Humoral and cellular immune responses to Onchocerca volvulus infection in humans

Onchocerciasis is one of the major filarial diseases affecting humans and a leading cause of blindness. Control of the disease by chemotherapy and by elimination of the vector is not feasible in most areas of endemicity. The host immune response is thought to play a major role in the pathogenesis of complications. However, there is no clear evidence of protective immunity to reinfection in individuals who continue to be exposed to infective larvae. Antigens of Onchocerca volvulus are complex and show extensive cross-reactivity with other filarial parasites of humans and animals. Infection in humans results in the production of precipitating and reaginic antibodies to the parasite and in increases in levels of immunoglobulins that have no apparent specificity for parasitic antigens. Chronic antigenic stimulation in the presence of an antibody response leads to increased levels of circulating immune complexes. Cell-mediated immunity to parasite-derived antigens, as measured by migration inhibition, lymphocyte blastogenesis, and delayed skin-test reactivity, is decreased during infection. In addition, there is a decrease in delayed skin-test reactivity and in lymphocyte blastogenesis in response to unrelated antigens.     

Transmission intensity and the patterns of Onchocerca volvulus infection in human communities

We focus on possible constraints upon Onchocerca volvulus establishment in humans in relation to exposure rates to infective larvae (L3) as measured by the annual transmission potential (ATP). We use mathematical and statistical modeling of pre-control west African (savanna), Mexican, and Guatemalan data to explore two hypotheses relating human infection to transmission intensity: microfilarial (mf) loads either saturate with increasing ATP or become (asymptotically) proportional to the ATP. The estimated proportion of L3 developing into adult worms ranged from 7% to 0.3% (low and high intensity areas, respectively). Relationships between mf prevalence and both mf and transmission intensity were nonlinear and statistically similar between west Africa (Simulium damnosum s.l.) and Meso America (S. ochraceum s.l.). This similarity extended to the relationship between mf intensity and ATP. The critical biting rates for onchocerciasis introduction and persistence (which depended on vector competence and host preference), were approximately 10-fold higher in settings where onchocerciasis is transmitted by S. ochraceum than in those where the vector is S. damnosum. A role for focal vector control in Mexico and Guatemala, in addition to nodulectomy and ivermectin, is suggested.     

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.     

HLA-D alleles associated with generalized disease, localized disease, and putative immunity in Onchocerca volvulus infection.

Human infections with the tissue nematode Onchocerca volvulus result in a variety of clinical conditions that possibly include protective immunity. In a West African area hyperendemic for human onchocerciasis, 120 residents were classified according to clinical and laboratory findings as presenting with generalized onchocerciasis, localized onchocerciasis, or as being putatively immune. The three groups differed in the distribution of HLA-D variants as determined by DNA typing. The most pronounced differences were found among alleles of the DQ loci. The haplotype DQA1*0501-DQB1*0301 was significantly more frequent among putatively immune individuals than among patients with generalized or localized disease. Conversely, DQA1*0101-DQB1*0501 and, independently, the allele DQB1*0201 were more frequent in generalized disease than in localized disease or putative immunity. In these correlations, the frequencies of allelic variants were in localized disease intermediate to those of the two other groups. The only distinct association found with localized disease was that of the DP allele DPB1*0402. The findings indicate that HLA-D variants influence the course of O. volvulus infection and help to define a state that may reflect protective immunity.     

Specific cellular immune response in patients with Helicobacter pylori infection

The leukocyte migration inhibition test was performed in 39 patients with Helicobacter pylori infection and in 38 patients without such infection. The culture of Helicobacter pylori was used as antigen. A highly significant inhibitory effect on leukocyte migration was found in patients with Helicobacter pylori infection. The results can be taken as proof of a systemic immune response to helicobacters at the cellular level in patients with Helicobacter pylori infection.     

