Increased IgG antibody responses to excretory/secretory antigens in neonates born from mothers infected with filarial nematodes.

The present investigation aimed to evaluate the extent to which maternal filarial infection influences IgG subclass immune responses in the cord blood of neonates. Prevalence of antigenaemia was detected using an Og4C3 assay. Filaria-specific IgG subclasses against excretory/secretory antigens were measured by ELISA. Transplacental transfer of circulating filarial antigen (CFA) was observed from 34.8% of CFA-positive mothers to their respective cord bloods. Filaria-specific IgG1, IgG2 and IgG4 responses were significantly higher among cord bloods of infected mothers compared to cord bloods of uninfected mothers. In contrast, the IgG3 response was significantly higher among cord bloods of uninfected mothers. The study shows that transplacental transfer of filarial antigens and filaria-specific IgG4 occurs more in mothers having high worm burdens, and transfer of filaria-specific IgG3 occurs more in the cord blood of uninfected mothers. The findings of the study provide evidence for the development of prenatal sensitization to filarial antigens in utero, and high filaria-specific IgG4 in cord blood may serve as a marker for in-utero sensitization.

Hydrocele fluid: can it be used for immunodiagnosis of lymphatic filariasis?

BACKGROUND & OBJECTIVES: Diagnosis of lymphatic filariasis using serum has been established but the utility of hydrocele fluid for the purpose is not exactly known. Since, hydrocele is a chronic form of the disease manifestation in a variety of situations and often poses difficulty in diagnosing its origin, we have evaluated the usefulness usage of hydrocele fluid for diagnosis of filarial origin of hydrocele in this study. METHODS: Paired samples of serum and hydrocele fluid from 51 individuals with hydrocele, living in an endemic area of Wuchereria bancrofti were assessed. Circulating filarial antigen, filarial specific antibody and cytokine assay were performed in both serum and hydrocele fluid of patients. RESULTS: Og4C3 assay detected circulating filarial antigen (CFA) in serum and corresponding hydrocele fluids. The level of IgG, IFN-γ and IL-10 were found to be high in CFA-negative, while IgM and IgE were high in CFApositive hydrocele fluid and serum samples associated with hydrocele. On the other hand neither CFA-positive nor CFA-negative hydrocele fluid and serum samples associated with hydrocele showed any difference in IgG4 level. INTERPRETATION & CONCLUSION: This study showed that the filaria related antigens and antibodies found in serum can be detected with equal sensitivity in hydrocele fluid. Therefore, it can be used as an alternative to serum for immunodiagnosis of filariasis, and help monitoring the filarisis elimination programme.

Immuno-epidemiology of bancroftian filariasis: a 14-year follow-up study in Odisha, India.

Forty asymptomatic, circulating filarial antigen negative (CFA(-ve)) and ten asymptomatic, circulating filarial antigen positive (CFA(+ve)) individuals were followed up longitudinally over a period of 14 years at intervals of 7 years in order to investigate the immunological, parasitological and clinical changes that took place in an endemic area due to natural process. The clinical status, microfilaremia, circulating filarial antigenemia and immunological responses to filarial antigens (DSSd1 and Sd30) prepared from cattle filarial parasite Setaria digitata, were examined. The observations showed that 19 individuals had developed either antigenemia or filarial symptoms (acute filarial lymphangitis/hydrocele) from CFA(-ve) group. Three individuals had cleared antigenemia and one had developed microfilaremia from CFA(+ve) group after 7 years. Increased IgG and IgM and low IgG2 and IgG4 level responses along with high lymphocyte production were observed in CFA-negative individuals. This was in contrast to observations made in CFA(+ve) subjects. The results of the present study indicated that the changes taking place in the immunological, clinical and CFA status of individuals residing in filaria endemic regions developed different clinical manifestation with course of time.

In utero sensitization modulates IgG isotype, IFN-γ and IL-10 responses of neonates in bancroftian filariasis.

