IgG Avidity Index Research Articles

The relationship between TORCH complex false positivity and obstetric outcome in patients with antiphospholipid syndrome

The presence of TORCH IgM positivity is not a specific indicator of primary infection; the assessment of IgG avidity index has been shown to be useful in identifying or excluding primary infection in pregnant women with no pre-gestational TORCH serology. TORCH is an acronym for Toxoplasmosis, Others (HBV, syphilis, Varicella-Zoster virus, Epstein Barr virus, Coxsackie virus and Parvovirus), Rubella, Cytomegalovirus (CMV) and Herpes Simplex. Data from 54 pregnancies in women with antiphospholipid syndrome (APS) were assessed in comparison with data from 222 healthy pregnant women as controls. Each woman in both groups was systematically screened for TORCH IgG and IgM during pre-conceptional evaluation and/or at the beginning of pregnancy. The assessment of IgG avidity was also evaluated in order to identify primary infection or false positivity. A significant increase of CMV IgM false positivity in APS in comparison with controls was detected. A worse pregnancy outcome was observed among APS patients having CMV IgM false positivity in comparison with APS patients without false positivity; in particular a statistically significant lower neonatal birth weight and a lower neonatal birth weight percentile were observed. Our data suggest that the presence of CMV IgM false positivity could represent a novel prognostic factor for poor pregnancy outcome in APS patients.

Pitfalls in the diagnosis of congenital rubella syndrome in the first trimester of pregnancy

A 29-year-old woman, gravida 3 para 0, was referred at 19 weeks of gestation because of a maternal rubella infection during the first trimester of pregnancy. She consulted at 5 weeks for a rash, which, at that time, was considered to be urticaria. Her serological status for rubella was unknown at that time, and as rubella infection was not considered, serological investigations were not conducted. At 6 weeks, toxoplasma and rubella testings were performed as recommended by the French High Health Authority [Haute Autorité de Santé (HAS)]. HAS only recommends IgG testing for routine Rubella screening and both IgG and IgM testings for toxoplasma.1 Her results were negative for rubella-specific IgG and positive for toxoplasma-specific IgG [104 IU/mL (cutoff: 10.5 IU/mL)] and IgM [5.23 (cutoff: 1), Access 2, Beckman Coulter, Fullerton, CA, USA]. Because these findings suggested a recent toxoplasma infection, spiramycine was started pending the results of the IgG avidity test. The avidity index was high, 0.48 (cutoff: 0.30; Vidas bioMérieux, Marcy-l'Étoile, France), thus making postconceptional toxoplasma seroconversion very unlikely, and spiramycine was stopped. As recommended by HAS, all rubella seronegative patients have a subsequent rubella testing at around 20 weeks. Her second serology performed at 16 weeks indicated a seroconversion leading to IgM testing: rubella-specific IgG, 181.6 IU/mL (cutoff: 10 IU/mL; Architect Abbott, Wiesbaden Germany) and rubella-specific IgM, 1.48 (cutoff: 1.2; Vidas bioMérieux). Retrospective analysis of the serum collected at 6 weeks indicated that rubella-specific IgM was already positive at that time (3.15). The IgG avidity index was measured using our in-house urea wash method. This method is based on adding 6 M urea as a denaturing agent to the washing buffer to prevent the binding of low-avidity antibody to the antigen. Results are expressed as a ratio of absorbance of a single serum dilution with and without denaturing agent. An avidity index of <30% is considered as very low, between 30% and 70% as low, between 70% and 90% as moderate, and >90% as high.2 The IgG avidity index was 78% (moderate) at 16 weeks. Together with the analysis of IgM kinetics on both samples,2 the primary infection was dated at around 5 weeks, coinciding with the rash described by the patient. The ultrasound at 16 weeks was unremarkable. Amniocentesis at 18 weeks detected rubella viral RNA by RT-nested-PCR analysis3 indicating congenital rubella infection. The ultrasound scan at 19 weeks revealed intrauterine growth restriction, together with asymmetric bilateral microphthalmia (below the 5th percentile),4 opacity of the right lens (Figures 1 and 2), and an isolated hyperechogenic mitral focus. Because these signs indicated symptomatic fetal rubella infection, the couple asked for termination of pregnancy. The male fetus weighed 190 g (below the 5th percentile for 20 weeks). The pathology examination confirmed bilateral microphthalmia and the fetal infection with biopsies from the liver and the brain being positive for rubella viral RNA.

