Dipeptidylpeptidase 4 inhibition enhances lymphocyte trafficking, improving both naturally occurring tumor immunity and immunotherapy.

The success of antitumor immune responses depends on the infiltration of solid tumors by effector T cells, a process guided by chemokines. Here we show that in vivo post-translational processing of chemokines by dipeptidylpeptidase 4 (DPP4, also known as CD26) limits lymphocyte migration to sites of inflammation and tumors. Inhibition of DPP4 enzymatic activity enhanced tumor rejection by preserving biologically active CXCL10 and increasing trafficking into the tumor by lymphocytes expressing the counter-receptor CXCR3. Furthermore, DPP4 inhibition improved adjuvant-based immunotherapy, adoptive T cell transfer and checkpoint blockade. These findings provide direct in vivo evidence for control of lymphocyte trafficking via CXCL10 cleavage and support the use of DPP4 inhibitors for stabilizing biologically active forms of chemokines as a strategy to enhance tumor immunotherapy.

Apolipoprotein H expression is associated with IL28B genotype and viral clearance in hepatitis C virus infection.

BACKGROUND & AIMS: HCV requires host lipid metabolism for replication, and apolipoproteins have been implicated in the response to treatment. METHODS: We examined plasma apolipoprotein concentrations in three cohorts of patients: mono-infected patients with symptomatic acute hepatitis C (aHCV); those undergoing treatment for chronic hepatitis C (cHCV); and HIV/HCV co-infected patients being treated for their chronic hepatitis C. We also evaluated associations between apolipoproteins and IL28B polymorphisms, a defined genetic determinant of viral clearance. RESULTS: Plasma apolipoprotein H (ApoH) levels were significantly higher in patients who achieved spontaneous clearance or responded to pegylated-interferon/ribavirin therapy. Strikingly, patients carrying the IL28B rs12979860 CC SNP correlated with the plasma concentration of ApoH in all three cohorts. Both ApoH and IL28B CC SNP were associated with HCV clearance in univariate analysis. Additional multivariate analysis revealed that the association between IL28B and HCV clearance was closely linked to that of Apo H and HCV clearance, suggesting that both belong to the same biological pathway to clearance. The association between IL28B CC SNP and ApoH was not observed in healthy individuals, suggesting that early post-infection events trigger differential ApoH expression in an IL28B allele dependent manner. CONCLUSIONS: This relationship identifies ApoH as the first induced protein quantitative trait associated with IL28B, and characterises a novel host factor implicated in HCV clearance.

Cutting edge: independent roles for IRF-3 and IRF-7 in hematopoietic and nonhematopoietic cells during host response to Chikungunya infection.

The host response to Chikungunya virus is dependent on the direct action of type I IFN on infected nonhematopoietic cells. Prior studies have demonstrated that multiple host sensors coordinate an antiviral response; however, the tissue source(s) and signaling pathways for IFN production remain unknown. In this study, we demonstrate that IRF-3 and IRF-7 are functionally redundant, but lack of both factors results in lethal infection in adult mice. Reciprocal bone marrow chimeras indicated that IRF-3 or IRF-7 expression in either hematopoietic or nonhemotopoietic cell compartments was capable of inducing an antiviral response. Interestingly, redundancy of IRF-3 and IRF-7 was age dependent, as neonatal animals lacking either factor succumbed to infection. We further demonstrate that IPS-1 is essential in nonhematopoietic cells and preferentially required during early life. These results highlight the interplay between nonimmune and immune cells during Chikungunya virus infection and suggest an important role for nonhematopoietic cells as a critical source of IFN-α/ß.

Identification of a novel neuropathogenic Theiler's murine encephalomyelitis virus.

Theiler's murine encephalitis viruses (TMEV) are divided into two subgroups based on their neurovirulence. Persistent strains resemble Theiler's original viruses (referred to as the TO subgroup), which largely induce a subclinical polioencephalomyelitis during the acute phase of the disease and can persist in the spinal cord of susceptible animals, inducing a chronic demyelinating disease. In contrast, members of the neurovirulent subgroup cause an acute encephalitis characterized by the rapid onset of paralysis and death within days following intracranial inoculation. We report herein the characterization of a novel neurovirulent strain of TMEV, identified using pyrosequencing technology and referred to as NIHE. Complete coverage of the NIHE viral genome was obtained, and it shares <90% nucleotide sequence identity to known TMEV strains irrespective of subgroup, with the greatest sequence variability being observed in genes encoding the leader and capsid proteins. The histopathological analysis of infected brain and spinal cord demonstrate inflammatory lesions and neuronal necrosis during acute infection with no evidence of viral persistence or chronic disease. Intriguingly, genetic analysis indicates the putative expression of the L protein, considered a hallmark of strains within the persistent subgroup. Thus, the identification and characterization of a novel neurovirulent TMEV strain sharing features previously associated with both subgroups will lead to a deeper understanding of the evolution of TMEV strains and new insights into the determinants of neurovirulence.

Circulating plasmacytoid dendritic cells in acutely infected patients with hepatitis C virus genotype 4 are normal in number and phenotype.

