Chemokine production in HIV-seropositive long-term asymptomatic individuals

The CD8+ T Cell Noncytotoxic Antiviral Responses

The CD8+ T cell noncytotoxic antiviral response (CNAR) was discovered during studies of asymptomatic HIV-infected subjects more than 30 years ago. In contrast to CD8+ T cell cytotoxic lymphocyte (CTL) activity, CNAR suppresses HIV replication without target cell killing. This activity has characteristics of innate immunity: it acts on all retroviruses and thus is neither epitope specific nor HLA restricted. The HIV-associated CNAR does not affect other virus families. It is mediated, at least in part, by a CD8+ T cell antiviral factor (CAF) that blocks HIV transcription. A variety of assays used to measure CNAR/CAF and the effects on other retrovirus infections are described. Notably, CD8+ T cell noncytotoxic antiviral responses have now been observed with other virus families but are mediated by different cytokines. Characterizing the protein structure of CAF has been challenging despite many biologic, immunologic, and molecular studies. It represents a low-abundance protein that may be identified by future next-generation sequencing approaches. Since CNAR/CAF is a natural noncytotoxic activity, it could provide promising strategies for HIV/AIDS therapy, cure, and prevention.

Suppression of MIP-1beta transcription in human T cells is regulated by inducible cAMP early repressor (ICER)

Local production of macrophage inflammatory protein-1beta (MIP-1beta), a beta-chemokine that blocks human immunodeficiency virus type 1 (HIV-1) entry into CD4+ CC chemokine receptor 5+ target cells, may be a significant factor in resistance to HIV-1 infection and control of local viral spread. The mechanisms governing MIP-1beta expression in T cells, however, are not well understood. Our results suggest that MIP-1beta RNA expression in T cells is dynamically regulated by transcriptional factors of the cyclic adenosine monophosphate (cAMP) responsive element (CRE)-binding (CREB)/modulator family. Transient transfection of primary human T cells with 5' deletion and site-specific mutants of the human MIP-1beta promoter identified an activated protein-1 (AP-1)/CRE-like motif at position -74 to -65 base pairs, relative to the TATA box as a vital cis-acting element and a binding site for inducible cAMP early repressor (ICER). Ectopic expression of ICER or induction of endogenous ICER with the cAMP agonists forskolin and prostaglandin E2 resulted in the formation of ICER-containing complexes, including an ICER:CREB heterodimer to the AP-1/CRE-like site and inhibition of MIP-1beta promoter activity. Our data characterize an important binding site for the dominant-negative regulator ICER in the MIP-1beta promoter and suggest that dynamic changes in the relative levels of ICER and CREB play a crucial role in cAMP-mediated attenuation of MIP-1beta transcription in human T cells.

High beta-chemokine expression levels in lymphoid tissues of simian/human immunodeficiency virus 89.6-vaccinated rhesus macaques are associated with uncontrolled replication of simian immunodeficiency virus challenge inoculum

Viral suppression by noncytolytic CD8+ T cells, in addition to that by classic antiviral CD8+ cytotoxic T lymphocytes, has been described for human immunodeficiency virus and simian immunodeficiency virus (SIV) infections. However, the role of soluble effector molecules, especially beta-chemokines, in antiviral immunity is still controversial. In an attenuated vaccine model, approximately 60% of animals immunized with simian/human immunodeficiency virus (SHIV) 89.6 and then challenged intravaginally with SIVmac239 controlled viral replication (viral RNA level in plasma, <10(4) copies/ml) and were considered protected (K. Abel, L. Compton, T. Rourke, D. Montefiori, D. Lu, K. Rothaeusler, L. Fritts, K. Bost, and C. J. Miller, J. Virol. 77:3099-3118, 2003). To determine the in vivo importance of beta-chemokine secretion and CD8+-T-cell proliferation in the control of viral replication in this vaccine model, we examined the relationship between viral RNA levels in the axillary and genital lymph nodes of vaccinated, protected (n = 20) and vaccinated, unprotected (n = 11) monkeys by measuring beta-chemokine mRNA levels and protein expression, the frequency of CD8+ T cells expressing beta-chemokines, and the extent of CD8+-T-cell proliferation. Tissues from uninfected (n = 3) and unvaccinated, SIVmac239-infected (n = 9) monkeys served as controls. Axillary and genital lymph nodes from unvaccinated and vaccinated, unprotected monkeys had significantly higher beta-chemokine mRNA expression levels and increased numbers of beta-chemokine-positive cells than did vaccinated, protected animals. Furthermore, the lymph nodes of vaccinated, unprotected monkeys had significantly higher numbers of beta-chemokine(+) CD8+ T cells than did vaccinated, protected monkeys. Lymph nodes from vaccinated, unprotected animals also had significantly more CD8+-T-cell proliferation and marked lymph node hyperplasia than the lymph nodes of vaccinated, protected monkeys. Thus, higher levels of virus replication were associated with increased beta-chemokine secretion and there is no evidence that beta-chemokines contributed to the SHIV89.6-mediated control of viral replication after intravaginal challenge with SIVmac239.

Interleukin-7-dependent production of RANTES that correlates with human immunodeficiency virus disease progression

There is a relationship between CD4-T-cell number and circulating interleukin 7 (IL-7) levels in human immunodeficiency virus (HIV)-positive individuals. Here, we show that IL-7 induced a dose-dependent production of CCL3 (MIP-1alpha), CCL4 (MIP-1beta), and CCL5 (RANTES) in peripheral blood mononuclear cells (PBMC), ex vivo tonsil lymphoid tissue of HIV(-) individuals, and PBMC from HIV(+) individuals, suggesting that IL-7 may regulate beta-chemokine production in vivo. In a cross-sectional study of HIV(+) individuals (n = 130), a weak but significant correlation between IL-7 and RANTES was noted (r = 0.379; P < 0.001). Remarkably, the correlation between IL-7 and RANTES increased to an r value of 0.798 (P < 0.001) if individuals with low CD4 cell counts (<200 cells/ micro l) were excluded from the analysis. Our results suggest that there is a relationship between IL-7 and the production of RANTES both in vitro and in vivo that is lost in immune-compromised patients (CD4 count of <200 cells/ micro l) but that could be restored by antiretroviral therapy. Unlike the case for IL-7, high levels of RANTES suggest an intermediate stage of HIV disease progression.

