Bactericidal and hemolytic activities of synthetic peptides derived from granulysin

Granulysin is a human polypeptide produced by cytolytic cells active against a broad range of microbes. Three peptides covering the regions 25-50 (Gr-1 and Gr-2) and 39-62 (Gr-3) of granulysin were synthesized, and their in vitro activity against Mycobacterium tuberculosis was evaluated. The most active peptide was Gr-1C, containing a disulphide bridge, with Minimal Inhibitory Concentration value of 10.1 microM. In concentrations of up to 50 microM, Gr-1 and Gr2 didn't exceed 30% of hemolysis.

[Human Metapneumovirus (hMPV) associated to severe bronchial asthmatic crisis]

Human Metapneumovirus (hMPV) is a recently reported agent of acute infection in the respiratory tract. It has been found in children as well as in young adults and elders. The clinical manifestations produced by hMPV are indistinguishable from those by common respiratory virus, and can evolve from asymptomatic infection into severe pneumonia. On the other hand, some authors have described cases of bronchial asthma exacerbation associated with hMPV infection. In this work we report a case of a child who presented a severe bronchial asthmatic crisis with a suspected viral associated infection. Immunofluorescence tests yielded negative results for sincitial respiratory virus, adenovirus, a-b influenza virus and parainfluenza 1, 2, 3, virus. In an attempt to detect the presence of hMPV, a RT-PCR was carried out to amplify sequences from both N and F genes. Using this approach, a positive result for hMPV was obtained. To our knowledge, this is the first description of a case of asthma exacerbation associated to hMPV in our region. In addition, these results are similar to previous reports where it was hypothesized that, like RSV, hMPV can trigger a respiratory chronic disease as asthma.

Evaluation of the diagnostic value of measuring IgG, IgM and IgA antibodies to the recombinant 16-kilodalton antigen of mycobacterium tuberculosis in childhood tuberculosis

OBJECTIVE

To evaluate the usefulness of the recombinant 16-kDa antigen (re-Ag16) of Mycobacterium tuberculosis in the serodiagnosis of tuberculosis (TB) in children.

MATERIALS

Seventy-four children with active TB, 49 apparently healthy contact children and 149 children suffering from non-mycobacterial diseases were evaluated. Detection of anti 16-kDa antigen IgG, IgM and IgA was performed by enzyme-immunoassay.

RESULTS

An increased mean antibody response to re-Ag16 was observed in contact children compared with non-mycobacterial disease patients (IgG assay: 89.1 enzymatic units [eu] vs. 40.8 eu; IgM assay: 64.7 eu vs. 38.1 eu; IgA assay: 138.2 eu vs. 78.2 eu for contact children and non-mycobacterial disease patients, respectively), indicating that anti-16-kDa antibodies could be elevated in response to infections even without clinically apparent TB. Setting the specificity as the 95th percentile of the contact group's ELISA units, the sensitivity of the IgG, IgA and IgM assays were 34%, 19% and 3% respectively; combining results of the IgG and IgA assays led to 43% positivity in children with active TB.

CONCLUSION

The detection of anti 16-kDa IgG and IgA may be useful as a complementary technique for the diagnosis of childhood TB. Recognition of this antigen seems to be heterogeneous; combining responses against other antigens may be a good strategy to improve the performance of this assay.

[Diagnosis of tuberculosis in children in provinces of Argentina]

Confirming the diagnosis of pediatric tuberculosis is cumbersome, due to the clinical features (generally paucibacillary forms) of the disease. This national study was undertaken in order to establish: the features of childhood tuberculosis at the time of diagnosis, the criteria on which the pediatricians based the diagnosis, the bacteriologic contribution to the diagnosis and the quality of notifications to the National Programme. Medical and laboratory records were reviewed for children under 15 years of age who were diagnosed with tuberculosis disease or primary infection during 1995. The study included children cared for at health centres from Argentinean provinces (capital city excluded) where pediatricians accepted to participate. Four hundred cases (17% of childhood notifications to the National Programme) and 81 primary infections were studied. The percentage of children studied by means of chest radiology, presence of symptoms, Mantoux test, case contact investigation and bacteriology were 95.3%, 79.6%, 90.1%, 92.7% and 35% for pulmonary cases, respectively, and 87.7%, 100%, 87.7%, 85.9% and 78.9% for extra-pulmonary cases, respectively. Of the evaluated pulmonary cases, 99.1% had abnormal x-rays, 79.0% had a tuberculin test > or = 10 mm, 79.8% had symptoms and 80.2% had a history of close contact. All extra-pulmonary patients had symptoms at the time of diagnosis; 63.0% had abnormal chest radiograph at diagnosis. Bacteriologic confirmation was achieved in 10.7% of the cases (20.8% and 40.0% of the investigated pulmonary and extra-pulmonary cases, respectively). This study would indicate that the diagnosis is made at relatively early stages of the disease. In general, recommendations of the Argentine Society of Pediatrics were followed. A low rate of bacteriological proof of diagnosis was observed, probably due to the scarce bacteriologic investigation and the low yield achieved in culturing pulmonary specimens. The study found under-register of cases and lack of precision in the information reaching the National Programme.

Antibody response to culture filtrate antigens of Mycobacterium tuberculosis during and after treatment of tuberculosis patients

SETTING

Many authors have shown rising titres of anti-mycobacterial antibodies after a few months of anti-tuberculosis treatment. This humoral response might persist for years, making the discrimination between current and old disease difficult.

OBJECTIVE

Characterisation of the humoral response to culture filtrates of Mycobacterium tuberculosis before and after treatment of tuberculous patients in order to identify those antigens that could provide information about disease activity.

