IgG avidity ELISA test for diagnosis of acute toxoplasmosis in humans

Serum samples, 100 in the total number, were collected from different laboratories in Tehran, Iran and tested for anti-Toxoplasma specific IgG and IgM antibodies using indirect immunofluorescent antibody test (IFAT). Using the IgG (chronic) and IgM (acute) positive samples, the IgG avidity test was performed by ELISA in duplicate rows of 96-well microtiter plates. One row was washed with 6 M urea and the other with PBS (pH 7.2), then the avidity index (AI) was calculated. Sixteen out of 18 (88.9%) sera with acute toxoplasmosis showed low avidity levels (AI ≤ 50), and 76 out of 82 (92.7%) sera in chronic phase of infection showed high avidity index (AI>60). Six sera had borderline ranges of AI. The results showed that the IgG avidity test by ELISA could distinguish the acute and chronic stages of toxoplasmosis in humans.     

Performance of the immunoglobulin G avidity and enzyme immunoassay IgG/IgM screening tests for differentiation of the clinical spectrum of toxoplasmosis

Toxoplasmosis has been well known as an important human infection to consider especially in pregnant women. Although many serologic methods are available, the diagnosis of toxoplasmosis can be extremely difficult. The presence of increased levels of Toxoplasma-specific IgG antibodies indicates an infection, but it does not differentiate between a recent and past infection. The purpose of our study was to compare the performance of the ELISA T. gondii IgG/IgM test, a widely used enzyme-linked immunosorbent assay, to the ELISA IgG avidity method. One hundred and four serum samples (from 38 males and 66 females) were tested and evaluated from symptomatic patients (chorioretinitis, lymphadenopathy), and from women in their first trimester of pregnancy who were suspected of having toxoplasmosis. The high IgG avidity and ELISA IgG antibody levels were in agreement for 51 of the specimens (49.0%). Thirty-eight discrepant (borderline) results from the IgG avidity method were positive for IgM (3 specimens) and IgG (37 specimens). Interestingly, out of the eight serum samples that were positive for both IgG and IgM antibodies, two samples were low IgG avidity, and three samples were borderline. There was no statistically significant relation observed between the results of the IgG avidity method and the ELISA IgG test, and the IgG avidity method and ELISA IgM test (chi2 = 1.987; p = 0.370 and chi2 = 2.152; p = 0.341, respectively). The IgG avidity method was considered easy to perform and an acceptable approach for the differentiation of discrepant results (recent/chronic) and for the current detection of T. gondii antibodies. We concluded that the determination of IgG avidity is a helpful tool for the diagnosis of the ocular form of toxoplasmosis and it is a safe method for screening this disease in the first trimester of pregnancy.     

Detection of IgG binding to Schistosoma mansoni recombinant protein RP26 is a sensitive and specific method for acute schistosomiasis diagnosis

We recently described the first recombinant Schistosoma mansoni protein RP26, which was capable of acute infection diagnosis. The aim of the present work was to further characterize the RP26 diagnostic properties in immunoblot and enzyme-linked immunosorbent (ELISA) assays. Testing sera from uninfected donors and sera from patients with acute or chronic Schistosoma infection by Western blot immunoassay revealed 100% specificity and 100% sensitivity for acute infection identification. Sera from uninfected, acute, and chronic schistosomiasis were also probed for IgG, IgG4, IgA, and IgM reactivity to RP26 plus soluble egg antigens (SEA) in ELISA. The mean IgG reactivity to RP26 by sera from acute schistosomiasis patients was significantly higher than the chronic ones. The IgG4, IgA, and IgM reactivities to RP26 were low and similar in both infected groups. The mean IgA and IgM reactivities to SEA were significantly higher in the group of acute compared to chronic group, whereas mean IgG4 reactivity was higher in chronic group. To estimate the specificity of Schistosoma infection diagnosis sera from patients infected with other different parasites were tested to detect IgG reactivity to RP26 and IgA and IgM reactivity to SEA. For IgA against SEA detection, 72% of sera were positive and 48% of sera were positive for IgM detection. Based on these results we can suggest that detection of sera IgG binding to RP26 is a sensitive and specific method for acute schistosomiasis diagnosis. Therefore, RP26 is a candidate for immunodiagnostic kit development.     

