Search

A 'blind' recombinant immunoscreening approach, of general application to studies of infectious diseases, was used to clone and identify the genome of the previously uncharacterized non-A, non-B hepatitis (NANB) virus. This agent is a positive-stranded RNA virus that appears to be distantly related to the flaviviridae family. A recombinant viral antigen (C100-3) was used to develop a capture assay for circulating antibody. Data obtained using this assay indicate that this agent, termed the hepatitis C virus (HCV), is the major cause of post-transfusion, community-acquired and cryptogenic, NANB. Anti-C100-3 antibody appears to be directed towards dominant, non-structural viral epitopes. It is a non-neutralising antibody that develops generally late in infection and is a particularly good marker of chronic, persistent viraemia. Many asymptomatic but infectious blood donors can now be detected using this antibody assay. HCV is associated with the development of hepatocellular carcinoma and possibly, other liver diseases.

A three-step solid-phase radioimmunoassay, HAVAB-M, was developed for use in clinical labs as an aid to diagnosing hepatitis A. Polystyrene beads were coated with anti-human IgM (mu-chain specific) and were incubated successively with serum specimen, HAV, and anti-HAV 125I. HAVAB-M was used to assay sera from patients with hepatitis A and was found to have high sensitivity for the IgM antibody to HAV. The antibody was detectable within a few days of onset of symptoms of hepatitis, and it reached maximum concentrations within one to three weeks. The test was designed so that most patients' sera would become negative approximately three months after onset. HAVAB-M was shown to be specific for IgM antibody, with virtually no detection of IgG anti-HAV. The test showed no interference fro rheumatoid factor and no cross-reactivity with sera from patients with hepatitis B or other infectious diseases.

Serial serum specimens from 149 patients with clinically diagnosed hepatitis were tested for five hepatitis B serological markers: hepatitis B surface antigen and its antibody (anti-HBs); hepatitis B e-antigen and its antibody (anti-HBe); and antibody to hepatitis B core antigen (anti-HBc). The times of appearance, disappearance, and persistence of these markers were used to differentiate various serological profiles obtained from the study. Four distinctive profiles were found to be associated with acute hepatitis B followed by recovery, and three with chronic hepatitis. These serologic profiles were assessed as diagnostic and prognostic guides for clinical management of the disease.

In 1968, studies of infectious hepatitis in volunteers were reported. Immunologic procedures for serologic study of the hepatitis A virus were not available at that time, and only the clinical and biochemical parameters of the disease were reported. Serial serum specimens from the participants in the study were retained; these specimens had been taken before inoculation and up to more than 100 days after inoculation. When a radioimmune assay for antibody to hepatitis A virus was developed, the series of sera was analyzed retrospectively. Forty-four male volunteers were involved in a series of three studies. Twenty (46%) of the volunteers were found to be initially immune to hepatitis A virus. Eighteen susceptible volunteers (with no preexisting antibody) were challenged with infectious virus. Eight of these volunteers developed clinical hepatitis and seroconverted; one seroconverted without evidence of clinical disease; and nine neither seroconverted nor had evidence of clinical disease. The radioimmune assay provided a method for diagnosis of immune status and of the acute disease caused by hepatitis A virus.

The performance of a solid phase radioimmunoassay (ABBOTT-HBe) for the detection of hepatitis B e antigen (HBeAg) and its antibody anti-HBe was evaluated in clinical studies. The reagents and procedure were found to be reproducible by seven investigators, and lab-to-lab variations were minimal. In HBsAg positive sera, ABBOTT-HBe detected HBeAg or anti-HBe in 90% of the specimens compared to 50% tested by immunodiffusion. During the early acute stage of viral infection, serum HBeAg coincided with the rise and decline of HBsAg and seroconversion to anti-HBe occurred most often prior to loss of HBsAg. Patients with clinical evidence of chronic liver disease showed persistence of HBsAg and HBeAg. Vertical transmission studies of hepatitis B virus infection from mother to newborns, showed that mothers whose sera were positive for both HBsAg and HBeAg resulted in a greater incidence of transmission of hepatitis B virus to their offspring than mothers whose sera were HBsAg positive but HBeAg negative.