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High Viral Load (high + viral_load)

Distribution by Scientific Domains

Medical Sciences	89%

Distribution within Medical Sciences

Hepatology	52%
Infectious Disease	11%

Selected Abstracts

Oral candidiasis as a clinical marker related to viral load, CD4 lymphocyte count and CD4 lymphocyte percentage in HIV-infected patients

JOURNAL OF ORAL PATHOLOGY & MEDICINE, Issue 1 2002
J. Campo
Abstract Background:, High viral load is currently considered to be one of the main indicators of the progression of HIV-induced immunodepression, but few studies have analysed its relationship to the presence of oral candidiasis (OC). The aim of this cross-sectional study is to analyse the relationship between viral load, total CD4 lymphocyte count, and percentage of CD4 lymphocytes to the occurrence of OC. Methods:, The present cross-sectional study included 156 HIV-infected patients seen at a clinic for sexually transmitted diseases and HIV. We assesed the presence or absence of OC, and microbiological samples were obtained from the palatine mucosa and dorsal tongue for a smear stained with KOH (potassium hydroxide) and culture on Sabouraud's dextrose agar in all patients. Viral load was determined by quantification of viral RNA in peripheral blood with a minimum detectable level of 500 RNA copies/ml. CD4+ counts/CD4+ percentage were categorized as <200/<14%, 200,499/14,28%, and >500/>29%, and HIV viral loads were categorized as <500, 500,10,000, >10,000 copies/ml. Results:, Thirty-eight percent (37.8%) of the patients had OC. Patients with CD4+ lymphocyte counts below 200×106/l and CD4+ percentages below 14% showed a significantly higher frequency of OC (57.9% and 48.0%, respectively). Patients with a viral load over 10,000 copies/ml also had OC more frequently (44.8%). In the multiple logistic regression analysis, OC showed a statistically significant association with high viral load [>10,000 vs <500, odds ratio (OR)=11.4], low percentage of CD4+ lymphocytes (<14% vs >28%, OR=5), and injection drug use (IDU vs heterosexual transmission, OR=10.2). In HIV-infected patients, high viral load was associated with more frequent OC, regardless of CD4+ lymphocyte level. Conclusions:, These findings suggest that oral candidiasis could be a useful clinical marker of patients with high viral load. In view of these results, emphasis should be placed on the importance of systematic examination of the oral cavity in all medical follow-up examinations of HIV-infected patients. [source]

Hepatitis B viral load predicts survival of HCC patients undergoing systemic chemotherapy,

HEPATOLOGY, Issue 6 2007
Winnie Yeo
HCC is a common cause of morbidity and mortality. For patients who are not candidates for curative surgery, systemic chemotherapy is one of the standard treatments. In parts of China and the Far East, over 80% of HCC patients have chronic HBV infection. In this study, we aimed to assess the relationship between pre-chemotherapy HBV viral load and the survival of HCC patients. HBV infection status was determined prior to chemotherapy in 188 patients, 170 of whom had evidence of HBV chronic infection/exposure (160 hepatitis B surface antigen [HBsAg]-positive, 10 HBsAg-negative/hepatitis B core antibody,positive). Of these, 125 had pretreatment HBV DNA levels determined via real-time PCR. Virological data were analyzed using conventional clinical variables to identify factors that influenced survival. Multivariate analysis revealed that high total bilirubin (P = 0.0016; hazard ratio = 1.040 per 1 ,M increase; 95% CI 1.015,1.065), HCV infection (P = 0.0095; hazard ratio = 6.955; 95% CI 1.606,30.129), and high HBV DNA level (P = 0.0217; hazard ratio = 1.650; 95% CI 1.076,2.531) affected survival significantly. Exploratory analysis revealed that high levels of pretreatment HBV DNA had a significantly higher incidence of severe hepatitis during chemotherapy. Conclusion: For HCC patients with HBV chronic infection/exposure, a high viral load prior to treatment is an adverse factor for survival and may be associated with a higher incidence of severe hepatitis during chemotherapy. Future strategies to improve the prognosis of HCC patients undergoing chemotherapy should consider supportive therapy that incorporates antiviral therapies to reduce HBV viral load. (HEPATOLOGY 2007;45:1382,1389.) [source]