Enzyme-linked immunosorbent assay (ELISA) for IgM, IgG and IgA class antibodies against Candida albicans antigens: development and comparison with other methods

An extract of Candida albicans was used as an antigen on microtitre plates in the enzyme-linked immunosorbent assay (ELISA) to measure IgM, IgG and IgA class antibodies in the sera of hospitalized patients. It was found that of these patient sera that reacted positively in Ouchterlony immunodiffusion (ID) when undiluted, 58% were also positive in the ELISA against the same antigen preparation. However, all the sera with an ID titre of 1:2 or higher were ELISA-positive, demonstrating especially IgG and IgA. Of the sera positive by counterimmunoelectrophoresis against somatic and metabolic antigens of C. albicans, 86% were positive by ELISA. Reactions in precipitin-negative sera, if they occurred, usually demonstrated IgM or IgA. The sera with high passive haemagglutination or indirect immunofluorescence titres against surface antigens of C. albicans were positive in the IgG and IgA assays, while approximately one third were positive in the IgM assay.     

The role of IgG avidity in diagnosis of cytomegalovirus infection in newborns and infants

To evaluate the value of IgG avidity in diagnosis of congenital cytomegalovirus (CMV) infection in newborns and infants we collected serum samples from 40 infants under 12 months of age with suspected congenital CMV infection. Sera were tested for IgM, IgG and IgG avidity. For 25 of them, virus isolation and/or polymerase chain reaction (PCR) on urine specimens were performed. Thirteen (32.5%) patients showed the presence of CMV IgM antibodies, 3 (7.5%) had equivocal IgM result, and 24 (60.0%) patients had IgG antibodies only. Using IgG avidity, CMV infection (low avidity index-AI) was documented in 61.5% IgM positive and 54.2% IgM negative patients. Eight of nine (88.8%) IgM positive patients were positive either on virus isolation or PCR. In IgM negative patients, 46.6% urine cultures were positive for CMV and 66.6% were PCR positive. According to age, IgG avidity demonstrated acute/recent primary CMV infection in 58.8% patients younger than three months compared with 91.7% and 81.8% in 3-6 and 6-12 months old babies, respectively. In conclusion, IgG avidity is useful in diagnosis of CMV infection either in IgM positive or IgM negative children older than 3 months of age. In infants less than 3 months, transplacentally derived maternal IgG antibodies of high avidity influence on the IgG avidity result. In these children, CMV infection should be confirmed by direct virologic methods such as virus isolation or PCR.     

Evaluation of the indirect and IgM‐capture anti‐human cytomegalovirus IgM ELISA methods as confirmed by cytomegalovirus IgG avidity

Primary cytomegalovirus (CMV) infection during pregnancy often results in congenital CMV infection with severe clinical complications. IgM antibodies are one of the indices of primary infection. The IgG avidity index (AI) is also known to remain low for 3 months after primary infection. Here, we evaluated and compared the performance of CMV IgM and IgG avidity assays. Because sensitivity and specificity reportedly differ between CMV IgM kits, CMV IgM detection was compared between the two commercially available ELISA kits that are most commonly used in Japan. Sera for CMV IgM were first screened using a traditional indirect ELISA kit. Selected samples were then tested for CMV IgM and CMV AI using a CMV IgM‐capture ELISA kit and a CMV IgG avidity assay, respectively. The rate of concordance between the IgM kits was 89% (42/47), indicating the absence of any significant difference. Most of the CMV IgM‐positive plasma samples showed high CMV IgG AI; however, 18 commercially available plasma samples with low CMV IgG AI were all CMV IgM‐positive. One plausible explanation for this discrepancy is that the duration of low IgG AI is shorter than that of IgM positivity. Alternatively, CMV IgM tests may generate pseudo‐positive readouts in cases of congenital infection. Nevertheless, our study confirms that CMV IgG AI can be a reliable indicator of CMV primary infection.     

