Tropical pulmonary eosinophilia

Tropical pulmonary eosinophilia is one of the many PIE syndromes [pulmonary infiltrates with eosinophilia (of the peripheral blood)]. It is caused by immunologic hyperresponsiveness to the filarial parasites Wuchereria bancrofti or Brugia malayi. Its clinical presentation includes nocturnal cough, dyspnea, wheezing, fever, weight loss, fatigue, interstitial mottling on chest radiograph, predominantly restrictive but also obstructive lung function abnormalities, and peripheral blood eosinophilia of more than 3000 per microliter. It can be distinguished from other PIE syndromes by the patient's history of residence in the tropics, by the presence of extraordinarily high levels of both serum IgE and antifilarial antibodies, and by the dramatic clinical improvement after treatment with the antifilarial drug diethylcarbamazine. Recent studies indicate that the compromised lung diffusion capacity of patients with acute tropical pulmonary eosinophilia is a function of the degree of the eosinophilic alveolitis present and that, despite a 3-week course of diethylcarbamazine, low-grade alveolitis persists in almost half of such patients; this persistent alveolitis is likely to be the cause of the progressive interstitial fibrosis seen in many untreated or inadequately treated patients with tropical pulmonary eosinophilia.

Lack of IgG4 antibody response to carbohydrate antigens in patients with lymphatic filariasis

It has been suggested that humans are genetically restricted from making IgG4 antibody responses to carbohydrate antigens. To test this hypothesis we examined sera from 35 patients with bancroftian filariasis (an infection known to induce very high levels of IgG4 antibodies to the parasite and known to be associated with repeated streptococcal infections) as well as from 15 normal individuals for their IgG and IgG subclass responses to streptococcal protein [streptolysin-O (SO), deoxyribonuclease B (DB)] and carbohydrate [group A carbohydrate (GAC)] antigens. Levels of IgG antibodies to all three antigens were found to be significantly higher in the filariasis patients compared to normals (P less than 0.01), and the subclass composition of these antibodies proved heterogenous. Although responses to all three antigens included IgG1, IgG2 and IgG3 antibodies and although IgG4 responses to the proteins SO and DB were significantly higher in the filariasis patients than in normals (P less than 0.001), more importantly there were no detectable anti-GAC IgG4 antibodies in either study group. These observations, coupled with our earlier finding of the absence of IgG4 responses to phosphocholine (PC) in patients with lymphatic filariasis, suggest that even the chronic antigenic stimulation of filarial helminth infection, which leads to very prominent IgG4 responses to protein antigens, cannot overcome the genetic restriction in humans for making IgG4 antibodies to carbohydrate antigens, whether of parasite or non-parasite origin.

Interleukin-5 and the posttreatment eosinophilia in patients with onchocerciasis

To understand the role of the eosinophilopoietic cytokine IL-5 in humans, the posttreatment eosinophilic response in a group of microfilaria (mf)-positive patients with onchocerciasis (n = 10) was examined before and after treatment with diethylcarbamazine (6 mg/kg for 7 d). Sequential blood samples were assessed at 24 and 1 h before treatment (baseline values), then at frequent intervals over the next 14 d. Symptom scores, skin microfilariae (mf), and peripheral blood eosinophil counts were recorded as a function of time after treatment, and serum levels of IL-5 were quantitated by a highly sensitive (sensitivity greater than or equal to 20 pg/ml) monoclonal-based ELISA. Pretreatment eosinophil counts ranged from 240 to 1,186 eosinophils/microliter (geometric mean, 675), and the mf counts from 10 to 218 per mg skin (geometric mean, 79). After an initial decline in the peripheral eosinophil count to 28 +/- 8% of pretreatment levels at 8 h after beginning treatment, the eosinophil counts steadily increased over the next 2 wk, reaching a maximum at 14 d (257 +/- 38% of pretreatment levels). Serum levels of IL-5 rose sharply from pretreatment levels to a peak of 70.5 +/- 11 pg/ml by 24 h after treatment. Serum IL-5 remained elevated over the next 2-3 d and declined toward baseline by approximately 6 d after treatment, at which time the eosinophil levels were steadily increasing. IL-3 and granulocyte macrophage colony-stimulating factor, two other cytokines implicated in eosinophilopoeisis, were not detectable in the serum at any time before or after treatment. The rise in serum IL-5 before the posttreatment eosinophilia seen in this group of patients with onchocerciasis demonstrates a temporal relationship between IL-5 and the subsequent development of eosinophilia and implicates IL-5 as an important mediator of eosinophilia in humans.

