The ORF3 protein of porcine circovirus type 2 is involved in viral pathogenesis in vivo

Porcine circovirus type 2 (PCV2) is the primary causative agent of an emerging swine disease, postweaning multisystemic wasting syndrome. We previously showed that a novel identified protein, ORF3, was not essential for PCV2 replication in cultured PK15 cells and played a major role in virus-induced apoptosis. To evaluate the role of the ORF3 protein in viral pathogenesis in vivo, we inoculated 8-week-old BALB/c mice that have been developed for PCV2 replication with ORF3-deficient mutant PCV2 (mPCV2). By 42 days postinoculation, all of the mice inoculated with the mPCV2, as well as with wild-type PCV2 (wPCV2), had seroconverted to PCV2 capsid antibody, and the mutant induced levels of PCV2 antibodies that were higher than those of the wPCV2. The PCV2 genomic copy numbers in serum were significantly higher (P<0.05) in the wPCV2-inoculated mice than in mice inoculated with the mPCV2. Also, the wPCV2 caused microscopic lesions characterized by lymphocyte depletion with histiocytic infiltration of lymphoid organs, but the mutant virus failed to induce any obvious pathological lesions. In situ hybridization and immunohistochemical analyses also showed that larger amounts of viral DNA and antigens were detected in the lymph nodes of the wPCV2-inoculated than mPCV2-inoculated mice. Furthermore, animals of the wPCV2-inoculated group showed significant downshifts of CD8(+) T-cell subsets of peripheral blood lymphocytes compared to the control mice (P<0.05) at various time points postinoculation. Also, the proportions of the CD4(+) and CD4(+) CD8(+) cells were significantly reduced in wPCV2-inoculated mice at some time points postinoculation. In contrast, there are some reductions in the proportions of these subsets in the mutant virus-inoculated mice, but the proportions do not decrease significantly. Taken together, these results demonstrate that the ORF3 protein is also dispensable for viral replication in vivo and that it plays an important role in viral pathogenesis.

Expansion and diversification of virus-specific T cells following immunization of human immunodeficiency virus type 1 (HIV-1)-infected individuals with a recombinant modified vaccinia virus Ankara/HIV-1 Gag vaccine

Affordable therapeutic strategies that induce sustained control of human immunodeficiency virus type 1 (HIV-1) replication and are tailored to the developing world are urgently needed. Since CD8(+) and CD4(+) T cells are crucial to HIV-1 control, stimulation of potent cellular responses by therapeutic vaccination might be exploited to reduce antiretroviral drug exposure. However, therapeutic vaccines tested to date have shown modest immunogenicity. In this study, we performed a comprehensive analysis of the changes in virus-specific CD8(+) and CD4(+) T-cell responses occurring after vaccination of 16 HIV-1-infected individuals with a recombinant modified vaccinia virus Ankara-vectored vaccine expressing the consensus HIV-1 clade A Gag p24/p17 sequences and multiple CD8(+) T-cell epitopes during highly active antiretroviral therapy. We observed significant amplification and broadening of CD8(+) and CD4(+) gamma interferon responses to vaccine-derived epitopes in the vaccinees, without rebound viremia, but not in two unvaccinated controls followed simultaneously. Vaccine-driven CD8(+) T-cell expansions were also detected by tetramer reactivity, predominantly in the CD45RA(-) CCR7(+) or CD45RA(-) CCR7(-) compartments, and persisted for at least 1 year. Expansion was associated with a marked but transient up-regulation of CD38 and perforin within days of vaccination. Gag-specific CD8(+) and CD4(+) T-cell proliferation also increased postvaccination. These data suggest that immunization with MVA.HIVA is a feasible strategy to enhance potentially protective T-cell responses in individuals with chronic HIV-1 infection.

