Passive immunization with a monoclonal IgM antibody specific for Strongyloides ratti HSP60 protects mice against challenge infection.

It is estimated that 30-100 million people are infected with the pathogenic nematode Strongyloides stercoralis worldwide but parasite control is still based on anti-helminthic treatment. To develop protective vaccination strategies, we use the murine model of Strongyloides ratti infection. We have shown recently that vaccination with alum-precipitated, but not with native or CFA-emulsified S. ratti heat shock protein 60 (srHSP60) conferred protection to challenge infection. Here we describe the generation of a monoclonal IgM specific for srHSP60. Anti-srHSP60 detected human and srHSP60 and stained S. ratti infective larvae in vitro. Passive immunization of mice with monoclonal anti-srHSP60 IgM led to reduced numbers of migrating larvae in lung and head, reduced numbers of parasitic adults in the small intestine and reduced larval output upon S. ratti challenge infection. Taken together, our findings highlight the relevance of srHSP60 as vaccine candidate for the induction of antibody-mediated protection against Strongyloides infection.

Screening Swiss water bodies for potentially pathogenic free-living amoebae.

Free-ling amoebae (FLA) including Acanthamoeba spp., Naegleria fowleri, Balamuthia mandrillaris and Sappinia pedata, can cause opportunistic infections leading to severe brain pathologies. Human infections with pathogenic FLA have been increasingly documented in many countries. In Switzerland, thus far, the occurrence and distribution of potentially pathogenic FLA has not been investigated. Swiss water biotopes, including swimming pools, lakes, rivers and ponds, have now been screened for the presence of FLA, and assessment of their pathogenicity potential for a mammalian host has been undertaken. Thus, a total of 17 isolates were recovered by in vitro cultivation from these different aquatic sources. Characterization by sequence analysis of Acanthamoeba spp.-specific and 'FLA-specific PCR products amplified from 18s rDNA based on morphological traits, thermotolerance, and cytotoxicity towards murine fibroblasts yielded the following findings: Echinamoeba cf. exundans (3 isolates), Hartmannella spp. (3), Vannella spp. (4), Protacanthamoebica cf. bohemica (1), Acanthamoeba cf. castellanii (1) and Naegleria spp. (5). B. mandrillaris and N. fowleri did not range amongst these isolates. None of the isolates exhibited pronounced cytotoxicity and all failed to grow at 42 degrees C; therefore, they do not present any potential for CNS pathogenicity for humans.

Isolation and molecular characterization of recombinant Echinococcus granulosus P29 protein (recP29) and its assessment for the post-surgical serological follow-up of human cystic echinococcosis in young patients.

We synthesized recombinant Echinococcus granulosus protoscolex recP29 antigen to be preliminarily assessed by ELISA and immunoblotting. RecP29-serology was carried out on 54 young patients with cystic echinococcosis (CE). Patients were classified into either cured (CCE) (n=40) or non-cured (NCCE) (n=14) CE patients. RecP29 ELISA showed a gradual decrease of antibody concentrations in all CCE cases that were initially (before treatment) seropositive to this antigen (25 out of 40) or that seroconverted following treatment. A complete seronegativity was reached within 3 years post-surgery in all of these cases. Conventional HCF ELISA yielded seronegativity in only 10% of initially recP29-seropositive CCE patients (P=0.086). Likewise, recP29 immunoblotting yielded seronegativity in 93% of 29 out of 40 initially recP29-immunoblot-positive CCE patients after 3 years follow-up, compared with 72% in the HCF immunoblotting (P=0.060). Eleven out of 14 NCCE patients were initially positive by recP29 ELISA, and 10 out of these maintained a marked anti-recP29 antibody reactivity until the endpoint of the follow-up period. All 14 NCCE cases were initially seropositive by recP29 immunoblotting, and 13 cases remained seropositive until the end of the study. Thus, recombinant P29 protein appears prognostically useful for monitoring those post-surgical CE cases with an initial seropositivity to this marker.

Assessment of Echinococcus granulosus somatic protoscolex antigens for serological follow-up of young patients surgically treated for cystic echinococcosis.

Echinococcus granulosus protoscolex soluble somatic antigens (PSSAs) were assessed for their prognostic value in the serological follow-up of young patients treated for cystic echinococcosis (CE), compared to conventional hydatid fluid (HF) antigen. Based on different clinical courses and outcome of infection, as well as imaging findings, patients were retrospectively classified into two different groups including either cured CE (CCE; i.e., absence of active cysts or presence of inactive cysts, respectively) and noncured CE (NCCE) patients still presenting active cysts at the end of an up to 5-year follow-up period. An immunoglobulin G (IgG)-PSSA enzyme-linked immunosorbent assay (ELISA) showed a gradual decrease in antibody levels in CCE cases, reaching seronegativity in 20% of the cases at least within 5 years postsurgery. In comparison, the conventional IgG-HF ELISA showed a significantly lower progressive decrease in antibody levels, serology becoming negative in only 15% of CCE patients at the endpoint of the follow-up period. Serological analysis of PSSA by immunoblotting yielded an interesting immunoreactive double band of 27 and 28 kDa that, in 15 (75%) of 20 CCE cases, exhibited a rapid decrease and subsequent disappearance of respective antibody reactivities within 3 years postsurgery. Conversely, anti-27- and -28-kDa antibody reactivity strongly persisted until the endpoint of the follow-up period in all of the five NCCE patients. Further analysis of the 27- and 28-kDa doublet by using affinity-purified antibodies showed that the double band was not detectable in HF. Furthermore, a predominantly IgG4 subclass-restricted humoral immune response against the 27- and 28-kDa antigens was demonstrated in seroreactive CE patients. Overall, an anti-27- and -28-kDa response appeared to correlate with cyst activity. In conclusion, PSSA represents a useful candidate to carry out a serologic follow-up of CE subsequent to treatment and deserves further respective evaluation for other age groups of CE patients.