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Objectives Infections are a major cause of mortality after allogeneic haemopoietic stem cell transplantation (alloHSCT), and immune recovery is necessary for prevention. Novel transplant procedures have changed the epidemiology of infections but contemporary data on functional immune recovery are limited. In this pilot study, we aimed to measure immune recovery in the current era of alloHSCT. Methods Twenty, 13, 11, 9 and 9 alloHSCT recipients had blood collected at baseline (time of conditioning) and 3‐, 6‐, 9‐, and 12‐months post‐alloHSCT, respectively. Clinical data were collected, and immune recovery was measured using immunophenotyping, lymphocyte proliferation, cytokine analysis and antibody isotyping. Results Median absolute T‐ and B‐cell counts were below normal from baseline until 9‐ to 12‐months post‐alloHSCT. Median absolute CD4+ T‐cell counts recovered at 12‐months post‐alloHSCT. Positive proliferative responses to Aspergillus, cytomegalovirus (CMV), Epstein‐Barr virus (EBV), influenza and tetanus antigens were detected from 9 months. IL‐6 was the most abundant cytokine in cell cultures. In cultures stimulated with CMV, EBV, influenza and tetanus peptides, the CD4+ T‐cell count correlated with IL‐1β (P = 0.045) and CD8+ T‐cell count with IFNγ (P = 0.013) and IL‐1β (P = 0.012). The NK‐cell count correlated with IL‐1β (P = 0.02) and IL‐17a (P = 0.03). Median serum levels of IgG1, IgG2 and IgG3 were normal while IgG4 and IgA were below normal range throughout follow‐up. Conclusions This pilot study demonstrates that immune recovery can be measured using CD4+ T‐cell counts, in vitro antigen stimulation and selected cytokines (IFNγ, IL‐1β, IL‐4, IL‐6, IL‐17, IL‐21, IL‐31) in alloHSCT recipients. While larger studies are required, monitoring immune recovery may have utility in predicting infection risk post‐alloHSCT.

Background and Aim T-cell responses against hepatitis C are believed to be critical in achieving both natural and treatment-induced clearance. However, rapid clearance of antigen with early treatment of primary infection may result in reduced or poorly sustained cellular immunity. This study longitudinally examined Th1 and Th2 hepatitis C virus (HCV)-specific cytokine production and T-cell effector function from subjects enrolled in the Australian Trial in Acute Hepatitis C comparing three groups: treatment-induced clearance (sustained virological response [SVR]), treatment non-response, and untreated spontaneous clearance. Methods HCV-specific T-cell responses were characterized by HCV peptide ELISpot, in vitro cytokine production, and T-cell flow cytometry assays. Results Treated subjects with a sustained virological response (SVR) displayed a better maintenance of HCV-specific Th1 responses compared to treatment non-responders (higher interferon [IFN]-γ and interleukin (IL)-2 magnitude at week 24, broader IFN-γ responses at weeks 24 and 48, P < 0.05) and significantly increased IFN-γ responses between screening and week 48 (magnitude P = 0.026, breadth P = 0.009). Treatment-induced viral clearance was also associated with a trend toward decreased IL-10 responses (screening to week 48, P = 0.070), higher expression of CD45RO (P = 0.042) and CD38 (P = 0.088) on CD4+ T cells, and higher IFN-γR expression (CD56+IFN-γR+ P = 0.033) compared to treatment non-responders. Untreated subjects with viral clearance also displayed high magnitude and broad HCV-specific IFN-γ and IL-2 responses early in infection; however, IFN-γ responses were not as well maintained compared to treated subjects with a SVR (week 48 magnitude, breadth P = 0.064). Conclusion Treatment-induced viral clearance of recent HCV infection is associated with maintenance of HCV-specific Th1 responses.

