Association of Baseline Tumor-Specific Neoantigens and CD8+ T-Cell Infiltration With Immune-Related Adverse Events Secondary to Immune Checkpoint Inhibitors.

PURPOSE: Recent evidence has shown that higher tumor mutational burden strongly correlates with an increased risk of immune-related adverse events (irAEs). By using an integrated multiomics approach, we further studied the association between relevant tumor immune microenvironment (TIME) features and irAEs. METHODS: Leveraging the US Food and Drug Administration Adverse Event Reporting System, we extracted cases of suspected irAEs to calculate the reporting odds ratios (RORs) of irAEs for cancers treated with immune checkpoint inhibitors (ICIs). TIME features for 32 cancer types were calculated on the basis of the cancer genomic atlas cohorts and indirectly correlated with each cancer's ROR for irAEs. A separate ICI-treated cohort of non-small-cell lung cancer (NSCLC) was used to evaluate the correlation between tissue-based immune markers (CD8+, PD-1/L1+, FOXP3+, tumor-infiltrating lymphocytes [TILs]) and irAE occurrence. RESULTS: The analysis of 32 cancers and 33 TIME features demonstrated a significant association between irAE RORs and the median number of base insertions and deletions (INDEL), neoantigens (r = 0.72), single-nucleotide variant neoantigens (r = 0.67), and CD8+ T-cell fraction (r = 0.51). A bivariate model using the median number of INDEL neoantigens and CD8 T-cell fraction had the highest accuracy in predicting RORs (adjusted r2 = 0.52, P = .002). Immunoprofile assessment of 156 patients with NSCLC revealed a strong trend for higher baseline median CD8+ T cells within patients' tumors who experienced any grade irAEs. Using machine learning, an expanded ICI-treated NSCLC cohort (n = 378) further showed a treatment duration-independent association of an increased proportion of high TIL (>median) in patients with irAEs (59.7% v 44%, P = .005). This was confirmed by using the Fine-Gray competing risk approach, demonstrating higher baseline TIL density (>median) associated with a higher cumulative incidence of irAEs (P = .028). CONCLUSION: Our findings highlight a potential role for TIME features, specifically INDEL neoantigens and baseline-immune infiltration, in enabling optimal irAE risk stratification of patients.

Sequential Combination of a Strong Interferon Inducer Viral Vector With Low Doses of Nivolumab Plus Ipilimumab Could Provide Functional Cure in Chronic Hepatitis B Virus infections: Technical Report Proposing a New Modality.

Based on the recommendation of the International Coalition to Eliminate hepatitis B virus (ICE-HBV), we intend to mimic the spontaneous resolution of HBV infection to achieve a functional cure of chronic hepatitis B virus (HBV) infection. To this end, we propose sequential targeting of the innate and adaptive host immune responses. Long-term suppression of HBV replication and hepatitis B surface antigen (HbsAg) production will be achieved first by inducing a strong innate immune response. The clinically validated viral superinfection therapy (SIT) will be administered, which employs an attenuated, non-lytic, double-stranded RNA (dsRNA) infectious bursal disease virus (IBDV) that provides an exceptionally strong interferon (IFN) response. Then, the exhausted HBV-specific T cell function will be restored by blocking the cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) and programmed cell death protein 1 (PD-1) receptors with immune checkpoint inhibitors (ICIs). In order to minimize any risk of toxicity, off-label low doses of nivolumab (0.5 mg/kg) plus ipilimumab (0.3 mg/kg) will be administered, the safety and efficacy of which has already been demonstrated in 131 unselected stage IV cancer patients. We predict that this combination therapy will provide sustained off-treatment virological and clinical responses during a relatively short treatment period.

Tackling cancer cell dormancy: Insights from immune models, and transplantation.

