The isolation of a 22 kDa band after SDS-PAGE of Schistosoma mansoni adult worms and its use to demonstrate that IgE responses against the antigen(s) it contains are associated with human resistance to reinfection.

In schistosomiasis endemic areas, intensities of reinfection after treatment are greater amongst young children than amongst adults, and high levels of parasite-specific IgE are associated with resistance to reinfection in an age-dependent manner. Previously we have reported that, in Western blots, a 22 kDa band was recognized by human IgE and that the incidence and intensity of S. mansoni reinfection were significantly lower amongst individuals who had IgE against this band, compared with those who did not (Dunne et al. 1992). Here we report the isolation of a 22 kDa SDS-PAGE band, its incorporation into ELISA and the demonstration that levels of human anti-22 kDa IgE had a significant negative correlation with intensities of subsequent reinfection. Rabbit anti-22 kDa band serum recognized the outer tegument, gut tegument, and the collecting ducts and flame cells of adult worms. The 22 kDa band antigen(s) was also present in "lung'- and "post-lung' schistosomula stages of S. mansoni, and in S. haematobium, S. bovis and S. japonicum adult worms. Metabolic labelling of schistosomula and worms demonstrated the in vitro synthesis and release of 22 kDa antigens.

A cloned major Schistosoma mansoni egg antigen with homologies to small heat shock proteins elicits Th1 responsiveness.

In schistosomiasis mansoni, soluble egg antigens of the worm induce chronic T-cell-mediated granulomatous tissue responses. Since the first preparation of crude soluble egg antigen extract, a dearth of highly purified antigens has hampered the identification of granuloma inducer molecules. Here we report that a cloned 38-kDa egg polypeptide (r38) with homologies to small heat shock proteins is a strong immunogen. The recombinant and the sodium dodecyl sulfate-polyacrylamide gel electrophoresis separated and eluted native 38-kDa (p38) polypeptides, used in microgram amounts and unaided by adjuvant, sensitized mice for a Th1-type immune response, with strong interleukin-2 (IL-2) and gamma interferon secretion but no IL-4 and IL-10 secretion. Extensive cross-reactivity between these two polypeptides was evident. THis pattern was confirmed by reverse transcription-PCR that showed strong IL-2 and gamma interferon message expression but trace amounts of IL-4 message expression in r38-sensitized splenocytes. In mice, the polypeptide induced pulmonary mononuclear granuloma formation around antigen-coupled beads or worm eggs. We propose that the superior immunogenicity of r38 is linked to its relatedness to small heat shock proteins and that the 38-kDa polypeptide may induce the Th1 cytokine responses observed during the early development phase of the egg-induced granuloma.

T-lymphocyte responsiveness in murine schistosomiasis mansoni is dependent upon the adhesion molecules intercellular adhesion molecule-1, lymphocyte function-associated antigen-1, and very late antigen-4.

Granuloma formation in murine schistosomiasis is dependent on CD4+ Th lymphocytes and requires recruitment and accumulation of inflammatory cells at the site of egg deposition. The present study examined the role of three adhesion molecules, intercellular adhesion molecule-1 (ICAM-1), lymphocyte function-associated antigen-1 (LFA-1), and very late antigen-4 (VLA-4), that participate in cellular recruitment, interaction, and lymphocyte activation during in vitro activation of acutely and chronically infected spleen and liver granuloma lymphocytes. Blockade of ICAM-1, LFA-1, or VLA-4 by rat monoclonal antibody inhibited spleen and granuloma lymphocyte interleukin-2 (IL-2) and IL-4 production as well as lymphoproliferative responses at similar levels (66 to 87%). The down-modulated cytokine and proliferative responses of chronically infected lymphocytes were inhibited to the same extent as their acutely infected counterparts. Cell sorting analysis demonstrated that acutely and chronically infected splenic and granuloma lymphocytes expressed similar levels of LFA-1, ICAM-1, and VLA-4 and that more ICAM-1 was expressed on infected than on uninfected mouse lymphocytes. By exposure of cells to paired monoclonal antibodies at suboptimal doses, it was determined that whereas all three adhesion molecules may participate, only ICAM-1 and LFA-1 showed synergistic interactions in determining lymphocyte responsiveness. These data suggest that spleen and liver granuloma lymphocytes are equally well armed with functional adhesion receptors. Thus, ICAM-1, LFA-1, and VLA-4 play an important accessory role in inflammatory cytokine production and lymphocyte proliferation, and therefore these adhesion molecules may participate in the initiation and maintenance of the granulomatous inflammation.

Human IgG subclass responses and subclass restriction to Schistosoma mansoni egg antigens.

