Regression of AIDS-related Kaposi's sarcoma following combined antiretroviral treatment

The aim of the study was to assess regression of Kaposi's sarcoma (KS) in AIDS patients in Argentina. Eighteen male AIDS patients with human immunodeficiency virus (HIV)-associated Kaposi's sarcoma at different clinical stages received KS specific treatment and/or anti-retroviral therapy. Triple anti-retroviral therapy was given to most of the patients with the exception of four who received zidovudine (ZDV) in combination with another nucleoside analogue but no protease inhibitors. Plasma viral load and CD4+ T lymphocyte number were measured in two blood samples (before and after treatment). Complete remission was found in all patients (five) at KS stage I, three out of eight patients at stage II but in none at stages III and IV. Two out of three patients at KS stage IV did not respond to treatments at all. Three patients at KS stages I and II showed complete remission of sarcoma with only anti-retroviral therapy suggesting that anti-retroviral therapy and non-KS specific chemotherapy can successfully control KS.

HIV-1 viral load: comparative evaluation of three commercially available assays in Argentina

Viral load (HIV-RNA copies per milliliter of plasma) has good correlation to prognosis considering progression to AIDS. The evaluation of commercial kits to measure viral load has become a need to find the most specific, sensitive and reproducible procedure to follow up HIV-infected patients. Hereby, a comparative analysis was done by using three different assays available in Argentina for quantitation of HIV-RNA in plasma. A plasma panel: 20 from HIV-1 infected individuals (9 asymptomatic and 11 symptomatic) and 9 from HIV-1 seronegative individuals was studied. Samples were run by Amplicor HIV-1 Monitor (Roche Diagnostic System, USA) Quantiplex HIV-1 RNA 2.0 Assay (Chiron Corporation, USA) and NASBA HIV-1 RNA QT (Organon Teknika, Holland). RNA was extracted from 0.2 ml of plasma for Amplicor, 0.1 ml and 1 ml of plasma for NASBA and, duplicates of 1 ml of plasma was centrifuged and pellet was used for bDNA assay no RNA extraction step. For a given specimen, a log difference of < 0.5 between assays was considered as concordant result. All seronegative samples were bellow the detection limit for all assays (Amplicor 200 c/ml, NASBA 400 c/ml and Quantiplex (bDNA) 500 c/ml). Two samples from asymptomatic patients were not detectable by NASBA (Sensitivity: 90%) Sensitivity was increased to 100% by using 1 ml of plasma. All samples were detectable by the other assays (sensitivity: 100%). For NASBA-bDNA, 74% samples were concordant, 35% for Amplicor-bDNA and 53% for NASBA-Amplicor. By using 1 ml of plasma from asymptomatic patients, concordance was 65% for NASBA-bDNA and 60% for NASBA Amplicor. Comparing samples from asymptomatic patients, only 22% was concordant in both cases. Reproducibility of NASBA was low (33% with differences lower than 0.5 Log) when 0.1 and 1 ml were used. Due to the levels of concordance of these results, it would be suggested to use always the same technique to follow up HIV-1 infection. The reproducibility of the assays should be tested by every laboratory and for every technician in charge of the assay in order to have confidence in the results specially to follow up HIV-infected patients or to monitor anti-viral therapies.

T-cell receptor BJ gene segment expression in human umbilical cord blood CD4+ and CD8+ T-cell subsets

