Short report: long-term serum antibody isotype responses to Strongyloides stercoralis filariform antigens in eight patients treated with ivermectin

The enzyme-linked immunosorbant assay was used to investigate long term changes in serum immunoglobulin G1 (IgG1), IgG4, IgE, and IgA against Strongyloides stercoralis phosphate-buffered saline-soluble filariform larval antigens in eight Jamaican patients treated with ivermectin. Patients were followed for periods of between 170 and 542 days. Based on repeated formalin-ether concentration and agar plate culture, all patients were found to be uninfected up to 18 months following chemotherapy. Generally, all antibody isotype levels decreased following treatment, although there was considerable heterogeneity among patients. In a single patient with hyperinfection, the decrease in IgG4 was marginal and may represent a treatment failure. Reduction in serum antibody isotype responses to S. stercoralis following treatment may be used to assess the effectiveness of ivermectin in treating endemic strongyloides (AU)

Treatment of patients infected with Strongyloides stercoralis using ivermectin: assessment of efficacy and safety - abstract

Infections with Strongyloides stercoralis are often refractory to thiabendazole therapy in certain patients. Ivermectin is being used increasingly for treatment of uncomplicated infections; however, possible immunopathological changes associated with drug-induced release of antigens as observed with use of the drug in filariasis has not been studied in strongyloidiasis. In this study we used the enzyme linked immunosorbant assay (ELISA) technique to examine the profiles of S. stercoralis-specific IgG4, IgE and IgA against saline soluble filariform extracts in 8 patients treated for the parasite. All patients were found to be negative for the parasite by stool examination following treatment. Isotype levels fell in concert following treatment although there was considerable heterogeneity among patients. Levels remained low following treatment response but were still measurable for up to eighteen months post-treatment. There appeared to be no rapid release of parasite antigens following treatment. One patient exhibited a transient increase in levels of IgA after which there was a decline in this and all other isotypes. The single patient with proven chronic infection and a history of gastrointestinal symptoms exhibited almost ablated IgG1, IgE and IgA responses prior to treatment but had a significant IgG4 response which remained high following treatment. The reduction in antibody levels post-treatment may be used as confirmation of parasitological cure. The study showed that there was no rapid release of S. stercoralis antigens as seen in filarial infections and that Ivermectin is safe and effective against the parasite (AU)

Serum isotype responses in patients infected with Strongyloides stercoralis following treatment with ivermectin - abstract

Infections with Strongyloides stercoralis occur worldwide and can cause significant morbidity and mortality in man. They are often refractory to conventional chemotherapy especially in immunocompromised individuals. Recent studies have shown that Ivermectin is a safe and effective drug for use in uncomplicated infections. In this study, the profiles of parasite-specific IgG1, IgG4, IgE and IgA against a PBS soluble S. stercoralis filariform extract following treatment with ivermectin were investigated using the enzyme-linked immunosorbant assay (ELISA) technique. A series of 8 patients with parasitologically proven strongyloidiasis were treated with ivermectin and followed up for periods of 5 to 18 months. The predominant isotype found in the sera of patients from this series was IgG. High levels of IgG1 were recorded in young individuals while IgG4 was predominant in older persons. Levels of all isotypes declined following treatment and remained low up to eighteen months. Furthermore, no parasitological evidence of S. stercoralis infection was found after treatment, using agar plate and formalin-ether concentration methods. The reduction in antibody levels of post-treatment may be used as an indicator of adequate treatment and also demonstrate that patients are not exposed to drug-induced antigens following treatment. The study of S. stercoralis specific isotype profile will be useful in immuno-epidemiological studies in communities (AU)

Prospective evaluation of enzyme-linked immunosorbent assay and immunoblot methods for the diagnosis of endemic Strongyloides stercoralis infection

Recently described enzyme-linked immunosorbent assay (ELISA) and immunoblot methods for the detection of serum IgG against Strongyloides stercoralis larval antigens were prospectively evaluated for the diagnosis of endemic strongyloidiasis. A modification of the ELISA involved preincubation of sera with Onchocerca gutturosa phosphate-buffered saline-soluble extract to remove cross-reactivity with other helminths. The sensitivity of the ELISA increased from 80 percent and 85 percent following preincubation. Similarly, there was an increase in specifity from 94 percent to 97 percent. The IgG recognition of 41-, 31-, and 28-kD filariform larval components showed sensitivities of 100 percent, 85 percent and 65 percent, respectively. Both the ELISA following incubation of sera with O. gutturosa extract and serum IgG reactivity to a 41-kD larval component using immunoblotting are sensitive and specific techniques for diagnosing endemic strongyloidiasis.(AU)

Prospective evaluation of an ELISA and Western Blot for the diagnosis of endemic strongyloides stercoralis infection - abstract

Strongyloides stercoralis is the most serious intestinal nematode infecting humans in the Caribbean. The parasite is, however, difficult to diagnose using standard laboratory techniques, especially in sub-clinical cases. An ELISA, using PBS extracts of filariform larvae as antigen, and a Western Blot method were evaluated in the Jamaican community. Sensitivity and specificity of the ELISA were 73 per cent and 93 per cent (n=135) respectively. Pre-incubation of sera with Onchocerca gutterosa (Filariata) antigen increased sensitivity and specificity of the ELISA to 82 per cent and 97 per cent, respectively. Similarly, The Western Blot which was based on IgG recognition of proteins of 41kD and one of 31kD or 28kD detected 82 per cent of infected individuals and 97 per cent of true negatives. There was no notable cross-reactivity by either ELISA or Western Blot with Ascaris, Trichuris or hookworm, also common to the Region. ELISA proved to be a sensitive and specific test for diagnosing S. stercoralis infection in Jamaica. Western Blotting had no significant merits over those of ELISA although it confirmed the presence of 3 immunodominant bands which may play a role in future immunodiagnosis. Furthermore, it adds to the battery of sensitive serological tests available to clinicians who have to decide on the infection status of potential S. stercoralis patients who are about to receive immuno-suppressive therapy (AU)

Immunodiagnosis of Strongyloides stercoralis infection: a method for increasing the specificity of the indirect ELISA

Indirect enzyme-linked immunosorbent (ELISA) allows sensitive detection of serum immunoglobulin (Ig) G against a soluble extract of Strongyloides stercoralis infective larvae. In this study, 40/40 (100 percent) human strongyloidiasis sera had high levels of anti-S. stercoralis IgG, but 30/40 (75 percent) filariasis sera, and 12/40 (30 percent) necartoriasis sera also had higher levels than control sera from UK residents. In attempts to increase the assay specificity by absorption of cross-reactive IgG, the effectiveness of pre-incubation of sera with extracts of different parasitic nematodes was investigated. One hour of incubation with 20 æ/ml aqueous extract of Onchocerca gutturosa absorbed cross-reactive IgG in most filariasis and necatoriasis sera, reducing the proportion with IgG levels above the positivity threshold by more one-half. Preliminary results suggest that absorption with extracts of other filarial nematodes is equally effective, and that some cross-reactive IgG is directed against phosphorylcholine. Cross-reactive IgG in most necatoriasis sera was effectively absorbed with an extract of Ascaris lumbricoides. Absorption of cross-reactive IgG is an effective means of increasing the specificity of the indirect ELISA, for use in the immunodiagnosis and immuno-epidemiology of S. stercoralis infection.