High-dose ribavirin in combination with standard dose peginterferon for treatment of patients with chronic hepatitis C,

HEPATOLOGY, Issue 2 2005
Karin Lindahl
Improved treatment regimens for patients with chronic hepatitis C, genotype 1 and high viral load are needed. Increasing the dose of ribavirin has increased the response rate, but experience with doses of more than 1,200 mg/day is limited. The aim of this study was to investigate the safety and tolerance to treatment with a high and individualized dose of ribavirin in combination with peginterferon. Ten patients with chronic hepatitis C, genotype 1 and high viral load were treated with peginterferon alfa-2a and ribavirin for 48 weeks in a prospective trial. The initial ribavirin dose was individualized and calculated from a pharmacokinetic formula based mainly on renal function. Ribavirin plasma concentrations were monitored, and the dose was adjusted to reach the target concentration. Hemoglobin was monitored, and patients were treated with erythropoietin and blood transfusions when indicated. After dose adjustments, the mean dose of ribavirin was 2,540 mg/day (range, 1,600-3,600) at week 24. The main side effect was anemia, which was controlled with erythropoietin. Two patients required blood transfusions. One patient was withdrawn at week 24 because of a lack of viral response, and one patient at week 39 because of side effects, primarily interferon associated. At follow-up (,24 weeks posttreatment), nine of ten patients had undetectable HCV RNA and thus were cured by standard definitions. In conclusion, a high dose of ribavirin according to an individualized schedule is feasible but associated with more frequent and serious side effects such as anemia. The viral response merits further evaluation. (HEPATOLOGY 2005;41:275,279.) [source]

Treatment with pegylated interferon and ribavarin in HCV infection with genotype 2 or 3 for 14 weeks: A pilot study

HEPATOLOGY, Issue 6 2004
Olav Dalgard
The aim of this study was to determine the efficacy of 14 weeks of treatment in patients infected with hepatitis C virus (HCV) genotype 2 or 3 who achieve early virological response (EVR). In a noncontrolled multicenter trial, 122 treatment-naive patients received 1.5 ,g/kg pegylated interferon alfa-2b subcutaneously once weekly and 800 to 1,400 mg/d ribavirin based on body weight. Treatment was stopped at week 14 in patients with EVR, defined as undetectable HCV RNA at weeks 4 and 8. Patients without EVR were assigned to 24 weeks of treatment. The primary end point was sustained virological response (SVR), defined as undetectable HCV RNA 24 weeks after end of treatment. Among the 122 patients, 95 (78%) had EVR and received 14 weeks of treatment. The remaining 27 (22%) were treated for 24 weeks. SVR was obtained in 85 (90%) of 95 patients in the 14-week treatment group and 15 of (56%) 27 in the 24-week treatment group. Altogether, SVR was obtained in 100 of 122 patients (82%; 95% CI, 75%-89%). SVR after 14 weeks of treatment was achieved more frequently among genotype 3a patients with low viral load compared with high viral load (98% vs. 79%; P = .019). Logistic regression analysis showed that absence of bridging fibrosis/cirrhosis was the only independent predictor of SVR. In conclusion, patients with genotype 2 or 3 and EVR obtained a high SVR after 14 weeks of treatment. The results need to be confirmed in a randomized, controlled study before this treatment approach can be recommended, particularly for patients with genotype 3 and high viral load or severe fibrosis. (HEPATOLOGY 2004;40: 1260,1265.) [source]

Rapid loss of hepatitis C virus genotype 1b from serum in patients receiving a triple treatment with telaprevir (MP-424), pegylated interferon and ribavirin for 12 weeks

