Dynamics of cellular immune responses in the acute phase of dengue virus infection.

In this study, we examined the dynamics of cellular immune responses in the acute phase of dengue virus (DENV) infection in a marmoset model. Here, we found that DENV infection in marmosets greatly induced responses of CD4/CD8 central memory T and NKT cells. Interestingly, the strength of the immune response was greater in animals infected with a dengue fever strain than in those infected with a dengue hemorrhagic fever strain of DENV. In contrast, when animals were re-challenged with the same DENV strain used for primary infection, the neutralizing antibody induced appeared to play a critical role in sterilizing inhibition against viral replication, resulting in strong but delayed responses of CD4/CD8 central memory T and NKT cells. The results in this study may help to better understand the dynamics of cellular and humoral immune responses in the control of DENV infection.

Assessing the Potential for Genome-Assisted Breeding in Red Perilla Using Quantitative Trait Locus Analysis and Genomic Prediction.

Red perilla is an important medicinal plant used in Kampo medicine. The development of elite varieties of this species is urgently required. Medicinal compounds are generally considered target traits in medicinal plant breeding; however, selection based on compound phenotypes (i.e., conventional selection) is expensive and time consuming. Here, we propose genomic selection (GS) and marker-assisted selection (MAS), which use marker information for selection, as suitable selection methods for medicinal plants, and we evaluate the effectiveness of these methods in perilla breeding. Three breeding populations generated from crosses between one red and three green perilla genotypes were used to elucidate the genetic mechanisms underlying the production of major medicinal compounds using quantitative trait locus analysis and evaluating the accuracy of genomic prediction (GP). We found that GP had a sufficiently high accuracy for all traits, confirming that GS is an effective method for perilla breeding. Moreover, the three populations showed varying degrees of segregation, suggesting that using these populations in breeding may simultaneously enhance multiple target traits. This study contributes to research on the genetic mechanisms of the major medicinal compounds of red perilla, as well as the breeding efficiency of this medicinal plant.

CD16(+) natural killer cells play a limited role against primary dengue virus infection in tamarins.

CD16 is a major molecule expressed on NK cells. To directly assess the role of natural killer (NK) cells in dengue virus (DENV) infection in vivo, CD16 antibody-treated tamarins were inoculated with a DENV-2 strain. This resulted in the transient depletion of CD16(+) NK cells, whereas no significant effects on the overall levels or kinetics of plasma viral loads and antiviral antibodies were observed in the treated monkeys when compared to control monkeys. It remains elusive whether the CD16(-) NK subpopulation could play an important role in the control of primary DENV infection.

Human immunodeficiency virus type 1 Vpr interacts with spliceosomal protein SAP145 to mediate cellular pre-mRNA splicing inhibition.

Vpr, an accessory gene product of human immunodeficiency virus type 1 (HIV-1), affects both viral and cellular proliferation by mediating long terminal repeat activation, cell cycle arrest at the G2 phase, and apoptosis. We previously found that Vpr plays a novel role as a regulator of pre-mRNA splicing both in vivo and in vitro. However, the cellular target of Vpr, as well as the mechanism of cellular pre-mRNA splicing inhibition by Vpr, is unknown. Here, we show clearly that Vpr inhibits the splicing of cellular pre-mRNA, such as beta-globin pre-mRNA and immunoglobulin (Ig) M pre-mRNA and that the third alpha-helical domain and arginine-rich region are important its ability to inhibit splicing. Additionally, using mutants with specific substitutions in two domains of Vpr, we demonstrated that the interaction between Vpr and SAP145, an essential splicing factor, was indispensable for splicing inhibition. Finally, co-immunoprecipitation and in vitro competitive binding assays indicated that Vpr associates with SAP145 and interferes with SAP145-SAP49 complex formation. Thus, these results suggest that cellular expression of Vpr may block spliceosome assembly by interfering with the function of the SAP145-SAP49 complex in host cells.

Human immunodeficiency virus type 1 Vpr induces cell cycle arrest at the G(1) phase and apoptosis via disruption of mitochondrial function in rodent cells.

Vpr of human immunodeficiency virus type 1 causes cell cycle arrest at the G(2)/M phase and induces apoptosis after G(2)/M arrest in primate cells. We have reported previously that Vpr also induces apoptosis independently of G(2)/M arrest in human HeLa cells. By contrast, Vpr does not induce G(2)/M arrest in rodent cells, but it retards cell growth. To clarify the relationship between cell cycle arrest and apoptosis, we expressed Vpr endogenously in rodent cells and investigated cell cycle profiles and apoptosis. We show here that Vpr induces cell cycle arrest at the G(1) phase and apoptosis in rodent cells. Vpr increased the activity of caspase-3 and caspase-9, but not of caspase-8. Moreover, Vpr-induced apoptosis could be inhibited by inhibitors of caspase-3 and caspase-9, but not by inhibitor of caspase-8. We also showed that Vpr induces the release of cytochrome c from mitochondria into the cytosol and disrupts the mitochondrial transmembrane potential. Finally, we showed that apoptosis occurred in HeLa cells through an identical pathway. These results suggest that disruption of mitochondrial functions by Vpr induces apoptosis via cell cycle arrest at G(1), but that apoptosis is independent of G(2)/M arrest. Furthermore, it appears that Vpr acts species-specifically with respect to induction of cell cycle arrest but not of apoptosis.

Characterization of natural killer cells in tamarins: a technical basis for studies of innate immunity.

Natural killer (NK) cells are capable of regulating viral infection without major histocompatibility complex restriction. Hepatitis C is caused by chronic infection with hepatitis C virus (HCV), and impaired activity of NK cells may contribute to the control of the disease progression, although the involvement of NK cells in vivo remains to be proven. GB virus B (GBV-B), which is genetically most closely related to HCV, induces acute and chronic hepatitis upon experimental infection of tamarins. This non-human primate model seems likely to be useful for unveiling the roles of NK cells in vivo. Here we characterized the biological phenotypes of NK cells in tamarins and found that depletion of the CD16+ subset in vivo by administration of a monoclonal antibody significantly reduced the number and activity of NK cells.