The CD8+ cell noncytotoxic anti-HIV response can be blocked by protease inhibitors

CD8+ cells from healthy HIV-infected individuals can suppress HIV replication in infected CD4(+) cells without killing the cells. This CD8+ cell noncytotoxic antiviral response (CNAR), observed by coculture of CD8+ cells with infected CD4+ cells, is associated with secretion of a CD8+ cell antiviral factor (CAF). In attempts to identify CAF, we discovered that certain protease inhibitors, particularly leupeptin, can block, by up to 95%, the anti-HIV activity in CD8+ cell culture fluids as well as inhibit CNAR. The effect is dose-dependent and is observed in up to 70% of the CAF and CNAR assays by using fluids and cells from several different subjects. Pretreatment of CD8+ cells with leupeptin reduces CNAR, further supporting an inhibitory effect on a CD8+ cell product. This inhibitory activity of protease inhibitors does not affect cell growth, expression of activation antigens, or viability of either CD8+ cells or the infected CD4+ cells. The results suggest that a part of the CD8+ cell noncytotoxic response involves the activity of a protease or a protein that interacts with protease inhibitors. Proteolysis of a CD8+ cell product(s) may be involved. This observation offers a promising approach for identifying the mechanism of CNARCAF activity.

Human and simian immunodeficiency virus-infected chimpanzees do not have increased intracellular levels of beta-chemokines in contrast to infected humans

This study was undertaken to explain why chimpanzees infected with HIV-1 (human immunodeficiency virus type 1) or SIV(cpz) (simian immunodeficiency virus of chimpanzee) are relatively resistant to AIDS (acquired immunodeficiency syndrome). The numbers of beta-chemokine-positive cells were compared between uninfected and infected humans and chimpanzees using three-color cytofluorometry. In humans, the percentage of beta-chemokine-positive cells was significantly higher in CD8(+) T and natural killer (NK) cells than in CD4(+) T cells in both uninfected and HIV-1-infected individuals. In the presence of HIV-1 infection, however, both CD8(+) and CD4(+) T cell subsets contained significantly more beta-chemokine-positive cells than in the absence of infection. Interestingly, in chimpanzees two important differences were noted. First, their percentage of beta-chemokine-positive CD8(+) T and NK cells was significantly higher than in uninfected humans. Second, in contrast to humans, infection with either HIV-1 or with SIV(cpz) was not associated with increased numbers of beta-chemokine-positive cells. These results indicate that: constitutive high levels of intracellular beta-chemokines in chimpanzees' CD8 lymphocytes and NK cells do not necessarily correspond to lower levels of virus replication during the chronic phase of infection; and increased percentages of beta-chemokine-positive cells in HIV-infection are not a correlate of disease resistance. The data suggest that neither pre-nor post-exposure levels of intracellular beta-chemokines are correlated with the subsequent control of disease progression.

Changes in CCR5 and CXCR4 expression and beta-chemokine production in HIV-1-infected patients treated with highly active antiretroviral therapy

The effect of highly active antiretroviral therapy (HAART) on the expression of CCR5 and CXCR4 HIV coreceptors and the production of the beta-chemokines regulated upon activation, normal T-cell expressed and secreted (RANTES), macrophage inflammatory protein (MIP)-1alpha, and MIP-1beta has been investigated in 30 HIV-1-infected individuals during 12-36 months of therapy. CCR5 expression was increased in both CD4 + and CD8 + subsets, whereas CXCR4 expression was upregulated only in CD4 + cells. CCR5 levels normalized during 36 months of therapy and positively correlated with the levels of memory, CD95 +, and HLA-DR + T cells. In contrast, the frequency of CXCR4-expressing cells was not significantly modified by HAART, although a downregulation was observed early after starting treatment. CXCR4 levels were significantly associated with the frequencies of naive T cells and negatively correlated with plasma viral load, CD95, and HLA-DR expression. An increased production of both spontaneous and lectin-induced RANTES, MIP-1alpha, and MIP-1beta was found at baseline in HIV-infected individuals. The spontaneous beta-chemokines production was not modified by 12 months of HAART, although a significant reduction was seen during the first months of therapy. A transient decrease of lectin-stimulated RANTES production was also observed, whereas the reduction of lectin-induced MIP-1alpha persisted for up to 12 months of therapy. In contrast, MIP-1beta secreted by phytohemagglutinin antigen-stimulated peripheral blood mononuclear cells progressively increased during HAART. In conclusion, our data indicate a normalization of CCR5 but not CXCR4 expression during suppressive therapy and changes in beta-chemokine production that may play a part in dictating the efficiency of viral infection and consequently the disease course.

The human immunodeficiency virus type 1 accessory protein Vpu induces apoptosis by suppressing the nuclear factor kappaB-dependent expression of antiapoptotic factors

Human immunodeficiency virus (HIV) type 1 Vpu is an integral membrane protein with a unique affinity for betaTrCP (TrCP), a key member of the SkpI-Cullin-F-box E3 ubiquitin ligase complex that is involved in the regulated degradation of cellular proteins, including IkappaB. Remarkably, Vpu is resistant to TrCP-mediated degradation and competitively inhibits TrCP-dependent degradation of IkappaB, resulting in the suppression of nuclear factor (NF)-kappaB activity in Vpu-expressing cells. We now report that Vpu, through its interaction with TrCP, potently contributes to the induction of apoptosis in HIV-infected T cells. Vpu-induced apoptosis is specific and independent of other viral proteins. Mutation of a TrCP-binding motif in Vpu abolishes its apoptogenic property, demonstrating a close correlation between this property of Vpu and its ability to inhibit NF-kappaB activity. The involvement of NF-kappaB in Vpu-induced apoptosis is further supported by the finding that the levels of antiapoptotic factors Bcl-xL, A1/Bfl-1, and TNF receptor-associated factor (TRAF)1, all of which are expressed in an NF-kappaB-dependent manner, are reduced and, at the same time, levels of active caspase-3 are elevated. Thus, Vpu induces apoptosis through activation of the caspase pathway by way of inhibiting the NF-kappaB-dependent expression of antiapoptotic genes.

Neutralizing antibodies against autologous human immunodeficiency virus Type 1 isolates in patients with increasing CD4 cell counts despite incomplete virus suppression during antiretroviral treatment

Antiretroviral-treated human immunodeficiency virus (HIV) type 1-seropositive individuals can remain clinically stable for a long period of time with an increasing CD4 cell count irrespective of incomplete viral suppression. We evaluated the role of neutralizing antibody (NtAb) activity in the etiopathogenesis of this viro-immunological disconnection (defined as an increasing CD4(+)-cell count despite a persistent, detectable viral load during antiretroviral therapy) in 33 patients failing therapy with two analogue nucleoside reverse transcriptase inhibitors. An HIV NtAb titer of >/=1:25 was detected in specimens from 16 out of 33 (48%) patients. A significant correlation was found between NtAb titers and CD4(+)-cell counts (P = 0.001; r = 0.546) but not with HIV RNA levels in plasma. Five patients with a viro-immunological disconnection had an NtAb titer of >1:125, statistically higher than the NtAb titers for the remaining 28 patients with both virologic and immunologic failure (P < 0.0001). The HIV-specific humoral immune response could play a role during antiretroviral treatment to improve immunological function despite an incomplete suppression of viral load.

