Age-related prevalence of antibodies to infective-larvae of Wuchereria bancrofit in normal individuals from a filaria-endemic region.

Antibody isotypic levels (IgM, IgE and IgG subclasses) to infective larvae (L3) of Wuchereria bancrofti were measured in 104 normal individuals from a filaria-endemic region in Orissa. The titres of antibodies were considerably higher in adults (n = 25, 25·1 ± 3·8 year) than in children (n = 52, 7·1 ± 2·1 year). Young children (n = 14) less than four years were seronegative to all isotypes other than IgM, the sero-conversion to which was achieved in the children (n=15) by the age of 7·5±1·2 years. The prevalence of other isotypes increased with age and reached a maximum in early adulthood (18·6 ± 1·6 years), which persisted in older adults (> 30 years). However, the increase in IgG3 prevalence with age was less marked. IgG2 was detected only after 10 years of age. Compared to the high prevalence (100%) of IgM, IgE, IgG1, and IgG2, in adults. IgG3 and IgG4 prevalences were low, 35% and 28% respectively. IgA level to L3 antigen was found to be extremely low even in adults. These data indicate that the prevalence of L3 antibodies was different for different isotypes and the acquisition of antibody response essentially followed an age dependent pattern.

Antigenicity of filarial superoxide dismutase in human bancroftian filariasis.

Superoxide dismutase activity was measured in different stages of growth of filarial parasites (human and cattle). The activity was almost undetected or very low in microfilarial stage but in adult worms, the enzyme activity was high. The enzyme was characterized to be a Cu/Zn superoxide dismutase. Most of the enzyme activity was associated with a detergent extractable fraction of adult (Setaria) parasite. The enzyme was also detected in the in vitro released products of adult worms. The superoxide dismutase activity was completely inhibited with IgG antibody from chronic filarial patients in contrast to IgG from normal people. Filarial patients particularly have high IgG and IgM antibody levels to purified enzyme. However, individuals from non-filarial regions of Orissa are sero-negative for superoxide dismutase antibodies. Antibody response to superoxide dismutase could thus be used for filarial diagnosis.

Enhanced antibody response to a detergent-soluble antigen in human filariasis after treatment with diethylcarbamazine.

An antigen fraction has been isolated from the water insoluble component of cattle filarial parasite Setaria digitata by detergent NP-40 solubilization, precipitation with ammonium sulphate and fractionation on sephadex G-100. Immunoglobulin G response to the isolated antigenic fraction was selectively suppressed in asymptomatic microfilaraemic people in comparison to the amicrofilaraemic groups of endemic normals and chronic patients. However, treating microfilaraemic people with diethylcarbamazine enhanced the antibody levels by 10-fold. These results suggest that active infection suppresses the response induced by the isolated antigenic fraction which is elevated after clearance of microfilariae.

Immune response to an allergenic fraction of Setaria digitata in human filariasis.

A low molecular weight antigenic fraction has been isolated from saline-soluble extracts of cattle filarial parasite Setaria digitata. This glycoprotein fraction (Fr III) which appears to have low phosphorylcholine content cross-reacted with infective larval (L3) antigens of Wuchereria bancrofti. Binding of human chronic filarial serum with L3 antigens could be inhibited partially by Fr III. The fraction elicited immediate cutaneous hypersensitivity reaction in people living in Wuchereria bancrofti endemic regions. The proportion of skin test positive cases was found to be highest in endemic normals in contrast to infected cases. IgE levels were however not different in chronic filariasis and in endemic normals (or in asymptomatic microfilaraemic carriers). On the other hand, specific IgG level was considerably enhanced only in chronic filariasis.

Interactions of the channel forming peptide alamethicin with artificial and natural membranes.

Alamethicin and related α-aminoisobutyric acid peptides form transmembrane channels across lipid bilayers. This article briefly reviews studies on the effect of alamethicin on lipid phase transitions in lipid bilayers and on mitochondrial oxidative phosphorylation. Fluorescence polarization studies, employing 1,6-diphenyl-1,3,5-hexatriene as a probe, suggest that alamethicin fluidizes lipid bilayers below the phase transition t-emperature, but has little effect above the gel-liquid crystal transition point. Alamethicin is shown to function as an uncoupler of oxidative phosphorylation in rat liver mitochondria. The influence of alamethicin on mitochondrial respiration is modulated by the phosphate ion concentration in the medium. Classical uncoupling activity is evident at low phosphate levels while inhibitory effects set in at higher phosphate concentrations. Time-dependent changes in respiration rates following peptide addition are rationalized in terms of alamethicin interactions with mitochondrial membrane components.