IgG Avidity Antibodies against Toxoplasma gondii in High Risk Females of Reproductive Age Group in India

Toxoplasma gondii is an obligate intracellular protozoan that is distributed worldwide. Recently, several tests for avidity of Toxoplasma IgG antibodies have been introduced to help discriminate between recently acquired and distant infections. The study was conducted in Jawaharlal Nehru Medical College and Hospital, India from February 2011 to September 2012. Serum specimens were subjected to Toxoplasma IgM ELISA and IgG avidity ELISA test. Out of 48 patients with abortions, 17 (35.4%) were positive for IgM ELISA, and 8 (16.6%) had low IgG avidity antibodies. Out of 48 patients with other obstetric problems, 23 (47.9%) were positive for IgM ELISA, and 17 (35.4%) had low IgG avidity antibodies. Combining both groups on avidity test, only 25 of 40 (62.5%) IgM-positive women had low-avidity IgG antibodies suggesting a recent T. gondii infection in these women. More importantly, 15 (37.5%) of the IgM-positive women had high-avidity antibodies suggesting that the infection was acquired before gestation The relation of IgM seropositivity with the following risk factors was not found to be statistically significant; contact with cats (0.13), non-vegetarian food habits (0.05), and low socio-economic status (0.49). While, for IgG avidity ELISA, only contact with cats (0.01) was significantly associated with seropositivity. All other risk factors have P-values of >0.05 (not significant). IgG avidity test when used in combination with IgM test was a valuable assay for diagnosis of ongoing or recently acquired T. gondii infection in India.     

Identification of potential serodiagnostic and subunit vaccine antigens by antibody profiling of toxoplasmosis cases in Turkey

Toxoplasmosis, caused by infection of the protozoan parasite Toxoplasma gondii, is associated with mild disease in healthy individuals, whereas individuals with depressed immunity may develop encephalitis, neurologic disorders, and other organ diseases. Women who develop acute toxoplasmosis during pregnancy are at risk of transmitting the infection to the fetus, which may lead to fetal damage. A diagnosis is usually confirmed by measuring IgG, or IgM where it is important to determine the onset of infection. A negative IgM result essentially excludes acute infection, whereas a positive IgM test is largely uninterpretable because IgM can persist for up to 18 months after infection. To identify antigens for improved diagnosis of acute infection, we probed protein microarrays displaying the polypeptide products of 1357 Toxoplasma exons with well-characterized sera from Turkey. The sera were classified according to conventional assays into (1) seronegative individuals with no history of T. gondii infection; (2) acute infections defined by clinical symptoms, high IgM titers, and low avidity IgG; (3) chronic/convalescent cases with high avidity IgG but persisting IgM; (iv) true chronic infections, defined by high avidity IgG and no IgM. We have identified 38 IgG target antigens and 108 IgM target antigens that can discriminate infected patients from healthy controls, one or more of which could form the basis of a 'tier-1' test to determine current or previous exposure. Of these, three IgG antigens and five IgM antigens have the potential to discriminate chronic/IgM persisting or true chronics from recent acutely infected patients (a 'tier-2' test). Our analysis of the antigens revealed several enriched features relative to the whole proteome, which include transmembrane domains, signal peptides, or predicted localization at the outer membrane. This is the first protein microarray survey of the antibody response to T. gondii, and will help in the development of improved serodiagnostics and vaccines.     

ELISA for the detection of specific IgM and IgG in human leptospirosis

ELISA was used to detect specific IgM and IgG in sera from humans with current or past leptospirosis. A serological pattern of a high IgM titre (greater than or equal to 1280), or moderately increased IgM (160-640) in conjunction with a low IgG titre (less than or equal to 20), with serovar copenhageni antigen was characteristic for approximately two-thirds of the sera from serovar icterohaemorrhagiae patients obtained in the first two months of the disease. The antigen was the supernatant of a heated and centrifuged culture of leptospires. Antigens were prepared from serovars copenhageni, grippotyphosa, hardjo and patoc. Sera from patients with icterohaemorrhagiae, grippotyphosa and hardjo infections showed cross-reactivity when different antigens were used. In past infections the IgG titres were clearly higher with the homologous antigen. ELISA for IgM and IgG allows the rapid diagnosis of acute leptospirosis.     

