J. C. Booth

Coxsackie B Viruses and Human Heart Disease

A large number of viruses can cause infections of the heart. Among these are the enteroviruses, adenoviruses, retroviruses and even orthomyxoviruses (Clements 1993). Human viruses causing systemic infections have a viremic stage during which the heart may be exposed to infectious agents. Thus the presence of virus in the myocytes or the infiltrating immune cells is likely to be a more common event than suspected. However, clinically overt cases of heart disease following common viral infections are rare and may represent a small percentage of all viral heart infections. Of the numerous agents commonly infecting humans, enteroviruses and in particular coxsackie B viruses (CVB) have been the most closely scrutinised agents implicated in human heart disease. The aim of this review is to discuss the evidence for an etiologic link between enteroviruses and in particular CVB and human heart disease.

COXSACKIE B VIRUS INFECTIONS AND MYOCARDIAL INFARCTION

During an eight-month study, acute serum samples were obtained from all 228 patients admitted with chest pain to a coronary-care unit. On admission a history of a recent influenza-like illness was given by the same proportion (5%) of those subsequently shown to have myocardial infarction, angina, or miscellaneous diagnoses. Myocardial infarction was diagnosed in 105 patients and serum samples were obtained from all of the 93 survivors during convalescence. Sera were also obtained from 99 age and sex matched controls from the same geographical area. Sera from the cases and controls were tested for Coxsackie B antibodies by microneutralisation. In 3 patients with MI and 2 controls significant increases in antibody titre occurred which indicated recent infection. The distribution of type-specific antibodies, geometric mean titres, seropositivity rates, and the prevalence of raised antibody titres were all identical in the cases and the controls. These results do not accord with observations in uncontrolled series which suggested a causal relation between infections with Coxsackie B viruses and myocardial infarction.

Reactivity and assay restriction profiles of monoclonal and polyclonal antibodies to acid phosphatases: a preliminary study

The development of secure diagnostic immunoassays requires, among others, rigorous characterisation of potential antibody reagents. The reactivity profiles of seven antibodies (six monoclonal [MAb] and one polyclonal [PAb]) with putative specificity for tartrate-resistant acid phosphatase (TRAP) and/or osteoclasts were evaluated in enzyme-linked immunosorbent assay (ELISA) and/or immunocytochemistry. MAbs 2H1, 4E6 and 5Cl demonstrated assay restriction: exhibiting reactivity only in ELISA. The remaining three MAbs (G211D, G312G and V35B) and the PAb 8023 recognised recombinant TRAP (rTRAP) in ELISA and native acid phosphatases in selected tissues and cell lines. The latter were cytochemically assessed for both tartrate-sensitive acid phosphatase (TSAP) and TRAP. V35B showed reactivity against the monocytic leukaemia cell line U937 and guinea pig kidney tissue (both TSAP+ and TRAP+) and ECV304 (TSAP+) cells. Interestingly, the reactivity of MAb G211D co-localised with TRAP activity in the membrane of osteoclasts but also detected cytoplasmic components in U937 cells and human embryonic lung fibroblasts (TRAP+ and TRAP+). G211D exhibited immunoreactivity against placental trophoblasts (positive for total AP). Intriguingly, MAbs 2H1, 4E6, 5Cl and PAb 8023 cross-reacted with potato acid phosphatase in ELISA, suggesting reactivity to conformationally similar epitopes. Thus, some of these reagents could be used in the development of standardised diagnostic immunoassays or as drug-targeting agents for conditions in which the pathological process involves bone resorption, the MAbs G211D, 2H1, 4E6, 5Cl and PAb 8023 being useful in ELISA but not immunocytochemical detection of TRAP.

Human cytomegalovirus and acute rejection after heart transplantation are not directly associated

Retrospective and prospective analyses of heart transplant recipients showed no significant association between acute rejection and the detection of cytomegalovirus (CMV) infection by culture or the polymerase chain reaction (PCR) for viral DNA, neither on grounds of the incidence of both conditions nor in relation to which was diagnosed first in the patient. Semiquantitative PCR of serial blood and endomyocardial biopsy specimens from individual patients revealed different patterns in the development of the viral DNA in the blood and the heart, also clear episodes of CMV infection in CMV antibody‐negative recipients of hearts from CMV antibody‐negative donors, none of whom went on to develop a CMV‐specific antibody response. None of these findings was associated with the development of rejection in the patient. On the other hand, in those patients who did experience rejection, peak levels of CMV DNA in the blood and the heart were usually not reached until 6 weeks or more after transplantation, whereas in those in whom rejection was not detected at all during the period of observation, peak levels of CMV DNA were detected earlier, mainly within the first 6 weeks after transplantation. In several cases, the delayed increase in CMV DNA in those with rejection, albeit not the delay itself, was linked to treatment with steroids. These findings support the view that CMV infection and rejection are independent events, but that the timing of the infection, and whether or not rejection is detected, are indicative of the general status of the immune response in individual patients.

