Chronic helminth infection burden differentially affects haematopoietic cell development while ageing selectively impairs adaptive responses to infection.

Throughout the lifespan of an individual, the immune system undergoes complex changes while facing novel and chronic infections. Helminths, which infect over one billion people and impose heavy livestock productivity losses, typically cause chronic infections by avoiding and suppressing host immunity. Yet, how age affects immune responses to lifelong parasitic infection is poorly understood. To disentangle the processes involved, we employed supervised statistical learning techniques to identify which factors among haematopoietic stem and progenitor cells (HSPC), and both innate and adaptive responses regulate parasite burdens and how they are affected by host age. Older mice harboured greater numbers of the parasites' offspring than younger mice. Protective immune responses that did not vary with age were dominated by HSPC, while ageing specifically eroded adaptive immunity, with reduced numbers of naïve T cells, poor T cell responsiveness to parasites, and impaired antibody production. We identified immune factors consistent with previously-reported immune responses to helminths, and also revealed novel interactions between helminths and HSPC maturation. Our approach thus allowed disentangling the concurrent effects of ageing and infection across the full maturation cycle of the immune response and highlights the potential of such approaches to improve understanding of the immune system within the whole organism.

Filariasis presenting as multiple subcutaneous nodules: a rare case report.

Filariasis presenting as multiple subcutaneous nodules is very rare and only a very few cases are reported in the literature. Microfilaria bancrofti is known to occur in different sites like breast, thyroid, lymph nodes, liver, lungs and body fluids, however, in contrast to the other filarial species, its occurrence in soft tissues is rarely reported. Conventional method of diagnosis of filariasis is by demonstration of microfilaria in peripheral blood smear which may be diurnal or nocturnal. The various species are differentiated by the morphological features like presence or absence of sheath, granules and nuclear arrangement in the tail end. We hereby report an unusual case of Wuchereria bancrofti infestation diagnosed on biopsy of subcutaneous nodule in a patient whose initial clinical presentation was of urticarial rashes over the upper extremities. In differential diagnosis of various subcutaneous nodular masses the possibility of filarial granuloma must be kept and a careful search should be done for adult worm or microfilaria in the serial tissue sections.

Pleural cellular reaction to the filarial infection Litomosoides sigmodontis is determined by the moulting process, the worm alteration, and the host strain.

The filarial nematode Litomosoides sigmodontis model was used to decipher the complex in vivo relationships between filariae, granulomas and leukocytes in the host's pleural cavity. The study was performed from D5 p.i.: to D47 p.i. in resistant C57BL/6 mice, to D74 p.i. in susceptible BALB/c mice, and to D420 p.i. in permissive jirds. We showed that, during the first month, leukocytes only clustered as granulomas around shed cuticles (exuviae) and with eosinophils as the major constituents. In addition, carbohydrates residues became abundant on exuviae only, suggesting a glycan-dependent mechanism of eosinophil attachment. Neutrophils were absent from the pleural cavity of all rodents and from the murine granulomas, but they made up 25% of the granuloma cell population in jirds. After the first month of infection granulomas formed around developed adult worms and morphological evidence suggested that leukocytes preferentially clustered around altered, but still motile, worms. No carbohydrates were detected on these worms and neutrophils were abundant in those granulomas. Finally, a rare third type of granuloma was observed in the resistant mice only; they contained young newly moulted adult worms; typically these granulomas were attached to the lateral lines of the worm via eosinophils; this feature correlated with the persistence of carbohydrate residues on the worms' lateral lines. Neutrophils were always in low proportion in all granulomas from resistant mice, suggesting difference in their adhesive properties in these mice. In vitro neutrophil recruitment in resistant mice was similar to that observed in susceptible mice although they expressed less cell surface CD11b.

Prevalence of filariasis in symptomatic patients in Moyen Chari district, south of Chad.