A recombinant clone of Wuchereria bancrofti with DNA specificity for human lymphatic filarial parasites

In order to understand the immune response to Wuchereria bancrofti and to aid in the diagnosis of W. bancrofti infections, recombinant antigens were identified from a W. bancrofti genomic expression library made in lambda gt11 using a pool of sera from infected Indian patients. One of the recombinant clones, lambda WbN1, containing a 2.5-kb insert, reacted strongly to a pool of sera from patients with lymphatic filariasis but not to normal human sera. In addition, this clone showed restricted specificity at the genomic level to the major lymphatic filarial parasites W. bancrofti and Brugia malayi but not to the closely related filarial parasite Brugia pahangi or to other filarial and non-filarial species tested. Nucleotide sequence analysis indicated the cloned DNA to have homology to myosin-like myofibrillar proteins. Polymerase chain reaction amplification initiated by specific synthetic oligomers amplified DNA in a species-specific manner from as little as 16 pg of isolated DNA or from one microfilaria.

Loiasis in endemic and nonendemic populations: immunologically mediated differences in clinical presentation

To define the clinical spectrum of loiasis more precisely and to begin to assess the immunologic basis for the difference in clinical manifestations between visitors to endemic areas and natives of these areas, 51 West African patients with loiasis were evaluated and compared with 42 infected expatriates. Microfilaremia was present in 90% and Calabar swellings in only 16% of the endemic patients. Conversely, only 10% of the expatriates were microfilaremic while 95% complained of Calabar swellings. The endemic population showed significantly decreased levels of peripheral blood eosinophils, parasite-specific IgG, and lymphocyte proliferation to parasite antigens compared with the nonendemic population. These findings support the hypothesis that differences in the modulation of the immune response to parasite antigen are responsible for the observed differences in clinical presentation between expatriate and endemic populations with loiasis.

Immunity to onchocerciasis: recognition of larval antigens by humans putatively immune to Onchocerca volvulus infection

Immunoblot analyses were done using sera from 12 individuals without evidence of onchocerciasis and 16 with active infection from an area of Guatemala holoendemic for onchocerciasis. For adult antigens from Onchocerca volvulus, no differences in antigen recognition could be identified between the two groups. In contrast, when infective larval (L3) antigen preparations derived from the related animal parasite Onchocerca lienalis were used, IgG from the "immune" individuals preferentially recognized a 45- to 50-kDa triplet and a 22-kDa L3 antigen. When L3 antigens of Brugia malayi were used, sera from putatively immune individuals identified a high-molecular-weight triplet/quadruplet plus several additional antigens of lower molecular weights that were recognized by sera from few (or none) of the infected patients. These findings define some differences in antibody specificity in onchocerciasis patients and therefore might define potential target antigens of humoral host defense. The exact nature of such defenses is unknown.

An immunogenic Onchocerca volvulus antigen: a specific and early marker of infection

Onchocerciasis (river blindness) is a serious health problem and a severe obstacle to social and economic development, especially in Africa. A complementary DNA fragment coding for an Onchocerca volvulus antigen (OV-16) was cloned and expressed in the plasmid vector pCG808fx. Immune responses to this O. volvulus-specific recombinant antigen were detectable in patients with documented onchocerciasis; the antibody response was also detectable at 3 months and at more than 1 year before infection could otherwise be detected in humans and in chimpanzees experimentally infected with O. volvulus third-stage larvae.

