Biology subjects

Malaviarachchi, P. A.

Publications and source records attributed to Malaviarachchi, P. A..

3 recordsLinked to original sources

bioRxiv2023

An ex vivo human precision-cut lung slice platform provides insight into SARS-CoV-2 pathogenesis and antiviral drug efficacy

COVID-19 has claimed millions of lives since the emergence of SARS-CoV-2, and lung disease appears the primary cause of the death in COVID-19 patients. However, the underlying mechanisms of COVID-19 pathogenesis remain elusive, and there is no existing model where the human disease can be faithfully recapitulated and conditions for the infection process can be experimentally controlled. Herein we report the establishment of an ex vivo human precision-cut lung slice (hPCLS) platform for studying SARS-CoV-2 pathogenicity and innate immune responses, and for evaluating the efficacy of antiviral drugs against SARS-CoV-2. We show that while SARS-CoV-2 continued to replicate during the course of infection of hPCLS, infectious virus production peaked within 2 days, and rapidly declined thereafter. Although most proinflammatory cytokines examined were induced by SARS-CoV-2 infection, the degree of induction and types of cytokines varied significantly among hPCLS from individual donors, reflecting the heterogeneity of human populations. In particular, two cytokines (IP-10 and IL-8) were highly and consistently induced, suggesting a role in the pathogenesis of COVID-19. Histopathological examination revealed focal cytopathic effects late in the infection. Transcriptomic and proteomic analyses identified molecular signatures and cellular pathways that are largely consistent with the progression of COVID-19 in patients. Furthermore, we show that homoharringtonine, a natural plant alkaloid derived from Cephalotoxus fortunei, not only inhibited virus replication but also production of pro-inflammatory cytokines, and ameliorated the histopathological changes of the lungs caused by SARS-CoV-2 infection, demonstrating the usefulness of the hPCLS platform for evaluating antiviral drugs. SIGNIFICANCEHere we established an ex vivo human precision-cut lung slice platform for assessing SARS-CoV-2 infection, viral replication kinetics, innate immune response, disease progression, and antiviral drugs. Using this platform, we identified early induction of specific cytokines, especially IP-10 and IL-8, as potential predictors for severe COVID-19, and uncovered a hitherto unrecognized phenomenon that while infectious virus disappears at late times of infection, viral RNA persists and lung histopathology commences. This finding may have important clinical implications for both acute and post-acute sequelae of COVID-19. This platform recapitulates some of the characteristics of lung disease observed in severe COVID-19 patients and is therefore a useful platform for understanding mechanisms of SARS-CoV-2 pathogenesis and for evaluating the efficacy of antiviral drugs.

microbiology↗

bioRxiv2022

IFNγ and antibody synergize to enhance protective immunity against Chlamydia dissemination and female reproductive tract reinfections

CD4 T cell-dependent IFN{gamma} production and antibody are the two best known effectors for protective immunity against Chlamydia female reproductive tract (FRT) infection. Nevertheless, mice lacking either IFN{gamma} or B cells are capable of clearing vast majority of Chlamydia from the female reproductive tract (FRT), while suffering from varying degrees of disseminated infection. In this study, we investigated whether IFN{gamma} and B cells play complimentary roles in host defense against Chlamydia and evaluated their relative contributions in systemic and mucosal tissues. Using mice deficient in both IFN{gamma} and B cells (IFN{gamma}-/- x {micro}MT), we showed that mice lacking both effectors are highly susceptible to lethal systemic Chlamydia dissemination. Passive transfer of immune convalescent serum, but not recombinant IFN{gamma}, reduced bacterial burden in both systemic and mucosal tissues in IFN{gamma}-/- x {micro}MT mice. Moreover, we observed a reduction of bacterial shedding of more than two orders of magnitude in IFN{gamma}-/- x {micro}MT mice following both Chlamydia muridarum and Chlamydia trachomatis infections. Lastly, protective immunity against C. muridarum reinfection was completely abrogated in the absence of IFN{gamma} and B cells. Our results suggest that IFN{gamma} and B cells synergize to combat bacterial dissemination, while an IFN{gamma} and B cell-independent mechanism exists for host resistance to Chlamydia in the FRT.

immunology↗

bioRxiv2020

Innate IFNγ is essential for systemic Chlamydia control while CD4 T cell-dependent IFNγ production is highly redundant in the female reproductive tract

Protective immunity to the obligate intracellular bacterium Chlamydia is thought to rely on CD4 T cell-dependent IFN{gamma} production. Nevertheless, whether IFN{gamma} is produced by other cellular source during Chlamydia infection and how CD4 T cell-dependent and -independent IFN{gamma} contribute differently to host resistance has not been carefully evaluated. In this study, we dissect the requirements of IFN{gamma} produced by innate immune cells and CD4 T cells for resolution of Chlamydia muridarum female reproductive tract (FRT) infection. After C. muridarum intravaginal inoculation, IFN{gamma}-deficient and T cell-deficient mice exhibited opposite phenotypes for survival and bacterial shedding at the FRT mucosa, demonstrating the distinct requirements for IFN{gamma} and CD4 T cells in host defense against Chlamydia. In Rag-deficient mice, IFN{gamma} produced by innate lymphocytes (ILCs) accounted for early bacterial containment and prolonged survival in the absence of adaptive immunity. Although group I ILCs are potent IFN{gamma} producers, we found that mature NK cells and ILC1 were not the sole source for innate IFN{gamma} in response to Chlamydia. T cell adoptive transfer experiments revealed that WT and IFN{gamma}-deficient CD4 T cells were equally capable of mediating effective bacterial killing in the FRT during the early stage of Chlamydia infection. Together, our results revealed that innate IFN{gamma} is essential for preventing systemic Chlamydia dissemination, whereas IFN{gamma} produced by CD4 T cells is largely dispensable at the FRT mucosa.

immunology↗