Immunologic evaluation of extracted intestinal proteins from Angiostrongylus cantonensis adult worms.

BACKGROUND: To determine whether intestinal Angiostrongylus cantonensis antigens can induce protective immunity in rats, gut antigens prepared from female adults (FAGP) and somatic antigens prepared from both male (MA) and female (FA) adult worms were used to immunize rats. METHODS: Rats were immunized twice with MA, FA, or FAGP antigens and then challenged with 50 third-stage A. cantonensis larvae, and different readouts were used to monitor protective immunity. Additionally, protein profiles of MA, FA, and FAGP extracts were analyzed and characterized by immunodetection methods. RESULTS: A 15% reduction in fifth-stage larvae from brains and a 14% reduction in adult worms from pulmonary arteries were observed in rats immunized with FAGP compared to controls. However, there was a >50% reduction in rats immunized with MA or FA. The lengths of larvae and adults recovered from FAGP-immunized rats were shorter than those recovered from other groups. The number of first-stage larvae recovered from fecal material in FAGP-immunized rats was significantly reduced. Additionally, FAGP induced the highest splenocyte proliferation. Serum IgG titers were not directly correlated with protective immunity. An 84 kDa gut membrane protein was strongly recognized by anti-FAGP antibodies. CONCLUSION: We demonstrated that immune responses induced by FAGP reduced the growth, development, and reproduction of A. cantonensis in subsequent infections. While the possibility of using FAGP combining with MA or FA antigens as a multi-function vaccine in immune protection against A. cantonensis needs to be further elucidated, we hope that it provides a novel strategy for this parasite vaccine development.

An enzymatically inactivated hemoglobinase from Necator americanus induces neutralizing antibodies against multiple hookworm species and protects dogs against heterologous hookworm infection.

Hookworms digest hemoglobin from erythrocytes via a proteolytic cascade that begins with the aspartic protease, APR-1. Ac-APR-1 from the dog hookworm, Ancylostoma caninum, protects dogs against hookworm infection via antibodies that neutralize enzymatic activity and interrupt blood-feeding. Toward developing a human hookworm vaccine, we expressed both wild-type (Na-APR-1(wt)) and mutant (Na-APR-1(mut)-mutagenesis of the catalytic aspartic acids) forms of Na-APR-1 from the human hookworm, Necator americanus. Refolded Na-APR-1(wt) was catalytically active, and Na-APR-1(mut) was catalytically inactive but still bound substrates. Vaccination of canines with Na-APR-1(mut) and heterologous challenge with A. caninum resulted in significantly reduced parasite egg burdens (P=0.034) and weight loss (P=0.022). Vaccinated dogs also had less gut pathology, fewer adult worms, and reduced blood loss compared to controls but these did not reach statistical significance. Vaccination with Na-APR-1(mut) induced antibodies that bound the native enzyme in the parasite gut and neutralized enzymatic activity of Na-APR-1(wt) and APR-1 orthologues from three other hookworm species that infect humans. IgG1 against Na-APR-1(mut) was the most prominently detected antibody in sera from people resident in high-transmission areas for N. americanus, indicating that natural boosting may occur in exposed humans. Na-APR-1(mut) is now a lead antigen for the development of an antihematophagy vaccine for human hookworm disease.

Inhibition of HIV-1 infection by monoclonal antibodies to carbohydrates of Schistosoma mansoni.

Patients infected with HIV-1 develop a potent humoral immune response against the virus, but HIV-1 primary isolates are remarkably resistant to neutralizing antibodies. Considering that the envelope glycoprotein of HIV-1 (gp120/41) is heavily glycosylated, we investigated whether anti-carbohydrate antibodies could inhibit HIV-1 infection in vitro. We studied the neutralizing activity of three monoclonal antibodies (mAbs) raised to carbohydrates of Schistosoma mansoni, against seven primary isolates of HIV-1. Assays were performed infecting peripheral blood mononuclear cells from normal donors with viral isolates previously treated with mAbs. Viral strains used were tropic for the coreceptors CCR5, CXCR4, and dual-tropic ones. We found that the anti-glycan mAbs vigorously inhibited HIV-1 infection, regardless of the preferential coreceptor usage of the isolate, in a dose-response manner. Importantly, five isolates were resistant to neutralization by two HIV-1 antibody-positive human sera endowed with potent anti-HIV-1 inhibitory activity. Our findings suggest that carbohydrates of the HIV-1 viral envelope may be a target of an effective humoral immune response elicited by vaccination.