HEPATOLOGY RESEARCH, Issue 11 2009
Fumitaka Suzuki
Aim:, To evaluate the efficacy and safety of the triple treatment with telaprevir (MP-424), pegylated interferon (PEG-IFN) and ribavirin during 12 weeks on-treatment. Methods:, The triple treatment was given to 20 patients with chronic hepatitis C who had been infected with hepatitis C virus (HCV)-1b in high viral load (median: 6.8 log IU/mL [range: 5.5,7.2]), with a median age of 54 years (range: 36,65 years). They were followed for early dynamics of HCV RNA in serum during 12 weeks and side-effects. Results:, HCV RNA levels decreased by 4.8 logs by 7 days and 5.5 logs by 14 days. HCV RNA disappeared in 50% (10/20) at 2 weeks, 79% (15/19) at 4 weeks, 88% (14/16) at 6 weeks, 94% (15/16) at 8 weeks and 100% (13/13) at 12 weeks. HCV RNA disappeared equally frequently in 10 treatment-naive patients, six non-responders to IFN monotherapy and four non-responders to PEG-IFN and ribavirin. It was no different in the patients with and without amino acid substitutions reducing the response to IFN. The treatment was withdrawn in seven (35%) patients, mostly due to reduced hemoglobin of less than 8.5 g/dL, of whom six (86%) remained clear of HCV RNA at 12 weeks. Conclusion:, HCV RNA was lost from serum rapidly and universally in patients infected with HCV-1b in high viral loads by the triple treatment. Because an early loss of HCV RNA correlates with high rates of sustained virological response (SVR), it would increase SVR substantially, and merit the patients who have not responded to previous therapies. [source]

Predicting the response to 48-week combination therapy with peginterferon ,-2b plus ribavirin from the estimated HCV RNA load index after negative serum change in genotype 1b hepatitis C patients

HEPATOLOGY RESEARCH, Issue 6 2009
Keiji Tsuji
Aim:, We estimated viral dynamics after serum hepatitis C virus (HCV) RNA became negative and assessed the relation between the estimated viral load at the end of treatment (EVE) index and the response to the combination therapy with peginterferon ,-2b plus ribavirin. Methods:, Patients with chronic HCV, genotype 1b, and a high viral load were treated with this combination therapy for 48 weeks, and serum HCV RNA was measured frequently during the treatment period. In the patients showing an end-of-treatment response (ETR), the viral load profile from the start of treatment until serum HCV RNA became negative was expressed by an approximate curve. Then the EVE index was calculated by using the expression obtained from the curve, and differences between the sustained virologic response (SVR) and relapse groups were investigated. Results: The SVR rate increased as the EVE index became lower, and the EVE index was significantly lower in the SVR group than in the relapse group. The SVR rate was higher for those in whom the EVE index was below the cut-off point. Conclusion:, Prediction of SVR and relapse from the EVE index is more useful than prediction from viral dynamics at the time when HCV RNA becomes negative or when HCV RNA shows a decrease of 2-log or more. [source]

P17 Response of individuals with high viral load to non-nucleoside reverse transcriptase inhibitors

HIV MEDICINE, Issue 3 2000
M Nelson
[source]

Cross-sectional analysis of oncogenic HPV viral load and cervical intraepithelial neoplasia