Filarial parasites infect an estimated 140 million people worldwide. Wuchereria bancrofti, Onchocerca volvulus, Loa loa and Mansonella perstans are responsible for most filarial infections in sub-Saharan Africa. We describe the prevalence and the clinical characteristics of filariasis in symptomatic patients in Goundi Sanitary district:167 patients were enrolled (99 men, 68 women). M. perstans microfilariae were isolated in peripheral blood in 164 cases, while Loa loa and Wuchereria bancrofti filariasis were diagnosed in only six and three cases, respectively. The most frequent filariasis observed in our study were due to M. perstans and L. loa, while the few cases of W. bancrofti filariasis seem to have been acquired abroad. No cases of O. volvulus were observed. Microfilarial burden was not related to symptoms, but a correlation between eosinophilia and pruritus was evident. No relationship was observed between eosinophils and symptoms. The prevalence observed in symptomatic patients could reflect the real prevalence of filariasis.

Brugia malayi asparaginyl-transfer RNA synthetase induces chemotaxis of human leukocytes and activates G-protein-coupled receptors CXCR1 and CXCR2.

Background. Lymphatic filariasis is a chronic human parasitic disease in which the parasites repeatedly provoke acute and chronic inflammatory reactions in the host bloodstream and lymphatics. Excretory-secretory products derived from filariae are believed to play an important role in the development of associated immunologic conditions; however, the specific mechanisms involved in these changes are not well understood. Recently, human cytoplasmic aminoacyl-transfer (t) RNA synthetases, which are autoantigens in idiopathic inflammatory myopathies, were shown to activate chemokine receptors on T lymphocytes, monocytes, and immature dendritic cells by recruiting immune cells that could induce innate and adaptive immune responses. Filarial (Brugia malayi) asparaginyl-tRNA synthetase (AsnRS) is known to be an immunodominant antigen that induces strong human immunoglobulin G3 responses.Methods. Recombinant B. malayi AsnRS was used to perform cellular function assays--for example, chemotaxis and kinase activation assays.Results. Unlike human AsnRS, parasite AsnRS is chemotactic for neutrophils and eosinophils. Recombinant B. malayi AsnRS but not recombinant human AsnRS induced chemotaxis of CXCR1 and CXCR2 single-receptor-transfected HEK-293 cell lines, blocked CXCL1-induced calcium flux, and induced mitogen-activated protein kinase.Conclusions. Our findings suggest that a filarial parasite chemoattractant protein may contribute to the development of chronic inflammatory disease and that chemokine receptors may be therapeutic targets to ameliorate parasite-induced pathology.

Quantitative appraisal of murine filariasis confirms host strain differences but reveals that BALB/c females are more susceptible than males to Litomosoides sigmodontis.

Litomosoides sigmodontis, a rodent filarial nematode, can infect inbred laboratory mice, with full development to patency in the BALB/c strain. Strains such as C57BL/6 are considered resistant, because although filarial development can occur, circulating microfilariae are never detected. This model system has, for the first time, allowed the power of murine immunology to be applied to fundamental questions regarding susceptibility to filarial nematode infection. As this is a relatively new model, many aspects of the biology remain to be discovered or more clearly defined. We undertook a major analysis of 85 experiments, to quantitatively assess differences in filarial survival and reproduction in male versus female and BALB/c versus C57BL/6 mice over the full course of infection. This large dataset provided hard statistical support for previous qualitative reviews, including observations that the resistant phenotype of C57BL/6 mice is detectable as early as 10 days postinfection (dpi). An unexpected finding, however, was that filarial survival was reduced in male BALB/c mice compared to their female counterparts. Worm recovery as well as the prevalence and density of microfilariae were higher in female compared with male BALB/c mice. Therefore, L. sigmodontis bucks the filarial trend of increased susceptibility in males. This could be partially explained by the different anatomical locations of adult L. sigmodontis versus lymphatic filariae. Interestingly, the effects of BALB/c sex upon microfilaremia were independent of worm number. In summary, this study has significantly refined our understanding of the host-L. sigmodontis relationship and, critically, has challenged the dogma that males are more susceptible to filarial infection.