Characterization of human immune responses to the cytosolic superoxide dismutase and glutathione S-transferase from Onchocerca volvulus

In onchocerciasis patients and in O. volvulus -exposed individuals without signs of onchocerciasis, T- and B-cell responses to two recombinantly expressed O. volvulus enzymes were analysed and compared to responses to total protein extract of adult parasites. The cytosolic enzymes Cu/Zn superoxide dismutase 1 (OvSOD1) and glutathione S-transferase 2 (OvGST2) represent 2 detoxifying molecules which may play an important role in parasite defense against host-induced oxidative stress. The T-cell response to the two recombinant proteins was analysed by investigating the cytokine responses of peripheral blood mononuclear cells. Induction of IL-5 at the mRNA level and IL-5 and IL-10 at the protein level was demonstrated in patients with the generalized form of onchocerciasis and endemic normals without clinical manifestations. IFN-γ was not found to be induced by either antigen. This pattern of lymphokine expression is indicative of a Th2-type response. Compared to patients with the generalized form, a higher level of cytokine induction was observed in the group of endemic normals. Low but significant IgG levels were observed against OvSOD1 in patients with onchocerciasis; higher antibody levels were found against OvGST2 in patients and endemic normals. The highest IgG levels were detected against the crude O. volvulus extract. These results indicate that the two recombinant O. volvulus proteins induce moderate T and B cell responses.     

Heat-shock response is associated with enhanced postischemic ventricular recovery

In cells, hyperthermia induces synthesis of heat-shock proteins and the acquisition of thermotolerance. Thermotolerant cells are resistant to subsequent oxidative stress. In this study, heat-shocked hearts were examined for evidence of protection during ischemia and reperfusion. Rats were exposed to 15 minutes of 42 degrees C hyperthermia. Twenty-four hours later their hearts were isolated and perfused and the contractility examined during and after ischemic perfusion. No protection was observed during ischemic perfusion. However, upon reperfusion heat-shocked hearts had recovery of contractility within 5 minutes of reperfusion, while control hearts showed no contractility at this time. Throughout 30 minutes of reperfusion heat-shocked hearts had significantly improved recovery of contractile force, rate of contraction and rate of relaxation. Creatine kinase release, associated with reperfusion injury, was significantly reduced from a high of 386.8 +/- 78.9 mU/min/g heart wt for controls to 123.7 +/- 82.9 mU/min/g heart wt for heat-shocked hearts at 5 minutes of reperfusion. Following 30 minutes of reperfusion, ultrastructural examination revealed less damage of mitochondrial membranes in the heat-shocked hearts. Further biochemical investigations revealed that the antioxidative enzyme, catalase, was significantly increased to 137 +/- 12.7 U/mg protein in the heat-shocked hearts while the control value was 64.8 +/- 8.3 U/mg protein. Hyperthermic treatment, which induces the heat-shock response, may be therapeutic for salvaging ischemic myocardium during reperfusion, through a mechanism involving increased levels of myocardial catalase.     

Specific serodiagnosis with adult Onchocerca volvulus antigen in an enzyme-linked immunosorbent assay

The cross-reactivity of the blood from onchocerciasis, loiasis, and dipetalonemiasis was tested by a micro-ELISA technique, utilizing adult Onchocerca volvulus antigen and blood samples taken on filter paper. The average ELISA values (OD at 500 nm) were as follows: 0.58 in persons with O. volvulus microfilariae (n = 81), 0.49 in microfilariae-negatives from the same endemic area (n = 39), 0.15 in dipetalonemiasis (n = 27), and 0.25 in loiasis (n = 12), while those of 65 Dipetalonema perstans-negative people were markedly low (average 0.14) and that of 22 Loa loa-negatives, 0.22, respectively. This ELISA could successfully differentiate onchocerciasis from dipetalonemiasis and loiasis.     

The effect of multiple ivermectin treatments on infection of Simulium ochraceum with Onchocerca volvulus

Ivermectin, a broad spectrum antiparasitic agent, interrupted the uptake of Onchocerca volvulus microfilariae by Simulium ochraceum from a group of human volunteers given multiple oral treatments of 200 micrograms/kg body weight. Two treatments, given at 7 month intervals, resulted in almost complete suppression of developing or infective larvae in the vector population for a 6 month period. The overall decline following 2 treatments was an order of magnitude lower than the pretreatment level. Ivermectin administration, in addition to the beneficial clinical effects, also could be useful for the control of human onchocerciasis as an independent measure or in conjunction with vector control.     