Frequency analysis of IgE-secreting B lymphocytes in persons with normal or elevated serum IgE levels

The immunoregulatory mechanisms that determine the high serum IgE antibody levels in disorders such as helminth parasite infections and the hyper-IgE recurrent infection syndrome (HIE) remain poorly understood. To assess whether elevated serum IgE levels result from an increased number of B lymphocytes committed to IgE production, the proportion of IgE-producing B lymphocytes was determined by a filter immunoplaque assay using PBMC from persons with a broad range of serum IgE levels that included normal persons (n = 9) and patients with loiasis (n = 12), tropical pulmonary eosinophilia (TPE) (n = 6), lymphatic filariasis (n = 28), and HIE (n = 8). PBMC from these persons were assessed for production of in vitro IgE. The geometric mean number of IgE-secreting cells in 10(5) B lymphocytes in PBMC was 0.42 (range 0-2.2) in normal persons, 5.6 (range 0.1-35.5) among patients with loiasis, 9.4 (range 0-53.2) among patients with lymphatic filariasis, 52 (range 31.5-115) among patients with TPE, and 218 (range 56-1404) among patients with HIE. When all study subjects were grouped, there were significant correlations with serum IgE levels (r2 = 0.78; p less than 0.0001) and net spontaneous in vitro IgE production (r2 = 0.8; p less than 0.0001). Estimates of the amount of IgE production per B lymphocyte were similar among normal persons, patients with filarial infections, and patients with TPE (geometric means of 134, 96, and 141 pg/ml/cell, respectively); in contrast, for HIE patients, IgE production by individual B cells was significantly lower (geometric mean 28 pg/ml/cell; p less than 0.001). These observations demonstrate that clonal expansion of IgE-producing B lymphocytes is a major mechanism underlying the elevated serum IgE levels seen in persons with hyper-IgE states.

Frequency analysis of IgE-secreting B lymphocytes in persons with normal or elevated serum IgE levels

The immunoregulatory mechanisms that determine the high serum IgE antibody levels in disorders such as helminth parasite infections and the hyper-IgE recurrent infection syndrome (HIE) remain poorly understood. To assess whether elevated serum IgE levels result from an increased number of B lymphocytes committed to IgE production, the proportion of IgE-producing B lymphocytes was determined by a filter immunoplaque assay using PBMC from persons with a broad range of serum IgE levels that included normal persons (n = 9) and patients with loiasis (n = 12), tropical pulmonary eosinophilia (TPE) (n = 6), lymphatic filariasis (n = 28), and HIE (n = 8). PBMC from these persons were assessed for production of in vitro IgE. The geometric mean number of IgE-secreting cells in 10(5) B lymphocytes in PBMC was 0.42 (range 0-2.2) in normal persons, 5.6 (range 0.1-35.5) among patients with loiasis, 9.4 (range 0-53.2) among patients with lymphatic filariasis, 52 (range 31.5-115) among patients with TPE, and 218 (range 56-1404) among patients with HIE. When all study subjects were grouped, there were significant correlations with serum IgE levels (r2 = 0.78; p less than 0.0001) and net spontaneous in vitro IgE production (r2 = 0.8; p less than 0.0001). Estimates of the amount of IgE production per B lymphocyte were similar among normal persons, patients with filarial infections, and patients with TPE (geometric means of 134, 96, and 141 pg/ml/cell, respectively); in contrast, for HIE patients, IgE production by individual B cells was significantly lower (geometric mean 28 pg/ml/cell; p less than 0.001). These observations demonstrate that clonal expansion of IgE-producing B lymphocytes is a major mechanism underlying the elevated serum IgE levels seen in persons with hyper-IgE states.

B cell responses to paramyosin. Isotypic analysis and epitope mapping of filarial paramyosin in patients with onchocerciasis

To examine the fine specificity of the human immune response to filarial paramyosin, the antigenicity of an expressed rcDNA (2.55 kb) of Dirofilaria immitis paramyosin was detailed by ELISA. Using sera from patients infected with Onchocerca volvulus, we analyzed both the entire paramyosin molecule and six subcloned fragments for their IgG, IgG subclasses, and IgE responses. Patients from both Guatemala (64% positive) and Ghana (100% positive) reacted to paramyosin with specific IgG levels above normal controls. Although there was no anti-paramyosin subclass restriction common to all patients, the IgG3 response in the Ghananians was significantly greater than that of Guatemalans (p less than 0.001). IgE anti-paramyosin responses showed positive correlations with IgG2 (p less than 0.001), IgG4 (p less than 0.002), and IgG1 (p less than 0.04) responses. Epitope mapping using the IgG response to the six subclones demonstrated preferential recognition of the amino terminal end of the molecule (nucleotides 1 to 360). IgG2 reactivity was clearly localized to the most amino-terminal 120 amino acids, and the IgG4 antibodies recognized amino acids immediately adjacent to this fragment. These studies examining the fine specificity of anti-filarial immune reactions should provide a method for understanding how parasites either evade or induce host immune responses.

