Antibodies to henipavirus or henipa-like viruses in domestic pigs in Ghana, West Africa

Abstract

Henipaviruses, Hendra virus (HeV) and Nipah virus (NiV), have Pteropid bats as their known natural reservoirs. Antibodies against henipaviruses have been found in Eidolon helvum, an old world fruit bat species, and henipavirus-like nucleic acid has been detected in faecal samples from E. helvum in Ghana. The initial outbreak of NiV in Malaysia led to over 265 human encephalitis cases, including 105 deaths, with infected pigs acting as amplifier hosts for NiV during the outbreak. We detected non-neutralizing antibodies against viruses of the genus Henipavirus in approximately 5% of pig sera (N = 97) tested in Ghana, but not in a small sample of other domestic species sampled under a E. helvum roost. Although we did not detect neutralizing antibody, our results suggest prior exposure of the Ghana pig population to henipavirus(es). Because a wide diversity of henipavirus-like nucleic acid sequences have been found in Ghanaian E. helvum, we hypothesise that these pigs might have been infected by henipavirus(es) sufficiently divergent enough from HeVor NiV to produce cross-reactive, but not cross-neutralizing antibodies to HeV or NiV.

Figure 1. The M.F.I. of anti-NiV (Red) and HeV (Blue) antibodies from 2 cats (C), 2 dogs (D), 10 sheep (S) and 15 goats (G) from Ghana with NiV positive cat and negative (all species) control.

Figure 2. The median fluorescent intensities (M.F.I.) of 97 pig (P) sera from Ghana tested in pools of 2 or singly for antibodies against Nipah (NiV-Red) and Hendra (HeV-Blue) virus soluble glycoprotein (sG) attached to microspheres on the Luminex platform.

Positive and negative serum controls are shown.

Figure 3. Percentage inhibition of NiV and HeV sG-Ephrin-B2 receptor by Luminex binding assay positive pig (P) sera, with NiV positive and negative controls.

Figure 4. The results of western blot analysis against Nipah virus nucleocapsid protein of seven Ghanaian pig sera (designated P) with high Luminex binding assay titres and one (P17) with a low binding assay titre against soluble henipavirus glycoproteins.

The marker is BenchMark Pre-stained Protein Ladder (Invitrogen); the positive sera NiV virus neutralization test positive pig and human field sera; the negative control sera negative pig and skimmed milk powder (SMP).