Coxsackie B virus-specific IgM antibody and myocardial infarction

The ELISA technique was shown to be group-specific for the detection of IgM antibodies against coxsackie B viruses, and probably against a wider range of enteroviruses. No evidence was obtained that recent coxsackie B-virus infection predisposes to myocardial infarction.

INDIRECT ENZYME-LINKED IMMUNOSORBENT ASSAY (ELISA) FOR DETECTION OF IgG ANTIBODIES AGAINST COXSACKIE B VIRUSES

In tests for IgG antibodies against Coxsackie B viruses in man, the enzyme-linked immunosorbent assay (ELISA) was essentially group-specific and, unlike the type-specific neutralisation test, usually failed to detect rises in antibody titre in paired, acute and convalescent, sera. However, in rabbits immunised against Coxsackie B viruses, ELISA demonstrated both group- and type-specific antibody responses. The lack of type-specificity of ELISA in man is probably because repeated infection with enteroviruses--echoviruses and Coxsackie A as well as Coxsackie B--results in masking of the type-specific antibody response by group-specific antibody.

Is routine post-operative surveillance for cytomegalovirus infection following heart transplantation necessary?

OBJECTIVE Cytomegalovirus infection (CMV) is an important cause of morbidity and mortality following cardiac transplantation. The purpose of the present study was to ascertain whether routine post-operative screening for CMV infection influenced clinical management. METHODS Laboratory and case notes of 220 patients who received cardiac transplantation between November 1986 and October 1996 were reviewed. The range of follow-up was one to 120 (median 36) months. CMV surveillance involved blood tests for early antigen detection weekly for the first 6 post-operative weeks, fortnightly thereafter until the end of the third post-operative month and every 6 weeks to the end of the first post-operative year. Otherwise monitoring was performed if the patients had clinical symptoms suggestive of CMV infection. CMV sero-negative IgG recipients (R) of sero-positive IgG donor (D) organs and/or blood products received hyper-immune gammaglobulin for the first three post-operative months. Four patient groups were noted, namely R+D+ (59 patients), R+D- (70 patients), R-D+ (35 patients) and R-D- (56 patients). RESULTS CMV antigenaemia was present in 40% (89) of patients and 48% (43) of these patients developed clinical features of CMV infection and received ganciclovir therapy. The distribution of clinical CMV infection requiring treatment was 25% (9/35) in the R+D- group, 50% (16/32) in the R+D+ group and 85% (18/22) in the R-D+ group. None of the patients in the R-D- group developed CMV antigenaemia. Forty six (52%) patients who were CMV antigen positive but who did not develop symptoms were not treated with ganciclovir and have remained well. CONCLUSION Our results suggest that routine screening for CMV following cardiac transplantation is unnecessary. Surveillance did not result in the instigation of treatment for CMV unless there were associated clinical features of CMV infection.

Lymphocyte responses to human cytomegalovirus in different groups of patients in Britain and in adults from West Africa and the Middle East

Antibody prevalence and lymphocyte proliferation responses to cytomegalovirus (CMV) and herpes simplex virus (HSV) were compared in several different groups of patients: genitourinary medical (GUM) patients, hemophiliacs, men with clinical acquired immunodeficiency syndrome (AIDS) and cases of primary CMV mononucleosis, and also in adults in the general population (control subjects) comprising separate groups native to Britain, West Africa, and the Middle East. Among the British control subjects who were positive for CMV IgG, all were also positive against CMV antigen by the lymphocyte transformation test (LTT). However, among those who were CMV IgG‐positive in the various groups of patients, 20–86.9% gave positive responses to CMV antigen by the LTT; moreover, 75.7% and 55.5% of the CMV IgG‐positive healthy control subjects from West Africa and the Middle East, respectively, gave positive LTT responses to CMV antigen. When the same groups of patients were tested for responsiveness to HSV antigen by the LTT, there was good agreement between a positive result by this test and by serology in all except those with primary CMV mononucleosis (42.8%). Overall, lymphocyte responses to CMV were significantly impaired in healthy, CMV antibody‐positive subjects from West Africa and the Middle East compared to similar subjects from Britain.