B cell responses to paramyosin. Isotypic analysis and epitope mapping of filarial paramyosin in patients with onchocerciasis

To examine the fine specificity of the human immune response to filarial paramyosin, the antigenicity of an expressed rcDNA (2.55 kb) of Dirofilaria immitis paramyosin was detailed by ELISA. Using sera from patients infected with Onchocerca volvulus, we analyzed both the entire paramyosin molecule and six subcloned fragments for their IgG, IgG subclasses, and IgE responses. Patients from both Guatemala (64% positive) and Ghana (100% positive) reacted to paramyosin with specific IgG levels above normal controls. Although there was no anti-paramyosin subclass restriction common to all patients, the IgG3 response in the Ghananians was significantly greater than that of Guatemalans (p less than 0.001). IgE anti-paramyosin responses showed positive correlations with IgG2 (p less than 0.001), IgG4 (p less than 0.002), and IgG1 (p less than 0.04) responses. Epitope mapping using the IgG response to the six subclones demonstrated preferential recognition of the amino terminal end of the molecule (nucleotides 1 to 360). IgG2 reactivity was clearly localized to the most amino-terminal 120 amino acids, and the IgG4 antibodies recognized amino acids immediately adjacent to this fragment. These studies examining the fine specificity of anti-filarial immune reactions should provide a method for understanding how parasites either evade or induce host immune responses.

Persistent lower respiratory tract inflammation associated with interstitial lung disease in patients with tropical pulmonary eosinophilia following conventional treatment with diethylcarbamazine

Tropical pulmonary eosinophilia (TPE) presents as an acute syndrome with dyspnea, fluffy infiltrates, and rounded opacities on the chest radiograph, reduced lung function, marked eosinophilia in the blood and lower respiratory tract, and high titers of specific IgE and IgG antifilarial antibodies. The standard therapy for TPE is a 3-wk course of diethylcarbamazine (DEC) following which there is almost always a marked improvement in all parameters. However, clinical observations suggest that the disease can persist despite DEC therapy and lead to chronic dyspnea with restrictive lung impairment. To evaluate the concept that DEC therapy is not completely "curative" for TPE, but rather leaves most individuals with a mild, chronic form of TPE defined by persistent inflammation of the lower respiratory tract, we evaluated 23 individuals an average of 12 +/- 2 months following a standard 3-wk course of diethylcarbamazine for acute TPE. In the majority there were mild, persistent symptoms referrable to the lung, chest X-ray abnormalities, blood eosinophilia, and elevated serum IgE and filarial specific IgG. On the average, lung function was consistent with the presence of chronic, mild interstitial lung disease. When the inflammatory cells from the lower respiratory tract were examined, there was a persistent eosinophilic alveolitis (TPE/post-DEC 1769 +/- 376 eosinophils/microliters epithelial lining fluid; normal subjects 256 +/- 38, p less than 0.02). Evaluation of the lower respiratory tract inflammatory cells recovered from the TPE/post-DEC-treated individuals demonstrated spontaneous release of exaggerated amounts of O2-. and H2O2 compared to normal subjects (p less than 0.05, both comparisons).(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in antibody profile after treatment of human onchocerciasis

To define the changes in antibody response to Onchocerca volvulus antigens after treatment of patients with onchocerciasis, IgG and IgE antibodies were examined quantitatively and qualitatively in 21 patients and 3 control individuals before and sequentially for 14 days after treatment with diethylcarbamazine. The quantitative levels of IgE and IgG responses (both polyclonal and O. volvulus-specific) remained essentially unchanged for all patients, but 9 of the 21 patients showed intensified responses to one or more parasite-specific antigens, and 8 of 21 developed antibodies to previously undetected antigens. There was a significant correlation between the intensities of infection and the development of newly recognized anti-O. volvulus antibodies. These studies demonstrate that O. volvulus-specific IgE and IgG antibody responses are, at least transiently, enhanced by treatment with diethylcarbamazine and that after treatment, parasites possibly release antigens previously hidden from the host's immune response.