In areas endemic for schistosomiasis, there is great heterogeneity in antibody isotype responses to parasite antigens amongst infected individuals. At the population level, the isotype composition of antibody responses undergoes dynamic changes which are associated with the age of infected individuals. Here we examine the IgG subclass responses to Schistosoma mansoni eggs (soluble egg antigens; SEA) of infected individuals by immunoblot and ELISA. By controlled treatment of SEA-coated ELISA plates and immunoblot nitrocellular strips with sodium periodate, in order to oxidize terminal carbohydrate residues selectively, we were able to relate individuals subjects' isotype responses to the different antigens that they responded to, and to the presence of putative carbohydrate and peptide epitopes on those antigens. IgG2 responses were restricted strictly to sodium periodate-sensitive carbohydrate epitopes and antigens of relatively high molecular weight. These antigens were not usually recognized by other isotypes and, therefore, they were only recognized by individuals who had high levels of IgG2. IgG1 and IgG3 responses were directed against both carbohydrate and peptide epitopes, whereas IgG4 responses were restricted to periodate-resistant epitopes. This suggests that the fall in IgG2 responses, and reciprocal rise in IgG4 antibodies, seen in young children as their intensities of schistosome infection increase, is not the result of isotype switching, and that, if these two subclasses are involved in blocking immunity to schistosomiasis, they are operating independently.

Immunity after treatment of human schistosomiasis: association between IgE antibodies to adult worm antigens and resistance to reinfection.

Previous studies in school children have demonstrated the slow development with age of resistance to reinfection after chemotherapy of Schistosoma mansoni infections, and have indicated that inappropriate ("blocking") antibody responses prevent the expression of immunity in young children. The present study was designed to investigate further the nature of the protective responses, by serological studies on a group of 151 S. mansoni-infected individuals resident in an endemic area in Machakos District, Kenya. Antibody levels against various antigens in blood samples before treatment were related to intensity of previous infections; antibodies in blood samples taken 6 months after treatment were related to cumulative reinfection rates over the following 30 months. IgE against an adult-worm antigen preparation correlated positively with age and negatively with reinfection. In contrast, IgE antibodies against other life-cycle stages showed either no relationship or the reverse correlation. Furthermore, antibodies of other isotypes against adult-worm antigens showed no correlations with reinfection. The correlation with IgE could be demonstrated for different preparations of adult worms, including a periodate-treated preparation presumptively depleted of carbohydrate epitopes. For both the intact and the periodate-treated preparations, multiple regression analysis of the results for children less than or equal to 16 years old demonstrated an IgE effect after allowing for age, although this effect was not observed in a previously studied group of school children. Western blot analysis of the adult-worm preparation revealed a limited set of antigens recognized by IgE, among which an antigen of 22 kDa was prominent. The qualitative presence of IgE against this antigen could also be shown to be related to a lack of subsequent reinfection.

Temporal variation in the carbohydrate and peptide surface epitopes in antibody-dependent, eosinophil-mediated killing of Schistosoma mansoni schistosomula.

Changes in the surface antigenicity and susceptibility to eosinophil-dependent killing during in vitro development of schistosomula of Schistosoma mansoni, were examined using sera from rabbits and mice immunized with antigens that are shed from the schistosomulum in vitro (shed antigen), a carbohydrate extract of shed antigen (SAg/CHO) or a periodate-insensitive fraction of shed antigen (SAg/PEP). Anti-SAg/CHO antisera recognised mainly carbohydrate epitopes on the parasite surface, whilst anti-SAg/PEP antisera bound to periodate-insensitive, putative peptide, surface epitopes. Anti-SAg/PEP antibodies failed to recognise the surface of newly transformed schistosomula unless the parasite was first treated with sodium periodate, suggesting that these epitopes may be masked by periodate sensitive (i.e., carbohydrate) epitopes. There was an increase in anti-SAg/PEP antibody binding to the larval surface with age of the parasite in vitro; five-day-old lung schistosomula were also recognised by anti-SAg/PEP antisera. In contrast, anti-SAg/CHO antibody binding declined with parasite age, and failed totally to recognise lung schistosomula. This change in epitope expression was reflected in eosinophil-dependent cytotoxicity assays, with anti-SAg/CHO antisera killing young larvae and anti-SAg/PEP antisera only killing older larvae. Lung worms were not killed by either antisera. The difference in epitopes recognised by the antisera was also reflected in the antigens identified by immunoprecipitation and SDS-PAGE.

Further studies on head lice and their control in Tasmania.

This study on the control of head lice infestation in Tasmania confirms the efficacy of malathion preparations compared with lindane preparations.

Venereal trichomoniasis: role of men.

It has been suggested that high zinc concentrations found in men may prevent Trichomonas vaginalis from being established in the male reproductive tract. In this investigation T vaginalis was readily killed at concentrations of zinc that occur in the prostatic fluid of healthy men (minimum trichomonacidal concentration (MTC) of 6.4 mmol/l). T vaginalis was also shown to be killed by human prostatic extracts as well as by human seminal fluid, even when the zinc content was much lower than the MTC for T vaginalis. It seems likely, therefore, that there are at least two antitrichomonal mechanisms in the male reproductive tract, one being zinc dependent and the other not relating to zinc content. Tritrichomonas foetus, which causes venereal trichomoniasis in cattle, was unaffected by bovine seminal fluid and was killed by zinc only at concentrations far higher than those found in the prostatic fluid in the bull (MTC 200 mmol/l).