Detection of specific antibodies in cats infected with the lung nematode Aelurostrongylus abstrusus

Feline aelurostrongylosis, caused by the metastrongylid nematode Aelurostrongylus abstrusus, is an underestimated respiratory parasitosis. Its diagnosis currently mainly relies on the isolation of first stage larvae from fresh faecal samples. The aim of our study was to develop a serological test for the detection of specific antibodies against A. abstrusus by ELISA. We used recombinant major sperm protein (MSP) of the bovine lungworm Dictyocaulus viviparus as detection antigen and evaluated two different ELISA plates (Maxisorp and Immobilizer™ Amino-plate, Nunc Roskilde, Denmark) with two different enzyme systems [alkaline phosphatase (AP) and horseradish peroxidase (HRP)]. Sera from cats experimentally (n=54) and naturally (n=17) infected with A. abstrusus and from randomly selected cats with different medical issues (n=160) were used to determine sensitivity and specificity. Furthermore, cross-reactions were evaluated using sera from cats naturally (n=71) and experimentally (n=8) infected with different nematodes. A sensitivity of 100% was obtained with sera from experimentally infected cats at 10 weeks post infection using MSP on the Immobilizer™ Amino-plate with HRP, while it ranged between 90.5 and 95.2% in the other ELISA set-ups. Using sera from naturally infected cats, a sensitivity of 88.2% (95% confidence interval: 63.6-98.5%) was achieved in all four set-ups. The specificity was 85.2-94.4% in sera from uninfected cats prior to experimental infection and 68.1-90% in randomly selected cats depending on the plate and enzyme system. The number of seropositive cats increased over time post infection. Serological follow-up showed a decrease of antibody levels within 30days after anthelmintic treatment. Seropositive reactions were observed with sera from stray cats naturally infected with Toxocara cati, Capillaria sp., hookworms and Taeniidae; however, coproscopic false negative A. abstrusus findings cannot be excluded. The serological detection of specific antibodies against A. abstrusus using ELISA requires a single serum sample and therefore represents a valid alternative for reliable individual diagnosis of A. abstrusus in cats and facilitates mass screening, overcoming the usually difficult collection of cat faeces.

IMMUNOGLOBULIN RESPONSES OF NORTHERN ELEPHANT AND PACIFIC HARBOR SEALS NATURALLY INFECTED WITH OTOSTRONGYLUS CIRCUMLITUS

Immunoglobulin (Ig) binding patterns of Pacific harbor seals (PHS, Phoca vitulina richardsi) and northern elephant seals (NES, Mirounga angustirostris) to tissues of adult Otostrongylus circumlitus were examined by immunoblotting to investigate the role of age in the unusual response of juvenile NES to infection with O. circumlitus. Serum was taken from NES between March 1997 and March 2001 and from PHS between May 1996 and August 1999. The serum of seals infected with O. circumlitus contained antibodies that bound to all nematode tissues examined. Intensity of band staining on Western blots suggested that there were higher levels of antibody recognizing the excretory-secretory (ES) glands in the serum of NES that were 1 yr and older and in the majority of PHS compared with that in 2- to 9-mo-old NES. All juvenile NES infected with O. circumlitus and a proportion of the PHS and older NES infected with O. circumlitus contained Ig specific to a 28 kDa protein band that was dominant in the female reproductive tract of the nematode. The Ig binding patterns of NES and PHS to adult Parafilaroides sp., larval Pseudoterranova sp., and larval and adult Anisakis sp. differed sufficiently from that of O. circumlitus that immunoblotting for the 28 kDa protein could be useful for diagnosis of this parasite in juvenile NES. The banding patterns suggest that O. circumlitus nematodes die and disintegrate in PHS and NES and that NES of 1 yr and older and most PHS respond differently to the ES glands than 2- to 9-mo-old NES.

ESTABLISHMENT OF ADULT PARELAPHOSTRONGYLUS TENUIS, PATENT INFECTIONS, AND ACQUIRED IMMUNITY AFTER EXPERIMENTAL INFECTION OF WHITE-TAILED DEER (ODOCOILEUS VIRGINIANUS) AND RED DEER (CERVUS ELAPHUS ELAPHUS)

Experimental Parelaphostrongylus tenuis infections were established in white-tailed deer (Odocoileus virginianus) and an atypical host, red deer (Cervus elaphus elaphus). Groups of deer were fed 10, 25, or 100 third-stage larvae (L3) of P. tenuis and received a single equivalent challenge exposure at varying intervals. Infections were monitored up to 6 yr in white-tailed deer and up to 2.8 yr in red deer. The prepatent period in white-tailed deer varied from 91 to 1,072 days (381 +/- 374) and in red deer from 105 to 358 days (167 +/- 77). Adult worms lived for up to 6 yr in white-tailed deer. Although most had patent infections until necropsy, latent periods were observed regardless of season. Adult worms lived for up to 2.8 yr in red deer, and patent infections persisted for 20-363 days (152 +/- 106). Patent infections were correlated with the presence of adult worms in blood vessels and sinuses of both deer species. Worms were restricted to the subdural space in all deer with latent and occult infections. Adult worm recovery in white-tailed deer fed 10 or 25 L3 corresponded to the mean intensities reported in natural infections of white-tailed deer Recovery from deer fed 100 L3 was not typical of natural infection intensities. Adult P. tenuis established in all groups of red deer, but neurologic disease was restricted to animals fed 100 L3. Acute neurologic disease was associated with subdural hemorrhage and occurred at 11 mo postinfection in 2 red deer. The absence of postchallenge patent periods and the persistence of occult infections indicated that challenge exposures did not establish. These data indicate that acquired immunity to P. tenuis was established by 6 mo postinfection in both white-tailed and red deer. Latent periods in white-tailed deer and latent infections in red deer reinforce the need for a reliable diagnostic assay.

