses

We investigated the epidemiological and clinical features of cryptosporidiosis, the molecular characteristics of infecting species and serum antibody responses to three Cryptosporidium-specific antigens in human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS) patients in Kenya. Cryptosporidium was the most prevalent enteric pathogen and was identified in 56 of 164 (34%) of HIV/AIDS patients, including 25 of 70 (36%) with diarrhea and 31 of 94 (33%) without diarrhea. Diarrhea in patients exclusively infected with Cryptosporidium was significantly associated with the number of children per household, contact with animals, and water treatment. Cryptosporidium hominis was the most prevalent species and the most prevalent subtype family was Ib. Patients without diarrhea had significantly higher serum IgG levels to Chgp15, Chgp40 and Cp23, and higher fecal IgA levels to Chgp15 and Chgp40 than those with diarrhea suggesting that antibody responses to these antigens may be associated with protection from diarrhea and supporting further investigation of these antigens as vaccine candidates.

Identification and immunological characterization of three potential vaccinogens against Cryptosporidium species

Cryptosporidiosis is a ubiquitous infectious disease, caused by the protozoan parasites Cryptosporidium hominis and Cryptosporidium parvum, leading to acute, persistent, and chronic diarrhea with life-threatening consequences in immunocompromised individuals. In developing countries, cryptosporidiosis in early childhood has been associated with subsequent significant impairment in growth, physical fitness, and intellectual abilities. Currently, vaccines are unavailable and chemotherapeutics are toxic and impractical, and agents for immunoprophylaxis or treatment of cryptosporidiosis are a high priority. Availability of the genome sequences for C. hominis and C. parvum provides new opportunities to procure and examine novel vaccine candidates. Using the novel approach of "reverse vaccinology," we identified several new potential vaccine candidates. Three of these antigens--Cp15, profilin, and a Cryptosporidium apyrase--were delivered in heterologous prime-boost regimens as fusions with cytolysin A (ClyA) in a Salmonella live vaccine vector and as purified recombinant antigens, and they were found to induce specific and potent humoral and cellular immune responses, suggesting their potential as new vaccinogens against Cryptosporidium infection.

Activated CD8+ T cells contribute to clearance of gastric Cryptosporidium muris infections

The role of CD4+ and CD8+ T lymphocytes in the development of a protective immune response against Cryptosporidium muris infection was studied by the reconstitution of severe combined immunodeficient (SCID) mice with well-defined populations of either naive or immune CD8+ or CD4+ T lymphocytes. Adoptive transfer of both naive and immune CD4+ T lymphocyte subpopulations protects SCID mice against cryptosporidiosis. Moreover, a significant biological impact of activated CD8+ T cells against gastric cryptosporidiosis was observed. The significant difference in the course and intensity of the infection in reconstituted SCID mice was found to be dependent on the protective function of both the CD4+ and CD8+ T-cell populations transferred. While SCID mice reconstituted with either immune or naive CD4+ or immune CD8+ T-cell subpopulations resolved the infection within 29, 37 and 51 days post-infection, respectively, those reconstituted with naive CD8+ T cells suffered from chronic infection similar to control SCID mice. Reconstitution with CD4+ T cells resulted in suppression of oocyst excretion and shortening of patent period in comparison with SCID mice reconstituted with CD8+ T cells. Thus, although CD4+ T cells are considered important in protective immunity, our results are the first to demonstrate the involvement of activated CD8+ T lymphocytes in the protection of mice against gastric cryptosporidiosis.

Serum immunoglobulin G, M and A response to Cryptosporidium parvum in Cryptosporidium-HIV co-infected patients

Background

Cryptosporidium parvum, the protozoan parasite, causes a significant enteric disease in immunocompromised hosts such as HIV patients. The present study was aimed to compare serum IgG, IgM and IgA responses to crude soluble antigen of C. parvum in HIV seropositive and seronegative patients co-infected with Cryptosporidium and to correlate the responses with symptomatology.

Methods

Cryptosporidium parvum specific serum antibody (IgG, IgM and IgA) responses were assessed by ELISA in 11 HIV seropositive Cryptosporidium positive (Group I), 20 HIV seropositive Cryptosporidium negative (Group II), 10 HIV seronegative Cryptosporidium positive (Group III), 20 HIV seronegative Cryptosporidium negative healthy individuals (Group IV) and 25 patients with other parasitic diseases (Group V).

Results

A positive IgG and IgA antibody response was observed in significantly higher number of Cryptosporidium infected individuals (Gp I and III) compared to Cryptosporidium un-infected individuals (Gp II, IV and V) irrespective of HIV/immune status. Sensitivity of IgG ELISA in our study was found to be higher as compared to IgM and IgA ELISA. The number of patients with positive IgG, IgM and IgA response was not significantly different in HIV seropositive Cryptosporidium positive patients with diarrhoea when compared to patients without diarrhoea and in patients with CD4 counts <200 when compared to patients with CD4 counts >200 cells/μl.

Conclusion

The study showed specific serum IgG and IgA production in patients infected with Cryptosporidium, both HIV seropositive and seronegative as compared to uninfected subjects suggesting induction of Cryptosporidium specific humoral immune response in infected subjects. However, there was no difference in number of patients with positive response in HIV seropositive or seronegative groups indicating that HIV status may not be playing significant role in modulation of Cryptosporidium specific antibody responses. The number of patients with positive IgG, IgM and IgA response was not significantly different in patients with or without history of diarrhoea thereby indicating that Cryptosporidium specific antibody responses may not be necessarily associated with protection from symptomatology.

Humoral immune response in IL-12 and IFN-gamma deficient mice after infection with Cryptosporidium parvum

Infection with Cryptosporidium spp. causes diarrhoeal disease and has become an important medical and veterinary problem especially in the immunocompromised host. The importance of the adaptive immune response, with CD4+ T-lymphocytes being the major players, has been clearly demonstrated. The requirement of IL-12 and IFN-gamma identifies this response as a Th1-dominated reaction. IFN-gamma is also important in the early phase of the host-parasite interaction. We analysed the outcome of infection in IL-12p40 (IL-12KO) and IFN-gamma (GKO) deficient C57BL/6 mice after primary and secondary challenge with the parasite and, for the first time, we demonstrate the resulting Ig response in sera and vaginal lavages. Although showing differences in the extent and the time course both strains of mice were able to clear infection and developed an almost complete resistance to re-infection. While GKO mice mounted prolonged parasite-specific IgG and IgA responses after primary infection, in IL-12KO mice IgG and IgA titres dropped over time. Re-challenge of mice 5 weeks after primary infection led to a booster effect in Ig response despite the absence of oocyst shedding. The data from infection and re-challenge experiments suggest that in IL-12- or IFN-gamma-deficient mice the development of resistance involves other protective immune responses.