Subversion of immunological signalling by a filarial nematode phosphorylcholine-containing secreted product.

Modulation of immune responses is an important strategy employed by pathogens to enable their survival in host organisms. Secreted immunomodulatory molecules are key weapons in the pathogen's battle with the host immune system. In this review, we will discuss the immunomodulatory effects of the phosphorylcholine-containing filarial nematode glycoprotein, ES-62, on the host immune system and summarise the results of our studies to identify the intracellular signalling pathways targeted by ES-62 to achieve these effects.

The role of endosymbiotic Wolbachia bacteria in filarial disease.

In this review, we describe the pathogenic role of Wolbachia endosymbiotic bacteria in filarial diseases, focusing on the host innate immune responses to filarial and Wolbachia products. A description of the host pathogen recognition and early inflammatory responses including TLR4-mediated signalling, chemokine and cytokine responses and inflammatory cell recruitment is provided from human studies and from animal models of filarial disease. Finally, the impact of the discovery and characterization of Wolbachia on filarial research and treatment programmes is discussed.

Resistance and susceptibility to filarial infection with Litomosoides sigmodontis are associated with early differences in parasite development and in localized immune reactions.

In order to understand natural resistance to filariasis, we compared Litomosoides sigmodontis primary infection of C57BL/6 mice, which eliminate the worms before patency, and BALB/c mice, in which worms complete their development and produce microfilariae. Our analysis over the first month of infection monitoredmigration of the infective larvae from the lymph nodes to the pleural cavity, where the worms settle. Although immune responses from the mouse strains differed from the outset, the duration of lymphatic migration (4 days) and filarial recovery rates were similar, thus confirming that the proportion of larvae that develop in the host species upon infection is not influenced by host genetic variability. The majority of worms reached the adult stage in both mouse strains; however, worm growth and molting were retarded in resistant C57BL/6 mice. Surprisingly, the only immune responses detected at 60 h postinfection occurred in the susceptible mice and only upon stimulation of cells from lymph nodes draining the inoculation site with infective larva extract: massive production of interleukin-6 (IL-6) and IL-5 (the latter cytokine was previously suspected to have an effect on L. sigmodontis growth). However, between days 10 and 30 postinfection, extraordinarily high levels of type 1 and type 2 cytokines and expansion of pleural leukocyte infiltration were seen in the resistant C57BL/6 mice, explaining the destruction of worms later. Our results suggest that events early in the infection determine susceptibility or resistance to subsequent microfilarial production and a parasite strategy to use specific immune responses to its own benefit.

Synergism of gamma interferon and interleukin-5 in the control of murine filariasis.

There has been a prevailing perception that Th1 and Th2 immune responses induce antagonistic immune effector mechanisms during an infection. We investigated the role of the Th1 cytokine gamma interferon (IFN-gamma) and the Th2 cytokine interleukin-5 (IL-5) in murine filariasis infections with the rodent filarial nematode Litomosoides sigmodontis with regard to immune responses to the parasite. Earlier data showed an important role for IL-5 and IFN-gamma in effective immune responses to filarial infection. Therefore, in this study it was asked whether IL-5 and IFN-gamma act synergistically or antagonistically. Indeed, IL-5 as well as IFN-gamma knockout (KO) mice show a higher worm load than the wild-type controls. IFN-gamma/IL-5 double-KO mice had a significantly higher worm load than any of the single-KO mice, suggesting a synergism between IFN-gamma and IL-5 in controlling worm infection. Neutrophils are known to play an important role for the containment and encapsulation process of the worms. In infected IFN-gamma KO, IL-5 KO, and IFN-gamma/IL-5 double-KO mice, neutrophils were significantly reduced in chemotactic activity levels compared to controls. In addition, the level of phagocytosis activity of neutrophils from IFN-gamma/IL-5 double-KO mice was further decreased in comparison to that of the single-KO mice. Levels of tumor necrosis factor alpha, which is an important factor for neutrophil activation, were found to be reduced in macrophages from KO mice. In conclusion, these results argue for immune effector mechanisms in murine filarial infection that are dependent on both IFN-gamma and IL-5. Synergistic effects of the two cytokines may be mediated, at least in part, by neutrophils for the control of adult worms.

