The immunopathogenesis of human immunodeficiency virus infection

Immunopathogenesis of HIV infection

The rate of progression of HIV disease may be substantially different among HIV-infected individuals. Following infection of the host with any virus, the delicate balance between virus replication and the immune response to the virus determines both the outcome of the infection, i.e. the persistence versus elimination of the virus, and the different rates of progression. During primary HIV infection, a burst of viremia occurs that disseminates virus to the lymphoid organs. A potent immune response ensues that substantially, but usually not completely, curtails virus replication. This inability of the immune system to completely eliminate the virus leads to establishment of chronic, persistent infection that over time leads to profound immunosuppression. The potential mechanisms of virus escape from an otherwise effective immune response have been investigated. Clonal deletion of HIV-specific cytotoxic T-cell clones and sequestration of virus-specific cytotoxic cells away from the major site of virus replication represent important mechanisms of virus escape from the immune response that favor persistence of HIV. Qualitative differences in the primary immune response to HIV (i.e. mobilization of a restricted versus broader T-cell receptor repertoire) are associated with different rates of disease progression. Therefore, the initial interaction between the virus and immune system of the host is critical for the subsequent clinical outcome.

Implications of increased infectivity in early-stage HIV infection. Application of a Bernoulli-process model of HIV transmission

Recent reports suggest that the infectivity of sexually transmitted HIV (i.e., the probability of transmission on a single sexual contact) may be up to 1,000 times greater during the first few months of infection than during the long asymptomatic period that precedes the development of AIDS. Assuming the validity of this estimate, a simple Bernoulli-process model of HIV transmission indicates that, in some cases, the expected number of secondary infections is greater for the brief period of primary infection than for the much longer asymptomatic phase. The implications of these findings for current HIV/AIDS prevention practices are analyzed with particular attention to the role of condom use in preventing HIV transmission.

Regulation of HIV-1 long terminal repeats by interaction of C/EBP(NF-IL6) and NF-kappaB/Rel transcription factors

We report the characterization of a CAAT enhancer-binding protein (C/EBP) (NF-IL6) element encompassing the region from -174 to -166 of the U3 long terminal repeat (LTR) region of HIV-1. This C/EBP cis sequence was found to bind to C/EBPbeta and C/EBPdelta factors in DNA band shift assay. Transfection of NTera-2 cells with a HIV-1-LTR CAT construct (pC15CAT), together with C/EBPbeta or C/EBPdelta expression plasmids showed that C/EBP proteins strongly activated the HIV-1 promoter. Deletions encompassing the C/EBP-binding site resulted in the enhancement of the LTR activation mediated by C/EBP proteins, suggesting that other sequences located 3' to -170 were indeed the target for C/EBP factors. This possibility was confirmed by using the pCD54E9CAT plasmid, in which the NF-kappaB enhancer was inserted 5' to the HIV-1 LTR TATA box. A NF-kappaB1(p50) expression plasmid was also utilized to test for functional co-operation between NF-kappaB and C/EBP factors. We observed that p50 middle dotC/EBPbeta and p50 middle dotC/EBPdelta complexes were generated in tested cells and strongly activated the HIV-1 LTR by binding to the NF-kappaB sequences. The physical association of NF-kappaB1(p50) with C/EBP factors was assayed by direct interaction of in vitro translated p50 proteins with C/EBPbeta or C/EBPdelta produced as glutathione S-transferase fusion proteins. Moreover, p50 middle dotC/EBPbeta complexes were observed in vivo by using DNA affinity studies with biotinylated NF-kappaB oligonucleotides. By using mutant forms of p50 or C/EBPbeta proteins we found that the transactivation of HIV-1 LTR by p50 middle dotC/EBPbeta complexes required the DNA-binding domain of p50 and the transcription activation domain of C/EBPbeta.

Comparison of virus burden in blood and sequential lymph node biopsy specimens from children infected with human immunodeficiency virus

BACKGROUND

Lymph nodes serve as reservoirs for the replication of human immunodeficiency virus (HIV) type 1. Comparison of serial measurements of virus burden in lymph nodes and peripheral blood after a change in antiretroviral therapy may provide insights into pathogenic mechanisms and permit a more accurate assessment of a therapeutic response.

STUDY DESIGN

Nevirapine was added to the drug regiment of eight children with HIV infection treated with the combination of zidovudine and didanosine who had increasing levels of serum p24 antigen. Lymph node biopsies were performed at entry and after 12 weeks of therapy.

RESULTS

Neither CD4 counts nor p24 antigen level correlated with the degree of viremia as measured by ribonucleic acid copy numbers in plasma. Correlations were found between HIV DNA copy number in peripheral blood mononuclear cells and HIV DNA copy number in lymph nodes (p = 0.02), as well as between peripheral blood CD4 counts and lymph node architecture. The HIV signals in the lymph nodes conformed to the anatomic organization of apical light zones in the germinal centers; however, in more advanced disease stages, organized germinal centers disappeared as evidence by a decline in the extent of the follicular dendritic network.

CONCLUSIONS

Lymph node biopsies in this small number of HIV-infected children revealed a progressive loss of an organized architecture, especially of the follicular dendritic network. This correlated with a progressive loss of CD4+ cells but not with other measures of disease stage, including viral load, as measured by ribonucleic acid copy numbers.

Viral load and immunophenotype of cells obtained from lymph nodes by fine needle aspiration as compared with peripheral blood cells in HIV-infected patients