Molecular targets for detection and immunotherapy in Cryptosporidium parvum

Cryptosporidium parvum is an obligate protozoan parasite responsible for the diarrheal illness cryptosporidiosis in humans and animals. Although C. parvum is particularly pathogenic in immunocompromised hosts, the molecular mechanisms by which C. parvum invades the host epithelial cells are not well understood. Characterization of molecular-based antigenic targets of C. parvum is required to improve the specificity of detection, viability assessments, and immunotherapy (treatment). A number of zoite surface (glyco)proteins are known to be expressed during, and believed to be involved in, invasion and infection of host epithelial cells. In the absence of protective treatments for this illness, antibodies targeted against these zoite surface (glyco)proteins offers a rational approach to therapy. Monoclonal, polyclonal and recombinant antibodies represent useful immunotherapeutic means of combating infection, especially when highly immunogenic C. parvum antigens are utilized as targets. Interruption of life cycle stages of this parasite via antibodies that target critical surface-exposed proteins can potentially decrease the severity of disease symptoms and subsequent re-infection of host tissues. In addition, development of vaccines to this parasite based on the same antigens may be a valuable means of preventing infection. This paper describes many of the zoite surface glycoproteins potentially involved in infection, as well as summarizes many of the immunotherapeutic studies completed to date. The identification and characterization of antibodies that bind to C. parvum-specific cell surface antigens of the oocyst and sporozoite will allow researchers to fully realize the potential of molecular-based immunotherapy to this parasite.

Longitudinal analysis of cryptosporidium species-specific immunoglobulin G antibody responses in Peruvian children

Cryptosporidium species are ubiquitous in the environment and are frequently detected in the stools of children who live where sanitation conditions are poor. To better characterize the immune response to these parasites, we monitored immunoglobulin G (IgG) antibody levels in a cohort of children from Lima, Peru. Two new enzyme-linked immunosorbent assays based on the C. parvum (bovine, subtype IIa) Iowa strain 17-kDa and 27-kDa antigens were used to measure IgG antibody levels in longitudinal serum samples. Antibody responses were detected during infections with C. parvum, C. felis, and C. meleagridis and with four different subtypes of C. hominis. We also noted that the magnitude of the antibody response was related to the number of previous infections and that older children generally had higher levels of antibodies to the two C. parvum antigens. Antibody responses were not associated with infections with either Cyclospora sp. or Giardia sp. We believe the antibody assays will be important tools for monitoring the success of future public health interventions.

Serum antibody response and Cryptosporidium parvum oocyst antigens recognized by sera from naturally infected sheep

The response of specific serum immunoglobulins (IgG, IgM and IgA) and the major antigens of Cryptosporidium parvum recognized by these isotypes were investigated by using enzyme-linked immunosorbent assay and immunoblot techniques in lambs and ewes naturally infected throughout an outbreak of cryptosporidiosis. Serum samples were collected from 20 lambs the first day they showed diarrhoea (D1), and Days 11 and 22, in addition to single serum samples from 17 of their dams. Serum anti-C. parvum IgG, IgM and/or IgA antibodies were detected in lambs as early as Day 1. Levels of IgM antibodies remained steady from D1 to D11 and increased at D22, whereas the IgG response decreased from D1 to D11 and subsequently increased. In contrast, IgA antibodies rapidly fell from D1 and all lambs were seronegative at D11 and D22. The highest levels of specific antibodies were detected in sera from ewes. In fact, all ewes were seropositives for IgM and IgA isotypes and most (16/17) showed positive levels of IgG. Four protein fractions (37-39, 42-48, 51-57 and 60-69 kDa) were the most frequently recognized by IgG and IgM from lamb sera. A low molecular weight fraction (12-14 kDa) reacting with IgG and IgA in most lamb sera was scarcely recognized by IgM and three broad bands were frequently recognized by IgA antibodies (23-25, 51-57 and 90-95 kDa). The recognition pattern of 23-25 kDa peptides by IgA from lamb sera clearly increased with the age. Peptides of 42-48, 51-57, 60-69 and 71-78 kDa were most frequently recognized by IgG and IgM from ewe sera. In relation to IgA antibodies from ewe sera, a frequent immunoreactivity was found with proteins in the intervals between 12 and 22 kDa as well as between 32 and 34 kDa and practically all sera reacted with fractions from 42 to 95 kDa.

Enzyme immunoassay detection of antigen-specific immunoglobulin g antibodies in longitudinal serum samples from patients with cryptosporidiosis

Cryptosporidium parvum is a protozoan parasite that causes diarrheal illness in a wide range of mammalian hosts, including humans. Characteristic serum immunoglobulin G (IgG) antibody responses to antigens in the 27- and 17-kDa size ranges have been shown to develop after infection, and several enzyme-linked immunosorbent assay (ELISA) and Western blot assay formats have been used to measure these IgG levels in human serum. Using a collection of serial samples from laboratory-confirmed cryptosporidiosis patients, we compared the results obtained by using two new ELISAs with those obtained with two different Western blot assays. When assayed with the large-format Western blot, 97% of the 67 patients had a demonstrable antibody response on at least one occasion. The Cp23 ELISA correctly identified 93% of the samples that had a 27-kDa response by Western blot and 100% of the negative samples. The Triton antigen ELISA detected 77% of the samples that had a 17-kDa response by Western blot and 88% of the negative samples. The sensitivity of the Triton antigen assay was higher for samples collected between 16 and 92 days after the onset of symptoms (96%). The minigel-format Western blot did not compare favorably with the large-format blot for the detection of antibodies to the 27-kDa antigen (71% sensitivity). A half-life of about 12 weeks was estimated for antibodies to both the 27- and 17-kDa antigens. We believe the Cp23 and Triton antigen ELISAs will be useful in epidemiologic studies of the prevalence of Cryptosporidium infection in the population.