By employing RT-PCR-based technology, followed by Southern-blot analysis, patterns of relative TRC BJ gene segment usage in human CD4+ and CD8+ umbilical cord blood T cells (UCT) from ten children were determined in relation to seven recombined TCR BV gene (sub) families (BV 3, 5S1, 6S1-3, 8, 9, 12 and 18). Normal frequency of usage of individual BJ members was observed to be extremely nonrandom. BJ usage in association with each BV was ranked and mean ranking values were calculated for individual BJs. Moreover, BJ family usage and family ranges as well as individual BJ over-representations were determined. In all these aspects of BJ exon expression, CD4+ and CD8+ UCT displayed similar distribution patterns. Comparisons of BJ usage in UCT subpopulations and in the adult peripheral blood lymphocyte (PBL) counterparts were performed and many similarities were observed. However, discrepancies in two parameters were recorded; contrary to observations in PBL, individual BJ over-representations were virtually absent in UCT, and significantly less wide BJ family ranges were demonstrated in CD8+ UCT relative to CD8+ PBL T cells. These differences support the notion that UCT are in a less dynamic state than are PBL T cells. Hence, despite the fact that PBL T cells are subjected to continuous antigenic challenge, the striking resemblance of PBL and UCT with regard to the overall individual relative usage, ranking, mean ranking and family utilisation of BJ gene segments, irrespective of the choice of recombined BV exons, may suggest a relatively nondiscriminatory role for the BJ gene product in antigen recognition as compared to those encoded by the BV, (N) and BD gene segments.

The role of virologic and immunologic factors in mother-to-child transmission of HIV-1

PROBLEM

More than 90% of human immunodeficiency virus type 1 (HIV-1) infection in children is acquired by mother-to-child transmission. However, infection of the child occurs in between 14 and 35% of cases.

METHOD OF STUDY

To understand the mechanisms involved in HIV-1 transmission, we have investigated the antigenic, molecular, and phenotypic characteristics of the virus harbored in infected mothers and their children.

RESULTS

A clear correlation was observed between the transmission of the virus and the isolation of viral variants with a rapidly replicating and syncytium-inducing phenotype from the mother. Furthermore, non-transmitting mothers were able to neutralize several primary isolates more frequently than transmitting mothers. The comparison of the viral phenotype and genotype of mother-child pairs showed that the transmitted virus did not have common features, suggesting that transmission is usually not a selective process.

CONCLUSIONS

This study suggests that transmission is governed by an interaction of both viral and immunological factors. The results obtained indicate that different strategies can be applied for the prevention of transmission.

Induction of apoptosis by primary HIV-1 isolates correlates with productive infection in peripheral blood mononuclear cells

OBJECTIVE

To study the apoptosis-inducing capacity of HIV-1 primary isolates in human peripheral blood mononuclear cells (PBMC) in relation to the viral biological phenotype.

DESIGN AND METHODS

Four HIV-1 primary isolates capable of replicating and inducing syncytia in the MT-2 cell line and two primary isolates lacking these properties were used to infect PBMC with the same infectious doses. The kinetics of virus production in the culture supernatants were followed in relation to apoptosis induction in PBMC as determined by intracellular labelling of apoptotic DNA strand breaks and flow cytometry analysis.

RESULTS

When low virus dose was used (0.001 m.o.i.), productive virus infection, with peak reverse transcriptase (RT) activity at days 5-7, was followed by high numbers of apoptotic cells at day 10 post infection. Tenfold higher inoculum dose (0.01 m.o.i.) resulted in enhanced virus production with peak RT activity at day 3 followed by high numbers of apoptotic cells at day 5 after infection. The apoptosis-inducing capacity of virus isolates was independent of their capacity to induce syncytia or replicate in the MT-2 cell line. However, upon cocultivation of infected PBMC with MT-2 cells, only virus with the MT-2 tropic phenotype initiated productive infection and induced apoptosis in MT-2 cells.

CONCLUSIONS

These results show that apoptosis induction in PBMC by primary HIV-1 isolates is closely related to the kinetics of virus replication but is not influenced by other biological properties of the virus such as syncytium-inducing capacity and MT-2 tropism.