Detection of anti-parelaphostrongylus tenuis antibodies in experimentally infected and free-ranging moose (Alces alces)

Confirming Parelaphostrongylus tenuis infection in moose (Alces alces) and other susceptible hosts is difficult. An enzyme-linked immunosorbent assay (ELISA) was developed using the excretory-secretory (ES) products of third-stage P. tenuis larvae (ES-ELISA) and the test applied to serum samples obtained from seven moose calves (5-9.5 mo old) given infective larvae (L3) in doses approximating those likely to be received in nature (3-30 L3). Anti-P. tenuis immunoglobulin G antibodies were detected in all seven inoculated moose during the course of infection until the termination of experiment 61-243 days post-inoculation (DPI). Five animals tested between 16-25 DPI had significant antibody levels, while a sixth animal did not test positive until 46 DPI. The seventh animal was not tested until 199 DPI. Antibody levels remained elevated in all five animals that harbored adult worms at the termination of the experiment. Whereas, antibody levels showed a gradual decline in the two remaining animals, presumably because of death of worms, and antibodies were undetected in one animal at the time of necropsy. The other animal displayed an anamnestic increase in antibody level following a challenge inoculation of infective larvae. Terminal and peak optical density (OD) values detected by ES-ELISA strongly correlated with inoculation dose (r = 0.98, P = 0.02 and r = 0.95, P = 0.04, respectively) among animals harboring adult worms (n = 4) but not significantly with the number of worms recovered postmortem (peak OD, r = 0.82, P = 0.18; terminal OD, r = 0.93, P = 0.07). Unlike the ES products, use of somatic antigens of the adult worm in ELISA did not provide satisfactory results. Antibodies to P. tenuis were detectable by ES-ELISA in two of 21 free-ranging moose from an enzootic area but not from any of 23 animals from a non-enzootic area. The ES-ELISA appears to be a useful test for assessing exposure of moose to P. tenuis.

Immunodiagnosis of experimental Parelaphostrongylus tenuis infection in elk

Elk infected with the meningeal worm, Parelaphostrongylus tenuis (Protostrongylidae), do not consistently excrete larvae in feces, making the current method of diagnosing live animals using the Baermann fecal technique unreliable. Serological diagnosis could prove more useful in diagnosing field-infected animals but depends on the identification and availability of good quality antigen. To mimic field infections, 2 elk were inoculated with 6 infective L3 larvae of P. tenuis, and another 2 with 20 L3 larvae. Fecal samples were examined for nematode larvae using the Baermann technique and serum samples taken were tested for anti-P. tenuis antibody with ELISAs by using the excretory-secretory (ES) products of L3, and sonicated adult worms as antigens. One animal passed first-stage larvae in its feces 202 days postinoculation, but passed none thereafter. The remaining 3 inoculated animals did not pass larvae. In contrast to parasite detection, antibodies against larval ES products were detected in all animals starting from 14 to 28 days postinoculation and persisted until the termination of the experiment on day 243 in 2 animals that harbored adult worms. Antibodies against somatic antigens of the adult worm were not detected until day 56 but also persisted until the end of the experiment in the animals with adult worms. In 2 elk that had no adult worms at necropsy, anti-ES antibodies were detected transiently in both, while anti-adult worm antibodies were present transiently in one. These findings confirm the superiority of P. tenuis larval ES products over somatic adult worm antigens as serodiagnostic antigens, as previously observed in studies of infected white-tailed deer, and extend the application of the newly developed ELISA test in diagnosing and monitoring cervids experimentally infected with P. tenuis.

Serological diagnosis of Parelaphostrongylus tenuis infection in white-tailed deer and identification of a potentially unique parasite antigen

Serological diagnosis of Parelaphostrongylus tenuis infection should offer many advantages over the currently used method of fecal analysis that relies on a patent infection. Toward this end, we investigated the presence of P. tenuis-specific antibodies in experimentally infected white-tailed deer (WTD) and of unique P. tenuis antigens that may be exploited for serodiagnosis. WTD infected with 6, 20 or 100-150 P. tenuis third-stage larvae (L3) had anti-parasite antibodies from as early as 21 days postinoculation (dpi) until the end of the experiment (147 dpi). Peak anti-P. tenuis enzyme-linked immunosorbent assay (ELISA) titers in individual animals ranged from 1:70 to 1:5,700. Serum from infected WTD reacted with 5 distinct P. tenuis L3 antigens (105, 45, 37, 32, and 19 kDa) as detected by the immunoblotting technique. Serum from caribou infected with Parelaphostrongylus andersoni or Elaphostrongylus rangiferi reacted with all antigens except the 37-kDa antigen of L3, indicating that it may be unique to P. tenuis and can serve as a serodiagnostic antigen. The 37-kDa antigen appears to be present in the adult P. tenuis but not adult E. rangiferi or E. cervi. The development of an ELISA utilizing the unique antigen of P. tenuis should lead to a reliable diagnostic assay for P. tenuis infection in WTD.