We wished to establish the feasibility of fine needle aspiration of lymph nodes as a noninvasive method for measuring subsets of immune cells and viral load in HIV-infected patients. Twenty-five patients (CD4+ T cell range 4-760/microl, median 362) were selected. Lymph node aspiration was attempted in 21 patients. Lymph node cells (LNC), ranging from 6 x 10(3) to 2 x 10(6) (median 6 x 10(5)) were obtained in 17 subjects, and compared with peripheral blood mononuclear cells (PBMC) obtained simultaneously. Immunophenotype could be determined by flow cytometry in 9 patients. Mean percent of CD4+ CD3+ T cells in LNC and PBMC and 23.2 and 14.6. Mean percent of CD8+ CD3+ T cells in LNC and PBMC was 23.1 and 45.0, respectively. Therefore, CD4+/CD8+ ratios were much higher in LNC (mean +/- SD: 1.06 +/- 0.31) than in PBMC (0.35 +/- 0.13). The amount of HIV DNA (11 patients) and RNA (8 patients) was determined in the plasma, LNC, and PBMC by competitive reverse transcriptase-polymerase chain reaction (RT-PCR). The number of copies of viral DNA/10(5) cells was higher in LNC than in PBMC (LNC/PBMC ratio ranger: 0.54-25, median 3.4). The number of copies of unspliced viral RNA/10(5) cells was much higher in LNC than in PBMC (LNC/PBMC ratio range 65-1,159, median 435). The plasma RNA copy number, a measure of circulating cell-free virus, was correlated with the RNA copy number in PBMC, but not in LNC. A RT-PCR system specific for spliced transcripts was also used to assess the level of transcripts independent of genomic RNA. This assay also detected more signal in LNC than in PBMC. The level of spliced transcripts in LNC and PBMC correlated with the amount of full-length RNA detected by competitive PCR. A semiquantitative coculture assay with lymphoblasts from healthy donors was used to assess the infectivity of LNC as compared with PBMC in 14 patients. The minimum number of LNC necessary to cause a positive coculture ranged from 10(3) to > 10(5) (median 10(4)); the corresponding number for PBMC ranged from 10(3) to > 10(6) (median 5 x 10(5)). In most patients selected for palpable lymph nodes, LNC could be obtained by fine needle aspiration, thus allowing noninvasive monitoring of viral burden in lymphoid tissue. The present study also suggests that both T-cell subsets and viral load differ in the blood and lymphoid tissue, which raises the question of whether the study of the lymphoid tissue would yield better prognostic markers of disease course.

Differential effects of interleukin-12, interleukin-15, and interleukin-2 on human immunodeficiency virus type 1 replication in vitro

Cytokines may have clinical utility as therapeutic agents for human immunodeficiency virus type 1 (HIV-1) infection and as an adjuvant for vaccines. The effect of interleukin-12 (IL-12) and IL-15 on in vitro HIV-1 replication was investigated. IL-12 and IL-15 at doses up to 10 ng/ml had little effect on basal HIV-1 p24 antigen production by chronically HIV-infected T (ACH-2) and monocytic (U1) cell lines. For ACH-2 cells stimulated with phorbol 12-myristate 13-acetate (PMA; 50 ng/ml), IL-12 and IL-15 significantly increased p24 antigen production by 20 and 30%, respectively (n = 6). In contrast, IL-12 and IL-15 (10 ng/ml) treatment of PMA-stimulated U1 cells decreased p24 antigen production by 16 and 15%, respectively (n = 6). We next studied the effect of IL-12 and IL-15 on HIV-infected peripheral blood mononuclear cells (PBMCs). In 10 HIV-seropositive patients' PBMCs cocultured with mitogen-activated HIV-seronegative donor cells, two patterns of p24 antigen production were observed in response to IL-2: low (p24 antigen production < 10(3) pg/ml; n = 8) and high (p24 antigen production > 10(3) pg/ml; n = 2) response. For the low-response pattern, IL-12 and IL-15 increased viral replication by 97-fold and 100-fold, respectively (P = 0.05 and 0.004, respectively). For the high-response pattern, both IL-12 and IL-15 suppressed HIV replication. The effect of IL-2, IL-12, and IL-15 on acute in vitro infection by HIV-1JRCSF was also examined. IL-12 did not increase p24 antigen production above basal levels while IL-2 and IL-15 significantly enhanced p24 antigen production (by approximately 2-fold). In conclusion, IL-12 and IL-15 may have differential effects on latent and acute HIV infection, and their ability to enhance HIV production may depend on cell activation. Thus, the use of these cytokines may be dictated by the clinical state of the patient.

An NF-kappaB site in the 5'-untranslated leader region of the human immunodeficiency virus type 1 enhances the viral expression in response to NF-kappaB-activating stimuli

The 5'-untranslated leader region of human immunodeficiency virus, type 1 (HIV-1), includes a complex array of putative regulatory elements whose role in the viral expression is not completely understood. Here we demonstrate the presence of an NF-kappaB-responsive element in the trans-activation response (TAR) region of HIV-1 that confers the full induction of HIV-1 long terminal repeat (LTR) in response to NF-kappaB-activating stimuli, such as DNA alkylating agents, phorbol 12-myristate 13-acetate, and tumor necrosis factor-alpha. The TAR NF-kappaB site GGGAGCTCTC spans from positions +31 to +40 and cooperates with the NF-kappaB enhancer upstream of the TATA box in the NF-kappaB-mediated induction of HIV-1 LTR. The conclusion stems from the following observations: (i) deletion of the two NF-kappaB sites upstream of the TATA box reduces, but does not abolish, the HIV-1 LTR activation by NF-kappaB inducers; (ii) deletion or base pair substitutions of the TAR NF-kappaB site significantly reduce the HIV-1 LTR activation by NF-kappaB inducers; (iii) deletions of both the NF-kappaB sites upstream of the TATA box and the TAR NF-kappaB site abolish the activation of HIV-1 LTR in response to NF-kappaB inducers. Moreover, the p50 p65 NF-kappaB complex binds to the TAR NF-kappaB sequence and trans-activates the TAR NF-kappaB-directed expression. The identification of an additional NF-kappaB site in the HIV-1 LTR points to the relevance of NF-kappaB factors in the HIV-1 life cycle.

Lymphoproliferation assays in cattle naturally infected with bovine leukaemia virus (BLV) and bovine immunodeficiency-like virus (BIV)

Experiments were designed to evaluate the effect of BLV on mitogen-stimulated peripheral blood mononuclear cells (PBMC) from naturally infected cattle. BIV was also taken into consideration due to a recent report showing that in Costa Rica, most of the BLV-infected animals are also seropositive for BIV. The methodology was based on a non-radioactive technique to determine lymphoproliferation. A colorimetric assay using XTT (formazan salt) to measure cell multiplication was adapted for bovine PBMC. ELISA and Western blotting were used to determine the serologic status of the cattle. PCR was only available for BIV detection. Our results show clearly that, dually-infected cattle (BIV-BLV) have reduced lymphoproliferative responses to the mitogen Con A. Haematological abnormalities associated with viral infections were also observed, specially leukocytosis and lymphocytosis. Cows with lymphosarcomas are severely affected. The specific antibody response to different viral proteins could not be associated with the suppressive status of the animals. Due to the high rate of dual infections observed in Costa Rica, these results are not sufficient to clarify which virus is responsible for the suppressive activity, if one or both viruses are necessary, or if they act synergistically.