Human immunodeficiency virus type-1 and chemokines: beyond competition for common cellular receptors

The chemokines and their receptors have been receiving exceptional attention in recent years following the discoveries that some chemokines could specifically block human immunodeficiency virus type 1 (HIV-1) infection and that certain chemokine receptors were the long-sought coreceptors which, along with CD4, are required for the productive entry of HIV-1 and HIV-2 isolates. Several chemokine receptors or orphan chemokine receptor-like molecules can support the entry of various viral strains, but the clinical significance of the CXCR4 and CCR5 coreceptors appear to overshadow a critical role for any of the other coreceptors and all HIV-1 and HIV-2 strains best employ one or both of these coreceptors. Binding of the HIV-1 envelope glycoprotein gp120 subunit to CD4 and/or an appropriate chemokine receptor triggers conformational changes in the envelope glycoprotein oligomer that allow it to facilitate the fusion of the viral and host cell membranes. During these interactions, gp120 appears to be capable of inducing a variety of signaling events, all of which are still not defined in detail. In addition, the more recently observed dichotomous effects, of both inhibition and enhancement, that chemokines and their receptor signaling events elicit on the HIV-1 entry and replication processes has once again highlighted the intricate and complex balance of factors that govern the pathogenic process. Here, we will review and discuss these new observations summarizing the potential significance these processes may have in HIV-1 infection. Understanding the complexities and significance of the signaling processes that the chemokines and viral products induce may substantially enhance our understanding of HIV-1 pathogenesis, and perhaps facilitate the discovery of new ways for the prevention and treatment of HIV-1 disease.

Relationship between HIV-1 Env subtypes A and D and disease progression in a rural Ugandan cohort

OBJECTIVE

To investigate the role of HIV-1 envelope subtypes on disease progression in a rural cohort of Ugandan adults where two major HIV-1 subtypes (A and D) exist.

METHODS

Participants of a clinical cohort seen between December 1995 and December 1998 had blood collected for HIV-1 subtyping. These included prevalent cases (people already infected with HIV at the start of the study in 1990) and incident cases (those who seroconverted between 1990 and December 1998). HIV-1 subtyping was carried out by heteroduplex mobility assay and DNA sequencing in the V3 env region. Disease progression was measured by the rate of CD4 lymphocyte count decline, clinical progression for the incident cases as time from seroconversion to AIDS or death, to first CD4 lymphocyte count < 200 x 10(6)/l and to the World Health Organization clinical stage 3. All analyses were adjusted for age and sex.

RESULTS

One hundred and sixty-four individuals, including 47 prevalent and 117 incident cases, had V3 env subtype data of which 65 (40%) were subtyped as A and 99 as D. In the incident cases, 44 (38%) were subtyped as A and 73 as D. There was a suggestion that for most end-points A had a slower progression than D. The cumulative probability of remaining free from AIDS or death at 6 years post-seroconversion was 0.72 [95% confidence interval (CI), 0.50 to 0.85] for A and 0.58 (95% CI, 0.42 to 0.71) for D, and the adjusted hazard ratio of subtype D compared to A was estimated to be 1.39 (95% CI, 0.66 to 2.94; P = 0.39). The estimated difference in rates of decline in square root CD4 lymphocyte counts was -0.41 per year (95% CI, -0.98 to 0.15; P = 0.15).

CONCLUSION

This study suggests that although subtype A may have a slower progression than D, HIV-1 envelope subtype is not a major factor in determining the progression of HIV-1 disease in a rural population in Uganda.

Higher macrophage inflammatory protein (MIP)-1alpha and MIP-1beta levels from CD8+ T cells are associated with asymptomatic HIV-1 infection

To test the hypothesis that beta-chemokine levels may be relevant to the control of HIV in vivo, we compared RANTES, MIP-1alpha, and MIP-1beta production from purified CD8(+) T cells from 81 HIV-infected subjects and from 28 uninfected donors. Asymptomatic HIV(+) subjects produced significantly higher levels of MIP-1alpha and MIP-1beta, but not RANTES, than uninfected donors or patients that progressed to AIDS. In contrast, beta chemokines in plasma were either nondetectable or showed no correlation with clinical status. The high beta-chemokine-mediated anti-HIV activity was against the macrophage tropic isolate HIV-1(BAL), with no demonstrable effect on the replication of the T-cell tropic HIV-1(IIIB). These findings suggest that constitutive beta-chemokine production may play an important role in the outcome of HIV-1 infection.

Plasma levels of the chemokine RANTES in macaque monkeys infected with pathogenic and non-pathogenic SIV/HIV-1 chimeric viruses at an early stage of infection

Plasma levels of the chemokine RANTES were examined in monkeys infected with either a pathogenic simian and human immunodeficiency chimeric virus (SHIV) or a non-pathogenic SHIV to determine whether RANTES levels were related to the pathogenicity of the virus, the plasma viral load, or the kinetics of CD4+ T-cells. In the results no significant correlation was found between the RANTES kinetics and changes in the CD4+ T-cell numbers nor the plasma viral loads in any of the monkeys, although a transient decrease of the RANTES level was observed in the pathogenic virus-infected monkeys. At least, the plasma RANTES level can not be used as an index of the pathogenicity of the virus at the early stage of infection.

Ex vivo modulation of RANTES and sCD30 by proinflammatory stimuli in HIV-seropositive and -negative individuals

RANTES and sCD30 were measured in ex vivo culture supernatants of unstimulated or stimulated PBMC in order to investigate their potential role as markers of acute immune activation. Patients in an advanced stage of HIV infection (AIDS A) were compared to AIDS patients who were evaluated for pneumonia at the time of blood withdrawal (AIDS B); HIV(+) individuals with nonprogressive infection (LTNP) and healthy donors (N) served as controls. Constitutive levels of RANTES were significantly elevated in AIDS B patients (P 0.0001), whereas spontaneous release of sCD30 was strongly correlated with the presence of both pneumonia (P 0.002) and HIV infection (P 0.004). LPS was a strong inducer of RANTES in all four categories; however, in AIDS B patients a negative and positive correlation between constitutive and induced levels was observed with LPS (P 0.0004) and IFN-gamma (P 0.006), respectively. We clearly showed that IFN-gamma reached a fourfold superinduction of sCD30 release in both HIV-positive and -negative individuals, whereas IL-6-driven production of both sCD30 and RANTES occurred only in healthy donors. Ex vivo RANTES levels may also be monitored as an index of acute immune activation under conditions of chronic activation of the immune system, whereas sCD30 release may be equally indicative of both acute and chronic processes of T cell activation. Proinflammatory stimuli differentially affected RANTES and sCD30 secretion in ex vivo PBMC cultures, suggesting complex pathways in the in vivo regulation of these two molecules.

