Sex-related differences in immunoglobulin M and in total antibody response to hepatitis A virus observed in two epidemics of hepatitis A.

Sixty symptomatic and 42 asymptomatic cases of hepatitis A detected during two epidemics on the Greek island of Crete in autumn-winter, 1978-1979 were tested for serum total and immunoglobulin M (IgM) specific antibody to hepatitis A virus (anti-HAV and IgM anti-HAV) by commercially available solid phase radioimmunoassays. All cases of symptomatic hepatitis A tested during the first eight weeks from onset were IgM anti-HAV positive with a geometric mean titer of 1:3,575 at 0-28 days from onset. The probability of positivity declined progressively thereafter: a 50% level was reached on the 128th day from onset and the geometric mean titer dropped to 1:317 in samples obtained after the 85th day from onset. Asymptomatic patients had a significantly shorter duration of IgM response than symptomatic ones and three months from onset the prevalence of IgM anti-HAV was only 33% in the former compared to 95% in the latter (p less than 0.0001). A significantly higher prevalence of IgM anti-HAV and higher titers of total and IgM specific anti-HAV was observed in females than in males. IgM anti-HAV was positive in 12 (57%) of 21 samples from females compared to three (12.5%) of 24 samples from males, collected after the 85th day from onset (p less than 0.01). Five months from onset, the cumulative probability of IgM anti-HAV positivity in females was 38% compared to 0% in males (p less than 0.05).