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Neopterin concentrations are associated with immune activation, which plays a crucial role in AIDS pathogenesis. Therefore, the measurement of neopterin concentrations is reliable for monitoring and predicting the course of  HIV infection:

 (Figure, adapted from Fuchs D, Wachter H. Neopterin – ein Marker für den zellulären Immunstatus - Bedeutung bei AIDS, ARC und AIDS-Risikogruppen, in: AIDS (Gschnait F, Wolff K, eds.), Springer-Verlag, Wien, New York, 1985, pp 97-127

Neopterin concentrations reflect activated T-cells -

Activated T-cells are more susceptible to HIV infection -

Activation of infected T-cells induces virus replication


Neopterin in HIV-1 infection

Wirleitner B, et al. Institute of Medical Chemistry and Biochemistry, Medical University of Innsbruck, Innsbruck, Austria
(Mol Immunol 2005; 42: 183-94)

Neopterin is well established as a reliable marker in HIV-1 infection. Neopterin concentrations measured in urine or serum indicate sensitively the course and progression of the disease as well as efficacy of anti-retroviral therapy. The main trigger for neopterin production is Th1-type cytokine interferon-gamma. During acute HIV-1 infection, enhanced formation of neopterin occurs already at a very early time point, before antibody seroconversion takes place. After this stage, neopterin concentrations in serum and urine closely correlate with virus load in the circulation of HIV-1-infected patients. Data provide evidence for an important role of immune activation and Th1-type cytokine interferon-gamma in the pathogenesis of HIV-1 infection. This review subsumes the importance of neopterin as a marker in HIV-1 infection. Further evidence is increasing, that neopterin derivatives might modulate immune response by interfering with the cellular redox balance, activating redox-sensitive transcription factors, or inducing apoptosis in specific cell types. The possible impact of neopterin derivatives and of other biochemical pathways induced by interferon-gamma such as indoleamine 2,3-dioxygenase in chronic diseases like HIV-1 infection is discussed.

The prognostic value of cellular and serologic markers in infection with human immunodeficiency virus type 1.

Fahey JL, et al. Center for Interdisciplinary Research in Immunology and Disease, University of California, Los Angeles 90024-1747, USA

(N Engl J Med 1990; 322: 166-72)

We evaluated three cellular and five serologic markers that are affected by infection with the human immunodeficiency virus type 1 (HIV-1) for their ability to predict the progression to clinical acquired immunodeficiency syndrome (AIDS). The cellular markers were the number of CD4+ T cells, the number of CD8+ T cells, and the ratio of CD4+ T cells to CD8+ T cells. The serologic markers were the serum levels of neopterin (a product of stimulated macrophages), beta 2-microglobulin, soluble interleukin-2 receptors, IgA, and HIV p24 antigen. We evaluated the usefulness of these measures as markers of the progression to AIDS prospectively, over four years, in a cohort of 395 HIV-seropositive homosexual men who were initially free of AIDS. CD4+ T cells (expressed as an absolute number, a percentage of lymphocytes, or a ratio of CD4+ to CD8+ T cells) were the best single predictor of the progression to AIDS, but the serum neopterin and beta 2-microglobulin levels each had nearly as much predictive power. The neopterin level appeared to be a slightly better predictor than the beta 2-microglobulin level. The levels of IgA, interleukin-2 receptors, and p24 antigen had less predictive value. A stepwise multivariate analysis indicated that the best predictors, in descending order, were CD4+ T cells (the percentage of lymphocytes or the CD4+: CD8+ ratio), the serum level of neopterin or beta 2-microglobulin, the level of IgA, that of interleukin-2 receptors, and that of p24 antigen. The last three markers had little additional predictive power beyond that of the first two. We conclude that of the eight markers studied, progression to AIDS was predicted most accurately by the level of CD4+ T cells in combination with the serum level of either neopterin or beta 2-microglobulin. At least one of these two serum markers, which reflect immune activation, should be used along with measurement of CD4+ T cells in disease-classification schemes and in the evaluation of responses to therapy.

Immunologic markers of progression to acquired immunodeficiency syndrome are time-dependent and illness-specific

Kramer A, et al. Viral Epidemiology Branch, National Cancer Institute, Rockville, MD 20892, USA
(Am J Epidemiol 1992; 136: 71-80)

Since prevalent cohorts may be biased by the duration of human immunodeficiency virus (HIV) infection (onset bias), it is useful to assess the potential predictive value of markers in incident cohorts of HIV-positive subjects for whom the date of seroconversion is known or can reliably be estimated. Of 131 homosexual men with HIV-1 seroconversion from New York City and Washington, DC, who were evaluated annually beginning in 1982, 60 developed acquired immunodeficiency syndrome (AIDS) by the end of 1989. The prognostic significance of immunologic markers (proportion of CD4+ T-lymphocytes, neopterin, beta 2-microglobulin, serum interferon, and anti-p24 antibody) and of a virologic marker (HIV p24 antigen) was determined using measurements made at defined time intervals after the known or estimated date of HIV seroconversion. When measurements made 3 years after seroconversion were used, all markers except anti-p24 antibody were found to be significant estimators of AIDS risk in univariate analyses. In multivariate Cox regression modeling, the maximum information was obtained by including neopterin, interferon, and the CD4+ T-lymphocyte proportion. The predictive value of markers after HIV seroconversion could change considerably from one interval to another. Elevated levels of beta 2-microglobulin and neopterin significantly predicted the development of Kaposi's sarcoma. These two markers were highly correlated (r = 0.74). The authors conclude that immunologic markers can be important for an HIV staging system for estimating prognosis and facilitating early therapeutic intervention in HIV-positive patients.