Identification of hepatitis C virus (HCV) 2a-derived epitope peptides having the capacity to induce cytotoxic T lymphocytes in human leukocyte antigen-A24+ and HCV2a-infected patients

Since virus-specific cytotoxic T lymphocytes (CTLs) play a critical role in preventing the spread of hepatitis C virus (HCV), vaccine-based HCV-specific CTL induction could be a promising strategy to treat HCV-infected patients. In this study, we tried to identify HCV2a-derived epitopes, which can induce human leukocyte antigen (HLA)-A24-restricted and peptide-specific CTLs. Peripheral blood mononuclear cells of HCV2a-infected patients or healthy donors were stimulated in vitro with HCV2a-derived peptides, which were prepared based on the HLA-A24 binding motif. As a result, three peptides (HCV2a 576-584, HCV2a 627-635, and HCV2a 1085-1094) efficiently induced peptide-specific CTLs from HLA-A24(+) HCV2a-infected patients as well as healthy donors. The cytotoxicity was exhibited by peptide-specific CD8(+) T cells in an HLA-A24-restricted manner. In addition, the HCV2a 627-635 peptide was frequently recognized by immunoglobulin G of HCV2a-infected patients. These results indicate that the identified three HCV2a peptides might be applicable to peptide-based immunotherapy for HLA-A24(+) HCV2a-infected patients.

Precursor frequency, nonlinear proliferation, and functional maturation of virus-specific CD4+ T cells

The early events regulating antiviral CD4 responses were tracked using an adoptive transfer model. CD4+ T cell expansion was nonlinear, with a lengthy lag phase followed by 2 days of explosive proliferation. A small number of naive Ag-specific CD4+ T cells were found in nonlymphoid tissues and, in the 8 days following infection, the number of activated cells increased in all tissues analyzed, and their effector functions matured. Finally, we show that a naive mouse contains approximately 100 naive CD4+ precursor cells specific for a single epitope, a precursor frequency of approximately 10(-5), similar to that of naive CD8+ T cells, indicating that the approximately 50-fold difference in size of the two responses to virus infection is determined by something other than the number of precursor cells.

Functional signatures in antiviral T-cell immunity for monitoring virus-associated diseases

At present, we only have indirect knowledge of the protective role of antigen-specific T cells in human viral infections, and it has been difficult to show a direct correlation between quantitative and qualitative measures of T-cell immunity and virus-associated diseases. However, as described in this Opinion article, recent advances in the characterization of T-cell functions and in the development of standardized T-cell assays have led to the identification of distinct functional signatures of T-cell responses that correlate with levels of viral replication and disease activity.

Interferon-gamma decreases replication of primary R5 HIV-1 isolates in thymocytes

As interferon-gamma (IFN-gamma) is produced at lower levels by neonatal than adult T cells, we determined whether IFN-gamma influences HIV-1 replication in thymocytes. IFN-gamma significantly decreased replication of R5 but not X4 viruses, and reduced depletion of CD3(hi)CD27 (mature) thymocytes, the preferential targets for R5 HIV-1. Thus infection and depletion of functionally mature thymocytes that can produce endogenous IFN-gamma may mutually contribute to HIV-1 replication in the thymus and to reduced T-cell output.

Viral and host immune regulatory mechanisms in hepatitis C virus infection

Recent studies suggest that liver inflammation in chronic hepatitis C virus (HCV) infection is controlled by several mechanisms, including host regulatory immune responses and viral polypeptides interacting with cells involved in innate and adaptive immunity. This article provides an overview about current thinking on host-pathogen symbiotic relationship in HCV infection and its significance with respect to pathogenesis. Special emphasis is given to regulatory T-cell subsets which have recently received attention and which are thought to play a major role in persistent viral infections such as HCV.

Selective lymphocyte depletion during the early stage of the immune response to foot-and-mouth disease virus infection in swine

Foot-and-mouth disease virus (FMDV) is the causative agent of a highly contagious vesicular disease of cloven-hoofed animals. In the present study we use FMDV serotype C infection of swine to determine, by analytical techniques, the direct ex vivo visualization of virus-infected immune cells during the first 17 days of infection. We report, for the first time, that FMDV C-S8c1 can infect T and B cells at short periods of time postinoculation, corresponding with the peak of the viremia. There is a significant lymphopenia that involves CD3(+) CD4(-) CD8(+/-), CD3(+) CD4(-) CD8(+)Tc, and CD3(+) CD4(+) CD8(+) memory Th but not CD3(+) CD4(+) CD8(-) naïve Th lymphocytes. In addition, a profound depletion of the vast majority of peripheral T cells in lymph nodes and spleen is observed. This selective depletion of T cells is not due mainly to in situ death via apoptosis as visualized by the terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) technique. Thus, early infection of T cells by FMDV may be the main cause of the observed T-cell depletion. Importantly, this lack of T cells is reflected in a reduced response to mitogen activation, which in many cases is totally eliminated. These data suggest a mechanism by which the virus causes a transient immunosuppression, subvert the immune systems, and spreads. These results have important implications for our understanding of early events in the development of a robust immune response against FMDV.

