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The present study was conducted to determine the prevalence and significance of Pneumocystis carinii antigenemia in patients with acquired immunodeficiency syndrome (AIDS) and clinically or invasively diagnosed P. carinii pneumonitis. Single serum specimens from 20 AIDS patients invasively examined for P. carinii organisms and 106 AIDS patients with a clinical diagnosis only of P. carinii pneumonitis were blindly tested for P. carinii antigenemia by a counterimmunoelectrophoresis assay. In the 20 specimen-documented cases, the antigen test demonstrated a sensitivity of 75% and a specificity of 90%. The positive predictive value of the test was 90%, while the negative predictive value was 70%. In AIDS patients with specimen-documented P. carinii pneumonitis, the prevalence of P. carinii antigenemia coincided almost exactly with the prevalence of positive invasively obtained specimens (60 and 59%, respectively). In patients with a clinical diagnosis only of P. carinii pneumonitis, half as many (30%) were found to exhibit antigenemia. Sequential P. carinii antigen titers determined by a new latex agglutination technique on three AIDS patients with specimen-documented P. carinii pneumonitis demonstrated the influence of specific therapy upon P. carinii antigenemia and its potential prognostic application.

A new latex particle agglutination test for direct detection of Haemophilus influenzae type b polyribose phosphate antigen in serum, cerebrospinal fluid, or urine was evaluated from studies at four clinical centers. Although use of a serum buffer significantly reduced inconclusive agglutination of the latex particles, the retesting of serum samples, after heat inactivation and dilution, resolved all serum samples, with one exception, as reactive or nonreactive for the presence of the polyribose phosphate antigen. A clinical accuracy of 100% was obtained for the latex particle agglutination method in respect to its capability for detection of polyribose phosphate antigen in all patients with confirmed infection by H. influenzae type b.

Although the growth characteristics of Pneumocystis carinii have been described in several cell culture systems, the response of this organism to the drugs of choice, trimethoprim-sulfamethoxazole and pentamidine isethionate, have not been described in vitro. The effect of various concentrations of drugs against P. carinii on the growth of this potentially hazardous opportunistic organism as well as the methodology for in vitro assay of these agents have been detailed. Fluorescence profiles illustrating size ranges of trophozoites and cysts derived from cell culture are described.

Heterosexual controls were found to have significantly higher titers of immunoglobulin G antibody to Pneumocystis carinii than did patients with the acquired immunodeficiency syndrome (AIDS) and P. carinii pneumonitis, human immunodeficiency virus (HIV) antibody-positive or -negative homosexual male "gay bar" patrons, and HIV antibody-positive or -negative commercial plasma donors. The T-helper/T-suppressor lymphocyte ratios of HIV antibody-negative homosexual male gay bar patrons were slightly depressed (mean = 1.31 +/- 0.54) compared with those of heterosexual controls (mean = 1.79 +/- 0.32). In addition to other recognized factors, preexisting humoral as well as cell-mediated immune deficits before infection with HIV may help to explain the prevalence of and morbidity and mortality associated with P. carinii pneumonitis in AIDS patients.