The effect of human T cell leukaemia virus type I infection on a herpes simplex virus-specific CD8+ cytotoxic T cell clone

Histone deacetylase inhibitors increase virus gene expression but decrease CD8+ cell antiviral function in HTLV-1 infection

The dynamics of human T-lymphotropic virus type-1 (HTLV-1) provirus expression in vivo are unknown. There is much evidence to suggest that HTLV-1 gene expression is restricted: this restricted gene expression may contribute to HTLV-1 persistence by limiting the ability of the HTLV-1–specific CD8+ cell immune response to clear infected cells. In this study, we tested the hypothesis that derepression of HTLV-1 gene expression would allow an increase in CD8+ cell–mediated lysis of HTLV-1–infected cells. Using histone deacetylase enzyme inhibitors (HDIs) to hyperacetylate histones and increase HTLV-1 gene expression, we found that HDIs doubled Tax expression in naturally infected lymphocytes after overnight culture. However, the rate of CD8+ cell–mediated lysis of Tax-expressing cells ex vivo was halved. HDIs appeared to inhibit the CD8+ cell–mediated lytic process itself, indicating a role for the microtubule-associated HDAC6 enzyme. These observations indicate that HDIs may reduce the efficiency of cytotoxic T-cell (CTL) surveillance of HTLV-1 in vivo. The impact of HDIs on HTLV-1 proviral load in vivo cannot be accurately predicted because of the widespread effects of these drugs on cellular processes; we therefore recommend caution in the use of HDIs in nonmalignant cases of HTLV-1 infection.

Recent progress in herpes simplex virus immunobiology and vaccine research

Herpes simplex virus types 1 and 2 (HSV-1 and HSV-2) cause prevalent, chronic infections that have serious outcomes in some individuals. Neonatal herpes may occur when the infant traverses the cervix during maternal genital herpes. Genital herpes is a major risk factor for human immunodeficiency virus type 1 transmission. Considerable efforts have been made to design and test vaccines for HSV, focusing on genital infection with HSV-2. Several protein subunit vaccines based on HSV-2 envelope glycoproteins have reached advanced-phase clinical trials. These antigens were chosen because they are the targets of neutralizing-antibody responses and because they elicit cellular immunity. Encouraging results have been reported in studies of treatment of HSV-seronegative women with a vaccine consisting of truncated glycoprotein D of HSV-2 and a novel adjuvant. Because most sexual HSV transmission occurs during asymptomatic shedding, it is important to evaluate the impact of vaccination on HSV-2 infection, clinically apparent genital herpes, and HSV shedding among vaccine recipients who acquire infection. There are several other attractive formats, including subunit vaccines that target cellular immune responses, live attenuated virus strains, and mutant strains that undergo incomplete lytic replication. HSV vaccines have also been evaluated for the immunotherapy of established HSV infection.

HLA-A*26, HLA-B*4002, HLA-B*4006, and HLA-B*4801 alleles predispose to adult T cell leukemia: the limited recognition of HTLV type 1 tax peptide anchor motifs and epitopes to generate anti-HTLV type 1 tax CD8(+) cytotoxic T lymphocytes

Genetic risk for adult T cell leukemia (ATL) has been implicated by ethnic and familial segregation of ATL patients from HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). To clarify the genetic risk for ATL, we characterized HLA class I alleles of ATL patients and analyzed the anchor motifs of HTLV-1 peptides binding to HLA class I molecules, using 291 lines of anti-HTLV-1 CD8(+) cytotoxic T lymphocytes (CTLs) generated in vitro with a total of 165 synthetic peptides for HTLV-1 Tax and Env proteins. Allele frequencies of HLA-A*26, B*4002, B*4006, and B*4801 were significantly higher in ATL patients than in HAM/TSP patients and asymptomatic HTLV-1 carriers in southern Japan. CD8(+) CTL analysis revealed the HTLV-1 Tax peptide sequence to completely lack anchor motifs of peptides binding to HLA-A*26,B*4002, and B*4006 molecules but to possess one anchor for HLA-B*4801, while the HTLV-1 Env peptide sequence had many anchor motifs for HLA-A*26, B*4002, B*4006, and B*4801 molecules. Most ATL patients featured heterozygous HLA class I alleles composed of HLA-A*26, B*4002, B*4006, and B*4801, with a lower number of HTLV-1 Tax peptide anchor motifs and epitopes generating anti-HTLV-1 Tax CD8(+) CTLs than individuals possessing other HLA alleles. The relationship between Tax epitope and ATL incidence was verified by the significantly decreased number of HTLV-1 Tax epitopes in ATL patients compared with asymptomatic HTLV-1 carriers (p < 0.01) as well as late onset ATL patients (p < 0.001). These results indicate that HLA-A*26, B*4002, B*4006, and B*4801 alleles predispose to ATL because of the limited recognition of HTLV-1 Tax peptide anchor motifs and epitopes capable of generating anti-HTLV-1 Tax CD8(+) CTLs.