Peripheral blood T cell expansions in patients with Behcet's disease

Behçet's disease (BD) is a chronic multisystemic inflammatory disorder characterized mainly by recurrent oral and genital aphthous ulcerations and uveitis. Etiology and pathogenesis of BD remain unknown. T cell receptor (TCR) V alpha/V beta gene product expression as well as Jbeta gene segment expression in peripheral blood of BD patients were analysed to investigate the possible role of T lymphocytes in the etiopathogenesis of BD. Flow cytometry with 12 TCR V-specific MoAbs was used for TCRV analyses. Jbeta gene segment usage by T cell populations expressing certain V betas was determined by polymerase chain reaction (PCR) technique with V beta- and C beta-specific primers, Southern blotting of PCR products, and subsequent hybridization with radiolabelled Jbeta gene segment-specific probes. Although 13 of the 23 BD patients exhibited increases in expression of one or more TCR V-gene products, only expansions among the CD4+ T cell subset were significantly more frequent in BD patients (7/23) compared with healthy controls (0/15) (P = 0.019). Six out of eight cases followed for up to 20 months had at least one expansion correlated with disease activity. A strict preference for particular Jbeta gene segments implicating clonality was apparent in all analysed T cell expansions and correlated well with disease activity. These results suggest a possible involvement of antigen-specific T lymphocytes in the pathogenesis of BD.

Detection of CD8 T-cell expansions with restricted T-cell receptor V gene usage in infants vertically infected by HIV-1

OBJECTIVE

To investigate the T-cell receptor (TCR) repertoire usage in infants born to mothers infected with HIV-1 in order to discern possible perturbations in TCR usage as a consequence of HIV-1 infection.

DESIGN

Blood samples from five HIV-1-infected and six non-infected children born to HIV-1-seropositive mothers were collected at two to three timepoints during the first and second year of life and the TCR variable gene usage was determined.

METHODS

Triple staining flow cytometry analysis using a panel of monoclonal antibodies (MAb) to TCR V alpha and V beta gene products and antibodies to CD4 and CD8 was performed.

RESULTS

Frequent large expansions of CD8+ lymphocyte subpopulations bearing distinct V alpha and V beta gene products was seen in HIV-1-infected children (four out of five) but was rarely detected in uninfected children.

CONCLUSION

The study demonstrated the frequent occurrence of persistent and clonal expansions of CD8+ T cells bearing distinct V alpha/V beta gene products in some HIV-1 vertically infected infants similar to those observed during primary infection in adults.

Overexpression of select T cell receptor V beta gene families within CD4+ and CD8+ T cell subsets of myasthenia gravis patients: a role for superantigen(s)?

BACKGROUND

The principal symptoms of myasthenia gravis (MG), muscle weakness and fatigue due to impaired neuromuscular transmission, are caused by autoantibodies to the muscle nicotinic acetylcholine receptor (AChR). The mechanisms underlying the autoimmune response, however, appear to be initiated by activation of specific HLA class II-restricted CD4+ T lymphocytes. Thus, central to elucidating the causation of MG is determining how T cells are recruited to contribute to misguided immunological assaults on the major autoantigenic target, AChR.

MATERIALS AND METHODS

By combining a polymerase chain reaction (PCR)-based strategy and Southern blot technique, we have analyzed the frequency of expression of 22 individual T cell receptor (TCR) V beta gene subfamilies in CD4+ and CD8+ peripheral blood T cell subsets derived from eight MG patients and seven healthy controls. The quantification of relative usage of individual TCR J beta gene segments was performed by hybridization of PCR-amplified products (specifically V beta 1-C beta) with a complete panel of 32P-5'-end-labeled J beta-specific oligonucleotide probes, followed by scanning analysis of autoradiographs.

RESULTS

Comparisons of data obtained from V beta analyses of T cells from MG patients with those from healthy individuals established that MG patients significantly overexpressed V beta 1, V beta 13.2, V beta 17, and V beta 20 gene family members within both CD4+ and CD8+ T cell subpopulations. Moreover, analysis of the relative utilization of individual TCR J beta gene segments in V beta 1+/CD4+ and V beta 1+/CD8+ T lymphocytes revealed distribution patterns in patients indistinguishable from those recorded in the corresponding cell subsets derived from controls.

