Immunological markers of disease progression in patients infected with the human immunodeficiency virus

Utility of Serum Neopterin and Serum IL-2 Receptor Levels to Predict Absolute CD4 T Lymphocyte Count in HIV Infected Cases

A prospective study was carried out to evaluate the efficacy of serum neopterin and soluble IL-2 receptor (sIL-2R) concentrations in comparison to CD4 count to study the progression of HIV disease and monitor response to ART in HIV cases. One hundred newly diagnosed HIV seropositive subjects were recruited. CD4 counts were determined by FACS system. Serum neopterin and sIL-2R levels were measured using enzyme immunoassay. In our study, levels of neopterin and sIL-2R were significantly higher in subjects with CD4 <200 cells/ μ L (with S. neopterin levels of >25.1 nmol/L and sIL-2R levels of >47.1 pM as cutoff values for CD4 <200 cells/ μ L) compared to those in subjects with CD4 >200 cells/ μ L at baseline which indicate that these markers can be utilized for initiation of ART in HIV cases. The levels of these markers decreased significantly after initiation of ART. In patients with CD4 >200 cells/ μ L, these markers are helpful in predicting disease progression.

Total lymphocyte count as a surrogate marker for CD4 count in resource-limited settings

BACKGROUND

CD4 testing is the recognized gold standard used to stage HIV/AIDS, guide treatment decisions for HIV-infected persons and evaluate effectiveness of therapy. The need for a less expensive surrogate marker that can be used in resource-limited setting is however necessary. The study sought to assess the suitability of Total lymphocyte count (TLC) as a surrogate marker for CD4 count in resource-limited localities in Ghana.

METHODS

This observational study was conducted at the Central Regional Hospital, which has one of the established antiretroviral therapy centres in Ghana. A total of one hundred and eighty-four (184) confirmed HIV I seropositive subjects were included in the study. Blood samples were taken from all the subjects for estimation of CD4 and total lymphocyte counts. The study subjects were further categorised into three (3) groups according to the Centers for Disease Control and Prevention (CDC) classification criteria as follows: CD4 counts (1) ≥ 500 cells/mm3 (2) 200-499 cells/mm3 and (3) <200 cells/mm3. Positive predictive value (PPV), negative predictive value (NPV), sensitivity and specificity of various TLC cut-offs were computed for three groups. Correlation and Receiver Operator Characteristic analysis was performed for the various CD4 counts and their corresponding Total Lymphocyte count obtained.

RESULTS

The sensitivity, specificity, positive and negative predictive values of TLC 1200 cells/ mm3 to predict CD4 count were <200 cells/mm3 72.2%, 100%, 100% and 95.7% respectively. A TLC of 1500 cells/ mm3 was found to have maximal sensitivity (96.67%), specificity (100%), PPV (100%) and NPV (75.0%) for predicting a CD4 cell count of 200-499 cell/mm3. A TLC of 1900 cells/mm3 was also found to have a maximal sensitivity (98.45%), specificity (100%), PPV (100%) and NPV (100%) for predicting CD4 count ≥500 cells/mm3. A positive correlation was noted between 184 paired CD4 and TLC counts (r = 0.5728).

CONCLUSION

Total Lymphocyte count can therefore adequately serve as a surrogate marker for CD4 count in HIV patients who are naïve for antiretroviral therapy in resource-limited areas.

PPARα and PPARγ protect against HIV-1-induced MMP-9 overexpression via caveolae-associated ERK and Akt signaling

