Recombinant antigens used as diagnostic tools for lymphatic filariasis.

Lymphatic filariasis (LF) is a parasitic disease caused by the worms Wuchereria bancrofti, Brugia malayi, or Brugia timori. It is a tropical and subtropical illness that affects approximately 67 million people worldwide and that still requires better diagnostic tools to prevent its spread and enhance the effectiveness of control procedures. Traditional parasitological tests and diagnostic methods based on whole protein extracts from different worms are known for problems related to sample time collection, sensitivity, and specificity. More recently, new diagnostic tools based on immunological methods using recombinant antigens have been developed. The current review describes the several recombinant antigens used as tools for lymphatic filariasis diagnosis in antigen and antibody capture assays, highlighting their advantages and limitations as well as the main commercial tests developed based on them. The literature chronology is from 1991 to 2021. First, it describes the historical background related to the identification of relevant antigens and the generation of the recombinant polypeptides used for the LF diagnosis, also detailing features specific to each antigen. The subsequent section then discusses the use of those proteins to develop antigen and antibody capture tests to detect LF. So far, studies focusing on antibody capture assays are based on 13 different antigens with at least six commercially available tests, with five proteins further used for the development of antigen capture tests. Five antigens explored in this paper belong to the SXP/RAL-2 family (BmSXP, Bm14, WbSXP-1, Wb14, WbL), and the others are BmShp-1, Bm33, BmR1, BmVAH, WbVAH, BmALT-1, BmALT-2, and Wb123. It is expected that advances in research with these antigens will allow further development of tests combining both sensitivity and specificity with low costs, assisting the Global Program to Eliminate Lymphatic Filariasis (GPELF).

Filariasis linfática por Brugia. Presentación de un caso / Lymphatic filariasis by Brugia. Case report

Introducción: según datos de la Organización Mundial de la Salud, la filariasis es -después de la lepra- la segunda causa de discapacidad permanente en el mundo con un programa mundial para su control en todas las zonas o áreas endémicas.Objetivo: presentar un caso de filariasis linfática por Brugia encontrado en la Misión Médica Cubana en áfrica, que puede ser útil como consulta para los colaboradores en cualquier región endémica.Presentación del caso: paciente de 3 años, con el antecedente de ingreso por diagnóstico de dermatitis localizada en la pierna izquierda, para la que recibió tratamiento con antibiótico tópico y antihistamínicos, mejoró y se egresó. Regresó con un cuadro clínico en fase aguda: aumento de volumen marcado de la pierna izquierda, desde el dorso del pie hasta debajo de la rodilla, duro y que no deja godet. Se ingresó con diagnóstico presuntivo de celulitis y posible filariasis, por lo que se le realizaron el examen físico y los complementarios específicos; no obstante resultar negativa la búsqueda de microfilarias, el cuadro clínico y humoral fue compatible con filariasis linfática por Brugia.Conclusiones: se considera prudente, ante cuadros sugestivos, tener en cuenta la posibilidad de una filariasis linfática para establecer el diagnóstico de forma precoz y evitar al paciente las secuelas e incapacidad resultantes(AU)

Introduction: according to the World Health Organization, filariasis is -after leprosy- the second cause of permanent disability in the world with a global program for control in all zones or endemic areas.Objective: to present a case of lymphatic filariasis by Brugia found at the Cuban Medical Mission in Africa, which can be useful as a reference for employees in any endemic region.Case report: 3 years old patient admited with a history of being diagnosed of dermatitis located in the left leg, which was treated with topical antibiotics and antihistamines; he improved and was discharged. He returned with a clinical profile in acute phase: marked increasing of volume of the left leg, from the back of the foot to below the knee, hard and not let godet. He entered with presumptive diagnosis of cellulitis and possible filariasis, so he underwent a physical examination and specific complementary; however be negative finding microfilariae, the humoral and clinical profile was consistent with lymphatic filariasis by Brugia.Conclusions: it is considered prudent, given suggestive profiles, to consider the possibility of lymphatic filariasis to establish the diagnosis early and avoid the patient against the consequences resulting in disability(AU)

An ultrastructural, cytochemical and freeze-fracture study of the surface structures of Brugia malayi microfilariae.

Ultrastructural analysis of the cuticle of Brugia malayi microfilariae indicated that it is composed of 2 regions: the inner one 15-20 nm thick with a homogeneous aspect and the outer one, designated as epicuticle, which is 15-20 nm thick. Three laminae separated by electron-lucent regions were seen in the epicuticle. Labeling of the cuticle and epicuticle of B. malayi and Wuchereria bancrofti microfilariae was observed when thin sections of Lowicryl-embedded parasites were incubated in the presence of gold-labeled phospholipase-C. Replicas of freeze-fractured microfilariae showed the presence of 2 fracture planes in the epicuticle and no fracture plane in the inner region of the cuticle. The P face of the epicuticle outer fracture plane presented few particles similar to intramembranous particles (IMPs). The epicuticle inner fracture plane P and E faces presented large numbers of densely-packed small particles and many protuberances. Also, fracture faces of hypodermal and muscle cell plasma membranes were analyzed. Faces P and E of fractured membranes showed the presence of typical IMPs. P faces of both membranes showed larger amounts of particles than E faces. Fracture of muscle plasma membrane revealed a linear array of particles disposed in parallel rows on its P face.