Prevalence of antibodies and RNA genome of hepatitis E virus in a cohort of French immunocompromised

BackgroundRecently, cases of chronic hepatitis E have been identified in immunocompromised patients. ObjectivesTo evaluate the prevalence of anti-HEV IgG antibodies and the persistence of HEV-RNA in sera of immunocompromised patients with regular follow-up at Saint-Louis Hospital in Paris, France. Study design307 samples collected from 261 HIV-infected patients and 46 kidney transplant (KT)-patients were retrospectively tested for the presence of the following hepatitis E virus (HEV) infection markers: anti-HEV IgM antibodies, anti-HEV IgG antibodies, anti-HEV IgG avidity index, and HEV-RNA. ResultsAnti-HEV IgG positive serology was found in 4 HIV-infected patients (1.5%) and 3 KT-patients (6.5%), leading to an overall seroprevalence of 2.3%. HEV-RNA detection was not observed among 55 HIV-patients at higher risk of chronic HEV (<200CD4 cells/mm3, elevated alanine aminotransferase (ALT) levels, and/or positive anti-HEV antibodies) and among 44 KT-patients. None of the seven patients had anti-HEV IgM antibodies, thereby excluding any acute infection. The IgG avidity index confirmed past HEV infection among tested patients. ConclusionsThe low seroprevalence observed in the Paris region does not warrant a systematic evaluation of HEV infection in immunocompromised patients. However, HEV infection must be examined as a possibility if unexplained increases in ALT should occur and after more common viral hepatitis infections are excluded.

Antiparasitic treatment suppresses production and avidity ofToxoplasma gondii-specific antibodies in a murine model of acute infection

Infection with Toxoplasma gondii during pregnancy may result in congenital transmission of the parasite. Infection is commonly diagnosed using serological tests for IgG, IgM and IgA antibodies. Avidity of IgG antibodies is used to exclude acute infection. Few studies have investigated the impact of antiparasitic treatment on the production of anti-T. gondii antibody and the avidity of IgG antibodies. We therefore investigated the production of IgG, IgM, and IgA antibodies and IgG avidity in a murine model of acute infection with 10 cysts of T. gondii. All antibody classes increased following infection. Treatment of mice with pyrimethamine/​sulfadiazine but not with spiramycin or azithromycin at dosages equivalent to those used in patients resulted in a significant decrease in the concentration of T. gondii-specific IgG and IgM antibodies postinfection. IgG and IgM antibody decreases were paralleled by a significant reduction in cyst numbers in brains of mice treated with pyrimethamine/sulfadiazine but not with other drugs. In contrast, treatment with atovaquone did significantly reduce the concentrations of IgM antibodies and resulted in reduced IgG avidity indices. T. gondii-specific DNA was not detected in blood between days 1 and 3. In conclusion, antiparasitic treatment with pyrimethamine/sulfadiazine and atovaquone appears to impact the generation of antibody responses against T. gondii. Future studies will have to determine the specific impact of antiparasitic treatment on antibody responses and the consequences for the management of patients infected with T. gondii.

Prospective Study of Congenital Toxoplasmosis Screening with Use of IgG Avidity and Multiplex Nested PCR Methods

Acute infection with Toxoplasma gondii during pregnancy can cause congenital toxoplasmosis. The aim of this study was to evaluate whether screening with the use of IgG avidity and multiplex nested PCR methods was effective to detect a high-risk pregnancy. In a prospective study, serum T. gondii IgG avidity was measured in consecutive 146 pregnant women testing positive for T. gondii antibody and either positive or equivocal for IgM. Multiplex nested PCR for T. gondii DNA on amniotic fluid, maternal blood, and umbilical cord blood were performed with informed consent. A total of 51 (34.9%) women presented with low IgG avidity (<30%), 15 (10.3%) presented with borderline avidity (30 to 35%), and 80 (54.8%) presented with high avidity (>35%) indices. Amniotic fluid obtained at amniocentesis or birth yielded positive PCR results in nine women with low IgG avidity indices. Of these nine women, three had congenital toxoplasmosis. None of women with high or border line IgG avidity indices had a positive PCR result in the amniotic fluid or congenital toxoplasmosis. No congenital toxoplasmosis was detected in women whose amniotic fluids yielded negative PCR results. Ingestion of raw or undercooked meat was found to be the main risk factor for acute T. gondii infection. Congenital toxoplasmosis screening with a combination of IgG avidity in the maternal blood and multiplex nested PCR in the amniotic fluid was useful for detecting a high risk pregnancy and diagnosing congenital toxoplasmosis.

