**5.2 Vaccine studies**

Could the failure to obtain expected results in antibiotic studies be due to late treatment? Taking measures before inflammatory and immune responses are induced might facilitate the management of the process. Antichlamydial vaccine studies are the focus in this regard.

Due to the different strains and pathogenetic mechanisms in the *Chlamydia* family, vaccines against all chlamydial species have long been a research topic of interest. *C. trachomatis* is the most common sexually transmitted disease in the world and causes health problems of concern to all of humanity in both men and women, from urinary tract infection to infertility, from pneumonia to blindness. Thus, antichlamydial vaccine development started about 100 years ago with *C. trachomatis*. Using the inactivated EB form for immunization provided results, but the short duration of immunity was disappointing [123].

*Chlamydia* contain two main bacteria-specific antigens: HSP-60 and major outer membrane protein (MOMP). MOMP activates both cellular and humoral immunity. Most current antichlamydial vaccine studies are focused on MOMP. HSP-60 is a receptor that can be found in many bacterial species and human cells, and no significant progress has been made to date in vaccine studies targeting this antigen [124].

Li et al. [125] demonstrated that administering a recombinant chlamydial protease-like activity factor (rCPAF) and IL-2 vaccine slowed the atherosclerosis process in their study on mice in which atherosclerosis was induced by a hyperlipidemic diet.

Recombinant protein vaccine studies have also yielded promising results in terms of reducing the immune response occurring after chlamydial contamination [126].

There have been nearly 200 antichlamydial vaccine studies to date, and an average of 10–12 new studies are conducted each year. However, although antichlamydial vaccine studies have investigated numerous specific antigenic targets and achieved partial success in mice, the results from whole-cell vaccine targets have not yet reached the clinical implementation stage [123].

#### **5.3 Treatments targeting inflammation triggers (risk factors)**

There is ample evidence regarding the anti-inflammatory effect of lifestyle modification. Regular exercise have been shown to both directly improve endothelial function and reduce inflammatory mediators, as well as mitigate risk factors [54, 55 83]. Adipose tissue is an important source of IL-6, which is known to be elevated and linked to inflammation in people with obesity. Lipid-lowering diet and treatments are effective in reducing inflammation. Statins not only have a strong lipid-lowering effect, but anti-inflammatory activity is known to be one of their pleiotropic effects. Statins reduce the release of adhesion molecules and inflammatory cytokines. In addition, they correct endothelial function, reduce oxidative stress, inhibit platelet aggregation, prevent clustering of T cell antigen receptors due to immune activation, and generally stabilize vulnerable plaques. The anti-inflammatory effects of statins have been demonstrated in patients with rheumatoid arthritis. In clinical studies, statins have been shown to reduce CRP values independently of LDL levels. In the CARE study, subgroup analyses revealed that the patient group with high CRP levels benefited more from statin treatment, which was more effective in reducing coronary events in this group [127, 128]. In the PROVE-IT study, the greatest benefit was seen in the group with aggressively reduced LDL and decreased CRP, which demonstrated that patients with the most inflammation benefited most and supported the use of statins in acute coronary syndromes [129]. In the JUPITER study, statin therapy resulted in significant reduction of cardiovascular events in individuals with high CRP but without high LDL, offering further evidence of the importance of reducing inflammation [130]. That study included 17,802 healthy individuals with normal LDL-cholesterol level and CRP above 2 mg/l who were randomized to receive rosuvastatin 20 mg or a placebo, and was terminated after only 1.9 years because of the significant reduction in cardiovascular events in the rosuvastatin arm. This rapid benefit was thought to be a result of the anti-inflammatory effect of rosuvastatin rather than its lipid-lowering effect [131].

There are studies on treatment methods that target risk factors, as well as treatments that directly target inflammation [73]. Some evidence has indicated that acetyl salicylic acid also has an important anti-inflammatory effect in addition to its inhibition of platelet aggregation [73].

An emerging treatment method that is still mostly in the animal testing phase is cytokine blockade. The newly identified CD40 pathway has been shown to play an important role in inflammation, the increase in adhesion molecules, and thrombosis. Blockade of this pathway with monoclonal antibodies has allowed a reduction in the development of atherosclerotic lesions in animal experiments [132].

Another treatment method based on cytokine blockade is polyclonal IgG injection. With polyclonal IgG injections, it is possible to block receptors in phagocytic cells and inhibit antibody synthesis and cytokine production. In mouse studies, intravenous IgG injection prevented the development of fatty streaks at several sites and reduced the area of atheromatous plaques [133]. The latest method of cytokine blockade are treatments to shrink atheromatous plaques with IL-10 injection, but these are still in the animal trial stage [134].

Anti-atherosclerosis vaccine development studies have intensified in recent years. The basic principle here is to modulate the immune response and protect against the development of atherosclerosis. For example, developing antibodies against oxidized LDL and creating antibodies by activating B lymphocytes have been shown to have a protective effect against atherosclerosis. In brief, inflammation is a fundamental

mechanism that is present at every stage of atherosclerosis and must be suppressed. The anti-inflammatory effects of lifestyle modification, statin therapy, and some other treatments have been demonstrated, while the search for new anti-inflammatory therapies continues.