The Serologic response to Cryptosporidium in HIV-infected persons: implications for epidemiologic research

Advances in serologic assays for Cryptosporidium parvum have made serology an attractive surveillance tool. The sensitivity, specificity, and predictive value of these new assays for surveillance of immunocompromised populations, however, have not been reported. Using stored serum specimens collected for the San Francisco Men's Health Study, we conducted a case-control study with 11 clinically confirmed cases of cryptosporidiosis. Based on assays using a 27-kDa antigen (CP23), the serum specimens from cases had a median response immunoglobulin (Ig) G level following clinical diagnosis (1,334) and a net response (433, change in IgG level from baseline) that were significantly higher than their respective control values (329 and -32, Wilcoxon p value = 0.01). Receiver operator curves estimated a cutoff of 625 U as the optimal sensitivity (0.86 [0.37, 1.0]) and specificity (0.86 [0.37, 1.0]) for predicting Cryptosporidium infection. These data suggest that the enzyme-linked immunosorbent assay technique can be an effective epidemiologic tool to monitor Cryptosporidium infection in immunocompromised populations.

Nasal immunization of mice with Cryptosporidium parvum DNA induces systemic and intestinal immune responses

DNA immunization offers a novel approach to inducing humoral and cellular immunity against infectious pathogens. We examined whether such an approach could be used against cryptosporiodiosis, an intestinal disease caused by the protozoan parasite Cryptosporidium parvum. This infection is a major problem for young ruminants and immunosuppressed individuals in whom cryptosporidiosis causes life-threatening symptoms. The life cycle of C. parvum takes place in the enterocytes of the intestinal epithelium. We therefore focused our attention on a route of immunization that might induce a mucosal immunoglobulin (Ig)A response. Eight-week-old BALB/c mice were immunized intranasally with DNA encoding a 15-kDa C. parvum sporozoite antigen (CP15-DNA) cloned onto the plasmid pcDNA3. CP15-DNA-immunized mice developed specific and longlasting production of anti-CP15 Ig A in intestinal secretions and specific IgG in sera 3 months and 1 year after the first DNA inoculation. CP15-DNA-immunized mice also developed an antigen-specific T lymphocyte proliferative response in both spleen and mesenteric lymph nodes. Control mice that received the pcDNA3 plasmid alone did not develop specific humoral and cellular responses. These results indicate that plasmid DNA may provide a powerful means of eliciting intestinal humoral and cellular responses to C. parvum infections in mammals.

Protection of kids against Cryptosporidium parvum infection after immunization of dams with CP15-DNA

In this study the effectiveness of a DNA vaccine to confer protection against cryptosporidiosis, an enteric infection of lifestock and humans, was evaluated. A vaccination protocol using a recombinant plasmid encoding the 15 kDa surface sporozoite protein of Cryptosporidium parvum was developed in adult pregnant goats. The present study reports that nasal immunization of pregnant goats with CP15-DNA led to a transfer of immunity to offspring conferring protection against C. parvum infection. Kids from CP15-DNA-vaccinated dams shed significantly fewer oocysts and over a shorter period than did kids from unvaccinated goats. The low level of parasite development in protected kids did not affect their growth whereas unprotected kids grew much slowly. There was still a significant difference in the weights of protected and unprotected kids after complete recovery. Anti-CP15 antibodies were present in serum and colostrum from vaccinated goats. Nevertheless, the precise immune mechanism of protection has still to be determined. This vaccine should reduce the economic losses due to cryptosporidiosis in ruminants, specially in small ruminants (calves, lambs, kids). It has also the potential to reduce environmental contamination by reducing oocyst shedding.

Detection by enzyme immunoassay of serum immunoglobulin G antibodies that recognize specific Cryptosporidium parvum antigens

Human infection with Cryptosporidium parvum usually elicits characteristic immunoglobulin G (IgG), IgA, and IgM antibody responses against two sporozoite surface antigens with apparent molecular masses of approximately 27 and 17 kDa. We have determined that these two antigens are actually complex families of related antigens. We have developed two new enzyme-linked immunosorbent assays (ELISAs) for the detection and quantitation of serum IgG antibodies against both antigens. The assays utilize a recombinant form of the 27-kDa antigen and a partially purified native fraction isolated from sonicated whole oocysts that contains 17-kDa antigen. An immunoblot assay previously developed in our laboratory served as the reference, or "gold standard," seroassay for the assessment of the new ELISAs. Positive responses with the recombinant-27-kDa-antigen ELISA were correlated with the immunoblot results for the 27-kDa antigen, with a sensitivity and specificity of 90 and 92%, respectively. Similarly, positive responses with the partially purified native-17-kDa-antigen ELISA correlated with the immunoblot results for the 17-kDa antigen, with a sensitivity and specificity of 90 and 94%, respectively. For both ELISAs the median IgG antibody levels for serum sets collected during outbreaks of waterborne C. parvum infection were at least 2.5-fold higher than the levels determined for a nonoutbreak set. Using the immunoblot as the "gold standard," the new ELISAs were more specific and, in the case of the 27-kDa-antigen ELISA, more sensitive than the crude oocyst antigen ELISA currently in use. These assays will be useful in future epidemiologic studies.

Determination of immuno-cross-reactivity between Cryptosporidium parvum and Eimeria spp

Immuno-cross-reactivity between Cryptosporidium parvum and Eimeria spp. was studied by the indirect fluorescent antibody test (IFAT) and Western blot procedure. Thirty-seven sera from asymptomatic (non-diarrheic) cattle, with known coprological (presence-absence of coccidia) and serological data respecting C. parvum, were tested by IFAT using Eimeria oocysts as antigen. Most sera (54%) displayed immunofluorescence around the surface of the Eimeria oocysts. Simultaneously, serum samples from rabbits naturally infected with Eimeria spp. (E. magna, E. intestinalis and E. residua), but free of C. parvum infection, were used to investigate the recognition of C. parvum oocyst antigens by the Western blot procedure. Fractions in the 11.5-94 kDa range, as well as others with molecular masses over 94 kDa, were recognized by sera from rabbits. Sera collected during patency period showed low or moderate reaction with antigenic fractions in the 11.5-25 kDa range. However, 29, 58 and 71 to 75 kDa proteic fractions were moderately or strongly recognized even after rabbits finished oocyst excretion.

