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Clinical and Vaccine Immunology, October 2006, p. 1071-1078, Vol. 13, No. 10
1071-412X/06/$08.00+0     doi:10.1128/CVI.00140-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Human Immunodeficiency Virus-Infected Patients with Prior Pneumocystis Pneumonia Exhibit Increased Serologic Reactivity to Several Major Surface Glycoprotein Clones

Veterans Affairs Medical Center,¹ Division of Infectious Diseases, Department of Internal Medicine,² Division of Epidemiology, Department of Environmental Health, University of Cincinnati College of Medicine, Cincinnati, Ohio³

Received 12 April 2006/ Returned for modification 22 May 2006/ Accepted 25 July 2006

Recombinant clones of the carboxyl terminus of the major surface glycoprotein (MsgC) of Pneumocystis jirovecii are useful for analyzing serologic responses in humans. However, there is no standardized set of antigens in general use, which could lead to conflicting results. We have previously shown that human immunodeficiency virus type 1 (HIV-1)-infected patients with prior Pneumocystis pneumonia (PcP⁺) responded more frequently and more strongly to a clone of MsgC than did HIV-1-infected patients without PcP (PcP^–). Here we test three new clones of MsgC to determine the effect of antigenic sequence variation on immune reactivity in blood donors and HIV-infected patients previously analyzed for reactivity to our original MsgC clone. In Western blot analyses, PcP⁺ patients exhibited the highest frequency of reactivity to each MsgC clone, and the frequency of reactivity with all four MsgC clones together was significantly higher in sera from PcP⁺ patients than in sera from the other patient groups. Furthermore, in an enzyme-linked immunosorbent assay we found that the PcP⁺ population had the highest level of reactivity to two of the four clones tested. One of the new clones could distinguish between PcP⁺ and PcP^– populations, and two MsgC clones could distinguish blood donors from the other patient populations. The results show that inherent differences in MsgC amino acid sequence can affect recognition by antibodies independently of variations in protein length or patient population, and the utility of a clone depends on its sequence and on the populations tested.