Identification of a subpopulation of immune Nigerian adult volunteers by antibodies to the circumsporozoite protein of Plasmodium falciparum

Collections of human sera from malaria-endemic areas would be valuable for identifying and characterizing antigens as malaria vaccine candidates if the contributing serum donors' ability to resist infection were fully characterized. We prepared such a serum collection from 26 apparently immune Nigerian adults who failed to develop patent parasitemia for at least 20 weeks following a documented increase in antibodies to the circumsporozoite protein (CSP) from Plasmodium falciparum. Volunteers were evaluated five times per week for malaria symptoms and bimonthly for parasites by examining thick blood smears. The incidence rate over 13 months for the cohort was 42% (47 malaria-confirmed volunteers) and the risk of infection was 1.3 infections/year. Responses to CSP did not correlate with protection. Because antibody responses to antigens other than CSP may be associated with protection, the sera from these immune individuals may be useful for identifying and characterizing other potential malaria vaccine candidates.     

Protection of chickens with or without maternal antibodies against both Marek's and Newcastle diseases by one-time vaccination with recombinant vaccine of Marek's disease virus type 1

We constructed a stable recombinant Marek's disease virus type 1 (rMDV1) expressing the fusion protein (F) of Newcastle disease virus (NDV) by inserting the coding sequence within the US10 gene of MDV1 by homologous recombination and designated this as rMDV1-US10L(F). The NDV-F protein was significantly expressed under control of the SV40 late promoter in cultured cells infected with the rMDV1. To examine the protective efficacy of the rMDV1, specific pathogen-free (SPF) chickens were vaccinated with rMDV1 at one-day-old. Almost all birds (> 95%) were protected from NDV challenge via intramuscular, ocular, intranasal and intratrachial routes at 4 weeks after vaccination. The rMDV1 showed 100% protection against virulent MDV1 challenge in SPF chickens. Antibody responses against NDV-F and MDV1 antigens were observed at least up to 11 weeks after immunization. When the sera from chickens vaccinated with the rMDV1 were examined for the presence of anti-NDV-F antibody on the day of NDV challenge, the vaccinated bird group which did not survive from NDV challenge were found to show lower antibody titers than the surviving group. The rMDV1 also provided sufficient protection against NDV and MDV1 challenges in commercial chickens with maternal antibodies against NDV-F and MDV1 antigens.     

Immunoglobulin A response in murine schistosomiasis: stimulatory role of egg antigens

The immunoglobulin G (IgG) and IgA antibody responses to different Schistosoma mansoni antigens have been determined in chronically infected mice as well as in unisexually infected animals. With a panel of enzyme-linked immunosorbent assays (ELISAs), soluble antigens from furcocercariae, adult worms, and eggs were probed with sera collected at 3-week intervals. Bisexually infected animals developed significant IgG and IgA antibody responses to the antigens tested, which increased after egg deposition. In unisexual infections no significant differences were recorded in the IgG antibody profile for furocercaria and adult worm antigens, whereas the IgA antibody response was impaired. Both the IgA and IgG antibody responses toward egg antigens were reduced compared with those in a bisexual infection. Furthermore, a specific mucosal IgA antibody response was observed only in the bisexually infected animals. Histological analysis performed on bisexually infected mice led to the observation of eggs and granulomatous lesions within the Peyer's patch follicles, which are essential sites for the induction of mucosal immunity in the intestine. These data suggest a relationship between egg deposition and the induction of the IgA antibody response toward schistosomes.     

Qualitative and quantitative analysis of the local and systemic antibody response in mice and humans with Helicobacter immunity and infection

Immunization can prevent or cure an otherwise chronic gastric Helicobacter infection in several different animal models. The goal of the present study was to compare the titers and specificities of local and systemic antibody responses generated by Helicobacter infection and immunization. Protective immunization results in levels of specific gastric antibody significantly lower than induced by infection. However, antibodies from protectively immunized mice preferentially recognize immunodominant proteins of 10-22 and 30 kDa. Immunoblot analysis of infected mice and humans demonstrated that the serum IgA, but not serum IgG, binding profiles yield an accurate profile of the antigenic specificity of the host's gastric IgA. Therefore, serum IgA may be useful in evaluating the immunodominant antigens at the gastric mucosa of infected persons and possibly in determining the immunogenicity of orally applied Helicobacter vaccines.     