The critical events in clearance or persistence of hepatitis C virus (HCV) infection are unknown but likely to be determined early in acute infection. Type 1 and type 2 cytokine production was assessed by HCV peptide ELISpot and multiplex in vitro cytokine production assays in longitudinally collected samples from 20 untreated participants enrolled in the Australian Trial in Acute Hepatitis C (ATAHC); a prospective cohort of acute HCV infection (77% injecting drug users, IDU). Significantly higher interleukin-10 (IL-10) production (P = 0.048), in the relative absence of interferon-gamma (IFN-γ) and IL-2 production, was present early in HCV infection in those who progressed to chronic infection. In contrast, viral clearance was associated with a greater magnitude and broader specificity of IFN-γ (magnitude P < 0.001, breadth P = 0.004) and IL-2 responses, in the relative absence of IL-10. Early IL-10 production was correlated with higher HCV RNA level at baseline (P = 0.046) and week 12 (P = 0.018), while IFN-γ and IL-2 production was inversely correlated with HCV RNA level at baseline (IFN-γ P = 0.020, IL-2 P = 0.050) and week 48 (IFN-γ P = 0.045, IL-2 P = 0.026). Intracellular staining (ICS) indicated the HCV-specific IFN-γ response was primarily from CD8(+) T cells and NK cells, whereas IL-10 production was predominantly from monocytes, with a subset of IL-10 producing CD8(+) T cells present only in those who progressed to chronic infection. IL-10, an immunoregulatory cytokine, appears to play a key role in progression to chronic HCV infection.

Effective treatment of celiac disease is an unmet medical need. A glutenase that destroys immunogenic gluten peptides may be clinically valuable. Twenty patients with celiac disease were randomly assigned to ingest a large gluten meal (16 g daily for 3 days) pre-treated with ALV003, a mixture of highly specific glutenases (n=10), or pre-treated with placebo (n=10). Peripheral blood T-cell IFN-gamma ELISpot responses to gliadin and an immunogenic 33mer and symptoms were assessed. While baseline IFN-gamma ELISpot responses to gliadin and the 33mer were negative in all patients, a significant ELISpot response to gliadin or the 33mer was observed in 6 of 10 patients consuming placebo-treated gluten and 0 of 10 consuming ALV003 pre-treated gluten (p=0.011). Symptoms typically associated with gluten ingestion occurred in both groups and were not significantly reduced by ALV003 pre-treatment. ALV003 pre-treatment can abolish immune responses induced by gluten in patients with celiac disease.

Background Cellula r immune responses play a critical role in providing help for the production of neutralizing antibodies to influenza virus, as well as producing anti-viral cytokines and killing infected cells in the lung. Heterosubtypic T-cell responses between different subtypes of influenza have been shown to exist in humans and to provide protection against morbidity and mortality associated with H5N1 infection in animal challenge models. Therefore, existing T-cell responses induced by natural infection or vaccination in humans may provide some degree of protection from infection with H5N1 strains, or may attenuate the severity of disease. Objectives To investigate heterosubtypic T-cell responses to avian influenza in humans. Methods T-cell responses to an overlapping set of H5 HA peptides and inactivated viruses (H1N1, H3N2 and H5N1) were assessed using IFN-γ and IL-2 enzyme-linked immunospot (ELISpot) assays in a cohort of adults either vaccinated against seasonal influenza in the last 3 years (n = 20) or previously infected (n = 40). Results T-cell responses to all three subtypes of virus were found in both infected and vaccinated individuals by IFN-γ and IL-2 ELISpot assays. Approximately half of the participants from each group had a positive T-cell response to the H5 HA peptides in the IFN-γ or IL-2 ELISpot assay. Conclusions Heterosubtypic T-cell responses to H5 HA occur quite frequently in vaccinated and infected individuals. Further investigation of these responses and what role they may play upon challenge or vaccination against H5N1 may assist in vaccine design for avian influenza.

Individuals infected with hepatitis C virus (HCV) have two possible outcomes of infection, clearance or persistent infection. The focus of this review is the host mechanisms that facilitate clearance. The interaction between HCV viral components and the immune system ultimately determines the balance between the virus and host. Strong evidence points to the aspects of cellular immune response as the key determinants of outcome. The recent discovery of viral evasion strategies targeting innate immunity suggests that the interferon-alpha/beta induction pathways are also critical. A growing body of evidence has implicated polymorphisms in both innate and adaptive immune response genes as determinants of viral clearance in individuals infected with HCV.