Highly active antiretroviral therapy normalizes the potential for MIP-1alpha production in HIV infection

DESIGN

The CC chemokines RANTES, MIP-1alpha and MIP-1beta are ligands for CCR5, which has been identified as the principal co-receptor for macrophage tropic strains of HIV-1. This study investigated whether the inducible levels of RANTES, MIP-1alpha and MIP-1beta produced by cultured whole blood samples related to different rates of progression of HIV infection and to the introduction of Nelfinavir-based highly active anti-retroviral therapy (HAART).

METHODS

Study subjects were HIV-positive and categorized as "slow progressors" (n= 8) or as "fast progressors" (n= 7); the latter group were treated with HAART. MIP-1alpha, MIP-1beta and RANTES production was determined using commercial ELISA kits.

RESULTS

The inducible production of MIP-1alpha by whole blood cells in culture was significantly depressed in patients starting therapy compared with "slow progressors" and "normal donors". The levels of MIP-1alpha significantly increased with therapy at 12 weeks compared with pre-HAART levels (P= O.05) and became comparable to that of "normals" and "slow progressors". Differences in the inducible levels of MIP-1beta and RANTES for the separate subject groups were not significant.

CONCLUSIONS

The increase in inducible MIP-1alpha production following HAART might suggest a role for the chemokines in HIV disease, either for monitoring the outcome of therapy of HIV disease, or as a direct therapeutic intervention.

[Role of cytokines and chemokines in the non-progression of HIV infection in vertically infected children]

BACKGROUND

To study the cytokine production in vertically HIV-1-infected children with more of 7 years of HIV infection and different pattern of progression.

PATIENTS AND METHODS

We study 32 HIV-1-infected children: 8 NA children (age > 7 years, asymptomatic or with light symptoms, without antiretroviral treatment and TCD4+ > 25%); 10 NE1 children (> 6 years, symptomatic, with antiretroviral treatment and TCD4+ > 25%); 14 NE2-3 children (> 6 years, symptomatic, with antiretroviral treatment and TCD4+ < 25%) and 16 (C) controls, children non-VIH+. The peripheral mononuclear cells of HIV-infected children (PBLs) were cultivated and cytokine production was quantified in the supernatant.

RESULTS

The non-stimulated PBMC from HIV-infected children produced more TNF-alpha and less IL-2 that C-group. The production of IFN-gamma was lower in the groups NE1 and NE2-3 than in C-group. The production of IFN-gamma was higher in group NA than in NE2-3. In the phytohaemagglutinin (PHA) stimulated PBLs, the production of TNF-alpha was higher in NA and NE1 than in controls. The production of IL-2 was similar in NA and NE1 than in controls. The production of IL-2 was similar in NA and NE1 than in control group, but the groups NE2-3 produced less IL-2 than control and NE1 groups. The production of IFN-gamma and RANTES were significantly higher in NA than in controls. The groups NE1 and NE2-3 produced lower levels of IL-5 than control and NA groups. The groups NE2-3 produced lower levels of IL-10 than control group. The ratio IFN-gamma/IL-5 and IFN-gamma/IL-10 were higher in group NA than in control and NE1.

CONCLUSIONS

In non-progressors HIV-infected children the immune response is conserved and we have observed an increased Th1 response, while in progressors HIV-infected children receiving antiretroviral treatment we could observe a diminished Th2 response. Moreover, our data clearly indicate that the decrease of IL-2 is an early marker of HIV-infection.

Evaluation of the putative role of C-C chemokines as protective factors of HIV-1 infection in seronegative hemophiliacs exposed to contaminated hemoderivatives

BACKGROUND

Overproduction of beta-chemokines and genetic variations in chemokine receptors have been correlated with protection against infection by HIV-1 or slow progression to AIDS in infected individuals.

STUDY DESIGN AND METHODS

The protective role of chemokines and their receptors was evaluated in a group of seven uninfected (seronegative) hemophiliacs transfused with hemoderivatives presumably contaminated with HIV-1. This group was compared to a group of seven infected (seropositive) hemophiliacs and a group of healthy donors (controls). The CD4+ cell count, intracellular cytokine levels, beta-chemokine levels in plasma, beta-chemokine production by PBMNCs, and expression of chemokine receptors CCR5 and CXCR4 in CD4+ cells were evaluated. The occurrence of protective genotypes in CCR5, CCR2b, and SDF-1 (stromal cell-derived factor 1) genes and susceptibility to infection by HIV-1 were also studied.

RESULTS

Significant differences in the production and plasma levels of beta-chemokines among the three groups were not detected. Lower IL-2 and IFN-gamma production was observed in the uninfected exposed hemophiliacs than in the controls. Genetic analysis of CCR5, CCR2b, and SDF-1 showed several polymorphisms associated with resistance in some HIV-exposed uninfected hemophiliacs. However, these genetic features cannot explain the protection of all exposed hemophiliacs. In fact, only one patient, carrying two copies of CCR5 from which 32 bp was deleted, showed low CCR5 expression and low susceptibility to infection by a CCR5-using HIV-1 strain. In contrast, PBMNCs from all other individuals supported infection in vitro by both CCR5- and CXCR4-using HIV-1 strains.

CONCLUSION

It is not possible to assign to beta-chemo-kines and polymorphisms in chemokine receptors a central role in preventing HIV-1 infection. Natural protection against HIV-1 infection is likely to be due to a multiplicity of factors.

Spontaneous and antigen-induced production of HIV-inhibitory beta-chemokines are associated with AIDS-free status

The beta-chemokines RANTES, macrophage inflammatory protein (MIP)-1alpha, and MIP-1beta suppress infection by macrophage-tropic strains of HIV and simian immunodeficiency virus (SIV) by binding and down-regulating the viral coreceptor, CCR5. Accordingly, we have examined whether higher levels of CCR5 ligands are associated with a more favorable clinical status in AIDS. A cross-sectional study of 100 subjects enrolled in the Multicenter AIDS Cohort Study at the Baltimore site was conducted to measure chemokine production and lymphocyte proliferation by peripheral blood mononuclear cells (PBMC). Statistical analyses of the data revealed that the production of HIV-suppressive beta-chemokines by HIV antigen-stimulated PBMC was significantly higher in HIV-positive subjects without AIDS compared with subjects with clinical AIDS. Increased chemokine production was also correlated with higher proliferative responses to HIV antigens. Both parameters were significantly lower in the AIDS versus non-AIDS group. Notably, significantly higher levels of MIP-1alpha were also observed with unstimulated PBMC from seronegative subjects at risk for HIV infection released as compared with seropositive and non-Multicenter AIDS Cohort Study seronegative subjects. The association of chemokine production with antigen-induced proliferative responses, more favorable clinical status in HIV infection, as well as with an uninfected status in subjects at risk for infection suggests a positive role for these molecules in controlling the natural course of HIV infection.

