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The World Health Organization (WHO) lists tuberculosis (TB) as the most important fatal infection worldwide (WHO 2009). The development of a new diagnostic test for TB infection is an important component of the Global Plan to Stop TB and the WHO Stop TB Strategy. In 2005 alone, an estimated 8.8 million individuals were infected with TB and 1.6 million people died of the disease (WHO 2009). Importantly, less than one half of the total 8.8 million estimated cases were diagnosed as smear-positive; the diagnosis of smear-negative patients has proven to be more challenging. Currently, a definitive diagnosis of both pulmonary TB (PTB) and extrapulmonary TB (EPTB) relies on the time consuming culture of mycobacteria. A vast majority of TB cases occur in developing countries that have limited resources. Rapid, inexpensive diagnostic tests would aid these countries in limiting the spread of infection within their communities (WHO 2009). In addition, molecular methods based on nucleic acid amplification to diagnose TB infection are rapid, highly specific and more sensitive than microscopic examination of smears, but are less sensitive compared to culture assays for smear-negative TB cases (Abebe et al. 2007).Serological tests that rely on the detection of antibodies against Mycobacterium tuberculosis-specific antigens possess several advantages: they are simple, inexpensive and feasible for the diagnosis of TB. Potential M. tuberculosis antigens were recently reviewed in a metaanalysis. A total of 254 studies were identified that encompassed nine native proteins, 27 recombinant proteins, 15 lipid-derived antigens and 30 combination antigen targets. These results indicated that highly specific tests frequently exhibited poor sensitivity, which limited the use of these antigens when a single antigen was used in the assay (Steingart et al. 2009). Recently, there has been renewed interest in the development of antibody-based diagnostic assays that utilise multiple antigens to achieve high sensitivity and specificity (Abebe et al. 2007). Many attempts to develop a serologic TB test have been made. These assays need to discriminate active from latent infection, avoid cross-reactivity with Bacillus Calmette-

We report on the measurement of saliva anti-Purified Protein Derivative sIgA and 38kDa antibodies from 127 children, of whom 31 were strong tuberculosis suspects and 96 were healthy contact children. The results concerning the percentage of children with antibody reactivity to PPD and 38kDa antigens showed that, of these 2 antigens, 38kDa induced higher reactivity in patients positive and negative for the Tuberculin Skin Test (28% and 16.6%, respectively) in comparison to controls positive and negative for the TST (11.7% and 7.1%, respectively). There was a statistically significant difference between patients positive and controls negative for the TST. In relation to the Purified Protein Derivative antigen, while 14.2% of patients positive for the TST showed antibody reactivity to the PPD antigen, no patients negative for the TST had reactivity to this antigen. The findings suggest that these two antigens seem be associated with a different development of the mucosal defence mechanisms mediated by sIgA against Mycobacterium tuberculosis. Key-words: Tuberculosis. Warao. Secretory IgA. Tuberculin skin test. RESUMOForam dosados anticorpos sIgA anti-Purified Protein Derivative e 38kDa da saliva de 127 crianças, das quais 31 eram de pacientes altamente suspeitos de tuberculose e 96 eram provenientes de crianças saudáveis, que tiveram contato com pacientes. Os resultados referentes à porcentagem de crianças, reativas ao PPD e ao antígeno 38kDa, mostraram que destes dois antígenos, o 38kDa induziu maior reatividade em pacientes positivos e negativos ao Tuberculin Skin Test (28% e 16,6%, respectivamente), em comparação aos controles positivos e negativos ao TST (11,7% e 7,1%, respectivamente). Houve diferença estatisticamente significativa entre pacientes positivos e controles negativos ao Tuberculin Skin Test. Em relação ao antígeno PPD, enquanto 14,2% de pacientes positivos ao TST mostraram anticorpos reativos ao antígeno Purified Protein Derivative, nenhum paciente negativo ao TST foi reativo ao antígeno. Os achados sugerem que, aparentemente, estes dois antígenos estão associados a desenvolvimento distinto dos mecanismos de defesa da mucosa mediados por sIgA contra Mycobacterium tuberculosis. Palavras-chaves: Tuberculose. Warao. IgA secretória. Teste cutâneo da tuberculina.

Observational studies on the humoural immune responses of the Warao indigenous people from Delta Amacuro, an isolated area, were compared with urban residents of the Venezuelan capital. Mycobacterium tuberculosisspecific reactivities (IgM, IgE, sIgA, IgG and IgG subclasses) Key words: tuberculosis -Warao -Creole -IgG subclasses -purified protein derivative -diagnosis Tuberculosis (TB) diagnosis needs to be improved, as it largely depends upon clinical examination and radiographic findings, mainly confirmed by sputum smear microscopy and bacterial culture (Murray et al. 1980). The latter requires a long cultivation period and diagnostic confirmation still relies on sputum smear examinations. Many alternative methodologies have been applied in TB diagnosis, such as western blot, microscopic observed direct sensitivity culture, PCR and cell-mediated immune response reactions (Moore et al. 2006, Negi et al. 2006. These methods require trained personnel and specific laboratory conditions, which hinder their implementation in many areas of high TB endemicity (mainly low-income countries) and field work application. On the other hand, there are other options that are currently under evaluation, including antibody detection by serology. While specific antibody detection by serology is under evaluation for a definitive demonstration that the humoural response can be used as a tool for the diagnosis of TB, future studies should be carried out in order to combine serological and cellular methods, such as T.SPOT-TB or Quantiferon Gold assay, which are considered to be approved tools. Regarding the immunodiagnosis of TB based on the T cell response to ESAT-6 and purified protein derivative (PPD) antigens, recently it has been reported that the IFN-γ assay using ESAT-6 as an antigenic stimulus has the potential to be used as a tool for the immunodiagnosis of early TB in children ( Van-Lume et al. 2008).The demand for a rapid, reliable, cost-effective and easy TB diagnostic tool focuses on antibody detection by serology (Bothamley 1995). It has been reported that the isotypic restriction of antibodies correlates with the biochemical nature of antigens; most antibodies against proteins are of IgG1 and IgG3 isotypes, while in those against carbohydrates IgG2 is over-represented (Chiang et al. 1997, Gupta et al. 2005. This is reflected in vivo where, for instance, antibody responses to viral proteins are mainly of the IgG1 and IgG3 subclasses. In contrast, bacteria carbohydrates usually induce type 2 T-independent responses, mainly of the IgG1 and IgG2 isotypes. Several ELISA tests have been attempted and results have presented a large variability in their accuracy depending on the antigen employed (one alone or a pool) (Chiang et al. 1997, Gupta et al. 2005, the immunoglobulin (Ig) class, the subclass measured (Radin et al. 1983, Daniel & Debane 1987, Pottumarthy et al. 2000, Conde et al. 2004, Imaz et al. 2004 and Mycobacterium tuberculosis strain variation (Alde et al. 1989, Zheng et al. 1994, Raja et al. 2002. This indicate...

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