Characterization of secretory IgA responses in mice infected with Cryptosporidium parvum

Mice inoculated at 5, 21 and 28 days of age with 10(6) or 10(7) Cryptosporidium parvum oocysts became infected but did not exhibit any clinical signs of disease. Specific IgA antibodies were detected in faecal extracts from all infected mice by an indirect immunofluorescent assay. These antibodies first appeared between 11 and 37 days post-infection (dpi) and persisted until the end of the experiment at 55 dpl. They appeared earlier in older mice than in newborn mice. Reduction and resolution of oocyst shedding was not directly related, however, to IgA antibody levels in infected mice. Reactive C. parvum antigens were identified by immunoblotting techniques using faecal and serum samples from infected mice. IgA copro-antibodies reacted specifically with two antigens of 26 and 33 kDa, which were also identified by IgG antibodies in mouse serum. The role of these antibodies in the resolution of infections and the subsequent protection against challenge is unknown.

Enteral human serum immunoglobulin treatment of cryptosporidiosis in mice with severe combined immunodeficiency

The anti-cryptosporidial immunoglobulin G antibodies in two commercially available human serum immunoglobulin (HSIG) products were quantified and characterized. The mean level of Cryptosporidium parvum-specific immunoglobulin G in HSIG was eightfold higher than the antibody level found in the sera of three immunocompetent individuals convalescing from cryptosporidiosis. However, HSIG products displayed no reactivity to cryptosporidial antigens in immunoblot analyses, while convalescent-phase sera demonstrated characteristic banding patterns. When HSIG was given to newborn severe combined immunodeficiency (scid) mice before and shortly after experimental infection, a decreased intensity of infection was observed in the intestines of the mice compared with that of control mice. However, there was no difference in mortality or histopathologic findings in the intestines of HSIG-treated and control mice when treatment was not started until 22 days of age. These results indicate that HSIG may be beneficial when given prophylactically; however, HSIG cannot eradicate cryptosporidia from mucosal surfaces in an established infection.

Diagnosis of bovine cryptosporidiosis by indirect immunofluorescence assay using monoclonal antibody

Two hybridoma cell lines against Cryptosporidium parvum oocysts (VRI-CN91) were produced. The isotype of these 2 monoclonal antibodies (mAbs) was IgG2b (1E7.2) and and IgM (C6). Enzyme immuno-transfer blotting analysis showed that 1E7.2 reacted specifically to 36 kDa protein and C6 reacted to 67 and 70 kDa proteins. C. parvum was bound specifically to the surface region of oocysts by these mAbs. No cross-reactivity was observed with tachyzoites of Toxoplasma gondii and oocysts of Eimeria zuernii, E. bovis and E. canadensis of bovine origin. The indirect immunofluorescence assay (IIF) using mAb C6 was successful with counterstain. With the IIF using mAb C6, oocysts appeared as 3 to 5 microns spherical objects fluorescing bright apple green against a reddish dark background. The IIF using mAb C6 was agreed in specificity and sensitivity with those of a commercial diagnostic kit. These results demonstrated that the produced mAbs were specific to C. parvum and that the mAb C6 could be used for diagnosis of cryptosporidiosis.

Major antigens of Cryptosporidium parvum recognised by serum antibodies from different infected animal species and man

Serum humoral immune response to Cryptosporidium parvum was evaluated in six species: mouse, rabbit, lamb, calf, pig and man. Electrophoretic and immunoblot analysis showed that specific animal antibody response appeared between Day 4 and Day 15 post inoculation. The two main target antigens had apparent molecular weights of 15-17 and 23 kDa. They were recognised by each species studied. Serum IgA intensively recognised the 15-17 kDa antigen, except in rabbit. This study demonstrates that these two antigens are consistent targets of humoral immune response and can therefore be of great interest in studies of therapy/prophylaxis.

Quantitative computer image analysis of a human chorionic gonadotropin colloidal carbon dipstick assay

Colloidal particles are widely used in qualitative dipstick assays for the determination of various proteins and haptens. Recently, a new colloidal label has been introduced based on elemental carbon. With this carbon label we have prepared a human chorionic gonadotropin-specific dipstick assay with a sensitivity of 10 mIU/ml. In addition, an image- and data-processing procedure for the quantification of the dipstick assay has been developed. The sum of the pixel grey levels of a carbon line was taken as a measure for this quantitative purpose. The measurement range of the assay is almost three orders of magnitude, i.e. 10 mIU/ml to 500 mIU/ml. The deviation from the mean of two dipstick determinations was 1.22% on average. The within-run and between-run precision, expressed as coefficients of variation at 50 mIU/ml were 1.03% and 1.84%, at 150 mIU/ml 2.14% and 3.77% and at 450 mIU/ml 2.55% and 5.28%, respectively. We have correlated this quantitative sol particle immunoassay with a commercial human chorionic gonadotropin specific radioimmunoassay. In an experiment with 25 human urine samples containing the hormone in amounts from 5 to 300 mIU/ml the correlation coefficient was 0.999. The sol particle immunoassay quantified by computer image analysis has been termed Sol particle Image Processed ImmunoAssay (SIPIA).

Both CP15 and CP25 are left as trails behind gliding sporozoites of Cryptosporidium parvum (Apicomplexa)

Sporozoites of Cryptosporidium parvum were examined after gliding upon glass microscope slides using monoclonal antibodies to the 15 and 25 kDa surface molecules and immunogold-silver enhancement. Both antibodies bound to surface antigen deposited as trials behind parasites, suggesting that both surface molecules are involved in substrate attachment.

Bovine antibody against Cryptosporidium parvum elicits a circumsporozoite precipitate-like reaction and has immunotherapeutic effect against persistent cryptosporidiosis in SCID mice

Control of cryptosporidiosis is currently hampered by the absence of drugs or vaccines proven consistently effective against Cryptosporidium parvum. On the basis of observations that anti-C. parvum antibody has therapeutic effect against cryptosporidiosis, cows were immunized with C. parvum to produce hyperimmune colostral antibody. An antibody-rich fraction was prepared and differentiated from control (nonhyperimmune) antibody by enzyme-linked immunosorbent assay, immunofluorescence assay, immunoelectron microscopy, and in vitro neutralizing titer against DEAE-cellulose-isolated C. parvum sporozoites. Oocyst, purified sporozoite, and merozoite antigens recognized by hyperimmune antibody were defined by Western blot (immunoblot). Hyperimmune antibody recognized antigens common to oocysts, sporozoites, and merozoites, as well as stage-specific antigens. Upon incubation with hyperimmune antibody, sporozoites underwent distinct morphologic changes characterized by progressive formation and eventual release of membranous sporozoite surface antigen-antibody complexes, similar to the malaria circumsporozoite precipitate reaction. The infectivity of sporozoites having undergone this reaction was neutralized. The reaction was minimal or absent on sporozoites incubated with control antibody. To determine therapeutic effect in vivo, persistent C. parvum infection was established in adult severe combined immune-deficient (SCID) mice by oral inoculation with 10(7) oocysts. At 5 weeks postinfection, infected mice were treated for 10 days with hyperimmune or control antibody by inclusion in drinking water and daily gavage. Fecal oocyst shedding and infection scores in the gastrointestinal tract and gall bladder/common bile duct in hyperimmune antibody-treated mice were significantly lower than those in the control antibody-treated mice. Hyperimmune bovine antibody prepared against C. parvum may provide a first-generation therapy for control of cryptosporidiosis. Additionally, the defined antigens can be evaluated as subunit immunogens to produce better-characterized polyclonal antibody for control of cryptosporidiosis or as targets for monoclonal antibody-based immunotherapy.