Association of the presence of residual anti-Toxoplasma gondii IgM in pregnant women and their respective family groups in Miracema, Northwest Rio de Janeiro, Brazil

The seroprevalence of toxoplasmosis in 832 pregnant women in Miracema, Rio de Janeiro, was determined and 75.1% (625) and 2.0% (17) were anti-Toxoplasma gondii IgG and IgM positive, respectively. Out of the 17 IgM positive pregnant women, only one had low avidity IgG corresponding to the acute phase of the infection. All the other women presented with high avidity IgG and also presented with residual IgM anti-T. gondii. Of this sample, 106 received home visits (this includes 11 family nuclei of pregnant women with residual IgM anti-T. gondii, 68 nuclei of only IgG positive pregnant women and 27 nuclei of pregnant women with no antibodies to anti-T. gondii), resulting in 267 individuals visited. Out of these 267 individuals, 21 were positive for IgG and IgM anti-T. gondii and were candidates for the IgG avidity test. All of them presented with high avidity IgG and residual IgM. Five of these IgM+ individuals were (5/238; 2.1%) relatives of IgM negative pregnant women. The other 16 (16/29; 55.2%) were relatives of IgM+ pregnant women who were positive for residual IgM anti-T. gondii. This association was statistically significant (p = 0.0000). The analysis presented herein raises questions regarding the presence of residual IgM anti-T. gondii such as genetic determinants or even constant antigenic stimuli for the same family cluster.     

Problems and limitations of conventional and innovative methods for the diagnosis of Toxoplasmosis in humans and animals

Diagnosis of toxoplasmosis is useful for human and animal health. Several techniques are employed for the diagnosis in feline and canine population. Coprological tests for the detection of oocysts in cat faeces are of little significance owing to short patency (15 days). Histological examinations of biological samples show a lack of reliability when the animals are infected with few parasites; the mouse inoculation is the most reliable method even if the detection of cysts in mice brain require 40 days. However tachyzoites of virulent strains can be isolated from peritoneal exudate 3-4 days after inoculation. Samples inoculation in cell cultures (VERO, human fibroblasts) requires specialized laboratories and fails if non viable parasites are present due to tissutal autolysis. Serological tests are the most used diagnostic methods; Dye test and IFAT that require intact tachyzoites are more sensitive and specific compared to IHA, LA, ELISA because, during the infection, the first significant increase of IgM and IgG antibodies was observed against cuticolar antigens. A PCR to identify T. gondii DNA in canine and feline biological samples was developed. The B1 PCR performed on blood samples was less sensitive than when it was performed on other biological fluids requiring 100 tachyzoites, instead of 10. Aqueous humor PCR results could be negative if the infection is low grade or is restricted to the posterior segment or the animal was previously treated with anti-Toxoplasma drugs. SNC disease may be also difficult to diagnose because an high serum IgG titer may be associated with locally production or leakage from serum through a compromised blood-CSF barrier. AB1 PCR was successfully applied for the diagnosis of Toxoplasma abortion in ewes requiring only 10 parasites in placental cotyledon samples; the test compared with mouse inoculation showed similar sensitivity. Discrepancies may have been due to a low and focal distribution of parasites in the tissues or to the presence of non viable parasites if the tissues are autolysed. In regard to diagnostic methods adaptable to slaughter testing, several serological tests have been studied (IFAT, ELISA, IHA) for detection of IgG in sheep, pigs, cattle using also recombinant antigens (gene fragments H4 and H11) to lack the cross reactivity. The problem is the antibodies fall to near background levels as the infection became chronic (6-10 months p.-i.). A highly sensitive and specific method (Toxo Taq Man) has been developed to detect and quantitate T. gondii burden in animal tissue samples (0.1 pg of T. gondii genomic DNA, which is equivalent to 1 bradyzoite) using T. gondii ITS1-derived primers and a fluorogenic probe via Real-Time PCR. This assay is compatible with automation technology for potential slaughterhouse use. The diagnosis of acute infection in human pregnancy is difficult since IgM antibodies can be detected for a very long time after the acute phase; an IgA increase is of more diagnostic value because can be detected only for 6-7 months while the short kinetics of IgE can be useful only to date the infection precisely. In addition an IgG seroconversion is essential for the diagnosis. Among the most reliable tests, IgG avidity test is useful when a single serum sample, in the first months of gestation, is available, but low avidity results may persist for as long as 1 year. For this purpose a panel of serologic tests must be performed (ELISA, EIA, ISAGA, IgG avidity, IFAT, Dye test) for IgM, IgA, IgG and IgE. The serological diagnosis of prenatal infection is difficult since maternal IgG are passively transferred in utero to the foetus and caution must be exercised in interpretation of IgM or IgA results. A technique of Western blots of paired maternal and baby sera for evidencing different bands in the blots of two sera was developed for this purpose (specificity 97-100%, sensitivity 96-98%). The most reliable methods for prenatal diagnosis are PCR, mouse inoculation and cultural techniques performed on amniotic fluid, foetal blood and peripheral maternal blood in pregnants serologically positive. PCR (targets B1, SAG-1, rDNA) with amniotic fluid performed from 18 weeks of gestation is more sensitive and more rapid than conventional diagnostic procedures. PCR has been successfully used to diagnose Toxoplasma encephalitis in immunocompromised patients (cerebral biopsy is the only diagnostic method) and in ocular toxoplasmosis. In this evenience it is useful the study of IgG, IgM, IgA profile of paired serum and aqueous humor (Western blots).     

