While antiretroviral therapy (ART) can suppress HIV replication, it is not a cure. It is therefore essential to develop therapeutic strategies to enhance the immune system to better become activated and recognize virus-infected cells.

Chlamydia are Gram negative bacterial pathogens responsible for disease in humans and economically important domesticated animals. As obligate intracellular bacteria, they must gain entry into a host cell where they propagate within a parasitophorous organelle that serves as an interactive interface between the bacterium and the host. Nutrient acquisition, growth, and evasion of host defense mechanisms occur from this location. In addition to these cellular and bacterial dynamics, Chlamydia differentiate between two morphologically distinct forms, the elementary body and reticulate body, that are optimized for either extracellular or intracellular survival, respectively. The mechanisms regulating and mediating these diverse physiological events remain largely unknown. Reversible phosphorylation, including classical two-component signaling systems, partner switching mechanisms, and the more recently appreciated bacterial Ser/Thr/Tyr kinases and phosphatases, has gained increasing attention for its role in regulating important physiological processes in bacteria including metabolism, development, and virulence. Phosphorylation modulates these events via rapid and reversible modification of protein substrates leading to changes in enzyme activity, protein oligomerization, cell signaling, and protein localization. The characterization of several conserved chlamydial protein kinases and phosphatases along with phosphoproteome analysis suggest that Chlamydia are capable of global and growth stage-specific protein phosphorylation. This mini review will highlight the current knowledge of protein phosphorylation in Chlamydia and its potential role in chlamydial physiology and, consequently, virulence. Comparisons with other minimal genome intracellular bacterial pathogens also will be addressed with the aim of illustrating the importance of this understudied regulatory mechanism on pathogenesis and the principle questions that remain unanswered.

Chlamydiae are obligate intracellular Gram-negative bacterial pathogens that undergo an essential, but poorly understood, biphasic developmental cycle transitioning between the infectious elementary body and the replicative reticulate body. Ser/Thr/Tyr phosphorylation has been increasingly recognized for its role in regulating bacterial physiology. spp. encode two Hanks'-type kinases in addition to a type 2C protein phosphatase (PP2C; CppA) and appears capable of global protein phosphorylation. While these findings substantiate the importance of protein phosphorylation in, the physiological impact of protein phosphorylation remains enigmatic. In this study, we investigated the role of CppA by using recombinant protein point mutants and small-molecule inhibitors. Recombinant CppA (rCppA) amino acid point mutants based upon missense mutations identified in growth-deficient strains exhibited reduced, but not a complete loss of, phosphatase activity toward -nitrophenyl phosphate (pNPP) and phosphopeptides. To more directly explore the importance of CppA in chlamydial development, we implemented a chemical "knockout" approach using derivatives of 5,5'-methylenedisalicylic acid (MDSA). Several MDSA derivatives significantly reduced CppA activity and the growth of L2, D, and in a cell culture infection model. The inhibition of L2 growth was more pronounced when treated at earlier infection time points, and the removal of the inhibitors after 12 h postinfection did not rescue progeny production. Our findings revealed that altered CppA activity reduces chlamydial growth and that CppA function is likely crucial for early differentiation events. Collectively, our findings further support the importance of the protein phosphorylation network in chlamydial development. is a significant cause of disease in humans, including sexually transmitted infections, the ocular infection trachoma, and pneumonia. Despite the critical roles of protein phosphatases in bacterial physiology, their function in pathogenesis is less clear. Our findings demonstrate that CppA, a broad-specificity type 2C protein phosphatase (PP2C), is critical for chlamydial development and further substantiate reversible phosphorylation as a key regulatory mechanism in Additionally, our work highlights the potential of CppA to serve as a novel target for future therapeutic strategies and supports the feasibility of designing more potent PP2C phosphatase inhibitors for and other pathogenic bacteria.

Allogeneic hematopoietic stem cell transplants can lead to dramatic reductions in human immunodeficiency virus (HIV) reservoirs. This effect is partially mediated by donor T cells recognizing lymphocyte-expressed minor histocompatibility antigens (mHAgs). The potential to mark malignant and latently infected cells for destruction makes mHAgs attractive targets for cellular immunotherapies. However, testing such HIV reservoir reduction strategies will likely require preclinical studies in non-human primates (NHPs). In this study, we used a combination of alloimmunization, whole exome sequencing, and bioinformatics to identify an mHAg in Mauritian cynomolgus macaques (MCMs). We mapped the minimal optimal epitope to a 10-mer peptide (SW10) in apolipoprotein B mRNA editing enzyme catalytic polypeptide-like 3C (APOBEC3C) and determined the major histocompatibility complex class I restriction element as Mafa-A1 * 063, which is expressed in almost 90% of MCMs. APOBEC3C SW10-specific CD8 + T cells recognized immortalized B cells but not fibroblasts from an mHAg-positive MCM. These results provide a framework for identifying mHAgs in a non-transplant setting and suggest that APOBEC3C SW10 could be used as a model antigen to test mHAg-targeted therapies in NHPs.

Vaccine strategies aimed at eliciting HIV-specific CD8+ T cells are one major target of interest in HIV functional cure strategies. We hypothesized that CD8+ T cells elicited by therapeutic vaccination during antiretroviral therapy (ART) would be recalled and boosted by treatment with the IL-15 superagonist N-803 after ART discontinuation. We intravenously immunized four SIV+ Mauritian cynomolgus macaques (MCM) receiving ART with vesicular stomatitis virus (VSV), modified vaccinia virus Ankara strain (MVA), and recombinant adenovirus serotype 5 (rAd-5) vectors all expressing SIVmac239 Gag. Immediately after ART cessation, these animals received three doses of N-803. Four control animals received no vaccines or N-803. The vaccine regimen generated a high magnitude of Gag-specific CD8+ T cells that were proliferative and biased toward an effector memory phenotype. We then compared cells elicited by vaccination (Gag-specific) to cells elicited by SIV infection and unaffected by vaccination (Nef-specific). We found that N-803 treatment enhanced both the frequencies of bulk and proliferating antigen-specific CD8+ T cells elicited by vaccination and the antigen-specific CD8+ T cells elicited by SIV infection. In sum, we demonstrate that a therapeutic heterologous prime-boost-boost (HPBB) vaccine can elicit antigen-specific effector memory CD8+ T cells that are boosted by N-803.