雞傳染性鼻炎菌(Avibacterium paragallinarum)為引起雞隻傳染性可利查病(Infecious coryza, IC)，發病的雞隻常可見眼窩下竇腫脹，若是感染產蛋雞可造產蛋率下降，造成經濟損失。雞傳染性鼻炎菌為格蘭氏陰性菌，因此有許多的致病因子與細胞壁成分有所相關，其中脂多醣可經由相位改變(phase variation)改變，使得醣類的結構及抗原性發生變異，進而影響疫苗保護力。經由序列比對結果發現，雞傳染性鼻炎菌具有兩段重複序列，並且與脂多醣的生合成基因有所相關。第一種為losA基因之5’-GAAC-3’重複序列與脂多醣半乳糖的修飾相關，第二種為rfaF基因之5’-GCCA-3’重複序列與脂多醣的七碳醣修飾相關，經上述重複序列可由細菌增殖複製時，slipped strand mispairing (SSM)可改變細菌基因中重複序列的數目，進一步去影響調控醣類的修飾與否。以PCR分析的方式發現losA及rfaF基因的重複序列在不同雞傳染性可利查菌之分離株中皆有所不同，且此兩基因之表現與否會影響細菌之脂多醣結構。本研究也利用基因選殖方式成功表現了此兩段重複序列基因蛋白，也成功免疫雞隻並產生出重組蛋白之抗體，這些抗體可用來檢測losA與rfaF基因之表現與否。這是首次發現雞傳染性鼻炎菌經由重複序列基因來改變脂多醣體中之醣類成份。 Avibacterium paragallinarum is the causative agent of infectious coryza, an important respiratory disease associated with growth retardation and reduced egg production in chickens. Avibacterium paragallinarum is a gram-negative coccobacillus that possesses a variety of virulence factors, mostly associated with cell wall composition, and one of the factors is glycosylation. Expression of glycosylation enhances bacterial susceptibility to the complement-mediated killing by normal chicken serum. Genome sequencing analysis showed that Av. paragallinarum contained an operon with strong sequence similarity to the losA and rfaF operon from Haemophilus influenzae, in which losA and rfaF controls the phase variable decoration of LPS with glycosylation. The gene losA contained a variable number of tandem repeats (VNTR) of the tetranucleotide unit 5’-GAAC-3’, encode a galactosyltransferase. The rfaF gene contained a VNTR of the tetranucleotide unit 5’-GCCA-3’, encode a heptosyltransferase. Variation in the number of VNTR may occur through slipped strand mispairing (SSM), resulting of shift of the downstream reading frame in or out of frame with the start codons. PCR analyses showed that the losA and rfaF gene contain different numbers of VNTR in Av. paragallinarum. Moreover, the structure of LPS of Av. paragallinarum was changes by the ON/OFF expression of losA and rfaF genes. The anti-losA and anti-rfaF sera were prepared from chicken that were immunized with recombinant losA and rfaF. These sera may be used to detect the losA and rfaF protein expressed in Av. paragallinarum. This is the first report on the phase-variable regulation of glycosylation of LPS from Av. paragallinarum and the mechanism for control of glycosylation of LPS from in this organism.