Background. Primary Epstein-Barr virus (EBV) infection causes a spectrum of characteristics that range from asymptomatic seroconversion to severe infectious mononucleosis (IM), sometimes with prolonged symptoms and disability. We examined the relationships between clinical course, number of viral copies, and immunological parameters in a prospective cohort of subjects with recent IM. Methods. Eight case patients with at least 6 months of disabling symptoms and 31 matched control subjects who had recovered promptly were included. Symptom scores were recorded at regular intervals over the course of 12 months. Cellular EBV load, EBV-specific antibody responses, lymphocyte subsets, and EBV-specific interferon (IFN)‐g induction were measured. Results. In case patients with prolonged illness, the severity of acute-phase symptoms was greater, the development of anti‐EBV nuclear antigen‐1 immunoglobulin G was more rapid, and the time to development of the peak IFN-g response to the majority of latent-cycle EBV peptides was generally slower than those in control subjects. However, in both groups, neither viral nor immune parameters correlated with the severity or duration of symptoms. Conclusions. The resolution of symptomatic IM is not determined by control of viremia, nor is it easily explained by altered host responses to EBV infection. The detailed determinants of delayed recovery remain to be elucidated.

Ex vivo effector cytotoxic T-lymphocyte (CTL) activity was assessed in 27 members of the Australian Long-Term Nonprogressor cohort and correlated with genetic, virological, and immunological markers. The 27 individuals were antiretroviral naive with CD4(+) T-cell counts of >500 cells/ microl for more than 8 years after human immunodeficiency virus type 1 (HIV-1) infection. Effector CTL activity was determined using a standard ex vivo chromium release assay. Individuals with CTL activity (HIV-1 env(IIIB) or pol or gag) were then compared to those without CTL activity in relation to plasma HIV-1 RNA, ICD p24 antigen, beta(2)-microglobulin, CD4 and CD8 T-cell counts, CCR5 and CCR2b genotypes, and progression to CD4

Heat shock protein (HSP) expression in lymphocytes isolated from 20 patients with HIV disease and 15 age-matched controls was determined. Fold increases in lymphocyte hsp70 expression after heat shock were 4.52 +/- 2.97 in HIV-positive individuals compared with 2.60 +/- 1.29 for HIV-negative controls (P= 0.001). Given clear roles for HSP in the cross-presentation of antigens, alpha-defensin internalization and pro-inflammatory cytokine production, a further investigation of HSP in HIV patients is merited.

The role of cytotoxic T lymphocytes (CTL) in limiting viral replication and producing hepatocellular injury in patients with chronic hepatitis C virus (HCV) infection is controversial.Intrahepatic and peripheral blood HCV-specific CTL activity against the entire HCV polyprotein was assessed in 26 patients. CTL responses were assessed after effector lymphocytes were re-stimulated for 6 days in vitro using HCV-vaccinia virus-infected autologous cells expressing HCV antigens. Serum and hepatic viral loads were measured and immunohistochemistry for CD3 and CD8 was performed to localise and enumerate effector cells in liver.A positive CTL response was detected in 39/52 (75%) of assays conducted with intrahepatic mononuclear cells and 21/52 (40%) of peripheral blood assays (P0.001). The presence of an intrahepatic CTL response was associated with low hepatic viral load (P=0.004). Hepatic lobular infiltration by CD8(+)T cells correlated weakly with serum alanine aminotransferase levels (r=0.42, P=0.04) and no relationship was demonstrated between CTL activity and histological evidence of liver damage.HCV-specific CTL activity is found more commonly in liver than in blood. An inverse relationship between CTL responses and viral load supports the hypothesis that HCV-specific CTL limit viral replication in patients with chronic HCV infection.