Disseminated non-dividing (dormant) cancer cells as well as those in equilibrium with the immune response remain the major challenge for successful treatment of cancer. The equilibrium between disseminated dormant cancer cells and the immune system is reminiscent of states that can occur during infection or allogeneic tissue and cell transplantation. We discuss here the major competing models of how the immune system achieves a self nonself discrimination (pathogen/danger patterns, quorum, and coinhibition/tuning models), and suggest that taking advantage of a combination of the proposed mechanisms in each model may lead to increased efficacy in tackling cancer cell dormancy.

Complete Remission of Vocal Cord Cancer Treated With Low-Dose Ipilimumab Plus Nivolumab Combined With Interleukin-2 and Hyperthermia.

We present a 44-year-old male patient, exposed to tobacco smoke and alcohol, with a locally advanced, multiple recurrent squamous cell carcinoma (SCC) of the vocal cord who had undergone resection four times. The patient rejected the mutilating surgery or radiation therapy due to the expected severe lifelong consequences. Instead, the patient opted for complex immunotherapy combining low doses of checkpoint inhibitors ipilimumab-nivolumab (0.3 and 0.5 mg/kg, respectively) with fever-inducing interleukin-2 (IL-2) and hyperthermia, which induced complete remission (CR). Restaging with MRI and laryngoscopy demonstrated lasting remission ongoing now for two years. The fact that this patient is free of any cancer-related signs or symptoms raises the possibility of a long-lasting remission even after the fourth recurrence of a locally advanced squamous cell vocal cord cancer by the induction of therapeutic fever combined with a safe low-dose ipilimumab plus nivolumab therapy to endorse T-cell function.

Significant association between tumor mutational burden and immune-related adverse events during immune checkpoint inhibition therapies.

More than 2000 immuno-oncology agents are being tested or are in use as a result of the cancer immunotherapy revolution. Manipulation of co-inhibitory receptors has achieved tumor eradication in a minority of patients, but widespread immune-related adverse events (irAEs) compromised tolerance to healthy self-tissues in the majority. We have proposed that a major mechanism of irAEs is similar to a graft-versus-malignancy effect of graft-versus-host disease. To verify our hypothesis, we retrieved post-marketing data of adverse events from the U.S. Food and Drug Administration Adverse Event Reporting System. A significant positive correlation was revealed in 7677 patients between the reporting odds ratio of irAEs during immune checkpoint inhibitor therapy and the corresponding tumor mutational burden across 19 cancer types. These results can be interpreted to mean that the ICI drugs unleashed T cells against "altered-self," self, and tumors resulting in better overall survival.

Exploiting autoimmunity unleashed by low-dose immune checkpoint blockade to treat advanced cancer.

As a result of the cancer immunotherapy revolution, more than 2000 immuno-oncology agents are currently being tested or are in use to improve responses. Not unexpectedly, the 2018 Nobel Prize in Physiology or Medicine was awarded to James P. Allison and Tasuku Honjo for their development of cancer therapy by the blockade of co-inhibitory signals. Unfortunately, manipulation of the co-inhibitory receptors has also resulted in a safety issue: widespread iatrogenic immune-related adverse events (irAEs). Autoimmunity is emerging as the nemesis of immunotherapy. Originally, it was assumed that CTLA-4 blockade selectively targets T cells relevant to the antitumour immune response. However, an uncontrolled pan T cell activation was induced compromising tolerance to healthy self-tissues. The irAEs are very similar to that of a chronic graft-versus-host-disease (GVHD) reaction following allogeneic bone marrow transplantation (BMT). We hypothesized that ipilimumab induced a graft-versus-malignancy (GVM) effect, which eradicated metastatic melanoma in a minority of patients, but also involved an auto-GVHD reaction that resulted in widespread autoimmunity in the majority. Therefore, we argued for a profound theoretical point against the consensus of experts. The task is not to desperately put the genie back in the bottle by immune-suppressive treatments, but instead to harness the autoimmune forces. In this way, the same goal could be achieved by an antibody as by the adoptive transfer of alloreactive donor lymphocytes, but without severe GVHD. The proof-of-principle of a low-dose-combination immune checkpoint therapy, consisting only of approved drugs and treatments, was demonstrated in 111 stage IV cancer patients.