Meningeal worm evokes a heterogeneous immune response in elk

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.

Bronchoalveolar cellular responses of goats following infections with Muellerius capillaris (Protostrongylidae, Nematoda)

The development of Muellerius capillaris in the lung of goats was associated with marked tissue damage and pronounced a cellular reaction. Using broncho-alveolar lavage, the time course of the cellular responses was studied following primary and secondary infection. During the primary infection, there was a biphasic increase in total broncho-alveolar leucocytes (an average of 294.0 +/- 137.0 cells microl[-1]) and in the absolute number of macrophages (182.0 +/- 82.0 cells ul[-1]), lymphocytes (68.5 +/- 35.0 cells microl[-1]), eosinophils (35.3 +/- 16.4 cells microl[-1]) and neutrophils (10.9 +/- 8.7 cell microl[-1]). The lung tissue reaction against worms consisted of a mild infiltration of inflammatory cells. The secondary infection resulted in significant changes in the pulmonary tissue characterised by severe inflammation, leading to widespread granulomatous formation throughout the parenchyma, hyperplasia of cells Type II and a leucocytosis in the broncho-alveolar fluids, with an anamnestic-like response by all cell types. The overall average of the total leucocytes, macrophages, lymphocytes, eosinophils and neutrophils was 529.3 +/- 347.4; 265.4 +/- 148.1; 127.3 +/- 100; 125.4 +/- 100.1 and 14.0 +/- 8.7 cells microl(-1), respectively. Secondary infection also resulted in 56% reduction of worms established in the lungs and 72.3% of L1 larval production. These data suggest that the broncho-alveolar leucocyte response to infection has an immunological basis and that the alveolar macrophages, neutrophils, eosinophils, and lymphocytes may play a significant role in lung resistance against protostrongylid nematodes.

Antigens of adults and third-stage larvae of the meningeal worm, Parelaphostrongylus tenuis (Nematoda, Metastrongyloidea)

We studied the antigens of adults and third-stage larvae of the meningeal worm, Parelaphostrongylus tenuis, in an attempt to identify potential serodiagnostic molecules for this important infection of wild ungulates. Soluble extracts of P. tenuis adult worms and third-stage larvae were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and two-dimensional (2D) electrophoresis and analyzed by immunoblotting using purified rabbit anti-P. tenuis immunoglobulin G (IgG). The IgG antibodies were obtained from animals immunized with P. tenuis adult worm or third-stage larva soluble extract and serum from elk infected with P. tenuis. Out of more than 75 antigens (as shown by 2D electrophoresis and immunoblotting), 7 antigens from adults (four 170-120-kD molecules with isoelectric points between 6.0 and 6.6, two 55-kD molecules with isoelectric points of 5.6 and 5.8, and one 13-kD molecule) and 2 antigens from third-stage larvae (one 25-30-kD molecule with an isoelectric point of 6.3 and one 13-kD molecule) distinguished P. tenuis from two other nematodes, Dictyocaulus viviparus and Trichinella spiralis. Initial results using serum from experimentally infected elk indicate that this serum recognized a similar profile of P. tenuis antigens when compared with the serum from immunized rabbits. This research has set the foundation for the development of a test for P. tenuis infections in wild and recently domesticated elk and and other ungulates.

[Histopathologic study of the host-parasite relationship: the earthworm-, wild boar-metastrongyle model]

A histopathological study was conducted on two hosts of metastrongyles (Metastrongylus sp.): earthworms and wild boars (Sus scrofa Linnaeus, 1758). In the earthworm intermediate host there were rare granulomas outside the normal site occupied by larvae (blood sinuses of calciferous glands). Given the small number of these reactions, they could not constitute a limiting factor for parasitism in this host. However, the lungs of wild boars contained numerous lesions associated with the presence of these nematodes. Such lesions, often inflammatory, were part of an immunological defence mechanism which controls the extent of parasitism in wild boar.

Differences in responses of rat- and guinea-pig-eosinophils to eosinophil chemotactic factors derived from Angiostrongylus cantonensis

Eosinophil chemotactic activity associated with whole worm extracts of the young adult worms (YA) and 1st stage larvae (L1) of Angiostrongylus cantonensis was assessed using guinea-pig- and rat-eosinophils. Both whole worm extracts were potently chemotactic to guinea-pig-eosinophils whereas only the whole worm extract of L1 was chemotactic to rat-eosinophils. Gel filtration chromatography of YA-whole worm extract yielded an eosinophil chemotactic factor (ECF-YA) with an estimated molecular weight of 16,900. ECF-YA was resistant to heating and pronase digestion but sensitive to periodate oxidation, suggesting that chemotactic activity was possibly associated with the sugar portion of the glycoprotein molecule. Guinea-pig- and rat-eosinophils were deactivated by previous incubation with homologous whole worm extracts but not with heterologous ones. When guinea-pig-eosinophils were treated with trypsin or pronase, their chemotaxis to ECF-YA was significantly inhibited, and pronase treatment was more effective. Both deactivated and trypsin-treated guinea-pig-eosinophils completely recovered their chemotaxis responses after in vitro culture for 12 and 24 h, respectively. When those eosinophils were cultured in vitro in the presence of puromycin or cycloheximide, however, their chemotaxis responses could not be recovered. These data clearly indicate that guinea-pig-eosinophils probably possess a kind of receptor (or 'recognition unit') capable of reacting to ECF-YA, and also that the receptor may be protein or glycoprotein molecules, and reproducible.

