Alloreactive T cells deficient of the short-chain fatty acid receptor GPR109A induce less graft-versus-host disease

The intestinal microbiota is essential for the fermentation of dietary fiber into short-chain fatty acids (SCFA) such as butyrate, acetate, and propionate. SCFAs can bind to the G-protein-coupled receptors GPR43 and GPR109A (HCAR2), with varying affinities to promote cellular effects in metabolism or changes in immune function. We explored the role of GPR109A as the main receptor for butyrate in mouse models of allogeneic hematopoietic cell transplantation (allo-HCT) and graft-versus-host disease (GVHD). Deletion of GPR109A in allo-HCT recipients did not affect GVHD, but transplantation of T cells from GPR109A knockout (KO) (Gpr109a-/-) mice into allo-HCT recipient mice significantly reduced GVHD morbidity and mortality compared with recipients of wild-type (WT) T cells. Recipients of Gpr109a-/- T cells exhibited less GVHD-associated target organ pathology and decreased proliferation and homing of alloreactive T cells to target tissues. Although Gpr109a-/- T cells did not exhibit immune deficits at a steady state, following allo-activation, Gpr109a-/- T cells underwent increased apoptosis and were impaired mitochondrial oxidative phosphorylation, which was reversible through antioxidant treatment with N-acetylcysteine (NAC). In conclusion, we found that GPR109A expression by allo-activated T cells is essential for metabolic homeostasis and expansion, which are necessary features to induce GVHD after allo-HCT.

Rate of emergence of cytomegalovirus (CMV) mutations in leukocytes of patients with acquired immunodeficiency syndrome who are receiving valganciclovir as induction and maintenance therapy for CMV retinitis

The emergence of mutations conferring ganciclovir resistance was evaluated in an open-label randomized clinical trial that compared oral valganciclovir with intravenous ganciclovir as induction therapy, followed by maintenance with valganciclovir, for newly diagnosed cytomegalovirus (CMV) retinitis in 148 patients with acquired immunodeficiency syndrome. The presence of CMV mutations was directly assessed in patient leukocytes by polymerase chain reaction, followed by restriction fragment-length polymorphism (RFLP) for detection of the most common UL97 mutations associated with ganciclovir resistance and by sequencing of the viral UL97 gene. The cumulative percentages of patients with UL97-mutant viruses at 3, 6, 12, and 18 months (based on the number of patients on treatment at each time point) was 2.2%, 6.5%, 12.8%, and 15.3%, respectively. Of the 20 relevant UL97 mutations found by sequencing in 14 patients, 14 (70%) were detected by RFLP analysis. The rate of emergence of ganciclovir-resistant viruses with use of oral valganciclovir is no greater than that reported with use of intravenous ganciclovir.

Lack of immortalizing activity of a human papillomavirus type 16 variant DNA with a mutation in the E2 gene isolated from normal human cervical keratinocytes

The oncogenic potential of a human papillomavirus type 16 (HPV16) variant cloned from normal human cervical keratinocytes has been tested in vitro using primary rodent epithelial cells and human cervical keratinocytes. The HPV16 variant was able to extend the lifespan of, but failed to immortalize, human keratinocytes. It could however cooperate with an activated ras oncogene to transform primary rodent cells. Radioimmunoprecipitation assays of the rodent cells showed that they expressed the E7 protein. DNA sequence analysis of the URR/E6/E7 and E5 regions of the HPV16 showed them to be fully functional, but a deletion in the viral E2 open reading frame was detected. This truncated E2 only weakly stimulated transcription of the viral regulatory region. Complementation assays using the HPV16 variant and a full-length E2 enabled the cloned variant to immortalize human cervical keratinocytes with wild-type efficiency. These results suggest that other viral gene products in addition to E6/E7 may play an important role in the in vitro immortalization of cervical keratinocytes in HPV16 and the development of cervical cancer.

Human papillomavirus 16 E7 protein is associated with the nuclear matrix

The cellular localization of the human papillomavirus (HPV)-16 E7 gene product in the cell lines CaSki and SiHa has been determined by both biochemical and immunocytochemical methods. These measurements show E7 to be localized in the cell nucleus, specifically with the nonchromatin nuclear structure or nuclear matrix. This localization of E7 required an unambiguous fractionation of the nuclear constituents. This was achieved by using a gentle sequential fractionation procedure to prepare the scaffold consisting of the nuclear matrix and intermediate filaments (NM-IF). Chromatin was cleaved with nuclease and the resulting nucleosomes eluted with 0.25 M ammonium sulfate. Immunostaining of cells after this extraction procedure with monoclonal antibodies (mAbs) to E7 revealed a fine grained, punctate nuclear fluorescence in CaSki and SiHa, which was absent in normal cervical keratinocytes and the HPV-negative cell line C33.1. Western blots of cell fractions with these mAbs showed that E7 was localized in the NM-IF fraction in SiHa and CaSki but was not detected in HPV-negative cells. A second protein of slightly higher mobility is identified by these antisera in HPV-16-containing cells. The data suggest that the previous inability to directly visualize E7 by immunocytology is due to the masking of epitopes by cellular components and not to low levels of protein.

Alterations in growth properties of human papilloma virus type 16 immortalised human cervical keratinocyte cell line correlate with amplification and overexpression of c-myc oncogene

Clinical and epidemiological data support a role for human papilloma virus (HPV) type 16 in the pathogenesis of cervical carcinoma. The W12 cell line contains HPV16 sequences, predominantly as a high copy number episome, and is immortalised in vitro, but non-tumourigenic. A morphologically distinct sub-line of the parental W12 cell line was isolated which displayed increased growth rate, increased capacity for self-renewal and increased resistance to differentiation in comparison with the parental W12 cell line. The structure and expression of the HPV16 sequences was virtually identical in the two cell lines. However, expression of the c-myc proto-oncogene was elevated in the morphologically distinct sub-line, and this was associated with amplification, but not rearrangement, of the c-myc locus. Karyotype analysis demonstrated that amplification of the c-myc locus was a result of duplication of the long arm of chromosome eight.