HIV-1 infection and chemokine receptor modulation

In addition to the CD4 molecule that binds to the human immunodeficiency virus type-1 (HIV-1) envelope glycoprotein gp120, productive HIV-1 infection requires interaction with cellular receptors for alpha- or beta- chemokines (CXCR4 and CCR5 respectively). Isolates of HIV-1 exhibit different tropism depending on the chemokine receptor type that they use to infect their cellular targets. HIV-1 strains that use preferentially CCR5 are known as R5 strains. They are more frequently found in asymptomatic individuals during the initial stages of the disease and are involved in the transmision of infection from mother to child. HIV-1 species using CXCR4 (X4 strains) are observed mainly in patients with advanced disease. While X4 isolates are associated with syncitium formation, in general R5 strains are not. Interaction of X4 and R5 with their specific receptors is necessary to establish productive HIV-1 infection and trigger a series of intracellular signals. Modulation of CXCR4 and CCR5 expression after HIV-1 infection is one of the results of such interaction and may have important consequences on the course of the infection. Down regulation of CCR5 and CXCR4 after HIV-1 infection could be the result of indirect events linked to HIV-1 infection, such as the induction of alpha- or beta-chemokines competing with the virions for receptor binding. They could also reflect direct effects of HIV-1 on chemokine-receptor turnover. In this review, the mechanisms of modulation of CXCR4 and CCR5 expression after HIV-1 infection will be discussed.     

Longitudinal analysis of lymphocyte ratios and HIV-1 intracellular DNA levels in children

The associations between human immunodeficiency virus type 1 (HIV-1) intracellular DNA and immunological markers were analyzed longitudinally for children with sustained, undetectable RNA levels while receiving highly active antiretroviral therapy (HAART) for >2 years. When DNA levels reached a plateau at week 104 of therapy, in contrast to findings for adults, there was no correlation between the CD4(+) : CD8(+) ratio and DNA levels (r=-0.02; P=.95), and naive CD4(+)CD45RA(+) lymphocytes predominated. These data suggest that the increased proportion of naive lymphocytes found in children are less susceptible to HIV-1 infection than are the memory lymphocytes that dominate immune reconstitution in adults.     

Roles of chemokines and chemokine receptors in HIV-1 infection

Human immunodeficiency virus type 1 (HIV-1) uses a coreceptor together with CD4 to enter CD4+ target cells. The chemokine receptors CXCR4 and CCR5 have been found to be the major coreceptors for T-cell line-tropic and macrophage-tropic HIV-1 strains, respectively, although many other chemokine and orphan receptors have also been identified as potential coreceptors for HIV-1. Genetic analyses has revealed the importance of chemokine and chemokine receptor genes in disease progression. The discovery of coreceptors provides a more defined scheme for virus entry in which the HIV-1 envelope glycoprotein sequentially binds CD4 and coreceptor, leading to a membrane fusion reaction between the viral envelope and the plasma membrane of the target cell. It also provides the basis for HIV-1 cell tropism. The identification of HIV coreceptors provides new opportunities for the development of anti-HIV therapy. Many coreceptor-based therapeutic approaches have been developed, some of which are currently in clinical trials.     

High levels of cervical HIV-1 RNA during early HIV-1 infection

Few data are available on genital tract viral replication early after HIV-1 acquisition, when infectivity is high. We compared cervical HIV-1 RNA from 60 women with paired samples from within 90 days after HIV-1 acquisition and at viral setpoint (4-24 months). Cervical HIV-1 was higher in early compared with setpoint samples (mean 3.43 versus 2.85 log10 copies/swab, P < 0.001). After adjusting for HIV-1-plasma RNA, cervical HIV-1 RNA from 30 days or less after infection was increased by 0.45 log10 copies/swab (P = 0.006).     

Elevated levels of serum perforin in chronic HIV-1 and acute SIV/SHIV infection

The impaired functional activity of cytotoxic T lymphocytes and natural killer cells during HIV-1 infection has recently been attributed to decreased intracellular levels of perforin and granzyme B. In sera from individuals chronically infected with HIV-1 we report increased levels of extracellular perforin compared with uninfected individuals. Increased perforin was also observed during experimental SIV/SHIV infection. The combination of reduced intracellular perforin levels and an increased serum level indicates that HIV infection induces aberrant perforin secretion.     