CONCLUSIONS

T lymphocytes from MG patients displayed a biased overexpression of four TCR V beta gene segments: V beta 1, V beta 13.2, V beta 17, and V beta 20. The relative frequencies of association of individual V beta 1 (D beta) J beta combinations revealed that J beta gene usage in the V beta 1-over-represented T cell subsets had normal distribution patterns. It can thus be deduced that J beta gene segment products appear not to have a selective effect on the process leading to overexpression of V beta 1 exons in MG patients. Hence, our observations suggest a possible role for superantigen(s) in the T cell activation in MG patients.

Enhanced prevalence of T cell receptor V beta 7 gene family expression in human intestine-associated T lymphocytes

Relative levels of expression of T cell receptor variable (V) beta and joining (J) beta gene segments were determined in T cells derived from intestinal biopsies of healthy mucosal areas, mesenteric lymph nodes and peripheral blood of the same individuals. Samples taken from patients suffering from inflammatory (n = 8) and non-inflammatory (n = 8) bowel diseases were analyzed by semi-quantitative polymerase chain reaction-based methods. In the intestine, fewer (median = 3.5) V beta gene segments constituted more than 50% of the T cell receptor V beta repertoire compared to that of peripheral blood T cells (median = 7, P < 0.001). Interestingly, in all sixteen individuals studied, intestinal T lymphocytes (IL-T) expressed the V beta 7 gene family to a higher degree than did T cells in the paired peripheral blood and mesenteric lymph nodes (P < 0.001). T cell receptor J beta gene segment analyses of V beta 7+ T cells revealed no significant difference in oligoclonality rates between peripheral blood (4/16) and intestine (7/16) (P = 0.46). Hence, overexpression of intestinal TCR V beta 7 message does not seem to be due to oligoclonal expansions in the majority of the samples.

Interplay of HIV-1 phenotype and neutralizing antibody response in pathogenesis of AIDS

A majority of human immunodeficiency virus type 1 (HIV-1) infected individuals display a rapid loss of CD4+ lymphocytes with fast progression towards overt acquired immunodeficiency syndrome (AIDS). However, a small proportion of individuals infected by HIV-1 remain immunologically intact for many years. In order to identify factors that might influence the pathogenesis of HIV-1 infection, 21 Italian mothers and 11 Swedish homosexual men were studied for the presence of autologous neutralizing antibodies in serum, biological phenotype of virus isolates and envelope variable region 3 (V3) sequences. The results were compared to the risk of mother-to-child transmission and progression of the disease. The presence of a neutralizing antibody response to the autologous virus as well as a virus with slow replicative capacity were linked both to low risk of mother-to-child transmission and non-progression of the disease. Patients whose peripheral blood mononuclear cells contained a mutation in the tip of the V3 loop (Arg318 to serine, lysine or leucine) significantly more often had neutralizing antibodies to autologous virus isolates containing arginine at this position. Thus, it appears that the interplay and balance between neutralizing antibody response of the host and the biological phenotype of HIV-1 strongly influence pathogenesis.

T-cell receptor J beta gene segment usage in immature and mature human thymocytes

