Antiretroviral Treatment Start-Time during Primary SIVmac Infection in Macaques Exerts a Different Impact on Early Viral Replication and Dissemination

BACKGROUND: The time of infection is rarely known in human cases; thus, the effects of delaying the initiation of antiretroviral therapy (ART) on the peripheral viral load and the establishment of viral reservoirs are poorly understood. METHODOLOGY/PRINCIPAL FINDINGS: Six groups of macaques, infected intravenously with SIV(mac251), were given placebo or antiretroviral therapy to explore reservoir establishment; macaques were treated for 2 weeks, with treatment starting 4 hours, 7 or 14 days after infection. Viral replication and dissemination were measured in the gut (rectum), in the lung and in blood and lymphoid tissues (peripheral lymph nodes), by quantifying viral RNA, DNA and 2LTR circles. We used immunohistochemistry (CD4 and CD68) to assess the impact of these treatments on the relative amount of virus target cells in tissue. Treatment that was started 4 hours post-infection (pi) decreased viral replication and dissemination in blood and tissue samples, which were assessed on day 14 (RNA/DNA/2LTR circles). The virus remained detectable and lymphoid tissues were activated in LN and the gut in both placebo- and ART-treated animals. Viral RNA in plasma continued to be lower in macaques treated seven days after infection; however, this was not the case for viral DNA in peripheral blood mononuclear cells. There was a small but significant difference in RNA and DNA levels in tissues between placebo- and ART-treated animals on day 21. When started 14 days after infection, treatment resulted in a limited decrease in the plasma viral load. CONCLUSIONS: Treatment that was started 4 hours after infection significantly reduced viral replication and dissemination. When started 7 days after infection, it was of slight virological benefit in peripheral blood and in tissues, and treatment was even less effective if started 14 days pi. These data favor starting ART no longer than one week after intravenous SIV(mac251) exposure

Modelling the response to vaccine in non-human primates to define SARS-CoV-2 mechanistic correlates of protection

The definition of correlates of protection is critical for the development of next-generation SARS-CoV-2 vaccine platforms. Here, we propose a model-based approach for identifying mechanistic correlates of protection based on mathematical modelling of viral dynamics and data mining of immunological markers. The application to three different studies in non-human primates evaluating SARS-CoV-2 vaccines based on CD40-targeting, two-component spike nanoparticle and mRNA 1273 identifies and quantifies two main mechanisms that are a decrease of rate of cell infection and an increase in clearance of infected cells. Inhibition of RBD binding to ACE2 appears to be a robust mechanistic correlate of protection across the three vaccine platforms although not capturing the whole biological vaccine effect. The model shows that RBD/ACE2 binding inhibition represents a strong mechanism of protection which required significant reduction in blocking potency to effectively compromise the control of viral replication.Initiative for the creation of a Vaccine Research InstituteInfrastructure nationale pour la modélisation des maladies infectieuses humaine

Isolation and phenotypic characterization of human and nonhuman primate intestinal lamina propria mononuclear cells

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Loss of reactivity of vaccine-induced CD4 T cells in immunized monkeys after SIV/HIV challenge.

International audienceBACKGROUND: Immunization protocols involving priming with DNA and boosting with recombinant live virus vectors such as recombinant modified Vaccinia Ankara (rMVA) are considered as vaccine candidates against HIV. Such protocols improve the outcome of simian/human immunodeficiency virus (SHIV) pathogenic challenge in Rhesus monkeys. OBJECTIVES: To investigate the fate of vaccine-induced T cells after a mucosal SHIV challenge. METHODS: We immunized Rhesus monkeys (Macaca mulatta) by DNA priming followed by rMVA boost. After intrarectal challenge with SHIV 89.6P, immunized animals demonstrated early control of viral replication and stable CD4 T-cell counts. We monitored T-cell responses by measuring IFN-gamma secretion and proliferation. RESULTS: Immunization induced strong and sustained SHIV-specific CD4 and CD8 T-cell responses. CD8 T-cell responses were recalled during acute infection, whereas none of the vaccine-induced SHIV-specific CD4 T-cell responses were recalled. Moreover, most of the CD4 T-cell responses became undetectable in peripheral blood or lymph nodes even after in-vitro peptide stimulation. In contrast, we persistently detected CD4 T-cell responses specific for control recall antigens in infected animals. CONCLUSION: SHIV 89.6P challenge results in a lack of reactivity of vaccine-induced SHIV-specific CD4 T cells. These results may have important implications in the AIDS vaccine field, especially for the evaluation of new vaccine candidates, both in preventive and therapeutic trials

Changes in Soluble Factor-Mediated CD8(+) Cell-Derived Antiviral Activity in Cynomolgus Macaques Infected with Simian Immunodeficiency Virus SIVmac251: Relationship to Biological Markers of Progression