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.

Hepatitis E Virus infection in HIV-infected patients with elevated serum transaminases levels

Increases in aminotransferases levels are frequently encountered in HIV-positive patients and often remain unexplained. The role in this setting and natural history of hepatitis E in HIV-infected patients are unknown. The aim of the study was to assess HEV infection in HIV-infected patients attending a Parisian hospital, with a current or previous cryptogenic hepatitis.191 plasma samples collected from 108 HIV-infected patients with elevated aminotransferases levels were retrospectively tested for the presence of hepatitis E virus (HEV) infection markers: anti-HEV IgM antibodies, anti-HEV IgG antibodies, anti-HEV IgG avidity index and plasma HEV RNA.One acute infection, documented by positive tests for anti-HEV IgM antibody, low anti-HEV IgG avidity index and plasma HEV RNA (genotype 3e), and three past infections were diagnosed, without any observed case of persistent infection. The acute hepatitis was benign and resolved spontaneously within two weeks. This infection was probably contracted locally. Acute HEV hepatitis can occur in HIV-infected patients but rarely explains cryptogenic hepatitis, at least in an urban HIV population, regardless geographic origin and CD4 counts.

Rubella outbreak on Tokunoshima Island in 2004: A population‐based study of pregnant women

The purpose of this study was to clarify the risk of rubella infection for pregnant women in the outbreak area. We performed a retrospective, population-based study on all 232 pregnant women during the rubella outbreak period in Tokunoshima Island. All women had a rubella hemagglutination inhibition (HI) titer drawn during their current pregnancy. In 61 women, HI titers were compared between the current and past pregnancies. Rubella IgG antibody titers were measured and IgG avidity index (AI) was calculated for 92 non-infected pregnant women. Of the 232 candidates, 22 pregnant women contracted rubella infection (congenitally infected infants: 2). Seventeen of 61 pregnant women showed a four-fold or greater elevation in HI titer when compared with previous titers. Their previous HI titers were all ≤64. Low IgG AIs (<30%) were only observed in women with a HI titer of ≤64 (92 non-infected women). The risk of maternal rubella infection in the outbreak was as follows: non-immunized pregnant woman and pregnant woman with a rubella HI antibody titer ≤64 and low IgG AI.

Hepatitis E virus in HIV-infected patients

Many cases of acute autochthonous hepatitic E virus (HEV) hepatitis have been reported in France, mainly from the south. Chronic HEV infection has recently been described in immunosuppressed patients. Although a potential risk of chronicity exists in HIV-infected patients, no survey has been conducted in this population. The aim of this study was to assess the sero-virological prevalence of HEV in French HIV-infected patients. Two hundred and forty-five HIV-infected patients followed at two Infectious Diseases Departments (one in the south, one in the north) were included from January to March 2009. Sera were collected from all patients and tested using anti-HEV IgG and IgM kits. HEV RNA was systematically amplified in the ORF2 region with an in-house method. The IgG avidity index of all IgG-positive samples was determined. Three of the 133 southern patients showed both anti-HEV IgG and IgM positivities, along with cytolysis and biological cholestasis; HEV RNA was amplified in two of these cases, whereas a low IgG avidity index was observed in all three samples. Twelve of the 130 remaining southern patients (9%) showed anti-HEV IgG positivity. The serological prevalence in the 112 northern patients was 3%, which was significantly lower than in the southern patients (P=0.04). No case of acute hepatitis was reported in the north, whereas the prevalence of patients with biochemical liver abnormalities was similar in both areas (P=0.22). In France, HIV-infected patients are at risk of HEV infection with a serological north-to-south gradient. No case of chronic HEV infection was detected in this study.