Somatic antigens of adult Dicrocoelium dendriticum recognised by bile antibodies of naturally infected cattle

Bile samples, from slaughtered cattle harbouring between 120 and 280 adult lancet flukes, were used to investigate the range of somatic proteins inducing local antibody responses in naturally infected animals. Lancet fluke infections induced local (bile) antibody responses against Tris-buffered saline (TBS) soluble, sodium dodecyl sulphate (SDS) soluble and 2-mercaptoethanol (2-Me) soluble somatic proteins of adult Dicrocoelium dendriticum. IgA antibody isotypes predominated in the response against buffer-soluble somatic antigens, whereas SDS-soluble and 2-Me-soluble proteins induced similar level of both IgA and IgG1 antibodies. Analysis of the antigens recognised by particular isotype-specific bile antibodies suggests that different antigens preferentially induce isotype restricted antibody responses. The bile antibody response was highly species specific, only one antigen from somatic protein extracts of Fasciola hepatica being precipitated by bile samples showing the highest reactivity against D. dendriticum.     

Axonal transection in the lesions of multiple sclerosis

We explored the relationship between mutans streptococcal infection and the development of salivary IgA antibody during initial colonization. Repetitive swabbing (n = 292) of the teeth of 33 children revealed that 45% became infected with mutans streptococci between 13 and 36 months of age. In contrast, mutans streptococci could not be detected in 18 children whose last sample was taken at 39-81 months of age (median age = 62 months). During the period of mutans streptococcal infectivity, immunoglobulin A (IgA) antibody to several mutans streptococcal antigens appeared in most children, whether or not infection had been demonstrated. Robust responses to mutans streptococcal components occurred during or shortly after, but not before the period of mutans streptococcal infectivity. No consistent differences were observed among the summarized patterns of response of infected and uninfected groups of children, although the IgA Western blot patterns of individual subjects were often quite distinct. For example, sets of siblings, who would be presumed to be challenged with similar maternal mutans streptococcal clonotypes, were shown to develop qualitatively different salivary IgA responses to mutans streptococcal components. These results support a discrete period for mutans streptococcal infection and may suggest that the level of maternal infection is a factor in the success of infection of the child during this period. The data also suggest that exposure to mutans streptococci is a sufficient condition for robust mucosal IgA responses to mutans streptococcal antigens during the period of infectivity and that these responses may be different, even among siblings.     

IgE antibody during infection with the ovine abomasal nematode, Teladorsagia circumcincta: primary and secondary responses in serum and gastric lymph of sheep

A monoclonal antibody to ovine IgE was employed in an ELISA to investigate the IgE antibody responses in serum and gastric lymph to a primary infection of Teladorsagia circumcincta, and following challenge in previously infected sheep. During a primary response, IgE antibody to antigens derived from the infective third stage (L3) and adult (L5) worms were negligible, with low levels of IgE antibody detected in serum and lymph. In contrast, there was a pronounced IgE antibody response in 2/4 sheep to L3 antigens during 2-8 days after challenge of previously infected animals but low levels of IgE antibody to L5 antigens. This response was confirmed in a second but similar experiment, where relatively high levels of IgE antibody was detected to antigens from L3. Antibody levels were higher in lymph than in serum from the same animals, and Western blots of L3 antigen following SDS-PAGE under reducing conditions revealed several bands of MW26-96KD which reacted with the IgE antibody from gastric lymph. Immunohistochemical staining indicated that these IgE antibodies may be reacting with allergens associated with the surface cuticle of the worms.     

Enzyme-linked immunosorbent assay for measuring ileal symbiont intracellularis-specific immunoglobulin G response in sera of pigs

Proliferative enteritis (PE) is a common intestinal disease on pig farms. The disease is caused by ileal symbiont (IS) intracellularis (Campylobacter-like organisms) bacteria. An enzyme-linked immunosorbent assay (ELISA) was developed to measure IS intracellularis-specific immunoglobulin G (IgG) response in the sera of pigs. The antigen used in the ELISA was filtered, percoll gradient-purified IS intracellularis extracted from the intestines of pigs affected with proliferative hemorrhagic enteropathy. The antibody responses of pigs challenged with intestinal homogenates from pigs affected with proliferative hemorrhagic enteropathy containing IS intracellularis or percoll-gradient purified IS intracellularis were low and variable. The low IgG titers measured in challenged pigs support previous findings that IgG plays a minor role in the immune response of pigs to IS intracellularis. On a farm in which infection was endemic, pigs seroconverted at between 7 and 24 weeks of age. High IgG titers, indicative of maternally acquired antibody, were present in 3-week-old pigs. The IgG titers in piglets were lowest at 6 weeks of age, which approximates the age of onset of clinical disease. These results suggest that IgG plays a role in determining the susceptibilities of pigs to natural infection. Measurements of seroconversion by the ELISA might aid in epidemiological investigations of PE in naturally infected herds. However, the variable antibody responses in experimentally challenged pigs would seem to limit its usefulness as an antemortem diagnostic test for PE.     

