Transforming growth factor beta production is inversely correlated with severity of murine malaria infection.

We have examined the role of the immunomodulatory cytokine transforming growth factor (TGF)-beta in the resolution and pathology of malaria in BALB/c mice. Circulating levels of TGF-beta, and production of bioactive TGF-beta by splenocytes, were found to be low in lethal infections with Plasmodium berghei. In contrast, resolving infections with P. chabaudi chabaudi or P. yoelii were accompanied by significant TGF-beta production. A causal association between the failure to produce TGF-beta and the severity of malaria infection was demonstrated by treatment of infected mice with neutralizing antibody to TGF-beta, which exacerbated the virulence of P. berghei and transformed a resolving P. chabaudi chabaudi infection into a lethal infection, but had little effect on the course of P. yoelii infection. Parasitemia increased more rapidly in anti-TGF-beta-treated mice but this did not seem to be the explanation for the increased pathology of infection as peak parasitemias were unchanged. Treatment of P. berghei-infected mice with recombinant TGF-beta (rTGF-beta) slowed the rate of parasite proliferation and prolonged their survival from 15 to up to 35 d. rTGF-beta treatment was accompanied by a significant decrease in serum tumor necrosis factor alpha and an increase in interleukin 10. Finally, we present evidence that differences in TGF-beta responses in different malaria infections are due to intrinsic differences between species of malaria parasites in their ability to induce production of TGF-beta. Thus, TGF-beta seems to induce protective immune responses, leading to slower parasite growth, early in infection, and, subsequently, appears to downregulate pathogenic responses late in infection. This duality of effect makes TGF-beta a prime candidate for a major immunomodulatory cytokine associated with successful control of malaria infection.

An ABC-ELISA for malaria serology in the field.

An avidin biotin peroxidase complex enzyme-linked immunosorbent assay (ABC-ELISA) was examined for the diagnosis of malaria in a controlled area in Sudan Gezira. The titers of the ABC-ELISA coincided with those of the IFAT. The method was more sensitive than the ordinary ELISA as the final enzyme reaction was amplified through the use of the ABC system. This allowed the resulting color spots on the dried plate wells to be read clearly with the naked eye. This test can be carried out without using major electrical equipment.

Maintaining the immunological balance in parasitic infections: a role for TGF-beta?

Transforming growth factor beta (TGF-beta) is an important regulator of inflammation, being proinflammatory at low concentrations and anti-inflammatory at high concentrations. As such, TGF-beta might be important in maintaining the balance between control and clearance of infectious organisms on the one hand and prevention of immune-mediated pathology on the other. In this article, Fakhereldin Omer, Jørgen Kurtzhals and Eleanor Riley review the immunoregulatory properties of TGF-beta in the context of parasitic infections. Data from murine malaria infections suggest that TGF-beta modifies the severity of the disease, and a number of potential protective mechanisms are discussed. Evidence is accumulating that TGF-beta is important for the regulation of other host-parasite interactions and that parasites might directly influence TGF-beta-dependent pathways via the synthesis of TGF-beta or TGF-beta-receptor homologues.

Absolute levels and ratios of proinflammatory and anti-inflammatory cytokine production in vitro predict clinical immunity to Plasmodium falciparum malaria.

The relationship between malaria-related outcomes and cytokine production in whole blood cultures associated with cellular immune responses and immunity to Plasmodium falciparum malaria was examined in a study in southern Ghana. Production of malaria-specific interferon (IFN)-gamma was associated with reduced risk of fever and clinical malaria. Protective IFN-gamma responses were induced by live schizonts but not by dead parasites. Production of malaria-specific tumor necrosis factor (TNF)-alpha was associated with reduced risk of fever during follow-up. Baseline levels of TNF-alpha and phytohemagglutinin (PHA)-induced interleukin (IL)-10 were positively associated with hemoglobin concentration. IL-12 production was associated with reduced risk of parasitemia. PHA-induced transforming growth factor-beta production was associated with reduced risk of fever during follow-up. High ratios of proinflammatory to anti-inflammatory cytokines were associated with increased risk of fever and higher hemoglobin concentrations. Thus, absolute levels and ratios of proinflammatory and anti-inflammatory cytokines influence susceptibility to infection, clinical disease, and anemia. These data contradict data from cross-sectional clinical studies and indicate a need for detailed analysis of the relationship between cellular immunity to malaria and resistance to disease.

Syphilis, gonorrhoea and genital chlamydial infection in a Somali village.

A total of 767 sera were collected from 187 men, 200 women and 380 children in a Somali village, Jambaluul. All sera were tested for syphilis serological markers by Venereal Diseases Research Laboratory (VDRL) and Treponema pallidum Haemagglutination Assay (TPHA). Sera positive for both or either of these tests were further analysed for the presence of specific IgM antibodies by Solid Phase Haemadsorption Assay (SPHA). A high and almost equal prevalence of TPHA positivity was found in men and women; 24% and 22.5%, respectively, and IgM antibodies were found in 3% and 4%, respectively. TPHA positivity significantly increased with age. Thus more than half of the villagers at the age of 45 years or more were TPHA positive. One percent of the children were TPHA positive. From all adults aged 15 years and above urogenital specimens were also taken for Chlamydia trachomatis antigen detection with an enzyme-amplified immunoassay (IDEIA) and Neisseria gonorrhoeae culture. Chlamydial genital infection was found in 6% of the men and 18% of the women. All gonococcal cultures were negative.