Antifilarial cellular responses detected in a Haitian pediatric population by use of a microblastogenesis assay.

Previous reports have demonstrated age-related shifts in antifilarial humoral immune responses in 6- to 10-year-old Haitian children; the responses consisted of elevated parasite-specific IgG2 and IgG3 in amicrofilaremic children and elevated IgG4 in microfilaremic children. In this study, the cell-mediated immune responses to soluble adult and microfilarial extracts of Brugia pahangi, determined by use of a microblastogenesis assay, were examined. Capillary blood samples were collected by finger prick from 176 Haitian children in an area with endemic Wuchereria bancrofti. Antigen-specific cellular responsiveness varied as a function of infection status but not age or sex; amicrofilaremic children had significantly greater responses to adult antigens than did microfilaremic children. Significant responses were detected in children less than 2 years of age; thus, correlations observed between filarial antigen-specific responses and infection status are established early in life.

Analysis of isotype-specific antifilarial antibody levels in a Haitian pediatric population.

Previous studies of antifilarial antibodies in a pediatric population residing in an area with endemic Wuchereria bancrofti filariasis have demonstrated age related shifts in antifilarial immunity. To further characterize humoral responses in Haitian children, serum samples from 129 patients (3 months-15 years of age) were analyzed by ELISA for isotype-specific antifilarial antibody responses. Age-stratified analysis of geometric mean antibody titers showed significant increases in antibody titers of all isotypes with age in the amicrofilaremic population. Antifilarial IgG1, 2, and 3 levels were higher in amicrofilaremic children than in microfilaremic children, significantly so for IgG2 and IgG3. In contrast, IgG4 antibody levels were higher in microfilaremic subjects than in amicrofilaremic subjects. A multivariate, unconditional, logistic regression model was developed from these data to predict infection status. The model correctly classified 91.6% of the amicrofilaremic subjects, but only 55.6% of the microfilaremic subjects.

Heightened anti-filarial immune responsiveness in a Haitian pediatric population.

The immunological consequences of exposure to filarial infection were examined by cross-sectional serological studies. Serum samples from 121 pediatric patients (18 months-15 years of age) were analyzed in parallel with a panel of sera from adults residing in the same area of Haiti. Parasite antigen specific IgG and IgE levels were determined by ELISA. IgG levels in children were significantly elevated in humoral immunoreactivity to Brugia pahangi extracts compared to adults. In addition, anti-filarial IgG levels in amicrofilaremic children were significantly greater than in microfilaremic children. In contrast, IgG levels in adults were equivalent independent of microfilaremic status. Anti-filarial IgE levels in sera from both children and adults were low in comparison to that of a subject with tropical pulmonary eosinophilia and were unrelated to clinical status. No correlations were found between humoral responses and age, sex, or degree of parasitemia. Sera from amicrofilaremic children and, to a lesser extent, adults recognize more antigens, particularly those of high molecular weight (greater than 55 kDa), than sera from microfilaremic patients.

South American brugian filariasis: report of a human infection acquired in Peru.

A 27-year-old white woman from New York City acquired an infection by a Brugia species while she camped in the Amazon basin of Peru. She was infected by at least one adult male worm and one gravid female worm. Both worms were intact and in a lymphatic vessel of a right cervical lymph node. The lymph node and surrounding fibroadipose tissue contained many microfilariae. The male worm was 50 micron wide and the female, 100 micron. Both worms had thin (1 micron) cuticles with fine transverse striations. There were 3 to 4 somatic muscle cells per quadrant. Microfilariae had tails characteristic of the genus Brugia. Although specific identification was not possible from the available material, the worm closely resembled Brugia guyanensis, a parasite of the coatimundi (Nasua nasua) and the only species of Brugia known in South America.

Brugia species in a man from western Ethiopia.

A case of human brugiasis in a student from Gambela, Ethiopia, is reported. Ten sheathed microfilariae showing the Brugia genus characteristics were recovered from 1 ml of blood.

Bancroftian filariasis in Haiti: preliminary characterization of the immunological responsiveness of microfilaremic individuals.

