Kemal Karaca

Recombinant canarypoxvirus vaccine carrying the prM/E genes of West Nile virus protects horses against a West Nile virus-mosquito challenge.

An ALVAC (canarypoxvirus)-based recombinant (vCP2017) expressing the prM and E genes derived from a 1999 New York isolate of West Nile virus (WNV) was constructed and assessed for its protective efficacy in horses in two different experiments. In the first trial, a dose titration study was conducted to evaluate both serum neutralising antibody responses to WNV and duration of immunity. In the second trial the onset of protection was determined. Twenty-eight adult horses received two doses of vCP2017 administered intramuscularly at 5-week intervals and sixteen horses comprised age-matched non-vaccinated controls. Individual sera were taken periodically and tested for neutralising antibodies against WNV. Horses were challenged by allowing WNV-infected Aedes albopictus mosquitoes to feed on them two weeks (second trial) or one year (first trial) after the second vaccination. After challenge, horses were monitored for clinical signs of disease, and blood samples were collected for detection of WNV viremia and antibody. In both trials, all vaccinated horses developed neutralising antibodies against WNV. None of the vaccinated or control horses developed clinical signs of WNV disease upon challenge. None of the nine horses challenged 2 weeks after primary vaccination and only one of the ten vaccinated horses challenged 1 year after vaccination developed detectable viremia after challenge, whereas more than 80% of the controls became infected. Results from these studies demonstrated that a primary course of two doses of vCP2017 provides both antibody response and an early immunity in horses against WNV viremia.

Development and Use of Fowlpox Vectored Vaccines for Avian Influenza

Abstract:  The avian influenza (AI) vaccine designated TROVAC™‐AIV H5 (TROVAC‐H5) contains a live recombinant fowlpox rec. (FP) recombinant (recFP), expressing the hemagglutinin (HA) gene of an AI H5 subtype isolate. This recombinant vaccine was granted a license in the United States for emergency use in 1998 and full registration in Mexico, Guatemala, and El Salvador where over 2 billion doses have been administered. One injection of TROVAC‐H5 protects chickens against AI‐induced mortality and morbidity for at least 20 weeks, and significantly decreases shedding after challenge with a wide panel of H5‐subtype AI strains, regardless of neuraminidase subtype. Recently, excellent protection was demonstrated against 2003 and 2004 Asian highly pathogenic H5N1 isolates. Whereas TROVAC‐H5 AI H5 efficacy was not inhibited by anti‐AI or anti‐fowlpox maternal antibodies (passive immunity), protection to AI was significantly decreased in chickens previously vaccinated or infected with FP (active immunity). Advantages of the TROVAC‐H5 vaccine over inactivated AI vaccines are: (a) single administration at 1 day of age and early onset (1 week) of protection, (b) easy monitoring of AI infection in vaccinated flocks with agar gel precipitation (AGP) and enzyme‐linked immunosorbent assay (ELISA) used as tests to differentiate infected from vaccinated animals (DIVA tests), and (c) no residue problem due to adjuvant. These features make TROVAC‐H5 an ideal AI vaccine for routine administration of day‐of‐age chicks in hatcheries. RecFP expressing HA from three lineages of H7 subtype (Eurasian, American, and Australian) were also tested for efficacy against a highly pathogenic avian influenza (HPAI) Eurasian HPAI H7N1. Only the recFP expressing the Eurasian H7 gene provided sufficient protection indicating that the breadth of protection induced by recFP is apparently restricted for H7 isolates. The fowlpox vector technology can also be used for the production of an emergency vaccine: once the HA sequence of an emerging AI virus is known, recFP can be rapidly generated. TROVAC‐H5 has recently been shown to be immunogenic in cats and could therefore also be considered for use in mammals.

Immunogenicity of Fowlpox Virus Expressing the Avian Influenza Virus H5 Gene (TROVAC AIV-H5) in Cats

ABSTRACT Vaccination of cats with fowlpox virus expressing the avian influenza (AI) virus H5 hemagglutinin gene (TROVAC AI) resulted in detectable hemagglutination inhibition (HI) antibody responses to the homologous A/Turkey/Ireland/1378/83 (H5N8) (A/tky/Ire/83) AI virus antigen. The HI antibody responses to heterologous A/Chicken/Indonesia/7/03 (H5N1) (A/ck/Indonesia/03) AI virus antigen were also detected in all vaccinated cats, but only after booster vaccinations. The vaccine described in this study and other poxvirus-vectored vaccines may be of value for the prophylaxis of AI virus-associated morbidity and mortality in mammals.