MiStImm: an agent-based simulation tool to study the self-nonself discrimination of the adaptive immune response.

BACKGROUND: There is an increasing need for complex computational models to perform in silico experiments as an adjunct to in vitro and in vivo experiments in immunology. We introduce Microscopic Stochastic Immune System Simulator (MiStImm), an agent-based simulation tool, that is designed to study the self-nonself discrimination of the adaptive immune system. MiStImm can simulate some components of the humoral adaptive immune response, including T cells, B cells, antibodies, danger signals, interleukins, self cells, foreign antigens, and the interactions among them. The simulation starts after conception and progresses step by step (in time) driven by random simulation events. We also have provided tools to visualize and analyze the output of the simulation program. RESULTS: As the first application of MiStImm, we simulated two different immune models, and then we compared performances of them in the mean of self-nonself discrimination. The first model is a so-called conventional immune model, and the second model is based on our earlier T-cell model, called "one-signal model", which is developed to resolve three important paradoxes of immunology. Our new T-cell model postulates that a dynamic steady state coupled system is formed through low-affinity complementary TCR-MHC interactions between T cells and host cells. The new model implies that a significant fraction of the naive polyclonal T cells is recruited into the first line of defense against an infection. Simulation experiments using MiStImm have shown that the computational realization of the new model shows real patterns. For example, the new model develops immune memory and it does not develop autoimmune reaction despite the hypothesized, enhanced TCR-MHC interaction between T cells and self cells. Simulations also demonstrated that our new model gives better results to overcome a critical primary infection answering the paradox "how can a tiny fraction of human genome effectively compete with a vastly larger pool of mutating pathogen DNA?" CONCLUSION: The outcomes of our in silico experiments, presented here, are supported by numerous clinical trial observations from the field of immunotherapy. We hope that our results will encourage investigations to make in vitro and in vivo experiments clarifying questions about self-nonself discrimination of the adaptive immune system. We also hope that MiStImm or some concept in it will be useful to other researchers who want to implement or compare other immune models.

Post-infection viral superinfection technology could treat HBV and HCV patients with unmet needs.

BACKGROUND: Viral hepatitis deaths from acute infection, cirrhosis, and liver cancer have risen from the tenth to the seventh leading cause of death worldwide between 1990 and 2013. Even in the oral direct acting antiviral (DAA) agent era there are still large numbers of patients with unmet needs. Medications approved for treatment of chronic hepatitis B virus (HBV) infection do not eradicate HBV often requiring treatment for life associated with risks of adverse reactions, drug resistance, nonadherence, and increased cost. Although DAAs increased virologic cure rates well over 90% in all hepatitis C virus (HCV) genotypes, HCV infection still cannot be cured in a small but significant minority of patients. While most of the medical issues of HCV treatment have been solved, the current costs of DAAs are prohibitive. RESULTS: The post-infection viral superinfection treatment (SIT) platform technology has been clinically proven to be safe and effective to resolve acute and persistent viral infections in 42 HBV and HCV patients (20 HBV, 22 HCV), and in 4 decompensated patients (2 HBV, 2 HCV). SIT employs a non-pathogenic avian double stranded RNA (dsRNA) virus, a potent activator of antiviral gene responses. Unexpectedly, SIT is active against unrelated DNA (HBV) and RNA (HCV) viruses. SIT does not require lifelong therapy, which is a major advantage considering present HBV treatments. The new viral drug candidate (R903/78) is homogeneously produced by reverse genetics in Vero cells. R903/78 has exceptional pH and temperature stability and also excellent long-term stability; therefore, it can be orally administered, stored and shipped without freezing. Since R903/78 is easy to stockpile, the post-infection SIT could also alleviate the logistic hurdles of surge capacity in vaccine production during viral pandemics. CONCLUSION: To help large number of HBV and HCV patients with unmet needs, broad-spectrum antiviral drugs effective against whole classes of viruses are urgently needed. The innovative SIT technological platform will be a great additional armament to conquer viral hepatitis, which is still a major cause of death and disability worldwide.