CD8+ and CD20+ lymphocytes cooperate to control acute simian immunodeficiency virus/human immunodeficiency virus chimeric virus infections in rhesus monkeys: modulation by major histocompatibility complex genotype

We have previously described two isogenic molecularly cloned simian immunodeficiency virus/human immunodeficiency virus chimeric viruses (SHIVs) that differ from one another by 9 amino acids and direct distinct clinical outcomes in inoculated rhesus monkeys. SHIV(DH12R-Clone 7), like other highly pathogenic CXCR4-tropic SHIVs, induces rapid and complete depletions of CD4+ T lymphocytes and immunodeficiency in infected animals. In contrast, macaques inoculated with SHIV(DH12R-Clone 8) experience only partial and transient losses of CD4+ T cells, show prompt control of their viremia, and remain healthy for periods of time extending for up to 4 years. The contributions of CD8+ and CD20+ lymphocytes in suppressing the replication of the attenuated SHIV(DH12R-Clone 8) and maintaining a prolonged asymptomatic clinical course was assessed by treating animals with monoclonal antibodies that deplete each lymphocyte subset at the time of virus inoculation. The absence of either CD8+ or CD20+ cells during the SHIV(DH12R-Clone 8) acute infection resulted in the rapid, complete, and irreversible loss of CD4+ T cells; sustained high levels of postpeak plasma viremia; and symptomatic disease in Mamu-A*01-negative Indian rhesus monkeys. In Mamu-A*01-positive animals, however, the aggressive, highly pathogenic phenotype was observed only in macaques depleted of CD8+ cells; SHIV(DH12R-Clone 8) was effectively controlled in Mamu-A*01-positive monkeys in the absence of B lymphocytes. Taken together, these results indicate that both CD8+ and CD20+ B cells contribute to the control of primate lentiviral infection in Mamu-A*01-negative macaques. Furthermore, the major histocompatibility complex genotype of an infected animal, as exemplified by the Mamu-A*01 allele in this study, has the additional capacity to shift the balance of the composite immune response.

T cell repertoire and Epstein-Barr virus-specific T cell response in chronic active Epstein-Barr virus infection: a case study

In a patient with chronic active Epstein-Barr virus infection associated with vasculitis and fulminant CD4+ T cell lymphoproliferative disorder, we probed the peripheral blood mononuclear cells (PBMC) for the presence of an EBV-specific T cell repertoire and tested the possible relationship between the lymphocytic infiltrate and the EBV-specific T cell response. Our results give credence to the presence of an apparently normal EBV-specific memory T cell response after in vitro reactivation of the patient's PBMC with autologous infected B lymphoblastoid cell lines. In keeping with the characterization of the vasculitis, certain T cell subsets were detected after expansion of skin lesion-infiltrating lymphocytes and were found to be infected with EBV. These particular T cell expansions were neither the effectors nor the targets of the in vitro reactivated EBV-specific T cells, thus excluding a simple relationship between EBV, the skin lesions, and the T cell expansions frequently observed in these patients.

Identification of HLA-A*3101-restricted cytotoxic T-lymphocyte response to human immunodeficiency virus type 1 (HIV-1) in patients with chronic HIV-1 infection