Mass in the post nasal space and acquired immune deficiency syndrome

We report a case of previously undiagnosed acquired immunodeficiency syndrome (AIDS) who had a mass in the post-nasal space causing almost complete nasal obstruction. Histology showed both respiratory and squamous epithelium covering an active chronic inflammatory infiltrate. Lymphoma, Kaposi's sarcoma and infiltrative fungal sinusitis were excluded. There was no evidence of the common viruses associated with lesions in AIDS. Unlike adenoid hypertrophy, the lesion was an exuberant growth with an additional chronic inflammatory reaction due to ulceration of the surface epithelium.

Medical UV exposures and HIV activation

This paper presents the first attempt to evaluate the potential of clinical UV exposures to induce the human immunodeficiency (HIV) promoter and, thus, to upregulate HIV growth in those skin cells that are directly affected by the exposure. Using the data for HIV promoter activation in vitro, we computed UVB and psoralen plus UVA (PUVA) doses that produce 50% of the maximal promoter activation (AD50). Then, using (a) literature data for UV transmittance in the human skin, (b) a composite action spectrum for HIV promoter and pyrimidine dimer induction by UVB and (c) an action spectrum for DNA synthesis inhibition by PUVA, we estimated the distribution of medical UVB and PUVA doses in the skin. This allowed us to estimate how deep into the skin the HIV-activating doses might penetrate in an initial and an advanced stage of UVB or PUVA therapy. Such analysis was done for normal type II skin and for single exposures. The results allow us to predict where in the skin the HIV promoter may be induced by selected small and large therapeutic UVB or PUVA doses. To accommodate changes in skin topography due to disease and UV therapy, our considerations would require further refinements. For UVB we found that, when the incident dose on the surface of the skin is 500 J/m2 (290-320 nm) (initial stage of the therapy), the dose producing 50% of the maximal HIV promoter activation (ADUVB50) is limited to the stratum corneum. However, with an incident dose of 5000 J/m2 (an advanced stage of the therapy), ADUVB50) may be delivered as far as the living cells of the epidermis and even to some parts of the upper dermis. For PUVA we found that, when the incident UVA doses are 25 or 100 kJ/m2 (320-400 nm) (an initial and an advanced stage of therapy, respectively), and the 8-methoxypsoralen concentration in the blood is 0.1 microgram/mL (the desired level), the combined doses to the mid epidermis (and some areas of the upper dermis) are well below the 50% HIV promoter-activating PUVA dose (ADPUVA50). Only under the worst scenario conditions, i.e. an exceptionally high drug concentration in the patient's tissues and localization of HIV in the nearest proximity to the skin surface, would the combined PUVA dose expected during photochemotherapy exceed ADPUVA50. These results suggest that the probability of HIV activation in the epidermis by direct mechanisms is higher for UVB than for PUVA treatment. However, complexities of the UV-inducible HIV activation and immunomodulatory phenomena are such that our results by themselves should not be taken as an indication that UVB therapy carries a higher risk than PUVA therapy when administered to HIV-infected patients.

Immediate immunosuppression caused by acute HIV-1 infection: a fulminant multisystemic disease 2 days post infection

A healthy 19-year-old woman had vaginal intercourse on a single occasion with an HIV-1 positive male from Gambia. Two days later she developed an acute HIV infection presenting as a fulminant multisystem disease that lasted for 35 hospital days and included: immediate immunosuppression with extreme CD4+ lymphocytopenia and combined with CD8+ lymphocytosis, neutropenia and hypogammaglobulinemia; intermittent spiking fever; pneumonitis; hepatitis; changing skin rashes; peripheral neuropathy with myopathy, and panencephalitis. P24 antigen was detected by Western blot on day 23 and seroconversion was detected by ELISA on day 25. Cultured lymphocytes from peripheral blood and cerebrospinal fluid grew HIV-1.

Pattern of gp120 sequence divergence linked to a lack of clinical progression in human immunodeficiency virus type 1 infection

Differential rates of AIDS development and/or T4 lymphocyte depletion in HIV-1-infected individuals remain unexplained. The hypothesis that qualitative differences in selection pressure in vivo may account for different rates of disease progression was addressed in nine eligible study participants from a cohort of 315 homosexual men who have been followed since 1985. Disproportionately fewer changes in variable regions and more in C3 of gp12O were found to be significantly associated with slower disease progression. Our finding provides the first example to demonstrate that differential selection pressure related to the emergence of HIV-1 variants is associated with long term nonprogression. Candidate vaccines that elicit strong selection pressure on C3 of gp120 are likely to provide better protection than those targeting variable regions.

Targeting human immunodeficiency virus type 1 reverse transcriptase by intracellular expression of single-chain variable fragments to inhibit early stages of the viral life cycle

Novel molecular approaches to inhibit human immunodeficiency virus type 1 (HIV-1) infection have received increasing attention because of the lack of effective antiviral drug therapies in vivo. We now demonstrate that cells can be intracellularly immunized by cytoplasmic expression of single-chain variable antibody fragments (SFv) which bind to the HIV-1 reverse transcriptase (RT) enzyme. The expression of anti-RT SFv in T-lymphocytic cells specifically neutralizes the RT activity in the preintegration stage and affects the reverse transcription process, an early event of the HIV-1 life cycle. Blocking the virus at these early stages dramatically decreased HIV-1 propagation, as well as the HIV-1-induced cytopathic effects in susceptible human T lymphocytes, by impeding the formation of the proviral DNA. These data also demonstrate that intracellular, complete SFvs may gain access to viral proteins of the HIV-1 preintegration complex. These SFvs will provide a tool with which to better understand the molecular mechanisms involved in restricting viral replication in HIV-1-infected cells.

