Evaluation of indirect fluorescent antibody test (IFAT) for the diagnosis and screening of lumpy skin disease using Bayesian method.

The performance of indirect fluorescence antibody test (IFAT) for serological diagnosis and screening of lumpy skin disease (LSD) was evaluated using methods without gold standard. Virus neutralization test (VNT) was used as the second test and the study sites were selected from two different geographical places in Ethiopia to get different disease prevalence. The analysis of conditional dependent Bayesian model for the accuracy of IFAT showed that sensitivity, specificity, prevalence of the population Pi(1) and the population Pi(2) were 0.92 (0.89-0.95), 0.88 (0.85-0.91), 0.28 (0.25-0.32) and 0.06 (0.048-0.075), respectively. The posterior inferences obtained for VNT sensitivity, specificity and conditional correlation between the tests for sensitivity (rhoD) and specificity (rhoDc) were 0.78 (0.74-0.83), 0.97 (0.95-0.99), 0.052 (-0.03-0.15) and 0.019 (-0.01-0.06), respectively. The interval estimation of conditional correlation for both sensitivity and specificity clusters around zero and thus conditional dependence between the two tests was not significant. Although accuracy measure would not be the only basis for test selection, the result of our study demonstrated that IFAT has a reasonable high accuracy to be used for the diagnosis and sero-surveillance analysis of LSD in the target population.

Nitric oxide synthesis during acute SIV mac251 infection of macaques.

During HIV1 infection, nitric oxide (NO) could significantly contribute to immune dysregulation by its multiple effects on the modulation of the host immune response. The in vivo regulation of NO production is attributable to several nitric oxide synthases, one of which is a cytokine-inducible enzyme (iNOS). In vitro experiments suggest that iNOS expression in macrophages may be directly modulated by HIV infection. Acute infection of macaques with a pathogenic strain of the simian immunodeficiency virus (SIV) represents a relevant animal model for the in vivo study of the relationships between iNOS expression and lentiviral replication. Indeed, acute infection in this model is characterized by high rates of viral replication associated with early cytokine dysregulations, in the absence of opportunistic infection. In our experiment, two cynomolgus macaques were inoculated intravenously with a pathogenic isolate of SIVmac251, and iNOS gene expression was investigated ex vivo during acute infection in mononuclear cells obtained from bronchoalveolar lavage (BALMCs). An enhancement of this gene expression was observed as early as the second week of infection, at the time of peak of systemic viraemia, and increased until day 31 p.i. This overexpression was concomitant with a marked linear increase in IFN gamma expression in BALMCs. At the time of systemic viral load peak, the production of NO in plasma of these two monkeys was evidenced by the detection of large amounts of nitrate.

Selective quasispecies transmission after systemic or mucosal exposure of macaques to simian immunodeficiency virus.

Sexual transmission is the major cause of the AIDS epidemic. For the development of new antiviral and vaccine strategies, we therefore need to understand the mechanisms by which lentiviruses cross the mucosal barrier and the subsequent pathogenic consequences. For this purpose, experimental approaches are greatly facilitated by the development of relevant animal models. In this study, macaques were inoculated intravenously, intrarectally, or intravaginally with a pathogenic cell-free isolate of SIVmac251. Patterns of virological and immunological events significantly differed between vaginally (transient viremia, late seroconversion) and intravenously or intrarectally inoculated monkeys (persistent viremia and early seroconversion). Two weeks after infection, analysis of the env gene nucleotide sequences of proviruses recovered from PBMCs demonstrated that most of the differences were observed in the V1 loop. Three viral variants were specifically associated with vaginal transmission, whereas no such selection was evidenced after intravenous or intrarectal transmissions. These results are in favor of specific mechanisms associated with vaginal transmission, implicating viral envelope structure.

Cytokine mRNA expression in mononuclear cells from different tissues during acute SIVmac251 infection of macaques.

We used semiquantitative RT-PCR to monitor the expression of mRNA encoding cytokines (IL-1 beta, IL-6, TNF-alpha, and IL-10) and IFN-gamma in fresh isolated peripheral blood mononuclear cells (PBMCs), lymph node mononuclear cells (LNMCs), and mononuclear cells obtained after bronchoalveolar lavages (BALMCs), of four cynomolgus macaques inoculated intravenously with a pathogenic isolate of simian immunodeficiency virus (SIVmac251). To investigate the effects of the viral load on the expression of the cytokines, two monkeys received 30 mg kg-1 day-1 of didanosine (ddI). The two nontreated monkeys became infected and seroconverted, whereas the ddI-treated monkeys were completely protected as demonstrated by all criteria of diagnosis of SIV infection. Concomitant with the peak of viral replication (2 weeks after the experimental inoculation), high levels of IL-6 mRNA were produced in PBMCs, LNMCs, and BALMCs of the two placebotreated infected monkeys. Overexpression of TNF-alpha and IL-10 mRNAs was sometimes observed in LNMCs and BALMCs. A progressive overexpression of IFN-gamma mRNA, starting 2 weeks after experimental inoculation, was observed in BALMCs from infected animals. Concurrently, a marked increase in the CD8+ lymphocyte percentage in the BAL fluids was detected by FACS analysis. Thus, our results emphasize the importance of a comparative study of the expression of cytokines in different tissues. They suggest the interactions of monocyte/macrophage monokine production with viral replication, as well as the role of IFN-gamma in the development of lung cellular immunity to SIV infection.