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ABSTRACT
Duarte, MCMB. Cytokine inflammatory responses in nasopharyngeal aspirates of children under five years
with acute respiratory infections in Recife, Brazil. [Thesis] Recife: “Pós-graduação em Saúde Materno Infantil,
Instituto de Medicina Integral Prof. Fernando Figueira (IMIP)”; 2010. 136 p.
It is estimated that four million children die each year due to acute respiratory infections and half of these deaths
occur in infants under six months old. Viruses are responsible for much of the impact of these infections. It is
estimated that the human respiratory syncytial virus alone will result in at least 3.4 million hospital admissions and
between 66,000 to 199,000 deaths in children under five each year worldwide, with 99% of these deaths in
emerging countries. Several studies have shown that the type, load and virulence of the virus on the one hand,
and host factors on the other, such as age, genetic susceptibility and immune status are implicated in the
pathogenesis and severity of acute viral respiratory infection. Among these factors, the host immune response is
considered the main factor determining the disease severity and its consequences in the long term. Few studies
have evaluated the host immune responses against viral infection according to disease severity, or between
different viruses and atypical bacteria that can produce similar clinical syndromes. Furthermore, most studies have
evaluated the T helper 1 and T helper 2 immune responses cells, whereas T helper 17 immune responses have
rarely been described. The objectives of the thesis were to investigate whether cytokines concentrations in
nasopharyngeal aspirate differ according to several respiratory pathogens in children with acute respiratory
infection in Brazil and if the cytokines concentrations differ according to disease severity in children of low
socioeconomical status in Brazil, infected by human espiratory syncytial virus. A prospective, exploratory,
descriptive study was conducted from June 2008 to October 2009. In the first, study children under five years were
included with a clinical diagnosis of acute respiratory infection with up to seven days of illness, with Polymerase
Chain Reaction Multiplex positive for one of the following pathogens: human adenovirus, human bocavirus, human
metapneumovirus, human rhinovirus, human respiratory syncytial virus and Mycoplasma pneumoniae, and with no
co-detection for influenza A and human B, human parainfluenza 1, 2, 3 and 4, coronavirus NL63, 229E, HKUI and
OC43 and Chlamydophila pneumoniae. In the second study, children younger than two years were included with a
clinical diagnosis of acute respiratory infection with up to seven days of illness, with Polymerase Chain Reaction
Multiplex positive for human respiratory syncytial virus and with no co-detection for other respiratory pathogens
cited above. In both studies, children with a history of complex congenital heart disease, severe chronic lung
disease and immunodeficiencies were excluded. The cytokines interferon-γ, tumor necrosis factor-α, interleukin-4,
IL-5, IL-6, IL-8, IL-10, IL-12, IL-13, IL-17 and colony-stimulating factor macrophages and granulocytes were
measured in nasopharyngeal aspirate using ELISA. In the first study, 71 children under five with acute respiratory
infection by a single respiratory pathogen - human respiratory syncytial virus (23), human metapneumovirus (11),
human adenovirus, human rhinovirus, human bocavirus (10 each) or Mycoplasma pneumoniae (7) were
evaluated. None of the children required mechanical ventilation and all survived. In general, the cytokines
concentrations showed no differences between the pathogens. Among the exceptions, IL-17 was higher in
children with Mycoplasma pneumoniae when compared to children with viral infection (p = 0.036). Further studies
are needed to elucidate the role of the Th17 response in acute respiratory infection. The second study describes
the cytokines concentrations in nasopharyngeal aspirates of 44 children infected only by human respiratory