Cross-sectional studies have shown that the capacity of CD8(+) cells from human immunodeficiency virus (HIV)-infected patients and simian immunodeficiency virus (SIV) SIVmac-infected macaques to suppress the replication of human and simian immunodeficiency viruses in vitro depends on the clinical stage of disease, but little is known about changes in this antiviral activity over time in individual HIV-infected patients or SIV-infected macaques. We assessed changes in the soluble factor-mediated noncytolytic antiviral activity of CD8(+) cells over time in eight cynomolgus macaques infected with SIVmac251 to determine the pathophysiological role of this activity. CD8(+) cell-associated antiviral activity increased rapidly in the first week after viral inoculation and remained detectable during the early phase of infection. The net increase in antiviral activity of CD8(+) cells was correlated with plasma viral load throughout the 15 months of follow-up. CD8(+) cells gradually lost their antiviral activity over time and acquired virus replication-enhancing capacity. Levels of antiviral activity correlated with CD4(+) T-cell counts after viral set point. Concentrations of β-chemokines and interleukin-16 in CD8(+) cell supernatants were not correlated with this antiviral activity, and α-defensins were not detected. The soluble factor-mediated antiviral activity of CD8(+) cells was neither cytolytic nor restricted to major histocompatibility complex. This longitudinal study strongly suggests that the increase in noncytolytic antiviral activity from baseline and the maintenance of this increase over time in cynomolgus macaques depend on both viral replication and CD4(+) T cells

Dynamics of viral replication in blood and lymphoid tissues during SIVmac251 infection of macaques

<p>Abstract</p> <p>Background</p> <p>Extensive studies of primary infection are crucial to our understanding of the course of HIV disease. In SIV-infected macaques, a model closely mimicking HIV pathogenesis, we used a combination of three markers -- viral RNA, 2LTR circles and viral DNA -- to evaluate viral replication and dissemination simultaneously in blood, secondary lymphoid tissues, and the gut during primary and chronic infections. Subsequent viral compartmentalization in the main target cells of the virus in peripheral blood during the chronic phase of infection was evaluated by cell sorting and viral quantification with the three markers studied.</p> <p>Results</p> <p>The evolutions of viral RNA, 2LTR circles and DNA levels were correlated in a given tissue during primary and early chronic infection. The decrease in plasma viral load principally reflects a large decrease in viral replication in gut-associated lymphoid tissue (GALT), with viral RNA and DNA levels remaining stable in the spleen and peripheral lymph nodes. Later, during chronic infection, a progressive depletion of central memory CD4+ T cells from the peripheral blood was observed, accompanied by high levels of viral replication in the cells of this subtype. The virus was also found to replicate at this point in the infection in naive CD4+ T cells. Viral RNA was frequently detected in monocytes, but no SIV replication appeared to occur in these cells, as no viral DNA or 2LTR circles were detected.</p> <p>Conclusion</p> <p>We demonstrated the persistence of viral replication and dissemination, mostly in secondary lymphoid tissues, during primary and early chronic infection. During chronic infection, the central memory CD4+ T cells were the major site of viral replication in peripheral blood, but viral replication also occurred in naive CD4+ T cells. The role of monocytes seemed to be limited to carrying the virus as a cargo because there was an observed lack of replication in these cells. These data may have important implications for the targeting of HIV treatment to these diverse compartments.</p

Ricin intoxication: development of monoclonal and recombinant antibodies for diagnostic and therapeutic applications

International audienceIntroduction. Ricin is a protein produced by the plant Ricinus communis, known for its high toxicity. As ricin is readily available in nature, it represents a considerable biothreat. An early diagnosis of ricin intoxication as well as efficient medical countermeasures are therefore urgently needed. In the event of intentional or accidental poisoning, it is essential to treat as quickly as possible. In this context, vaccination, which takes several weeks to several months to achieve the right level of protection, is not appropriate. On the contrary, direct administration of antibodies, provides immediate protection. However, since ricin sequence can differ according to the isoform, developing efficient protective mAbs against ricin is challenging. We have developed and characterized several murine monoclonal antibodies for diagnostic and therapeutic applications. They have enabled the development of a highly sensitive and specific in vitro diagnostic immunoassay (sandwich ELISA) for ricin intoxication, which is now CE-IVD marked and commercially available. Some of these antibodies have been evaluated in in vitro and in vivo models, and have demonstrated excellent protection against ricin poisoning in mice.Materials and Methods. In vitro diagnostic test: monoclonal antibodies were produced by immunizing mice with inactivated ricin. The best antibodies were then selected for their ability to recognize ricin in ELISA. The performance of this test, in its research format, was then evaluated using plasma from ricin-intoxicated animals. An industrial prototype of the test was then designed, and its performance evaluated using human plasma.Medical countermeasures: several generations of ricin antibodies (murine monoclonal and recombinant camelid) were produced and evaluated for their neutralizing capacities in a cellular model. The best ones were then evaluated for their protective activity in an in vivo murine model of intranasal intoxication.Results. In vitro diagnostic test: In its research format, the sandwich ELISA test enables early detection of ricin in the blood of intratracheally poisoned macaques or intranasally poisoned mice.Medical countermeasures: the best antibodies gave intranasally intoxicated mice survival rates of 90% and 50% respectively when administered 6h and 18h post-intoxication.References1. J. Prigent et al., PLoS ONE. 6(5): e20166. (2011)2. M.L. Orsini Delgado et al., Toxins. 13(2):100 (2021