X-linked severe combined immunodeficiency (XSCID) is a lethal disease resulting in death in infancy. In many instances, haploidentical bone marrow transplantation (BMT) offers reconstitution of T-cell immunity alone, with residual hypogammaglobulinaemia. The exact nature of B-cell dysfunction in these patients is unclear, although differentiation arrest of the B cells is a potential explanation. To ascertain the differentiation status of peripheral blood B lymphocytes from XSCID patients after BMT, the surface expression of CD19, CD10, CD34, CD5, serum immunoglogulin (sIg)M, sIgD, sIgG and CD27 on these B cells was investigated using three-colour flow cytometry. CD27 is a marker of memory B cells. Populations of CD19+IgM−D− B cells, CD19+IgM-only, CD19+IgG+CD27+ and CD19+IgM+ CD27+ B cells were found to be diminished in the XSCID patients after BMT with persistent hypogammaglobulinaemia, compared with both post-BMT patients with B-cell function and age-matched normal controls. This indicated the lack of CD19+IgM−D− B cells, which represent Ig isotype-switched B cells, as well as CD19+IgM-only and CD19+IgG+CD27+ or CD19+IgM+CD27+ memory B-cell populations. Interaction between CD27 and its ligand CD70 has been shown to induce IgG and IgM production by CD27+ B cells. Therefore, the lack of CD27/70 interaction is a probable explanation for the hypogammaglobulinaemia in these patients after BMT.

BACKGROUND The beta-chemokine receptor CCR-5 is used as a coreceptor by macrophage-tropic strains of HIV-1 to gain entry into CD4+ cells. OBJECTIVE To determine the effect of a common 32 base-pair deletion mutation in the CCR-5 gene (CCR-5 delta 32) on progression of HIV infection to AIDS, and to assess the level of heterozygosity for this mutation in a well-defined group of long-term non-progressors (LTNP). PARTICIPANTS Sixty-four HIV-1-infected LTNP (CD4+ T lymphocyte count > 500 x 10(6)/l after 8 years) were compared with 95 individuals infected within a similar period (1983-1986) but who had rapidly progressed to AIDS and death, and with a further 120 HIV-positive individuals with CD4+ counts < 500 x 10(6)/l. METHODS The presence of the CCR-5 delta 32 mutation was assessed using polymerase chain reaction with primers spanning the 32 base-pair deletion. CD4+ and CD8+ counts, plasma HIV-1 RNA, p24 antigen and beta 2-microglobulin levels in LTNP carrying the CCR-5 delta 32 mutation were compared with LTNP lacking the mutation. RESULTS A marked increase in the frequency of CCR-5 delta 32 heterozygosity was found among LTNP (35.9%) compared with rapid progressors (12.6%; P = 0.0005) and patients selected on the basis of a CD4+ T-cell count < 500 x 10(6)/l (12.5%; P = 0.0004). LTNP heterozygous for CCR-5 delta 32 had a significantly higher CD8+ T-cell count than those without the mutation (1218 versus 972 x 10(6)/l; P = 0.044). No significant correlation was observed between heterozygosity and CD4 count, viral load, p24 antigen or beta 2-microglobulin within the LTNP group. CONCLUSIONS This study provides the strongest evidence to date for the importance of a single copy of the CCR-5 delta 32 mutation in long-term non-progression of HIV infection, which may involve, in part, CD8+ T lymphocytes.

Initially, the immune system controls HIV infection, but over time the virus depletes the population of CD4+ T cells and disturbs the homoeostasis and function of other cells in the immune system. Extensive destruction of the immune system eventually leaves the body defenceless.