Immunoglobulin G-dependent classical complement pathway activation in neutrophil-mediated cytotoxicity to infective larvae of Angiostrongylus cantonensis

The participation of antibody and complement in cell-mediated adherence and cytotoxicity to infected larvae (L3) of Angiostrongylus cantonensis was investigated in vitro. Of the different cell types involved in the reaction, neutrophils were seen to have a predominant role in immune serum--dependent adherence and cytotoxicity to L3. In the presence of immune serum, cytotoxicity to L3 by neutrophils from infected rats was twice that of neutrophils from normal rats. Although mononuclear cells and eosinophils from infected rats significantly increased the adherence to L3, they had little lethal effect on L3. A further study using gel filtration (Sephacryl S-200) and affinity chromatography (protein A) revealed that immunoglobulin G (IgG) alone was responsible for the complement activation in neutrophil-mediated killing of L3. Neither adherence nor cytotoxicity to L3 by neutrophils were affected when immune serum was heated to 50 degrees C or treated with zymosan, but they were markedly decreased when immune serum was treated with Mg2(+)-ethylene glycol-bis-(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid. The results of this study indicate that the neutrophil-mediated adherence and cytotoxicity to L3 of A. cantonensis are mediated through IgG-dependent classical complement pathway activation.

Acquired immunity in rats against Angiostrongylus cantonensis infection

Acquired immunity against Angiostrongylus cantonensis was induced by immunizing rats with somatic antigens from fifth-stage larvae and adult worms and live third-stage larvae. Rats immunized twice had significantly fewer worms than rats immunized three times. Fewer worms were recovered from rats immunized with 200 live third-stage larvae than from any other groups. Rats immunized with somatic antigens had higher enzyme-linked immunosorbent assay (ELISA) antibody levels than rats immunized with live larvae. Rats immunized with live third-stage larvae of Angiostrongylus cantonensis were more strongly protected against challenge infections (62-92%) than rats immunized with antigens extracted from fifth-stage larvae (0-30%) and adult worms (11-24%).

Influence of immune treatments against Dirofilaria immitis infection in dogs

Mongrel dogs were inoculated with two kinds of antigenic substances. The first was a phosphate buffered saline extract of whole Dirofilaria immitis mixed with aluminum hydroxide gel (group 1), and the second was an orally administered live Metastrongylus apri infective larvae (L3) (group 2). Both groups were then infected with D. immitis L3. Indirect hemagglutination (IHA) tests showed that the antibody was produced by these inoculations before the infection was introduced, even in dogs inoculated with M. apri. This suggests a cross-reactivity between D. immitis and M. apri. The initial passive cutaneous anaphylaxis (PCA) antibody production was markedly delayed by about 70 days in group 2 compared with the production in the infected control dogs (group 3). The appearance of microfilaremia was also delayed by about one month in group 2 compared with that in the above control group. All dogs were sacrificed after the termination of the observation and worms recovered from the right ventricle and pulmonary arteries were counted and measured. The results indicated that immunization resulting from the homologous worm-somatic antigen might accelerate the growth of the infected larvae, whereas immunization resulting from the heterologous worm antigen, but cross-reactive to D. immitis, might disadvantageously affect the growth.

Humoral immune response of Balb/c mice to larval and adult worm antigens of Angiostrongylus malaysiensis

The development of Angiostrongylus malaysiensis in Balb/c mice and the humoral response due to it were studied by using the enzyme-linked immunosorbent assay (ELISA) with adult worm and L3 antigens. The worms recovered from mice were seen in the brain tissue only, they failed to migrate to the lung as in the normal host (rats). The antibody titres of sera from infected mice, showed similar patterns in response to L3 antigen and to adult worm antigen. However, the highest antibody response could be detected by L3 antigen in the early period after infection while the adult worm antigen detected a higher response in the later stages of development.

Preparation of monoclonal antibody against Angiostrongylus cantonensis antigen

Monoclonal antibodies (MAb) against A cantonensis were produced through fusion of immunised spleen cells from BALB/c mice with NS-1 myeloma cells at a ratio of 10:1. The successful fusion rate on the 3rd day of fusion was 90.1%. Ten MAb were characterised, six of which were IgG1 and the remaining four were IgG2a, IgG2b, IgM and IgA respectively. Among 6 IgG1 MAb, four were A. cantonensis-specific, of which three reacted to adult worm antigen only and one reacted to both adult worm and juvenile worm antigens. Two other IgG1 MAb showed cross-reaction with other helminthic antigens of Toxocara canis. Ascaris suum. Paragonimus westermani, Dirofilaria immitis, Anisakis Spp, Gnatostoma Spinigerum and Clonorchis sinensis.