Detection of serum antibody responses in cattle with natural or experimental Neospora infections

Parasite-specific antibody responses were detected using an indirect fluorescent antibody (IFA) test in cattle that were naturally or experimentally infected with Neospora parasites. The test was developed using Neospora tachyzoites isolated from an aborted bovine fetus and grown in bovine cell cultures (isolate BPA1). In all cases, infections were confirmed by the identification of Neospora tachyzoites and/or bradyzoite cysts in fetal or calf tissues using an immunoperoxidase test procedure. Fifty-five naturally infected cows that aborted Neospora-infected fetuses had titers of 320-5,120 at the time of abortion. The titer of 6 cows that were serologically monitored over a prolonged period decreased to 160-640 within 150 days after they aborted infected fetuses. Two of the cows showed an increase in their Neospora titers during their subsequent pregnancy, and they gave birth to congenitally infected calves that had precolostral titers of 10,240-20,480. Postcolostral titers of these calves and of 4 other calves with congenital Neospora infections were all > or = 5,120, whereas calves with no detectable parasites had titers < or = 160. Two pregnant heifers that were experimentally infected with the BPA1 isolate at approximately 120 days gestation seroconverted to Neospora antigens within 9 days and developed peak titers of 5,120 and 20,480 within 32 days of infection. The fetus taken by caesarean section 32 days postinfection from 1 heifer and the full-term calf born to the other had Neospora titers of 640 and 10,240, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of levamisole on cellular immunity in multiple sclerosis

The lymphocyte stimulation test has been standardized in a normal human population using four virus cell-associated antigens (VCAA): human embryonic lung cells infected with the LEC and Norrby strains of measles virus, mumps virus, and vaccinia virus. Following 1 week of treatment with the immunopotentiating drug levamisole, a group of multiple sclerosis (MS) patients was found to have increased lymphocyte stimulation responses toward VCAA and increased delayed hypersensitivity responses towards a battery of skin test antigens. No change in the percentage of short- or long-incubation E rosettes occurred. Measles haemagglutinin inhibition (HI) antibody titres measured before and after the entire course of levamisole therapy (12 weeks) did not change. The neurological status of five out of seven MS patients deteriorated while they were taking levamisole.     

Serological association between spirorchidiasis, herpesvirus infection, and fibropapillomatosis in green turtles from Florida

Serodiagnostic tests for detecting green turtle (Chelonia mydas) antibody responses were developed to test the strength of association between exposure to spirorchid trematode antigens or herpesvirus antigens and having green turtle fibropapillomatosis (GTFP). Plasma samples from 46 captive-reared green turtles, including paired pre- and 1-yr post-inoculation samples from 12 turtles with experimentally induced GTFP, were found by enzyme-linked immunosorbent assay (ELISA) to be negative for antibodies to adult spirorchid (Learedius learedi) antigens. In contrast, all 12 turtles that developed experimentally induced GTFP converted within 1 yr from having negative to positive antibody reactivity to GTFP-associated herpesvirus antigens, whereas the three controls and four turtles that failed to develop tumors remained negative. Plasma samples from 104 free-ranging green turtles from two Florida (USA) coastal feeding grounds with different GTFP prevalences were tested by ELISA for antibodies to L. learedi adult antigens; and there was no statistically significiant association between antibody prevalence and sampling site. When a low optical density cutoff value (0.15) was used to interpret ELISA results, 98% of the turtles from each site were spirorchid antibody-positive and there was no association between antibody reactivity to spirorchids and GTFP status. When a higher negative cutoff value was used, however, a statistically significant association between antibody reactivity to spirorchids and GTFP-free status was found. These results suggest that spirorchids do not have a role in GTFP pathogenesis. All 20 of the tumor-bearing lagoon turtles had antibodies to herpesvirus antigens whereas only two (10%) of the tumor-free reef turtles had detectable anti-herpesvirus reactivity. The strong association between antibody reactivity to herpesvirus antigens and GTFP status in both captive-reared and free-ranging turtles is consistent with the hypothesis that the transmissible agent that causes GTFP is a herpesvirus.     