Virus-specific cytotoxic T-lymphocyte (CTL) responses are critical in the control of human immunodeficiency virus type 1 (HIV-1) infections. As several HIV-1 CTL epitopes restricted to many HLA types are already known, we aimed at identifying the CTL epitopes restricted by HLA-A*3101 in an effort to expand the epitope repertoire available for the development of potential T cell-mediated therapeutic measures and protective vaccines. Scanning of HIV-1 clade B SF2 strain proteins for the presence of peptides containing HLA-A*3101-binding motifs revealed 88 nine- to 11-mer peptides that had been synthesized and assayed for binding to HLA-A*3101 molecules. Peptides with medium to high HLA-binding affinity were tested for their ability to stimulate a CTL response in the peripheral blood mononuclear cells (PBMCs) from selected HIV-1-infected patients. Two of these binding peptides, Env769-779 (RLRDLLLIAAR) and Nef192-200 (KLAFHHMAR), induced peptide-specific CTLs in PBMCs from at least two of five HIV-1-seropositive individuals. CTL clones specific for the two peptides killed HLA-A*3101-expressing target cells infected with HIV-1 recombinant vaccinia virus, indicating that these peptides were naturally processed HLA-A*3101-restricted CTL epitopes. Identification of T-cell epitopes on HIV-1 proteins will increase our understanding of the role of CD8+ T cells in HIV-1 infections and assist in the design of new protective strategies.

[Difference and significance of peripheral blood T-lymphocyte subsets in patients with chronic hepatitis B and asymptomatic HBV carriers]

OBJECTIVE

To investigate the difference of peripheral blood T-lymphocyte subsets in patients with chronic hepatitis B and asymptomatic HBV carriers, and to analyze the relationship between the pathogenesis of hepatitis B and the hosts' cellular immunity.

METHODS

Flow cytometry was used to detect the peripheral blood T-lymphocyte subsets in 29 patients of chronic hepatitis B, 25 asymptomatic HBV carriers and 35 healthy blood donors.

RESULTS

Compared with normal controls, the numbers of leucocytes, lymphocytes, T-lymphocytes, CD4+ T cells, CD8+ T cells, CD4+CD28+ T cells and CD8+CD28+ T cells decreased in both the patients with chronic hepatitis B and asymptomatic HBV carriers, the number of NK cells of the patients with chronic hepatitis B decreased as well. Compared with normal controls and asymptomatic HBV carriers, the proportions of CD8+CD38+ T cells and CD4+CD45RA-memory T cells markedly increased and the proportion and number of CD4+CD45RA+62L+ T cells decreased in patients with chronic hepatitis B.

CONCLUSION

There is an imbalance in peripheral blood T-lymphocyte subsets and turbulence in cellular immunity in the patients with chronic hepatitis B and asymptomatic HBV carriers, which may be associated with HBV persistent infection.

Recall proliferation potential of memory CD8+ T cells and antiviral protection

Memory CD8+ T cells play a crucial role in mediating protection from infection with viruses and other intracellular pathogens. Memory T cells are not a homogenous cellular population and may be separated into central memory T cells with substantial recall proliferation capacity and effector memory T cells with limited recall proliferation capacity. It has been suggested that the protective capacity of effector memory T cells is more limited than that of central memory T cells in viral infections. Here, we show that pronounced recall proliferation potential is indeed key for protection against lymphocytic choriomeningitis virus, which replicates in central lymphoid organs and is controlled by contact-dependent lysis of infected cells. In contrast, recall proliferation competence is not sufficient for protection against vaccinia virus, which is replicating in peripheral solid organs and is controlled by cytokines. To protect against vaccinia virus, high numbers of effector-like T cells were required to be present in peripheral tissue before viral challenge. These data indicate that the protective capacity of different subpopulations of memory T cells may vary dependent on the nature and the route of the challenge infection, which must be considered in T cell-based vaccine design.

During viral infection of the respiratory tract, CD27, 4-1BB, and OX40 collectively determine formation of CD8+ memory T cells and their capacity for secondary expansion

Independent studies have shown that CD27, 4-1BB, and OX40 can all promote survival of activated CD8+ T cells. We have therefore compared their impact on CD8+ memory T cell formation and responsiveness within one, physiologically relevant model system. Recombinant mice, selectively lacking input of one or two receptors, were challenged intranasally with influenza virus, and the immunodominant virus-specific CD8+ T cell response was quantified at priming and effector sites. Upon primary infection, CD27 and (to a lesser extent) 4-1BB made nonredundant contributions to accumulation of CD8+ virus-specific T cells in draining lymph nodes and lung, while OX40 had no effect. Interestingly though, in the memory response, accumulation of virus-specific CD8+ T cells in spleen and lung critically depended on all three receptor systems. This was explained by two observations: 1) CD27, 4-1BB, and OX40 were collectively responsible for generation of the same memory CD8+ T cell pool; 2) CD27, 4-1BB, and OX40 collectively determined the extent of secondary expansion, as shown by adoptive transfers with standardized numbers of memory cells. Surprisingly, wild-type CD8+ memory T cells expanded normally in primed OX40 ligand- or 4-1BB ligand-deficient mice. However, when wild-type memory cells were generated in OX40 ligand- or 4-1BB ligand-deficient mice, their secondary expansion was impaired. This provides the novel concept that stimulation of CD8+ T cells by OX40 and 4-1BB ligand during priming imprints into them the capacity for secondary expansion. Our data argue that ligand on dendritic cells and/or B cells may be critical for this.