Regulation of parasite-induced eosinophilia: selectively increased interleukin 5 production in helminth-infected patients

Production of the eosinophilogenic cytokines interleukin 3 (IL-3), granulocyte/macrophage colony-stimulating factor (GM-CSF), and IL-5 by mitogen-stimulated peripheral blood mononuclear cells was compared between 11 noneosinophilic individuals and seven patients with helminth-induced eosinophilia. Both the kinetics and quantities of IL-3 and GM-CSF were similar in the two groups. In contrast, IL-5 production at both the protein and the mRNA level was markedly greater in the eosinophilic patients, an observation suggesting that IL-5 may be particularly important in mediating the selective eosinophilia seen in filarial and other helminth infections.

Cytokine regulation of antigen-driven immunoglobulin production in filarial parasite infections in humans

To define the immunoregulatory mechanisms underlying serum IgE levels found in patients with filariasis, we studied polyclonal IgE production by peripheral blood mononuclear cells (PBMC) from 15 patients with filarial infections, with a focus on the role of interleukin-4 (IL-4) and interferon-gamma (IFN-gamma) in the generation and regulation of the response. Spontaneous in vitro IgE production was elevated in 10 of the 15 patients (836-6,464 pg/ml; normals, less than 500 pg/ml). Addition of filarial parasite antigen to PBMC cultures significantly stimulated polyclonal IgE production in an antigen dose-dependent manner in 10 of 12 patients tested (P less than 0.001). The essential role of IL-4 in the generation of this response was demonstrated when simultaneous addition of anti-IL-4 completely inhibited antigen-stimulated IgE production in all 10 patients studied. An inhibitory role of endogenously produced IFN-gamma was also indicated when the addition of anti-IFN-gamma to the cultures significantly augmented filarial antigen-stimulated IgE production by 33-1,238% in these same patients. Addition of 10-1,000 U/ml of recombinant human IFN-gamma to PBMC completely inhibited parasite antigen-induced IgE production. This study demonstrates that filarial antigen-stimulated IgE production in patients with filariasis is mediated by IL-4 and down regulated by IFN-gamma and suggests that the amount of IgE produced depends on the relative quantity of IL-4 and IFN-gamma generated by parasite-specific T cells.

Eosinophil degranulation. An immunologic determinant in the pathogenesis of the Mazzotti reaction in human onchocerciasis

Onchocerciasis patients treated with diethylcarbamazine often undergo a severe inflammatory response, the Mazzotti reaction. To assess the eosinophil's role in the pathogenesis of the Mazzotti reaction, we obtained serial blood, plasma, and skin biopsy specimens from 21 heavily infected patients and 3 endemic controls, both before and during therapy with diethylcarbamazine. Samples were analyzed for blood eosinophils, plasma levels of eosinophil granule major basic protein (MBP) and eosinophil-derived neurotoxin, eosinophil infiltration and eosinophil and mast cell degranulation in the skin. After the first dose of diethylcarbamazine, blood eosinophils fell from a pre-treatment level of 888 +/- 111 to 203 +/- 42 cells/mm3 at 8 h. This decrease was followed by a marked eosinophilia developing over the remaining 7 days of treatment and 14 days of follow-up. Plasma eosinophil-derived neurotoxin levels increased from 56 +/- 4 ng/ml pretreatment to a peak of 82 +/- 9 ng/ml at 8 h and returned to pretreatment levels by 48 h. Beginning at 12 h, plasma MBP levels increased from 730 +/- 74 ng/ml pretreatment to a peak of 1140 +/- 74 ng/ml after 5 days. Pretreatment skin biopsies stained for MBP by immunofluorescence showed a bright fibrillar pattern in the dermis consistent with chronic eosinophil degranulation; the MBP was localized on elastic tissue fibers. After treatment, skin biopsy specimens showed both the pretreatment fibrillar MBP staining pattern as well as focal eosinophil degranulation. Deposition of MBP around microfilariae in the papillary dermis was visible as early as 1.5 h. The lowest blood eosinophil levels and peak plasma eosinophil-derived neurotoxin levels coincided with the infiltration and degranulation of eosinophils in the skin. Mast cell degranulation in the skin was maximal by the first posttreatment biopsy (1.5 h) coincident with the beginning of eosinophil degranulation. Although the pathogenesis of the Mazzotti reaction is clearly complex, our results indicate that eosinophil degranulation is characteristic of the response and that it occurs with a time course suggestive of a role for the eosinophil in determining the clinical and pathologic manifestations of the reaction.