INTERNATIONAL JOURNAL OF CANCER, Issue 5 2006
Roberto Flores
Abstract In human papillomavirus (HPV)-associated carcinogenesis, HPV infection characteristics such as viral load may play an important role in lesion development. The purpose of this study was to determine the association between quantitative assessment of oncogenic HPV viral load, and abnormal cytology among women residing along the United States,Mexico border. A cross-sectional study of 2,319 women was conducted between 1997 and 1998. Viral load of oncogenic HPV types (16, 18, 31, 39, 45, 51, 52, and 58) was measured among 173 HPV (+) women using quantitative real-time PCR. Overall, HPV 16, 31, 52 and 58 showed the highest viral load. Single type infection had higher viral loads compared to multiple type infections. HPV viral load declined significantly (p = 0.04) with age. No significant association was observed with other known HPV risk factors such as oral contraceptive use, parity, sexual and STD history. Viral load was independently associated with degree of cervical lesions. An adjusted odds ratio (AOR) of 4.7 for the association between increasing total viral load and Atypical Squamous Cells of Undetermined Significance (ASCUS)/Atypical Glandular Cells of Undetermined Significance (AGUS) was observed (p for trend <0.01). Increased risk of low-grade SIL was observed with higher viral load compared with HPV negative women (AOR = 47.7 for total viral load; AOR = 37.1 for HPV viral load not including HPV16, and AOR = 25.9 for HPV16 viral load). Likewise, increased risk of high-grade SIL with higher viral loads was observed (AOR = 58.4 for high total viral load compared with HPV negative women, AOR = 58.1 for HPV viral load not including HPV16, and AOR = 69.8 for HPV16 high viral load). Results from this study suggest a dose,response relationship between increasing oncogenic HPV viral load and risk of LSIL and HSIL. © 2005 Wiley-Liss, Inc. [source]

Oral candidiasis as a clinical marker related to viral load, CD4 lymphocyte count and CD4 lymphocyte percentage in HIV-infected patients

Retreatment with interferon and ribavirin vs interferon alone according to viraemia in interferon responder-relapser hepatitis C patients: a prospective multicentre randomized controlled study

JOURNAL OF VIRAL HEPATITIS, Issue 3 2003
I. Portal
Summary., Low pretreatment viral load has consistently been shown to be an independent predictor of sustained response (SR) in patients with chronic hepatitis C infection. We assessed the efficacy of interferon (IFN) plus ribavirin vs IFN alone in low viraemic patients (<2 millions copies/mL) who had relapsed to a previous course of IFN and the efficacy of 24 vs 48 week combination therapy in high viraemic patients. Two hundred and ninety-seven patients were randomly assigned to one of the four regimens after stratification on pretreatment viral load. All patients received IFN- ,2b (6 million units thrice weekly for 24 weeks and 3 million units thrice weekly for 24 weeks). Patients with low viraemia received either IFN- ,2b alone for 48 weeks (R1: 42 patients) or IFN- ,2b plus ribavirin (600 mg/day) for 24 weeks and IFN- ,2b alone for the next 24 weeks (R2: 48 patients). Patients with high viral load received either IFN- ,2b plus ribavirin for 24 weeks and then IFN- ,2b alone for the next 24 weeks (R3: 104 patients) or IFN- ,2b plus ribavirin for 48 weeks (R4: 103 patients). In low viraemic patients the rate of SR was 37.7% in group R1 and 59.6% in group R2 (P < 0.05). In high viraemic patients, the rate of SR was 44.7% in group R3 and 51.4% in group R4 (P: NS). Thirty-one patients discontinued treatment (10.4%) without difference regarding treatment regimen. In the regimen using ribavirin we found no difference in terms of SR between patients receiving a dose of ribavirin below 10.6 mg/kg/day (55%) or over 10.6 mg/kg/day (58%). Histological improvement occurred in 70.2% of patients regardless of the regimen. Logistic regression showed that genotype 2 and 3, Knodell score <6 and alanine aminotransferase pretreatment level >3 × upper limit of normal were significantly and independently correlated with SR. In low viraemic patients who relapsed to a previous IFN treatment, combination therapy using high-dose IFN and low-dose ribavirin is better than high-dose IFN alone. In high viraemic patients there was no benefit in increasing the duration of combination therapy from 24 to 48 weeks. In this study, it was found that low dose of ribavirin can be used safely and there is no effect of ribavirin dose on SR. [source]

A prospective study of interferon therapy modified by pre-treatment viral load in cirrhotic patients