V3 loop-determined coreceptor preference dictates the dynamics of CD4+-T-cell loss in simian-human immunodeficiency virus-infected macaques

We used experimental infection of rhesus macaques with envelope gp120 V3 loop isogenic simian-human immunodeficiency virus (SHIV) molecular clones to more clearly define the impact of human immunodeficiency virus type 1 coreceptor usage in target cell selectivity and the rates of CD4+-T-cell depletion. Functional assays demonstrate that substitution of the V3 loop of the pathogenic CXCR4-tropic (X4) SHIV(SF33A2) molecular clone with the corresponding sequences from the CCR5-tropic (R5) SHIV(SF162P3) isolate resulted in a switch of coreceptor usage from CXCR4 to CCR5. The resultant R5 clone, designated SHIV(SF33A2(V3)), is replication competent in vivo, infecting two of two macaques by intravenous inoculation with peak viremia that is comparable to that seen in monkeys infected with X4-SHIV(SF33A2). But while primary infection with the X4 clone was accompanied by rapid and significant loss of peripheral and secondary lymphoid CD4+ T lymphocytes, infection with R5-SHIV(SF33A2(V3)) led to only a modest and transient loss. However, substantial depletion of intestinal CD4+ T cells was observed in R5-SHIV(SF33A2(V3))-infected macaques. Moreover, naïve T cells that expressed high levels of CXCR4 were rapidly depleted in X4-SHIV(SF33A2)-infected macaques, whereas R5-SHIV(SF33A2(V3)) infection mainly affected memory T cells that expressed CCR5. These findings in a unique isogenic system illustrate that coreceptor usage is the principal determinant of tissue and target cell specificity of the virus in vivo and dictates the dynamics of CD4+-T-cell depletion during SHIV infection.

Nucleofection of non-B cells with mini-Epstein-Barr virus DNA

A tumor-specific cell surface localization of heat shock protein 70 (Hsp70) on CX+ colon carcinoma cells provides a recognition structure for NK cells but not for NKT and T cells. Incubation with low-dose IL-2 plus Hsp70-peptide TKD enhances production and release of granzyme B by NK cells and thus renders Hsp70-positive tumors more sensitive to their cytolytic attack. To provide the experimental basis for the generation of Hsp70-reactive NK cell lines we established a modified nucleofection technique as a rapid and efficient method for gene transfer into non-B cells. Therefore, TKD-stimulated, CD3/CD19-depleted effector cells, consisting of 85% CD3- CD16/56+ NK cells, 1.4% CD3+ CD16/56+ NKT cells, and 0.3% CD3+ CD16/56- T cells were nucleofected with the green fluorescent protein (GFP)-containing mini-Epstein-Barr virus (mini-EBV) plasmid p2667 (1478.A d2GFP). GFP, a marker for the expression of EBV-associated genes, became visible for the first time on day 18 after transfection. On day 28 mini-EBV-transfected cells consisted of 49% NKT, 38% T cells, and 13% NK cells; no contaminating B cells were detectable. Even 1.5 years after transfection GFP and CD94 were found to be co-expressed on transfectants. These data indicated that mini-EBV provides a useful tool for the nucleofection of non-B cells. The cytolytic activity of NK-transfectants towards Hsp70 membrane-positive CX+ tumor cells was comparable to that of non-transfected effector cells. In summary, our results might provide the basis for the generation of non-B effector cell lines including NK cells with conserved Hsp70-reactivity.