Coinfection with human immunodeficiency virus (HIV) and hepatitis C virus (HCV) has detrimental effects on HCV disease progression, including increased HCV RNA levels, promotion of viral persistence in primary infection, and faster progression to cirrhosis and hepatocellular carcinoma [1]. HIV/HCV coinfection has also been associated with a significant reduction in the response to HCV antiviral treatment [2]. Individuals with primary HCV infection who undergo spontaneous clearance have an initial robust CD4+ helper cell response, whereas those who develop viral persistence have a poorer response, which diminishes overtime [3]. However, studies addressing the impact of coinfection on the effector function of HCV-specific T cells in acute HCV infection are limited. A small study by van den Burg et al reported a valuable role for HCV-specific CD4+ T-cell responses targeting HCV nonstructural (NS) proteins in reduction of HCV RNA (n = 2) and resolution of HCV (n = 1) in subjects with acute HIV/HCV coinfection [4]. Schnuriger et al demonstrated a similar finding, wherein HCV-specific proliferative responses (particularly against NS4) were associated with lower HCV RNA levels and spontaneous clearance of HCV in HIV/HCV-coinfected subjects [5]. Interestingly, IFN-γ responses were not associated with HCV clearance or with CD4+ T-cell counts [5]. More recently Thomson et al reported a trend for spontaneous clearance of acute HCV infection, in HIV-positive men, associated with higher CD4+ T-cell counts and stronger T-cell responses within the first 3 months of HCV infection [6]. Even fewer studies, have directly compared acute HCV-specific T-cell responses between HIV/HCV coinfection and HCV monoinfection. Danta et al demonstrated a lower frequency of HCV-specific IFN-γ production in HIV/HCV-coinfected subjects compared with internationally recruited HCV-monoinfected controls, although there was no difference in the magnitude of IFN-γ production between the cohorts [7]. These studies raise the question of whether the detrimental effects of HIV/HCV coinfection on HCV clearance could be attributed to a lack of CD4+ T-cell help, which is important in the generation and maintenance of CD8+ T-cell responses [8], to an altered cytokine environment, or both. Our objective was to determine whether the magnitude and breadth of the HCV-specific cellular immune responses in acute HCV infection is affected by HIV/HCV coinfection by directly comparing HCV-specific T-cell responses in subjects with acute HCV infection with or without HIV infection, recruited simultaneously within the Australian Trial in Acute Hepatitis C (ATAHC).

SUMMARY Serum-free culture conditions to generate immature human monocyte-derived DC (Mo-DC) were optimized, and the parameters that influence their maturation after exposure to lipopeptides containing CD4(+) and CD8(+) T-cell epitopes were examined. The lipopeptides contained a single CD4(+) helper T-cell epitopes, one of a number of human leucocyte antigen (HLA)-A2-restricted cytotoxic T-cell epitope and the lipid Pam2Cys. To ensure complete maturation of the Mo-DC, we examined (i) the optimal lipopeptide concentration, (ii) the optimal Mo-DC density and (iii) the appropriate period of exposure of the Mo-DC to the lipopeptides. The results showed that a high dose of lipopeptide (30 microm) was no more efficient at upregulating maturation markers on Mo-DC than a low dose (6 microm). There was an inverse relationship between Mo-DC concentration and the mean fluorescence intensity of maturation markers. In addition, at the higher cell concentrations, the chemotactic capacity of the Mo-DC towards a cognate ligand, CCL21, was reduced. Thus, high cell concentrations during lipopeptide exposure were detrimental to Mo-DC maturation and function. The duration of exposure of Mo-DC to the lipopeptides had little effect on phenotype, although Mo-DC exposed to lipopeptides for 48 rather than 4 h showed an increased ability to stimulate autologous peripheral blood mononuclear cells to release interferon-gamma in the absence of exogenous maturation factors. These findings reveal conditions for generating mature antigen-loaded DC suitable for targeted immunotherapy.

Background HIV-specific cellular immune responses have been detected in some uninfected infants born to HIV-infected women, indicating transient virus exposure or replication has occurred. Small quantities of maternal blood pass into the infant's circulation during childbirth, termed “microtransfusion”, potentially facilitating viral exposure. We sought to determine the occurrence of microtransfusion and HIV-specific immune responses as an indicator of viral exposure in a cohort of uninfected infants born to HIV-infected women, in the context of interventions.

