Graham P. Taylor

Treatment of tuberculosis in HIV-infected persons in the era of highly active antiretroviral therapy

Objective To assess the risks and benefits of administering highly active antiretroviral therapy (HAART) during the treatment of tuberculosis (TB) in HIV-infected patients. Design and methods HIV-1 patients presenting to 12 HIV centres in Greater London and south-east England with culture-proven TB were identified from January 1996 to June 1999. Case-notes were reviewed retrospectively. Results Patients (n = 188) were severely immunocompromised with a median CD4 cell count at TB diagnosis of 90 × 106 cells/l (IQR: 30–180). At presentation, 85% (n = 159) were not taking antiretrovirals. A total of 45% commenced HAART during TB treatment, which was associated with significant reductions in viral load, AIDS-defining illness (ADI) [3.5 versus 24.5%; relative risk (RR) = 0.14] and mortality. Only nine of 91 (10%) patients with a CD4 count > 100 × 106 cells/l at TB diagnosis experienced a further ADI, whereas 18 of 92 (20%) patients with a CD4 count < 100 × 106 cells/l developed this complication. Adverse events (AE) occurred in 99 (54%) of 183 patients, one-third of whom changed or interrupted HIV and/or TB medication. The majority of AE occurred within the first 2 months, with peripheral neuropathy (21%), rash (17%) and gastrointestinal upset (10%) occurring most commonly. Conclusions Many physicians delay HAART in patients presenting with TB because of pill burden, drug/drug interactions and toxicity. Although the use of HAART led to significant reductions in viral load, ADI and mortality, co-infected patients commonly experienced AE leading to interruptions in TB/HIV therapy. We therefore recommend starting HAART early for patients with advanced HIV disease (CD4 < 100 × 106 cells/l) and deferring HAART until the continuation phase of TB therapy (i.e. after 2 months) for patients who are clinically stable (CD4 > 100 × 106 cells/l).

Fratricide among CD8+ T Lymphocytes Naturally Infected with Human T Cell Lymphotropic Virus Type I

Infection and gene expression by the human T lymphotropic virus type I (HTLV-I) in vivo have been thought to be confined to CD4(+) T lymphocytes. We show here that, in natural HTLV-I infection, a significant proportion of CD8(+) T lymphocytes are infected by HTLV-I. Interestingly, HTLV-I-specific but not Epstein-Barr virus-specific CD8(+) T lymphocytes were shown to be infected. Furthermore, HTLV-I protein expression in naturally infected CD8(+) T lymphocytes renders them susceptible to fratricide mediated by autologous HTLV-I-specific CD8(+) T lymphocytes. Fratricide among virus-specific CTLs could impair the immune control of HTLV-I and possibly other lymphotropic viruses.

Natural history of adult T-cell leukemia/lymphoma and approaches to therapy

After cell-to-cell transmission, HTLV-I increases its viral genome by de novo infection and proliferation of infected cells. Proliferation of infected cells is clonal and persistent in vivo. During the carrier state, infected cells are selected in vivo by the hosts immune system, the genetic and epigenetic environment of proviral integration sites, and other factors. In leukemic cells, tax gene expression is frequently impaired by genetic and epigenetic mechanisms. Such loss of Tax expression enables ATL cells to escape the host immune system. On the other hand, ATL cells acquire the ability to proliferate without Tax by intracellular genetic and epigenetic changes. Despite advances in support and the development of novel treatment agents, the prognosis for ATLL remains poor. A number of therapies, however, do appear to improve prognosis compared to CHOP (VEPA). These include interferon-α plus zidovudine (probably after 1–2 cycles of CHOP), intensive chemotherapy as in LSG-15 with G-CSF support and Allo-SCT (which includes the potential for cure). Emerging novel approaches include HDAC inhibitors, monoclonal antibodies, and proteasome inhibitors. Comparison between different therapeutic approaches is complicated by the range of natural history of ATLL, different recruitments of naïve-to-therapy, refractory or relapsed patients, and variations in the reporting of outcome that frequently excludes difficult-to-evaluate patients. Moreover, results from relatively small proof-of-principle studies have not been extended with randomized, controlled trials. As a result, currently, there is no clear evidence to support the value of any particular treatment approach over others. To avoid further unnecessary patient suffering and to identify optimal therapy as rapidly as possible, large randomized, controlled trials encompassing multicenter, international collaborations will be necessary.

The host genomic environment of the provirus determines the abundance of HTLV-1-infected T-cell clones

Human T-lymphotropic virus type 1 (HTLV-1) persists by driving clonal proliferation of infected T lymphocytes. A high proviral load predisposes to HTLV-1-associated diseases. Yet the reasons for the variation within and between persons in the abundance of HTLV-1-infected clones remain unknown. We devised a high-throughput protocol to map the genomic location and quantify the abundance of > 91,000 unique insertion sites of the provirus from 61 HTLV-1(+) persons and > 2100 sites from in vitro infection. We show that a typical HTLV-1-infected host carries between 500 and 5000 unique insertion sites. We demonstrate that negative selection dominates during chronic infection, favoring establishment of proviruses integrated in transcriptionally silenced DNA: this selection is significantly stronger in asymptomatic carriers. We define a parameter, the oligoclonality index, to quantify clonality. The high proviral load characteristic of HTLV-1-associated inflammatory disease results from a larger number of unique insertion sites than in asymptomatic carriers and not, as previously thought, from a difference in clonality. The abundance of established HTLV-1 clones is determined by genomic features of the host DNA flanking the provirus. HTLV-1 clonal expansion in vivo is favored by orientation of the provirus in the same sense as the nearest host gene.