The incidence of hepatitis C virus (HCV) genotype 4 infection in Egypt provides a unique opportunity to study the innate immune response to symptomatic acute HCV infection. We investigated whether plasmacytoid dendritic cells (pDCs) are activated as a result of HCV infection. We demonstrate that, even during symptomatic acute infection, circulating pDCs maintained a similar precursor frequency and resting phenotype, compared with pDCs in healthy individuals. Moreover, stimulation with a Toll-like receptor 9 agonist resulted in an intact inflammatory response. These data support the growing consensus that pDCs are not directly activated by HCV and therefore are viable targets for immunotherapy throughout HCV infection.

Importance of the V1/V2 loop region of simian-human immunodeficiency virus envelope glycoprotein gp120 in determining the strain specificity of the neutralizing antibody response.

Plasma samples from individuals infected with human immunodeficiency virus type 1 (HIV-1) are known to be highly strain specific in their ability to neutralize HIV-1 infectivity. Such plasma samples exhibit significant neutralizing activity against autologous HIV-1 isolates but typically exhibit little or no activity against heterologous strains, although some cross-neutralizing activity can develop late in infection. Monkeys infected with the simian-human immunodeficiency virus (SHIV) clone DH12 generated antibodies that neutralized SHIV DH12, but not SHIV KB9. Conversely, antibodies from monkeys infected with the SHIV clone KB9 neutralized SHIV KB9, but not SHIV DH12. To investigate the role of the variable loops of the HIV-1 envelope glycoprotein gp120 in determining this strain specificity, variable loops 1 and 2 (V1/V2), V3, or V4 were exchanged individually or in combination between SHIV DH12 and SHIV KB9. Despite the fact that both parental viruses exhibited significant infectivity and good replication in the cell lines examined, 3 of the 10 variable-loop chimeras exhibited such poor infectivity that they could not be used further for neutralization assays. These results indicate that a variable loop that is functional in the context of one particular envelope background will not necessarily function within another. The remaining seven replication-competent chimeras allowed unambiguous assignment of the sequences principally responsible for the strain specificity of the neutralizing activity present in SHIV-positive plasma. Exchange of the V1/V2 loop sequences conferred a dominant loss of sensitivity to neutralization by autologous plasma and a gain of sensitivity to neutralization by heterologous plasma. Substitution of V3 or V4 had little or no effect on the sensitivity to neutralization. These data demonstrate that the V1/V2 region of HIV-1 gp120 is principally responsible for the strain specificity of the neutralizing antibody response in monkeys infected with these prototypic SHIVs.

Infectivity and neutralization of simian immunodeficiency virus with FLAG epitope insertion in gp120 variable loops.

A FLAG epitope tag was substituted within variable loop 1 (V1), 2 (V2), or 4 (V4) of the gp120 envelope glycoprotein of simian immunodeficiency virus strain 239 (SIV239) to evaluate the extent to which each variable loop may serve as a target for antibody-mediated neutralization. Two sites within each variable loop of SIV239 were chosen for individual epitope tag insertions. FLAG epitope substitutions were also made in the V1, V2, and V4 loops of a neutralization-sensitive derivative of SIV239, SIV316. Of the 10 FLAG-tagged recombinant viruses analyzed, three (SIV239FV1b, SIV239FV2b, and SIV239FV4a) replicated with kinetics similar to those of the parental strain, SIV239, in both CEMx174 cells and the immortalized rhesus monkey T-cell line 221. The SIV316FV1b and SIV316FV4a FLAG variants replicated with a substantial lag, and the five remaining recombinants did not replicate detectably. Both gp160 and gp120 from replication-competent FLAG variants could be immunoprecipitated from transfected 293T cells by the anti-gp120 rhesus monoclonal antibody (RhMAb) 3.11H, the anti-FLAG MAb M2, and CD4-immunoglobulin, whereas only unprocessed gp160 was detected in 293T cells transfected with replication-defective variants. Furthermore, gp120 was detectably incorporated only into virions that were infectious. SIV239FV1b was sensitive to neutralization by MAb M2, with a 50% inhibitory concentration of 1 mug/ml. Neither SIV239FV2b nor SIV239FV4a was sensitive to M2 neutralization. The ability of the M2 antibody to neutralize SIV239FV1b infectivity was associated with an increased ability of the M2 antibody to detect native, oligomeric SIV239FV1b envelope protein on the surfaces of cells relative to that for the other SIV FLAG variants. Furthermore, SIV239FV1b was globally more sensitive to antibody-mediated neutralization than was parental SIV239 when these strains were screened with a panel of anti-SIV MAbs of various specificities. These results indicate that the V1 loop can serve as an effective target for neutralization on SIV239FV1b. However, antibody-mediated neutralization of this variant, similar to that of other SIV239 variants that have been studied previously, was associated with a global increase in neutralization sensitivity. These results suggest that the variable loops on the neutralization-resistant SIV239 strain are difficult for antibodies to access effectively and that mutations that allow neutralization have global effects on the trimeric envelope glycoprotein structure and accessibility.