Immunoassays have been used in recent years to detect the presence of infectious diseases. In order for the assay to be useful, it must detect a particular organism with a high degree of reliability. In most cases, this requires the isolation and reaction of antigens peculiar to the organism with corresponding antibodies. For the test to be commercially successful, it also needs to be relatively inexpensive, simple to use and rapid.
One such organism which can be detected by immunoassay is herpes simplex virus. Despite the increasing control of various viruses by vaccination or treatment with various anti-viral agents, infection by herpes simplex virus (identified herein as HSV) remains a serious problem. There are two types of HSV: type 1 which occurs mainly around the mouth, and type 2 which occurs primarily around the genital area of the human body. Skin infections and viral encephalitis are but two of the serious results from HSV infection.
Because of the widespread nature of herpes infection, there is considerable interest in having a rapid, simple and reliable test for detection of the causative virus. However, there are several similar viruses which often are indistinguishable from HSV using known diagnostic procedures. Thus, a useful diagnostic test for HSV-1 or HSV-2 must be specific for these viruses only, and must not be sensitive to viruses such as Epstein-Barr virus, cytomegalovirus, varicella zoster virus or any other flora.
Extraction of antigen from the organisms in a biological specimen is critical to providing an accurate, rapid and sensitive assay. Many varied techniques have been used for extraction including physical disruption of the cells by sonication, heating or centrifugation. Chemical extraction compositions have also been developed. For example, U.S. Pat. No. 4,661,349 (issued Apr. 28, 1987 to Kino et al) describes the extraction and purification of a 90,000-95,000 dalton molecular weight glycoprotein B from HSV in the preparation of a vaccine. Extraction is accomplished using any of a number of nonionic or anionic surfactants at neutral pH.
U.S. Pat. No. 4,430,437 (issued Feb. 7, 1984 to Hampar et al) describes extraction of nucleocapsid proteins from HSV using first a mixture of glycerol, Nonidet P-40 nonionic surfactant, sodium deoxycholate and phenylmethylsulfonylfluoride at pH 8, followed by treatment with sodium dodecyl sulfate, a mercaptoethanol at pH 8 and 100.degree. C. It is to be noted that the low pH and high temperature are important for the described extraction procedure.
Ethanolamine has been used in combination with surfactants and high temperature heating (for example, 70.degree.-110.degree. C.) to extract chlamydial antigens at a pH below 8 as described in E.P. Publication 183,383 (IQ BIO).
There is a need in the art for a means of extracting herpes simplex viral antigen to provide sensitive and rapid assays that can be readily adapted to simple test devices.