Earlier initiation of ART and further decline in mother-to-child HIV transmission rates, 2000-2011

Objectives:To analyze mother-to-child HIV transmission (MTCT) rates over time in light of changes in management, demographic, and pregnancy characteristics. Design:Population-based surveillance data on diagnosed HIV-positive women and their infants are routinely collected in the UK and Ireland. Methods:A total of 12 486 singleton pregnancies delivered in 2000–2011 were analyzed. HIV infection status was available for 11 515 infants (92.2%). Results:The rate of MTCT declined from 2.1% (17/816) in 2000–2001 to 0.46% (nine of 1975, 95% confidence interval: 0.21–0.86%) in 2010–2011 (trend, P = 0.01), because of a combination of factors including earlier initiation of antenatal combination antiretroviral therapy (cART). Excluding 63 infants who were breastfed or acquired HIV postnatally, MTCT risk was significantly higher for all modes of delivery in women with viral load of 50–399 copies/ml (1.0%, 14/1349), compared with viral load of less than 50 copies/ml (0.09%, six of 6347, P <0.001). Among the former (viral load 50–399 copies/ml), the risk of MTCT was 0.26% (two of 777) following elective cesarean section and 1.1% (two of 188) following planned vaginal delivery (P = 0.17), excluding in-utero transmissions. MTCT probability declined rapidly with each additional week of treatment initially, followed by a slower decline up to about 15 weeks of cART, with substantial differences by baseline viral load. Conclusion:MTCT rates in the UK and Ireland have continued to decline since 2006, reaching an all-time low of 5 per 1000 in 2010–2011. This was primarily because of a reduction in transmissions associated with late initiation or nonreceipt of antenatal cART, and an increase in the proportion of women on cART at conception.

In vivo kinetics of human natural killer cells: the effects of ageing and acute and chronic viral infection

Human natural killer (NK) cells form a circulating population in a state of dynamic homeostasis. We investigated NK cell homeostasis by labelling dividing cells in vivo using deuterium‐enriched glucose in young and elderly healthy subjects and patients with viral infection. Following a 24‐hr intravenous infusion of 6,6‐D2‐glucose, CD3– CD16+ NK cells sorted from peripheral blood mononuclear cells (PBMC) by fluorescence‐activated cell sorter (FACS) were analysed for DNA deuterium content by gas chromatography mass spectrometry to yield minimum estimates for proliferation rate (p). In healthy young adults (n = 5), deuterium enrichment was maximal ∼ 10 days after labelling, consistent with postmitotic maturation preceding circulation. The mean (± standard deviation) proliferation rate was 4·3 ± 2·4%/day (equivalent to a doubling time of 16 days) and the total production rate was 15 ± 7·6 × 106 cells/l/day. Labelled cells disappeared from the circulation at a similar rate [6·9 ± 4·0%/day; half‐life (T½) < 10 days]. Healthy elderly subjects (n = 8) had lower proliferation and production rates (P = 2·5 ± 1·0%/day and 7·3 ± 3·7 × 106 cells/l/day, respectively; P = 0·04). Similar rates were seen in patients chronically infected with human T‐cell lymphotropic virus type I (HTLV‐I) (P = 3·2 ± 1·9%/day). In acute infectious mononucleosis (n = 5), NK cell numbers were increased but kinetics were unaffected (P = 2·8 ± 1·0%/day) a mean of 12 days after symptom onset. Human NK cells have a turnover time in blood of about 2 weeks. Proliferation rates appear to fall with ageing, remain unperturbed by chronic HTLV‐I infection and normalize rapidly following acute Epstein–Barr virus infection.

Arginase activity mediates reversible T cell hyporesponsiveness in human pregnancy

Complex regulation of T cell functions during pregnancy is required to ensure materno‐fetal tolerance. Here we reveal a novel pathway for the temporary suppression of maternal T cell responses in uncomplicated human pregnancies. Our results show that arginase activity is significantly increased in the peripheral blood of pregnant women and remarkably high arginase activities are expressed in term placentae. High enzymatic activity results in high turnover of its substrate L‐arginine and concomitant reduction of this amino acid in the microenvironment. Amino acid deprivation is emerging as a regulatory pathway of lymphocyte responses and we assessed the consequences of this enhanced arginase activity on T cell responses. Arginase‐mediated L‐arginine depletion induces down‐regulation of CD3ζ, the main signalling chain of the TCR, and functional T cell hyporesponsiveness. Importantly, this arginase‐mediated T cell suppression was reversible, as inhibition of arginase activity or addition of exogenous L‐arginine restored CD3ζ chain expression and T cell proliferation. Thus, L‐arginine metabolism constitutes a novel physiological mechanism contributing to the temporary suppression of the maternal immune response during human pregnancy.