Identification of Cryptosporidium parvum oocyst/sporozoite antigens recognized by infected and hyperimmune lambs

The appearance, persistence and eventual decline of IgG, IgM and IgA antibodies recognizing Cryptosporidium parvum antigens were studied in naturally infected lambs using a Western blot technique, and the results compared with those obtained using sera from immunized lambs. There was an intense recognition of some low molecular weight proteins (15-17 kDa by IgG and IgA; 28-30 kDa by IgA, IgM and IgG) during the infection and early post-infection period. These peptides were not recognized after Days 45-60 of life. Some high molecular weight antigens (94 kDa) were weakly recognized on Day 15 but more intensely recognized from Day 30 onwards, persisting until at least Day 90. Antibody recognition of these C. parvum proteins could be an indicator of recent or past exposure to the parasite.

[Isolation of Cryptosporidium parvum oocysts from fecal samples--the combination of ether extraction and discontinuous sucrose gradients]

A calf and 50 mice were infected with Cryptosporidium parvum, and their fecal materials were collected and treated with ether extraction (EE), followed by discontinuous sucrose gradients (DSG) method. EE method was to remove some of fat or lipid from feces. Sediments were washed by centrifugation (1,500 x g for 10 min., 3 times) in phosphate-buffered saline and then these washed sediments were sieved sequentially through stainless steel screens with a final mesh of 250 (61 microns porosity) to remove other debris. After sieving, the materials were suspended in 2.5% potassium dichromate solution. Oocysts were counted by using a hemocytometer and the recovery rate of pure oocysts was calculated on the basis of the count. Following centrifugation (1,500 x g for 30 min.) by DSG method, most oocysts were recovered at the interface between a gravity of 1.103 and 1.064. The recovery rates of pure oocysts from the fecal suspension of the calf (3.8 x 10(7)/ml) and the mouse (3.2 x 10(6)/ml) treated with EE method were 81.6% and 51.6%, respectively. It is suggested that the recovery rate was dependent on the number of oocysts in each suspension treated with EE method. To get the 50% recovery rate, there must be more than 2 x 10(6) oocysts per ml of the fecal suspension treated with EE method. By the combination of the two methods it was possible to isolate C. parvum oocysts from normal feces of the calf and mouse as well as from diarrheic feces.

Multiple oral inoculations with Cryptosporidium parvum as a means of immunization for production of monoclonal antibodies

Oral immunization of suckling mice with Cryptosporidium parvum results in a humoral response to a limited set of antigens. Six-day-old BALB/c mice were each inoculated orally with 1 x 10(6) viable oocysts and subsequently administered oral inoculations of 2 x 10(6) viable oocysts at 30 and 60 days following the primary infection. After 45 days, mice were boosted with 1 x 10(6) oocysts orally, plus soluble extracts equivalent to 2 x 10(6) and 1 x 10(6) oocysts given intravenously and intraperitoneally, respectively. Four days later, splenic lymphocytes were fused to Ag8 myeloma cells. Using this method, we have been able to select for monoclonal antibodies that predominantly recognize sporozoite surface and apical complex antigens.

Colloidal carbon particles as a new label for rapid immunochemical test methods: quantitative computer image analysis of results

Colloidal carbon particles can serve as label in sol particle immunoassays. The universal applicability of these particles in qualitative and (semi)quantitative immunoassays has been demonstrated. Sol particle and/or dipstick immunoassays, not yet optimized in terms of sensitivity, are discussed. The colloidal label has been used successfully in a mouse immunoglobulin isotyping kit. Human serum albumin spotted onto nitrocellulose in a concentration range of 7.8 to 1000 ng could be detected using anti-albumin antibody absorbed onto colloidal carbon particles. It was also possible to perform a competitive assay with this conjugate for a concentration range of free human serum albumin varying from 0.25 to 6.75 micrograms. The Kunitz-type trypsin inhibitor from soybean was determined by a colloidal carbon based immunoassay in a range of 2.5 to 160 ng. In this assay, free and colloidal carbon-bound inhibitor competed for binding specific antibodies spotted onto a nitrocellulose membrane. An image- and data-processing procedure has been developed that enables a rapid and simple quantification of colloidal carbon sol particle immunoassays. The average grey level of a spot is taken as a measure for quantitative purposes. This so-called Sol-particle Image Processed ImmunoAssay (SIPIA) procedure is equally well applicable to assays using other colloidal particles.

Cellular biology of Cryptosporidium parvum

With the emergence of Cryptosporidium parvum as a major pathogen encountered in human and veterinary clinical practice, a need for increased knowledge of the cellular- and immuno-biology of this Apicomplexan parasite has developed. Initial work has used paradigms taken from other Apicomplexans, especially Plasmodium, Toxoplasma and Eimeria, as a starting point. In this article, Carolyn Petersen discusses the observation that in these organisms, molecular targets of antibodies (which have protective value, in vivo, against disease) have frequently been located in the apical complex or on the surface of the invasive stages of the parasite and appear to mediate biologically crucial processes including motility, attachment to the host cell, modification of the host membrane, and entry into the host cell. Molecular-biology approaches to the study of enzymes and of structural proteins which mediate motility are also considered. Invasion mechanisms, biochemical pathways and motility may involve molecules that will prove susceptible to immunotherapeutic or chemotherapeutic interruption of cryptosporidiosis.