A longitudinal study of lymphocyte subsets in a cohort of cats naturally-infected with feline immunodeficiency virus

Despite the potential of feline immunodeficiency virus (FIV) as an animal model for human immunodeficiency virus (HIV) studies, the long term effects of naturally-occurring infection have not been determined. HIV infection causes an ongoing deterioration in immune function which directly correlates with disease, in particular acquired immunodeficiency syndrome (AIDS). However, it is not known whether FIV-induced immunosuppression is progressive or related to the clinical condition. This study examined changes in lymphocyte subset numbers of serial samples, taken from cohorts of FIV-positive and FIV-negative cats over and 18-month period. FIV-positive cats were clinically staged as asymptomatic carriers (AC) or cats with AIDS-related complex (ARC), and FIV-negative cats matched and staged on the basis of similar diseases. During the course of the study, 4 FIV-positive cats developed AIDS, classed as the terminal stage of infection. There were no significant differences in the mean absolute numbers of any lymphocyte subset between the onset (t0) and the completion (t18) of the study. Similarly there were no significant changes in subset numbers during the 18 months preceding the development of AIDS. While the study period was brief and the sample sizes small, it is postulated that FIV infection in Australia may not necessarily cause progressive immunodeficiency and that FIV-induced immunosuppression (as measured by subset analysis) may not be well correlated with the clinical status of the infected cat.

Fluctuations in steady state level of genomic HIV-1 RNA and replication intermediates related to disease progression rate

Steady state levels of HIV-1 genomic RNA and unintegrated circular DNA fluctuate in the course of HIV-1 infection. Genomic RNA in serum was detected using the NASBA technique and the amount of circular DNA was assessed by PCR. Quantification was done by competitive techniques using co-amplification of internal standards. Within the Amsterdam Cohort Studies it was possible to distinguish rapid progressors, intermediate progressors, slow progressors and non-progressors. Rapid progressors show persistently high viral RNA loads from seroconversion on, while all other HIV-1-infected individuals show a steady decline after seroconversion. Subsequent rises in viral RNA levels herald disease progression in later stages of infection. Unintegrated circular DNA shows similar, but somewhat delayed kinetics. These results indicate that the distribution of AIDS and the average length of the symptom-free period in an HIV-1-infected host population is determined by the steady state levels of genomic RNA and of replication intermediates that are produced by a particular HIV-1 virus population in the average seropositive individual.

Longitudinal study of adrenal steroids in a cohort of HIV-infected patients with hemophilia

The objective of the study was to relate plasma dehydroepiandrosterone sulfate (DHEA-S) concentrations to the progression of HIV infection in individual HIV-infected men with hemophilia and to obtain information on the cause of DH EA-S alterations. Blood samples were obtained from 16 men with hemophilia; in 9 men serial samples were available for up to 11 years after HIV-1 infection. Control samples were obtained from men of comparable ages without hemophilia or HIV infection. Measurements were made of CD4+ cell counts, plasma adrenocorticotropic hormone (ACTH), cortisol, DHEA, DHEA-S, and prolactin. Before HIV infection, men with hemophilia had significantly lower plasma levels of DHEA-S than control men. After infection, 3 of 9 subjects studied serially had little or no change in plasma DHEA-S levels or in CD4+ cell counts over 11 years. Four of the 9 i n whom AIDS developed had progressive decreases in plasma DHEA-S concentrations that, in some cases, preceded a precipitous fall in CD4+ cell counts. Major decreases in plasma DHEA-S levels before falls in CD4+ counts were observed in 2 ot her subjects who had other severe illnesses. None of the decreases in DHEA-S levels were associated with decreased concentrations of plasma cortisol, ACTH, or prolactin. We conclude that plasma DHEA-S is an indicator of general health rather than a specific indicator for progression of HIV. The decrease in plasma DHEA-S is not related to ACTH stimulation of the adrenal gland or to cortisol secretion, but it may be related to cytokines that can inhibit 17-hydroxylation of DH EA-S precursors.

Acquired immune deficiency syndrome caused by hyperimmunity

Normal immunocytes including T and B cells are equilibrated by a reciprocal attacking mechanism called a network. Continuous disequilibrium of this network results in general immunodeficiency with oligo- and polyclonal hyperimmunity, for example, T-cell activation due to spontaneous reticuloendotheliosis, paraneoplastic autoimmune syndromes, and human immunodeficiency virus infection. In these disorders, reciprocal self-reactivity, including autologous graft-versus-host reaction, plays a role in the immunodeficiency. A priori self-targeting immunity is a key mechanism to explain autoimmunity in the acquired immunodeficiency syndrome. In the treatment of the immunodeficiency due to hyperimmunity, I propose immunological suppression by agents and reconstitution of the network by bone-marrow transplantation.

Comparative analysis of apoptosis in HIV-infected humans and chimpanzees: relation with lymphocyte activation

Programmed-cell death (apoptosis) is a physiological cell death process which appears exacerbated in peripheral lymphocytes from HIV-infected persons. On the contrary, a barely detectable level of apoptosis is found in peripheral lymphocytes from HIV-infected chimpanzees, which support long-term productive infection without developing AIDS. In the present study, we analyzed the relationship between apoptosis and the general state of immune activation in PBMC from HIV-infected humans and chimpanzees. In addition, apoptosis control in the CD8 subset by the bcl-2 proto-oncogene was compared in both human and chimpanzees. Taken together, the results indicate that the degree of apoptosis correlates with the state of activation of the immune system and this observation together with the finding that apoptosis concerns all lymphocyte subsets indicates that the low level of apoptosis in HIV-infected chimpanzees is related to the lack of immune activation in this nonpathogenic model.

