Non-oncogenic Acute Viral Infections Disrupt Anti-cancer Responses and Lead to Accelerated Cancer-Specific Host Death

In light of increased cancer prevalence and cancer-specific deaths in patients with infections, we investigated whether infections alter anti-tumor immune responses. We report that acute influenza infection of the lung promotes distal melanoma growth in the dermis and leads to accelerated cancer-specific host death. Furthermore, we show that during influenza infection, anti-melanoma CD8⁺ T cells are shunted from the tumor to the infection site, where they express high levels of the inhibitory receptor programmed cell death protein 1 (PD-1). Immunotherapy to block PD-1 reverses this loss of anti-tumor CD8⁺ T cells from the tumor and decreases infection-induced tumor growth. Our findings show that acute non-oncogenic infection can promote cancer growth, raising concerns regarding acute viral illness sequelae. They also suggest an unexpected role for PD-1 blockade in cancer immunotherapy and provide insight into the immune response when faced with concomitant challenges.

NK cells and CD8+ T cells cooperate to improve therapeutic responses in melanoma treated with interleukin-2 (IL-2) and CTLA-4 blockade

BACKGROUND

Melanoma is one of the few types of cancer with an increasing annual incidence. While a number of immunotherapies for melanoma have been associated with significant clinical benefit, including high-dose IL-2 and cytotoxic T lymphocyte antigen 4 (CTLA-4) blockade, clinical response to either of these single agents has been limited to 11-20% of treated patients. Therefore, in this study, we sought to test the hypothesis that the combination of IL-2 and CTLA-4 blockade could mediate a more profound therapeutic response.

METHODS

Here, B6 mice were challenged with poorly immunogenic B16 melanoma on day 0, and treated with CTLA-4 blocking antibody (100 μg/mouse) on days 3, 6, and 9, and IL-2 (100,000 units) twice daily on days 4-8, or both.

RESULTS

A highly significant synergistic effect that delayed tumor growth and prolonged survival was demonstrated with the combination immunotherapy compared to either monotherapy alone. The therapeutic effect of combination immunotherapy was dependent on both CD8+ T and NK cells and co-depletion of these subsets (but not either one alone) abrogated the therapeutic effect. CTLA-4 blockade increased immune cell infiltration (including CD8+ T cells and NK cells) in the tumor and IL-2 reduced the proportion of highly differentiated/exhausted tumor-infiltrating NK cells.

CONCLUSIONS

These results have implications for the design of clinical trials in patients with metastatic melanoma and provide new insights into how the immune system may be mediating anti-tumor activity with combination IL-2 and CTLA-4 blockade in melanoma.

HIV infection accelerates gastrointestinal tumor outgrowth in NSG-HuPBL mice

HIV infection is a risk factor for the tumorigenesis including non-AIDS-defining cancers such as those of the gastrointestinal tract. However, the mechanisms underlying such cancer outgrowth are still unknown. Furthermore, combined HIV/cancer studies are difficult to evaluate using primate models or in the clinical patient setting. To understand the mechanisms of tumor outgrowth in the context of HIV infection, we adopted a humanized mouse model permissive to infection and cancer as well as an in vivo humanized mouse challenge with colon cancer in the context of HIV infection. Immunodeficient NOD SCID IL-2R(-/-) mice were immunologically reconstituted by adoptive transfer of 10(7) HIV-negative donor peripheral blood leukocytes and challenged with 10(6) HCT116 human colon cancer cells. A group of mice was treated with antiretroviral therapy. Tumor microenvironment and epithelial tissues in the context of HIV infection were analyzed using immunohistochemistry. We demonstrate that HIV-infected humanized mice develop significantly larger tumors than uninfected mice (p<0.05). Epithelial cell proliferation in HIV-infected mice is significantly enhanced in comparison to proliferation in uninfected mice (p<0.01). Moreover, the activation of β-catenin, an important step in intestinal epithelial cell proliferation and tumorigenesis, is elevated in the tumors of HIV-infected mice (p<0.0001). Importantly, antiretroviral therapy reverses these pathological processes independently of CD4(+) T cell return. These findings model the ability of HIV infection to result in tumor outgrowth that is evident in HIV-positive patients and lend insight into previously unrecognized mechanisms that may underlie this pathology.

Impact of non-oncogenic acute viral infection on anti-tumor CD8+ T cell responses (TUM5P.938)

Background: Factors dictating clinical emergence of cancer are not fully understood. Specifically, how non-oncogenic acute viral infections affect unrelated anti-tumor CD8+ T cell responses (those in uninfected tissues) is unknown. Methods: Therefore, we infected B6 mice with non-lethal Influenza (A/PR/8-OVA, 80,000 EID50, intranasally) 3 days prior to challenge with B16-F10 melanoma (120,000 cells, subcutaneously, right flank). To track self/tumor antigen, virus-expressing antigen, and unrelated foreign antigen CD8+ T cells, we transferred pmel (gp100-specific, Thy1.1+Ly5.1-), OT-I (OVA-specific, Thy1.1+Ly5.1+), and P14 (LCMV gp33, Thy1.1-Ly5.1-) CD8+ T cells, respectively, into Thy1.1-Ly5.1+ B6 mice. Results: Influenza infection significantly worsened normal host anti-tumor responses and decreased host survival with cancer from ~32 to ~15 days (P&lt;0.01). Interestingly, pmel (but not OT-I and P14) CD8+ T cells circulating to the infected lung underwent cell death resulting in their eventual loss from the tumor microenvironment (up to 90%; P&lt;0.001). Similar findings were observed with infections 15 or 30 days before or 7 days after B16 challenge and when Balb/c or humanized NSG mice were challenged with breast cancer or melanoma in the context of LCMV or HIV. Conclusions: Our findings may explain the clinical phenomenon emerging from epidemiologic studies reporting increased unrelated cancer in patients with non-oncogenic viral infections.