Bovine humoral immune response to Cryptosporidium parvum

Cryptosporidiosis is a diarrheal disease predominantly affecting cattle and humans. Sera from experimentally infected calves and calves of various ages with no histories of exposure were evaluated for immunoglobulin G to Cryptosporidium parvum. An age-associated increase in immunoglobulin G was present in experimental calves and in calves with no histories of infection from 1 to 3, but not > 3, months of age.

Intestinal parasites in returned travelers

Travelers returning from third-world countries may become infected with a variety of intestinal parasites. Although protozoan infections are more frequently seen, intestinal worms are also encountered. If considered in the differential diagnosis, these infections usually are readily diagnosed and treated.

Cryptosporidium parvum in calves: kinetics and immunoblot analysis of specific serum and local antibody responses (immunoglobulin A [IgA], IgG, and IgM) after natural and experimental infections

Fecal and serum anti-Cryptosporidium parvum immunoglobulin A (IgA), IgM, and IgG were monitored by an enzyme-linked immunosorbent assay after experimental and natural infection of calves with C. parvum. Although all experimentally infected calves showed high levels of colostral antibodies in the feces, they acquired C. parvum infection. Three of five animals died. Calves which acquired natural infection showed only diarrhea. Levels of colostral coproantibodies dropped quickly. Experimental infection was followed by a rise in local anti-C. parvum IgM levels from day 5 postinfection (p.i.). IgM peaked at day 14 p.i. and then disappeared quickly. Anti-C. parvum IgA levels rose between days 7 and 14 p.i. and decreased slowly. Rising levels of coproantibodies coincided with falling oocyst output. Fecal anti-C. parvum IgG levels rose slightly during oocyst output, and IgG disappeared 3 weeks p.i. Similar kinetics were established in naturally infected calves. Although fecal anti-C. parvum IgA levels declined slowly, reinfections were established 5, 7, and 14 weeks after the primary contact. Serum anti-C. parvum IgG levels rose during maximal oocyst excretion, whereas serum anti-C. parvum IgA levels peaked later than did local IgA levels. Challenge reinfection of naturally infected calves at day 112 was not followed by clinical signs or oocyst output or by a secondary antibody response. Sequential Western immunoblotting with fecal extracts revealed up to 32 different parasite antigens. Convalescent-phase sera recognized up to 23 antigens. Fecal IgA reacted intensely with antigens with relative molecular weights (M(r)) of approximately 11,000 and 15,000. These antigens were not recognized by convalescent-phase serum IgG. Both local IgA and serum IgG also showed strong reactions with 23,000- and 44,000-M(r) antigens and with several antigens of between 66,200 and 200,000 M(r). Most bands remained detectable for at least 16 weeks p.i.

Cryptosporidiosis

Before 1982, only eight case reports of human cryptosporidiosis and fewer than 30 papers on Cryptosporidium spp. appeared in the biomedical literature. At that time, cryptosporidiosis was thought to be an infrequent infection in animals and rarely an opportunistic infection in humans. The concept of Cryptosporidium spp. as pathogens has changed dramatically within the past 8 years because of improved diagnostic techniques, increased awareness within the biomedical community, and the development of basic research programs in numerous laboratories. Presently, greater than 1,000 publications including over 400 case reports in the biomedical literature address Cryptosporidium spp. and cryptosporidiosis. Cryptosporidium parvum is now thought to be one of the three most common enteropathogens causing diarrheal illness in humans worldwide, especially in developing countries. It is likely that cryptosporidiosis was previously included in the 25 to 35% of diarrheal illness with unknown etiology. Because of the severity and length of diarrheal illness and because no effective therapy has been identified, cryptosporidiosis is one of the most ominous infections associated with AIDS. The role of C. parvum as an enteropathogen is well established; documentation of its role as a cause of hepatobiliary and respiratory diseases is now appearing in the literature. Our present understanding of the natural history, epidemiology, biology, and immunology of Cryptosporidium spp. as well as the clinical features, pathogenicity, and treatment of cryptosporidiosis are reviewed here.

Characteristics and specificity of hybridoma antibodies against oocyst antigens of Cryptosporidium parvum from man

Hybridoma antibodies (HAbs) against oocyst antigens of a human isolate of Cryptosporidium parvum were developed by fusion of SP2/0 mouse myeloma cells and spleen cells from BALB/c mice immunized with oocyst homogenates. In an indirect immunofluorescence antibody test (IFAT), using as antigen a mixture of air-dried sporozoites and oocysts, HAbs labelled either the oocyst wall or areas of the sporozoite, including the whole organism, the entire surface, a polar region or the interior. Most of the HAbs were specific for the sporozoite surface, and few of them recognized the oocyst wall. In Western blot analysis of oocyst antigens, sporozoite surface-reactive monoclonal antibodies (MoAbs) recognized one or more of seven polypeptide bands with molecular weights in the range 47- greater than 200 kD, and all reacted with the 47 kD band. Each of four heterologous parasite isolates had a unique recognition pattern with a panel of MoAbs in IFAT, suggesting antigenic differences may exist between strains of C. parvum. The ability to differentiate between parasite isolates by immunological methods might be of value in epidemiological studies of cryptosporidiosis.

Characterization of microneme antigens of Cryptosporidium parvum (Protozoa, Apicomplexa)

Two monoclonal antibodies (MAbs) raised against purified excysted oocysts and sporozoites of cryptosporidium parvum reacted in an immunofluorescence assay with antigens located at the anterior pole of the zoites. On Western blots of purified oocysts, these MAbs reacted with a series of bands between 210 and 40 kDa; several of these bands were recognized by both MAbs; others were specific. One MAb (TOU) did not react after periodic acid treatment and was therefore considered to recognize a carbohydrate epitope; as determined by immunoelectron microscopy, this MAb reacted on micronemes of sporozoites and merozoites and also with the peripheral cytoplasm and the parasitophorous vacuole of trophozoites and macrogametes. The other MAb (HAD) reacted with an epitope that was insensitive to periodate treatment but did not react in the immunoelectron microscopy assay. However, the similar labeling pattern obtained with the immunofluorescence assay with both MAbs and the fact that the two antibodies share common bands on Western immunoblots suggest that both MAbs react with molecules located in Cryptosporidium micronemes, one reacting with a glycannic epitope and the other reacting with a peptidic epitope.