Immunoproteasome-deficient mice mount largely normal CD8+ T cell responses to lymphocytic choriomeningitis virus infection and DNA vaccination

During viral infection, constitutive proteasomes are largely replaced by immunoproteasomes, which display distinct cleavage specificities, resulting in different populations of potential CD8(+) T cell epitope peptides. Immunoproteasomes are believed to be important for the generation of many viral CD8(+) T cell epitopes and have been implicated in shaping the immunodominance hierarchies of CD8(+) T cell responses to influenza virus infection. However, it remains unclear whether these conclusions are generally applicable. In this study we investigated the CD8(+) T cell responses to lymphocytic choriomeningitis virus infection and DNA immunization in wild-type mice and in mice lacking the immunoproteasome subunits LMP2 or LMP7. Although the total number of virus-specific cells was lower in LMP2 knockout mice, consistent with their having lower numbers of naive cells before infection, the kinetics of virus clearance were similar in all three mouse strains, and LMP-deficient mice mounted strong primary and secondary lymphocytic choriomeningitis virus-specific CD8(+) T cell responses. Furthermore, the immunodominance hierarchy of the four investigated epitopes (nuclear protein 396 (NP(396)) > gp33 > gp276 > NP(205)) was well maintained. We observed a slight reduction in the NP(205)-specific response in LMP2-deficient mice, but this had no demonstrable biological consequence. DNA vaccination of LMP2- and LMP7-deficient mice induced CD8(+) T cell responses that were slightly lower than, although not significantly different from, those induced in wild-type mice. Taken together, our results challenge the notion that immunoproteasomes are generally needed for effective antiviral CD8(+) T cell responses and for the shaping of immunodominance hierarchies. We conclude that the immunoproteasome may affect T cell responses to only a limited number of viral epitopes, and we propose that its main biological function may lie elsewhere.

Cytotoxic capacity of hepatitis C virus (HCV)--specific lymphocytes after in vitro immunization with HCV-derived lipopeptides

BACKGROUND

Hepatitis C virus (HCV)-derived lipopeptides can induce epitope-specific immune responses in lymphocytes from HCV-naive individuals. We analyzed whether such T cells generated by in vitro immunization with HCV core-derived lipopeptides exert HCV-specific cytolytic activity.

METHODS

Using a sensitive flow cytometric cytotoxicity assay we characterized HCV-specific cytotoxicity in T cells generated in vitro with HCV core-derived 25-mer lipopeptides. In addition, we studied expressions of Fas ligand and perforin and interferon-gamma (IFN-gamma) secretion in HLA-A2-HCV(core_35-44) tetramer-positive T cells generated with lipopeptide amino acid 20-44 (LP20-44).

RESULTS

CD8+ T cells induced in vitro with HCV core-derived lipopeptides only infrequently exerted HCV-specific cytotoxicity, irrespective of whether antigen-coated T2 cells or autologous B lymphoblasts were used as targets. Detailed analysis of HLA-A2-HCV(core_35-44) tetramer-positive T cells generated with LP20-44 revealed that in vitro immunization resulted in T cells that secreted IFN-gamma after antigen-specific restimulation and that upregulated expression of Fas ligand but not of perforin.

CONCLUSIONS

Our data confirm at the functional level that HCV lipopeptides induce antigen-specific T lymphocytes that produce IFN-gamma but exert significant cytotoxicity in only a minority of experiments, probably because expression of cytolytic effector molecules is not enhanced in their granules.

Isolation of human immunodeficiency virus type 2 biological clones from peripheral blood lymphocytes

Infectious variants of human immunodeficiency virus (HIV) can be isolated from peripheral blood mononuclear cells (PBMC) of infected individuals by propagating the virus in co-cultures with healthy donor PBMC. Standardized culture protocols have been designed specifically for the isolation of HIV type 1 (HIV-1) and proven effective for the isolation of virus from virtually all HIV-1-infected individuals. For the isolation of HIV-2, however, standard HIV-1 culture protocols have been only partially effective. While suitable for the isolation of HIV-2 from PBMC of individuals in advanced stages of disease, they appeared largely inadequate for the isolation of HIV-2 from asymptomatically HIV-2-infected individuals. This chapter describes a variant HIV isolation procedure with culture conditions adapted to the isolation of HIV-2 from PBMC of "healthy" HIV-2-infected individuals, i.e., individuals with high CD4+ T-cell numbers and no detectable viral RNA in plasma. By using a limiting dilution format, several biological clones representing individual HIV variants can be obtained from the PBMC of an infected individual. In addition, the frequency of PBMC infected with HIV-2 variants capable of propagating in vitro can be estimated.