Total and specific IgE in serum and cerebrospinal fluid of rats and guinea pigs infected with Angiostrongylus cantonensis

The total and specific IgE response to Angiostrongylus cantonensis infection was evaluated according to host permissiveness. Total IgE levels measured by a double antibody radioimmunoassay (RIA) increased slowly in the permissive host (the rat), reaching a maximum between 4 and 8 weeks after infection. This maximum was earlier but significantly lower in the non-permissive host (the guinea pig). IgE antibodies specific for adult worms or L1 or L3 larvae of A. cantonensis were measured by a radioallergosorbent test (RAST). In the case of adult worms and L1 antigens, specific IgE antibody levels showed large variations in relation to the duration of infection in rats. In contrast to total IgE levels, the specific IgE response to L3 larvae was lower in rats than in guinea pigs in both the serum and cerebrospinal fluid (CSF). These results suggest variations in the total vs specific IgE response according to host permissiveness or non-permissiveness to A. cantonensis infection. These results are discussed in the context of the possible participation of IgE antibodies in immune defence.

Local antibody production and immune complex formation in rats experimentally infected with Angiostrongylus cantonensis

The systemic humoral immune responses and tissue localization of worm-antigen, antibodies (IgG), and complement (C3) were examined in rats experimentally infected with Angiostrongylus cantonensis. While the worms remained in the subarachnoid space, it was infiltrated with plasma cells and lymphoid cells containing IgM and IgG. When the infiltration of these cells became more pronounced, the serum antibody titer began to increase. At the same time, deposits of IgM, IgG, and C3 were found in the glomeruli of the kidney. A number of eggs were observed in the lungs, enclosed in granulomatous tissues. Infiltrates of plasma cells including IgM and IgG, and deposits of IgM, IgG, and C3 were detected around the eggs and in the granulomatous tissues. A marked increase in serum antibody was observed. A. cantonensis larvae induce local antibody (IgM and IgG) production in the central nervous system prior to an increase of serum antibody titer. Measurement of cerebrospinal fluid antibody titer at an early stage of infection may confirm infection. The larvae showed no evidence of damage in spite of marked local antibody production in the central nervous system. The eggs in the lungs stimulated both local and systemic antibody production, and immune complexes were formed in the lung and the circulatory system. Immune complexes may participate in the formation of granuloma.

Immunoblot analysis of the circulating antigens occurring in serum of rats infected with Angiostrongylus cantonensis

Following the infection of rats with Angiostrongylus cantonensis, the occurrence and molecular features of circulating antigens (CAs) were analyzed, with special reference to their origin in worms, by SDS-PAGE combined with an immunoblotting technique. Antisera against the CAs were obtained by immunizing rats with sera from rats 35, 91, and 150 days postinfection. The anti-sera, referred to as anti-CA(35), anti-CA(91), and anti-CA(150), respectively, formed one or two precipitin lines when tested in Ouchterlony plates against extracts of digestive organs (DE) and of reproductive organs (RE) from adult female worms. When the anti-CA(35) was used as a blotting antibody under nonreducing conditions, a set of clearly spaced narrow bands with molecular weights (mol. wt.) in the range of 90,000-180,000 daltons developed only in the case of the DE. Besides the antigen(s), additional bands with mol.wt. of 115,000 and 185,000 daltons were revealed in the case of the RE when two other antisera were used. Immunoblot analysis of the immunoprecipitates, derived from anti-CA(150) and sera of infected rats, revealed the occurrence of two types of protein as the major CAs: one had a mol.wt. in the range of 140,000-180,000 daltons and was found in the serum 14 days postinfection, and the other, with a mol.wt. of 185,000 daltons, was found in the serum 35-150 days postinfection. Immunohistochemical studies localized the CAs predominantly in the cytoplasm of both uterine eggs and maturing oocytes.

Angiostrongylus cantonensis: immunoblot analysis of the antigens recognized by rats

Following infection of rats with Angiostrongylus cantonensis, occurrence of anti-parasite antibody in the serum was determined with special reference to the antigens recognized by host IgG antibodies, using SDS-PAGE combined with an immunoblotting technique. Three saline extracts of digestive organ, reproductive organ and body wall, isolated from adult female A. cantonensis, were used as crude antigenic solutions. Then 7 to 49 days after infection, IgG antibodies directed predominantly against a single antigen, referred to as Ac-1 antigen, were detected. After 91 days or more, infected rats formed antibodies not only against the Ac-1 antigen, but also against a wide variety of other components with molecular weights in the range of 26,000-220,000 dalton. By using an antiserum against Ac-1 antigen as a probe, it was shown that the molecular weight and subunit structure, as well as the immunoelectrophoretic mobility, varied according to the organ from which the antigenic extract was prepared. The Ac-1 protein in the extract of the reproductive organ, one of the major sources of the Ac-1 antigen, showed the same electrophoretic mobility as alpha-globulin. It has a molecular weight in the range of 100,000-200,000 dalton under both non-reducing and reducing conditions. Immunohistochemical studies, using the same antiserum and sectioned adult female worms, found Ac-1 antigen in the cytoplasm of oocytes at different stages of development, and in the lateral cord.

Isolation of specific antigens from Angiostrongylus cantonensis. 2. By affinity chromatography

The crude adult worm extract of Angiostrongylus cantonensis was subjected to a series of affinity chromatography for selective removal of host antigens as well as cross-reactive components with other helminths. The purified fraction designated as AC(p) with molecular weights ranging from 10,000-42,000 was found to contain antigenic components specific to A. cantonensis as determined by immunoelectrophoresis and enzyme-linked immunosorbent assay.