Variations of the frontal exit of the supraorbital nerve: an anatomic study

Meningeal worm (Parelaphostrongylus tenuis) is a neurotropic nematode of ungulates in eastern North America. Lack of an effective diagnostic test increases the concern of translocating potentially infected ungulates into western North America, where P. tenuis does not occur naturally. In an attempt to identify serodiagnostic molecules, we determined (1) whether elk (Cervus elaphus) experimentally infected with P. tenuis produce antibodies against infective larvae or adult worms, and (2) if sera consistently recognize antigens that distinguish P. tenuis from a common nematode parasite of elk, the lungworm Dictyocaulus viviparus. Each of 10 elk were exposed to 15 or 300 infective P. tenuis larvae. Serum was collected (0, 41, and 83 days post-exposure and at necropsy) and monitored for antibodies using the enzyme-linked immunosorbent assay (ELISA) and immunoblot. When reactivity of sera with larval P. tenuis protein was compared (day 0 versus 83), ELISA values were significantly higher on day 83 for elk exposed to 15 or 300 parasites. Likewise, ELISA values using protein of adult P. tenuis were higher for elk exposed to 300 larvae. Immunoblots showed that sera from elk, with adult worms in the central nervous system, consistently recognized the 25-27, 28-30, and 34-36 kDa antigens of infective larvae after 83 days. However, many D. viviparus molecules were found to cross-react with antibodies formed against meningeal worm antigens. Use of adult worm proteins for serodiagnosis appears limited, because no protein was consistently recognized by sera collected from elk exposed to 15 larvae. We believe that development of a reliable diagnostic test for meningeal worm requires more research addressing cross-reactivity and detection of P. tenuis during the incubation stage.     

Isolation and identification of chicken infectious anemia virus in China

A chicken infectious anemia virus (CIAV) isolate was obtained from broiler flocks aged 25-40 days with anemia and poor performance and was designated SR43. The CIAV isolate was resistant to treatment with chloroform and induced thymus atrophy, bone marrow aplasia, and low hematocrit values when inoculated into 1-day-old, susceptible, specific-pathogen-free chicks. CIAV-specific antigens could be demonstrated in SR43-infected MDCC-MSB-1 cells, a cell line derived from a Marek's disease lymphoma, with the use of a monoclonal antibody specific for CIAV. CIAV DNA in infected MDCC-MSB-1 cell cultures was detected by using a polymerase chain reaction assay. These findings demonstrate that CIAV is present in China.     

Immunosuppression in paracoccidioidomycosis: T cell hyporesponsiveness to two Paracoccidioides brasiliensis glycoproteins that elicit strong humoral immune response

To assess human cellular immune response to paracoccidioidomycosis (PCM), lymphocyte proliferative responses to purified antigens from Paracoccidioides brasiliensis were determined in healthy persons previously infected by the fungus (positive donors), in healthy noninfected persons (controls), and in PCM patients. Affinity-purified gp70 and gp43, the two major antigens in humoral immune responses, were used. Both induced lymphocyte proliferation (gp43 species-specific) in positive donors but not in controls; healthy persons previously infected by Histoplasma capsulatum reacted to gp70 and not to gp43. A similar cross-reactivity in antibody response to gp70 was previously reported; however, antibody response to gp43 has been considered specific. Lymphocytes from PCM patients, who, unlike positive donors, have high levels of anti-gp43 and anti-gp70 antibodies, proliferated poorly with gp70 and gp43 but better with other stimuli. This dichotomy between humoral and cellular antigen-specific responses suggests a Th2 immune response in PCM, which may be related to failure to control the infection.     

Serological diagnosis of influenza B virus infection: comparison of an enzyme-linked immunosorbent assay and the hemagglutination inhibition test

The sensitivity of an enzyme-linked immunosorbent assay (ELISA) for the detection of antibody to influenza B virus was compared with that of the hemagglutination inhibition test on acute- and convalescence-phase sera obtained from adults and children infected with influenza B virus. Two whole virus, tissue culture-grown antigen preparations were used in the ELISA, influenza B/West Virginia/81 and influenza B/Hong Kong/72. Four antigens were used in the hemagglutination inhibition test. These included the tissue culture-grown whole virus antigens that were used in the ELISA. In addition the standard egg-grown antigens, influenza B/Singapore/79 and influenza B/Hong Kong/72, were included for comparison. The ELISA antibody titer was significantly correlated to the hemagglutination inhibition antibody titer, and 10 of 10 adults and 17 of 21 children infected with influenza B had fourfold antibody increases as detected by ELISA with either antigenic type of tissue culture-grown whole virus. Increases in geometric mean antibody titers of 16- to 71-fold were detected by ELISA. Increases in geometric mean antibody titers of 3- to 10-fold were detected by hemagglutination inhibition depending on the type of antigen utilized. We found that ELISA with whole virus antigens was a sensitive and specific test for the detection of antibody to influenza B virus.     