Hepatic cytolysis and Hepatitis E Virus infection in HIV-positive patients

Background Hepatitis E is an emerging infection in developed countries and progression to chronic hepatitis has been recently reported in some organ transplant recipients. The prevalence and evolution of hepatitis E in HIVinfected patients are unknown. The aim of the study was to assess hepatitis Ev irus (HEV) infection in HIVinfected patients attending a French Parisian hospital. Methods Out of 1250 HIV-infected patients attending the clinics, 108, with elevated transaminase episodes during the last four years, were included in the study. Two hundred and twelve episodes were recorded and 191 plasma samples (1 to 8 per patient), collected simultaneously to the episodes, were retrospectively tested for the presence of anti-HEV IgM and IgG antibodies and HEV RNA. Results An acute infection, documented by positive tests for anti-HEV IgM, low anti-HEV IgG avidity index (10%) and plasma HEV RNA (genotype 3e), was diagnosed in an homosexual patient with a moderate immunodepression (CD4+ lymphocyte count above 200/mm 3 ). This infection was likely locally acquired. It was benign and resolved within two weeks. No persistent carriage of HEV occurred. In addition, three past infections were evidenced, all of them in patients originating from countries with low socio-economic status. No persistent infection was diagnosed in our cohort. Discussion HEV should be tested in HIV-infected patients with elevated transaminase levels. HEV RNA detection should be used to diagnose the infection and monitor recovery.

Toxoplasmosis and pregnancy: Perinatal results and association of the IgG avidity test with congenital infection in pregnant women with positive anti-&lt;i&gt;Toxoplasma gondii&lt;/i&gt; IgM &lt;b&gt;[Abstract in English]&lt;/b&gt;

AIMS: To verify the perinatal outcomes in pregnant women with acute toxoplasmosis, and to determine if there was association between the results of Toxoplasma gondii-specific IgG avidity test and the presence or absence of fetal/neonatal infection. METHODS: A cross-sectional study included pregnant women with serological diagnosis of acute toxoplasmosis (presenting a positive Toxoplasma gondii-specific IgM test) attended at the outpatient unit for high-risk pregnancy of the Faculty of Medicine, Federal University of Mato Grosso do Sul, Brazil, in the period from November 2002 to November 2007. Test results demonstrating IgG avidity index above 30% were considered high avidity, while values below 30% were considered low avidity. Fetal and/or neonatal infection was defined by positive result for the polymerase chain reaction in amniotic fluid, or by a positive Toxoplasma gondii-specific IgM test in the newborn's serum. RESULTS: Considering all pregnant women referred to the outpatient unit for high-risk pregnancy in the period of study, frequency of pregnant women with positive Toxoplasma gondii-specific IgM was 10.8% (176/1.634). The rate of congenital infection in these patients was 4% (7/176). The IgG avidity test was performed in 162 patients (92% of the 176 pregnant women with positive IgM), and the avidity was high in 144 (88.9%). There was an association (p=0.003) between high avidity and no fetal/neonatal toxoplasmosis in our sample, with a prevalence ratio of 13.4 (confidence interval [CI] 95% 2.2-86.6). The positive predictive value of the avidity test (probability of congenital infection with a low avidity) was 22% (95% 6%-47%), while the negative predictive value (probability of absence of congenital infection with a high avidity) was 98% (95% CI 94% -99%). CONCLUSIONS: In this study the rate of congenital infection in pregnant women diagnosed with acute toxoplasmosis was 4%. In pregnant women with positive Toxoplasma gondii-specific IgM, results of Toxoplasma gondii-specific IgG avidity test were associated with the presence or absence of congenital infection, with a high negative predictive value (no fetal/neonatal infection when avidity was high).

Use of hepatitis E IgG avidity for diagnosis of hepatitis E infection

The diagnosis of acute hepatitis E infection is based on the detection of HEV RNA or specific IgM in immunocompetent patients. Viraemia and excretion of HEV RNA in faeces are not observed in all patients and commercial kits vary in their performance for anti-HEV IgM detection. Additional diagnostic tests must therefore be considered. The value of anti-HEV IgG avidity index for differentiating between acute infection and previous exposure to HEV in countries of low endemicity was investigated. 132 specimens were included, with 39 serum samples from patients with known HEV infection, studied retrospectively. IgG avidity index was high (>60%) in patients with previous infection ( n = 16) or polyclonal activation ( n = 3) but was low (<40%) in patients with acute infection ( n = 20). Then, 93 serum samples from patients, checking for acute hepatitis (detection of anti-HEV IgM but not of HEV RNA) were investigated. IgG avidity index was <40% in 77 of these patients, consistent with acute infection. It exceeded 60% in 15 patients, providing evidence of contact with HEV up to six months previously. One patient had an uninterpretable biological profile, with an IgG avidity index between 40% and 60%. IgG mature slowly during HEV infection, over a period of six months. IgG avidity index can therefore be used to exclude primary infection. This method should improve the diagnosis of acute hepatitis E.