Epidemiology and predictive factors for chemokine receptor use in HIV-1 infection

BACKGROUND: CXCR4-using virus is associated with higher viral load and accelerated human immunodeficiency virus (HIV) disease progression. Additionally, CCR5 antagonists may not reduce the HIV-1 RNA load when mixed/dual-tropic or CXCR4-using virus is present. The determination of coreceptor tropism may be required before CCR5 or CXCR4 antagonists are initiated, unless reliable predictive markers of coreceptor use are established. METHODS: Samples from treatment-naive and -experienced HIV-1-positive individuals with date-matched CD4 and CD8 cell counts and HIV-1 RNA, clade, and pol sequences were assessed for coreceptor usage, by use of the ViroLogic PhenoSense assay. RESULTS: Coreceptor use determination was successful in 563 of 861 samples. Non-clade B virus was present in 18.6% of samples. CXCR4 or mixed/dual-tropic CCR5/CXCR4 virus was present in 112 of samples (19.9%). Only 4 samples (0.7%) showed exclusive CXCR4 use. In a multivariate model, higher CD4 cell count, lower viral load, and higher natural killer cell counts were significantly associated with CCR5 usage. No associations with treatment experience, clade, or pol gene mutations were observed. CONCLUSION: The prevalence of CCR5-tropic HIV-1 phenotype declines with decreasing CD4 cell count and increasing viral load. Mixed/dual tropic virus is found in all CD4 cell count and viral load strata. Coreceptor usage is not influenced by viral clade.     

Longitudinal changes in serum HBV DNA levels and predictors of progression during the natural course of HBeAg-negative chronic hepatitis B virus infection

Summary.  We evaluated the longitudinal changes of viraemia and predictors of progression in a prospectively followed cohort of 150 untreated patients with HBeAg-negative chronic hepatitis B virus (HBV) infection. According to the first year of follow-up, 85 patients were classified into inactive carrier state and 65 into chronic hepatitis B (CHB). Serum HBV DNA levels were determined at baseline in all patients, at year-1 in carriers or last pretherapy visit in CHB patients and during alanine aminotransferase (ALT) elevations in carriers progressing to CHB. HBV DNA levels at any occasion were ≥80, ≥2000 or ≥20 000 IU/mL in 81%, 23% or 0% of carriers and 100%, 95% or 83% of CHB patients. The cumulative progression rate from carrier to CHB was 11%, 16%, 24% at 2-, 3-, 4 years and was independently associated with higher baseline ALT (always within traditional normal range) and baseline HBV DNA ≥2000 or ≥5000 IU/mL. In 12 carriers progressed to CHB, HBV DNA increased by >1 log₁₀ IU/mL. During 7.5 months of median follow-up, HBV DNA change ≥1 log₁₀ IU/mL was observed in 49% of CHB patients. In conclusion, serum HBV DNA levels are detectable in the majority of inactive HBV carriers exceeding 2000 IU/mL in only 23% and 20 000 IU/mL in none of them. Carriers have approximately 15% 3-year risk of progression to CHB, which is associated with higher baseline ALT and viraemia ≥2000–5000 IU/mL, and thus should be closely followed. Approximately 20% of HBeAg-negative CHB patients have HBV DNA <20 000 IU/mL with fluctuations >1 log₁₀ occurring in many of them.     

Polymorphisms in Toll-like receptor 9 influence the clinical course of HIV-1 infection

