F. W. A. Heessen

Antibody isotype response after human cytomegalovirus infection

The antibody isotype response to human cytomegalovirus (CMV) was studied in paired sera from patients with primary and recurrent CMV infection. The majority of sera was obtained from immunocompromised patients. In the 48 patients with primary CMV infection, CMV-specific IgM (CMV-IgM) and IgG (CMV-IgG) antibodies were found in all patients, and CMV-specific IgA (CMV-IgA) and IgE (CMV-IgE) antibodies in 46 patients. CMV-IgM, -IgA, and -IgE antibodies were found in, respectively, 21, 31 and 4 of the 53 patients with recurrent CMV infection, and in, respectively, 3, 3 and 1 of the healthy controls. The results indicate that CMV-IgE is a better marker of primary CMV infection than CMV-IgM, and confirm that detection of CMV-IgM and -IgA may also be useful for diagnosis of recurrent CMV infection.

Antibody-capture enzyme-linked immunosorbent assays that use enzyme-labelled antigen for detection of virus-specific immunoglobulin M, A and G in patients with varicella or herpes zoster

Antibody-capture enzyme-linked immunosorbent assays (AC-ELISA) which use enzyme-labelled antigen were developed for detection of varicella-zoster virus-(VZV) specific IgM, IgA and IgG antibody in patients with varicella or herpes zoster and in sera from healthy individuals. All 18 patients with varicella developed a VZV-IgM and a VZV-IgG response, 17 also a VZV-IgA response. In contrast, all 19 patients with herpes zoster were shown to be positive for VZV-IgA whereas only 13 of these reacted positively for VZV-IgM. A VZV-IgM response was detected in only two sera from 100 healthy individuals and an IgA response in only one. The presence of virus-specific IgA and IgG in the cerebrospinal fluid as determined by AC-ELISA was a useful indicator of VZV infection of the central nervous system. By AC-ELISA, VZV-IgG was detected predominantly in sera from patients with acute or recent VZV infection. Only 14 sera from 100 healthy individuals were positive for VZV-IgG by AC-ELISA, whereas all were positive by an indirect ELISA. These results indicate that AC-ELISAs may be useful assays for determination for acute or recurrent VZV infection, but are not suitable for determination of past infection with this virus.

Polyclonal B lymphocyte activation induced by mouse hepatitis virus A59 infection

Mouse hepatitis viruses (MHV) diversely affect immune responses, depending on the viral strain and the mouse genetic background. Here, we studied the effect of MHV-A59 infection on B cell responses of 129/Sv and CBA mice. Our results indicate that in these strains, MHV-A59 induces spleen cell activation that leads to enlargement of the spleen without structural alteration. Infection triggers production by B lymphocytes of large amounts of immunoglobulin G2a, mostly without viral specificity. This polyclonal immunoglobulin production is dependent on the presence of functional T helper cells. This polyclonal B lymphocyte activation induced by MHV-A59 infection can have pathological implications, such as the enhancement of concomitant autoimmune reactions.

Use of the enzyme-linked immunosorbent assay for the early diagnosis ofMycoplasma pneumoniae infection

IgM and IgG antibodies toMycoplasma pneumoniae were measured in 147 sera from four groups of patients by means of an indirect enzyme-linked immunosorbent assay (ELISA) and the results compared with those obtained by other methods. A good correlation was demonstrated between the complement fixation test and ELISA-IgM and to a lesser extent ELISA-IgG; for the metabolic inhibition test the reverse was the case. The indirect haemagglutination test appeared to detect mainly IgM antibodies. Low levels of IgM antibodies were dectected by ELISA in 60 sera of children not suffering from pneumonia. However, if only high titres (> 800) were regarded as indicative ofMycoplasma pneumoniae infection, a presumptive diagnosis could have been made in 42 of 73 single acute phase sera from patients. Comparable results were obtained with IHA. The diagnostic level of IgM antibodies was reached during the second week of the disease. It is concluded that examination of a single serum sample by either ELISA-IgM or IHA may assist in early diagnosis ofMycoplasma pneumoniae infection.

Rheumatoid factor production and polyclonal non-antiviral antibody responses elicited by infection with common mouse viruses.

Rheumatoid factor (RF) production and antibody responses directed against antigens unrelated to infectious agents were measured in the serum of 129/Sv mice infected with various viruses. Some of these viruses induced a polyclonal B lymphocyte activation reflected by the presence of serum antibodies reacting in ELISA with dinitrophenylated albumin and with transferrin, but failed significantly to trigger the production of RF capable of agglutinating IgG2a-coated latex particles. In contrast, high RF serum levels were detected only in mice infected with an intestinal agent which was not able to induce other non-antiviral antibody responses. This observation indicates that the strong RF production previously reported in 129/Sv mice is a phenomenon specifically elicited by infection with this particular intestinal agent that cannot be explained by mere polyclonal B lymphocyte activation similar to that induced by common viruses.