Chronic immune activation and gut barrier dysfunction is associated with neuroinflammation in ART-suppressed SIV+ rhesus macaques.

HIV-associated neurocognitive disorders (HAND) affect ~40% of virally suppressed people with HIV (PWH), however, the precise viral dependent and independent changes to the brain are unclear. Here we characterized the CNS reservoir and immune environment of SIV-infected (SIV+) rhesus macaques during acute (n = 4), chronic (n = 12) or ART-suppressed SIV infection (n = 11). Multiplex immunofluorescence for markers of SIV infection (vRNA/vDNA) and immune activation was performed on frontal cortex and matched colon tissue. SIV+ animals contained detectable viral DNA+ cells that were not reduced in the frontal cortex or the gut by ART, supporting the presence of a stable viral reservoir in these compartments. SIV+ animals had impaired blood brain barrier (BBB) integrity and heightened levels of astrocytes or myeloid cells expressing antiviral, anti-inflammatory or oxidative stress markers which were not abrogated by ART. Neuroinflammation and BBB dysfunction correlated with measures of viremia and immune activation in the gut. Furthermore, SIV-uninfected animals with experimentally induced gut damage and colitis showed a similar immune activation profile in the frontal cortex to those of SIV-infected animals, supporting the role of chronic gut damage as an independent source of neuroinflammation. Together, these findings implicate gut-associated immune activation/damage as a significant contributor to neuroinflammation in ART-suppressed HIV/SIV infection which may drive HAND pathogenesis.

Behavioral Phenotypes of Foxg1 Heterozygous Mice.

FOXG1 syndrome (FS, aka a congenital variant of Rett syndrome) is a recently defined rare and devastating neurodevelopmental disorder characterized by various symptoms, including severe intellectual disability, autistic features, involuntary, and continuous jerky movements, feeding problems, sleep disturbances, seizures, irritability, and excessive crying. FS results from mutations in a single allele of the FOXG1 gene, leading to impaired FOXG1 function. Therefore, in establishing mouse models for FS, it is important to test if heterozygous (HET) mutation in the Foxg1 gene, mimicking genotypes of the human FS individuals, also manifests phenotypes similar to their symptoms. We analyzed HET mice with a null mutation allele in a single copy of Foxg1, and found that they show various phenotypes resembling the symptoms of the human FS individuals. These include increased anxiety in the open field as well as impairment in object recognition, motor coordination, and fear learning and contextual and cued fear memory. Our results suggest that Foxg1 HET mice recapitulate at least some symptoms of the human FS individuals.

Combined protein and nucleic acid imaging reveals virus-dependent B cell and macrophage immunosuppression of tissue microenvironments.

Understanding the mechanisms of HIV tissue persistence necessitates the ability to visualize tissue microenvironments where infected cells reside; however, technological barriers limit our ability to dissect the cellular components of these HIV reservoirs. Here, we developed protein and nucleic acid in situ imaging (PANINI) to simultaneously quantify DNA, RNA, and protein levels within these tissue compartments. By coupling PANINI with multiplexed ion beam imaging (MIBI), we measured over 30 parameters simultaneously across archival lymphoid tissues from healthy or simian immunodeficiency virus (SIV)-infected nonhuman primates. PANINI enabled the spatial dissection of cellular phenotypes, functional markers, and viral events resulting from infection. SIV infection induced IL-10 expression in lymphoid B cells, which correlated with local macrophage M2 polarization. This highlights a potential viral mechanism for conditioning an immunosuppressive tissue environment for virion production. The spatial multimodal framework here can be extended to decipher tissue responses in other infectious diseases and tumor biology.

Effects of chronic exposure to a mixed field of neutrons and photons on behavioral and cognitive performance in mice.

To simulate the space radiation environment astronauts are exposed to, most studies involve acute exposures but during a space mission there will be chronic (long-lasting) exposures. To address this knowledge gap, a neutron irradiator using a 252Cf (252Californium) source was used to generate a mixed field of neutrons and photons to simulate chronic, low dose rate exposures to high LET radiation. In the present study, we assessed the effects chronic neutron exposure starting at 60 days of age on behavioral and cognitive performance of BALB/c female and C3H male mice at 600 and 700 days of age as part of an opportunistic study that took advantage of the availability of neutron and sham-irradiated mice from a radiation carcinogenesis experiment. There were profound dose- and time point-dependent effects of chronic neutron exposure. At the 600-day time point, irradiated BALB/c female mice showed improved nest building at all three doses. At the 700-day, but not 600-day, time point slightly but significantly increased body weights were seen in C3H male mice exposed to 0.118 Gy. At the 600-day time point BALB/c female mice irradiated with 0.2 Gy did, like sham-irradiated, not show preferential exploration of the novel object that was seen in mice irradiated with 0.118 or 0.4 Gy. In C3H male mice exposed to 0.4 Gy and at the 600-day time point, increased measures of anxiety were observed on days 1 and 2 in the open field. Thus, different outcome measures show distinct dose-response relationships, with some anticipated to worsen performance during space missions, like increased measures of anxiety, while other anticipated to enhance performance, such as increased nest building and object recognition.