Immature double positive (DP, CD4+CD8+) and mature single positive (SP, CD4+CD8- and CD4-CD8+) human thymocytes from nine thymi were analysed for their complete patterns of relative TCR J beta multigene member usage in relation to six rearranged V beta family exons (V beta 5.1, 6.1-3, 8, 9, 12 and 18). Each sample tested contained mRNA transcripts corresponding to all potential V beta(D beta)J beta combinations. Individual J beta gene segments were expressed in a similar, highly non-random manner both in SP and DP thymocytes, irrespective of original genomic position of the individual associated V beta exon. In addition, ranges of family usage and frequency of individual over-representations of J beta gene segments, as determined in DP and SP thymocyte populations, displayed no significant differences. Upon comparison of DP and SP thymocytes, however, a discrepancy in one aspect of J beta gene utilization was established: decreasing J beta family 1/J beta family 2 ratios were determined to be positively correlated with increasing maturity of thymocytes, a condition further supported by data previously obtained from studies of PBL T cells. At the individual J beta gene level, the observed gradual modification of the relative family usage can largely be explained by a significant shift from a higher J beta 1.1/J beta 2.7 ratio in DP to a higher J beta 2.7/J beta 1.1 ratio in SP thymocytes. Altogether, the present results imply that selectional processes in the thymus appear to have only minor consequences on the distribution pattern of expressed J beta exons. Hence, the disproportionate pattern of TCR J beta gene usage seems to be established mainly at the recombinatorial level followed by minor adjustments during thymic and post-thymic events.

Detection of CD4+ T cells harboring human immunodeficiency virus type 1 DNA by flow cytometry using simultaneous immunophenotyping and PCR-driven in situ hybridization: evidence of epitope masking of the CD4 cell surface molecule in vivo

Human immunodeficiency virus type 1 (HIV-1) infection of T cells and cells of the monocyte/macrophage lineage requires a specific interaction between the CD4 antigen expressed on the cell surface and the HIV-1 external envelope glycoprotein (gp120). To study the association between HIV-1 infection and modulation of cell surface expression of the CD4 molecule in vivo, we examined the CD4+ T cells harboring proviral DNA obtained from HIV-1-infected individuals who had received no antiretroviral therapy for at least 90 days. Simultaneous immunophenotyping of CD4 cell surface expression and PCR-driven in situ hybridization for HIV-1 DNA were used to resolve the CD4+ T cells into distinct populations predicted upon the presence or absence of proviral DNA. Among the HIV-1-infected study subjects, the percentage of CD4+ T cells harboring proviral DNA ranged from 17.3 to 55.5%, with a mean of 40.5%. Cell surface fluorescent staining with anti-CD4 antibody directed against a non-gp120 binding site-related epitope (L120) or a conformation-dependent epitope of the gp120 binding site (Leu 3A) demonstrated either an equivalent or a 1.5- to 3-fold-lower cell surface staining intensity for the HIV-1 DNA-positive subpopulation relative to the HIV-1 DNA-negative subpopulation, respectively. These data suggest that masking or alteration of specific epitopes on the CD4 molecule occurs after viral infection.

Nonrandom T-cell receptor J beta usage pattern in human CD4+ and CD8+ peripheral T cells

Association frequencies of TCR J beta gene segments with six V beta families (V beta 3, 6.1-3, 8, 9, 12, and 18) were analyzed in T-cell populations obtained from healthy blood donors. The six selected V beta families are located at various chromosomal positions relative to other recombinatorial elements (D beta, J beta, C beta). We report here that in CD4+ as well as CD8+ T-cell subsets, all 13 J beta gene segments were used in combination with all the V beta s tested and that no correlation between the genomic position of the individual V beta s and J beta gene segment usage was observed. J beta gene segment usage was found to be nonrandom in general, with J beta 2.7 and J beta 2.4 exhibiting highest and lowest frequency of utilization, respectively. J beta family 2 was used more frequently than J beta family 1 by the two T-cell subsets. Some individual J beta gene segments were skewed toward either CD4+ or CD8+ T cells. Thus, J beta 1.3 and J beta 1.6 were consistently biased toward expression in CD4+ T cells. In contrast, when combined with V beta 8 or V beta 9, J beta 2.1 results were skewed dramatically toward expression in CD8+ T cells. We also found 70 cases of expanded individual V beta/J beta associations in a total of 1092 investigated combinations, 62 of which were confined to the CD8+ T-cell populations. CD8+ T-cell populations are thus much more likely to contain TCR V beta/J beta-restricted expansions than CD4+ T cells.

