Murine Leukemia Virus Spreading in Mice Impaired in the Biogenesis of Secretory Lysosomes and Ca2+-Regulated Exocytosis

Retroviruses have been observed to bud intracellularly into multivesicular bodies (MVB), in addition to the plasma membrane. Release from MVB is thought to occur by Ca(2+)-regulated fusion with the plasma membrane.To address the role of the MVB pathway in replication of the murine leukemia virus (MLV) we took advantage of mouse models for the Hermansky-Pudlak syndrome (HPS) and Griscelli syndrome. In humans, these disorders are characterized by hypopigmentation and immunological alterations that are caused by defects in the biogenesis and trafficking of MVBs and other lysosome related organelles. Neonatal mice for these disease models lacking functional AP-3, Rab27A and BLOC factors were infected with Moloney MLV and the spread of virus into bone marrow, spleen and thymus was monitored. We found a moderate reduction in MLV infection levels in most mutant mice, which differed by less than two-fold compared to wild-type mice. In vitro, MLV release form bone-marrow derived macrophages was slightly enhanced. Finally, we found no evidence for a Ca(2+)-regulated release pathway in vitro. Furthermore, MLV replication was only moderately affected in mice lacking Synaptotagmin VII, a Ca(2+)-sensor regulating lysosome fusion with the plasma membrane.Given that MLV spreading in mice depends on multiple rounds of replication even moderate reduction of virus release at the cellular level would accumulate and lead to a significant effect over time. Thus our in vivo and in vitro data collectively argue against an essential role for a MVB- and secretory lysosome-mediated pathway in the egress of MLV

TRIM E3 ligases interfere with early and late stages of the retroviral life cycle.

Members of the TRIpartite interaction Motif (TRIM) family of E3 ligases have been shown to exhibit antiviral activities. Here we report a near comprehensive screen for antiretroviral activities of 55 TRIM proteins (36 human, 19 mouse). We identified approximately 20 TRIM proteins that, when transiently expressed in HEK293 cells, affect the entry or release of human immunodeficiency virus 1 (HIV), murine leukemia virus (MLV), or avian leukosis virus (ALV). While TRIM11 and 31 inhibited HIV entry, TRIM11 enhanced N-MLV entry by interfering with Ref1 restriction. Strikingly, many TRIM proteins affected late stages of the viral life cycle. Gene silencing of endogenously expressed TRIM 25, 31, and 62 inhibited viral release indicating that they play an important role at late stages of the viral life cycle. In contrast, downregulation of TRIM11 and 15 enhanced virus release suggesting that these proteins contribute to the endogenous restriction of retroviruses in cells

Replication Dynamics of Mycobacterium tuberculosis in Chronically Infected Mice

The dynamics of host-pathogen interactions have important implications for the design of new antimicrobial agents to treat chronic infections such as tuberculosis (TB), which is notoriously refractory to conventional drug therapy. In the mouse model of TB, an acute phase of exponential bacterial growth in the lungs is followed by a chronic phase characterized by relatively stable numbers of bacteria. This equilibrium could be static, with little ongoing replication, or dynamic, with continuous bacterial multiplication balanced by bacterial killing. A static model predicts a close correspondence between “viable counts” (live bacteria) and “total counts” (live plus dead bacteria) in the lungs over time. A dynamic model predicts the divergence of total counts and viable counts over time due to the accumulation of dead bacteria. Here, viable counts are defined as bacterial CFU enumerated by plating lung homogenates; total counts are defined as bacterial chromosome equivalents (CEQ) enumerated by using quantitative real-time PCR. We show that the viable and total bacterial counts in the lungs of chronically infected mice do not diverge over time. Rapid degradation of dead bacteria is unlikely to account for the stability of bacterial CEQ numbers in the lungs over time, because treatment of mice with isoniazid for 8 weeks led to a marked reduction in the number of CFU without reducing the number of CEQ. These observations support the hypothesis that the stable number of bacterial CFU in the lungs during chronic infection represents a static equilibrium between host and pathogen

MLV spreading in mouse models for Hermansky-Pudlak and Griscelli syndromes.