Enhancing of anti-viral activity against HIV-1 by stimulation of CD8+ T cells with thymic peptides

HIV-1 can be neutralized by soluble factors produced and secreted by activated CD8+ T cells. Production of such anti-viral CD8 factors (including chemokines) can be induced with IL-2 or phytohaemagglutinin (PHA). In addition to PHA or IL-2, we have co-stimulated CD8+ T cells with PHA/IL-2 and a mixture of thymic peptides (TP) of molecular weights below 10 kD. For the activation, CD8+ T cells were purified from peripheral blood mononuclear cells of HIV-1- individuals and any resultant anti-viral activity was monitored using an HIV-1 neutralization assay. Using HIV-1 isolates highly resistant to chemokine inhibition we detected significantly higher levels of HIV-1 neutralizing activity in CD8+ T cell culture supernatants which had been co-activated with TP. When the TP-induced anti-viral activity was monitored, neutralization of both non-syncytia-inducing (NSI) and syncytia-inducing (SI) patient isolates was enhanced by 38% (NSI, PHA +/- TP), 66% (SI, PHA +/- TP), 28% (NSI, IL-2 +/- TP), and 57% (SI, IL-2 +/- TP) compared with the anti-viral activity present in supernatants from CD8+ T cell cultures stimulated only with PHA or IL-2. Peptide sequence analysis of purified TP showed that the TP mixture predominantly contains peptides with homology to human histone and collagen sequences. Our data demonstrate that CD8+ T cells are additionally activated by a mixture of TP. In this way, the production of HIV-1 neutralizing CD8 factors can be enhanced.

Chemokines and chemokine receptors: role in HIV infection

Our understanding of the host factors that determine susceptibility and progression of HIV infection has been very limited. In particular, it has been not clear why some people remain uninfected being repeatedly exposed to HIV-1, and others who have been infected by HIV, remain clinically asymptomatic for long periods of time. Recently it has been demonstrated that mutated forms of a number of chemokine receptors that act as coreceptors for HIV-1 entry may account for some of these phenomena. Furthermore, chemokines such as RANTES and others, being the natural ligands for chemokine receptors, have been shown to be effective inhibitors of HIV-1 infection. In this review we discuss some of the genetic, immunological, virological and epidemiological data relevant to the very important role chemokines and chemokine receptors play in HIV pathogenesis with special reference to the increased susceptibility of the African host to HIV infection.

Increased intracellular accumulation of macrophage inflammatory protein 1beta and its decreased secretion correlate with advanced HIV disease

Considering that the chemokine macrophage inflammatory protein 1beta (MIP1beta) may serve as a competitive inhibitor for HIV entry, the objective of this study was to compare intracellular and extracellular levels of MIP1beta, in untreated HIV-infected individuals. HIV patients and healthy controls were tested by two-color flow cytometry for intracellular MIP1beta, in freshly explanted CD4 and CD8 lymphocytes, and in monocytes. Sera and plasma collected on the same day were tested, respectively, by enzyme-linked immunosorbent assay (ELISA) for MIP1beta concentration and for number of HIV-RNA copies, using nucleic acid sequence-based amplification procedure (NASBA) methodology. Results demonstrate that a high intracellular level of MIP1beta appears to be linked to a deterioration in the immune status of HIV patients (i.e., low CD4 counts) and to a high viral load. Moreover, an inverse relationship exists between the intracellular and the "secreted" form of MIP1beta, thus leading to the hypothesis that the regulation of cellular accumulation and secretion of MIP1beta and of other chemokines may be disrupted during AIDS development.

Chemokine and chemokine receptor expression after combined anti-HIV-1 interleukin-2 therapy

OBJECTIVE

To evaluate changes in serum levels of chemokines, chemokine production, and chemokine receptor expression by peripheral blood mononuclear cells (PBMC), after treatment of HIV-1-infected individuals with interleukin (IL)-2.

METHODS

We determined CC-chemokine levels by enzyme-linked immunosorbent assay and chemokine receptor expression using FACS analysis or reverse transcriptase polymerase chain reaction in samples from patients receiving highly active antiretroviral therapy (HAART) supplemented with low doses of recombinant IL-2. Results were compared with a control group of patients receiving HAART.

RESULTS

Serum levels of RANTES, macrophage inflammatory protein (MIP)-1alpha and MIP-1beta, and the production of these chemokines by unstimulated and stimulated PBMC, were not modified by IL-2 administration. In contrast, the IL-2-treated group showed increased expression of CXC-chemokine receptor (CXCR)-4 in the CD4 T-cell subset after 24 weeks of treatment, which was associated with increased mRNA levels. A lower increase was observed in CC-chemokine receptor (CCR)-5 expression by CD4 T cells. No modifications in the expression of these receptors were observed in monocytes and no general increases were observed in mRNA levels of chemokine receptors CCR-1, CCR-2b and CCR-3 in IL-2-treated patients.

CONCLUSIONS

IL-2 at doses that significantly increase CD4 cell counts does not induce dramatic modifications in the chemokine/chemokine receptor system. Only expression of CXCR-4 appears to increase, due in part to lymphocyte activation. Therefore, the efficacy of IL-2 treatment in HIV-1 infection has to be evaluated by its ability to activate and induce faster regeneration of the immune system.

Differential effects of human immunodeficiency virus isolates on beta-chemokine and gamma interferon production and on cell proliferation

All human immunodeficiency virus (HIV) isolates can grow readily in primary CD4(+) T cells, but they can be distinguished by their ability to replicate in macrophages and established T-cell lines. The macrophage-tropic viruses are generally non-syncytium inducing (NSI), whereas the T-cell-line-tropic viruses are syncytium inducing (SI) in cultured cells. We now demonstrate that infection of CD4(+) T cells by NSI and SI viruses shows a differential effect on production of beta-chemokines and gamma interferon. Infection by NSI viruses increased production of MIP-1alpha, MIP-1beta, and gamma interferon, whereas infection by SI viruses had no effect or decreased production of these cytokines. Production of RANTES was slightly increased during infection by both virus phenotypes. This differential effect of NSI and SI viruses was observed at the level of beta-chemokine mRNA as well as at the level of protein expression. Infection by NSI viruses also increased CD4(+) cell proliferation. These results may have relevance for a differential role of HIV strains in AIDS pathogenesis.