In utero exposure has been considered as a risk factor for filarial infection. To evaluate the influence of maternal infection on filarial-specific IgG subclass response in neonates and their correlation with plasma levels IL-10 and interferon-γ, 145 pairs of mothers and their respective cord bloods were examined. Transplacental transfer of circulating filarial antigen (CFA) was observed in 34·8% cord bloods from CFA positive mothers. Filarial-specific IgG1, IgG2 and IgG4 responses of cord bloods were found to be positively correlated with CFA of mothers. In contrast, IgG3 responses negatively correlated with CFA of mothers. The % of similarity of recognition pattern in the cord blood with maternal blood was high for IgG3 response than IgG4 in all three groups. An increased levels of IL-10 and decreased levels of interferon gamma (IFN-γ) were observed in cord blood of infected mothers. Interferon gamma was positively correlated with IgG3 and negatively correlated with IgG4 level. On the other hand, IL-10 was positively correlated with IgG4 and CFA, indicating that cytokines may play a role in modulating the immune responses in cord bloods of sensitized foetus. The findings of the study reveal that in utero tolerance or sensitization may influence the filarial-specific immunity to infection in neonates.

Maternal filarial infection: association of anti-sheath antibody responses with plasma levels of IFN-γ and IL-10.

Maternal filarial infection influences the risk of acquiring infection and development of immunity in children. Here we have analysed the blood samples of 60 mothers (24 infected and 36 uninfected) and their corresponding cord bloods to assess the impact of maternal infection on the anti-sheath antibodies and cytokine production in neonates born from them. About 69·4% of non-infected mothers and their cord bloods showed the presence of anti-sheath antibodies, while only 16·6% of the cord bloods from infected mothers were positive for it. The IL-10 level was significantly high in cord bloods of infected mothers compared with non-infected mothers. At the same time the IL-10 level was also observed to be remarkably high in cord bloods of both infected and non-infected mothers negative for anti-sheath antibody. In contrast, IFN-γ levels were significantly high in cord bloods of non-infected mothers compared with infected mothers and the increment was prominent in cord bloods of both infected and non-infected mothers positive for anti-sheath antibody. The study reveals that the presence or absence of anti-sheath antibodies in association with cytokines skews the filarial specific immunity to either Th1 or Th2 responses in neonates. This may affect the natural history of filarial infection in early childhood.

Lymphatic filariasis in children: age dependent prevalence in an area of India endemic for Wuchereria bancrofti infection.

Lymphatic filariasis has been considered as a disease of adults and most epidemiological surveys have excluded children. The prevalence of infection and clinical manifestations of the disease among children in the age group of 1-15 years was determined in a Wuchereria bancrofti endemic area. The 1383 children from the rural villages of a coastal district (Khurda), State of Orissa, India, were studied. The finger prick blood (50ìl) samples were collected between 20:30 and 23:30 hours for parasitological and immunological evaluation. At the same time clinical examination was also recorded. Circulating Filarial Antigen (CFA) status and antibody (IgG) to filarial antigen was also determined in the study population. The prevalence of asymptomatic microfilaraemic carriers (AS), acute disease (AC), hydrocele (Hyd) cases and cryptic infection (CFA +ve) were 9.9%, 14.6%, 3.8% and 17.1% respectively. It was observed that 45.4% of the children below 15 years of age were either infected or had clinical manifestations of the disease. IgG antibody positivity 75.4%, 84% and 95.8% were observed in 1-5 yr, 6-10 yr and 11-15 years age group respectively. The study suggested that asymptomatic infection and acute form of disease were common occurrence among the children and more than half of the children population were either infected or having clinical manifestations of the diseased by pre-adult stage (11-15 years of age) in the endemic area.

Transplacental transfer of filarial antigens from Wuchereria bancrofti-infected mothers to their offspring.