ELISA间接法检测呼吸道合胞病毒和副流感病毒血清IgM和IgA抗体

建立了检测呼吸道合胞病毒(RSV)和副流感病毒(PFV)血清特异性IgM和IgA抗体的间接ELISA方法。在方法统一的基础上比较了检测IgG、IgM和IgA抗体的结果,证明检测血清IgM和IgA可以作为RSV和PFV感染的早期诊断指标。检测了120份临床急性下呼吸道感染患儿的血清,RSV-IgM检出率为33.3％,RSV-IgA为36.7％;PFV-IgM为27.5％,PFV-IgA为31.6％。提出了对RSV和PFV感染以检测特异性IgA替代IgM或两者互补的设想。     

Toxoplasmosis in Kosovo pregnant women

This study presents the initial results of a collaborative project aimed at the evaluation of Toxoplasma seroprevalence in a population of Kosovar pregnant women. The serum samples of 334 pregnant women were tested to detect IgG, IgM, IgG avidity for toxoplasmosis. Data regarding age, occupation, area of origin and education were also obtained for the pregnant women examined; 97/334 (29.4%) resulted positive for IgG antibodies, four of whom (4.1%) were also positive for IgM, (1.2% of the total population examined). All four IgM-positive pregnant women also demonstrated low avidity tests. The rate of IgG seroprevalence found in our study was lower than that observed in various European countries, especially those of western Europe. Conversely, the percentage of recent infections was higher than expected. The higher rate of infections could be the result of a recent toxoplasmosis epidemic in Kosovo, most likely due to the altered hygienic conditions caused by the forced transfer of the ethnic-Albanian population from an area of low (Serbia) to high (Kosovo) toxoplasmosis prevalence.     

Recombinant, truncated CD4 molecule (rT4) binds IgG

CD4 is a cell surface glycoprotein that identifies the subset of human T lymphocytes that induces sIg+ B lymphocytes to differentiate and secrete Ig after intimate T-B cell contact. In the course of studying a recombinant, truncated form of CD4 (rT4) we noticed that goat antibodies of apparently irrelevant specificities bound to immobilized rT4. To directly study whether rT4 interacts with Ig molecules, purified human IgG was added to rT4-coated wells and a dose-dependent interaction between IgG and rT4 was observed by ELISA. Purified myeloma IgG proteins bound to immobilized rT4 with the same avidity as polyclonal IgG that suggests that rT4-IgG binding was not due to the presence of anti-rT4 antibodies in the IgG fraction. IgG from 6 sera bound to rT4 in concentration dependent manner similar to purified IgG. Immobilized rT4 specifically bound IgG, and not IgM, IgA, IgD, or beta 2-microglobulin. The specific interaction of rT4 and IgG was also observed when IgG or IgM were immobilized, demonstrating that IgG binding was not a unique property of immobilized rT4. As with low affinity receptors for IgG, rT4 bound heat aggregated IgG with increased avidity. Neither anti-CD4 mAb nor dextran sulfate inhibited rT4-IgG binding. rT4 bound Fc but not F(ab)2 fragments. Each of the purified IgG subclasses; IgG1, 2, 3, and 4 bound to rT4 with similar avidity. Taken together, these data suggest that rT4 specifically interacts with a public structure on IgG Fc.     