Eosinophil degranulation. An immunologic determinant in the pathogenesis of the Mazzotti reaction in human onchocerciasis

Onchocerciasis patients treated with diethylcarbamazine often undergo a severe inflammatory response, the Mazzotti reaction. To assess the eosinophil's role in the pathogenesis of the Mazzotti reaction, we obtained serial blood, plasma, and skin biopsy specimens from 21 heavily infected patients and 3 endemic controls, both before and during therapy with diethylcarbamazine. Samples were analyzed for blood eosinophils, plasma levels of eosinophil granule major basic protein (MBP) and eosinophil-derived neurotoxin, eosinophil infiltration and eosinophil and mast cell degranulation in the skin. After the first dose of diethylcarbamazine, blood eosinophils fell from a pre-treatment level of 888 +/- 111 to 203 +/- 42 cells/mm3 at 8 h. This decrease was followed by a marked eosinophilia developing over the remaining 7 days of treatment and 14 days of follow-up. Plasma eosinophil-derived neurotoxin levels increased from 56 +/- 4 ng/ml pretreatment to a peak of 82 +/- 9 ng/ml at 8 h and returned to pretreatment levels by 48 h. Beginning at 12 h, plasma MBP levels increased from 730 +/- 74 ng/ml pretreatment to a peak of 1140 +/- 74 ng/ml after 5 days. Pretreatment skin biopsies stained for MBP by immunofluorescence showed a bright fibrillar pattern in the dermis consistent with chronic eosinophil degranulation; the MBP was localized on elastic tissue fibers. After treatment, skin biopsy specimens showed both the pretreatment fibrillar MBP staining pattern as well as focal eosinophil degranulation. Deposition of MBP around microfilariae in the papillary dermis was visible as early as 1.5 h. The lowest blood eosinophil levels and peak plasma eosinophil-derived neurotoxin levels coincided with the infiltration and degranulation of eosinophils in the skin. Mast cell degranulation in the skin was maximal by the first posttreatment biopsy (1.5 h) coincident with the beginning of eosinophil degranulation. Although the pathogenesis of the Mazzotti reaction is clearly complex, our results indicate that eosinophil degranulation is characteristic of the response and that it occurs with a time course suggestive of a role for the eosinophil in determining the clinical and pathologic manifestations of the reaction.

A controlled trial of ivermectin and diethylcarbamazine in lymphatic filariasis

Ivermectin is a new antifilarial drug that can be given in a single oral dose. To compare the efficacy and side effects of ivermectin with those of diethylcarbamazine, the standard antifilarial treatment, we conducted a randomized, double-blind trial in 40 South Indian men with lymphatic filariasis caused by Wuchereria bancrofti. Patients were randomly assigned to one of three treatments: a single low dose of ivermectin (mean [+/- SE], 21.3 +/- 0.7 micrograms per kilogram of body weight; n = 13) followed by placebo for 12 days; a single high dose of ivermectin (mean, 126.2 +/- 3.7 micrograms per kilogram; n = 13) followed by placebo for 12 days; or diethylcarbamazine for 13 days (6 mg per kilogram per day for 12 days preceded by 3 mg per kilogram for 1 day; n = 14). Eleven patients were initially assigned to receive placebo and after five days were reassigned to one of the three treatment groups. At day 12 there was complete clearance of microfilariae from the blood in all 26 men who took ivermectin and in 11 of the 14 men who took diethylcarbamazine. At six months the numbers of detectable microfilariae (as a percentage of the pretreatment values) were 18.3 percent after low-dose ivermectin and 19.5 percent after high-dose ivermectin, as compared with 6.0 percent after diethylcarbamazine (P less than 0.05). The side effects were confined to the first five days and were similar in the three treatment groups. We conclude that in lymphatic filariasis, the clinical response to a single dose of ivermectin compares favorably with that after the standard 12-day course of diethylcarbamazine. Given the practical advantages of single-dose administration, ivermectin should become a useful medication for the control of bancroftian filariasis.