Removal of Wolbachia from Brugia pahangi is closely linked to worm death and fecundity but does not result in altered lymphatic lesion formation in Mongolian gerbils (Meriones unguiculatus).

Approximately 30 years ago, researchers reported intracellular bacteria in filarial nematodes. These bacteria are relatives of the arthropod symbiont Wolbachia and occur in many filarial nematodes, including Brugia pahangi and Brugia malayi. Wolbachia bacteria have been implicated in a variety of roles, including filaria development and fecundity and the pathogenesis of lymphatic lesions associated with filarial infections. However, the role of the bacteria in worm biology or filarial disease is still not clear. The present experiments support previous data showing that tetracycline eliminates or reduces Wolbachia bacteria in B. pahangi in vivo. The elimination of Wolbachia was closely linked to a reduction in female fecundity and the viability of both sexes, suggesting that the killing of Wolbachia is detrimental to B. pahangi. The gerbils treated with tetracycline showed reduced levels of interleukin-4 (IL-4) and IL-5 mRNA in renal lymph nodes and spleens compared with the levels in B. pahangi-infected gerbils not treated with tetracycline. However, similar findings were noted in B. pahangi-infected gerbils treated with ivermectin, suggesting that the loss of circulating microfilariae, not the reduction of Wolbachia bacteria, was associated with the altered cytokine profile. Despite the change in T-cell cytokines, there was no difference in the sizes of renal lymph nodes isolated from gerbils in each treatment group. Furthermore, the numbers, sizes, or cellular compositions of granulomas examined in the lymphatics or renal lymph nodes did not differ with treatment. These data suggest that Wolbachia may not play a primary role in the formation of lymphatic lesions in gerbils chronically infected with B. pahangi.

Community perception of Malayan filariasis in the rural areas of Cherthala Taluk of Kerala State, south India.

Lymphatic filariasis, one of the major public health problems can be controlled with the active participation of the community. The human factors involved in the disease transmission are important. The knowledge on the community perception and practice is essential to develop community oriented control programmes. A descriptive study was conducted in the filariasis endemic area of Cherthala, Kerala State, India, to identify the level of people's perception on Malayan filariasis. Two methods namely, interviews and uncontrolled observation were used in the study. A total of 450 respondents (150 microfilaria carriers, 150 chronic patients and 150 normals) were interviewed. The study results showed that majority of the respondents (86.7%) were aware that the disease was caused by a parasite and 93.6% had awareness on transmission of the disease through mosquito bite. The knowledge on the preventive measures against filariasis was also high (78.2%) among the sampled respondents. The strategy for community mobilization in filariasis control programme is discussed in view of high awareness.

Implementation of revised strategy of filaria control-baseline clinico-parasitological survey.

A clinico-epidemiological study of filariasis was carried out in Varanasi District in October and November, 1997 to generate baseline data for assessing the impact of Mass Drug Administration (MDA) in the district. Disease rate was found to be 6.6% (9.9% in males and 3.0% in females) and microfilaria rate was 5.3% (5.2% in males and 5.5% in females). Mean microfilaria density was found to be 9.86 per 20 Cu.mm blood. Genital manifestations (77.5%) outnumbered all other forms of clinical manifestations. Vector infectivity rate was found to be 0.93%.

Rural bancroftian filariasis in north-western Cameroon: parasitological and clinical studies.