OBJECTIVE: Maternal infection has been considered to be a risk factor for filarial infection in offspring. In order to examine the influence of maternal infection in neonates, we have determined the prevalence of circulating filarial antigen (CFA) and anti-filarial antibodies in 119 maternal and corresponding cord blood samples collected from an area endemic for bancroftian filariasis. METHOD: Prevalence of antigenaemia was detected using Og4C3 circulating filarial antigen enzyme-linked immunosorbent assay. The presence of microfilariae was determined by filtration of a 1 ml sample through a Nuclepore membrane. Antibody isotypes (IgG, IgM, and IgE) to filarial antigen (Setaria digitata antigenic extract) were determined by enzyme linked immunosorbent assay (ELISA). RESULTS: Microfilariae were detected in 14 cases (11.8%), whereas the Og4C3 assay could detect filarial antigen in 44.5% of pregnant mothers. Interestingly, 24.5% of samples born from CFA-positive mothers were found positive for CFA. None of the cord samples from CFA-negative mothers were found positive for CFA. No significant difference was observed in prevalence of filarial-specific IgG, IgM and IgE antibodies in CFA-positive and negative mothers. IgG antibody was detected in 60.5% of maternal and 21.8% of cord samples. IgG antibody in the cord does not differ with the antigen status of the mother. In contrast IgM and IgE antibody prevalence was significantly higher in cord from infected mothers than non-infected mothers (11.3% vs 0 for IgM, 24.5% vs 3.03% for IgE). CONCLUSION: Our study demonstrates the transplacental transfer of circulating filarial antigen from mother to cord. Filaria-specific IgM and IgE antibodies were higher in cord blood from infected mothers than from non-infected mothers. The findings of the study provide additional circumstantial evidence for pre-natal sensitization to filarial antigens developed in utero.

Protective efficacy of a filarial surface antigen in experimental filariasis.

A water-insoluble, detergent-soluble, surface-associated glycoprotein, designated as Dssd1, was found to induce microfilaria clearance in Mastomys coucha implanted with Setaria digitata. Intraperitoneal implantation of adult female worms of S. digitata in M. coucha could induce microfilaraemia lasting about 165 days in circulation. Immunization of M. coucha with Dssd1 antigen either before or after implantation of worms resulted in a significant reduction in microfilaria density. Complete clearance of circulating microfilaria was achieved by immunization (before and after implantation) in animals by 95 and 105 days post-implantation, respectively, indicating the efficacy of Dssd1 antigen in the clearance of microfilaraemia in infected M. coucha.

Antigenemia in young children living in Wuchereria bancrofti-endemic areas of Orissa, India.

The prevalence of filarial antigenemia (an indicator of adult worm burden) among 610 children, aged 3-15 years, was determined in three endemic villages of Khurda District, Orissa, India, during 2005. Prevalence of antigenemia, detected using Og4C3 circulating filarial antigen ELISA, was 32.6% compared with 10% microfilaraemia. Although the prevalence of antigenemia increased marginally with increase in age, no significant difference was observed among the children of different age groups (28.3% in 3-5 years, 31.5% in 6-10 years and 35.2% in 11-15 years), indicating that the adult worm burdens did not vary much according to the age of the study children. Gender did not influence the prevalence of antigenemia. The study emphasizes the advantage of using the circulating filarial antigen assay for detecting true filarial infection and demonstrates a high prevalence of antigenemia among the 610 children studied.

Parasite antigenaemia and IgG4 antibodies to a filarial protease in an endemic human population in India.

Levels of circulating filarial antigen (Og4C3) and IgG4 antibodies to a filarial protease were determined in subjects of Wuchereria bancrofti exposed sera from Orissa, India. In addition to all individuals with antigenaemia (microfilaraemia), IgG4 antibodies were also detected in some individuals without antigenaemia. A 2-year longitudinal follow-up indicated that IgG4 seropositivity in asymptomatic amicrofilaraemics could be a risk factor for acquiring infection (antigenaemia).

Antigenemia is associated with low antibody response to carbohydrate determinants of a filarial surface antigen.