Potential contributions of viral envelope and host genetic factors in a human immunodeficiency virus type 1-infected long-term survivor

The lack of clinical progression in some individuals despite prolonged human immunodeficiency virus type 1 (HIV-1) infection may result from infection with less-pathogenic viral strains. To address this question, we examined the HIV-1 envelope protein from a donor with a low viral burden, stable CD4(+) T-lymphocyte counts, and little evidence of CD8(+) T-cell expansion, activation, or immune activity. To avoid potential changes in envelope function resulting from selection in vitro, envelope clones were constructed by using viral RNA isolated from uncultured peripheral blood mononuclear cells (PBMC). The data showed that recombinant viruses containing envelope sequences derived from RNA isolated from patient PBMC replicated poorly in primary CD4(+) T cells but demonstrated efficient growth in macrophages. The unusual phenotype of these viruses could not be explained solely by differential utilization of coreceptors since the chimeric viruses, as well as an uncloned isolate obtained from the same visit date, can utilize CCR5. In addition, the donor's own cells appeared resistant to infection with chimeric viruses containing autologous envelope sequences. Genotype analysis revealed that the donor was heterozygous for the previously described 32-bp deletion in CCR5 which may be linked with prolonged survival in HIV-1-infected individuals. These data suggest that the changes in envelope sequences confer properties of viral attenuation, which together with the CCR5 +/Delta32 genotype could account for the long-term survival of this patient.

Adaptation to promiscuous usage of CC and CXC-chemokine coreceptors in vivo correlates with HIV-1 disease progression

OBJECTIVE

To study coreceptor usage of sequential primary HIV-1 isolates in a longitudinal follow-up cohort of HIV-1-infected men to understand its contribution to pathogenesis of HIV disease.

DESIGN

Viral coreceptor usage of sequential primary isolates from HIV-1-infected individuals was examined at various timepoints and data was compared with CD4 cell counts, rates of disease progression and beta-chemokine production.

METHODS

Fifty-eight sequential primary isolates were obtained from four rapid progressors, six late progressors, and three long-term nonprogressors (LTNP) and their coreceptor usage was examined by infection of peripheral blood mononuclear cells (PBMC) from donors with wild-type or non-functional CC-chemokine receptor (CCR)-5, and by infection of GHOST4 cells expressing CD4 and various chemokine receptors [CCR-1-CCR-5, CXC-chemokine receptor (CXCR)-4, BOB/GPR15, BONZO/STRL33]. Production of RANTES and macrophage inflammatory protein (MIP)-1beta was examined using unstimulated or phytohemagglutinin (PHA)-stimulated PBMC isolated from these individuals at multiple timepoints during infection.

RESULTS

A switch from single CCR-5 coreceptor usage to multiple coreceptor usage occurred in all four rapid progressors and three out of six late progressors. In addition to the commonly used coreceptors CXCR-4, CCR-5, and CCR-3, some of the viruses isolated from patients in the terminal stage of infection also used CCR-1, CCR-2b, CCR-4, and BOB as coreceptors. The emergence of viral variants capable of utilizing multiple coreceptors generally preceded CD4 cell decline to < 200 x 10(6)/l and correlated with the onset of AIDS. In contrast, three LTNP maintained exclusive usage of CCR-5 over a period of 7-12 years post-infection. Endogenous production of RANTES and MIP-1beta by PBMC from LTNP was not significantly different from rapid and late progressors. However, PHA-driven production of both chemokines was significantly higher in LTNP, suggesting that in vivo activating stimuli might curtail HIV replication by inducing these chemokines.

CONCLUSIONS

Viral variants capable of utilizing a broad range of coreceptors correlated with HIV-1 disease progression. In contrast, LTNP maintain exclusive usage of CCR-5 and produce higher levels of beta-chemokines. Thus, both viral and host determinants leading to the emergence of viral variants capable of using an expanded range of coreceptors may be likely determinants of disease progression.

HIV pathogenesis: mechanisms of susceptibility and disease progression

The understanding of the factors associated with HIV-1 acquisition and disease progression has been significantly advanced in the past few years. These factors can be broadly defined as intrinsic or acquired and are operative at the levels of disease acquisition and progression or both. Much recent attention has focused on the identification of allelic variants at specific genetic loci that alter either susceptibility to infection or the natural history of disease progression. In addition, a more detailed understanding of the immunologic responses to HIV-1 and factors that perturb these responses has greatly enhanced our understanding of the immunologic control of HIV-1 and the roles of cofactors in HIV-1 acquisition and disease progression.

RANTES production in HIV-1 antigen-stimulated whole blood culture: relationship with type 1 immune response and plasma viral load in individuals infected with HIV-1

Host factors which control replication and clearance of human immunodeficiency virus (HIV) are poorly understood. RANTES (regulated on activation, normal T cell expressed and secreted) and other beta-chemokines may be HIV-1-suppressive factors but their role in the progression of HIV-1 infection is a subject of controversy. We investigated the relationship between production of RANTES and correlates of disease progression in 15 patients infected with HIV-1. We used whole blood culture to study the production of RANTES, interferon (IFN)-gamma, interleukin (IL)-4 and IL-13 in response to supernatant of T cells infected with HIV-1. A defect of RANTES production was associated with a predominant type 2 and decreased type 1 cytokine profile (IL-4 and/or IL- 13 > IFN-gamma). We obtained a positive correlation between RANTES and IFN-gamma (P = 0.004) and the ratio of type 1 and type 2 cytokines IFN-gamma/IL-4 (P = 0.04) and IFN-gamma/IL-13 (P = 0.003), and a negative correlation between RANTES production and HIV-1 RNA copy number in plasma (P = 0.01). The same pattern of correlation was observed between HIV-1 p24-stimulated production of RANTES and the plasma viral load (P = 0.02, n = 15). The measurement of RANTES produced by heparinized whole blood in response to HIV-1 antigens appears as a potentially valuable tool to assess the defect of type 1 immune response in individuals infected with HIV-1 and to define whether the absence of a RANTES response may play a role in the increased rate of HIV-1 replication.

Chemokine receptors and chemokines in HIV infection

Suppression of HIV by chemokines represents a special case in virology and immunology where soluble molecules other than antibodies inhibit infection by a specific virus. The basis for this inhibition is that HIV has evolved to use certain chemokine receptors as "coreceptors" for entry into host cells. Human genotypes that reduce or prevent coreceptor expression are strongly associated with protection against infection and slower disease progression. We suggest that local production of certain chemokines can produce a similar modulation of coreceptor expression, and mounting evidence indicates that chemokine release is a major determinant of protection from HIV infection. Here we review this evidence and explore future avenues for investigating the role of chemokines in controlling HIV infection.

Chemokine receptors and the clinical course of HIV-1 infection

For several years, the cellular basis behind the differences in HIV-1 tropism and the species specificity of HIV-1 has remained unclear. Since the discovery that chemokine receptors are essential cofactors for entry of HIV-1 into cells, tremendous progress has been made in the understanding of the role played by co-receptors in HIV-1 biological variability, HIV-1 transmission and AIDS pathogenesis.

