Grandien M
Department of Virology, Swedish Institute for Infectious Disease Control, S-105 21 Stockholm, Sweden.
Clin Diagn Virol. 1996 May;5(2-3):81-90. doi: 10.1016/0928-0197(96)00209-7.
Diagnosis of viral infections can be obtained in the early stages of a disease by detection of viral antigens directly in the clinical specimen. This has become an important tool for rapid virus diagnosis.
Antigens produced during virus infections can be detected either in cells collected from the site of infection by immunohistological investigation or in secretions and blood by solid phase immunoassays (IA). Viruses causing acute respiratory infections can be diagnosed in cells from the respiratory tract, viruses causing vesicular eruptions in epithelial cells from skin scrapings, rabies virus in nerve cells of the brain or epithelial cells from skin and cornea and cytomegalovirus (CMV) matrix antigen, pp65, can be detected in peripheral blood leukocytes (PBL) by immunofluorescence (IF) or immunoperoxidase techniques. The quality of specimens can be easily checked during the reading of results. Some IAs for antigen detection, such as detection of HBsAg and HIV p24 antigen in blood are standardized and sensitive. Others give less sensitive results because of the variation of quality of the clinical specimen. The latex agglutination tests are mainly used for rapid detection of virus or viral antigens in faeces: rota-and adenoviruses; the method may not be very sensitive but yields a result within a few minutes. Assays detecting viral nucleic acids are more sensitive than antigen detection tests because of a tremendous amplification of gene segments obtained by the polymerase chain reaction (PCR). So far such assays are time consuming and expensive and are mainly used in specific clinical situations.
After introduction of specific monoclonal antibodies (Mabs), the antigen detection techniques are increasingly used. the need for quality control, trained staff, and standardized reagents and methods for specimen collection and preparation is now being appreciated. IF for viral respiratory viruses is used for diagnosis and epidemiological studies all over the world. Likewise, IF is still the method most often used for rabies diagnosis. For CMV, the pp65 matrix antigen is shown to be a sensitive marker closely correlated with clinical symptoms. Its detection by the IF technique has proven to be superior to other techniques for prediction of CMV pneumonia in bone marrow transplant patients. IAs are currently used in fully automated systems for large scale diagnosis based on antigen detection in serum specimens. Increase of antibody specificity on the solid phase by use of Mabs directed against the most abundant viral antigen in the clinical specimen shortens the reaction time; this has been employed in most of the constantly appearing new rapid diagnosis kits based on the immunoassay principle.
Although, in virology, more sensitive results are obtained by the gene detection method, PCR, directly in clinical samples, viral antigen detection tests are, after the introduction of Mabs for diagnostic purposes, increasingly used because of their low demand on laboratory equipment, their rapid and early result and relatively low cost. Antigen detection is successfully used directly in clinical specimens for rapid diagnosis of many viral infections as well as for identification of tissue culture isolated viruses. With Mab-based IAs the reaction time is shortened and new rapid, almost 'instant test' kits are appearing on the market.
通过直接检测临床标本中的病毒抗原，可在疾病早期获得病毒感染的诊断结果。这已成为快速病毒诊断的一项重要工具。
病毒感染过程中产生的抗原，可通过免疫组织学研究在从感染部位采集的细胞中检测，或通过固相免疫测定法（IA）在分泌物和血液中检测到。引起急性呼吸道感染的病毒可在呼吸道细胞中诊断，引起水疱疹的病毒可在皮肤刮屑的上皮细胞中诊断，狂犬病病毒可在脑神经元细胞或皮肤及角膜的上皮细胞中诊断，巨细胞病毒（CMV）的基质抗原pp65可通过免疫荧光（IF）或免疫过氧化物酶技术在外周血白细胞（PBL）中检测到。在读取结果时可轻松检查标本质量。一些用于抗原检测的免疫测定法，如血液中乙肝表面抗原（HBsAg）和HIV p24抗原的检测，已标准化且灵敏。其他一些免疫测定法由于临床标本质量的差异，结果敏感性较低。乳胶凝集试验主要用于快速检测粪便中的病毒或病毒抗原：轮状病毒和腺病毒；该方法可能不太灵敏，但几分钟内即可得出结果。由于聚合酶链反应（PCR）对基因片段的大量扩增，检测病毒核酸的测定法比抗原检测试验更灵敏。到目前为止，此类测定法耗时且昂贵，主要用于特定临床情况。
引入特异性单克隆抗体（Mab）后，抗原检测技术的应用越来越广泛。现在人们认识到需要进行质量控制、配备训练有素的工作人员以及使用标准化试剂和用于标本采集与制备的方法。用于病毒呼吸道病毒的免疫荧光法在全世界用于诊断和流行病学研究。同样，免疫荧光法仍是狂犬病诊断最常用的方法。对于巨细胞病毒，pp65基质抗原被证明是与临床症状密切相关的敏感标志物。通过免疫荧光技术检测该抗原已被证明在预测骨髓移植患者的巨细胞病毒肺炎方面优于其他技术。免疫测定法目前用于基于血清标本抗原检测的全自动大规模诊断系统。通过使用针对临床标本中最丰富病毒抗原的单克隆抗体提高固相上抗体的特异性，可缩短反应时间；这已应用于大多数不断出现的基于免疫测定原理的新型快速诊断试剂盒中。
尽管在病毒学中，通过基因检测方法即直接在临床样本中进行PCR可获得更灵敏的结果，但出于对实验室设备要求低、结果快速且早期以及成本相对较低等原因，在将单克隆抗体用于诊断目的后，病毒抗原检测试验的应用越来越广泛。抗原检测已成功直接用于临床标本，用于多种病毒感染的快速诊断以及组织培养分离病毒的鉴定。基于单克隆抗体的免疫测定法缩短了反应时间，市场上出现了新型快速、几乎“即时检测”的试剂盒。