Characterization of bovine cellular and serum antibody responses during infection by Cryptosporidium parvum

Cellular and serum antibody responses of calves were monitored for 23 days after oral inoculation of the calves with oocysts of Cryptosporidium parvum. In vitro blastogenic responses of peripheral blood lymphocytes were assessed after stimulation with a C. parvum preparation. Specific lymphocyte blastogenic responses to the parasite were detected 2 days after inoculation. Parasite-specific antibody titers were demonstrable 7 days after inoculation with oocysts and achieved peak levels 9 days after inoculation, coinciding with oocyst shedding at 5 to 10 days after inoculation. Both lymphocyte and antibody responses remained elevated until the termination of the experiment. Immunoblotting the C. parvum preparation with serum from an infected calf revealed six major parasite antigens. Five of these antigens reacted on immunoblots from 7 to 14 days after inoculation with oocysts. A parasite antigen of approximately 11,000 molecular weight demonstrated intense reactivity on immunoblots from 7 to 23 days after inoculation. The 11,000-molecular-weight antigen also reacted on immunoblots with parenterally raised antioocyst and antisporozoite rabbit sera. These results indicate that cell-mediated as well as humoral immune responses are initiated by cryptosporidial infection in calves and that the 11,000-molecular-weight parasite antigen is immunodominant.

Quantitation of antibody reactivity to human immunodeficiency virus (type 1) proteins and glycoproteins on Western immunoblots by reflectance densitometry

The human serum antibody response to polypeptides of human immunodeficiency virus type 1 (HIV-1) was quantitated by reflectance densitometry of Western immunoblots by using two commercially available blotting systems. In one system, human antibodies were detected by an avidin-biotin method using peroxidase as the label, and in the other, human antibodies were detected by peroxidase-labeled conjugate against human immunoglobulins. When staining intensity was plotted against the log of the serum dilution, a shallow slope was evident, with a 50% change in staining intensity requiring as much as a 100-fold change in antibody content. The linear range of the staining intensity curves was frequently found in serum dilutions of 1:2,500 to 1:1,000,000, and a plateau was often observed at high antibody concentrations (1:80 to 1:640). When replicate strips were tested, staining intensities varied by +/- 7 to 37%. Antibodies to p24gag and gp160env were readily detectable in several sera diluted 1:1,000,000, a result seen with both blotting systems. If Western blotting were to be used to observe increase or decreases in levels of antibodies to various polypeptides, several widely spaced serum dilutions would need to be tested.

Enzyme-linked immunoassay for detection of Cryptosporidium antigens in fecal specimens

Cryptosporidium sp. is a ubiquitous 4- to 6-micron protozoan parasite infecting the intestinal tract of humans. It causes mild to fulminant diarrhea in patients, especially immunocompromised persons, and it may be hard to detect by microscopic fecal examination. An indirect, double-antibody enzyme-linked immunosorbent assay (ELISA) was developed using specifically produced goat and rabbit antisera to detect Cryptosporidium antigens in human feces. Of 62 frozen stools from patients with cryptosporidiosis, as detected by at least two microscopic diagnostic techniques, 51 were positive by ELISA; all ELISA-negative specimens came from patients with fewer than five oocysts per 0.01 ml of concentrated fecal sample examined after modified acid-fast or fluorescent monoclonal antibody staining. A total of 182 specimens from persons without Cryptosporidium infection were negative by ELISA in 176 instances; 3 ELISA-positive specimens came from patients with cryptosporidiosis diagnosed earlier. The sensitivity of the assay was 82.3%, and specificity was 96.7%. The predictive value of a positive ELISA was 89.5%, and the predictive value of a negative ELISA was 94.2%. The ELISA was not affected by the presence of eight other intestinal parasites but was sometimes affected by repeated freezing and thawing of fecal specimens. All fecal specimens were heated to 100 degrees C for 2 min to reduce proteolytic enzyme activity, although the necessity of this step needs further evaluation. This first-generation ELISA is a simple, rapid, easily standardized test for Cryptosporidium antigens in stool samples which will be useful for diagnosis and for large-scale epidemiologic studies.

Cryptosporidium parvum (Apicomplexa: Cryptosporidiidae) oocyst and sporozoite antigens recognized by bovine colostral antibodies

Colostral whey from seven hyperimmunized and two control cows (hyperimmune bovine colostrum) was examined by Western immunoblotting for the presence of antibody against oocysts and sporozoites of Cryptosporidium parvum, using rabbit anti-bovine immunoglobulin A (IgA), IgG1, IgG2, and IgM antibodies, followed by a horseradish peroxidase goat anti-rabbit polyvalent antibody. Although considerable variation was found in binding activity between cows on different immunization protocols, IgA and IgG1 in whey recognized a greater variety of C. parvum antigens than did IgG2 and IgM. A band at 9 to 10 kilodaltons appeared unique in that it was recognized only by IgA.

Cryptosporidiosis and AIDS

Cryptosporidiosis in patients with AIDS presents as a chronic enteritis, with biliary complications in about 10% of sufferers. The disease is persistent and progressively fatal. Due to the widespread prevalence of the parasite in the community and amongst domesticated animals, persons with AIDS are constantly at risk. Treatment is extremely difficult in view of the apparent lack of a specific anticryptosporidial drug. Methods of immunomodulation are worth considering, but the main recourse may have to be a prolonged regimen of rehydration and parenteral nutrition. However, if T helper cell function improves, the disease may go into remission or the parasite could be eliminated. Vaccination of those at risk is not feasible at present.

Epidemiological aspects of human cryptosporidiosis

The coccidian protozoan parasiteCryptosporidiumhas been described in many host species since its discovery in the early part of the century, but it remained obscure until the recognition by veterinary workers in the 1970s of its importance as a cause of scours in young livestock animals [1–4].

Localization of a 23,000 MW antigen of Cryptosporidium by immunoelectron microscopy

Rabbit antiserum was raised against a 23,000 molecular weight (MW) antigen prepared from Cryptosporidium oocysts by electro-elution from polyacrylamide gels. The antiserum was tested for specificity by immunoblotting against solubilized oocyst preparations. Several antigens including the 23,000 MW antigen were recognized suggesting that it shared common epitopes with higher MW proteins. The antiserum was then used in conjunction with a protein A-colloidal gold conjugate to locate antigenic sites within exogenous and endogenous developmental stages of Cryptosporidium. The pellicles of both sporozoites and merozoites exhibited specific labelling, particularly around their anterior ends. No specific labelling was observed for any other membrane determinants or organelles in these or other life cycle stages.