Induction of high levels of broadly reactive cytotoxic T lymphocytes (CTL) remains a promising approach for an effective HIV-1 vaccine. We have developed a novel genetic-based vaccine strategy that encodes consensus overlapping peptide sets from all HIV-1 proteins scrambled together. This synthetic scrambled antigen vaccine (SAVINE) strategy has significant advantages, e.g. capacity to encode more antigens safely and is very flexible compared to traditional isolate-based strategies. The SAVINE vaccine strategy is clearly immunogenic, being able to restimulate a range of human HIV-1 specific responses in vitro and induce HIV-1 specific immunity in vivo in mice. Interestingly, different in vivo delivery strategies affected the resulting immunity and immunodominance pattern in mice. This platform strategy could be used for other infections and cancers where T cell responses are important for protection.

Induction of HIV-specific T-cell responses by vaccines may facilitate efficient control of HIV. Plasmid DNA vaccines and recombinant fowlpoxvirus (rFPV) vaccines are promising HIV-1 vaccine candidates, although either vaccine alone may be insufficient to protect against HIV-1. A consecutive immunisation strategy involving priming with DNA and boosting with rFPV vaccines encoding multiple common HIV-1 antigens was further evaluated in 30 macaques. The DNA vaccine vector included CpG immunostimulatory molecules, and rFPV vaccines were compared with rFPV vaccines co-expressing the pro-T cell cytokines IFNgamma or IL-12. Vaccines expressed multiple HIV-1 genes, mutated to remove active sites of the HIV proteins. The vaccines were well tolerated, and a significant enhancement of DNA-vaccine primed HIV-1 specific T lymphocyte responses was observed following rFPV boosting. Co-expression of IFNgamma or IL-12 by the rFPV vaccines did not further enhance immune responses. Non-sterilising protection from a non-pathogenic HIV-1 challenge was observed. This study provides evidence of a safe, optimised, strategy for the generation of T-cell mediated immunity to HIV-1.

The factors influencing lymphocyte trafficking to the liver lobule during chronic hepaititis C virus (HCV) infection are currently not well defined. Interferon-γ-inducible protein 10 (IP-10), a chemokine that recruits activated T lymphocytes, has recently been shown by in situ hybridization to be expressed in the liver during chronic HCV infection. This study sought to define the cellular source of IP-10 in the liver by immunohistochemistry, to examine the expression of its receptor, CXCR3, on T lymphocytes isolated from blood and liver tissue, and to correlate IP-10 expression with the histological markers of inflammation and fibrosis. IP-10 was expressed by hepatocytes but not by other cell types within the liver, and the most intense immunoreactivity was evident in the areas of lobular inflammation. The IP-10 receptor was expressed on a significantly higher proportion of T lymphocytes in the liver compared with blood. CD8 T lymphocytes, which predominate in the liver lobule, were almost uniformly CXCR3-positive. The expression of IP-10 mRNA correlated with lobular necroinflammatory activity but not with inflammation or fibrosis in the portal tracts. These findings suggest that IP-10 may be induced by HCV within hepatocytes and may be important in the pathogenesis of chronic HCV infection, as recruitment of inflammatory cells into the lobule is an important predictor of disease progression.

A synthetic hydrophobic peptide (core peptide; CP) containing two positively charged amino acids, lysine and arginine was derived from the transmembrane sequence of the T-cell receptor (TCR) alpha chain and has been shown to inhibit T-cell-mediated inflammation. In this study, we investigated the specificity of CP (10 microm) on lymphocyte function and found that it significantly inhibited interleukin-2 production in T cells and natural killer cytotoxicity by 46-58% compared to positive control. CP had no effects on B-cell proliferative responses when used at these concentrations; however, it suppressed B-cell proliferation at higher concentrations (50 microm). Inhibition by CP was not the result of membrane pore formation or cytotoxicity when examined by trypan blue, propidium iodide staining or transmission electron microscopy. CP analogues, with both lysine and arginine replaced by neutral or negatively charged amino acids, or by randomly distributing charges in the peptide sequence, had no effect on lymphocyte function. These results suggest that peptide inhibition is affected by its structure and charge interactions, and may involve common signalling molecules in T, B and natural killer cells. The potential of the immuno-inhibitory effects of CP as a novel anti-inflammatory peptide in therapy should be further explored.