Nosocomial colonization and infection in persons infected with human immunodeficiency virus

Nosocomial infections appear to be increased in patients with acquired immunodeficiency syndrome (AIDS), compared to individuals with asymptomatic infection due to human immunodeficiency virus (HIV). Risk factors for bacterial colonization and infection include immunosuppression, prior treatment with some antibiotics, increased hospitalizations with longer lengths of stay, greater exposure to invasive devices such as indwelling intravenous or urinary catheters, and the degree of immunosuppression. Data suggest that other infectious agents such as Pneumocystis carinii, Mycobacterium tuberculosis, Mycobacterium avium complex, and Cryptosporidium may be acquired in healthcare facilities. Diagnosis and management of nosocomial infections in HIV-infected persons may be complicated by an atypical presentation, increased rates of relapse following treatment, presence of multiple infections, and early discharge from the inpatient setting. Accurate assessment of nosocomial infections and outbreaks in the hospital is complicated by limited data on the risk of transmission of both traditional and unusual pathogens in this population. Furthermore, some patients may acquire nosocomial pathogens during their initial hospitalization and present later with infections that normally would be classified as community acquired. Therefore, there probably is an underestimation of current nosocomial infection rates, and perhaps "hospital-associated" or "healthcare-facility-associated" might be more accurate terms for these infections.

Lymphoid changes of the nasopharyngeal and palatine tonsils that are indicative of human immunodeficiency virus infection. A clinicopathologic study of 12 cases

We report 12 cases in which the histomorphologic changes of the nasopharyngeal tonsils (adenoids) or palatine tonsils suggest infection with the human immunodeficiency virus (HIV). The patients included 10 men and two women, aged 20 to 42 years (median, 33 years). The clinical presentation included airway obstruction, pharyngitis, fever, and a tonsillar or adenoidal mass lesion. Histologic evaluation of the excised adenoids or tonsils in 10 of the cases demonstrated a spectrum of changes including florid follicular hyperplasia, follicle lysis, attenuated mantle zone, and the presence of multinucleated giant cells (MGC). The latter characteristically localized adjacent to the surface or tonsillar crypt epithelium. Two of the 12 cases showed marked lymphoid depletion with absent germinal centers, plasmacytosis, and stromal vascular proliferation. Immunohistochemical evaluation for HIV p24 core protein showed reactivity in 10 of 12 cases localized to follicular dendritic cell network (FDC), the MGC, scattered interfollicular lymphoid cells, and cells identified within the surface or crypt epithelium. Localization of viral RNA by in situ hybridization paralleled the HIV p24 immunohistochemical findings. Additional significant findings included the presence of both CD-68 and S-100 protein in the MGC and the presence of S-100 protein in dendritic cells. Other than HIV, no microorganisms were identified. At the time of presentation, eight patients were not known to be a risk for HIV infection, nor were they known to be HIV infected or suffering from AIDS. In these patients, HIV infection was suspected on the basis of the histologic changes seen in the resected tonsillar and adenoidal tissue. Serologic evaluation (by enzyme-linked immunosorbent assay), confirmed the presence of HIV infection. Our findings suggest the possibility of HIV dissemination through the upper aero-digestive tract mucosa via target cells, such as intraepithelial dendritic cells, submucosal macrophages, and T-lymphocytes. Subsequent presentation of viral antigens to the tonsillar and adenoidal lymphoid tissues results in enlargement of these structures that clinically may simulate a neoplastic proliferation but causes histomorphologic changes that are highly suspicious for HIV infection even in asymptomatic HIV-positive patients.

Kinetics of cytokine expression during primary human immunodeficiency virus type 1 infection

In the present study, we have determined the kinetics of constitutive expression of a panel of cytokines [interleukin (IL) 2, IL-4, IL-6, IL-10, interferon gamma (IFN-gamma), and tumor necrosis factor alpha (TNF-alpha)] in sequential peripheral blood mononuclear cell samples from nine individuals with primary human immunodeficiency virus infection. Expression of IL-2 and IL-4 was barely detected in peripheral blood mononuclear cells. However, substantial levels of IL-2 expression were found in mononuclear cells isolated from lymph node. Expression of IL-6 was detected in only three of nine patients, and IL-6 expression was observed when transition from the acute to the chronic phase had already occurred. Expression of IL-10 and TNF-alpha was consistently observed in all patients tested, and levels of both cytokines were either stable or progressively increased over time. Similar to IL-10 and TNF-alpha, IFN-gamma expression was detected in all patients; however, in five of nine patients, IFN-gamma expression peaked very early during primary infection. The early peak in IFN-gamma expression coincided with oligoclonal expansions of CD8+ T cells in five of six patients, and CD8+ T cells mostly accounted for the expression of this cytokine. These results indicate that high levels of expression of proinflammatory cytokines are associated with primary infection and that the cytokine response during this phase of infection is strongly influenced by oligoclonal expansions of CD8+ T cells.

Immunological memory and protective immunity: understanding their relation

The immune system can remember, sometimes for a lifetime, the identity of a pathogen. Understanding how this is accomplished has fascinated immunologists and microbiologists for many years, but there is still considerable debate regarding the mechanisms by which long-term immunity is maintained. Some of the controversy stems from a failure to distinguish between effector and memory cells and to define their roles in conferring protection against disease. Here the current understanding of the cellular basis of immune memory is reviewed and the relative contributions made to protective immunity by memory and effector T and B cells are examined.

In vitro lymphocyte blastogenic responses and cytokine production in sickle cell disease patients with acute pneumonia

BACKGROUND

Pulmonary infections continue to be a major cause of morbidity and mortality in patients with sickle cell disease (SCD).

METHODS

In this study cell-mediated immunity in vitro was evaluated in 62 SCD patients (62 steady state and 16 with acute pneumonia) and compared with 44 normal controls (30 healthy and 14 with acute pneumonia). Lymphocyte blastogenic responses to phytohemagglutinin, tetanus toxoid and Candida albicans antigen were assessed in all subjects. In addition production of tumor necrosis factor, alpha- and gamma-interferon (IFN) were assayed.

RESULTS

The results revealed comparable blastogenic responses to all three stimuli in all subjects except SCD patients with pneumonia. This group showed poor responses to all stimuli. The mean counts per minute were decreased 65 to 90% when compared with the other patients. Cytokine production of IFN-alpha and TNF was equivalent in all subjects. Conversely IFN-gamma production in both SCD groups, steady state (35 +/- 6 U/ml) and SCD with pneumonia (14 +/- 6 U/ml), was significantly decreased when compared with those in normal healthy controls (65 +/- 14 U/ml) and with pneumonia (48 +/- 17 U/ml). On analysis of individual titers 15 of 62 (24%) steady state and 10 of 16 (63%) SCD patients with pneumonia were deficient in IFN-gamma production in vitro.

