Serodiagnosis and Immunotherapy in Infectious Disease最新文献

Antibodies which react with toxoplasma antigens (natural antibodies) can be found in patients without other evidence of toxoplasma infection. The natural antibody profile of 37 sera which were Dye Test (DT) negative was investigated by Western blotting with toxoplasma antigens. These 37 sera comprised 11 which were indirect haemagglutination test positive for toxoplasma antibodies, 8 rheumatoid factor positive and 18 from patients with acute viral infections. These three groups of sera could not be distinguished from each other, or from pooled sera from patients not infected with toxoplasma, by characterising the Western blot reactions.

Serology is valuable for assessing malarial transmission levels, monitoring the effectiveness of control measures, detecting latent foci and screening blood donors in malaria-free areas. Only a Plasmodium falciparum antigen, obtained from culture, is commercially available for serological testing, the rational being the cross-reactivity among blood stages of different Plasmodium species. We have compared the frequency of cross-reactivity of sera from individuals who had recovered from clinical malaria caused by P. vivax (group Pv) or P. falciparum (group Pf) with blood stage antigens of either parasite. In both groups, a higher seropositivity, detected using indirect fluorescent antibody test (IFAT), was observed with the homologous antigen. Since the cross-reactivity observed with the heterologous antigen could reflect previous malaria infections, we analysed the reactions with sera from mono-infected individuals with either Pf or Pv and observed a low level of cross-reaction (∼ 20%). Our results suggest that the Pf antigen used in the routine of serology does not replace the Pv antigen, and that the two antigens should be used simultaneously to avoid false negative reactions, especially in primary infections.

A total of 214 serum samples obtained from leprosy patients (96 with the lepromatous form, 36 with the tuberculoid form, 33 with the indeterminate form, and 19 with the borderline form) before and during chemotherapy, from household contacts (n = 18) and from controls (n = 12) were submitted to the M. leprae particle agglutination test (MLPA) and to enzyme-linked immunosorbent assay (ELISA) for the detection of anti-phenolic glycolipid (PGL I) antibodies. ELISA was more sensitive for all clinical forms of leprosy, with greater seropositivity for the lepromatous form (54.64%). For 88 patients with the lepromatous form, we noted that the shorter the time of treatment (≤ 3 years), the higher the percentage of seropositive results (P ≤ 0.01). The present results suggest that both tests could be used to monitor leprosy treatment and in epidemiologic surveys.

ELISA, the usual screening test for HCV infection, may yield nonspecific results. Most laboratories, therefore, for corroboration perform PCR. However, a negative HCV-PCR does not prove nonspecifity of the initial ELISA test and therefore an immunoblot has to be performed. RIBA-II was used for that purpose for several years, but suffers from a high number of indeterminate results. We therefore compared RIBA II results of 75 sera with those of RIBA III, Matrix, Western Blot (Murex) and INNO-LIA tests. Of 34 sera that were positive in RIBA II, all were also positive in the four other immunoblots. Similarly, these 4 tests showed concordantly positive results in 13 of 27 RIBA II indeterminate sera. In the remaining 14 (RIBA II indeterminate) sera the four immunoblots displayed no uniform results but various combinations of positive, indeterminate and even negative results. Similar results were found with 13 RIBA II negative (ELISA positive) sera. These data may indicate less sensitivity as well as some nonspecificity of some of the immunoblots. In general, however, the four newly developed immunoblots proved to be more sensitive than RIBA II. This obviously is not caused by the inclusion of the NS₅-antigen but by improvement of the conventional antigens. Only one serum was found in which the NS₅-band was crucial for its positivity. In conclusion, for corroboration of some HCV-ELISA positive, PCR negative sera, more than one immunoblot may be necessary.

The antibody responses to Epstein-Barr nuclear antigen (EBNA) polypeptides were analyzed by immunoblotting in 93 patients with autoimmune connective tissue diseases (ACTD) in comparison with 50 clinically healthy control subjects. Antibody frequencies to EBNA-2, -4 and -6 were signficantly higher in patients than in controls. Among the patients with ACTD, those with systemic lupus erythematosus (SLE) showed a significant increase in the frequency of anti-EBNA-3 antibodies. These results confirm the particularity of the antibody responses against Epstein-Barr virus (EBV) polypeptides in patients with ACTD; they could either reflect basic immune disturbances or suggest a participation of EBV in the pathogenesis of the disease.

