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Activity and physical appearance were assigned scores from 0 = normal to 3 = severe and graphed to compare between groups. were still detected three weeks post-hatch. Three weeks post-hatch, chickens were challenged with 106 EID50/bird of Mexican-origin H7N3 HPAIV. Interestingly, while 0% of the MDA (?) chickens survived the challenge, 95% of the MDA (+) chickens survived. Furthermore, computer virus shedding was significantly reduced by day 5 post-challenge in the MDA (+) group. In conclusion, MDA confers partial protection against mortality upon challenge with H7N3 HPAIV, as far as three weeks post-hatch, even in the absence of detectable Alosetron Hydrochloride anti-HA antibodies, and reduce computer virus shedding after challenge. Keywords: maternally-derived antibodies, highly pathogenic avian influenza computer virus, H7N3, vaccination of chickens, protection 1. Introduction Influenza A computer virus (IAV) infections of poultry have severe repercussions to the poultry industry. Infections with low pathogenic avian influenza computer virus (LPAIV) are commonly associated with reduced feed conversion rates, weight loss, decreased egg production, and secondary infections. Flocks infected with highly pathogenic avian influenza computer virus (HPAIV) usually show high mortality rates that can decimate an entire flock. Outbreaks of LPAI and HPAI cause important economic losses to the poultry industry due to expenses associated with culling and quarantine, emergency vaccination programs, and loss of consumer confidence, among other issues. Undoubtedly, the most important LPAIVs are of the H5 and H7 subtypes because of their potential to mutate into HPAIVs. Outbreaks in poultry caused by H5 and H7 subtype LPAIV and HPAIV strains are reportable to the World Animal Health Business [1]. Alosetron Hydrochloride In the Americas, highly-pathogenic avian H7N3 viruses have been previously reported in Chile (2002) and Canada (2004 and 2007) [2,3,4]. In 2012, an H7N3 HPAIV was first reported in Mexico and became endemic with devastating consequences for the commercial poultry sector. Between June and August of 2012, 22.3 million chickens were culled [5,6]. Since then, Mexico has introduced intensive vaccination campaigns to control outbreaks occurring in different regions of the country [5], with only partial success as shown by continuing Alosetron Hydrochloride reports to the OIE [6]. H7N3 viruses isolated from Mexico have been further analyzed for protection in chickens and for their fitness in chickens and mallards. Variations in protection and fitness have been found between viruses isolated from different years as shown in recent reports [7,8]. Vaccination of poultry against influenza stimulates production of antibodies that confer variable protection against field strains. These antibodies can be vertically transferred from mothers to the hatching progeny and, therefore, are referred to as maternally-derived antibodies (MDA). The passive transfer of maternal immunity was initially described in chickens by Klemperer in 1893 (reviewed in [9]). There are three types of immunoglobulins identified in chickens: IgY (functional equivalent KSHV ORF45 antibody of the mammalian IgG), IgA, and IgM [10,11,12]. Serum IgY is usually transported from the hens blood stream into the oocyte (which becomes the egg yolk) while still in the ovarian follicle through a specific receptor that recognizes the Fc domain name [13,14,15,16,17]. The IgA and IgM are secreted by the mucosa of the oviduct and incorporated in low amounts into the egg along with the secreted albumin during egg formation [18]. During embryo development, the IgY is usually transported from the egg yolk into the embryos systemic circulation through receptor-mediated transcytosis [19,20,21,22]. This transport has been documented Alosetron Hydrochloride as early as seven days into incubation [23] and increases over time, peaking towards last couple of days before hatch and within the first few days after hatch [24]. The IgA and IgM are ingested by the embryo from the amniotic fluid and transported to the gut in very low amounts [15,18]. Several studies have been conducted to evaluate the half-life.