CONCLUSIONS

Acute pulmonary infections seem to have a profound effect on cell-mediated immunity in SCD. IFN-gamma deficiency, along with quantitative and qualitative T cell abnormalities, may represent significant factors to explain the frequent and severe infections seen in SCD.

Rabies superantigen as a Vbeta T-dependent adjuvant

Recently we reported evidence that nucleocapsid (NC) of rabies virus is a Vbeta8-specific exogenous superantigen (SAg) in humans and a Vbeta6-specific SAg in BALB/c mice. NC was also found to stimulate rabies vaccination by enhancing the rabies neutralizing antibody response. In this study, we tested the hypothesis that the stimulating effect of NC and its SAg properties are linked. To do this, we studied the effect of rabies SAg on the immune response to an unrelated antigen, the influenza virus, and compared the response in two congenic strains of mice, BALB/c and BALB/D2. BALB/c mice are rabies SAg responsive, whereas BALB/D2 mice are not responsive to SAg activation by rabies NC because they lack the SAg recognition element, the Vbeta6 T cell receptor. In BALB/c mice, coinjection of rabies SAg with inactivated influenza virus resulted in a rapid and long-term increase in (a) the titres of influenza virus-specific antibodies (IgG and IgM), including protective hemagglutination-inhibiting antibodies, (b) antigen-specific proliferation and, (c) IL-2 and IL-4 secretion by lymph node lymphocytes, when compared to mice that received influenza virus only. In contrast, in BALB/D2 mice, neither antibody nor lymphocyte responses were stimulated. Moreover, during establishment of the primary response, the increase in influenza-primed T cells was mainly restricted to those bearing a Vbeta6 TCR. These data establish that rabies SAg can stimulate both T and B cell-specific responses to an unrelated antigen, depending on expression of the SAg target (Vbeta6 T lymphocytes). This is the first report linking NC adjuvant properties with its SAg mechanism.

The use of two measures of health-related quality of life in HIV-infected individuals: a cross-sectional comparison

Two measures of health-related quality of life in 65 HIV-infected individuals were compared in a cross-sectional design. The Quality of Well-Being Scale (QWB) results in a single score ranging from death to perfect health. The MOS-HIV Health Survey (MOS-HIV, 34-item version) gives scores in 11 dimensions. The QWB score distinguished subjects with AIDS from those who were asymptomatic (p = 0.027). For the seven multi-item scales of the MOS-HIV, Cronbach's alpha ranged from 0.85-0.95, indicating good internal consistency reliability. Clinical HIV-infection status was significantly associated with the dimensions of Overall Health (p = 0.002), Role Function (p = 0.022), Social Function (p = 0.037), Energy/Fatigue (p = 0.027) and Health Distress (p = 0.025). All eleven dimensions of the MOS-HIV were significantly correlated with the QWB score (Spearman's coefficient = 0.405-0.670; for all, p < 0.01) and the QWB score could be predicted from the MOS-HIV dimension scores using multiple regression. The QWB and the MOS-HIV may be useful in assessing health-related quality of life in patients infected with HIV.

The expression of CD8 on B lymphocytes in HIV-infected individuals

In HIV-1 infected individuals the CD8 + T lymphocyte population is markedly activated as reflected by increased expression of the CD38 and CD45RO activation markers and elevated serum levels of soluble CD8 antigen. We have previously shown that in vitro activation of peripheral blood lymphocytes results in the appearance of T cell markers on B cells. In the present study B lymphocytes from HIV-1-infected individuals were tested for the expression of the CD8 T cell antigen, using F(ab')2 fragments of antibodies against the CD8 and CD19 antigens. The proportion of CD19 + B cells which co-expressed CD8 was significantly elevated among 55 HIV-infected individuals (7.20 +/- 1.24%, mean +/- S.E.) as compared with among 22 normal controls (3.32 +/- 0.70%). The proportion of CD4 + cells decreased significantly in HIV-infected individuals in accordance with the progression of the infection, but no significant change in the level of CD8 + CD19 + B cells was seen in different stages of the disease. In contrast, the proportion of CD8 + B cells showed a significant correlation with the proportion of CD8 + cells.

Cytokines and soluble receptor changes in the transition from primary to early chronic HIV type 1 infection

We studied determinants of chronic inflammation and/or immune activation in plasma from patients in the transition from primary to early chronic HIV-1 infection. The following parameters were estimated in seven patients over time: plasma concentrations of soluble CD8 (sCD8), tumor necrosis factor alpha (TNF-alpha), soluble TNF receptor type II (sTNFRII), interleukin 6 (IL-6), soluble IL-6 receptor (sIL6R), IL-10, transforming growth factor beta1 (TGF-beta1), along with CD4- and CD8-positive T cell counts, p24 antigenemia, and clinical evaluation. Results showed that concentrations of sCD8, TNF-alpha, and sTNFRII, and peripheral CD8-positive lymphocyte counts, were significantly increased in patients, compared to HIV-negative controls, and showed a trend toward normal values over time. Levels of IL6, sIL6R, IL-10, and TGF-beta1 did not differ from those of controls and did not change over time. Heterogeneity was observed among the patients in terms of CD4-positive T cell depletion, levels of sCD8, concentrations of TNF-alpha/sTNFRII, and clinical outcome. These data indicate that in the transition phase from primary acute to chronic and asymptomatic infection the host immune activation in response to the virus is highly heterogeneous and that the sustained rise in TNF-alpha and its receptor may represent an important therapeutic target in early disease. The persistence of a state of chronic inflammation and/or immune activation could influence the progression of disease independently from CD4-positive T cell counts.

Interleukin-2 and human immunodeficiency virus infection: pathogenic mechanisms and potential for immunologic enhancement

A hallmark of human immunodeficiency virus (HIV) infection is the progressive loss of CD4+ T lymphocytes; however, qualitative defects in immune responses occur prior to the precipitous drop CD4+ T cell numbers. One of the first immunologic defects to be described in HIV-infected individuals is a deficiency in interleukin (IL)-2 production. The addition of IL-2 in vitro to cultures of mononuclear cells from HIV-infected individuals partially or completely restored certain defective cellular immune responses. However, production of or addition of IL-2 has also been associated with increased viral replication in infected T cells. These observations underscore the pernicious correlation between immune activation and HIV replication. However, recent in vitro and in vivo studies have provided promising preliminary results suggesting that, at least at certain stages of disease, the benefits of IL-2 mediated immune enhancement may outweigh or override the inductive effects of this cytokine on HIV production.