METHODS

Anti-mycobacterial IgG response was determined during and after treatment of tuberculous patients by ELISA and immunoblot. Serum was taken from 71 active tuberculous patients (59 newly acquired and 12 relapse), 15 old tuberculous patients and 45 nontuberculous control subjects.

RESULTS

By ELISA, antibody response increased after 2 months of treatment. After chemotherapy was completed, the estimated number of antibodies remained at the same level. The level of specific antibodies in patients seems to reach the same level as that of control subjects 3 years after initiation of treatment. In Western blot, although each patient serum had its own characteristic banding pattern, differences between tuberculous patients and control subjects were found in the area below 20 kDa. Serum from tuberculous patients showed high levels of antibodies at the 14 kDa region. After the beginning of treatment, the intensity of the 14 kDa region band and the percentage of positive recognition tended to decrease. Therefore, one year after initiation of treatment, only seven of 13 cases who demonstrated anti-mycobacterial antibodies in ELISA revealed a mild but still positive reaction at the 14 kDa region; this reactivity disappeared 2 years after initiation of chemotherapy.

CONCLUSIONS

The 14 kDa region antigen seems to induce a humoral response that evolves in relation with the disease activity.

Clinical and epidemiologic characteristics of respiratory syncytial virus subgroups A and B infections in Santa Fe, Argentina

Respiratory Syncytial Virus (RSV) has two major antigenic groups, A and B. The implications of these variants in the epidemiology and pathogenesis of RSV infection are not well defined. This study was undertaken to compare the two RSV subgroups in patients admitted to hospital. Clinical and epidemiologic features of RSV subgroups in children under 30 months of age with proven RSV acute lower respiratory infections were examined during 4 winters from 1993 to 1996 in Santa Fe, Argentina. RSV typing was carried out with monoclonal antibodies in nasopharyngeal cells by indirect immunofluorescence. Of the 177 RSV positive nasopharyngeal aspirates obtained from 1993 to 1996, 85 (48%) were available for typing. Seventy-three (85.9%) specimens were identified as Subgroup A and 12 (14.1%) as Subgroup B. Except in 1993, in which only Subgroup A was detected, both variants circulated throughout the epidemic season. Subgroup A infections produced more severe disease than Subgroup B infections, as assessed by the length of the hospital stay and the use of respiratory support. This difference was age related, being evident in infants 0-6 months old. Patients with Subgroup B infections were also significantly less frequently breast-fed (95% vs. 75% for A and B subgroups, respectively; P = 0.04). It is concluded that the severity of disease in Argentinian patients admitted with acute RSV infections may be associated with Subgroup A strains as determined by a serogrouping method.

[Etiology of acute lower respiratory tract infections among children younger than 5 years old in Santa Fe]

The etiology of acute lower respiratory tract infections (ARI) and nasopharyngeal bacterial carriage in children less than 5 years old living in Santa Fe city, Argentina, was studied. A total of 518 children were included in the study: 450 suffering from ARI and 68 asymptomatic children. Blood samples, pleural effusions and nasopharyngeal secretions (NS) were obtained from children for bacterial isolations. NS was also used for fluorescent antibody techniques, and serum samples were employed for detecting IgM anti Chlamydia trachomatis. A bacterial pathogen was isolated from blood in 6.2% (14/224) of the children with ARI. A total of 11 Streptococcus pneumoniae (five of them oxacillin resistant), two Haemophilus influenzae and one Staphylococcus aureus strains were isolated. The most frequently detected pathogen in the ARI group was respiratory syncytial virus (RSV). It was found in 23.3% (105/450) of the children with ARI. Among children with risk of Chlamydia trachomatis infection, 24% presented high titters of specific IgM antibodies. Main bacteria carried in NS in the ARI group were H.influenzae (31.6%) and S. pneumoniae (23.4%) while viridans streptococci (26.5%), H.influenzae (23.5%) and Moraxella catarrhalis (22.1%) were more frequently isolated from controls. The most common pneumococcal types were 14 and 7 and the main type of H.influenzae was b biotype I. During the period of this study, the susceptibility of the pneumococcal isolates to oxacillin decreased from 60% to 50.8%, and the H.influenzae susceptibility to ampicillin fell from 92.3% to 79%. All the H.influenzae type b isolations were susceptible to ampicillin.

Inhibition of trypomastigotes' infectivity by a monoclonal antibody directed to a glycoconjugated fraction of epimastigotes of Trypanosoma cruzi

In this work it was shown that the infectivity of trypomastigote forms of Trypanosoma cruzi was affected upon the interaction with the Monoclonal Antibody (McAb) 2E9, which was raised against a glycoconjugated fraction of membranes of epimastigotes (Tulahuen strain). Characterization of the epitope recognized by this McAb, as well as its effects on complement mediated lysis and host cell invasion are reported. Immunocytochemical analysis showed that the McAb was reactive with two macromolecules (41-58 kDa) present on Trypanosoma cruzi epimastigotes (Tulahuen and Y strain), while it recognized several trypomastigotes macromolecules, showing a more intense reactivity with a band of 80 kDa. By indirect immunofluorescence, it was found there were subpopulations of blood and tissue culture derived trypomastigotes which attach the antibody to varying degrees. Studies using chemical or enzymatically treated antigens suggested that the McAb 2E9 was directed against carbohydrate epitopes, which were identified as being--galactosyl residues. In addition, preliminary results are shown, suggesting that the epitope recognized by the McAb 2E9 is involved in adhesion/or internalization of trypomastigotes.