One of the limitations for clinical applications of dendritic cell (DC)-based cancer immunotherapy is the low potency in generating tumor antigen specific T cell responses. We examined the immunotherapeutic potential of a mitochondria-targeted nanoparticle (NP) based on a biodegradable polymer and zinc phthalocyanine (ZnPc) photosensitizer (T-ZnPc-NPs). Here, we report that tumor antigens generated from treatment of breast cancer cells with T-ZnPc-NPs upon light stimulation activate DCs to produce high levels of interferon-gamma, an important cytokine considered as a product of T and natural killer cells. The remarkable ex vivo DC stimulation ability of this tumor cell supernatant is a result of an interleukin (IL)-12/IL-18 autocrine effect. These findings contribute to the understanding of how in situ light activation amplifies the host immune responses when NPs deliver the photosensitizer to the mitochondria and open up the possibility of using mitochondria-targeted-NP-treated, light-activated cancer cell supernatants as possible vaccines.

About 10% of the coding capacity of the Mycobacterium tuberculosis (M. tb) genome is devoted to the PE/PPE family of genes scattered throughout the genome. We have identified 28 PE/PPE operons which are organized within the M. tb genome in such a way that most PE members are upstream to PPE members. One example of such a gene arrangement is the PPE gene Rv2430c, earlier shown by us to code for a highly antigenic protein eliciting strong B-cell responses in TB patients [Choudhary, R.K., Mukhopadhyay, S., Chakhaiyar, P., Sharma, N., Murthy, K.J.R., Katoch V.M. and Hasnain, S.E. (2003) PPE antigen Rv2430c of Mycobacterium tuberculosis induces a strong B cell response. Infect. Immun. 71, 6338-6343], situated downstream to PE gene Rv2431c. Rv2431c and Rv2430c are transcribed as an operon. Expression of either rRv2431c or rRv2430c alone in E. coli limited their localization to the inclusion bodies. However, when they were co-expressed, both the proteins appeared in the soluble fraction. These two proteins interact with each other and form oligomers when alone, however, when present together they exist as heteromer.

BackgroundMany of the PE/PPE proteins are either surface localized or secreted outside and are thought to be a source of antigenic variation in the host. The exact role of these proteins are still elusive. We previously reported that the PPE41 protein induces high B cell response in TB patients. The PE/PPE genes are not randomly distributed in the genome but are organized as operons and the operon containing PE25 and PPE41 genes co-transcribe and their products interact with each other.Methodology/Principal FindingWe now describe the antigenic properties of the PE25, PPE41 and PE25/PPE41 protein complex coded by a single operon. The PPE41 and PE25/PPE41 protein complex induces significant (p<0.0001) B cell response in sera derived from TB patients and in mouse model as compared to the PE25 protein. Further, mice immunized with the PE25/PPE41 complex and PPE41 proteins showed significant (p<0.00001) proliferation of splenocyte as compared to the mice immunized with the PE25 protein and saline. Flow cytometric analysis showed 15–22% enhancement of CD8+ and CD4+ T cell populations when immunized with the PPE41 or PE25/PPE41 complex as compared to a marginal increase (8–10%) in the mice immunized with the PE25 protein. The PPE41 and PE25/PPE41 complex can also induce higher levels of IFN-γ, TNF-α and IL-2 cytokines.ConclusionWhile this study documents the differential immunological response to the complex of PE and PPE vis-à-vis the individual proteins, it also highlights their potential as a candidate vaccine against tuberculosis.

The cellular and molecular mechanisms underpinning the unusually high virulence of highly pathogenic avian influenza H5N1 viruses in mammalian species remains unknown. Here, we investigated if the cell tropism of H5N1 virus is a determinant of enhanced virulence in mammalian species. We engineered H5N1 viruses with restricted cell tropism through the exploitation of cell type-specific microRNA expression by incorporating microRNA target sites into the viral genome. Restriction of H5N1 replication in endothelial cells via miR-126 ameliorated disease symptoms, prevented systemic viral spread and limited mortality, despite showing similar levels of peak viral replication in the lungs as compared to control virus-infected mice. Similarly, restriction of H5N1 replication in endothelial cells resulted in ameliorated disease symptoms and decreased viral spread in ferrets. Our studies demonstrate that H5N1 infection of endothelial cells results in excessive production of cytokines and reduces endothelial barrier integrity in the lungs, which culminates in vascular leakage and viral pneumonia. Importantly, our studies suggest a need for a combinational therapy that targets viral components, suppresses host immune responses, and improves endothelial barrier integrity for the treatment of highly pathogenic H5N1 virus infections.