Tropical pulmonary eosinophilia: analysis of antifilarial antibody localized to the lung

Acute tropical pulmonary eosinophilia (TPE) is characterized by wheezing, pulmonary infiltrates, marked peripheral blood eosinophilia, and very high serum levels of filaria-specific antibodies. To evaluate the amount and character of the filaria-specific antibodies in the lungs in this disorder, bronchoalveolar lavage was carried out in individuals with acute TPE, in normal subjects, and in patients with elephantiasis or asthma. Striking elevations of total IgE were found in the lower respiratory tract epithelial lining fluid (ELF) of patients with TPE along with high levels of filarial-specific IgG, IgM, and IgE. When patients with acute TPE were treated with diethylcarbamazine and evaluated again 6-14 d later, there was marked reduction in ELF parasite-specific IgG and IgE, which paralleled a rapid clinical response. Immunoblot comparison of the antigen recognition patterns of ELF and serum antibodies demonstrated a general similarity in parasite antigens recognized, but the lung IgE and IgG antibodies appeared to recognize only a certain subset of the parasite antigens recognized by serum antibodies. Thus, a profound antibody response to filarial infection is found in the lungs of patients with TPE, suggesting that these filaria-specific antibodies play an important role in the pathogenesis of this disorder.

Phosphocholine epitopes on helminth and protozoal parasites and their presence in the circulation of infected human patients

Antigens containing phosphocholine (PC) circulate in the blood during chronic filarial infection. Because of the wide occurrence of such PC epitopes, we examined their specificity by evaluating 10 common parasites of humans for the presence of PC epitopes, and sera from patients infected with these parasites for circulating antigens containing PC. Immunoblot analysis of extracts from various parasites using an anti-PC monoclonal antibody (CA101) demonstrated the presence of PC epitopes on the protozoa Leishmania major and Trypanosoma cruzi, and on the helminths Schistosoma mansoni and Strongyloides stercoralis, in addition to those previously described on Trichinella spiralis, Onchocerca volvulus and Brugia malayi. They were not detected on the protozoa Entamoeba histolytica, Giardia lamblia or Plasmodium falciparum. Sera from 163 individuals with single protozoan or helminth infections were assayed for PC-bearing circulating antigens in a two-site immunoassay; such antigens were found in almost all patients infected with Wuchereria bancrofti; in half of those infected with S. stercoralis; and in 7-15% of those with S. mansoni, T. cruzi or L. donovani; none was detected in those with Trichinella, hookworm, Echinococcus, malaria, Giardia or amoebic infections. Thus, while detection of circulating PC-antigen as an immunodiagnostic assay for filariasis could result in some 'false positives', it appears to be a potentially valuable immunodiagnostic tool that deserves wider field testing to determine its practical usefulness.

Immunopathology of ocular onchocerciasis. I. Inflammatory cells infiltrating the anterior segment

Ocular tissue (conjunctiva and iris) was obtained from 12 adult African men with active ocular onchocerciasis and from nine age-matched persons from the same endemic region but without onchocercal infection. These tissues were examined immunohistologically and two major findings were noted. First, mild-to-moderate chronic inflammatory cellular infiltration was present in the conjunctiva of the onchocerciasis patients. T lymphocytes (CD3+) were the major inflammatory cells, and the T suppressor/cytotoxic (CD8+) subset was significantly increased in the ocular onchocerciasis patients (P less than 0.03). Second, in the onchocerciasis patients, non-lymphoid cells of the conjunctiva and iris, such as vascular endothelium, pericytes and fibroblasts were in an activated state, as shown by increased expression of Class II MHC antigens (P less than 0.02, conjunctiva; P less than 0.05, iris). These concomitant findings of lymphocyte infiltration and resident cell activation indicate a dynamic state of localized host responsiveness presumably to the microfilarial parasites and their products in the anterior segments of the eyes of patients with ocular onchocerciasis.

