Effect of Single Housing on Innate Immune Activation in Immunodeficiency Virus-Infected Pigtail Macaques ( Macaca nemestrina ) as a Model of Psychosocial Stress in Acute HIV Infection.

OBJECTIVE: Simian immunodeficiency virus (SIV) infection of macaques recapitulates many aspects of HIV pathogenesis and is similarly affected by both genetic and environmental factors. Psychosocial stress is associated with immune system dysregulation and worse clinical outcomes in people with HIV. This study assessed the impact of single housing, as a model of psychosocial stress, on innate immune responses of pigtailed macaques ( Macaca nemestrina ) during acute SIV infection. METHODS: A retrospective analysis of acute SIV infection of 2- to si6-year-old male pigtailed macaques was performed to compare the innate immune responses of socially ( n = 41) and singly ( n = 35) housed animals. Measures included absolute monocyte count and subsets, and in a subset ( n ≤ 18) platelet counts and activation data. RESULTS: SIV infection resulted in the expected innate immune parameter changes with a modulating effect from housing condition. Monocyte number increased after infection for both groups, driven by classical monocytes (CD14 + CD16 - ), with a greater increase in socially housed animals (227%, p < .001, by day 14 compared with preinoculation time points). Platelet numbers recovered more quickly in the socially housed animals. Platelet activation (P-selectin) increased by 65% ( p = .004) and major histocompatibility complex class I surface expression by 40% ( p = .009) from preinoculation only in socially housed animals, whereas no change in these measures occurred in singly housed animals. CONCLUSIONS: Chronic psychosocial stress produced by single housing may play an immunomodulatory role in the innate immune response to acute retroviral infection. Dysregulated innate immunity could be one of the pathways by which psychosocial stress contributes to immune suppression and increased disease severity in people with HIV.

Activity of Plasmodium vivax promoter elements in Plasmodium knowlesi, and a centromere-containing plasmid that expresses NanoLuc throughout the parasite life cycle.

BACKGROUND: Plasmodium knowlesi is now the major cause of human malaria in Malaysia, complicating malaria control efforts that must attend to the elimination of multiple Plasmodium species. Recent advances in the cultivation of P. knowlesi erythrocytic-stage parasites in vitro, transformation with exogenous DNA, and infection of mosquitoes with gametocytes from culture have opened up studies of this pathogen without the need for resource-intensive and costly non-human primate (NHP) models. For further understanding and development of methods for parasite transformation in malaria research, this study examined the activity of various trans-species transcriptional control sequences and the influence of Plasmodium vivax centromeric (pvcen) repeats in plasmid-transfected P. knowlesi parasites. METHODS: In vitro cultivated P. knowlesi parasites were transfected with plasmid constructs that incorporated Plasmodium vivax or Plasmodium falciparum 5' UTRs driving the expression of bioluminescence markers (firefly luciferase or Nanoluc). Promoter activities were assessed by bioluminescence, and parasites transformed with human resistant allele dihydrofolate reductase-expressing plasmids were selected using antifolates. The stability of transformants carrying pvcen-stabilized episomes was assessed by bioluminescence over a complete parasite life cycle through a rhesus macaque monkey, mosquitoes, and a second rhesus monkey. RESULTS: Luciferase expression assessments show that certain P. vivax promoter regions, not functional in the more evolutionarily-distant P. falciparum, can drive transgene expression in P. knowlesi. Further, pvcen repeats may improve the stability of episomal plasmids in P. knowlesi and support detection of NanoLuc-expressing elements over the full parasite life cycle from rhesus macaque monkeys to Anopheles dirus mosquitoes and back again to monkeys. In assays of drug responses to chloroquine, G418 and WR9910, anti-malarial half-inhibitory concentration (IC50) values of blood stages measured by NanoLuc activity proved comparable to IC50 values measured by the standard SYBR Green method. CONCLUSION: All three P. vivax promoters tested in this study functioned in P. knowlesi, whereas two of the three were inactive in P. falciparum. NanoLuc-expressing, centromere-stabilized plasmids may support high-throughput screenings of P. knowlesi for new anti-malarial agents, including compounds that can block the development of mosquito- and/or liver-stage parasites.

