Autoantibodies, immunoglobulins, complement and circulating immune complexes in acute malaria.

BACKGROUND: Malaria caused by Plasmodium vivax and Plasmodium falciparum is common in the Indian subcontinent. Studies conducted elsewhere have suggested that malarial infection causes intense immunostimulation. We screened patients with malarial infection for autoantibodies and measured the immunoglobulin, circulating immune complex and complement levels to determine the extent of immunological alterations in these patients. METHODS: One hundred adults with acute malarial infection confirmed by examination of the peripheral blood smear and 25 age- and sex-matched controls were studied. An autoantibody screen and serum immunoglobulin complement (C3 and C4) and circulating immune complex levels were measured at the time of admission and 4 weeks after they became afebrile. A direct Coomb's test was also done. RESULTS: Anti-ssDNA, anti-dsDNA and rheumatoid factor were positive at the time of admission in 51, 30 and 38 patients respectively. None of the controls were positive for these autoantibodies except for one who was positive for rheumatoid factor. The IgM, IgG and IgA levels were raised in 16, 25 and 36 patients respectively. Circulating immune complex levels were raised in 32 patients and complement C3 and C4 were low in 8 and 31 patients. Follow up studies at 4 weeks in 19 patients showed that the autoantibodies were negative. However, the immunoglobulin, C4 and circulating immune complex levels remained elevated. Six per cent of patients had a positive direct Coomb's test with reticulocytosis at the time of presentation. CONCLUSION: Acute malarial infection can cause false-positive results for anti-ssDNA, anti-dsDNA and rheumatoid factor and may also cause a rise in the serum immunoglobulin, complement and circulating immune complex levels.

False positive modified Widal test in acute malaria.

The present study reports results of modified Widal test carried out on 96 cases of acute malaria and 25 healthy controls. Out of the 96 patients studied, 30 had complicated P.falciparum (CPF), 36 had uncomplicated P.falciparum (UPF) and 30 had P.vivax (pv) malaria. Modified widal test was done to know the Widal titers due to Igm type of anti-salmonella antibodies, which is considered very specific for diagnosis of recent enteric fever. This test was positive in 14.58% and 10.41% of malaria patients for salmonella 'o' and 'H' titers respectively. On four weeks follow up most of the positive test become negative. Non-specific polyclonal B lymphocyte stimulation due to malaria was postulated to be responsible for this phenomenon.