Lymphocyte subpopulations in Bancroftian filariasis: activated (DR+) CD8+ T cells in patients with chronic lymphatic obstruction

To examine the relationship between lymphocyte phenotypes and states of activation in patients with Bancroftian filariasis, dual colour flow cytometry and concurrent in vitro cell culture were performed on normal individuals (NV; n = 15), and on patients with either asymptomatic microfilaraemia (MF; n = 12) or elephantiasis (CP; n = 11). In contrast to findings by others in a population with Brugian filariasis, the percentages of total B lymphocytes (CD19), T lymphocytes (CD3), helper/inducer T lymphocytes (CD4), and suppressor/cytotoxic T lymphocytes (CD8) in both patient groups were found to be within the range defined by clinically normal individuals. Furthermore, there were no differences among the groups in the expression of the IL-2 receptor (CD25) on T cells. There was, however, a significantly greater proportion (P less than 0.01) of 'activated' cytotoxic/suppressor lymphocytes (defined by co-expression of CD8 and HLA-DR) in patients with elephantiasis (16.4 +/- 8.6%) than in the MF (8.9 +/- 2.6%) or NV (8.3 +/- 2.9%) groups. Further, when the expression of this activation antigen was examined in parallel with in vitro mitogen responsiveness, an inverse correlation between the percentage of CD8+ HLA-DR+ lymphocytes and pokeweed mitogen-induced proliferation was seen (r = -0.54; P less than 0.001). These data provide further definition of the immunoregulatory abnormalities seen in human filarial infections and suggest that activated CD8+ T lymphocytes may be involved in the pathogenesis of the chronic obstructed lymphatic form of this disease.

Selective up-regulation of endothelial cell class I MHC expression by cytokines from patients with lymphatic filariasis

Local host immune responses to the lymphatic-dwelling filarial parasite Wuchereria bancrofti are important in the pathogenesis of the lymphangitis that leads to filarial elephantiasis. That the lymphatic endothelial cells may be important in this inflammatory process was shown by the ability of supernatants generated from filarial Ag-driven PBMC of individuals with filarial elephantiasis caused by W. bancrofti infection to up-regulate class I MHC expression on human umbilical vein endothelial cells when compared to unstimulated control supernatants from the same individual (relative fluorescence intensity = 159% +/- 13.5; p less than 0.001). In contrast, individuals with the same filarial infection but manifesting no lymphatic disease were unable to generate, in response to filarial Ag the cytokines required for this activation (relative fluorescence intensity = 93% +/- 2.6). Supernatants induced by a non-filarial Ag (purified protein derivative) were able to effect class I MHC up-regulation in both patient groups. The same filarial Ag-driven supernatants did not cause detectable class II MHC staining on human umbilical vein endothelial cells. These results suggest a likely role for parasite Ag-driven, cytokine-mediated endothelial cell activation in the pathogenesis of lymphatic inflammatory/obstructive filarial disease.

Selective up-regulation of endothelial cell class I MHC expression by cytokines from patients with lymphatic filariasis

Local host immune responses to the lymphatic-dwelling filarial parasite Wuchereria bancrofti are important in the pathogenesis of the lymphangitis that leads to filarial elephantiasis. That the lymphatic endothelial cells may be important in this inflammatory process was shown by the ability of supernatants generated from filarial Ag-driven PBMC of individuals with filarial elephantiasis caused by W. bancrofti infection to up-regulate class I MHC expression on human umbilical vein endothelial cells when compared to unstimulated control supernatants from the same individual (relative fluorescence intensity = 159% +/- 13.5; p less than 0.001). In contrast, individuals with the same filarial infection but manifesting no lymphatic disease were unable to generate, in response to filarial Ag the cytokines required for this activation (relative fluorescence intensity = 93% +/- 2.6). Supernatants induced by a non-filarial Ag (purified protein derivative) were able to effect class I MHC up-regulation in both patient groups. The same filarial Ag-driven supernatants did not cause detectable class II MHC staining on human umbilical vein endothelial cells. These results suggest a likely role for parasite Ag-driven, cytokine-mediated endothelial cell activation in the pathogenesis of lymphatic inflammatory/obstructive filarial disease.