Complete Clinical Remission of Stage IV Triple-Negative Breast Cancer Lung Metastasis Administering Low-Dose Immune Checkpoint Blockade in Combination With Hyperthermia and Interleukin-2.

The prognosis of triple-negative breast cancer with metastases after chemotherapy remains dismal. We report the case of a 50-year-old female with first disease recurrence at the axillary lymph node and, later on, bilateral pulmonary metastases with severe shortness of breath. The patient received low-dose immune checkpoint blockade (concurrent nivolumab and ipilimumab) weekly over 3 weeks with regional hyperthermia 3 times a week, followed by systemic fever-range hyperthermia induced by interleukin-2 for 5 days. She went into complete remission of her pulmonary metastases with transient WHO I-II diarrhea and skin rash. The patient remained alive for 27 months after the start of treatment, with recurrence of metastases as a sternal mass, and up to 3 cm pleural metastases. This exceptional response should instigate further research efforts with this protocol, which consists only of approved drugs and treatments.

Anti-CTLA-4 therapy may have mechanisms similar to those occurring in inherited human CTLA4 haploinsufficiency.

The inhibitory anti-CTLA-4 antibody, ipilimumab, dramatically improved survival in a subgroup of metastatic melanoma patients. The majority, however, suffered autoimmune-related adverse events (irAEs), sometimes pathognomonic of acute graft-versus-host-disease (GVHD). This implies that the CTLA-4 blockade is not tumor specific. We make a risky but testable prediction: anti-CTLA-4 therapy may have mechanism similar to that occurring in inherited human CTLA-4 haploinsufficiency. If so, a therapeutic paradigm shift is required. The task is not desperately trying to put the genie back in the bottle by immune-suppressive treatments, but harnessing the immense forces liberated by the anti-CTLA-4 antibody blockade by pretargeting or dose adjustment.

Control of minimal residual cancer by low dose ipilimumab activating autologous anti-tumor immunity.

In this perspective article, we address the controversy regarding the safety-efficacy issue in ipilimumab trials. While the CTLA-4 blockade interrupted T-cell pathways responsible for immune down-regulation and mediated regression of established malignant tumors in a minority of patients, this has to be weighed against the immune related adverse events (irAEs) suffered by the majority. Based on two groundbreaking but neglected proof-of-principle papers that demonstrated augmented graft-vs.-malignancy (GVM) effect that reversed the relapse of malignancy without worsening the graft-vs.-host disease (GVHD) by a CTLA-4 blockade, here we suggest a therapeutic paradigm shift, which may help break the impasse and resolve this timely issue in oncology.

A novel method of CD34+ cell separation from umbilical cord blood.