Transmission of human immunodeficiency virus type 1 (HIV-1) from mother to child correlates with viral phenotype

The aim of this study was to investigate if the risk of mother-to-child transmission of human immunodeficiency virus type 1 (HIV-1) is influenced by the biological phenotype of the mother's virus. Virus isolates from 30 HIV-1 infected mothers and 12 infected children born to these mothers were analyzed for replication on several cell lines (Jurkat-tat, Jurkat, CEM, U937 clone 2, and MT-2). We show that mothers who harbor virus able to replicate in cell lines (rapid/high virus) have a significantly higher risk to infect their children than mothers with slow/low virus (P = 0.017). Children born to mothers with rapid/high viruses can be infected by slow/low as well as rapid/high viruses, while mothers with slow/low virus appear to transmit slow/low virus in every case. Our study shows that the biological phenotype of the mother's virus may serve as a complementary marker to CD4+ lymphocyte counts and p24 antigenemia in predicting the risk of transmission of HIV-1 to the child.

Neutralizing antibodies and viral characteristics in mother-to-child transmission of HIV-1

OBJECTIVE

To determine viral characteristics and the protective effect of virus neutralizing antibodies in mother-to-child transmission of HIV-1.

MOLECULAR STUDIES

Ten HIV-1-infected mother-child pairs were sampled within 4 months of delivery. Variable region 3 of the viral envelope was amplified by nested polymerase chain reaction and sequenced, directly and/or after cloning, by solid-phase DNA sequencing. The amino acid sequence of variable region 3 from all 10 children was homogeneous, whereas the mothers showed varying degrees of heterogeneity. Apparently, selection of an HIV-1 variant occurs either at transmission or during initial virus replication in the infected child. No characteristic molecular features of the transmitted virus were identified.

BIOLOGICAL STUDIES

Virus isolates from 13 mother-child pairs were characterized for replicative capacity in a variety of cell lines. Eight mothers from whom a virus with a slow/low replicative pattern was isolated transmitted the slow/low virus to their children, whereas mothers with a rapid/high virus transmitted either a rapid/high or a slow/low virus (two cases each). This indicates that viruses with rapid/high replicative capacity do not have a selective advantage during transmission.

VIRUS NEUTRALIZING

Sera from 20 mothers were characterized for the ability to neutralize their own virus (autologous neutralization) and virus from other mothers (heterologous neutralization). The results showed that non-transmitting mothers had neutralizing antibodies against autologous virus more frequently than transmitting mothers. In addition, all mothers with autologous neutralizing antibodies also neutralized at least two heterologous primary isolates. This indicates that a broad neutralizing antibody response may be linked to a lower risk of mother-to-child transmission.

CONCLUSION

On the basis of the variable region 3 loop sequence, HIV-1-infected infants harbour homogenous virus populations. Despite this, no molecular or biological markers for selective transmission could be identified. A maternal neutralizing antibody response with broad specificity may protect the child from HIV-1 infection.

Mother-to-child transmission of human immunodeficiency virus type 1: correlation with neutralizing antibodies against primary isolates

The aim of this study was to investigate the influence of neutralizing antibodies in mother's serum on the risk of mother-to-child transmission of human immunodeficiency virus type 1 (HIV-1). Sera from 20 HIV-1 infected mothers were analyzed for their ability to neutralize their own virus (autologous neutralization) and virus obtained from other mothers (heterologous neutralization). A statistically significant correlation was found between the capacity to neutralize 1 selected primary isolate and protection of the child from infection. Also, neutralizing antibodies against autologous virus were more frequently present in nontransmitting mothers than in transmitting mothers (5 and 2, respectively, of 10 mothers). The mothers with autologous neutralizing antibodies also neutralized at least 2 heterologous primary isolates. Thus, mothers with neutralizing antibodies to primary HIV-1 isolates have a reduced risk of infecting their children.