Effects of immune colostrum and orally administered antisporozoite monoclonal antibodies on the outcome of Cryptosporidium parvum infections in neonatal mice

A neonatal BALB/c mouse model of cryptosporidiosis was used to examine the potential passive transfer of immunity via immune colostrum and oral treatment with anticryptosporidial monoclonal antibodies. Neonates suckled by dams that recovered from Cryptosporidium parvum infections were equally susceptible to infection as their control counterparts suckled by naive dams. Parasite loads among the control and immune colostrum-fed mice were indistinguishable. Neonates receiving orally administered antisporozoite monoclonal antibodies were equally susceptible to infections compared with the control and immune colostrum-fed mice. Parasite loads among the mice receiving daily oral treatment with monoclonal antibody mixtures exhibited significantly lower parasite loads compared with the control mice (P less than 0.05).

Electrophoretic and immunoblot analysis of Cryptosporidium oocysts

Cryptosporidium oocysts were recovered by density gradient centrifugation from diarrhoeal faeces of four human patients and one goat kid. Goat-derived oocysts were further treated with excystation medium and the excysted oocyst walls purified by isopycnic ultracentrifugation. Soluble extracts from intact oocysts and the oocyst wall preparation were analysed by SDS-PAGE. Fifty-one polypeptide bands were detected in intact oocyst preparations: 48 were in the range 14,000-200,000 molecular weight (MW), two bands were less than 14,000 MW and one band was above 200,000 MW. Twenty-one bands were detected in the oocyst wall preparation, all within the range 14,000-200,000 MW. Immunoblot analysis of Cryptosporidium polypeptides using acute or convalescent human and goat sera revealed a large number of reactive bands. Varying degrees of heterogeneity were observed within and between the two serum groups. Nine of the 10 human sera and all of the goat kid sera reacted with a 23,000 MW and 32,000 MW antigen. A 15,500 MW antigen was also detected by all the goat and four of the 10 human sera. Both serum groups reacted with various antigens above 40,000 MW. Surface labelling of three human isolates of Cryptosporidium oocysts with 125I was performed using the Bolton and Hunter reagent. The solubilized preparations were separated by SDS-PAGE on 12% and 18% slab gels and autoradiographed. Common bands were seen at 15,500, 32,000, 47,500, 79,000 and 96,000 MW. Some variation in the molecular weight of polypeptides labelled with 125I was observed among the three isolates.(ABSTRACT TRUNCATED AT 250 WORDS)

Development of and serologic evaluation of acquired immunity to Cryptosporidium baileyi by broiler chickens

Eighteen 2-wk-old broiler chickens that were inoculated orally with oocysts of Cryptosporidium baileyi (Group B) became infected, shed large numbers of oocysts in their feces on Days 6 to 12 post inoculation (PI), and suddenly cleared the parasites from the mucosal epithelium of the bursa of Fabricius (BF), cloaca, or both BF and cloaca on Days 14 to 16 PI. Eighteen uninoculated birds (Group A) did not shed oocysts during this time period. Five days after all birds in Group B stopped shedding oocysts, the 36 chickens comprising both groups were challenged orally with C. baileyi oocysts. At the time of necropsy, 10 days after oral challenge, all Group A birds (previously uninfected, challenged) had heavy C. baileyi infections in the mucosal epithelium of the BF or cloaca. No parasites were found in the BF or cloaca of the Group B birds (previously infected, recovered, challenged) at the time of necropsy. These data demonstrate that a single intestinal infection with C. baileyi can elicit an immune response of sufficient magnitude to clear the parasite from the intestinal (BF and cloaca) mucosa and to make broiler chickens resistant to subsequent oral challenge with oocysts of the same species. Development of resistance to reinfection was accompanied by the appearance of serum antibodies to C. baileyi that were detectable by two Cryptosporidium-specific assays; an indirect immunofluorescent antibody assay and an enzyme-linked immunosorbent antibody assay (ELISA). The ELISA described herein can now be incorporated into serologically based health monitoring programs.

Lacteal immunity to enteric cryptosporidiosis in mice: immune dams do not protect their suckling pups

The susceptibilities of passively immunized principal and nonimmunized control suckling mice to orogastric challenge with Cryptosporidium parvum oocysts were compared. Principals were suckled by dams that had recovered from C. parvum infection. Controls were suckled by dams reared free of C. parvum infection. Principals and controls were equally susceptible to challenge. Principals were susceptible even when their dams were hyperimmunized by oral and parenteral booster inoculations with C. parvum oocysts. Immune dams produced serum antibody against C. parvum, while nonimmune dams did not. Anti-cryptosporidia immunoglobulin G (IgG) and IgA were demonstrated in whey extracted from the stomachs of principals that had suckled immune dams but not in whey extracted from the stomachs of controls. It was concluded that passive lacteal immunity is not an efficient means of protection against cryptosporidiosis in mice. As in other coccidian infections, protective immunity against cryptosporidiosis may depend more on immune cells than on antibody.

Quantification of immunoglobulin on electrophoretic immunoblot strips as a tool for human immunodeficiency virus serodiagnosis

Electrophoretic immunoblotting (EIB [Western blotting]), the main method for verification of human immunodeficiency virus (HIV) seropositivity, needs thorough characterization and standardization. We explored the possibilities of quantifying immunoglobulin G (IgG) bound to EIB strips both by densitometry of the peroxidase-stained bands and by measurement of radioactivity with labeled anti-HIV IgG. The radioactivity method is inherently more exact but was more cumbersome. However, despite saturation phenomena at high IgG densities, the densitometric method was more convenient and yielded reproducible estimates of the amount of bound IgG. We found it useful primarily for documentation of changes in the relative abundance of antibodies to different HIV proteins from individual patients over time. To explore the potential usefulness of the method, we studied a small set of HIV-seropositive persons. The average p24/gp41 color yield ratios and standard deviations in 3 persons with recent seroconversion, 15 healthy subjects, and 6 diseased HIV-seropositive persons were 6.6 +/- 0.9, 2.3 +/- 1.9, and 1.3 +/- 0.5, respectively. These data are in accord with previous qualitative or semiquantitative observations but are too limited for any conclusions regarding the use of quantitative EIB for prognostic use with individual patients. Quantitative EIB is a valuable tool for comparative methodological studies and for research on the protective role of anti-HIV antibodies in acquired immunodeficiency syndrome pathogenesis. Its possible use in prognostication for individual patients must be evaluated in long-term studies.