BACKGROUND: The clinical course of HIV-1 infection is highly variable among individuals, at least in part as a result of genetic polymorphisms in the host. Toll-like receptors (TLRs) have a key role in innate immunity and mutations in the genes encoding these receptors have been associated with increased or decreased susceptibility to infections. OBJECTIVES: To determine whether single-nucleotide polymorphisms (SNPs) in TLR2-4 and TLR7-9 influenced the natural course of HIV-1 infection. METHODS: Twenty-eight SNPs in TLRs were analysed in HAART-naive HIV-positive patients from the Swiss HIV Cohort Study. The SNPs were detected using Sequenom technology. Haplotypes were inferred using an expectation-maximization algorithm. The CD4 T cell decline was calculated using a least-squares regression. Patients with a rapid CD4 cell decline, less than the 15th percentile, were defined as rapid progressors. The risk of rapid progression associated with SNPs was estimated using a logistic regression model. Other candidate risk factors included age, sex and risk groups (heterosexual, homosexual and intravenous drug use). RESULTS: Two SNPs in TLR9 (1635A/G and +1174G/A) in linkage disequilibrium were associated with the rapid progressor phenotype: for 1635A/G, odds ratio (OR), 3.9 [95% confidence interval (CI),1.7-9.2] for GA versus AA and OR, 4.7 (95% CI,1.9-12.0) for GG versus AA (P = 0.0008). CONCLUSION: Rapid progression of HIV-1 infection was associated with TLR9 polymorphisms. Because of its potential implications for intervention strategies and vaccine developments, additional epidemiological and experimental studies are needed to confirm this association.     

HBV感染者血清趋化因子IP-10和RANTES的表达及其临床意义探讨

目的探讨HBV感染者血清IP—10和RANTES水平及其临床意义。方法采用ELISA定量检测正常人、自限性HBV感染者、慢性HBV携带者和慢性乙型肝炎患者血清IP-10和RANTES水平。结果与正常人比,自限性HBV感染者、慢性HBV携带者和慢性乙型肝炎患者血清IP-10（P=0．002,P=0．002,P=0．01）和RANTES（P=0．01,P=0．02,P〈0．001）表达均明显上调;自限性HBV感染者、慢性HBV携带者和慢性乙型肝炎患者之间血清IP-10水平无显著性差异（P〉0．05）,但自限性HBV感染者血清RANTES水平较其他两组明显升高（P±0．005,P=-0．03）;慢性乙型肝炎患者血清IP-10（P=0．001）和RANTES（P=0．02）水平均明显高于慢性HBV携带者;HBeAg阴性和阳性者之间两指标无显著性差异（P=0．08,P=0．42）;HBVDNA阳性者血清IP-10（P=-0．016）和RANTEs（P=0．02）水平均明显高于HBV DNA阴性者。结论IP-10和RANTES的趋化作用广泛参与了机体对HBV免疫应答的各个阶段,并在肝脏组织的炎性损伤中发挥了作用。     

Protection against parenteral HIV-1 infection by homozygous deletion in the C-C chemokine receptor 5 gene.

OBJECTIVES: To investigate the role of the CC chemokine receptor 5 (CCR5) for parenteral transmission of HIV-1. DESIGN: The prevalence of the delta32 deletion within the CCR5 gene was determined in a cohort of 207 patients, who had received documented amounts of non-antibody-tested and non-inactivated clotting factor concentrate. METHODS: Chromosomal DNA of haemophiliacs was isolated from whole blood. A portion of the CCR5 gene spanning the delta32 deletion was amplified by PCR. The resulting DNA fragments were analysed by agarose gel electrophoresis. RESULTS: The rate of HIV-1 infection was correlated strongly with increasing amounts of inoculated clotting factor concentrate. None of the HIV-positive patients (n = 129) had the delta32/delta32 genotype, whereas 12 out of 78 HIV-negative haemophiliacs had the homozygous delta32 deletion. CONCLUSIONS: The delta32/delta32 genotype was highly protective against HIV-1 infection, even in patients who had received millions of non-inactivated clotting factor units. As it is likely that in the early 1980s plasma pools were contaminated not only with monocyte-tropic HIV-1 strains, CCR5 appears to be the major mediator of HIV-1 infection. Furthermore, we conclude that there must be other protective mechanisms in multiply exposed non-infected haemophiliacs who have wild-type CCR5.     

Discrimination of HIV-2 infection from HIV-1 infection by western blot and radioimmunoprecipitation analysis