A highly sensitive, non-probe-based, real-time quantitative reverse transcriptase PCR was developed for viral load measurements in both serum and liver samples from patients with hepatitis C virus (HCV) infection. With synthetic RNA, the linearity of the approach was conserved over a wide range of HCV copy numbers. There was a strong correlation between hepatic and serum viral load measurements ( r = 0.689, P = 0.004, n = 15), indicating that the level of viremia reflected the amount of virus present in the liver.

Summary Hepatitis C virus, a recently identified member of the family Flaviviridae, is an important cause of chronic viral hepatitis and cirrhosis. There are similarities in the nature of the immune response to this pathogen with immunity in other flavivirus and hepatotropic virus infections, such as hepatitis B. However, the high rate of viral persistence after primary hepatitis C infection, and the observation that neutralizing antibodies are not protective, would suggest that there are a number of important differences between hepatitis C, other flaviviruses, and hepatitis B. The phenomenon of quasispecies evolution and other viral factors have been proposed to contribute to immune evasion by hepatitis C virus. In the face of established persistent infection, virus-specific cytotoxic T lymphocytes may exert some control over viral replication. However, these same effectors may also be responsible for the progressive liver damage characteristic of chronic hepatitis C infection. The nature of protective immunity, including the role of innate immune responses early after hepatitis C exposure, remains to be defined.

IL-12 production is reduced in HIV infection, and recombinant human IL-12 (rhIL-12) augments in vitro HIV-specific proliferative responses in PBMC from HIV-seropositive individuals. To determine whether rhIL12 could also augment HIV-specific CTL responses we studied 41 HIV-seropositive individuals. Recombinant hIL-12 increased the detectable in vitro HIV-specific CD8 CTL activity of PBMC taken from HIV-seropositive individuals with CD4 counts500 cells/microl and from some individuals with lower CD4 counts. IL-12 increased cell recovery in cultures of PBMC from HIV-seropositive individuals with CD4 counts500 cells/microl and also increased the precursor CTL frequency. However, the increase in HIV-specific CTL activity was not due to IL-2 or IFN-gamma production or an increase in the number of cells with surface markers characteristic of CTL effector cells. This study demonstrates that rhIL-12 augments in vitro HIV-specific CTL activity and provides evidence to justify further investigation within clinical trials of this cytokine in HIV infection.

Compelling evidence now suggests that αβ CD8 cytotoxic T lymphocytes (CTL) have an important role in preventing human immunodeficiency virus (HIV) infection and/or slowing progression to AIDS. Here, we describe an HIV type 1 CTL polyepitope, or polytope, vaccine comprising seven contiguous minimal HLA A2-restricted CD8 CTL epitopes conjoined in a single artificial construct. Epitope-specific CTL lines derived from HIV-infected individuals were able to recognize every epitope within the construct, and HLA A2-transgenic mice immunized with a recombinant virus vaccine coding for the HIV polytope also generated CTL specific for different epitopes. Each epitope in the polytope construct was therefore processed and presented, illustrating the feasibility of the polytope approach for HIV vaccine design. By simultaneously inducing CTL specific for different epitopes, an HIV polytope vaccine might generate activity against multiple challenge isolates and/or preempt the formation of CTL escape mutants.

The specificity and function of two T-cell clones derived from A/Memphis/1/71 (H3) influenza virus (Mem 71)-immune BALB/c spleen cells have been compared. One clone, X-31 clone 1, was subtype specific, proliferating in response to influenza strains of the H3 subtype only. The other, Jap clone 3, cross-reacted in proliferation assays with heterologous subtypes of influenza A, but not type B. Both clones recognized the HA 1 chain of the hemagglutinin (HA) molecule and their proliferation in response to detergent-disrupted virus could be specifically inhibited by monoclonal antibodies to the HA. The T-cell clones were of the L3T4 + phenotype. Both recognized antigen in association with I-E d , as indicated by studies with H-2 recombinant strains of mice and by blocking with monoclonal anti-I-E antibody. In vivo , both clones elicited a delayedtype hypersensitivity (DTH) reaction when inoculated into mouse footpads together with virus, X-31 clone 1 again displaying subtype specificity and Jap clone 3 being cross-reactive. The clones were also able to provide factor-mediated help in vitro to virus-primed B cells in an anti-HA antibody response. The cross-reactive T-cell clone provided help not only for B cells primed with influenza A subtype H3 and responding to H3 virus in culture, but also for H2 virus-primed B cells making anti-H2 antibody.