Documento de consenso de la Sociedad Española de Infectología Pediátrica sobre el diagnóstico y el tratamiento de la infección congénita por citomegalovirus

Cytomegalovirus (CMV) is the leading cause of congenital infection in developed countries, affecting 0.3 to 0.6% of all live births in Europe. Primary CMV infection occurs in 1 to 4% of seronegative women during pregnancy and may be transmitted to the fetus in 40% of cases. Up to 10% of intrauterine CMV infections result in symptomatic congenital disease at birth. Half of these children and 13% of those born with asymptomatic infection will develop long-term sequelae, especially neurosensory hearing loss and mental retardation. Accurate diagnosis of primary maternal and fetal infection is now possible using the avidity index of anti-CMV IgG and virological testing to detect the virus in amniotic fluid. Symptomatic congenital infection may be preventable using CMV hyperimmune globulin during pregnancy. The gold standard for diagnosis of congenital CMV infection is the detection of the virus in urine within the first 2 weeks of life by rapid cell culture techniques (shell vial) or nucleic acid amplification of viral DNA (PCR). Retrospective diagnosis can be achieved by detection of viral DNA by PCR in dried blood spots (Guthrie card) collected on filter paper in the first days of life. Currently available drugs for the treatment of congenital CMV include ganciclovir and its oral prodrug valganciclovir. Treatment with intravenous ganciclovir for six weeks may prevent hearing deterioration in children with symptomatic congenital CMV infection and central nervous system involvement. Valganciclovir may be an excellent alternative because of its good bio-availability, providing plasma concentrations similar to those achieved with intravenous ganciclovir.

Improvement in the aetiological diagnosis of acute hepatitis C: A diagnostic protocol based on the anti-HCV-IgM titre and IgG Avidity Index

Background The gold standard for the diagnosis of acute hepatitis C (AHC) is seroconversion to anti-HCV/HCV-RNA positivity, an occurrence frequently missed in clinical practice. Objectives This study aims to diagnose AHC by the combined use of the HCV Avidity Index (HCV-AI) and HCV-IgM titre. Study design We enrolled 45 patients with AHC diagnosed by seroconversion to anti-HCV/HCV-RNA positivity and 36 with exacerbation of chronic hepatitis C (e-CHC) diagnosed at least 1 year earlier. HCV-IgM titres were determined by a commercial enzyme-linked immunosorbent assay (ELISA) and HCV-AI by an ELISA for detection of HCV IgG with a partial modification. For each test, specific cut-off values at four selected checking points were established during the observation (<10 days, 11–15 days, 16–20 days and >20 days from the onset of symptoms): for the HCV-IgM assay, the highest value in e-CHC +5% and for HCV-AI assay, the lowest value in e-CHC −5%. Results Around 90% of patients with AHC or e-CHC were correctly diagnosed at all checking points by combining the results of both tests. This practice afforded an improvement in sensitivity for the diagnosis of AHC, with the highest values at first and third checking points (92.3% and 92.6%, respectively) and an improvement in negative predictive value (NPV), with the highest value at first checking point (92.6%). Conclusions The diagnosis of AHC, made by seroconversion to anti-HCV/HCV-RNA positivity, was confirmed in more than 90% of patients by combining the results of IgG Avidity Index (IgG-AI) and HCV-IgM obtained in a single serum sample.

Molecular and serologic markers of acute dengue infection in naive and flavivirus-vaccinated travelers

A total of 520 European travelers with suspected dengue fever were examined, and acute dengue virus infection was confirmed in 127 of them. Molecular and serological tests for dengue diagnosis, according to their usefulness in the different stages of the disease, were performed. The accuracy of the IgM/IgG ratio and the IgG avidity index was confirmed during the early phase of the illness to discriminate the serologic status (primary versus secondary immune response) of patients who were either naive or previously vaccinated against other flaviviruses. Virologic markers of secondary infection were detected in 11.8% of nonvaccinated infected patients and in 92.6% of yellow fever vaccinated patients. The proper use of these simple methodologies could help in the identification of patients affected with secondary infection, who may be at a higher risk of developing a hemorrhagic disorder.

