Study On A Lethal Viral Pathogen Of Common Cotton-eared Marmoset And Its Relationship With Human

As a close consanguinity of human race, the common cotton-eared marmoset (Callithrix Jacchus) has been used in a wide range of research as a primate mode] of human pathology, physiology, biochemistry and nutriology, etc. Their small size and adaptability make it possible for relatively large population to be maintained for experimental purposes. The Experimental Animal Center of Tianjin Medical University has fetched in the common cotton-eared marmosets from Australia in 1987, and now holds more than 100 marmosets. This colony is the biggest one in China.Acute respiratory infection (ARI) broke out in the colony in June, 1999. Almost all the marmosets got ill, and about 1/3 died. The fact that the infection spread out quickly immediately after the outbreak with a high incidence of the disease and a relatively high mortality rate shows distinct characteristics of respiratory virus infection. In order to protect and develop the only marmosets-colony center in P.R.China and find the relationship between the pathogen and human being, a meticulous study on the lethal pathogenicity was carried out.Part one is mainly about isolation & determination of the pathogen-causing ARI.A virus strain with high hemagglutinin liter was isolated out from embryonated egg and MDCK cells after they were inoculated with the lung tissues of the died marmosets. The hemagglutination inhibition (HI) test of paried serum samples and the animal inoculation tests show that: (1). The antibody liter in recovery period have more than 4-fold rise. (2). Symptoms of ARI manifested in the marmoset inoculated with the isolated virus strain are quite similar to that in the epidemic. Theserum antibody liter four weeks after the inoculation has 60-fold rise compared with that before inoculation. (3). Same virus was isolated from SPF mice inoculated with the virus strain. All these confirm that the isolated virus strain is the pathogen of the ARIIt is also found that all the faculty in the animal center have antibody specific to this virus, and 14 of 40 people who had never contacted with the marmosets have antibody to the virus. The result suggests that the virus has a close relation to human, and may be a common respiratory virus in human and marmoset.Part two is about the identification of the isolated virus strain.The cross HI test has been carried out to identify the isolated strain using 6 different sera & virus. It is found that the isolated virus strain is similar to Sendai virus in serology, and with cross reaction to influenza B though.After concentration, the virus was negatively stained and then observed under electron microscope. The structure of nucleocapsid can be observed easily, with the typical character of paramyxoviridae virus.RT-PCR technique was used to detect the genome of the agent. Out of 8 pairs of PCR primers for the possible respiratory viruses, only the primers for sendai virus can amplify product. The product was sequenced and then compared with known sequence in DNA database. BLAST analyses shows the strain is sendai virus, which belongs to parainfluenza virus type 1.Part three is the study on the relationship between the isolated pathogen and human, the virus HN gene clone, which can provide theoretic framework for developing an effective vaccine.The antibody liter of 53 sera from subjects under 14 years, 36 sera from between 15 and 50 years, 43 sera from older than 50 years in Tianjin, and 18 sera from ones in Shanxi-province were examined with HI test. The positive rates have no significantly statistical difference in these groups. About 50% of them have the antibody to the isolated virus strain.The HN gene of the isolated virus was amplified by RT-PCR, and cloned into aplasmid vector, and then sequenced. The deduced protein sequence was compared with the HN protein of human parainfluenza virus type l(hPIVl). These two proteins are very similar in composition, so it is promising that the HN gene of the isolated virus can be candidate for a vaccine against both sendai virus and hPI...