BACKGROUND: Umbilical cord blood (UCB) is rich in the heavily glycosylated CD34 antigen-bearing hematopoietic stem cells that are valuable for transplantation therapy of malignant and nonmalignant disease. CD34+ cell yields (0.13%-0.25%-0.3%) of mononuclear cells (UCMCs) isolated by anti-CD34 monoclonal antibody (MoAb) on immunomagnetic particles (e.g., Miltenyi particles) are insufficient to treat adults. STUDY DESIGN AND METHODS: We fractionated UCMCs by physicochemical charge-based methods. Avoiding Miltenyi particles and HESPAN yielded 30 x 10(6) to 54 x 10(6) UCMCs/20 mL UCB by Ficoll-Isopaque for serial depletion fractionation, using nylon wool column (NWC) or direct rosetting with sheep red blood cells (SRBCs) without incubation in the cold. RESULTS: CD34+ cell yields (approx. 5.12%) were 39 times greater than 0.13% (Korean study, 11,098 UCB units) and 10 to 20 times greater than 0.25% to 0.3% harvested by anti-CD34 Miltenyi particles. SRBC depletion of most high-specific-gravity T cells achieved considerable enrichment of CD34+ and BY55+ cells. Using NWC achieved 2.5-fold enrichment of CD34+ cells and twofold enrichment of BY55+ cells. Direct SRBC rosetting provided better or higher enrichment of CD34+ cells. Overall CD34+ cell yield in low-density fraction was more than twice after direct rosetting (38% vs. 16%) in contrast to separation by NWC followed by SRBC rosetting. CD3+ cell yields (by three CD markers) were approximately 8.83%, far below approximately 30 x 10(7) /kg considered acceptable to avoid graft-versus-host disease. Natural killer cell yields (CD16+/CD56+ and BY55+/ CD160+) are in perfect agreement. CONCLUSIONS: Achieving approximately 5% CD34+ cell yields from single UCB donations, a major advance, holds great promise for CD34+ cell therapy of adults and larger children, and cheaper cultured RBC manufacture.

Interesting possibilities to improve the safety and efficacy of ipilimumab (Yervoy).

As predicted, an anti-CTLA-4 mAb (ipilimumab) on binding to T lymphocytes breaks down immune-tolerance. Thereby, it was hoped, tumor-specific-T cells would be freed for a sustained attack on cancer cells. Data on ipilimumab treatment in 1498 patients with advanced melanoma (in 14 phase I-III trials) has shown immune-related adverse events (irAEs) in 64.2% of the patients consistent with tolerance breakdown. However, there is no evidence that the antitumor effects via a CTLA-4 blockade are attributable to T cells specifically targeting tumor cells. In fact, several trials indicate a possible correlation between grade 3 and 4 irAEs with clinical efficacy of ipilimumab; tumor regression may be associated with autoimmunity development. Therefore, we suggest a new treatment paradigm. The non-tumor specific pan-lymphocytic activation should be exploited by a 'pretargeting' approach proven successful in radioimmunodetection and radioimmunotherapy. First, an anti-tumor mAb conjugated with streptavidin (StAv) should be administered to be followed by the delivery of biotin-labeled anti-CTLA-4 mAb. This schedule has the virtue of endowing T cells with the ability to travel to tumor sites without prematurely succumbing to apoptosis, while streptavidin's ultra-high affinity for biotin (K(D), 10⁻¹5 M) ensures capturing all T cells binding biotin labeled anti-CTLA-4. Using the law of mass action, we calculated that following administration of ipilimumab at >1 mg/L concentration (∼5 mg per patient ∼70 kgbw), the immense forces of the immune system liberated by the anti-CTLA-4 antibody blockade would then be focused with laser sharp accuracy on tumor cells without collateral damage to normal host cells.

Ipilimumab (Yervoy) and the TGN1412 catastrophe.