Production and Evaluation of Toxoplasma gondii Recombinant GRA7 for Serodiagnosis of Human Infections

The precise diagnosis of the acute toxoplasmosis in pregnant women and immunocompromsied patients has critical importance. Most of the commercially available assays use the whole Toxoplasma soluble extract as the antigen. However, the assays currently available for the detection of specific anti-Toxoplasma antibodies may vary in their abilities to detect serum immunoglobulins, due to the lack of a purified standardized antigen. The aim of this study was production and evaluation of the usefulness of the recombinant Toxoplasma gondii GRA7 antigen for the serodiagnosis of Toxoplasma gondii IgM and IgG by ELISA. A total of 70 T. gondii IgM positive sera, 74 T. gondii IgG positive sera, and 60 sera from subjects who were not infected with T. gondii were examined. These sera were shown different absorbance values in ELISA test. To control the specificity of the rGRA7 other parasitic diseases, for example, echinococcosis, malaria, leishmaniasis, fascioliasis, and strongyloidiasis were tested of which none showed positive results. Sensitivity and specificity of the generated recombinant IgG ELISA in comparison with commercial ELISA (com ELISA) were 89% and 90%, and the sensitivity and specificity of the generated recombinant IgM ELISA were 96% and 90%, respectively. The results obtained here show that this antigen is useful for diagnostic purposes.     

Evaluation of IgG, IgM, and IgA antibodies to mycoplasma penetrans detected by ELISA and immunoblot in HIV-1-infected and STD patients, in São Paulo, Prazil

The aim of the present study was to determine the frequency of IgG, IgA, and IgM antibodies to Mycoplasma penetrans in HIV-1-infected patients and in patients with sexually transmitted diseases. We tested serum samples from 106 HIV-1-positive patients and 110 individuals with clinical symptoms of urethritis. ELISA and the immunoblot test were performed using M. penetrans lipid associated membrane proteins as antigen. By ELISA, we found a higher frequency (P < 0.05) of IgG against M. penetrans in HIV-1-infected and STD patients (25.5 and 17.3%) than in controls (1.2%), as well as a higher frequency of IgA (P < 0.05) (15.1 and 17.3% compared to 1.2%). For IgM, no differences were observed (P >/= 0.05) (3.8, 9.1, and 5. 8%, respectively). When the frequencies of IgG, IgM, and IgA antibodies of the HIV-1-infected patients were compared taking into account the CD4/CD8 cell ratios < 0.3 and >/= 0.3, no significant differences were observed between the two groups (13.3, 10, and 20%, compared to 20, 0, and 5%, respectively) (P > 0.05), possibly due to the low number of samples on which we could perform T-cell counts (53/106). The M. penetrans peptide of 38 kDa, considered immunodominant, was recognized in immunoblot by 51.8% of positive sera by ELISA for IgG, 50.0% for IgM, and 75% for IgA in the AIDS patients group, and by 47.4, 60.0, and 75.0%, respectively, in the sexually transmitted disease group. Cross-reactions in immunoblot for IgG were observed in sera from individuals infected with Mycoplasma pneumoniae and Mycoplasma hominis, and cross-reactions in immunoblot for IgA were observed in sera from individuals infected with M. hominis; all of them were ELISA negative to M. penetrans.     