Human T-lymphotropic virus, type 1, tax protein triggers microtubule reorientation in the virological synapse

We showed recently that the human T-lymphotropic virus, type 1 (HTLV-1), spreads directly from cell to cell via a virological synapse. The HTLV-1 virological synapse resembles the immunological synapse; each is a specialized contact between a lymphocyte and another cell that contains organized protein microdomains, and each involves repolarization of the T-cell microtubule cytoskeleton. However, formation of the virological synapse is not triggered by T-cell receptor-mediated antigen recognition. On the basis of our previous data, we postulated that formation of the viral synapse was triggered by a conjunction of two signals, one from HTLV-1 infection of the T-cell and one from cell-cell contact. We have recently identified ICAM-1 engagement as a cell-contact signal that causes the microtubule polarization associated with the virological synapse. Here we used confocal microscopy of T-lymphocytes naturally infected with HTLV-1 or transfected with individual HTLV-1 genes to investigate the role of the viral transcriptional transactivator protein Tax. Polarization of the microtubules was induced by cell-cell contact or by cross-linking T-cell surface molecules with monoclonal antibodies adsorbed to latex beads. We show that Tax, which is mainly found in the nucleus, is also present at two specific extranuclear sites as follows: around the microtubule organizing center in association with the cis-Golgi and in the cell-cell contact region. We show that expression of Tax provides an intracellular signal that synergizes with ICAM-1 engagement to cause the T-cell microtubule polarization observed at the virological synapse.

Pre-eclampsia, antiretroviral therapy, and immune reconstitution

Antiretrovirals are standard treatment for HIV-1-positive women during pregnancy in the UK, but little is known about maternal or fetal safety. In our cohort study of 214 pregnant women with HIV-1 infection, those who received no antiretroviral therapy had a rate of pre-eclampsia significantly lower (none of 61) than those on triple antiretroviral therapy (8 of 76; odds ratio 15.3, 95% CI 0.9-270, p=0.0087). However, the rate of pre-eclampsia in HIV-1-positive women on treatment did not differ from that in uninfected controls (12 of 214; p=0.2). The association of HIV-1-related immune deficiency with a low rate of pre-eclampsia, and the restoration of this rate in women treated with triple antiretroviral therapy to the expected rate indicates a pivotal role of the immune system in the pathogenesis of pre-eclampsia. The clinical presentation of pre-eclampsia and toxic effects of antiretroviral therapy could overlap and complicate diagnosis and management in these patients.

High-Density Lipoproteins Differentially Modulate Cytokine-Induced Expression of E-Selectin and Cyclooxygenase-2

Atherogenesis is a multifactorial chronic inflammatory disease in which low plasma levels of HDLs are a strong predictor of the condition. Although the mechanism of protection by HDLs is not precisely known, HDLs have been shown to influence many of the events involved in the development of atherosclerosis. Previously we have shown that HDLs inhibited the cytokine-induced expression of adhesion molecules (E-selectin, VCAM-1, and ICAM-1) by endothelial cells (ECs). As the complete transcriptional regulation of all 3 genes requires the NF-kappaB family of transcription factors, we examined the effect of HDLs on activation of NF-kappaB. We also investigated the effect of HDLs on 2 other cytokine-induced genes, granulocyte-macrophage colony-stimulating factor (GM-CSF) and cyclooxygenase (Cox-2; prostaglandin H2 synthase, EC 0.1.14.99.1). E-selectin expression in response to tumor necrosis factor-alpha (TNFalpha) was, as expected, inhibited in ECs that had been preincubated with HDLs. However, the level of secretion of GM-CSF in the same cultures was no different from control. In a similar manner, although HDLs had no effect on steady-state mRNA levels of GM-CSF, the levels of E-selectin were significantly inhibited by HDLs. In transient cotransfection experiments we found that HDLs inhibited the cytokine-induced expression of a reporter gene driven by the E-selectin proximal promoter (-383 to 80) but had no effect on the expression of a reporter gene driven under the control of the proximal promoter of GM-CSF (-627 to 28). As would be predicted from this differential response, HDLs did not influence the nuclear translocation or DNA binding of NF-kappaB, or alter the kinetics of degradation and resynthesis of the inhibitory protein IkappaBalpha. We found that HDLs synergized with cytokine to enhance the expression of Cox-2 and induce the synthesis of its main EC product, prostacyclin (PGI2), a potent inhibitor of platelet and leukocyte functions. In conclusion, HDL induces an antiinflammatory phenotype in cytokine-induced ECs, synergizing with cytokine to induce elevation of Cox-2 in addition to inhibiting adhesion molecule expression. Our studies show that these differential effects are mediated in a manner that is likely to be independent of NF-kappaB per se.