A cross-sectional epidemiological, parasitological and clinical survey of bancroftian filarieasis was conducted in the rural north-western Republic of Cameroon. Of the 1020 respondents (622 males and 398 females) randomly drawn from 4 ethnically homogeneous communities, 148 were microfilaraemic giving an overall prevalence of 14.5%. Association between the ages of individuals and the prevalence of microfilaria (mf) in peripheral circulation was statistically significant (chi 2(6) = 12.59, P < 0.05). More males (7.8%) than females (6.7%) of all ages exhibited mf and was significant statistically (chi 2 = 0.98, P < 0.01). Community-specific prevalence of mf ranged from 11.9% in Bambui to 17.0% in Bambeli. At the community level the overall geometric mean intensity (GMI) of infection was 192 mf per 10 ml of blood (range 165 mf p ml to 248 mf p ml). Overt clinical manifestations of chyluria, elephantiasis and hydrocele were detected among the mf-positive respondents. Thirty one cases (20.9%) involving 15 (18.6%) males and 16 (23.15%) females exhibited chyluria which was absent in children aged 1 < or = 10 years but appeared to be associated with advancing age. Elephantiasis especially of lower extremities and breast was observed in 8 (10.0%) males and 15 (22.0%) females. Highest cases of elephantiasis were recorded for female adults aged 41-60 years (34.6%) of total cases. Hydrocele affected 20.0% of mf-positive males ages > or = 11 years with cases increasing with advancing age. A positive association seems to exist between hydrocele prevalence and the prevalence of microfilaraemia. A total of 1440 female mosquitoes belonging to 3 species were dissected for the presence of microfilariae. Anopheles gambiae complex s.l. was the dominant species and the only one found to be naturally infected with mf. The apparently low mf. intensity in the population, pattern of microfilaraemia, distribution of clinical syndromes and vector species are discussed.

Apoptosis induced by filarial parasitic sheath protein in HEp 2 cell lines blocked by ectopic expression of bcl 2.

Chronic filarial patients exhibit an occult manifestation, Tropical Pulmonary Eosinophilia, (TPE), caused by an exaggerated immune response to shed and circulating filarial antigens, leading to extensive lung damage. We have attempted to examine the disease in vitro using the human epithelial cell line, HEp2. Filarial sheath proteins induce apoptosis in HEp2 cells characterized by chromatin condensation, internucleosomal DNA cleavage, positive staining for TUNEL assay and shows a sub-G1 peak on FACS analysis. In order to understand subcellular events and to analyse the protective role of bcl2, we engineered HEp2 to overexpress Bcl2 protein. HEp2 bcl2 cells do not undergo apoptosis on exposure to filarial sheath protein, indicating that filarial protein-induced apoptosis in epithelial cells proceeds via a pathway, inhibitable by overexpression of bcl 2.

Uptake and development of Wuchereria bancrofti in Culex pipiens L. and Aedes caspius pallas.

Studies were conducted to compare early phenomena associated with W. bancrofti infection and further development in the filaria vector Culex pipiens and the refractory mosquito Aedes caspius. Ingestion rates evaluated immediately after simultaneous feeding on an infected human were 69.1% for 43 Cx. pipiens and 35.7% for 28 Ae. caspius. The observed number of mf ingested by either mosquito did not vary significantly (2.7 +/- 1.4, and 2.3 +/- 0.9, respectively) and, based on the size of the blood meal ingested (2.8 and 2.3 microliters respectively), a two-fold mf concentration factor was recorded for both species. Blood ingested by Cx. pipiens (N = 16) and Ae. caspius (N = 10) clotted within 120 and 90 min post-feeding respectively. The time difference observed, however, did not affect significantly the rates of migration into the hemocele (56 and 67% respectively). Comparison of initial infection rates with those obtained after the extrinsic incubation period of the parasite was completed, indicated that the proportion of infected Cx. pipiens was reduced by 3.9% and that of Ae. caspius by 30.0%. Furthermore, the observed infectivity ratio of 265 Cx. pipiens that had an infective blood meal was 0.74 and only 0.009 for 70 Ae. caspius. It is concluded that refractoriness of Ae. caspius to W. bancrofti is expressed through the feeding mechanism itself, by severely limiting the mf ingestion rate, and through physiological processes that inhibited the development of ingested worms.