Angioimmunoblastic T cell lymphoma with an unusual proliferation of Epstein-Barr virus-associated large B cells arising in a patient with progressive systemic sclerosis

We report an unusual case of angioimmunoblastic T cell lymphoma arising in the setting of 5 years of immunosuppressive treatment for progressive systemic sclerosis. The lymph node lesion was accompanied by large blastic B cells with an association of Epstein-Barr virus. Southern blot study demonstrated the clonal rearrangement of T cell receptor beta-chain gene, but not of immunoglobulin heavy chain gene. Phenotypical examination of the lymph node also revealed the predominance of CD4+ T cells in addition to the proliferation of follicular dendritic cells, but no light chain restriction in large B cell components. In the clinical and laboratory aspects, neutrophilia (15.8 x 10(9)/l) and plasmacytosis (40%) in bone marrow were noted, which were considered to be closely related to elevated serum granulocyte colony-stimulating factor, interleukin (IL)-4 and IL-6. Based on the combined data described here, our preferred diagnosis was angioimmunoblastic T cell lymphoma with Epstein-Barr virus-associated B cell lymphoproliferative disorder, the pathogenesis of which was suggested to be closely associated with immunosuppressive treatment for progressive systemic sclerosis.

Immune responses and protection by vaccine and various vaccine adjuvant candidates to virulent porcine reproductive and respiratory syndrome virus

Various vaccine adjuvant candidates were assessed with the modified-live porcine reproductive and respiratory syndrome virus (MLV PRRSV) (Ingelvac PRRS MLV) vaccine. Their influence on humoral-mediated immune (HMI) and cell-mediated immune (CMI) responses as well as protection from virulent PRRSV challenge (MN-184) was evaluated. Ninety seronegative pigs were randomly divided into nine groups of 10 pigs. One group received MLV vaccine alone. Five groups received MLV vaccine with either bacterial endotoxin-derived adjuvant (ET), mixed open reading frame 5 (ORF5) peptides derived from various PRRSV isolates, porcine interferon alpha (IFNalpha), polyinosinic-polycytidylic acid stabilized with polylysine and carboxymethylcellulose (poly-ICLC), or porcine interleukin-12 (IL-12). One group did not receive MLV vaccine but was immunized with ORF5 peptides conjugated with cholera toxin (ORF5 peptide/CT). Two groups served as challenged and unchallenged non-vaccinated controls. Four-color flow cytometry was utilized to simultaneously identify three major porcine T-cell surface markers (CD4, CD8, and gammadelta TCR) and detect activation marker CD25 (alpha chain of IL-2 receptor) or intracellular IFNgamma. The MLV PRRSV vaccine alone successfully primed CD4(-)CD8(+)gammadelta- T-cells as demonstrated by a significant increase in %IFNgamma+ cells when live PRRSV was used as a recall antigen. Booster immunizations of mixed ORF5 peptides and co-administration of IL-12 with MLV PRRSV vaccine significantly enhanced IFNgamma expression by some T-cell subsets (CD4(-)CD8(+)gammadelta+ and CD4(-)CD8(-)gammadelta+ for mixed ORF5 peptides and CD4(+)CD8(+)gammadelta- and CD4(-)CD8(+)gammadelta+ for IL-12). All groups receiving MLV-vaccine with or without adjuvants had reduced lung lesions after challenge. The group immunized with only ORF5 peptide/CT did not have significant T-cell recall responses and was not protected from challenge. Expression of IFNgamma by several T-cell subsets correlated with reduced lung lesions and viremia, whereas expression of CD25 did not. Expression of surface CD25 did not correlate with IFNgamma production. PRRSV ELISA s/p ratio prior to challenge also correlated with reduced lung lesions and viremia. In conclusion, booster immunizations of the mixed ORF5 peptides and co-administration of IL-12 effectively enhanced the CMI response to MLV vaccine. However, neither adjuvant significantly contributed to reducing clinical effects when compared to MLV alone.

