Abstract
Small ruminant lentiviruses (SRLVs) infections lead to chronic diseases and remarkable economic losses undermining health and welfare of animals and the sustainability of farms. Early and definite diagnosis of SRLVs infections is the cornerstone for any control and eradication efforts; however, a “gold standard” test and/or diagnostic protocols with extensive applicability have yet to be developed. The main challenges preventing the development of a universally accepted diagnostic tool with sufficient sensitivity, specificity, and accuracy to be integrated in SRLVs control programs are the genetic variability of SRLVs associated with mutations, recombination, and cross-species transmission and the peculiarities of small ruminants’ humoral immune response regarding late seroconversion, as well as intermittent and epitope-specific antibody production. The objectives of this review paper were to summarize the available serological and molecular assays for the diagnosis of SRLVs, to highlight their diagnostic performance emphasizing on advantages and drawbacks of their application, and to discuss current and future perspectives, challenges, limitations and impacts regarding the development of reliable and efficient tools for the diagnosis of SRLVs infections.
Highlights
Small ruminant lentiviruses (SRLVs) are a group of non-oncogenic viruses of the family Retroviridae, that infect both sheep and goats causing chronic, incurable, inflammatory diseases known as maedi-visna (MV) and caprine arthritis-encephalitis (CAE) [1]
Se: sensitivity; Sp: specificity; a Sensitivity and specificity values for sheep; b Sensitivity and specificity values for goats; c Sensitivity and specificity values for milk samples; gp: glycoprotein; TM: transmembrane; Ref: reference. * before merge of Institut Pourquier by Idexx Laboratories in 2007; ** recombinant GAG-GST fusion protein expressed in E. coli; A: Checkit CAEV/MVV monophasic Dr Bommeli AG, Bern, Switzerland; B: enzyme-linked immunosorbent assay (ELISA) MAEDI VISNA/CAEV Institut Pourquier, Montpellier, France
Loop-mediated isothermal amplification (LAMP) and recombinase polymerase amplification lateral flow dipstick (RPA-LFD) techniques have been lately applied with success for CAEV diagnosis [96,97,98]
Summary
Small ruminant lentiviruses (SRLVs) are a group of non-oncogenic viruses of the family Retroviridae, that infect both sheep and goats causing chronic, incurable, inflammatory diseases known as maedi-visna (MV) and caprine arthritis-encephalitis (CAE) [1]. The unsatisfactory diagnostic performance of ELISAs are mainly attributed to: (i) the unfavorable combination of antigen used in the test with the infection stage, as the production of antibodies against matrix and capsid proteins (e.g., p25, p28, and p16) during early infection stages precedes the production of other antibodies; on the contrary they are almost eliminated at later stages in the infected animals, where antibodies against gp and gp135 prevail [27,54,55,56], (ii) the antigenic distance between the viral strain used in the development of the assay and the infecting strain of the examined animals; SRLVs are characterized by cross-reactivity [57,58], homologous humoral immune response in strain-specific epitopes reduces dramatically the sensitivity of ELISA test and leads to misdiagnosis [37,54,59,60], (iii) the late seroconversion of animals, the fluctuation of antibody response during animal’s life and the alternations between viremia and humoral immune responses [15,18,52,61], and (iv) the animal species; in goats, for example, a more robust reactivity against transmembrane glycoproteins compared to capsid proteins has been observed [37,55]. Se: sensitivity; Sp: specificity; a Sensitivity and specificity values for sheep; b Sensitivity and specificity values for goats; c Sensitivity and specificity values for milk samples; gp: glycoprotein; TM: transmembrane; Ref: reference. * before merge of Institut Pourquier by Idexx Laboratories in 2007; ** recombinant GAG (group-specific antigens)-GST (glutathione S-transferase) fusion protein expressed in E. coli; A: Checkit CAEV/MVV monophasic Dr Bommeli AG, Bern, Switzerland; B: ELISA MAEDI VISNA/CAEV Institut Pourquier, Montpellier, France
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