Autoimmune-related pancreatitis is associated with autoantibodies and a Th1/Th2-type cellular immune response

BACKGROUND & AIMS: Although autoimmunity may be involved in some cases of pancreatitis, the mechanism is still unknown. To clarify this, we studied serum autoantibodies, subsets of lymphocytes, and the Th1/Th2 balance of cellular immune responses in patients with autoimmune-related pancreatitis (AIP). METHODS: Seventeen patients with AIP (8 men and 9 women; age, 53.2 +/- 13.0 years) were studied. Autoantibodies including antilactoferrin (ALF) or carbonic anhydrase II antibody (ACA-II) were examined using the enzyme-linked immunosorbent assay (ELISA) or the indirect fluorescein antibody method. Intracellular cytokines (interferon gamma and interleukin 4) and subtypes of peripheral blood lymphocytes were examined by flow cytometry and ELISA. RESULTS: More than one autoantibody was observed in all 17 patients. Serum antinuclear antibody was detected in 13 of 17 patients, ALF antibody in 13, ACA-II antibody in 10, rheumatoid factor in 5, and anti-smooth muscle antibody in 3, but antimitochondrial antibody in none. The serum levels of ACA-II and LF antibody were not correlated. HLA-DR(+)CD8(+) and HLA-DR(+)CD4(+) cells were significantly increased in peripheral blood (P < 0.05). CD4(+) cells producing interferon gamma and the secreted levels were significantly increased compared with those in controls (P < 0.05), but interleukin 4 was not increased. CONCLUSIONs: An autoimmune mechanism against CA-II or LF, and Th1-type immune response, may be involved in AIP.     

Development and characteristics of the cellular immune response to infection with varicella-zoster virus

Techniques for assay of in vitro lymphocyte transformation (LTF) were used with varicella-zoster virus (VZV) as the antigen to study the temporal characteristics of the VZV-specific cellular immune response in children with varicella and in normal subjects with a history of the illness. The LTF response in children with only vesicular eruptions was prompt, and individual peak activity was detected within one to two weeks after the onset of illness, followed by a gradual decrease of the activity to lower levels. Patients with a complication of meningoencephalitis showed a marked delay in the development of peak activity. No consistent defference in the development of complement-fixing antibody to VZV was observed in these patients with different clinical manifestations. The LTF response of normal subjects with remote clinical evidence of varicella was characterized by occasional high activity, a finding that suggests reinfection with VZV. These observations provide additional evidence that the specific cellular immune response is heavily involved in the pathogenesis of VZV infection.     

Expression of an Onchocerca volvulus Ov33 homolog in Dirofilaria immitis: potential in immunodiagnosis of heartworm infection

In this study, the expression of an Onchocerca volvulus Ov33 homolog was demonstrated in Dirofilaria immitis. Rabbit antiserum raised against a recombinant fusion protein of O. volvulus, MBP/OvD 5B (Ov33), was found to react with a 31–33 kDa glycoprotein (DiT33) of adult worms of D. immitis. An antibody response to MBP/OvD 5B was observed in dogs, as early as 11 weeks post infection with infective larvae of D. immitis, and in dogs with occult infection. Cats both experimentally and naturally infected with D. immitis also reacted strongly with the recombinant antigen. In contrast, sera from dogs receiving chemically-abbreviated infection or from animals harbouring a variety of other helminths failed to react. These data suggest that antibody responses generated by DiT33 may have potential in immunodiagnosis of heartworm infection in cats and dogs.     

T cell responses in coinfection with Onchocerca volvulus and the human immunodeficiency virus Type 1

Onchocerca volvulus and the human immunodeficiency virus (HIV) are two immunocompromising infectious agents of major public health concern in Uganda. To examine the effect of coinfection with O. volvulus and HIV on cellular immune responses, lymphocyte proliferative responses and cytokine production of peripheral blood mononuclear cells (PBMC) from persons infected with O. volvulus with and without HIV type 1 infection were compared. Proliferation of PBMC to PHA and tuberculin (PPD) in coinfection was less ( P  = 0.08, P  < 0.01) than in O. volvulus infection . O. volvulus extract stimulated lymphocyte proliferation in microfilaria-negative and HIV-negative O. volvulus infection while only an inconspicuous response was observed in microfilaria-negative coinfection. After stimulation of PBMC with PPD, the production of interferon-γ (IFN-γ), interleukin (IL)-4 and IL-5—demonstrated in O. volvulus infection—were reduced in coinfection with HIV ( P  < 0.01). While both groups failed to produce IFN-γ in response to O. volvulus extract, only O. volvulus infected persons generated pronounced IL-5 and low IL-4 levels (0.01 > P  = 0.02). The cellular immune responses in coinfection suggested an HIV-related lack of specific reactivity to O. volvulus antigen and impairment of IL-4 and IL-5 production in addition to the lack of IFN-γ response on antigenic stimulation .     

