Expression of a Recombinant Nucleocapsid Protein of Rift Valley Fever Virus in Vero Cells as an Immunofluorescence Antigen and Its Use for Serosurveillance in Traditional Cattle Herds in Zambia

Abstract

The open reading frame of the nucleocapsid protein (NP) of Rift Valley fever virus (RVFV) strain MP12 was cloned and expressed in Vero E6 cells. The recombinant NP (rNP)-expressing cells were used as antigens for an indirect immunofluorescent antibody assay (IFA). The rNP-based IFA and RVFV-infected Vero E6 cell (authentic antigen)-based IFA showed similar IFA profiles with immune rabbit serum, which was prepared by immunization with rNP expressed using a baculovirus vector. A total of 942 traditional cattle sera obtained in five districts in Central, Southern, and Western provinces of Zambia were screened for anti-RVFV antibodies by the authentic antigen-based and rNP-based IFAs. Significant agreement was obtained between the two IFAs. The findings show that the rNP-based IFA is a safe and useful diagnostic tool as an alternative to the authentic antigen-based IFA. The antibody titers given by the rNP-based IFA were higher than those by the authentic antigen-based IFA. Therefore, the rNP-based IFA might be useful for serosurveillance of RVFV infection among cattle. Antibody prevalence rates in the five districts were 1.3% to 13.5% in the authentic antigen-based IFA and 6.0% to 21.4% in the rNP-based IFA. The results indicated that despite no reports of active cases of RVF in these provinces of Zambia, the virus is circulating among cattle herds.

Crossing the Line: Seroprevalence and Risk Factors for Transboundary Animal Diseases Along the Tanzania-Zambia Border

“…The animal-level and herd-level seroprevalence of RVFV in this study was 2.26% and 5.62% in Zambia, and 3.26 and 9.15% in Tanzania. As no RVFV outbreak has been reported in Zambia since 1989 (27) or in Tanzania since 2007 (28,29), these results may indicate inter-epidemic circulation of RVFV in the area, something that has previously been found in both Zambia (60,61) and Tanzania (62,63). This result is similar to findings in previous studies conducted during inter-epizootic periods in Tanzania, where animal-level seroprevalence in sheep and goats ranged from 5.4 to 11.7% (62)(63)(64).…”

Serologic and molecular evidence for circulation of Crimean-Congo hemorrhagic fever virus in ticks and cattle in Zambia

“…A total of 1,047 individual cattle serum samples collected in the previous study [ 8 ] during 2012–2014 and a follow-up study in 2015 from traditional cattle herds in six districts of four provinces of Zambia (Shibuyunji in Lusaka Province, Mumbwa in Central Province, Mazabuka and Kazungula in Southern Province, and Mwandi and Sesheke in Western Province) were used for the serologic screening ( Fig 1 and Table 1 ). For the genetic screening of CCHFV genome, total RNA was extracted from randomly selected 526 samples out of 1,047 cattle sera using QIAamp Viral RNA Mini Kit (Qiagen) according to the manufacturer’s instructions.…”

Mosquito-Borne Viral Pathogens Detected in Zambia: A Systematic Review

“…Using a recently developed diagnostic tool on a recombinant nucleocapsid protein (rNP)-based indirect immunofluorescent antibody assay (IFA), it was found that the seroprevalence of RVF varied between 6.0% to 21.4% among cattle herds in Central, Southern and Western provinces [ 19 ].…”

“…A total of 16 studies were included in this review, and all the 16 studies described the sampling approaches used in selecting the sample. Most of the studies (12) were cross-sectional studies [16][17][18][19][20][21][22][23][24][25][26][27]. Seven research studies were conducted in humans [15,16,22,23,[27][28][29] while nine studies were conducted in animals and/or mosquitoes, and one study had both humans and animals [27].…”