LIVER INTERNATIONAL, Issue 4 2000
Yasushi Shiratori
Abstract:Background/Aims: The relative role of hepatitis C virus (HCV) load and subtype as predictors of the efficacy of interferon therapy has been clarified in patients with chronic hepatitis C, but the effectiveness of interferon therapy in cirrhotic patients is still unclear. Methods: To resolve this issue, we undertook a multicenter, randomized, and prospective study of 114 cirrhotic patients with hepatitis C virus infection. The patients were selected to undergo two different periods (6 or 12 months) of IFN therapy according to viral load. Patients with "low" viral load (,105.8 copies/ml serum) were randomly divided into three groups, receiving 6 or 9 million units (MU) interferon three times a week for 6 months (total dose: 468 or 702 MU), or of a modified regimen using 6MU of IFN over 6 months (total dose 564 MU), while patients with "high" viral load (,106.3 copies/ml serum) were also randomly divided into two groups of 6 or 9 MU of IFN three times a week for 12 months (total dose: 936 or 1404 MU). Results: HCV-RNA negativity rate at the completion of treatment with 6 or 9 MU IFN was 65% in patients with "low" viral load, in contrast to 14% in patients with "high" viral load. Sustained virological response was found in 40% of patients with "low" viral load irrespective of the three different regimens, in contrast to only 1 out of 35 patients (3%) with "high" viral load. Viral eradication was found in approximately 50% of patients having a low virus load (,104.3 copies/ml) and with HCV subtype 2a. Univariate and multivariate analysis revealed that pretreatment viral load was a significant factor contributing to efficacy of IFN therapy. Conclusions: Sustained response was scarcely achieved in cirrhotic patients with high viral loads even after a 12-month course of intensive IFN therapy. This result indicates that there is a certain cut-off level of HCV RNA load which can not be eradicated. [source]

Prophylaxis Against Hepatitis B Recurrence Posttransplantation Using Lamivudine and Individualized Low-Dose Hepatitis B Immunoglobulin

AMERICAN JOURNAL OF TRANSPLANTATION, Issue 8 2010
L. Jiang
Although the combination of lamivudine (LAM) and high-dose intravenous (IV) hepatitis B immunoglobulin (HBIG) is very effective in preventing hepatitis B virus (HBV) recurrence after liver transplantation (LT), the major limitation of this regimen is its high cost. A more cost-effective, convenient and widely accepted regimen is urgently needed. We evaluated the safety and efficacy of another strategy using LAM and individualized low-dose intramuscular (IM) HBIG. Between May 2002 and December 2009, a total of 254 adult patients undergoing LT for HBV-related benign end-stage liver diseases received this regimen in our center. The mean follow-up of these patients was 41.2 ± 22.7 months. Their 1-, 3- and 5-year survival rates were 85.3%, 77.4% and 76.4%, respectively, and 1-, 3- and 5-year HBV recurrence rates were 2.3%, 6.2% and 8.2%. Fourteen patients experienced posttransplant HBV recurrence. Pretransplant high viral load and posttransplant prednisone withdrawal time were observed to be associated with recurrence. In conclusion, combination therapy with LAM and individualized low-dose IM HBIG provides a safe and effective prophylaxis against HBV recurrence after LT at about 5% of the cost of conventional high-dose IV HBIG regimens. [source]

An autopsy case of late-onset Epstein,Barr virus associated post-transplant lymphoproliferative disorders 11 yr after kidney transplantation