<p>Wildtype and mutant mice were infected with Moloney MLV by intraperitoneal injection 3 days after birth. Bone marrow, spleen, and thymus were harvested 18 days post-infection and the genomic DNA analyzed. The copy number for proviral MLV was normalized to cell numbers using internal standards for actin A1. Rab27a (<i>ashen</i>) is compared to its wildtype background <i>C3H/Hej</i>, while the remaining AP-3 (<i>pearl</i>), BLOC-1 (<i>pallid</i>), BLOC-2 (<i>ruby-eye</i>), BLOC-3 (<i>light-ear</i>), double mutant BLOC-2,3 (<i>cocoa/light-ear</i>) and triple mutant (<i>pallid/cocoa/light-ear</i>) are compared to <i>C57BL/6J</i>. The statistical analysis with standard deviations is presented in the lower panel, in which infection levels observed in both wild-type background mice are set to 100%. Values labeled with an asterisks (*) indicates statistically significant differences to wildtype using the non-parametric Mann-Whitney double T-Test with a confidence level of 95%.</p

Impact of COVID-19 Vaccination on Healthcare Worker Infection Rate and Outcome during SARS-CoV-2 Omicron Variant Outbreak in Hong Kong

Immune escape is observed with SARS-CoV-2 Omicron (Pango lineage B.1.1.529), the predominant circulating strain worldwide. A booster dose was shown to restore immunity against Omicron infection; however, real-world data comparing mRNA (BNT162b2; Comirnaty) and inactivated vaccines&rsquo; (CoronaVac; Sinovac) homologous and heterologous boosting are lacking. A retrospective study was performed to compare the rate and outcome of COVID-19 in healthcare workers (HCWs) with various vaccination regimes during a territory-wide Omicron BA.2.2 outbreak in Hong Kong. During the study period from 1 February to 31 March 2022, 3167 HCWs were recruited, and 871 HCWs reported 746 and 183 episodes of significant household and non-household close contact. A total of 737 HCWs acquired COVID-19, all cases of which were all clinically mild. Time-dependent Cox regression showed that, compared with two-dose vaccination, three-dose vaccination reduced infection risk by 31.7% and 89.3% in household contact and non-household close contact, respectively. Using two-dose BNT162b2 as reference, two-dose CoronaVac recipient had significantly higher risk of being infected (HR 1.69 p &lt; 0.0001). Three-dose BNT162b2 (HR 0.4778 p&lt; 0.0001) and two-dose CoronaVac + BNT162b2 booster (HR 0.4862 p = 0.0157) were associated with a lower risk of infection. Three-dose CoronaVac and two-dose BNT162b2 + CoronaVac booster were not significantly different from two-dose BNT162b2. The mean time to achieve negative RT-PCR or E gene cycle threshold 31 or above was not affected by age, number of vaccine doses taken, vaccine type, and timing of the last dose. In summary, we have demonstrated a lower risk of breakthrough SARS-CoV-2 infection in HCWs given BNT162b2 as a booster after two doses of BNT162b2 or CoronaVac

Risks and Mitigating Factors in Psychosocial Adjustment of Spousal Caregivers of People with Dementia

By applying the Stress Process Model to examine the characteristics of people with dementia and their spousal caregivers, this study aims to identify the potential risk and mitigating factors of psychosocial adjustment among the spousal caregivers. We recruited 80 care recipient-caregiver couples in Hong Kong and examined the relationships of socio-economic, care recipient’s, and caregiver’s factors with spousal caregivers’ psychosocial adjustment. It was found that care recipients’ cognitive functions were associated with caregivers’ reported frequencies of their behavioral and psychological symptoms of dementia (BPSD) (r = .30, p = .008), and caregivers’ perceived burden of caregiving (r = -.54, p = .008). Caregivers’ quality of life was associated with their perceived caregiving burden (r = -.82, p = .001) and self-efficacy (r = .32, p = .001). Upon further examining the caregiving model with these parameters, a significant multivariate general linear model was found with (F (1, 12) = 13.06, p = .001, partial eta square = .70, observed power = .99). Moreover, female caregivers reported higher sense of caregiving stress and poorer quality of life than male caregivers. This study found that the cognitive functions and BPSD of care recipients with dementia and perceived level of caregiving burden are strongly associated with degrees of psychosocial adjustment among their spousal caregivers. The self-perceived caregiving role in a family is also a possible confounding factor contributing to the perceived caregiving burden. To support in-home caregiving of people with dementia, strategies to empower spousal caregivers to execute their caregiving roles are recommended