Preliminary results in HIV-1-infected patients treated with transfer factor (TF) and zidovudine (ZDV)

The efficiency of HIV-1 specific transfer factor (TF) administration, combined with Zidovudine (ZDV), in asymptomatic persistent generalised lymphadenopaty, or AIDS related complex (ARC) patients was evaluated. Twenty patients were randomly assigned to receive only ZDV (1st group) or ZDV together with HIV-1-specific TF (2nd group). HIV-1-specific TF was administered orally at 2 x 10(7) cell equivalent daily for 15 days, and thereafter once a week for up to 6 months. There were no significant differences between the two groups in clinical evolution, red blood cells, haemoglobin, lymphocytes, CD20 subset, transaminases, beta-2-microglobulin, p24 antigen. White blood cells, CD8 lymphocytes as well as IL-2 levels increased in the second group, while the CD4 subset increased in the first group. The combination treatment with ZDV and TF appeared to be safe and well tolerated. Furthermore, levels of serum cytokines were investigated in 10 patients (8 asymptomatic and 2 ARC) treated with ZDV, and compared with 5 patients of the 2nd group (3 asymptomatic and 2 ARC) treated with ZDV plus HIV-1-specific TF. Peripheral lymphocytes, CD4, CD8 subsets, IL-2, TNF alpha, IL-6, p24 antigen, IL-2 soluble lymphocyte receptors (sR), CD4sR, CD8sR and beta-2-microglobulin were evaluated at the baseline and at the 3rd month. The CD4 subset was not significantly different in the two groups, whilst IL-2 increased in the 2nd group receiving ZDV plus TF, suggesting an activation of the Th1 secretion pattern.

Practice parameters for the diagnosis and management of immunodeficiency. The Clinical and Laboratory Immunology Committee of the American Academy of Allergy, Asthma, and Immunology (CLIC-AAAAI)

In this brief review, only the most useful immunologic tests available for defining host defects that lead to susceptibility to infection have been emphasized. It should be pointed out that those evaluations and tests ordered by the physician will rule out the vast majority of the currently recognized defects. Finally, it is important that any patients identified as abnormal by these screening tests be characterized as fully as possible in centers specializing in these diseases before therapy is initiated, since what may appear to be a simple diagnosis on the surface may be an indicator of more complex underlying problems.

Changes in membrane enzymes and glycosphingolipids in lymphocytes from HIV-1--infected and noninfected intravenous drug users

The amounts of cell-surface glycosphingolipids and plasma membrane enzymes produced on the peripheral blood mononuclear cells (PBMNCs) isolated from 101 intravenous drug users (IDUs), of whom 91 were HIV-1 seropositive, were examined. Seronegative IDUs and age-matched healthy donors served as controls. The numbers of circulating CD3+, CD4+, and CD8+ T lymphocytes decreased during the advanced stages of the infection. There were also fewer CD4+ T-helper cells in HIV-1--seronegative IDU drug addicts. PBMNCs from HIV-1--seropositive subjects had abnormal surface enzyme kinetics. The phospholipase C had two pH optima, whereas the enzyme on normal cells has only one. The specific activity in cells from AIDS subjects was 4 times lower than that in normal PBMNCs. 5'-Nucleotidase showed a similar trend, whereas neutral endopeptidase activity did not correlate with the amounts of surface common acute lymphoblastic leukemia antigen (CALLA). These enzyme activities were decreased in HIV-seronegative IDUs. The subcellular distribution of enzymes and the profile of surface glycosphingolipids were also markedly changed, indicating the profound alterations in the membranes of PBMNCs from HIV-1--seropositive IDUs. These data suggest that intravenous drug use compromises the biochemical and structural integrity of the membrane surface of PBMNCs even before the onset of HIV.

The intrinsic rate of increase of HIV/AIDS: epidemiological and evolutionary implications

A method derived from demographic theory is presented for modeling the epidemiology of an infectious disease. For long-term infections, this method better accounts for host variation in survival and transmission rates than classical compartment models. Examples of the applications of this method focus on a single long-term infectious disease, HIV/AIDS. The method is employed to examine (1) how changes in transmission rates during different stages of infection affect the rate of spread of HIV/AIDS both in wholly susceptible populations and in populations where the number of potential hosts is limited, (2) the way the relative frequencies of the different stages of infection vary over time, (3) how the rate at which the epidemic is growing (or diminishing) affects the fraction of HIV-infected individuals who manifest the symptoms of AIDS, (4) the effect of treatment on the rate of spread of HIV, and (5) the potential effects of natural selection on the virulence of HIV.

Reference ranges and sources of variability of CD4 counts in HIV-seronegative women and men

BACKGROUND

CD4 lymphocyte counts are used to monitor immune status in HIV disease. An understanding of the variability of CD4 counts which occurs in the absence of HIV infection is essential to their interpretation. The sources and degree of such variability have not been extensively studied.

OBJECTIVES

To establish reference ranges for CD4 counts in HIV-seronegative women and heterosexual men attending a genitourinary medicine (GUM) clinic, and to identify possible differences according to gender and cigarette smoking and, in women, any effect of the menstrual cycle, oral contraceptive use and cigarette smoking.

DESIGN

Female and heterosexual male patients attending a GUM clinic and requesting an HIV-antibody test were recruited prospectively. Results from an earlier study of CD4 counts in homosexual men were available for comparison.

METHODS

Lymphocyte subpopulation analysis on whole blood by flow cytometry.

RESULTS

The absolute CD4 count and percentage of CD4 cells (CD4%) were significantly higher in women (n = 195) than heterosexual men (n = 91) [difference between the means 111 x 106/1 (95% CI 41, 180) and 3.1% (1.30, 4.88)]. The absolute CD4 count and CD4% were also significantly higher in smokers (n = 143) than non-smokers (n = 140) [difference 143 (79, 207) and 2.1% (0.43, 3.81)]. Reference ranges for absolute CD4 counts (geometric mean +/- 2SD) were calculated on log transformed data as follows; female smokers 490-1610, female non-smokers 430-1350, heterosexual male smokers 380-1600, heterosexual male non-smokers 330-1280. Among other variables examined, combined oral contraceptive pill use was associated with a trend towards a lower absolute CD4 count. Changes were seen in CD4% with the menstrual cycle. CD4 counts and CD4% did not differ significantly between heterosexual men and homosexual men (n = 45).