Haemophilus ducreyi elicits a cutaneous infiltrate of CD4 cells during experimental human infection

Human subjects were experimentally infected with Haemophilus ducreyi for up to 2 weeks. Bacterial suspensions were delivered into the epidermis and dermis through puncture wounds made by an allergy-testing device. Subjects developed papular lesions that evolved into pustules resembling natural disease. Some papular lesions resolved spontaneously, indicating that host responses may clear infection. Bacteria were shed intermittently from lesions, suggesting that H. ducreyi may be transmissible before ulceration. Host responses to infection consisted primarily of cutaneous infiltrate of polymorphonuclear leukocytes, Langerhans cells, macrophages, and CD4 T cells of alpha beta lineage. Expression of HLA-DR by keratinocytes was associated with the presence of interferon-gamma mRNA in the skin. There was little evidence for humoral or peripheral blood mononuclear cell responses to bacterial antigens. The cutaneous infiltrate of CD4 cells and macrophages provides a mechanism that facilitates transmission of human immunodeficiency virus by H. ducreyi.     

The use of monoclonal antibody for the immunodiagnosis of Fasciola gigantica infection in cattle

Antigens that were specific to Fasciola gigantica were obtained from the whole worm homogenate of the parasite by immunoaffinity chromatography in cyanogen bromide-activated sepharose 4B columns and used for the production of monoclonal antibodies. The F. gigantica-specific monoclonal antibody was labelled with horseradish peroxidase and used for the detection of circulating antigen by the direct ELISA method in the sera of cattle experimentally infected with the parasite. Circulating antigens were detectable in the sera of the animals as from the third week after infection while negative absorbance values were obtained 2 weeks after the termination of the infection by chemotherapy with oxyclozanide. This immunodiagnostic method offers an attractive alternative as a supplement to the conventional coprological diagnosis of fasciolosis.     

Application of equine infectious anemia virus core proteins produced in a baculovirus expression system to serological diagnosis

Equine infectious anemia virus (EIAV) core proteins were obtained from a baculovirus expression system. Recombinant baculoviruses (rBVs) highly expressed the Gag precursor and p26 antigens in an rBV-infected Sf21 cell culture supernatant. Enzyme-linked immunosorbent assay (ELISA) and agar gel immunodiffusion (AGID) were conducted using the expressed proteins to detect antibodies from experimentally infected horses. The expressed antigens showed low background levels, high specificity and sensitivity in ELISA and AGID. The results of the serological tests using the expressed antigens were identical to those using a manufactured trial antigen. rBVs containing gag and p26 genes were found to express high quality and large quantities of Gag and p26 antigens, respectively. The antigens were quite useful for detecting anti-EIAV antibodies from virus-infected horses.     

Serologic responses of young colostrum fed dairy calves to antigens of Pasteurella haemolytica A1

The potential and limitations of early calfhood vaccination to induce active immunity to Pasteurella haemolytica A1 in conventional colostrum fed calves were investigated. Holstein dairy calves (n = 29) were vaccinated at 2 and 4 weeks of age, or at 6 and 8 weeks of age with a commercial culture supernatant vaccine (Presponse, Langford Inc., Guelph, Ont., Canada), or remained unvaccinated as controls. Serum antibody titres were measured using an indirect bacterial agglutination assay, a leukotoxin neutralization assay, and enzyme immunoassays for antibodies of the IgM, IgG1, and IgG2 isotypes binding purified capsular polysaccharide of P. haemolytica A1. Seroconversion (fourfold or greater increase in serum antibody titre) rates were compared using Fisher's exact test. The effects of passive antibody titres and age on response to vaccination were assessed by linear modelling. Vaccination at 2 and 4 weeks of age was associated with 40%, and 0% of calves seroconverting on the basis of agglutinating antibody titres, and leukotoxin neutralizing titres respectively, and 50%, 0%, and 0% seroconverting on the basis of IgM, IgG1 and IgG2 antibodies to capsular polysaccharide, respectively. Agglutinating antibody responses were not related to prevaccination antibody titres, or to age at vaccination. Higher responses (p = 0.08) to leukotoxin were observed in older calves (after taking differences in prevaccination titres into account). Statistical analyses of responses to capsular polysaccharide among calves with comparable prevaccination IgG1 antibody titres revealed significantly higher IgM, IgG1 and IgG2 responses in older calves. Rising titres of IgM antibodies in nonvaccinated calves after 5 weeks of age suggest natural exposure to P. haemolytica A1 or antigens which result in serologic cross-reactions as a means of priming immune responses.