Effect of UV-irradiation, spleen cells and MLN cells on protective immunity against Angiostrongylus cantonensis infection in mice

The UV-irradiated larvae of Angiostrongylus cantonensis were used for inducing immunity in mice. A single oral dose of 100 infective UV-irradiated larvae exposed for 5 min or 15 min induced 91% and 97% protection against subsequent infection. Adoptive protection against A. cantonensis could also be transferred by spleen and mesenteric lymph node cells obtained from vaccinated mice.

Surface antigens of Angiostrongylus cantonensis developing in permissive and non-permissive hosts

The immunofluorescent antibody test and immunocytochemical method were employed to study the surface antigens of Angiostrongylus cantonensis obtained from infected rats, mice and guinea pigs. Positive results with intense fluorescence and brownish peroxidase staining were observed on the cuticular surface of A. cantonensis recovered from rats 22 days (late cerebral phase) and 34 days (lung phase) post-infection when tested with antisera against host (normal rat serum) antigens as well as crude extracts of A. cantonensis. However, host antigens were not observed on the surface of the nematode recovered from the brain of mice and guinea pigs 15 days post-infection.

Induction of protective immunity against infection by Angiostrongylus cantonensis in rats

Attempts were made to induce acquired immunity against Angiostrongylus cantonensis infection by immunizing rats with somatic (L3S) and metabolic (L3ES) antigens from third-stage larvae and with somatic antigen from adult female worms (FACE) via either a combined intraperitoneal and oral (IP-OR-OR) or subcutaneous (SC-SC-SC) route. The most effective mean in inducing protection was the administration of L3S by the IP-OR-OR route, as judged from reduced mortality, prolonged survival periods and/or reduced worm burdens. Such a protocol reduced mortality to below 20% of the unimmunized controls. The worm burden of the L3S-immunized rats was only about 25% of the control value and the survival period was at least double. However, judging from gross morphology, the absence of stunted growth and unimpaired ficundity of the worms that developed into adult stage, it appears that those worms that survived had normal development. The latter observation is in contrast to that noted with FACE immunization which seemed to affect also the growth and development of worms that survived into adult stage.

ELISA testing in cases of clinical angiostrongyliasis in Thailand

The sera from 116 Thais admitted to Nakhon Ratchasima hospital in northeastern Thailand with eosinophilic meningitis were tested for antibodies to Angiostrongylus cantonensis by ELISA. Ninety-six percent of the sera were considered positive with ELISA values exceptionally high for most patients. The clinical aspects of the disease are also presented. The ELISA test is considered to be of value in the diagnosis of the disease but tests for the antigen would provide a more definitive diagnosis.

Effect of anthelmintic treatment on the development of resistance in sheep vaccinated or experimentally infected with Dictyocaulus filaria

This investigation was undertaken to study the immune response of Iraqi sheep vaccinated with Dictyocaulus filaria larvae (Filiraq) and to determine the effect of tetramisole on the development of resistance to reinfection. The findings confirm the effectiveness of Filiraq in conferring protection against experimental infection with D filaria. However, the administration of anthelmintic four weeks after each vaccination interfered with the development of immunity. Termination of D filaria infection at 28 days by tetramisole treatment also prevented the immune response.

Studies on the interaction between an irradiated bovine lungworm vaccine and a morantel sustained release bolus

The interaction of the morantel sustained release bolus with the development of immunity in calves vaccinated with two doses of gamma irradiated (40 Kr) Dictyocaulus viviparus larvae was investigated under laboratory conditions. A total of 37 helminth-naive calves were used. Eight calves were used in the first part of the study to test the efficacy of a larval vaccine prepared by using gamma rays delivered from a cobalt source. In the second part of the study, four groups of four groups of four calves each were vaccinated and of these, all the animals in two groups each received a bolus. The remaining three groups (two groups of four and one group of five calves each) remained nonvaccinated with each animal in one group receiving a bolus. All the calves were challenged with approximately 2000 lungworm larvae four months postvaccination. In order to simulate possible field conditions, two of the vaccinated groups and two of the nonvaccinated groups were given a trickle infection of 800 lungworm larvae over a four-week period, three months prior to challenge. Based on a comparison of clinical signs, pathology and lungworm burdens at necropsy, the vaccination of the calves conferred a significant degree of protection (P less than 0.001) to a subsequent challenge compared with controls. The introduction of a morantel sustained release bolus and/or a trickle infection had no effect on the high degree of protection engendered by the vaccination. Nonvaccinated calves given a trickle infection, with or without a bolus, were also highly immune to challenge.

Analysis of antigens from different developmental stages of Angiostrongylus cantonensis

Protein profiles of somatic extracts from different developmental stages and excretory and secretory products of third-state larvae of Angiostrongylus cantonensis were analyzed and characterized by polyacrylamide gel electrophoresis in sodium dodecyl sulfate under both reduced and unreduced conditions. Immunological identification of common and stage-specific antigens was determined by radioimmunoprecipitation using chronically infected rat serum and antisera from rats immunized with somatic extracts of third-stage larvae and adult female worms. The somatic extracts of first-and third-stage larvae and of adult worms were found to be highly complex, each consisting of more than 20 different peptides with molecular weights varying from higher than 130,000 to 8,200 daltons. Most proteins were composed of single polypeptide chains. Polypeptides with molecular weights of 80,000, 39,500 and 22,000 daltons were present in more than one developmental stages and were antigenically related. Those with molecular weight of 15,500 dalton, was present primarily in L3S and its possible usefulness in immunodiagnosis of infection that occurs in man was discussed.

