Acanthamoeba-specific human T-cell clones isolated from healthy individuals

Abstract

T-cell responses to pathogenic free-living amoebae, Acanthamoeba sp., were analyzed in healthy Japanese individuals. Of 20 healthy subjects, 10 (50%) showed significant proliferative responses of peripheral blood mononuclear cells to the soluble amoebic antigens in vitro. The antigens used were not mitogenic, and no evidence of amoebic superantigens was available. We established human T-cell clones reactive to Acanthamoeba, all of which were CD3- and CD4-positive, CD8-negative, and TCR-alpha beta-positive. We isolated two strains of Acanthamoeba from two patients, one from a patient with meningoencephalitis (CSF strain) and the other from a patient with keratitis (K strain). Of 13 clones, 11 were reactive to the K-strain as well as to the CSF-strain antigen under human leukocyte antigen (HLA)-DR restriction, whereas the other two were specific for the K-strain antigen. All but one clone tested showed TH1-equivalent functions because these cells produced interferon (IFN)-gamma in response to the amoebic antigen but produced no detectable level of interleukin 4 (IL-4). These results suggest that immunocompetent hosts might have acquired protective immunity mediated by Acanthamoeba-specific T-cells during natural sensitization.

Acanthamoebaspp. as Agents of Disease in Humans

“…Few studies have been conducted to investigate the interactions of Acanthamoeba with T lymphocytes. Tanaka et al (439) examined T-cell responses to Acanthamoeba antigens in healthy human subjects. T-cell clones from these subjects were established and analyzed for biological and functional activities.…”

“…The T-cell clones were categorized as being Th1 cells involved in delayedtype hypersensitivity reactions in that they produced gamma interferon in response to amebic antigens. Based on their observations, Tanaka et al (439) suggested that the low incidence of symptomatic disease in humans might be due to acquired protective immunity induced by T-cell responses.…”

Autoimmunity in the Mediation of Granulomatous Amoebic Encephalitis: Implications for Therapy

“…Affected patients, including healthy individuals upto 90%, carry the Acanthamoeba-reactive antibodies of IgM, IgG, and IgA isotypes with no significant differences between males (86.2%) and females (89.2%), indicating that humans are regularly exposed to Acanthamoeba and become sensitized with the amoebic antigens (Chappell, et al, 2001, McClellan, et al, 2002, Schuster, 2002, Khan, 2005a, Brindley, et al, 2009, da Rocha-Azevedo, et al, 2009. It has been reported that T cells from healthy individuals can react to Acanthamoeba antigens obtained from CSF and antigen-specific T cell clones capable of producing IFN-also have been derived (Tanaka, et al, 1994). Likewise, peripheral blood mononuclear cells from rheumatoid arthritis patients shows proliferative responses to A. polyphaga (Shadidi, et al, 2001).…”

Caracterização e filogenia moleculares de Acanthamoeba.

“…Tais estudos seriam de grande interesse em saúde pública, uma vez que foi mostrada recentemente a presença de Acanthamoeba em mais da metade das piscinas analisadas na Alemanha, assim como em quase 100% das amostras de solo da Turquia (87) , além da observação feita no Japão de que cerca de metade dos indivíduos examinados apresentou anticorpos contra essas amebas (124) .…”

“…Além disso, Acanthamoeba é o hospedeiro natural de diversas bactérias, como várias Chlamydiales (33) e, especialmente, Legionella pneumophila, causadora da doença dos legionários em humanos (101,106,126) , o que aumenta ainda mais sua importância tanto ecológica como em saúde pública. Além disso, Acanthamoeba é freqüentemente isolada do trato respiratório superior de indivíduos assintomáticos (55,124) , sugerindo que o contato entre essas amebas e seus hospedeiros potenciais é bastante intenso. …”