Characterization of monoclonal antibodies to the sperm-specific lactate dehydrogenase isozyme

Antibodies to lactate dehydrogenase of Plasmodium knowlesi are specific to Plasmodium species

Polyclonal immune monkey serum raised against schizonts of Plasmodium knowlesi (H-strain) showed the presence of antibodies to lactate dehydrogenase (LDH) of P. knowlesi by immunodot enzyme staining method. The anti-LDH antibodies are most probably directed towards an epitope distinct from the catalytic site as shown by the specific enzyme staining of LDH after binding with antibody on nitrocellulose paper. These antibodies showed reactivity with LDH from different strains (H, P and W1 strains of P. knowlesi) and species (P. cynomolgi B, P. berghei, P. yoelii, P. falciparum and P. vivax) of malarial parasites but did not cross-react with three isoenzymic forms of mammalian LDH (A4, B4 and C4) as well as with LDH from some protozoan and helminth parasites. These findings suggest that the anti-LDH antibodies have defined specificity to Plasmodium spp.

Epitopes of human testis-specific lactate dehydrogenase deduced from a cDNA sequence

The sequence and structure of human testis-specific L-lactate dehydrogenase [LDHC4, LDHX; (L)-lactate: NAD+ oxidoreductase, EC 1.1.1.27] has been derived from analysis of a complementary DNA (cDNA) clone comprising the complete protein coding region of the enzyme. From the deduced amino acid sequence, human LDHC4 is as different from rodent LDHC4 (73% homology) as it is from human LDHA4 (76% homology) and porcine LDHB4 (68% homology). Subunit homologies are consistent with the conclusion that the LDHC gene arose by at least two independent duplication events. Furthermore, the lower degree of homology between mouse and human LDHC4 and the appearance of this isozyme late in evolution suggests a higher rate of mutation in the mammalian LDHC genes than in the LDHA and -B genes. Comparison of exposed amino acid residues of discrete antigenic determinants of mouse and human LDHC4 reveals significant differences. Knowledge of the human LDHC4 sequence will help design human-specific peptides useful in the development of a contraceptive vaccine.

Control of fertilization by immunization with peptide fragments of sperm specific LDH-C4

The use of a well-defined, synthetic antigen is essential to progress in developing a vaccine for fertility control and to establish with certainty the utility of such technology. The studies with LDH-C4 are consistent with the feasibility of using a synthetic antigen in a vaccine to control fertility. LDH-C4 remains the best-developed candidate for future studies. Immunization with LDH-C4 does suppress fertility, and the complete biochemical characterization of this isozyme is well underway. These studies will provide a wealth of synthetic antigens to substitute for the natural product in experiments to determine whether immunologic contraception is appropriate and desirable for wide-scale application in human beings.

Mouse lactate dehydrogenase (LDH) C4 (testis) is immunochemically cross-reactive with LDH A4 (muscle) and LDHB4 (heart)

It has been reported that lactate dehydrogenase (LDH) purified from testes (LDH C) of homotherms is not immunochemically cross-reactive with somatic forms of LDH purified from heart (LDH B) or muscle (LDH A). On the basis of this premise, LDH C has been considered for use as a contraceptive vaccine. Data presented here indicate that mouse antisera to either mouse or rat LDH C are cross-reactive with LDH A and B purified from muscle and heart tissues of mice. However, rabbit antisera to mouse LDH C are not cross-reactive with either mouse LDH A or B. Thus, the degree of cross-reactivity is dependent on the species from which the immunogen LDH is purified, the antisera are derived, and the LDH used in the assay is purified. The determination that LDH A, B, and C are immunochemically cross-reactive is of importance in evaluating LDH C as an immunogen in an immunologic approach to contraception.