Importance of competitive binding in the detection of antigen specific bovine isotypes and subisotypes by the micro ELISA

An enzyme-linked immunosorbent assay was developed to detect and quantify the specific bovine immunoglobulin class response to Trypanosoma theileri, Dictyocaulus viviparus and infectious bovine rhinotracheitis virus. Comparative measurement of the specific immunoglobulin classes in whole serum was achieved using monospecific rabbit antibovine IgG1, IgG2 and IgM, followed by a goat anti-rabbit Ig-enzyme conjugate (antiglobulin ELISA). The results obtained in the antiglobulin ELISA compared favourably with the standard (or indirect) ELISA using the purified immunoglobulins. Competitive inhibition between specific immunoglobulins of different isotypes and subisotypes was the major disadvantage of the antiglobulin ELISA. This latter assay failed to detect specific IgG2 against T theileri antigen in both calf and adult whole serum. The inability to detect the specific IgG2 was a result of competitive inhibition by specific IgG1. However, competitive inhibition between specific immunoglobulins was not observed in either of the other test systems using D viviparus and infectious bovine rhinotracheitis virus antigens.

Comparison of protection against lungworm infection between levamisole-treated and vaccinated calves

A trial involving 122 calves of approximately 100 kg bodyweight was undertaken to assess the protection against reinfection with Dictyocaulus viviparus in calves whose primary infection was treated with levamisole. Four matched groups, each of 20 housed calves, were taken and one group vaccinated against parasitic bronchitis. Calves in the remaining groups were infected with third stage D viviparus larvae daily for 42 days and treated with 7 . 5 mg/kg levamisole administered subcutaneously at 14, 14 and 28, or 14, 28 and 42 days. All groups were challenged with 10,000 larvae per call on day 49. Relevant control groups were maintained. Eight calves from each main group were slaughtered four weeks later and survivors retained until 20 weeks from the start of the experiment. Calves treated sequentially with two or three doses of levamisole at 14 day intervals while exposed to incoming infection approximated more closely to the performance of vaccinated cattle and were significantly better protected against challenge than those receiving one dose of levamisole only. Feed conversion was most efficient in vaccinated calves not exposed to the potentially lethal trickle infection. After the last levamisole treatment, vaccinated calves and those treated with three doses of levamisole at 14 day intervals were significantly heavier than calves receiving one dose of levamisole only. Vaccinated calves grew heavier than those receiving triple levamisole treatments until the time of challenge. Thereafter the triple levamisole treatment group improved and eventually grew heavier than the vaccinated animals.

ELISA for the detection of angiostrongylus cantonensis antibodies in patients with eosinophilic meningitis

The enzyme-linked immunosorbent assay (ELISA) was used to examine sera from twelve Taiwanese children with eosinophilic meningitis suspected to be induced by infection with Angiostrongylus cantonensis. Polystyrene tubes were coated with Angiostrongylus cantonensis antigens (5 micrograms/ml protein) prepared from fourth-stage larvae recovered from the brains of experimentally infected rats. Alkaline phosphatase labelled goat antihuman IgG conjugate was used in a dilution of 1 to 500; sera were diluted 1 to 1000. Positive control sera were from patients with parasitologically confirmed infections; the negative control sera from healthy persons. The ELISA values for sera from suspected cases of angiostrongyliasis ranged from 4.5 to 23.1; the positive control sera, 12.7 to 34.4 and the negative control sera 1.3 and 2.2. The assay shows promise and with the use of more purified antigens, micromethods and automated ELISA readers it should become valuable in the presumptive diagnosis of angiostrongyliasis in endemic areas.

Antibody responses in rats infected with Angiostrongylus cantonensis and the passive transfer of protective immunity with immune serum

Little haemagglutinating antibody was detected in the serum of rats with primary Angiostrongylus cantonensis infections until the juvenile worms left the brain and lodged in the lungs about 35 days after infection. Antibody titres reached a peak 50 days after infection and were maintained for at least a further 95 days. Increasing the infective dose of A. cantonensis larvae increased the peak antibody titres attained by the infected rats. Re-infection temporarily reduced the serum antibody titre, but later it increased and showed an anamnestic response. Reaginic antibody production was transient during primary infections; re-infection failed to stimulate further reaginic antibody production. Antiserum from immune donor rats protected recipients against A. cantonensis. The transferred immune serum suppressed anti-A. cantonensis antibody production in recipient rats.

Passive immunity in rats infected with Angiostrongylus cantonensis: interactions between syngeneic immune serum and sensitized lymph node cells

Immune serum injected into the peritoneum of rats passively protected them against Angiostrongylus cantonensis; this protection was greater than that conferred by passively transferred immune lymph node cells. When immune lymph node cells and serum were transferred together into the same rat, no enhanced protection was observed. The protective effect of serum was inhibited by the lymph node cells to levels commensurate with those conferred by immune lymph node cells alone. Normal lymph node cells also depressed the levels of immunity conferred by immune serum when they were transferred together with serum, but to a lesser extent than did sensitized lymph node cells. Transferred antibody acted to suppress antibody production against A. cantonensis in recipient rats.