Fifteen T-cell clones were derived from BALB/c or DBA/2 mice immunized with a synthetic peptide corresponding to the C-terminal 24 residues (residues 305 to 328) of the HA1 chain of H3 subtype influenza virus hemagglutinin. All of the clones proliferated when the peptide was presented in association with I-Ed. By using shorter homologs, it was shown that the T-cell response was focused predominantly on the region at the N-terminal end of the peptide encompassed by residues 306 to 319. Individual clones recognizing this region differed in their absolute requirements for residues at the extremities of the site and also in their patterns of efficiency of recognition of shorter homologs. One particular clone defined another site of T-cell recognition within residues 314 to 328. The response of the clones to peptide analogs identified certain residues within the sites that were critical for recognition, with the substitution Gln-311----Ser having a differential effect on clones responding to the N-terminal site. Only one of the clones responded well to influenza virus itself. This clone also required relatively low concentrations of the parent peptide for optimum stimulation and was suppressed by higher concentrations. The data demonstrate striking heterogeneity in the T-cell response even to a short synthetic peptide, with different T-cell clones recognizing slightly different but overlapping areas of the molecule.

Helper T cel lines specific for influenza virus were established by continuous culture of Mem 71-Bel (H3) virus-immune spleen cells in the presence of virus and antigen-presenting cells and their specificity assessed in proliferation experiments. A line stimulated in vitro with Mem 71-Bel virus was able to proliferate in response to viruses of the same, and also of different, type A haemagglutinin (HA) subtypes as the immunizing virus but not to a type B influenza virus. A component of this cross-reactivity was due to recognition of the HA molecule. Lines stimulated in vitro with purified disrupted H3 or H2 viruses showed a higher degree of cross-reactivity. Of nine clones isolated from these lines, seven were directed against the HA molecule and recognized the HA1 chain. The HA-specific T cell clones were either subtype-specific T cell clones were either subtype-specific, recognizing only viruses of the H3 subtype, or cross-reactive, also recognizing viruses of the H2 subtype of type A (but not type B). Subtype-specific and cross-reactive T cell clones were shown to function as helper T cells in vitro. In addition to collaborating with H3 virus-primed B cells responding to H3 virus in culture, the cross-reactive T cell clone could also provide help for H2 virus-primed B cells making anti-HA antibody in response to H2 virus.

A total of 14 I-Ad-restricted helper T-cell clones specific for the hemagglutinin (HA) molecule of influenza virus were isolated from spleens of BALB/c or (BALB/c X C57BL/10)F1 mice immunized with the H3 subtype influenza virus A/Memphis/71 (Mem 71) and from lymph nodes of BALB/c mice primed with purified HA. The specificity of these T-cell clones was assessed in proliferation assays by reactivity with naturally occurring strains of viruses that arose by antigenic drift and contain known amino acid sequence changes in HA and with a panel of monoclonal antibody (MAb)-selected mutants of Mem 71 with single amino acid substitutions in HA. The HA genes of those mutant viruses that failed to stimulate one or more of the T-cell clones were sequenced. The clones could be allocated to at least four groups, each group having a distinct pattern of reactivity with the panel of natural field strains. The epitopes recognized by the four groups of clones were found, by reactivity with MAb-selected mutants, to be in very close proximity to one another and probably overlapping. All of the distinct epitopes recognized by the T-cell clones were adversely affected by a single amino acid substitution, either at residue 60 or at residue 63 in the HA1 polypeptide chain, within the region known from antibody-binding studies as site E. Some, but not all, of the epitopes may be influenced by the addition of a carbohydrate side chain to the HA of a particular MAb-selected mutant and certain field strains containing an Asp----Asn substitution at residue 63. Site E is therefore a major site of H-2d helper T-cell recognition on the H3 HA.