The role of IgG avidity determination in diagnosis of Epstein-Barr virus infection in immunocompetent and immunocompromised patients

There is a high degree of variability in the serologic response to Epstein-Barr virus (EBV) infection, especially in viral capsid antigen (VCA)-IgM antibodies. Therefore, additional tests are needed to confirm primary infection. We evaluated the value of IgG avidity determination in diagnosis of EBV infection in immunocompetent and immunocompromised patients. A total of 236 serum samples from immunocompetent patients with symptoms suggestive of EBV infection were tested for the presence of VCA-IgM/IgG antibodies and IgG avidity. Using IgG avidity, acute primary infection was confirmed in 56.7% of the immunocompetent patients with positive and in 1.8% of patients with negative VCA-IgM. Recent primary infection was documented in 8.9% of the IgM positive and 3.5% of the IgM negative patients. In patients with indeterminate serology (equivocal IgM), 6.7% were classified by avidity index (AI) as acute primary infection, 10.0% as post-acute and 83.3% as past infection cases. Concerning the 32 immunocompromised patients, recent primary infection was documented in 3 of the 14 IgM positive patients. High AI was detected in 11 of these patients, indicating an IgM response due to reactivation. Determination of IgG avidity in combination with classical serologic markers seems to be a reliable method to confirm primary infection both in immunocompetent and immunocompromised patients. It may be especially useful to differentiate cases of primary infection in patients with undetectable VCA-IgM antibodies or indeterminate routine EBV serology.     

Evaluation of Anti-Toxoplasma IgG, IgM, and IgA in Mothers with Spontaneous Abortion in Zanjan, Northwest Iran

Toxoplasma gondii is one of the major agents of infectious abortions and due to its worldwide distribution can threat healthy pregnant women who had no previous exposure to this parasite. The present study was designed to investigate the contribution of T. gondii to spontaneous abortions in Zanjan, Northwest of Iran, using ELISA method. Blood Samples were collected from 264 mothers referred to the provincial hospitals of Zanjan due to spontaneous abortion. The sera were isolated and subjected to evaluate the anti-Toxoplasma IgG, IgM and IgA antibodies. The results showed IgG positive (IgG⁺) in 99 cases (37.5%). A total of 68 women (25.8%) showed seroconversion with IgM or IgA or both IgM and IgA. They included: IgM⁺ in 21 (8.0%), IgA⁺ in 23 (8.7%) and both IgM⁺ and IgA⁺ in 24 (9.1%) subjects. In 23 cases, positive titers of IgM and IgG were accompanied. In general, the analysis of anti-Toxoplasma antibody patterns, showed that about 17% of the spontaneous abortions were associated with serological patterns of acute infection. According to these findings, a considerable proportion of spontaneous abortions can be attributed to T. gondii in the study area.     

Follow-up of antibody avidity in BALB/c mice infected with Toxocara canis

In human Toxocara canis infection, an association has been shown between high IgG avidity in the chronic phase and low IgG avidity in recently acquired toxocarosis. The evolution of the antibody response in terms of avidity has been carried out through a T. canis infection in BALB/c mice. Infection with T. canis embryonated eggs (EE) was carried out with single doses (SD) of 6, 12, 50, 100, 200 or 1000 EE/mouse and with multiple doses (MD) of 200 and 1000 EE. Specific antibodies against T. canis (IgM+G, IgG, IgG1 and IgM) were detected by ELISA and Western Blot (WB) techniques in the presence and absence of urea. With the ELISA method, an increase in the avidity index (AI) of around 50% was detected from days 40-80 p.i. to the end of the study, with all the doses studied. The WB method showed the presence of high avidity antibodies bound to 100 kDa and 75 kDa T. canis proteins in all the cases when the IgM+G and the IgG1 antibodies were investigated. Antibodies of variable avidity were observed in those sera that recognized the group of low molecular weight proteins, between 37 kDa and 25 kDa.     

应用血清学方法鉴别急性和慢性病毒性乙型肝炎

本文用ELISA间接法检测急性和慢性乙型肝炎病人血清特异性抗HBcIgG,用ELISA捕捉法检测特异性抗HBcIgM。11例急性乙肝病人急性期抗HBcIgM100％阳性,抗HBcIgG全部阴性;恢复期抗HBcIgM 81.8％阴转,抗HBcIgG则100％阳转。17例慢性乙肝病人抗HBcIgM82.35％阳性,抗HBcIgG 100％阳性。被检血清经密度梯度超速离心,证实抗HBcIgM和抗HBcIgG两类抗体反应在急性和慢性乙肝病人血清中具有不同的动态规律。