γδ Lymphocyte Response to Porcine Reproductive and Respiratory Syndrome Virus

Porcine reproductive and respiratory syndrome virus (PRRSV) continues to be one of the most important diseases facing swine industry today. Following PRRSV infection pigs develop both humoral and cell-mediated responses following PRRSV exposure; however, the relative importance in protection and clearance of the virus is not yet completely understood. Swine contain a large percentage of gammadelta T-lymphocytes in peripheral circulation capable of responding to various pathogens in both an innate and specific immune response. The objectives of this study were to determine whether gammadelta lymphocytes functionally respond to PRRSV upon initial exposure and re-exposure. Four month old PRRSV free gilts were intranasally inoculated with a field isolate MN-30100 then assessed at various time points post infection. On day 120, pigs were re-exposed with MN-30100 PRRSV strain and subsequently were bled on days 0, 7, and 14 post re-exposure. Lymphocyte subpopulations, antigen specific proliferation, and IFN-gamma production were evaluated throughout the study. Circulating gammadelta lymphocytes in PRRSV exposed animals expanded between days 14 to 70 (d14-d70, p = 0.016); following antigen stimulation, gammadelta lymphocyte proliferated by day 14 (d0-d14, p = 0.001) continuing through day 60. gammadelta lymphocytes produced IFN-gamma by day 14 pi continuing through day 50 (d0-d50, p = 0.004). Following re-exposure both gammadelta+ and CD4+ lymphocytes increased in IFN-gamma production. These results are not fully conclusive on the role of gammadelta lymphocytes against PRRSV; the data indicate that gammadelta lymphocytes specifically respond to PRRSV.

Detection of the meq gene in the T cell subsets from chickens infected with Marek's disease virus serotype 1

The meq gene was thought to be only detected in Marek's disease virus serotype 1 (MDV 1) including a very virulent strain, Md5, while L-meq, in which a 180-bp sequence is inserted into the meq open reading frame, is found in other strains of MDV 1, such as CVI 988/R6. However, both meq and L-meq were previously detected by PCR in chickens infected with MDV 1, suggesting that MDV 1 may consists of at least two subpopulations, one with meq, the other with L-meq. To further analyze these subpopulations, we analyzed the time course changes in distribution of these subpopulations among T cell subsets from chickens infected with MDV 1. Both meq and L-meq were detected in CD4+ and CD8+ T cells infected with strain Md5 or CVI 988/R6. The shift in MDV subpopulations from one displaying meq to the other displaying L-meq and/or the conversion from meq to L-meq occurred mainly in the CD8+ T cell subset from Md5-infected chickens. PCR products corresponding to L-meq rather than meq were frequently amplified from the CD8+ T cell subset from CVI 988/R 6 -infected chickens. These results suggest that a dominant subpopulation of MDV 1 changes depending on the T cell subsets, and that L-meq is dominantly present in the CD8+ T cells which play a role in the clearance of pathogenic agents.

Induction of prolonged survival of CD4+ T lymphocytes by intermittent IL-2 therapy in HIV-infected patients

HIV infection leads to decreases in the number of CD4 T lymphocytes and an increased risk for opportunistic infections and neoplasms. The administration of intermittent cycles of IL-2 to HIV-infected patients can lead to profound increases (often greater than 100%) in CD4 cell number and percentage. Using in vivo labeling with 2H-glucose and BrdU, we have been able to demonstrate that, although therapy with IL-2 leads to high levels of proliferation of CD4 as well as CD8 lymphocytes, it is a remarkable preferential increase in survival of CD4 cells (with half-lives that can exceed 3 years) that is critical to the sustained expansion of these cells. This increased survival was time-dependent: the median half-life, as determined by semiempirical modeling, of labeled CD4 cells in 6 patients increased from 1.7 weeks following an early IL-2 cycle to 28.7 weeks following a later cycle, while CD8 cells showed no change in the median half-life. Examination of lymphocyte subsets demonstrated that phenotypically naive (CD27+CD45RO-) as well as central memory (CD27+CD45RO+) CD4 cells were preferentially expanded, suggesting that IL-2 can help maintain cells important for host defense against new antigens as well as for long-term memory to opportunistic pathogens.