Tegument-specific, virus-reactive CD4 T cells localize to the cornea in herpes simplex virus interstitial keratitis in humans

Herpes stromal keratitis (HSK) is a prevalent and frequently vision-threatening disease associated with herpes simplex virus type 1 (HSV-1) infection. In mice, HSK progression occurs after viral clearance and requires T cells and neutrophils. One model implicates Th1-like CD4 T cells with cross-reactivity between the HSV-1 protein UL6 and a corneal autoantigen. HSK can be prevented by establishing specific immunological tolerance. However, HSK can also occur in T-cell receptor-transgenic X SCID mice lacking HSV-specific T cells. To study the pathogenesis of HSK in the natural host species, we measured local HSV-specific T-cell responses in HSK corneas removed at transplant surgery (n = 5) or control corneas (n = 2). HSV-1 DNA was detected by PCR in two specimens. HSV-specific CD4 T cells were enriched in three of the five HSK specimens and were not detectable in the control specimens. Reactivity with peptide epitopes within the tegument proteins UL21 and UL49 was documented. Responses to HSV-1 UL6 were not detected. Diverse HLA DR and DP alleles restricted these local responses. Most clones secreted gamma interferon, but not interleukin-5, in response to antigen. HSV-specific CD8 cells were also recovered. Some clones had cytotoxic-T-lymphocyte activity. The diverse specificities and HLA-restricting alleles of local virus-specific T cells in HSK are consistent with their contribution to HSK by a proinflammatory effect.

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.

Immortalization of human T cells expressing T-cell receptor gamma delta by herpesvirus saimiri

Herpesvirus saimiri (HVS) has recently been shown to immortalize human CD4+ and CD8+ T cells expressing T-cell receptor alpha beta (TCR-alpha beta) with the maintenance of their original phenotypes and functional properties. However, the immortalization of human T cells expressing TCR-gamma delta by HVS has not been successful. Here we report that HVS can also infect and immortalize human T cells expressing TCR-gamma delta. Two human TCR-gamma delta+ T-cell clones, which continuously proliferated in interleukin-2-containing culture medium without any exogenous stimulation or addition of feeder cells for more than 8 months, were established by HVS infection. Morphologically, the HVS-transformed TCR-gamma delta+ T-cell clones were granular lymphocytes which exhibited wide-range HLA-unrestricted cytotoxicity as untransformed TCR-gamma delta+ T cells. Their phenotypes and cytotoxic activities were not altered during long-term culture. The immortalization of human TCR-gamma delta+ T cells by HVS infection would be useful for functional analysis of this lymphocyte population, which is believed to play an important role in protection against various infectious diseases.

Phenotypic progression of a rat lymphoid cell line immortalized by human T-lymphotropic virus type I to induce lymphoma/leukemia-like disease in rats

Rat lymphoid cells, TARS-1, immortalized by coculture with adult T-cell leukemia cells, were intraperitoneally injected into 65 newborn, inbred WKAH/Hkm rats. In most of the rats, tumor nodules were discernible 7 to 15 days after transplantation but were completely rejected within 5 to 6 weeks. Two rats with no tumor nodules exhibited gait disturbances and paralysis of the hind legs 3 to 4 weeks after transplantation. Histological and hematological examinations revealed that a lymphoma/leukemia-like disease had developed in one of the two rats, and the T-lymphoid cell line WLeuk-1 was established from peripheral blood mononuclear cells from this rat. When the WLeuk-1 cells were transplanted into newborn WKAH/Hkm rats, the animals died of a lymphoma/leukemia-like disease within several weeks after transplantation, in contrast to their rejection of the TARS-1 cells. Southern blot and karyotype analyses revealed that WLeuk-1 cells had retained the marker chromosomes and human T-lymphotropic virus type I (HTLV-I) integration patterns of the parent cell line, TARS-1. The additional specific chromosome abnormalities 3p+,t (12;13), and Xq+ were found in the WLeuk-1 cells. Moreover, the expression of HTLV-I structural proteins was slightly depressed in WLeuk-1 cells, while that of the transacting factors p40tax and p21x, but not that of p27rex, was enhanced about fivefold compared with that in TARS-1. The transactivating function of p40tax was intact in WLeuk-1, as evidenced by enhanced interleukin-2 receptor alpha chain expression. These results suggest that aberrant expression of HTLV-I regulatory genes and alteration of cellular genes were associated with the phenotypic progression of the WLeuk-1 cell line.