The development of the anti-CTLA-4 antibody (ipilimumab; marketed as Yervoy) immune regulatory therapy was based on the premise that "Abrogation of the function of CTLA-4 would permit CD28 to function unopposed and might swing the balance in favor of immune stimulation, tolerance breakdown and tumor eradication…" (Weber, 2009). By now, the vast majority of data collected from more than 4000 patients proves that this prediction was entirely correct. Paradoxically, the successful blockade of immune checkpoints raises the question whether an anti-CTLA-4 antibody could ever become an important therapy against cancer. T cells lost their ability to discriminate between self and non-self. Thus, tolerance to self tissues was broken in ∼70% of the patients. In the recent industry-sponsored phase III clinical trial of ipilimumab, 147 (38.7%) of the patients experienced severe adverse events and 6.8% suffered dose-limiting events (8.4%, in the ipilimumab-alone group). There were 14 deaths related to the study drugs and 7 of these were associated with immune-related adverse events. In contrast, the complete response rate was only 0.2%, in one patient out of 403 who received ipilimumab plus a peptide vaccine. Promoters of ipilimumab appear to be unmindful of the clinical trial catastrophe in London. Then, a humanized "superagonist" anti-CD28 monoclonal antibody, TGN1412, which "preferentially" activated regulatory T cells, at a higher dose, also activated all CD28 positive T cells. This precipitated a "cytokine storm" leading to life-threatening multiple organ failure in the six healthy human volunteers. Neither anti-CD28 nor anti-CTLA-4 therapies rely on antigen-specificity. Both release free antibody into the body against common molecular targets that are expressed on the targeted as well as on the non-targeted T cells. At lower antibody doses specific T cells are preferentially activated. With increasing antibody dose, however, the kinetics of the interaction is pushed in favor of widespread non-specific T cell expansion. Using the law of mass action we calculated that the vast majority of the CTLA-4 receptors on all activated T cells (including melanoma specific T cells) in the phase III clinical trial of ipilimumab will have been saturated. This would explain the runaway immune response observed. The conclusions drawn by the authors of the ipilimumab trial paper could bear an independent inspection and reassessment concerning the validation of the blockade of immune checkpoints as an important therapeutic strategy against cancer.

Breast and other cancer dormancy as a therapeutic endpoint: speculative recombinant T cell receptor ligand (RTL) adjuvant therapy worth considering?

BACKGROUND: Most individuals who died of trauma were found to harbour microscopic primary cancers at autopsies. Surgical excision of the primary tumour, unfortunately, seems to disturb tumour dormancy in over half of all metastatic relapses. PRESENTATION OF THE HYPOTHESIS: A recently developed immune model suggested that the evolutionary pressure driving the creation of a T cell receptor repertoire was primarily the homeostatic surveillance of the genome. The model is based on the homeostatic role of T cells, suggesting that molecular complementarity between the positively selected T cell receptors and the self peptide-presenting major histocompatibility complex molecules establishes and regulates homeostasis, strictly limiting variations of its components. The repertoire is maintained by continuous peripheral stimulation via soluble forms of self-peptide-presenting major histocompatibility complex molecules governed by the law of mass action. The model states that foreign peptides inhibit the complementary interactions between the major histocompatibility complexes and T cell receptors. Since the vast majority of clinically detected cancers present self-peptides the model assumes that tumour cells are, paradoxically, under homeostatic T cell control.The novelty of our hypothesis therefore is that resection of the primary tumour mass is perceived as loss of 'normal' tissue cells. Consequently, T cells striving to reconstitute homeostasis stimulate rather than inhibit the growth of dormant tumour cells and avascular micrometastases. Here we suggest that such kick-start growths could be prevented by a recombinant T cell receptor ligand therapy that modifies T cell behaviour through a partial activation mechanism. TESTING THE HYPOTHESIS: The homeostatic T cell regulation of tumours can be tested in a tri-transgenic mice model engineered to express potent oncogenes in a doxycycline-dependent manner. We suggest seeding dissociated, untransformed mammary cells from doxycycline naïve mice into the lungs of two mice groups: one carries mammary tumours, the other does not. Both recipient groups to be fed doxycycline in order to activate the oncogenes of the untransformed mammary cells in the lungs, where solitary nodules are expected to develop 6 weeks after injection. We expect that lung metastasis development will be stimulated following resection of the primary tumour mass compared to the tumour-free mice. A recombinant T cell receptor ligand therapy, starting at least one day before resection and continuing during the entire experimental period, would be able to prevent the stimulating effect of surgery. IMPLICATIONS OF THE HYPOTHESIS: Recombinant T cell receptor ligand therapy of diagnosed cancer would keep all metastatic deposits microscopic for as long as the therapy is continued without limit and could be pursued as one method of cancer control. Improving the outcome of therapy by preventing the development of metastases is perhaps achievable more readily than curing patients with overt metastases.