Platelet-endothelial associations may promote cytomegalovirus replication in the salivary gland in mice.

Platelet decline is a feature of many acute viral infections, including cytomegalovirus (CMV) infection in humans and mice. Platelet sequestration in association with other cells, including endothelium and circulating leukocytes, can contribute to this decline and influence the immune response to and pathogenesis of viral infection. We sought to determine if platelet-endothelial associations (PEAs) contribute to platelet decline during acute murine CMV (mCMV) infection, and if these associations affect viral load and production. Male BALB/c mice were infected with mCMV (Smith strain), euthanized at timepoints throughout acute infection and compared to uninfected controls. An increase in PEA formation was confirmed in the salivary gland at all post-inoculation timepoints using immunohistochemistry for CD41+ platelets co-localizing with CD34+ vessels. Platelet depletion did not change amount of viral DNA or timecourse of infection, as measured by qPCR. However, platelet depletion reduced viral titer of mCMV in the salivary glands while undepleted controls demonstrated robust replication in the tissue by plaque assay. Thus, platelet associations with endothelium may enhance the ability of mCMV to replicate within the salivary gland. Further work is needed to determine the mechanisms behind this effect and if pharmacologic inhibition of PEAs may reduce CMV production in acutely infected patients.

The Role of Animal Research in Pandemic Responses.

The significant advances made by the global scientific community during the COVID-19 pandemic, exemplified by the development of multiple SARS-CoV-2 vaccines in less than 1 y, were made possible in part because of animal research. Historically, animals have been used to study the characterization, treatment, and prevention of most of the major infectious disease outbreaks that humans have faced. From the advent of modern 'germ theory' prior to the 1918 Spanish Flu pandemic through the more recent Ebola and Zika virus outbreaks, research that uses animals has revealed or supported key discoveries in disease pathogenesis and therapy development, helping to save lives during crises. Here we summarize the role of animal research in past pandemic and epidemic response efforts, as well as current and future considerations for animal research in the context of infectious disease research.

Sex differences in lung imaging and SARS-CoV-2 antibody responses in a COVID-19 golden Syrian hamster model.

In the ongoing coronavirus disease 2019 (COVID-19) pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), more severe outcomes are reported in males compared with females, including hospitalizations and deaths. Animal models can provide an opportunity to mechanistically interrogate causes of sex differences in the pathogenesis of SARS-CoV-2. Adult male and female golden Syrian hamsters (8-10 weeks of age) were inoculated intranasally with 10 5 TCID 50 of SARS-CoV-2/USA-WA1/2020 and euthanized at several time points during the acute (i.e., virus actively replicating) and recovery (i.e., after the infectious virus has been cleared) phases of infection. There was no mortality, but infected male hamsters experienced greater morbidity, losing a greater percentage of body mass, developing more extensive pneumonia as noted on chest computed tomography, and recovering more slowly than females. Treatment of male hamsters with estradiol did not alter pulmonary damage. Virus titers in respiratory tissues, including nasal turbinates, trachea, and lungs, and pulmonary cytokine concentrations, including IFNb and TNFa, were comparable between the sexes. However, during the recovery phase of infection, females mounted two-fold greater IgM, IgG, and IgA responses against the receptor-binding domain of the spike protein (S-RBD) in both plasma and respiratory tissues. Female hamsters also had significantly greater IgG antibodies against whole inactivated SARS-CoV-2 and mutant S-RBDs, as well as virus neutralizing antibodies in plasma. The development of an animal model to study COVID-19 sex differences will allow for a greater mechanistic understanding of the SARS-CoV-2 associated sex differences seen in the human population.