Induction of specific T-cell responses in HIV infection

OBJECTIVES

To induce recovery of HIV-1-specific immune responses by combining immunization with antiviral chemotherapy.

DESIGN

Forty HIV-infected patients entered a double-blind study with recombinant gp160 in combination with zidovudine or placebo. The pretreatment observation period was around 2 years and the treatment period 5 years. Eighty matched HIV-infected patients served as controls.

METHODS

Immune status was monitored by proliferation assays with HIV-specific antigens, mitogens and recall antigens. Viral load, CD4 cell counts, apoptosis, T-cell clonal analysis and CC-chemokine receptor (CCR)-5 status were determined.

RESULTS

All immunized patients showed a strong and HIV-specific T-cell proliferative response. This response was related to the immunizations, and was not enhanced by the zidovudine monochemotherapy given during the first 6 months of the immunizations. The treatments did not significantly alter viral load. Potent antiviral combination therapy given to non-immunized individuals reduced their viral load but did not influence HIV-specific immune responses. There was a trend for an increased frequency of non-progression in the immunized group compared with controls. These individuals had both wild-type and mutant CCR-5 genes.

CONCLUSION

The results clearly show that restoration of HIV-specific T-cell immunity occurs after immunization with the HIV gp160 antigen and is not influenced by the addition of antiviral monochemotherapy. Even intensive chemotherapy alone did not restore HIV-specific immunity and immunization alone did not influence viral load. This suggests that combinations of intensive chemotherapy with specific HIV immunization would result both in viral load reduction and improved immune responses to HIV.

Endogenous production of beta-chemokines by CD4+, but not CD8+, T-cell clones correlates with the clinical state of human immunodeficiency virus type 1 (HIV-1)-infected individuals and may be responsible for blocking infection with non-syncytium-inducing HIV-1 in vitro

Recent studies have demonstrated that the beta-chemokines RANTES, MIP-1alpha, and MIP-1beta suppress human immunodeficiency virus type 1 (HIV-1) replication in vitro and may play an important role in protecting exposed but uninfected individuals from HIV-1 infection. However, levels of beta-chemokines in AIDS patients are comparable to and can exceed levels in nonprogressing individuals, indicating that global beta-chemokine production may have little effect on HIV-1 disease progression. We sought to clarify the role of beta-chemokines in nonprogressors and AIDS patients by examination of beta-chemokine production and HIV-1 infection in patient T-lymphocyte clones established by herpesvirus saimiri immortalization. Both CD4+ and CD8+ clones were established, and they resembled primary T cells in their phenotypes and expression of activated T-cell markers. CD4+ T-cell clones from all patients had normal levels of mRNA-encoding CCR5, a coreceptor for non-syncytium-inducing (NSI) HIV-1. CD4+ clones from nonprogressors and CD8+ clones from AIDS patients secreted high levels of RANTES, MIP1alpha, and MIP-1beta. In contrast, CD4+ clones from AIDS patients produced no RANTES and little or no MIP-1alpha or MIP-1beta. The infection of CD4+ clones with the NSI HIV-1 strain ADA revealed an inverse correlation to beta-chemokine production; clones from nonprogressors were poorly susceptible to ADA replication, but clones from AIDS patients were highly infectable. The resistance to ADA infection in CD4+ clones from nonprogressors could be partially reversed by treatment with anti-beta-chemokine antibodies. These results indicate that CD4+ cells can be protected against NSI-HIV-1 infection in culture through endogenously produced factors, including beta-chemokines, and that beta-chemokine production by CD4+, but not CD8+, T cells may constitute one mechanism of disease-free survival for HIV-1-infected individuals.

Enhanced activation of platelets with abnormal release of RANTES in human immunodeficiency virus type 1 infection

Besides their role in hemostasis, platelets are involved in inflammatory and immunological processes, and we hypothesize that platelet activation may play an immunopathogenetic role in HIV-1 infection. Blood was drawn from 15 controls and 20 HIV-1-infected patients with normal platelet counts, classified into groups of non-AIDS and AIDS. Platelet activation was detected using flow cytometry with mAbs against the release markers P-selectin and CD63, mAb against GPIb, and the probe annexin V detecting surface exposure of aminophospholipids. The amount of microvesicles was measured using mAb against GPIIIa. Compared to controls, blood samples from HIV-1-infected patients showed significantly enhanced levels of microvesicles and activated platelets as detected by their exposure of P-selectin, CD63, and aminophospholipids, as well as reduction in GPIb expression. Increased expression of P-selectin and amounts of microvesicles were most pronounced in advanced clinical and immunological disease. When studying the effect of HIV-1 protease inhibitor therapy (indinavir) on platelet activation, we found that concomitant with a profound decrease in plasma viral load, there was a near normalization of several of the parameters reflecting enhanced platelet activation. Finally, we demonstrated that platelets may be an important source of the chemokine RANTES in HIV-1-infected patients. Although both unstimulated and SFLLRN-stimulated platelets from asymptomatic patients had enhanced release of RANTES, platelets from AIDS patients were characterized by markedly enhanced spontaneous, but decreased SFLLRN-stimulated release of this chemokine. Taken together, these results, which demonstrate for the first time increased platelet activation in HIV-1-infected patients with normal platelet counts, may represent a previously unrecognized immunopathogenic factor in HIV-1 infection.

Increased frequency of CCR-5 delta 32 heterozygotes among long-term non-progressors with HIV-1 infection. The Australian Long-Term Non-Progressor Study Group

BACKGROUND

The beta-chemokine receptor CCR-5 is used as a coreceptor by macrophage-tropic strains of HIV-1 to gain entry into CD4+ cells.

OBJECTIVE

To determine the effect of a common 32 base-pair deletion mutation in the CCR-5 gene (CCR-5 delta 32) on progression of HIV infection to AIDS, and to assess the level of heterozygosity for this mutation in a well-defined group of long-term non-progressors (LTNP).

PARTICIPANTS

Sixty-four HIV-1-infected LTNP (CD4+ T lymphocyte count > 500 x 10(6)/l after 8 years) were compared with 95 individuals infected within a similar period (1983-1986) but who had rapidly progressed to AIDS and death, and with a further 120 HIV-positive individuals with CD4+ counts < 500 x 10(6)/l.

METHODS

The presence of the CCR-5 delta 32 mutation was assessed using polymerase chain reaction with primers spanning the 32 base-pair deletion. CD4+ and CD8+ counts, plasma HIV-1 RNA, p24 antigen and beta 2-microglobulin levels in LTNP carrying the CCR-5 delta 32 mutation were compared with LTNP lacking the mutation.