A study of two ELISA methods (Eti-toxok-M, Sorin; Vidas Toxo IgM, bioMerieux) and one agglutination (Toxo Isaga, bioMerieux) was carried for the detection of specific IgM antibodies to Toxoplasma gondii in Southern Spain in different population groups. For diagnosis of acute toxoplasmosis ELISA methods showed 100% sensitivity, 99.4% specificity, 12% predictive value positive and 100% predictive value negative. Toxo Isaga showed 100% sensitivity, 99.5% specificity, 15% predictive value positive and 100% predictive value negative.

Of 135 serum samples from 135 patients suspected of hepatitis C virus (HCV) infection, 67 were detected by Abbott IMX antibody assay, 89 by Murex anti-HCV (version III), and 47 by Roche Amplicor polymerase chain reaction (PCR). Furthermore, 44 of the 62 positive serum samples by both Abbott and Murex antibody assays, 2 of the 27 positive samples by Murex antibody assay only, none of the 5 positive samples by Abbott antibody assay only, and one of the 43 negative samples by both Abbott and Murex antibody assays had measurable HCV RNA by Roche Amplicor PCR, suggesting active hepatitis C viremia. Whereas Abbott and Murex antibody assays were in agreement with each other in 103 of the 135 serum samples tested, they showed discrepancy with regard to the other 32. Despite generating a small percentage of false positives, Abbott and Murez antibody assays are useful in monitoring serum antibody levels of the past or continuing hepatitis C virus infection. Abbott IMX appears to be more specific than Murex anti-HCV (version III). The use of Roche Amplicor PCR provides a means of revealing active hepatitis C viremia, and helping clarify antibody indeterminate serum samples.

In our earlier studies, a rapid monoclonal antibody-based direct immunofluorescence (IF) test for respiratory syncytial virus (RSV) antigen in nasopharyngeal aspirates (NPAs) proved sensitive and specific, and dual virus infections were very rare when the test was used during the winter RSV season. We therefore recommended that virus isolation in cell culture be restricted to RSV antigen-negative specimens when RSV infection was highly prevalent (October to March in the UK). We reviewed the effect of this policy on the detection of RSV and other viruses in NPAs. The number of NPAs received each RSV epidemic increased markedly with time (3804 in 1984–88, 4569 in 1989–93, P < 0.0001), while during the test of the year the numbers declined slightly (753 vs. 700 for the same periods, P < 0.05). The RSV positivity rate increased October to March (1447/3588 (40%) in 1984–89, 2357/4591 (48%) in 1989–94, P < 0.0001). Restricted use of virus isolation led to a dramatic decline in the yield of RSV in cell culture from RSV IF-negative NPAs (196/3804 (5.2%) for 1984–88, 30/4569 (0.66%) for 1989–93, P < 0.0001). The already low yield on non-RSV respiratory viruses in cell culture was not affected by this policy. A strategy is proposed for the detection of RSV and other respiratory viruses in NPAs which may make virus isolation on such specimens obsolete.

A total of 214 serum samples obtained from leprosy patients (96 with the lepromatous form, 36 with the tuberculoid form, 33 with the indeterminate form, and 19 with the borderline form) before and during chemotherapy, from household contacts (n = 18) and from controls (n = 12) were submitted to the M. leprae particle agglutination test (MLPA) and to enzyme-linked immunosorbent assay (ELISA) for the detection of anti-phenolic glycolipid I (PGL I) antibodies. ELISA was more sensitive for all clinical forms of leprosy, with greater seropositivity for the lepromatous form (54.64%). For 88 patients with the lepromatous form, we noted that the shorter the time of treatment (≤ 3 years), the higher the percentage of seropositive results (P ≤ 0.01). The present results suggest that both tests could be used to monitor leprosy treatment and in epidemiologic surveys.