Antibody response in sheep experimentally infected with different small ruminant lentivirus genotypes

Abstract

Two groups of sheep were experimentally infected by intratracheal route with two small ruminant lentivirus (SRLV) isolates belonging to different genotypes (It-561 genotype A3 and It-Pi1 genotype B2). Seroconversion was evaluated using recombinant homologous and heterologous matrix protein/capsid antigen fusion protein. Results clearly indicate that seroconversion against homologous antigen was detected well in advance as regards heterologous antigen in both groups, although the advantage of using homologous antigen was less evident in detecting seroconversion against the caprine arthritis encephalitis virus (CAEV)-like strain, compared with the maedi-visna virus (MVV)-like infection. Commercially available ELISAs detect CAEV-like seroconversion earlier than MVV-like infection suggesting a closer relationship between CAEV-like isolate and the antigen used in the latter ELISA tests. Seven recombinant subunits developed from matrix protein and capsid antigen of strain K1514 (prototype A1) were used to better define the antibody response in sheep infected with It-561 isolate. Two animals clearly reacted against type specific epitopes in the early stage of infection.This study highlights the relative insensitivity of gag encoded cross-reacting epitopes during the early stage of infection and suggests the development of novel diagnostic tests based on both genotype specific antigens. #

Seroconversion against SU5 derived synthetic peptides in sheep experimentally infected with different SRLV genotypes

“…SRLV infection, however, does not involve the lymphocyte compartment, and sheep 1 antibody titer does not decrease, therefore a different mechanism may be responsible. A comparison of the results obtained in this study and in Lacerenza et al (2006) shows that both CA--MA fusion antigens and SU5 peptides detect infection at early stages, from week three onwards. Furthermore, while It--561 drives type--specific antibody response towards both Gag and Env antigens, It--Pi1 seems to drive production of type--specific antibody only against SU5.…”

“…In the last years serological assays based on Gag antigens derived from Italian isolates belonging to both phylogenetic groups were developed and applied in field conditions: the response obtained was largely type--specific, indicating the opportunity to use antigens representative of both genotypes to improve the sensitivity of the diagnostic assays (Grego et al, 2002 andGrego et al, 2005). Furthermore, when sequential sera collected from sheep experimentally infected with either It--561 or with It--Pi1, were analyzed by ELISA with both homologous and heterologous CA--MA fusion proteins, the homologous antigen detected infected animals up to months before the heterologous antigen (Lacerenza et al, 2006). In this study the same panel of sequential sera was analyzed with an Env ELISA based on It--561 and It--Pi1 SU5 peptides.…”

“…Infection of sheep with these strains has been described by Lacerenza et al (2006). Detection of viral sequences in blood of experimental sheep was done by LTR PCR ( Extramiana et al, 2002) and Pol PCR ( Grego et al, 2002).…”

“…Recent analysis of two Italian SRLV isolates, MVV--like It--561 and CAEV--like It--Pi1, demonstrated that gag--encoded capsid (CA) and matrix (MA) proteins carry type--specific epitopes and most sheep and goat sera reacted to these antigens in a type--specific manner, irrespective of the species of origin (Grego et al, 2002 andGrego et al, 2005). Furthermore, homologous CA--MA fusion protein was able to detect seroconversion at an earlier stage compared to the heterologous protein (Lacerenza et al, 2006). The present study extends the analysis of the humoral response induced by It--561 and It--Pi1 to SU5, one of the major epitopes of the envelope (Env) protein (Bertoni et al, 2000 andValas et al, 2000).…”

Specific detection of small ruminant lentiviral nucleic acid sequences located in the proviral long terminal repeat and leader-gag regions using real-time polymerase chain reaction

“…Drawbacks of serological methods may include epitope specific reactivity (Grego et al, 2005;Lacarenza et al, 2006) and the sometimes slow antibody response to infection (Rimstad et al, 1993;Vogt et al, 2000). Theoretically, PCR may overcome these disadvantages by detecting the provirus in an early stage of infection, i.e.…”