Activation of matrix metalloproteinase-9 (MMP-9) is involved in HIV-1-induced disruption of the blood-brain barrier (BBB). In the present study, we hypothesize that peroxisome proliferator-activated receptor (PPAR)-α or PPARγ can protect against HIV-1-induced MMP-9 overexpression in brain endothelial cells (hCMEC cell line) by attenuating cellular oxidative stress and down-regulation of caveolae-associated redox signaling. Exposure to HIV-1-infected monocytes induced phosphorylation of ERK1/2 and Akt in hCMEC by 2.5- and 3.6-fold, respectively; however, these effects were attenuated by overexpression of PPARα or PPARγ and by silencing of caveolin-1 (cav-1). Coculture of hCMEC with HIV-1-infected monocytes significantly induced MMP-9 promoter and enzyme activity by 3- to 3.5-fold. Promoter mutation studies indicated that SP-1 (g1940t_g1941t) is an essential transcription factor involved in induction of MMP-9 promoter by HIV-1. In addition, HIV-1-stimulated activity of MMP-9 promoter was inhibited by mutation of AP-1 site 2 (c1918t_a1919g) and both (but not individual) NF-κB binding sites (g1389c and g1664c). PPAR overexpression, ERK1/2 or Akt inhibition, and silencing of cav-1 all effectively protected against HIV-1-induced MMP-9 promoter activity, indicating a close relationship among HIV-1-induced cerebrovascular toxicity, redox-regulated mechanisms, and functional caveolae. Such a link was further confirmed in MMP-9-deficient mice exposed to PPARα or PPARγ agonist and injected with the HIV-1-specific protein Tat into cerebral vasculature. Overall, our results indicate that ERK1/2, Akt, and cav-1 are involved in the regulatory mechanisms of PPAR-mediated protection against HIV-1-induced MMP-9 expression in brain endothelial cells.

HIV-1-induced amyloid beta accumulation in brain endothelial cells is attenuated by simvastatin

HIV-1-infected brains are characterized by increased amyloid deposition. To study the influence of HIV-1 on amyloid beta (Abeta) homeostasis at the blood-brain barrier (BBB) level, we employed a model of brain microvascular endothelial cells exposed to HIV-1 in the presence or absence of Abeta. HIV-1 markedly increased endogenous Abeta levels and elevated accumulation of exogenous Abeta. Simvastatin, the HMG-CoA reductase inhibitor, blocked these effects. We next evaluated the effects of HIV-1 and/or simvastatin on expression of the receptor for lipoprotein related protein (LRP1) and the receptor for advanced glycation end products (RAGE), known to regulate Abeta transport across the BBB. LRP1 expression was not affected by HIV-1; however, it was increased by simvastatin. Importantly, simvastatin attenuated HIV-1-induced RAGE expression. These results suggest that HIV-1 may directly contribute to Abeta accumulation at the BBB level. In addition, statins may protect against increased Abeta levels associated with HIV-1 infection in the brain.

PPARalpha and PPARgamma attenuate HIV-induced dysregulation of tight junction proteins by modulations of matrix metalloproteinase and proteasome activities

The blood-brain barrier (BBB) plays an important role in HIV trafficking into the brain and the development of the central nervous system complications in HIV infection. Tight junctions are the main structural and functional elements that regulate the BBB integrity. Exposure of human brain microvascular endothelial cells (hCMEC/D3 cell line) to HIV-infected monocytes resulted in decreased expression of tight junction proteins, such as junctional adhesion molecule-A (JAM)-A, occludin, and zonula occludens (ZO)-1. Control experiments involved exposure to uninfected monocytes. Alterations of tight junction protein expression were associated with increased endothelial permeability and elevated transendothelial migration of HIV-infected monocytes across an in vitro model of the BBB. Notably, overexpression of the peroxisome proliferator-activated receptor (PPAR)alpha or PPARgamma attenuated HIV-mediated dysregulation of tight junction proteins. With the use of exogenous PPARgamma agonists and silencing of PPARalpha or PPARgamma, these protective effects were connected to down-regulation of matrix metalloproteinase (MMP) and proteasome activities. Indeed, the HIV-induced decrease in the expression of JAM-A and occludin was restored by inhibition of MMP activity. Moreover, both MMP and proteasome inhibitors attenuated HIV-mediated altered expression of ZO-1. The present data indicate that down-regulation of MMP and proteasome activities constitutes a novel mechanism of PPAR-induced protections against HIV-induced disruption of brain endothelial cells.

Use of surrogate markers to predict the HIV disease stage and time to initiate antiretroviral therapy in developing countries

CD4 counting is the standard method for determining eligibility for antiretroviral therapy (ART) and HIV disease progression, but it is not widely available in developing countries. The aim of this study was to correlate the levels of beta-2 microglobulin and total lymphocyte count (TLC) with CD4 counts for monitoring disease progression and identify patients who require ART. The authors measured CD4 T-cell counts, TLC, and beta-2 microglobulin levels in 119 HIV seropositive patients. There was a significant negative correlation between CD4 counts and beta-2 microglobulin levels and significant positive correlation between TLC and CD4 counts. Taking a TLC cutoff of < or = 1600 and beta-2 microglobulin levels > or = 3.5 mg/l, the authors could identify 90.4% of patients with CD4 count < or = 200 cells/microl. These assays may allow reduction in the annual number of CD4 cell evaluation and the cost associated with monitoring the immune status of HIV-positive patients.