Antigenic peptide nanofibers elicit adjuvant-free CD8⁺ T cell responses

Vaccines that elicit robust CD8⁺ T cell responses are desirable for protection against infectious diseases and cancers. However, most vaccine adjuvants fail to elicit robust CD8⁺ T cell responses without inflammation and associated toxicity. We recently reported that self-assembling peptides that form nanofibers in physiological buffers elicited strong adjuvant-free and antigen-specific antibody responses in mice. However, whether or not such nanofibers likewise can elicit strong CD8⁺ T cell responses is unknown. Here, we demonstrate that the self-assembling peptide Q11 conjugated to a CD8⁺ T cell epitope of ovalbumin (Q11-OVA), elicits strong antigen-specific primary and recall responses, and in a vaccination regimen protects against subsequent infection. Importantly, we show that these antigenic peptide nanofibers do not persist as an inflammatory antigen depot at the injection site. Our results demonstrate for the first time that self-assembling peptides may be useful as carriers for vaccines where CD8⁺ T cell-mediated protection is needed.

Membrane-based plasma collection device for point-of-care diagnosis of HIV

A major requirement for the development of point-of-care tests for the detection of disease analytes is the need to separate plasma from whole blood in an efficient and rapid manner. Furthermore, the separated plasma must be able to elute efficiently the analyte of interest and serve effectively as a physical matrix to deliver the equivalent of neat plasma for downstream diagnostic analysis. Additionally, many applications require the use of heat shock to liberate immunocomplexed antigen found in the collected plasma. A membrane-based filter method is reported for rapid and efficient collection of plasma from a whole blood sample that is compatible with heat shock. Using pediatric human immunodeficiency virus as an example, this device elutes 100% of the input p24 core antigen post-collection and enables heat shock of plasma samples identical to neat plasma treatment.

Induction of CAF-1 expression in response to DNA strand breaks in quiescent human cells

Genome stability in eukaryotic cells is maintained through efficient DNA damage repair pathways, which have to access and utilize chromatin as their natural template. Here we investigate the role of chromatin assembly factor 1 (CAF-1) and its interacting protein, PCNA, in the response of quiescent human cells to DNA double-strand breaks (DSBs). The expression of CAF-1 and PCNA is dramatically induced in quiescent cells upon the generation of DSBs by the radiomimetic drug bleocin (a bleomycin compound) or by ionizing radiation. This induction depends on DNA-PK. CAF-1 and PCNA are recruited to damaged chromatin undergoing DNA repair of single- and double-strand DNA breaks by the base excision repair and nonhomologous end-joining pathways, respectively, in the absence of extensive DNA synthesis. CAF-1 prepared from repair-proficient quiescent cells after induction by bleocin mediates nucleosome assembly in vitro. Depletion of CAF-1 by RNA interference in bleocin-treated quiescent cells in vivo results in a significant loss of cell viability and an accumulation of DSBs. These results support a novel and essential role for CAF-1 in the response of quiescent human cells to DSBs, possibly by reassembling chromatin following repair of DNA strand breaks.

Silencing of chromatin assembly factor 1 in human cells leads to cell death and loss of chromatin assembly during DNA synthesis

In eukaryotic cells, chromatin serves as the physiological template for gene transcription, DNA replication, and repair. Chromatin assembly factor 1 (CAF-1) is the prime candidate protein to mediate assembly of newly replicated DNA into chromatin. To investigate the physiological role of CAF-1 in vivo, we used RNA interference (RNAi) to silence the 60-kDa subunit of CAF-1 (p60) in human cells. Transfection of a small interfering RNA (siRNA) directed against p60 resulted in efficient silencing of p60 expression within 24 h. This silencing led to an induction of programmed cell death in proliferating but not in quiescent human cells. Concomitantly, proliferating cells lacking p60 accumulated DNA double-strand breaks and increased levels of the phosphorylated histone H2A.X. Nuclear extracts from cells lacking p60 exhibited a 10-fold reduction of nucleosome assembly activity during DNA synthesis, which was restored upon addition of recombinant p60 protein. Nascent chromatin in cell nuclei lacking p60 showed significantly increased nuclease sensitivity, indicating chromatin assembly defects during DNA synthesis in vivo. Collectively, these data identify CAF-1 as an essential factor not only for S-phase-specific chromatin assembly but also for proliferating cell viability.

Temporal pattern recognition based on instantaneous spike rate coding in a simple auditory system

Auditory pattern recognition by the CNS is a fundamental process in acoustic communication. Because crickets communicate with stereotyped patterns of constant frequency syllables, they are established models to investigate the neuronal mechanisms of auditory pattern recognition. Here we provide evidence that for the neural processing of amplitude-modulated sounds, the instantaneous spike rate rather than the time-averaged neural activity is the appropriate coding principle by comparing both coding parameters in a thoracic interneuron (Omega neuron ON1) of the cricket (Gryllus bimaculatus) auditory system. When stimulated with different temporal sound patterns, the analysis of the instantaneous spike rate demonstrates that the neuron acts as a low-pass filter for syllable patterns. The instantaneous spike rate is low at high syllable rates, but prominent peaks in the instantaneous spike rate are generated as the syllable rate resembles that of the species-specific pattern. The occurrence and repetition rate of these peaks in the neuronal discharge are sufficient to explain temporal filtering in the cricket auditory pathway as they closely match the tuning of phonotactic behavior to different sound patterns. Thus temporal filtering or "pattern recognition" occurs at an early stage in the auditory pathway.