CLINICAL TRANSPLANTATION, Issue 2008
Kumi Aita
Abstract:, A 42-yr-old Japanese female presented with right cervical lymphadenopathy. She had been diagnosed with IgA glomerulonephritis at the age of 19 and had a one-yr history of hemodialysis after giving birth to her first child. At the age of 31, she had a living-related renal transplantation from her mother. On admission, she was diagnosed with diffuse large B-cell lymphoma (DLBL) by lymph node biopsy and was treated with Rituxymab plus CHOP (Rituximab/Cyclophosphamide/Doxorubicin/Vincristine/Prednisone). However, the therapy was not successful, and the patient had a rapidly deteriorating clinical course with elevated Epstein,Barr virus (EBV) loads in her peripheral blood. She died four months after the onset of lymphoma, because of disseminated intravascular coagulation and multiple organ failure. In kidney transplantation, the incidence of post-transplant lymphoproliferative disorders (PTLD) is between 0.4% and 2% and mostly occurs within a year after transplantation, in strong association with EBV infection. Late-onset PTLD, however, is more like standard lymphomas and is rarely induced by EBV. The present case was quite atypical of late-onset PTLD because the patient's high viral load was first detected 11 yr after transplantation and presented as a monomorphic B-cell lymphoma. [source]

Rapid loss of hepatitis C virus genotype 1b from serum in patients receiving a triple treatment with telaprevir (MP-424), pegylated interferon and ribavirin for 12 weeks

Efficacy of low dose long-term interferon monotherapy in aged patients with chronic hepatitis C genotype 1 and its relation to alpha-fetoprotein: A pilot study

HEPATOLOGY RESEARCH, Issue 7 2007
Hideyuki Nomura
Aim:, The objective of this study was to examine the efficacy and safety of low dose long-term interferon (IFN) therapy in aged patients with chronic hepatitis C genotype 1. Methods:, The IFN therapy was performed in Shin-Kokura Hospital on 44 patients aged 60 or older with chronic hepatitis C. All patients had high viral loads of genotype 1. Three million units of natural IFN-, was administered intramuscularly or intrasubcutaneously, three times a week for three years. A control group of 44 subjects not treated with IFN, matched for age, gender and hepatic histology, was formed. Results:, Two of the 44 patients showed a sustained virological response. Alanine aminotransferase was below the upper limit of normal in 59% (23/39) of the patients and alpha-fetoprotein was less than 40 ng/mL in 97% (38/39) on the completion of treatment. Sustained biochemical response was observed in 53% (19/36) of the patients. In the liver cirrhosis group, serum albumin values and platelet counts increased in 38% (6/16) and 33% (6/18) of patients, respectively. Hepatocellular carcinoma (HCC) appeared in three patients by 13 months after the start of treatment, but no cases were reported thereafter. The cumulative non-carcinogenesis rate of HCC in the liver cirrhosis group was significantly higher in the IFN treatment group compared to the control group (log,rank test, P = 0.046). Conclusion:, Low dose long-term interferon monotherapy to prevent carcinogenesis of HCC was considered useful in aged patients for whom peg-interferon and ribavirin combination therapy is difficult. [source]

Gene expression profiling of gut mucosa and mesenteric lymph nodes in simian immunodeficiency virus-infected macaques with divergent disease course

JOURNAL OF MEDICAL PRIMATOLOGY, Issue 4-5 2006
M.D. George
Abstract Background, Although the majority of drug-naïve HIV-infected patients develop acquired immunodeficiency syndrome (AIDS), a small percentage remains asymptomatic without therapeutic intervention. Methods, We have utilized the simian immunodeficiency virus (SIV)-infected rhesus macaque model to gain insights into the molecular mechanisms of long-term protection against simian AIDS. Results, Chronically SIV-infected macaques with disease progression had high viral loads and CD4+ T-cell depletion in mucosal tissue and peripheral blood. These animals displayed pathologic changes in gut-associated lymphoid tissue (GALT) and mesenteric lymph node that coincided with increased expression of genes associated with interferon induction, inflammation and immune activation. In contrast, the animal with long-term asymptomatic infection suppressed viral replication and maintained CD4+ T cells in both GALT and peripheral blood while decreasing expression of genes involved in inflammation and immune activation. Conclusions, Our findings suggest that reduced immune activation and effective repair and regeneration of mucosal tissues correlate with long-term survival in SIV-infected macaques. [source]