RESULTS

A marked increase in the frequency of CCR-5 delta 32 heterozygosity was found among LTNP (35.9%) compared with rapid progressors (12.6%; P = 0.0005) and patients selected on the basis of a CD4+ T-cell count < 500 x 10(6)/l (12.5%; P = 0.0004). LTNP heterozygous for CCR-5 delta 32 had a significantly higher CD8+ T-cell count than those without the mutation (1218 versus 972 x 10(6)/l; P = 0.044). No significant correlation was observed between heterozygosity and CD4 count, viral load, p24 antigen or beta 2-microglobulin within the LTNP group.

CONCLUSIONS

This study provides the strongest evidence to date for the importance of a single copy of the CCR-5 delta 32 mutation in long-term non-progression of HIV infection, which may involve, in part, CD8+ T lymphocytes.

HIV-specific mucosal and cellular immunity in HIV-seronegative partners of HIV-seropositive individuals

HIV-specific mucosal and cellular immunity was analyzed in heterosexual couples discordant for HIV status in serum and in HIV-unexposed controls. HIV-specific IgA but not IgG was present in urine and vaginal wash samples from HIV-exposed seronegative individuals (ESN), whereas both IgA and IgG were observed in their HIV-seropositive partners; antibodies were not detected in low-risk controls. Envelope protein (Env) peptide-stimulated interleukin-2 (IL-2) production by peripheral blood mononuclear cells (PBMCs) was detected in 9 out of 16 ESNs, 5 out of 16 HIV-infected patients and 1 out of 50 controls. Env peptide-stimulated PBMCs of ESNs produced more IL-2 and less IL-10 compared with those of HIV-infected individuals; no differences were observed in chemokine production or in CCR5 expression. These data demonstrate that a compartmentalized immune response to pathogens is possible in humans and raise the possibility of protective roles for cell-mediated immunity and mucosal IgA in HIV-seronegative individuals exposed to HIV.

Host factors in the pathogenesis of HIV disease

Host factors play an important role in determining rates of disease progression in human immunodeficiency virus (HIV)-infected individuals. HIV is able to subvert the host immune system by infecting CD4+ T cells that normally orchestrate immune responses and by inducing the secretion of proinflammatory cytokines that the virus can utilize to its own replicative advantage. The recognition that certain chemokine receptors serve as necessary co-factors for HIV entry into its target cells as well as the fact that ligands for these receptors can modulate the efficiency of HIV infection has expanded the number and scope of host factors that may impact the pathogenesis of HIV disease. This area of investigation will no doubt yield novel therapeutic strategies for intervention in HIV disease; however, caution is warranted in light of the enormous complexity of the pleiotropic cytokine and chemokine networks and the uncertainty inherent in manipulating these systems. HIV-infected long-term non-progressors represent an excellent model to study potential host factors involved in HIV disease pathogenesis. Genetic factors certainly have a major impact on the immune responses mounted by the host. In this regard, a polymorphism in the gene for the HIV co-receptor CC chemokine receptor 5 (CCR5), which serves as a co-receptor for macrophage (M)-tropic strains of HIV, affords a high degree of protection against HIV infection in individuals homozygous for the genetic defect and some degree of protection against disease progression in HIV-infected heterozygotes. HIV-specific immune responses, including cytotoxic T-lymphocyte (CTL) responses and neutralizing antibody responses, also appear to play salutary roles in protecting against disease progression.

Do beta-chemokines have clinical relevance in HIV infection?

The role of beta-chemokines in HIV infection was evaluated. The kinetics of regulated upon activation of normal T cell expressed and secreted, macrophage inflammatory protein-1alpha, and macrophage inflammatory protein 1beta production by stimulated T lymphocytes did not differ substantially between HIV-infected (asymptomatic and with AIDS) and uninfected subjects. Maximal production of these beta-chemokines by activated peripheral blood cells was higher in the infected individuals than in uninfected individuals, but no significant difference was observed between healthy infected subjects and AIDS patients. Evaluation of the effect of HIV replication on beta-chemokine production indicated that acute infection of CD4+ T cells with non-syncytia-inducing (NSI) viruses generally increased beta-chemokine production two to eightfold, whereas with SI strains, it led to decreased production. The sensitivity of an individual's virus to beta-chemokine-mediated inhibition correlated with the NSI virus phenotype and a healthy clinical state. 50% of the AIDS patients, however, had NSI viruses that were sensitive to beta-chemokines. Finally, anti-beta-chemokine-neutralizing antibodies caused a more rapid release of HIV by CD4+ T cells naturally infected by NSI, but not SI, viruses indicating that endogenously produced chemokines can affect HIV production in culture. These findings suggest that beta-chemokines may affect HIV replication when an NSI virus is involved, but provide little evidence that they substantially influence HIV infection and pathogenesis.

HIV infection and aging: mechanisms to explain the accelerated rate of progression in the older patient

Age is an important predictor of progression in HIV infections. Not only do older individuals' develop AIDS more rapidly than younger persons, they die more quickly after developing an AIDS-defining illness. While the elderly have higher morbidity and mortality rates from viral and bacterial infections, the mechanism(s) responsible for the more rapid progression of HIV infection in older individuals has not been described. Our results demonstrate that the destruction of T cells in both young and old HIV infected patients progresses at the same rate. HIV 1-infected cells from older individuals do not appear more susceptible to immune mediated destruction. The more rapid progression appears due to an inability of older persons to replace functional T cells that are being destroyed. These findings suggest that improved survival in older HIV infected individuals will require more aggressive antiretroviral therapies as well as continued research to identify and preserve immune system elements that control the virus.

Chemoattractant factors (IP-10, MIP-1alpha, IL-16) mRNA expression in mononuclear cells from different tissues during acute SIVmac251 infection of macaques

We have used semiquantitative RT-PCR to monitor the expression of mRNA encoding chemoattractant factors IP-10, MIP-1alpha, and IL-16 in freshly isolated peripheral blood mononuclear cells (PBMCs), lymph node mononuclear cells (LNMCs), and mononuclear cells obtained after bronchoalveolar lavages (BALMCs) of two cynomolgus macaques inoculated intravenously with a pathogenic isolate of simian immunodeficiency virus, SIVmac251. Concomitant with the peak of systemic viral replication (two weeks after experimental inoculation) and proinflammatory cytokine IL-6 mRNA expression, high levels of MIP-1alpha and IP-10 mRNA were produced in LNMCs and BALMCs. In BALMCs, in which we have reported a marked progressive overexpression of IFN-gamma mRNA coinciding with an increase in the CD8+ lymphocyte percentages, we noticed a progressive overexpression of IL-16 mRNA. Our results suggest the role of chemokines IP-10, MIP-1alpha, and IL-16 in the development of inflammatory and immune responses during the early stages of lentiviral infection.