PPARalpha and PPARgamma effectively protect against HIV-induced inflammatory responses in brain endothelial cells

Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors which down-regulate inflammatory signaling pathways. Therefore, we hypothesized that alterations of PPAR functions can contribute to human immunodeficiency virus-1 (HIV-1)-induced dysfunction of brain endothelial cells. Indeed, treatment with HIV-1 transactivator of transcription (Tat) protein decreased PPAR transactivation in brain endothelial cells. We next stably over-expressed PPARalpha and PPARgamma in a newly developed cell line of human brain endothelial cells (hCMEC/D3 cells). Tat-induced up-regulation of inflammatory mediators, such as interleukin (IL)-1beta, tumor necrosis factor-alpha, CCL2, and E-selectin were markedly attenuated in hCMEC/D3 over-expressing PPARalpha or PPARgamma. These results were confirmed in CCL2 and E-selectin promoter activity studies. Similar protective effects were observed in hCMEC/D3 after activation of PPARgamma by exogenous PPAR agonists (dPGJ(2) and rosiglitazone). PPAR over-expression also prevented Tat-induced binding activity and transactivation of nuclear factor-kappaB. Importantly, increased PPAR activity attenuated induction of IL-1beta, tumor necrosis factor-alpha, CCL2, and E-selectin in hCMEC/D3 cells co-cultured with HIV-1-infected Jurkat cells. The protective effects of PPAR over-expression were reversed by the antagonists of PPARalpha (MK886) or PPARgamma (GW9662). The present data suggest that targeting PPAR signaling may provide a novel therapeutic approach to attenuate HIV-1-induced local inflammatory responses in brain endothelial cells.

Adenosine deaminase activity in cats infected with feline immunodeficiency virus

Adenosine deaminase (ADA), an enzyme involved in purine metabolism, has been shown to be of clinical importance in several diseases in humans. To investigate whether ADA is of any clinical significance in cats, plasma adenosine deaminase (P-ADA) and T cell adenosine deaminase (T-ADA) activities were measured in feline immunodeficiency virus (FIV) negative and positive cats. The AIDS-related complex (ARC) group showed a significant elevation in P-ADA activity compared to the asymptomatic carrier (AC), and FIV-negative groups (P<0.005). T-ADA activity was significantly elevated in FIV-positive cats compared to the FIV-negative group (P<0.05) and this elevation was attributed to the increase in the ARC group (P<0.01). A correlation was found between P-ADA and T-ADA activities in the FIV-negative group. T-ADA activity and CD4(+)cell number showed a strong negative correlation in FIV-positive cats (P<0.0005). CD4(+) cell numbers were significantly reduced in the ARC group compared to the healthy controls (P<0.005). Our results showed that T-ADA is increased in FIV-positive cats during the ARC stage. These results also suggest that ADA may be an indicator of T cell activation in the ARC stage of FIV infection.

Salivary immunoglobulin A antibodies to gp41 in human immunodeficiency virus-seropositive patients: lack of correlation with disease progression

Mucous membranes are the main route of transmission of human immunodeficiency virus (HIV). Interestingly, some viral inhibitory activities have been found in saliva. The purpose of this study was to determine the level of salivary immunoglobulin A (IgA) antibodies to gp41 in HIV+ patients at various disease stages to identify whether gp41 was able to induce vigorous humoral responses. Unstimulated saliva samples were obtained from three groups of subjects (n=37): group A (HIV-), group B (HIV+, CD4+ <200/mm3), and group C (HIV+, CD4+ >200/mm3). IgA antibody levels to purified gp41 were determined by enzyme-linked immunosorbent assay (ELISA). Western blot analyses were performed using HIV+ saliva to confirm IgA reactivity to gp41. ELISA demonstrated that HIV+ subjects had higher IgA antibody to gp41 than HIV- individuals. No significant differences were noted between HIV+, CD4+ <200/mm3 and CD4+ >200/mm3 subjects. High (81.25%) IgA reactivity to gp41 was demonstrated by Western blotting of saliva from all HIV+ individuals. In conclusion, gp41 responses are important in the HIV disease process, as indicated by the high IgA levels and gp41 reactivity in saliva of HIV+ patients.