Passive protection against fasciolosis in mice by immunization with a monoclonal antibody (ES-78 MoAb).

Recently, we reported a partial characterization of the epitope recognized by the ES-78 monoclonal antibody (MoAb). This monoclonal antibody was obtained from spleen lymphocytes of a mouse immunized with excretory-secretory antigens of Fasciola hepatica adult worms. In the present study, we report the results obtained in experiments of passive protection using this MoAb in BALB/c mice infected with 15 Fasciola hepatica metacercariae. The monoclonal antibody was able to reduce the parasite burden when administered 24 h before challenge but not when delivered 7 days after challenge. The antibody recognition of digestive tract structures in 3-week-old parasites was demonstrated by immune histochemical techniques. The antigens purified by affinity chromatography using this antibody had molecular weights of 14-20, 25-29 and 36-45 kDa and demonstrated proteinase activity similar to cathepsin L. These results suggest that the antigens carrying the epitope recognized by the ES-78 MoAb may be used as target in the protection against fasciolosis.

Identification and molecular cloning of a 67-kilodalton protein in Schistosoma japonicum homologous to a family of actin-binding proteins.

A monoclonal antibody to Schistosoma japonicum which conferred significant protection against cercarial challenge in mice was produced. The predicted translation product of the cDNA corresponding to the antigen recognized by this antibody was homologous to a newly identified family of actin-binding proteins. The expressed protein bound polymerized actin and was recognized by serum from patients infected with S. japonicum.

Synergistic action of cyclosporin A and polyspecific rabbit anti-sera against murine Schistosoma mansoni.

The efficacy of cyclosporin A (CsA) treatment against Schistosoma mansoni in mice was compared with treatments that included co-administration of one of two anti-sera (infected rabbit serum (IRS) obtained by repeated infection and a worm membrane antigen anti-serum (WSS) obtained by immunization with worm surface supernatants). These two sera recognized a number of worm antigens but differed in precise detail. Administration of CsA alone to mice harbouring mature infections of S. mansoni reduced worm burdens and preferentially targeted female worms. Sera administered alone had no effect on worm burdens. Co-administration of worm membrane antigen anti-serum (WSS) with CsA reduced worm burden significantly compared with drug treatment alone. Male worms were more susceptible to this combined treatment regime. Anti-infection serum (IRS) had a lesser stimulatory activity in combination with CsA which was not statistically different from the effects of CsA alone on worm burdens. The data suggest that CsA-induced surface damage to the parasite may reveal specific antigens that were previously unavailable for host attack.

Protective effects of anti-antiidiotypic IgE antibodies obtained from an IgE monoclonal antibody specific for a 26-kilodalton Schistosoma mansoni antigen.

A rat IgE mAb specific for larval Ag (26 kDa, 56 kDa) has been shown to protect rats against Schistosoma mansoni infection. Immunizations of Lou/M rats performed with this IgE (Ab1) induced the production of antiidiotypic antibodies (Ab2). Moreover, after this Ab2 production, anti-antiidiotypic antibodies (Ab3) were revealed. The screening of Ab3 isotypes showed the presence of IgG Ab3 and more interestingly of IgE Ab3, i.e., the same isotype as Ab1. These IgE and IgG antibodies recognized predominantly the 26-kDa Ag and were cytotoxic for schistosomula in the presence of platelets for IgE Ab3 and eosinophils for IgG Ab3. Both IgE and IgG Ab3 conferred by passive transfer protective immunity to infected rats (up to 50%). Thus the immunization with an IgE mAb led in part to the production of Ab3 of the same isotype as Ab1. In conclusion, these results suggest that the isotype selection of the antibodies of the third generation (Ab3) might be influenced by the Ab1. The respective role of the idiotope and isotype of Ab1 in isotype regulation is discussed.

Role of a mouse monoclonal IgE antibody in passive transfer of immunity to Schistosoma japonicum infection

We have been able to produce a mouse monoclonal IgE antibody specific to an adult worm antigen extracted from Schistosoma japonicum (Sj). The antibody was able to elicit passive cutaneous anaphylaxis in the rat skin against Sj with the highest titer of 1:256,000 but did not cross-react with S. mansoni antigen. The antibody recognized a 97-kDa molecule expressed on the surface of mechanically transformed schistosoma of S. japonicum. Passive transfer of the antibody into mice in the early stage of challenge infection resulted in a partial but significant reduction of recovery of adult worms. Induction of eosinophilia by an oral administration of embryonated eggs of Toxocara canis prior to challenge infection enhanced the reduction.