CONCLUSION

There is a significant gender and smoking effect on CD4 counts. The effects of oral contraceptive use and the menstrual cycle warrant further investigation.

Quantification of low levels of human immunodeficiency virus (HIV) type 1 RNA in P24 antigen-negative, asymptomatic, HIV-positive patients by PCR

A nested PCR was used to quantify small numbers of human immunodeficiency virus (HIV) type 1 (HIV-1) RNA particles in the serum specimens of 26 p24 antigen-negative, asymptomatic, HIV-positive patients undergoing antiretroviral therapy. Fifteen patients received zidovudine (ZDV) and alpha interferon, and 11 patients received ZDV monotherapy. After PCR, the amounts of RNA were quantified by comparing the endpoint dilutions of serum samples with a standard curve with known amounts of viral particles. Before the beginning of the antiviral therapy, HIV-1 RNA was detected in 92% of the patients. After treatment, a fall in the number of viral particles was detected in patients receiving combination therapy (mean titers +/- standard errors of the means, 3,617 +/- 756 pretherapy versus 1,800 +/- 845 posttherapy; P < 0.05) and in patients receiving monotherapy (3,763 +/- 642 pretherapy versus 1,353 +/- 394 posttherapy; P < 0.05). Our results indicate that PCR with nested primers may be useful for assessing the changes in viremia in HIV-positive patients with low viral load undergoing antiviral therapy.

Human antibody variable region gene usage in HIV-1 infection

Human antibody variable region gene usage during human immunodeficiency virus type 1 (HIV-1) infection is examined in the following review, and several hypotheses are presented to account for the distinct patterns of antibody gene expression associated with infection. Evidence supporting qualitatively biased antibody gene expression has been derived from analysis of the human humoral immune response by isoelectric focusing (IEF) and serological and molecular studies of immunoglobulin (Ig) from different lymphoid compartments of HIV-1-infected patients. Preferential usage of heavy-chain variable region (VH) gene families 1 and 4 is supported by serological studies of serum Ig and molecular characterization of anti-HIV-1 human monoclonal antibodies derived from infected patients. Negative biases against VH3 family gene usage are detected by polymerase chain reaction (PCR) studies of peripheral blood lymphocytes from AIDS patients but not by combinatorial phage display library techniques. Biased antibody gene usage and expression during HIV-1 infection may be related to HIV-1 pathogenesis by limiting the available HIV-1 neutralizing repertoire. Further molecular characterization of anti-HIV-1 antibodies and in vivo expression of V-region genes during HIV-1 infection should provide important information regarding antibody gene expression and its relationship to HIV-1 pathogenesis.

Validation of a quantitative RNA PCR assay for HIV-1 in human plasma

A quantitative human immunodeficiency virus type 1 (HIV-1) RNA polymerase chain reaction assay has been validated analytically and clinically in > 13,000 samples. The assay is highly reproducible with intra- and inter-assay precision of 16% and 19%, respectively. In 1,542 of 1,548 subjects with CD4+ counts of 0-500 cells per mm3, viral RNA levels were quantifiable and ranged from approximately 3,000-52,200,000 copies per milliliter. Median plasma HIV-1 RNA values were inversely proportional to CD4+ counts from 0-400 cells per mm3. When patients were off antiretroviral therapies for approximately 14 days prior to the initial baseline RNA PCR evaluation, the mean variance between the two baseline values was 23% (0.1 log). Of these patients, 95% had a sufficient plasma viral load to quantitate a 10-fold (1 log) diminution in viral load caused by antiviral therapy. In contrast, only 20% and 45% of these subjects had sufficient p24 and ICD p24 levels to detect a 50% diminution in circulating virus. The high precision and reproducibility of this quantitative RNA PCR assay provide an enhanced means of evaluating therapeutic drug regimens for HIV-1.

Virus-induced immunopathology

Several viruses cause damage to the tissue by immunopathological mechanisms. This chapter presents the principal examples of immunopathogenesis caused by the viruses, accompanied by speculations about its management. The most common mechanism of lesion development in virus induced immunopathology involves T cells. Usually, it seems that when CD8+ T cells act as the controlling cell type, lesions are acute and the outcome is decided quickly. The classic example is provided by LCM in mice. The newest candidate may turn out to be SNV infection in humans. Lesions orchestrated primarily by CD4+ T cells can be either acute or long-lasting. Curiously, in the LCMV example, if CD8+ T cells are removed from the scene, immunopathological responses may still occur and these involve CD4+ T cells. Such responses are far more chronic and of lower grade than those mediated by CD8+ T lymphocytes. One possible sequel to chronic inflammatory responses to viruses is that autoreactive inflammatory reactions are initiated and an autoimmune disease occurs. The adage that an ounce of prevention is worth a pound of cure is certainly true in the field of viral pathogenesis. Preventing viral infection or manipulating immune processes during the initial phases of infection is far more successful than attempting to counteract pathological events once underway.

Simian immunodeficiency virus variants: threat of new lentiviruses

Infection in humans with the lentivirus HIV-1 typically results in the development of a chronic disease state characterized by the slow decline of CD4+ lymphocytes, the development of immunosuppression, and the development of opportunistic infections, ultimately leading to death. Although the average course of disease runs approximately 10 years, shorter and longer progression times have been noted. These alterations are presumed to be, at least partially, a factor of viral variation. The simian immunodeficiency viruses (SIVs) are the nonhuman primate counterparts to HIV. Several of these isolates, including SIV from sooty mangabey monkeys, induce a remarkably similar disease in Asian macaques. Recently, variants of SIV from sooty mangabey monkeys and SIV from African green monkeys have been described, which are increasingly more pathogenic. As in HIV-1 infections, this is probably due to genetic variation. On the basis of these findings, atypical viruses with tremendous pathogenic potential can arise from apathogenic or moderately pathogenic viruses.