Reduction in high blood tumor necrosis factor-alpha levels after manipulative therapy in 2 cervicogenic headache patients.

OBJECTIVE: This case report discusses the treatment of 2 patients with cervicogenic headache (CHA) attending the Outpatient Clinic of the Hungarian National Institute for Rheumatology and Physiotherapy (Budapest, Hungary) and reviews the pathophysiology, therapeutic strategy, and problems associated with the treatment of CHA. CLINICAL FEATURES: Patient 1 was a 27-year-old female who sustained a whiplash injury. A sharp, shooting headache developed, readily induced, and aggravated by just bending the neck backward or by turning her head. Magnetic resonance imaging revealed a disk protrusion at C4-C5 pressing the anterior cerebrospinal space. Patient 2 was a 62-year-old female who sustained a whiplash injury; her cervical movements became restricted, which precipitated headaches. Magnetic resonance imaging revealed a paramedian disk hernia between the C4 and C5 vertebrae that intruded into the right ventral cerebrospinal space. INTERVENTION AND OUTCOME: After 4 weeks of manipulative therapy for patient 1, both active and passive range of motion returned to normal, and the high tumor necrosis factor-alpha (TNF-alpha) level (63 pg/mL) was substantially reduced (28 pg/mL). Patient 2 was started on manipulative therapy twice a week for 4 weeks; after 2 months, the patient became symptom-free, and high TNF-alpha level (72 pg/mL) was reduced greatly (35 pg/mL). CONCLUSION: Two patients with whiplash injury and disk herniation developed CHA associated with very high TNF-alpha levels. After manipulative therapy, these patients became symptom-free, and their TNF-alpha levels decreased substantially.

T cells survey the stability of the self: a testable hypothesis on the homeostatic role of TCR-MHC interactions.

In the lifetime of an individual, every single gene will have undergone mutation on about 10(10) separate occasions. Nevertheless, cancer occurs mainly with advancing age. Here, we hypothesize that the evolutionary pressure driving the creation of the T cell receptor (TCR) repertoire was primarily the homeostatic surveillance of the genome. The subtly variable T cells may in fact constitute an evolutionary link between the invariable innate and hypervariable B cell systems. The new model is based on the homeostatic role of T cells, suggesting that molecular complementarity between the positively selected TCR and the self peptide-presenting major histocompatibility complex molecules establishes and regulates homeostasis, strictly limiting variations of its components. Notwithstanding, the 'homeostatic role of T cells' model offers a more realistic explanation as to how a naïve clonal immune system can cope with the much faster replicating pathogens, despite a limited repertoire that is capable of facing only a small fraction of the vast antigenic universe at a time.

Examination of the value of treatment of decompensated viral hepatitis patients by intentionally coinfecting them with an apathogenic IBDV and using the lessons learnt to seriously consider treating patients infected with HIV using the apathogenic hepatitis G virus.

Hepatitis virus infection persistent worldwide (approximately 600 m people) results in chronic hepatitis progressing to hepatocellular carcinoma (HCC) in many (approximately 1 m deaths/year). The review examines the usefulness of treating chronic viral hepatitis, including decompensated patients, by intentional coinfection with an attenuated infectious bursal disease virus (IBDV; apathogenic in man, stable at pH 2, orally administered). Learning lessons from the IBDV studies, the case is made to treat human immunodeficiency virus (HIV) infected patients (worldwide prevalence approximately 50 m people) by coinfecting with apathogenic hepatitis G virus (GBV-C). These ideas are reinforced by (i) eight out of ten studies reporting a beneficial effect of GBV-C viremia on HIV-related mortality or response to therapy and (ii) the recent reports of improved or delayed survival of HIV patients, naturally coinfected with an apathogenic virus.