Human antibody responses to Schistosoma mansoni: does antigen directed, isotype restriction result in the production of blocking antibodies?

Immunoglobulin M antibodies are not specific for serodiagnosis of human toxocariasis

Serodiagnosis of human toxocariasis is established by detecting serum anti-Toxocara IgG antibodies, but there is little knowledge regarding the reactivity of human IgM antibodies against the Toxocara antigens. In this study, we have evaluated the reactivity of IgM antibodies in sera from patients with toxocariasis, patients with other helminth infections, and healthy individuals, against Toxocara larval excretory-secretory (TES) antigens by enzyme-linked immunosorbent assay (ELISA) and Western blot (WB). Anti-Toxocara IgM were detected in 91.4% of sera from patients with toxocariasis, 76% of sera from patients with other helminth infections, and 45.3% of sera from healthy individuals when ELISA was used. Likewise, IgM antibodies were detected in 94.8% of sera from patients with toxocariasis, 65.3% of sera from patients with other helminth infections, and 41% of sera from healthy individuals when WB was used. This reactivity exhibited only a slight decrease when the TES antigens were deglycosylated, showing that not only glycosidic epitopes, but also peptide epitopes are involved in the recognition and binding of IgM antibodies during the immune response against the parasite. The results shown that IgM antibodies are not specific for serodiagnosis of human toxocariasis.

Post-splenectomy infections in chronic schistosomiasis as a consequence of bacterial translocation

INTRODUCTION

Bacterial translocation is the invasion of indigenous intestinal bacteria through the gut mucosa to normally sterile tissues and internal organs. Schistosomiasis may cause alterations in the immune system and damage to the intestines, portal system and mesenteric lymph nodes. This study investigated bacterial translocation and alterations in the intestinal microbiota and mucosa in schistosomiasis and splenectomized mice.

METHODS

Forty female 35-day-old Swiss Webster mice were divided into the following four groups with 10 animals each: schistosomotic (ESF), splenectomized schistosomotic (ESEF), splenectomized (EF) and control (CF). Infection was achieved by introduction of 50 Schistosoma mansoni (SLM) cercariae through the skin. At 125 days after birth, half of the parasitized and unparasitized mice were subjected to splenectomy. Body weights were recorded for one week after splenectomy; then, the mice were euthanized to study bacterial translocation, microbiota composition and intestinal morphometry.

RESULTS

We observed significant reductions in the weight increases in the EF, ESF and ESEF groups. There were increases of at least 1,000 CFU of intestinal microbiota bacteria in these groups compared with the CF. The EF, ESF and ESEF mice showed decreases in the heights and areas of villi and the total villus areas (perimeter). We observed frequent co-infections with various bacterial genera.

CONCLUSIONS

The ESEF mice showed a higher degree of sepsis. This finding may be associated with a reduction in the immune response associated with the absence of the spleen and a reduction in nutritional absorption strengthened by both of these factors (Schistosoma infection and splenectomy).

Schistosomiasis in areas of low endemicity: a new era in diagnosis

Parasitological detection of Schistosoma is the cornerstone of schistosomiasis diagnosis in areas of transmission worldwide. However, a steep decrease of sensitivity in low-endemicity areas (LEAs) compromises estimation of schistosomiasis. Despite the restricted utilization of molecular and immunodiagnostic techniques, recent improvements and advances have been contributing to change this scenario, especially in LEAs. Nonetheless, the main issue in a new era of diagnosis overcomes technical advances per se and relates to the loss of 'gold standards' in schistosomiasis diagnosis in LEAs. Here, we review and discuss the current role of molecular and immunodiagnostic methods in schistosomiasis management.

Human schistosome infection and allergic sensitisation

Several field studies have reported an inverse relationship between the prevalence of helminth infections and that of allergic sensitisation/atopy. Recent studies show that immune responses induced by helminth parasites are, to an extent, comparable to allergic sensitisation. However, helminth products induce regulatory responses capable of inhibiting not only antiparasite immune responses, but also allergic sensitisation. The relative effects of this immunomodulation on the development of protective schistosome-specific responses in humans has yet to be demonstrated at population level, and the clinical significance of immunomodulation of allergic disease is still controversial. Nonetheless, similarities in immune responses against helminths and allergens pose interesting mechanistic and evolutionary questions. This paper examines the epidemiology, biology and immunology of allergic sensitisation/atopy, and schistosome infection in human populations.

Immune profiles in hepatosplenic schistosomiasis mansoni after surgical treatments

The hepatosplenic form of schistosomiasis mansoni sometimes induces bleeding in oesophageal varices that requires surgical treatment. Although splenectomy is often necessary these patients rarely present with septic events, a finding that may be related to changes in the immunological system. To investigate the immunological profiles of patients with schistosomiasis, we studied the B- and T-lymphocyte counts and the immunoglobulin A, G and M (IgA, IgG and IgM) levels in patients treated surgically and in those who were not operated on. Patients who underwent distal splenorenal shunt, preserving the spleen, showed significantly increased T-lymphocyte counts compared with healthy controls. The IgM and IgG levels were significantly increased compared with the healthy controls in patients submitted to partial and total splenectomy, respectively. The IgM level also tended to increase in patients who were not operated on compared with the controls. These results suggest that chronic schistosomiasis may influence the immune system.