Increased detection of HBV DNA in HBsAg-positive and HBsAg-negative South African HIV/AIDS patients enrolling for highly active antiretroviral therapy at a Tertiary Hospital

JOURNAL OF MEDICAL VIROLOGY, Issue 3 2009
Azwidowi Lukhwareni
Abstract This retrospective study investigated the prevalence of hepatitis B virus (HBV) in 192 stored sera from human immunodeficiency virus (HIV) positive South African patients initiating antiretroviral therapy (ART), and explored the implications of HBV,HIV co-infection on laboratory diagnosis of HBV. HBV serology (HBsAg, anti-HBs and anti-HBc) and nested HBV PCR assays targeting the HBV polymerase gene were performed, with HBV DNA positive samples being quantified with Cobas Taqman HBV test 48 assay (Roche Diagnostics). The study found that 63% (121/192) of patients had past or present HBV infection, and 40.6% (78/192) had detectable HBV DNA. Also, 22.9% (44/192) of patients were HBsAg positive and HBV DNA positive, while 23% (34/148) of HBsAG negatives had occult HBV infections. Of the 78 HBV DNA positive samples, 62.8% had viral loads ranging from 102 to ,108 IU/ml, and 37.2% had HBV viral loads <200 IU/ml. There was a statistically significant positive association between HBsAg-positivity and high viral loads, with 27% (12/44) of HBsAg positives having HBV viral loads between 104 and ,108 IU/ml, compared to only 5.9% (2/34) of HBsAg negatives (relative risk: 4.64; 95% confidence interval: 1.11, 19.35; chi-square P -value,=,0.015). The study shows that the majority of HIV/AIDS patients initiating ART have either acute or chronic HBV infections, and further confirms that HIV remains a risk factor for occult HBV infections in South African patients as previously shown. The findings strongly support HBV screening in all HIV-positive patients initiating ART in South Africa, considering that current ART regimens include drugs with anti-HBV activity (e.g., lamivudine). J. Med. Virol. 81:406,412, 2009. © 2009 Wiley-Liss, Inc. [source]

Prevalence of X4 tropic HIV-1 variants in patients with differences in disease stage and exposure to antiretroviral therapy

JOURNAL OF MEDICAL VIROLOGY, Issue 8 2007
Eva Poveda
Abstract Viral tropism plays an important role in HIV pathogenesis. However, its correlation with the clinical outcome and following exposure to antiretroviral drugs are still unclear. HIV-1 co-receptor usage was examined in 206 infected individuals: 67 seroconverters, 52 chronically drug-naïve, and 87 antiretroviral-experienced patients. The V3 loop was sequenced from plasma HIV-RNA and co-receptor usage was inferred using a phenotype predictor software (http://genomiac2.ucsd.edu:8080/wetcat/v3.html), which classifies V3 sequences as R5 or X4. The overall prevalence of X4 viruses was 26.2%, with significant differences among groups: 13.4% in seroconverters, 25% in drug-naïve, and 36.8% in antiretroviral- experienced patients (P,=,0.001). The presence of X4 variants in the latter group was associated with higher viral load (P,=,0.002) but not with lower CD4 counts. There was no association between HIV tropism and gender, transmission route or age. Neither with the CCR5 ,32 genotype. Moreover, no association was found between HIV-1 tropism and drug resistance mutations nor with failure to regimens based on either protease inhibitors or non-nucleoside reverse transcriptase inhibitors. Finally, no significant association was found between IL-7 plasma levels with HIV-1 tropism. In summary, X4 viruses are particularly frequent among antiretroviral-experienced patients with high viral loads, irrespective of the CD4 count. Thus, CCR5 antagonists should be used with special caution in this subset of patients. J. Med. Virol. 79: 1040,1046, 2007. © 2007 Wiley-Liss, Inc. [source]