The IgG response to a filarial surface antigen (DssdI) was evaluated in circulating antigen (Og4C3 test) positive and negative individuals from the Wuchereria bancrofti endemic region of Orissa, India. Circulating filarial antigen (CFA) positive individuals exhibited depressed antibody levels to DssdI and individuals with high antibody levels were invariably CFA negative. Low IgG levels to DssdI are associated with CFA positivity irrespective of microfilaraemia and clinical status. Thus asymptomatic microfilaraemic individuals with antigen positivity exhibited low IgG levels similar to symptomatic (chronic filariasis with elephantiasis, hydrocele) or asymptomatic amicrofilaraemic individuals with antigenemia. Western blot analysis revealed a band of approximately 210 kDa reactive with CFA-negative, but not with CFA-positive sera. DssdI was subjected to mild periodate oxidation to investigate the role of carbohydrate epitopes. The treatment considerably reduced the antigenic recognition of DssdI, stressing the immunodominance of carbohydrate residues of DssdI in infection-free individuals. In contrast, individuals with active infection failed to produce such antibodies to filarial surface carbohydrates.

Age-dependent prevalence of asymptomatic amicrofilaraemic individuals in a Wuchereria bancrofti-endemic region of India.

The age-related prevalence of asymptomatic amicrofilaraemics, apparently uninfected individuals, was determined in a Wuchereria bancrofti-endemic region of Orissa, India during 2001. The prevalence of these uninfected individuals was highest in the younger age groups (aged < or = 15 years), decreased rapidly in those aged > 15 to 40 years, and then stabilized in those aged > 40 years.

Antigenemia at 10 years after diethylcarbamazine treatment of asymptomatic microfilaraemic individuals: marginal conversion to infection-free state.

A group of asymptomatic microfilaraemic individuals (n = 44, 29 males, 15 females) living in a Wuchereria bancrofti endemic region of Orissa, India, was treated with a standard regimen of diethylcarbamazine (12 days, 6 mg/kg) in 1990. The incidence of microfilaraemia and antigenemia (Og4C3) was determined after a gap of 10 years in 2000. Nineteen individuals reacquired microfilariae (43.2%, 11 males, eight females), five males developed hydrocele, two females became acute filarial patients and 18 subjects (13 males, five females) were asymptomatic amicrofilaraemics. Filarial antigen was detected in 36 individuals (81.2%, 27 male, nine female) comprising microfilaraemics, amicrofilaraemics and diseased. Only eight individuals (18.2%, two males, six females) remained antigen free.

A long-term follow-up of asymptomatic amicrofilaraemic individuals living in a filaria-endemic region of Orissa, India: infection and disease status.

A group of asymptomatic amicrofilaraemic individuals (endemic normals) aged > 12 years was identified in 2 filaria-endemic villages of Orissa, India in 1990 (Bajapur village, n = 40) and in 1994 (Olosingh village, n = 47). They were re-examined for microfilaraemia and disease status in the year 2000 after a 10-year and a 6-year period. Studies conducted at both villages yielded a similar pattern in the development of disease. Above 85% of the females remained normal, compared to 54% of males. Remaining individuals had acquired hydrocoele (males) and adenolymphangitis (both males and females). Only 1 individual converted to having asymptomatic microfilariae. No case of elephantiasis was observed. Results indicate that most females remained normal and males faced considerable risk of developing hydrocoele in these Wuchereria bancrofti-endemic areas.

A four year follow up study of filaria specific IgE response in individuals with hydrocele.

BACKGROUND & OBJECTIVES: Hydrocele is the most common clinical manifestation in males infected with Wuchereria bancrofti. IgE response to a filarial allergen Sd30 was evaluated in hydrocele patients living in a W. bancrofti endemic region of Orissa, India. METHODS: IgE levels to Sd30, an antigenic fraction isolated from Setaria digitata, were determined by ELISA in sera from patients of filariasis (n = 93). IgG and IgM levels were also determined. RESULTS: It was observed that microfilaraemic patients with hydrocele (n = 16) exhibited considerably reduced (P < 0.01) IgE levels in comparison to hydrocele patients without microfilariae (n = 27) and to other filarial groups (elephantiasis, asymptomatic microfilaraemics). The reduced IgE response in microfilariae positive patients with hydrocele persisted even after a gap of four years in the majority of patients. INTERPRETATION & CONCLUSIONS: The results show low IgE levels in microfilaraemic patients with hydrocele in comparison to other groups in filaria endemic regions. The exact mechanism of this reduction in IgE is not known but these patients make a distinct group in filaria endemic regions and should be considered separately for immunological evaluation.