Patent infections with the lymphatic filariae, Wuchereria bancrofti and Brugia malayi, are associated with suppressed in vitro cellular responsiveness to filarial antigens. In studies of bancroftian filariasis in Haiti, a significant number of microfilaremic individuals can be characterized as "responders" to filarial antigens. Cells from 37/74 untreated microfilaremic subjects responded to B. pahangi antigen (stimulation ratio greater than 2) as detected by in vitro blastogenesis. A comparison of responders to nonresponders revealed a significant difference in mean B. pahangi reactivity (15,822 vs. 4,538 cpm, P less than 0.001), but no significant differences with respect to age, microfilaremia, PPD or PHA reactivity, or B. pahangi-specific antibody levels. Subtle differences may exist between these groups with respect to recognition of specific antigens on Western blots.

Lucha contra la filariasis linfática : Manual para personal sanitario

Este manual está destinado a quienes se encargan de planificar, administrar y ejecutar actividades de lucha conta la filariasis linfática. En él se describe un enfoque sistemático de la elaboración de estragegias nacionales que sean sencillas, económicas y orientadas a la comunidad, señalándose la manera en que los agentes de salud de la comunidad pueden llegar a participar en los esfuerzos de lucha contra la enfermedad, y la medida en que esa lucha puede realizarse mediante la participación de la comunidad. Además se describen métodos específicos de obtención de datos epidemiológicos fiables para la evaluación de la enfermedad y de las medidas de lucha

Publicado en inglés bajo WNSP/87-14

Control of lymphatic filariasis: A manual for health personnel

Publicado en español bajo WNSP/88-44

Mansonella ozzardi in Haiti. IV. Evaluation of antibody reactivity to heterologous antigens.

Sera from individuals in an area of Haiti endemic for Mansonella ozzardi were analyzed for reactivity to antigens of Brugia pahangi, Dirofilaria immitis, Mansonella llewellyni or Ascaris lumbricoides using either an enzyme-linked immunosorbent assay or an indirect immunofluorescent antibody test. IgM and IgG reactivity to all antigens was observed with sera from both microfilaremic and amicrofilaremic individuals when compared to reactivity of sera from individuals from nonendemic areas. Antibody reactivity to B. pahangi was greater than that to other antigens. IgG reactivity of sera from endemic patients to filarial antigens was consistently greater than that of IgM. Antibody reactivity was not correlated with age or microfilarial density.

[Filariasis in foreign immigrants]. / Filariosen bei eingereisten Ausländern.

Among the patients of the Clinic for Infectious and Tropical Diseases of the County Hospital St. George Leipzig the frequency of the infestment with microfilaria in immigrated foreigners was established. Of 1925 examined patients 78 (4.1%) were infested with microfilaria. In 27 patients we succeeded in proving Wuchereria bancrofti and in 3 Brugia malayi, 43 showed Acanthocheilonema perstans, in 5 cases a double infection was present.

Comparison of heterologous adult Brugia malayi and homologous Onchocerca volvulus antigen in the enzyme-linked immunosorbent assay (ELISA) for Guatemalan onchocerciasis.

To determine the susceptibility of a heterologous filarial antigen for measuring Onchocerca volvulus antibodies, worms were compared using an enzyme-linked immunosorbent assay (ELISA) test. Control serum samples from helminth-free U.S. residents and from helminth-infected but filariae-free Salvadoran residents were tested and compared with serum obtained from microfilariae-positive and -negative Guatemalan residents living in an area of endemic onchocerciasis. The results showed that none of the sera from U.S. residents had positive O. volvulus ELISA titers (greater than or equal to 1:160); however, 8.51% (4/47) had positive B. malayi ELISA titers (greater than or equal to 1:640). The geometric mean titers with the B. malayi ELISA test were higher than with the O. volvulus ELISA test--in sera from 47 U.S. residents (1:219 vs. 1:49), from 108 Salvadoran residents (1:92 vs. 1:71), and from 145 microfilariae-negative (1:539 vs. 1:167) and 303 microfilariae-positive (1:1,270 vs. 1:561) Guatemalan residents. The B. malayi ELISA test exhibited slightly less sensitivity than the homologous O. volvulus ELISA test; nevertheless, a good correlation (r = 0.74) was found between the 2 test antigens, indicating that the B. malayi antigen could be used to measure O. volvulus antibodies.

Enzootic Brugia infection in a two-year-old Colombian girl.

Mature male and female filarial worms were present in a lymphatic vessel near a retro-auricular lymph node removed from a 2-year old Colombian girl. Although apparently mature microfilariae were present in the uterus of the female, none was detected in blood samples (Knott's) of peripheral blood taken during day or night. The identification of the worms as a species of Brugia is suggested by their location in a dilated lymphatic vessel, morphology of adults, and the distribution pattern of tail nuclei of the microfilariae. This case is similar to another Colombian case reported from the Departamento del Santander del Sur, and suggests that zoonotic filarial infections may not be uncommon in Colombia.