Functional characterization and immune recognition of the extracellular superoxide dismutase from the human pathogenic parasite Onchocerca volvulus (OvEC-SOD)

Onchocerca volvulus is a human pathogenic filarial nematode causing chronic onchocerciasis, a disease characterized by chronic skin and eye lesions. Despite attempts to control this infection from many perspectives, it still remains a threat to public health because of adverse effects of available drugs and recent reports of drug resistance. Under control of an intact immune system, O. volvulus survives for a long time in the host by employing a variety of strategies including the utility of antioxidant enzymes. In the present study, we focus on the extracellular superoxide dismutase from O. volvulus (OvEC-SOD) found in the excretory/secretory products of adult worms. Contrary to previous studies, the OvEC-SOD was found to have a 19 amino acid long signal peptide that is cleaved off during the process of maturation. To validate this result, we designed a novel method based on Caenorhabditis elegans cup5(ar465) mutants to specifically evaluate signal peptide-mediated secretion of nematodal proteins. Following purification, the recombinant OvEC-SOD was active as a dimer. Site-directed mutagenesis of the three cysteines present in the OvEC-SOD shows that enzyme activity is markedly reduced in the Cys-192 mutant. A homology model of the OvEC-SOD underlines the importance of Cys-192 for the stabilization of the adjacent active site channel. The generation of a humoral immune response to secretory OvEC-SOD was indicated by demonstrating IgG reactivity in sera from patients infected with O. volvulus while the cross-reactivity of IgG in plasma samples from cows, infected with the most closely related parasite Onchocerca ochengi, occurred only marginally. High IgG1 and IgM titres were recorded in sera from mice infected with the filaria Litomosoides sigmodontis, however, low or no cellular proliferative responses were observed. Thus, the present data suggest that secretory OvEC-SOD is a target of the humoral immune response in human onchocerciasis and induced strongest IgG responses in hyperreactive onchocerciasis. Furthermore, humoral response during murine infection induced SOD-specific IgG that cross-reacted with OvEC-SOD.     

Acute dengue virus 2 infection in Gabonese patients is associated with an early innate immune response,including strong interferon alpha production

Background  

Dengue is now a leading cause of morbidity and mortality throughout the tropics. We conducted the first ex vivo study of dengue fever (DF) in African patients infected during the first Gabonese dengue virus 2 (DENV-2) outbreak in 2007, in order to investigate cytokine production, including the antiviral cytokine IFN-α, reported to be a potent inhibitor of DENV replication in vitro.     

Osteoporosis in patients with rheumatoid arthritis is associated with serum immune regulatory cellular factors

Clinical Rheumatology - Osteoporosis (OP) is a comorbidity of rheumatoid arthritis (RA) that largely causes disability. This study discussed the expression patterns of serum immunoregulatory...     

Early immune response in healthy and immunocompromised subjects with primary varicella-zoster virus infection

Events in pathogenesis and immunity during primary varicella-zoster virus (VZV) infection were examined in 64 healthy subjects and 21 immunocompromised patients. Activation of the interferon system and activation of circulating T lymphocytes were early immune responses that occurred during the incubation period in some healthy subjects. Elevated levels of 2-5A synthetase in peripheral blood mononuclear cells and detection of serum alpha interferon (IFN-alpha) and gamma interferon (IFN-gamma) were present in the majority of healthy subjects who had acute primary VZV infection. Expression of HLA-DR antigen occurred on circulating T lymphocytes from subjects with acute VZV infection. The early production of VZV-specific IgG or IgM antibodies did not correlate with the severity of the clinical infection, but the detection of T lymphocyte proliferation to VZV antigen within three days after the appearance of the varicella exanthem was associated with milder illness. The mean VZV-specific lymphocyte transformation for subjects with less than 100 lesions/m2 was 7.5 +/- 10.43 SD compared with 1.4 +/- 1.85 SD for those with greater than 400 lesions/m2 (P less than .05). Only one (7.7%) of 13 immunocompromised patients had early VZV-specific lymphocyte transformation compared with 19 (42%) of 45 healthy subjects (P less than .05). The rapid host response to primary VZV infection was associated with rapid termination of viremia in healthy subjects; VZV was isolated from only 11% of peripheral blood mononuclear cell samples cultured within 48 hr after the appearance of the exanthem.