Serum and plasma samples were collected from blood donors who were confirmed positive for antibodies to HIV-1 in the United States, and from blood donors and individuals in West Africa and Portugal who were positive for antibodies to HIV-1, HIV-2, or both. Western blots and sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) radioimmunoprecipitation assays (RIPA) utilizing native HIV-1 and HIV-2 proteins were performed on these specimens to determine the ability of these procedures to discriminate between HIV-1 and HIV-2 infections. Extensive serologic cross reactivity between HIV-1 and HIV-2 p24 was found in both populations. Antibody reactivity to the envelope protein gp120 was able to discriminate 20 of 20 (100%) U.S. specimens as HIV-1 infections. In specimens from West Africa and Portugal, Western blot and RIPA were in complete agreement on 33 of 42 samples (78.6%). Among these 33 specimens, 10 were found to be reactive for antibodies to HIV-1 only, 10 were reactive to HIV-2 only, and 13 were considered to be dually reactive, having antibodies reactive with both HIV-1 gp120 and HIV-2 gp120. Nine of the 42 specimens were discordant by Western blot and RIPA classification, being dually reactive by one procedure and reactive with only one viral gp120 by the other technique. Because of the serological cross reactivities between HIV-1 and HIV-2, in certain populations it is difficult to ascertain whether an individual is infected with HIV-1, HIV-2, a new viral type, or whether the individual is infected simultaneously with multiple viruses. More specific tests such as viral isolation or molecular probes may be necessary to distinguish between infections with these viruses in certain populations.     

Mixed cryoglobulinemia in HIV-1 infection: the role of HIV-1

BACKGROUND: Cryoglobulins are associated with chronic infections. OBJECTIVE: To investigate the prevalence of mixed cryoglobulinemia in patients with HIV-1 infection, the clinical spectrum of cryoglobulinemia in these patients, and the possible role of HIV-1 in cryoglobulin formation. DESIGN: Prospective cohort study. SETTING: Laiko Hospital, Athens, Greece. PATIENTS: 89 patients with HIV-1 infection. MEASUREMENTS: Serum and cryoglobulins were evaluated for antibodies to HIV and hepatitis C virus (HCV), HIV-1, and HCV viral load. RESULTS: Mixed cryoglobulins were detected in 24 patients with HIV-1 infection (27% [95% CI, 18% to 36%]). The HIV-1 viral load was higher in cryoglobulin-positive patients (median, 38.25 x 10(3) copies/mL [25th, 75th percentiles: 13.8 x 10(3) copies/mL, 78.55 x 10(3) copies/mL]) than in cryoglobulin-negative patients (median, 5.3 x 10(3) copies/mL [25th, 75th percentiles: 0.7 x 10(3) copies/mL, 27.2 x 10(3) copies/mL]) (P = 0.001). Antibodies to HIV were detected in all cryoprecipitates, and HIV-1 RNA sequences were identified in 22 of the 23 cryoprecipitates examined. Nine cryoglobulin-positive patients (38% [CI, 19% to 54%]) had clinical manifestations compatible with cryoglobulinemia. CONCLUSIONS: Mixed cryoglobulinemia is common in patients with HIV-1 infection.     

Viral levels in newborn African infants undergoing primary HIV-1 infection.

We examined weekly changes in viral levels in seven untreated infants infected with HIV at birth. Viral levels spiked immediately but reverted quickly to plateau levels typical of infant HIV infection within 2 weeks of first detected viraemia. We speculated that the depletion of naive, susceptible cells is responsible for the rapid decrease in spike levels and that the rapid replacement of lymphocytes in infants causes the high plateau viral levels (10(5) copies/ml) to be sustained.     

HIV-1与趋化因子受体的研究进展

近年来，HIV-1在借助趋化因子受体（CCR5，CXCR4）感染免疫细胞方面的研究引起了广泛关注。对趋化因子受体在HIV-1感染中结构与功能的研究对于促进人们了解艾滋病的发病机制及其预防具有重要意义。另外，对CCR5与CXCR4相关抑制剂的作用分析更为艾滋病疫苗的研制与应用提供了新的方向。本文就HIV-1与趋化因子受体的研究进展情况作一综述。     

HIV-1 Env蛋白与HIV-1感染

人免疫缺陷病毒Ⅰ型(HIV-1)是艾滋病的主要病原体,HIV-1 Env蛋白在病毒的感染、侵入和干扰机体免疫机能等方面发挥着重要作用,它可以干扰细胞正常的信号转导途径、导致合胞体的形成、引发细胞病变。HIV-1感染的细胞类型包括 CD_4~+辅助T细胞、单核巨噬细胞、树突状细胞、朗罕氏细胞、胎盘滋养层细胞、神经元细胞等。HIV-1感染引发的病理变化与免疫系统的变化密切相关,免疫系统的