Hervé R. Moulin from Agroscope Changins-Wädenswil in Switzerland and co-authors from the Swiss Institute of Virology and Immunoprophylaxis (IVI) in Mittelhäusern and the INRA Pharmacology-Toxicology Unit in Toulouse, France, have published a paper investigating the interferon type I response in the organs of chickens infected with the H5N1 sub-type of the highly pathogenic avian influenza (HPAI) virus. Their paper is published in the journal, Veterinary Research.

The researchers report that their study shows high pathogenic H5N1 influenza virus infection of chicken induced high levels of bioactive interferon type I in the lung (4.3 × 10⁵U/mg tissue), plasma (1.1 × 10⁵U/mL) and spleen (9.1 × 10⁵U/mg tissue).

In contrast, they explain, a low pathogenic attenuated H5N1 vaccine strain only induced approximately 24 times less IFN in the lung, 441 times less in the spleen and 649 less in the plasma. This was in the same range as a reassortant carrying the HA from the vaccine strain and the remaining genes from the high pathogenic virus.

On the other hand, a reassortant virus with the HA from the high pathogenic H5N1 with the remaining genes from the vaccine strain had intermediate levels of IFN.

The level of interferon responses related to the viral load, and those in the spleen and blood to the spread of virus to lymphoid tissue, as well as disease severity. In vitro, the viruses did not induce interferon in chicken embryonic fibroblasts, but high levels in splenocytes, with no clear relationship to pathogenicity and virulence.

This, and the responses also with inactivated viruses imply the presence of plasmacytoid dendritic cell-like leukocytes within the chicken immune system, are possibly responsible for the high interferon responses during H5N1 infection.

Moulin and co-authors add that their data also indicate that the viral load as well as the cleavability of the HA enabling systemic spread of the virus are two major factors controlling systemic IFN responses in chicken.

Reference

Moulin H.R., M. Liniger, S. Python, L. Guzylack-Piriou, M. Ocaña-Macchi, N. Ruggli and A. Summerfield. 2011. High interferon type I responses in the lung, plasma and spleen during highly pathogenic H5N1 infection of chicken. Veterinary Research, 42:6. doi:10.1186/1297-9716-42-6

Further Reading

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You can view the full report (as a provisional PDF) by clicking here.

Further Reading

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You can visit the Avian Flu page by clicking here.

January 2011