Characterization of neutralizing antibodies to Far Eastern of tick-borne encephalitis virus subtype and the antibody avidity for four tick-borne encephalitis vaccines in human

We assessed the humoral immunity of 290 vaccinated persons against tick-borne encephalitis (TBE). During the first year and 2 years after the primary three vaccinations the antibodies to the Far Eastern subtype tick-borne encephalitis virus strain P-73 were detected by neutralization test after immunization with FSME-Immune Inject vaccine (Baxter Vaccine AG, Austria) in 88.2% and 78.1% vaccinated persons, respectively; with Encepur ® Adult vaccine (Novartis Vaccines, Germany), in 100% and 100%; with the vaccine of the Chumakov Institute of Poliomyelitis and Viral Encephalitides RAMSci (Russia), in 100% and 94.1%; with EnceVir vaccine (Russia), in 88.2% and 83.9%; and after combined vaccination, in 100% and 92.7%. The dynamics of the decrease in IgG avidity index correlated with the changes of antibody titers determined by neutralization test. After the primary vaccination course, the titers of virus-neutralizing antibodies were high (6.3–7.4 log 2) when the avidity index of IgG antibodies were 31% and more; thus, this level can be considered immunologically significant. Two years after the primary vaccination course, the IgG avidity indexes of 60% and more can be regarded as significant on the background of the GMT decrease of virus-neutralizing antibodies. These results allow us to recommend all four vaccines for mass vaccination and an assay of IgG avidity, along with neutralization test, for a more adequate assessment of the level of postvaccination immune response.

Use of Toxoplasma gondi Specific IgG Avidity Assay for Diagnosis of Acquired Toxoplasmosis in Pregnant Women

Fetal infection by Toxoplasma gondii develops when non-immune mother becomes infected during pregnancy. Accurate dating of infection is mandatory before intervention to prevent dangerous complications. T. gondii IgM persists in patient's serum months after infection, providing no evidence of recent infection, beside its lack of specificity. T.gondii IgG avidity assay is expected to be a tool to distinguish recent and past infection. High avidity excludes recent infection in the preceding 16-20 weeks, however, low avidity doesn't help to differentiate between recent and old infection. Sera from 2070 asymptomatic Saudi Arabian pregnant women at different gestational stages were screened for T.gondii IgG by Indirect hemagglutination test. Enzyme–linked fluorescent assay (ELFA) was used for detection of T.gondii IgM, quantitative assay of IgG and IgG-avidity index (AI). Out of 401 IHA-positive sera, 151 (37.7%) samples were positive for T.gondii IgM, among which AI was low in 17 samples (11.3%), intermediate in 1 (0.6%), and high in 133 samples (88.1%). The possibility of recent infection in the IgM-positive sera is excluded since they contained high IgG AI (95% CI 83-93%). IgM-negative sera showed either high (in 97.8% of sera) or intermediate AI. This finding minimized the value of a positive IgM finding as single indicator for acute recent infection. Actually, it highlighted the value of IgG avidity assay to exclude recent infection. No significant correlation between level of IgG, and presence of either low or high AI (r = 0.096, p = 0.054). Likewise, no correlation was found between IgG level and presence of IgM in serum (r =0.092, p =0.046). To conclude, data suggested that pregnant women should be initially screened for IgG, to determine the patient's immune status; followed by IgM assay of IgG-positive sera. Negative serum IgM essentially excludes recent infection. Regardless the serum IgG level,AI assay should follow to exclude recent infection in the past 16-20 weeks. Assays should rely on accurate techniques (e.g., ELFA). This will reduce the cost of repeated assays in the majority of pregnant women during 1st trimester, avoid unnecessary examinations, antibiotic therapy, and anxiety burden.

Assessment of the value of detecting specific IgA antibodies for the diagnosis of a recently acquired primary Toxoplasma infection

To assess the value of detecting IgA antibodies for the diagnosis of a recently acquired primary Toxoplasma infection. IgA antibodies were screened in sera from 87 women with different serological profiles of Toxoplasma gondii IgM and IgG antibodies and Toxoplasma-specific IgG avidity. The IgM and IgG antibodies and the IgG avidity were measured with an automated Vitek Immuno Diagnostic Assay System (VIDAS). Anti-T.gondii IgA was measured with Platelia Toxo IgA TMB kits. All 12 sera obtained from women with clinical and/or serological evidence of a recently acquired Toxoplasma infection were positive for IgA. In 42 serum samples obtained more than 6 months after T. gondii infection from women with no clinical evidence of infection, but who had a positive IgM test and a high IgG avidity index, the IgA-enzyme linked immunosorbent assay (ELISA) test results were positive, negative, and doubtful in 16 (38.1%), 23 (54.8%), and 3 (7.1%) sera, respectively. In eight women, IgA was detected in sera collected more than 9 months after the onset of infection. The IgA test result was also positive in 11 of 12 sera (91.7%) obtained from women with no clinical evidence of toxoplasmosis, but who had a positive IgM test and a borderline IgG avidity index. The IgA-ELISA was negative in 21 sera obtained more than 2 years after the onset of T. gondii infection from women with no clinical evidence of toxoplasmosis, but who had a negative IgM test and a positive IgG test. These results show that IgA is not a dependable marker for a recently acquired primary Toxoplasma infection.