Markers for disease progression in intravenous drug users infected with HIV-1

Zangerle R, et al. Department of Dermatology and Venerology, University of Innsbruck, Austria
(AIDS 1991; 5: 985-91)

We evaluated the number and percentage of CD4+ T cells, the ratio of CD4+ T cells to CD8+ T cells, the serum levels of beta 2- microglobulin and urinary levels of neopterin for their ability to predict disease progression (defined as clinical AIDS and/or oral candidiasis in combination with a CD4+ T cell count less than 400 x 10(6)/l). Thirty-eight intravenous drug users (IVDU) infected with HIV-1 without HIV-1-related symptoms were followed for a median observation period of 45 months. Cumulative incidence of disease progression was computed by the product-limit approach. The CD4+: CD8+ T-cell ratio (P = 0.001), the number (P = 0.002) and percentage (P = 0.05) of CD4+ T cells, and urinary neopterin (P = 0.007) were significant predictors for disease progression. Serum beta 2-microglobulin, which has been found to be of similar prognostic value as neopterin in homosexual men, did not show predictive power in this study of IVDU. The urinary neopterin concentrations obtained at entry of the study correlated with the values of the CD4+:CD8+ T-cell ratio and number and percentage of CD4+ T cells which were obtained at the end of the follow-up. These findings should help to identify, among HIV-1-infected IVDU, those at high risk of disease progression.

Neopterin as a predictive marker for disease progression in human immunodeficiency virus type 1 infection

Fuchs D, et al. Institute of Medical Chemistry and Biochemistry, Medical University, Innsbruck, Austria
Clin Chem 1989; 35: 1746-9)

We assessed the value of urinary neopterin concentrations for prognosis of disease progression in HIV-1-infected patients. Sixty-eight anti-HIV-1 seropositive homosexuals with lymphadenopathy syndrome were tested for urinary neopterin and T-cell subset counts in 1982-83, and the incidence rate at which they developed acquired immunodeficiency syndrome (AIDS) between then and May 1988 was evaluated. Overall, 21 of 68 (30.9%) cases progressed to AIDS, with a yearly progression rate of 4-9%. The predictive value of urinary neopterin concentrations was higher (P = 0.0042) than that of CD4+ T-cell counts (P = 0.015) or the CD4+/CD8+ T-cell ratio (P = 0.022). Counts of CD8+ T-cells failed to show predictive significance (P = 0.29). Similarly, multivariate-regression analysis indicated that neopterin concentrations and CD4+ T-cell numbers were significant copredictors. Produced by human macrophages activated by interferon gamma, neopterin is thus a marker of macrophage activation via T cells. We conclude that these data demonstrate a correlation between the amount of T-cell-macrophage activation, as measured by urinary neopterin concentrations, and the progression of the disease.

Serum neopterin, an immune activation marker, independently predicts disease progression in advanced HIV-1 infection

Mildvan D, et al. Beth Israel Medical Center, New York, NY, 10003, USA
(Clin Infect Dis 2005; 40: 853-8)
Background. CD4(+) T lymphocyte (CD4) counts and plasma human immunodeficiency virus (HIV) type 1 RNA concentrations predict clinical outcome in HIV-1 infection. Our objective was to assess the independent prognostic value for disease progression of soluble markers of immune system activation.Methods. This retrospective marker-validation study utilized previously obtained clinical and laboratory data, including CD4(+) cell counts, and made use of stored frozen serum samples to assay for levels of beta (2)-microglobulin, neopterin, endogenous interferon, triglycerides, interleukin-6, soluble tumor necrosis factor- alpha receptor II, and HIV-1 RNA, and to determine HIV genotypic reverse-transcriptase inhibitor resistance. The 152 patients who participated in this study represented a subsample of participants in AIDS Clinical Trials Group (ACTG) 116B/117, a randomized trial that demonstrated the clinical benefit of didanosine over zidovudine monotherapy in persons with advanced HIV-1 infection. Marker data were analyzed in relation to protocol-defined clinical disease progression, using Cox proportional hazards models.Results. The median duration of follow-up was 344 days. Elevated baseline values for neopterin (P<0.001), endogenous interferon (P<0.001) and interleukin-6 (P=.0007) were each associated with greater subsequent risk of clinical disease progression. In a head-to-head comparison that was adjusted for CD4(+) cell count (P=0.02) and HIV-1 RNA level (P=n.s.), we found that elevated values for neopterin (P<0.001) and, to a lesser extent, endogenous interferon (P<0.01) were the strongest predictors of increased risk of clinical disease progression 6 months later.Conclusions. Soluble markers of immune activation add prognostic information to CD4 counts and viral load for risk of disease progression in advanced HIV-1 infection. The robust performance of neopterin, an inexpensive and reliably measured serum marker, supports its potential suitability for patient monitoring, particularly in resource-limited settings.