Brugia pahangi-induced contractility of bovine mesenteric lymphatics studied in vitro: a role for filarial factors in the development of lymphedema?

Products generated by filarial nematodes depress vascular reactivity by mechanisms involving endothelial cells. We hypothesized that comparable filarial-induced alterations might occur in lymph vessels. Experiments were designed to test the hypothesis that spontaneous contractions of bovine mesenteric lymphatics studied in vitro are altered by the filarial parasite Brugia pahangi. Rings of bovine mesenteric lymphatics were suspended in tissue baths and spontaneous contractions were evaluated for rate, rhythm, and amplitude. Rings that met inclusion criteria (rate > 1.8/min, regular rhythm, and an amplitude > 500 mg) were randomly exposed to B. pahangi or used as controls. Parasites were added to the bath at time zero. Changes in rate, rhythm, and magnitude of spontaneous contractions were evaluated every 10 min. Comparisons were made within control or Brugia-infected groups over time and between groups (B. pahangi versus controls). The presence of B. pahangi significantly depressed the frequency of spontaneous contractions when compared with controls. Control rings were stable over time, without changes in rate, rhythm, or amplitude. However, B. pahangi alter both the rate and rhythm of spontaneous contractions. Since spontaneous contractile activity is likely to be important in the propulsion of lymph, alterations of contractile activity could result in lymphedema. Thus, filarial factors may be responsible, in part, for altered lymphatic function seen in lymphedema. Pharmacologic intervention aimed toward influencing host-parasite metabolic interactions may, in this complicated scenario, prove useful.

Immunology of human helminth infection.

Parasitic helminths cause enormous morbidity among humans especially in developing countries. These large extracellular organisms have complex life cycles frequently involving an arthropod vector. Helminth parasites can be tissue dwelling or intestinal but all induce a dramatic expansion of the Th2 lymphocyte subset. It remains unclear whether these Th2-derived responses, including IgE, eosinophilia and mastocytosis are important in the protective immune response to the parasite, or are responsible for immune-mediated pathology, or both. Interestingly, despite high levels of IgE and other features of Th2 cell activation, allergic responses are rarely observed in infected individuals. Helminths can survive for years in the infected host, and have evolved elaborate immune evasion strategies to establish these long-lived infections including the induction of tolerance to parasite antigens. This review discusses the dynamics of infection with helminth parasites with specific emphasis on Th2 subset activation. The current knowledge of immune effector mechanisms, immunopathology and hopes for vaccine development are also discussed.

The host-parasite relationships in pyridoxine (vitamin B6) deficient cotton rats infected with Litomosoides carinii (Nematoda: Filaroidea).

This paper demonstrates that the establishment and growth of the filarial nematode parasite, Litomosoides carinii, is reduced in pyridoxine-deficient cotton rats. Young cotton rats were assigned to one of three dietary: vitamin B6-deficient cotton rats (B6-AL) were fed a pyridoxine-free diet ad libitum; pair-fed controls (B6 + PF) were fed the same amount of pyridoxine-free diet as animals in the deficient group and given daily oral supplements of 100 micrograms pyridoxine; and pyridoxine-sufficient controls (B6 + AL) were fed the pyridoxine-free diet ad libitum and supplemented daily with 100 micrograms pyridoxine. Half of each group was infected with 50 L3 of L. carinii by subcutaneous injection 8 weeks after the start of the experimental feeding period. B6-deficient cotton rats ate less (P < 0.001) and gained less weight (P < 0.001) than B6-supplemented controls. The levels of microfilaraemia in deficient animals, measured weekly throughout the experiment by taking blood smears, was significantly lower than in supplemented animals (P < 0.001). The deficient rats became latent for L. carinii at 20 weeks post-infection, whereas there was patent microfilaraemia in rats in the other dietary groups until the end of the experiment. Smaller (P < 0.001) and fewer (P < 0.05) adult worms were recovered from the pleural and abdominal cavities of deficient animals than from either pair-fed or sufficient controls at autopsy 28 week post-infection.