Immunization with irradiated larvae against Dictyocaulus filaria in young lambs

In the lungworm-endemic areas of Kashmir, 6-10 week old lambs of Karnah and Kashmir Merino breeds were vaccinated with two doses of 50 kR gamma-irradiated larvae of Dictyocaulus filaria, given a month apart. Assessed on the basis of reduced prevalence and significantly lower faecal larval output over an eight-month observation period, vaccinated lambs showed a high degree of resistance to naturally acquired D. filaria infection. The results also show that vaccination against D. filaria provided some degree of protection against infection with other lungworm species.

[The value of lungworm vaccination in calves (author's transl)]

Although the lungworm vaccine was found to be useful under field conditions, some questions remain, particularly epidemiological ones. Experiments with housed and grazing calves were carried out to elucidate a number of these problems. From these experiments in which vaccinated and unvaccinated calves were challenged, it was apparent: 1. that the immunity developed by vaccinated calves could resist a heavy challenge without clinical symptoms; 2. that vaccinated calves exposed to a heavy challenge could produce small numbers of lungworm larvae. It was shown that, despite the hard winter of 1978/1979, infectious lungworm larvae were present on the pasture in the spring of 1979.

Use of excretory and secretory products from adult female worms to immunize rats and mice against Angiostrongylus cantonensis infection

To evaluate their protective potential, excretions and secretions of adult female Angiostrongylus cantonensis were prepared from an in vitro culture fluid and injected together with Freund's complete and incomplete adjuvants into rats and mice. Under appropriate conditions, judging from reduced mortality rates and/or prolonged survival periods, these animals were protected against a lethal challenge infection with 3rd-stage larvae. Although both 'immunized' and unimmunized mice died following such a lethal infection, the survival period for the 'immunized' group was significantly longer than that of unimmunized controls (40.8 compared with 26.7 days). On the other hand, the mortality rate of 'immunized' rats was reduced to 25% as compared with 100% in unimmunized controls. There was also evidence of adverse effects on parasite development in these 'immunized' rats. The number of young adult worms recovered from the brain 21 days after challenge infection and both the number and size of mature male and female worms in the lungs 60 days after infection were significantly reduced in the 'immunized' rats. Moreover, the reproductive activity of female worms was depressed, as evident from the output of 1st-stage larvae in the faeces and the number of eggs released during maintenance in vitro. The quantity of proteins released during in vitro maintenance of adult worms in a chemically defined serum-free medium was 0.2--0.5 micrograms/worm/day. The concentrated culture fluid contained at least 7 different antigenic components when analysed with hyperimmune rabbit antiserum to female excretions and secretions (FES) antigen. Polyacrylamide gel electrophoresis in sodium dodecylsulphate showed the presence of 3 major and at least 12 minor protein components with molecular weights varying from 24,000 to 115,000 daltons. Different lines of evidence presented in this study show immunological cross-reactivity among antigens from different developmental stages.

Eosinophilic meningitis: a suspected case of angiostrongylosis found in Shizuoka Prefecture, Honshu, Japan

A patient with eosinophilic meningitis in Shizuoka Prefecture, Honshu, Japan had nausea, vomiting and headache on admission; laboratory examinations revealed leukocytosis with eosinophilia. Eight days later neck stiffness appeared. Lumbar puncture showed an increase of the initial pressure in association with eosinophilic pleocytosis in the spinal fluid. The possibility of angiostrongylosis was considered because the patient had eaten raw slugs for 4 years as a remedy for lumbago. Although the serum contained cross-reactive antibodies against Toxocara canis, positive reactions to Angiostrongylus cantonensis antigens were observed in all of the immunological tests made. These observations, together with results of epidemiological studies in Honshu carried out by other investigators, suggest that the present case of eosinophilic meningitis may have been caused by A. cantonensis. One previous case has been reported from Honshu Island, Japan.

Effect of immunization with metabolic antigens on experimental infection of rats with Angiostrongylus cantonensis

Immunization of rats with excretions and secretions from an in vitro culture fluid (ES antigens) of adult female Angiostrongylus cantonensis markedly enhanced their resistance to infection by third-stage larvae. Mortality rate, survival period, worm development and worm recovery, determined after a lethal challenge with infective larvae, were compared in immunized and unimmunized animals. With regard to these criteria, the results obtained with animals that had been immunized with ES antigens from adult males were found to be indistinguishable from those of the unimmunized controls. On the contrary, those immunized with ES antigens from adult females had lower mortality rate, increased survival period, and lower worm burden. Both male and female worms recovered from brain and mature adults recovered from pulmonary arteries of rats that had been immunized with female ES antigens were also found to be stunted.

A precipitin test for the diagnosis of human abdominal angiostrongyliasis

A precipitin reaction was observed when sera of cotton rats infected either naturally or experimentally with Angiostrongylus costaricensis were tested by gel double-diffusion against sera obtained from three biopsy-confirmed human cases of A. costaricensis. With immunoelectrophoresis, the antigen was demonstrated in the serum of infected rats. The antibody in the human serum was mostly of the IgG type. No cross reactions were seen with sera from individuals infected with the common intestinal helminths, or individuals serologically positive for Toxocara, A. cantonensis, Chagas' disease, amebiasis, leishmaniasis, toxoplasmosis, or syphilis.