A longitudinal study of the IgG antibody response to HIV-1 p17 gag protein in HIV-1+ patients with haemophilia: titre and avidity.

The IgG response to HIV-1 p17 gag protein was studied for up to 6 years in 12 HIV-1-infected patients with haemophilia, who had seroconverted between 1982 and 1985. To assess any prognostic value, p17 IgG titres were compared with p24 IgG titres, CD4 cell counts and p24 antigenaemia. p17 IgG avidity index was also examined. A strong similarity was found between the IgG titre to HIV-1 p17 and that to p24. In patients who developed AIDS the decline in p17 IgG titres could precede by several years the drop in CD4 cells to under 200 cells/microliters; whereas some long-term asymptomatic patients (CDCII) had increasing p17 IgG titres and stable CD4 cell counts. Declining p17 and p24 IgG titres were not always associated with an increase in p24 antigenaemia. IgG titres were found to be better predictors of disease progression than CD4 cell counts or p24 antigenaemia. Patients who developed AIDS during the study were also characterized by a lower p17 IgG avidity than patients who remained asymptomatic. This result suggests that IgG avidity could have prognostic relevance and be of importance for host resistance to AIDS onset.

The effect of the human cytomegalovirus pp65 IgG-avidity index for the human cytomegalovirus primary infection in mice model

Objective To investigate the significance of human cyomeg Movirus(HCMV)pp65 IgG antibody avidity index(AI)for the clinical diagnosis of HCMV primary infection through the experimental model of HCMV primaly infection in BALB/c mice.Methods 6～8 weeks,female,specific-pathogen-free BALB/c mice were divided into 5 groups.6 mice in each group. And he mice were injected with 2×106 PFU/m1,2×105 PFU/mi,2×104 PFU/ml,2×103 PFU/ml and 2×102 PFU/ml of HCMV intraperitoneally respectively. Another 6 mice were injected intraperitoneally with the maximum dose of HCMV kept at 56℃ for 30 min as inactivated virus group.And HF negative control group was established at same time. All the mice ere sacrificed to obtain brain and lung tissues for the following experiments after 1 montll.(1)Tissue samples obtained from mice were inoculated in human embryo fibroblasts(HF)monolayers after routine treatment for virus isolation.HCMV specific eytopathie effect(CPE) was observed bv inverted phase-contrast microscopy.HCMV UL83 DNA in the ultures as tested by PCR and pp65 antigen was detected by indirect immunofluorescence.(2)Extracted mRNA from tissue samples and HCMV pp67 mRNA were analyzed by reverse transcriptase PCR(RT-PcR).(3)Immunoglobulin M(IgM)antibody and immunoglobulin G(1gG)antibody avidity Was investigated for their usefulness in distinguishing primary genital HCMV infections rom nonprimary infections with ELISA kit using truncated pp65 protein.ResultsHCMV can be isolated in the tissues from the mice injected with 2×106 PFU/ml and 2×105 PFU/m1.RT- PCR and ELISA showed positive results in the same groups.The infective rates were 100%.The analysis of the low doses groups,inactivated group and HF negative ontrol group all showed negative results.Conclusions BALB/c mice can be infected with HCMV and appeared as primary infection after1 month.Determination of HCMV pp65 IgM and HCMV p065 IgG-AI by ELISA incorporated with virus isolation and RT-PCR are helpful for distinguishing primary infections from nonpfimary infections.The detection of HCMV p65 IgM and HCMV pp65 IgG-AI by ELISA utilizing recombinant protein pp5 as antigens can be used for preliminary screening. Key words: Cytomegalovirus infections; Disease models,animal; PhosphoproteinsImmunoglobuli G; Antibody affinity; Enzyme-linked immunosorbent assay